Noninvasive Respiratory Metabolite Analysis Associated with Clinical

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Article

Non-invasive respiratory metabolite analysis associated with clinical disease in cetaceans: a Deepwater Horizon oil spill study Alberto Pasamontes, Alexander A Aksenov, Michael Schivo, Teri Rowles, Cynthia R. Smith, Lori H. Schwacke, Randall S. Wells, Laura Yeates, Stephanie Venn-Watson, and Cristina E. Davis Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.6b06482 • Publication Date (Web): 13 Apr 2017 Downloaded from http://pubs.acs.org on April 16, 2017

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Environmental Science & Technology

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Non-invasive respiratory metabolite analysis associated with clinical

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disease in cetaceans: a Deepwater Horizon oil spill study

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Alberto Pasamontes1, Alexander A. Aksenov1, Michael Schivo2,3, Teri Rowles4, Cynthia R. Smith5, Lori

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H. Schwacke6, Randall S. Wells7, Laura Yeates5, Stephanie Venn-Watson5, Cristina E. Davis1,*

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1 Mechanical and Aerospace Engineering, One Shields Avenue, University of California, Davis, CA 95616, USA

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2 Department of Internal Medicine, 4150 V Street, Suite 3400, University of California, Sacramento, CA 95817,

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USA

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3 Center for Comparative Respiratory Biology and Medicine, University of California, Davis, CA 95616, USA

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4 Office of Protected Resources, National Marine Fisheries Service, National Oceanic and Atmospheric

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Administration, 1315 East West Highway, Silver Spring, MD 20910, USA

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5 National Marine Mammal Foundation, 2240 Shelter Island Drive, Suite 200, San Diego, CA 92106, USA

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6 National Centers for Coastal Ocean Science, National Oceanic and Atmospheric Administration, 331 Fort Johnson

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Road, Charleston, SC 29412, USA

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7 Chicago Zoological Society’s Sarasota Dolphin Research Program, c/o Mote Marine Laboratory, 1600 Ken

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Thompson Parkway, Sarasota, Florida 34236, USA

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*Correspondence: Mechanical and Aerospace Engineering, One Shields Avenue, University of California, Davis,

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CA 95616, USA, +1 (530) 754-9004, [email protected]

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ABSTRACT

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Health assessments of wild cetaceans can be challenging due to the difficulty of gaining

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access to conventional diagnostic matrices of blood, serum and others. While the non-invasive

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detection of metabolites in exhaled breath could potentially help to address this problem, there

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exists a knowledge gap regarding associations between known disease states and breath

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metabolite profiles in cetaceans. This technology was applied to the largest marine oil spill in

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U.S. history (The 2010 Deepwater Horizon oil spill in the Gulf of Mexico). An accurate analysis

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was performed to test for associations between the exhaled breath metabolome and sonographic

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lung abnormalities as well as hematological, serum biochemical, and endocrine hormone

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parameters. Importantly, metabolites consistent with chronic inflammation, such as products of

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lung epithelial cellular breakdown and arachidonic acid cascade metabolites were associated

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with sonographic evidence of lung consolidation. Exhaled breath condensate (EBC) metabolite

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profiles also correlated with serum hormone concentrations (cortisol and aldosterone),

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hepatobiliary enzyme levels, white blood cell counts, and iron homeostasis. The correlations

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among breath metabolites and conventional health measures suggest potential application of

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breath sampling for remotely assessing health of wild cetaceans. This methodology may hold

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promise for large cetaceans in the wild for which routine collection of blood and respiratory

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anomalies are not currently feasible.

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Keywords: Breath analysis, metabolomics, non-invasive method, cetaceans

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INTRODUCTION

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Health assessments of common bottlenose dolphins (Tursiops truncatus) via temporary

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capture and release have been valuable for understanding disease in wild populations, as well as

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identifying underlying causes and risk factors for disease. Unfortunately, routine health

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monitoring of cetaceans, especially large species, in their natural habitat can be challenging since

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comprehensive health evaluations require samples, such as blood, urine, or ultrasound images,

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that are difficult or impossible to obtain without physically handling the animal. One potential

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way to address this issue is through the use of exhaled breath analysis for cetacean health

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assessment. Breath analysis metabolomics is a very attractive tool due to the fact that the

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necessary samples can be collected non-invasively and potentially remotely without having to

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physically handle the animal1, 2.

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In order to identify breath-based metabolic profiles that are associated with specific

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disease states in cetaceans, there is a need to pair exhaled breath metabolite data with confirmed

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clinical disease using standard diagnostic tools. Additionally, there is a need to use sophisticated

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state-of-the-art technologies and analytical approaches, such as mass spectrometry3, 4. Deviations

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in breath metabolic content due to any factors such as diseases and exposures can be potentially

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evaluated by comparing against “normal” baseline metabolite profile from healthy animals5 or a

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list of target biomarkers previously identified.

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The Deepwater Horizon (DWH) oil spill began in April 2010 after the explosion of the

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oil rig in the Macondo Prospect6, 7. As part of the DWH Natural Resource Damage Assessment

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(NRDA) a number of studies were conducted to assess the impacts to populations of cetaceans8,

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, including bay, sound and estuary (BSE) common bottlenose dolphins10-12. The studies

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evaluated the health of bottlenose dolphins in two areas of the Northern Gulf of Mexico coast

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that were heavily oiled (Barataria Bay and Mississippi Sound), as well as in a reference site

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(Sarasota Bay, FL) that did not receive oiling from the DWH spill

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dolphins that stranded and died within the oil spill footprint10. These studies have revealed that

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dolphin populations within the oil spill footprint were severely affected by the spill, including


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, as well as evaluation of


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increased presence of adrenal and lung disease, higher mortality and lower survival rates,

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perinatal losses, and poor reproductive success11,

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opportunity to evaluate affected animals and lay the ground work in determining specific breath

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biomarkers associated with health conditions in dolphins affected by the oil spill. The goals of

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the present study were to identify specific 1) breath-based metabolite profiles associated with a

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dolphin population with adverse health effects following an oil spill compared to reference

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populations, and 2) changes in breath metabolites associated with lung disease or clinical blood

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values. By doing so, we aimed to demonstrate how the method of breath analysis could serve as

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a valuable tool in wildlife conservation efforts and deepen our understanding of marine mammal

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biology and physiology.

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. The severe impacts have presented an

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MATERIAL AND METHODS

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Exhaled Breath Condensate (EBC) Sampling.

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An exhaled breath condensate (EBC) collection device was specifically adapted for

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marine mammal anatomy and physiology and was previously described4. Briefly, this device

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consists of a glass tube with dry ice packed around it and a soft mask on the bottom which is

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placed above the blowhole. Exhaled air is expelled through the chilled glass tube out of the

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exhaust to the surrounding air.

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EBC Sample Collection from Wild Dolphins.

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Exhaled breath condensate from wild common bottlenose dolphins was collected during

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capture and release exercises conducted in Sarasota Bay (SB), Florida USA in May 2011 and

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May 2012 as a part of periodic health assessment studies, and in Barataria Bay (BB), Louisiana

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USA during 3-16 August 2011 as part of a DWH NRDA study. The dolphin health assessment

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study in SB was led by the Chicago Zoological Society and conducted under National Marine

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Fisheries Service Scientific Research Permit No. 15543, and the study in BB was led by NOAA

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and conducted under National Marine Fisheries Service Scientific Research Permit No. 932-

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1905/MA-009526. Protocols were reviewed and approved by NOAA Institutional Animal Care

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and Use Committees for Barataria Bay. In total, 21 breath samples were collected from dolphins

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in SB and 19 breath samples were collected from dolphins in Barataria Bay. 4 ACS Paragon Plus Environment

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The catch and release procedure was as follows. The free swimming animals were

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scouted and selected, and then restricted by deploying a seine net. Captured individuals were

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restrained by handlers and, if necessary, disentangled from the net. Following the capture, the

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animals were transferred onto a padded, shaded deck of a special research boat and a several

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biological samples were collected within span of approximately one hour10, including exhaled

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breath condensate. To procure a breath sample, the collection device was positioned above the

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blowhole without immediate contact and 10 full breaths were captured over an approximately 5

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min time frame. Approximately 200-500 µL of EBC were collected each time, depending on the

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size and behavior of the animal during collection. The frozen EBC samples were extruded from

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the sampling device using PTFE plunger, placed into a borosilicate vial, capped and immediately

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placed on dry ice and then in a -80 °C freezer at until further metabolite biochemical analysis.

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For each consecutive collection the device and plunger were thoroughly cleaned with 70%

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ethanol and allowed to air dry.

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EBC Sample Collection from Managed Animals under Human Care.

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EBC sample collection was carried out from 10 managed animals in the U.S. Navy

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Marine Mammal Program in San Diego, CA using previously published methods4. In total, 21

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samples were utilized for analysis, as described below. The collection was conducted on animals

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that breathed normally while positioned by trainers at the water surface. Approximately 10-20

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breaths were collected over a 5 min time frame, depending on the animal size and behavior. The

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samples were normalized by its weight. Typical EBC volumes were up to 500 µL of condensate.

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The frozen EBC samples were extruded from the sampling device with PTFE plunger, placed

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into a borosilicate vial, capped and immediately stored on dry ice and then in a -80 °C freezer

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until further analysis. For each consecutive collection the device and plunger were thoroughly

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cleaned with 70% ethanol and allowed to air dry.

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Liquid Chromatography/Mass Spectrometry (LC/MS) Analysis of Non-volatile EBC

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Metabolites.

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Samples from both wild and managed animals were analyzed using the same analytical

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protocols for metabolomic profiling that have been published in detail earlier4. Briefly, the 0.1 5 ACS Paragon Plus Environment


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mL aliquot of EBC was lyophilized and then redissolved in 0.1 mL of 90% acetonitrile in water.

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Five µL of resuspended sample was then used for LC/MS analysis. The CUDA (12-

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[[(cyclohexylamino)-carbonyl]amino]dodecanoic acid) in methanol/toluene, 9:1 v/v internal

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standard, was added to each sample and used for quality control and to assess reproducibility.

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Analysis was performed on an Agilent 1200 Series high-performance liquid chromatography

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(HPLC)/6530 accurate-mass Q-TOF mass spectrometer system (Agilent Technologies, Santa

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Clara, CA)4 on a Kinetex 2.6 µm (HILIC) 100 Å HPLC column (150 mm x 2.10 mm)

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(Phenomenex, Torrance, CA), held at 40 ºC during analysis. The mass spectrometer was

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equipped with an Agilent Jet Stream ESI source.

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acetonitrile in water, 9:1 v/v (mobile phase B) to 45% over 15 min water (mobile phase A) at

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0.35 mL/min. Ammonium acetate and acetic acid were added to pH 5 to each mobile phase. The

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MS analysis was performed in both positive and negative ion modes; the mass range was set to

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60-1700 Thomson (m/z); scan rate 4 spectra/sec, sample analysis time was 21 min per sample.

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Fragmentor voltage was 120 V, sheath gas flow was 11 L/min, and sheath gas temp was 350 ºC.

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For the reverse phase (RP) analysis, the 100 µL sample aliquot was dried down and re-suspended

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in 100 µL 9:1 methanol: toluene, 3 µL of sample was then injected. The data-dependent MS/MS

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analysis was performed on a pooled sample as described earlier17. For both analyses modes compound

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annotations were performed by comparing sample MS/MS spectra to the METLIN library18.

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Blood Diagnostics of Barataria Bay and Sarasota Bay Dolphins and Assessment of

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Respiratory Anomalies.

The gradient was changed from 100%

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The majority of the health diagnostic assays has been conducted routinely in previous

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dolphin health assessment studies and were previously reported for the wild animal cohorts in

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this study10, 19. Blood samples were sent to the Animal Health Diagnostic Center at Cornell

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University College of Veterinary Medicine (Ithaca, NY) for hematology, serum chemistry, and

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evaluation of endocrine function using standard methods19. The assessment of respiratory

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anomalies was conducted as described previously using pulmonary ultrasound10.

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Statistical Analysis.

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The LC/MS raw data files were first processed with Mass Hunter Qualitative Analysis

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B.05.00SP1 software in order to deconvolve each peak (Agilent; Santa Clara, CA). The peaks 6 ACS Paragon Plus Environment

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were aligned using Mass Profiler Professional 12.1 software. Data from both the managed

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population (San Diego data set) and the wild capture/releases (Barataria and Sarasota data set)

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were treated as a single data set for deconvolution and alignment to ensure the parameters used

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were consistent across the study. Principal Component Analysis (PCA) was applied for

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exploratory analysis and to study the internal variance of the data4. Metabolites present in less

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than 10% of the samples were removed, assuming they were not sufficiently reproducible and

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therefore of lesser diagnostic value.

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Partial least-squares (PLS)20 regression is a multivariate latent-variable method that

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relates one dependent variable (y) to a set of independent variables, X. Partial least-squares

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discriminant analysis (PLSDA) is the application of PLS to the classification of problems in

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which (y) is a vector that codifies the class of each sample. In our case, we were interested in

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using metabolite abundances to predict the sampling location of each data set (Sarasota Bay =

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SB; Barataria Bay = BB; San Diego = SD). Cross-validation where 66% of the samples were

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used as a training group and 34% as a test group was then carried out. Quality assessment of a

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model was performed by computing the sensitivity (samples of the class of interest correctly

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assigned to its class) and the specificity (samples not belonging to the class of interest correctly

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not assigned to that class) of the predicted class assignments4. The global accuracy of the model

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is reported as the sum of the specificity and sensitivity divided by two21, 22. PLSDA also reports

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information about which features makes the difference between groups; the chemicals were

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ranked by the Variable Importance in Projection (VIP) score. VIP scores estimate the importance

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of each variable in the PLSDA model. Variables with VIP scores higher than 0.8 were

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considered important.

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metabolites, a “70-20% filter23” was applied: peaks which were present between 70% in one

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group and 20% of samples in another group were removed. Furthermore, peaks that were present

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in less than 20% of samples in both groups were also removed.

Before applying PLSDA, in order to remove low reproducibility

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Where available, the identities of metabolites were proposed based on MS/MS

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fragmentation patterns. If MS/MS was not available, the compounds of interest have been

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tentatively identified based on exact mass and were annotated by comparing either MS/MS

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spectra or exact mass values to the METLIN library entries. The exact mass search was carried

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out with 20 ppm window with protonation, ammoniation and sodiation as possible charge 7 ACS Paragon Plus Environment


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acquisition modes. The list of potential candidates was then manually reviewed and the most

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likely candidate matches were selected. For example, protonated or ammoniated species were

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given priority, while non-biogenic compounds or compounds that would not be expected to

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occur in a marine environment have been excluded. In cases when no appropriate match was

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found or a large number of plausible matches existed, i.e. more than 3 plausible disparate

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structures or compound classes match the MS/MS and/or exact formula, the compound was

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presumed unidentified. In many cases, where a number of possible isomers exists (e.g. for

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lipids), although the exact structure could not be determined, the class of the molecular species

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was postulated. All compound identifications are putative at the level 3-4 of the Metabolomics

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Standards Initiative24.

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Correlation of EBC metabolites with blood analysis parameters was carried out for BB

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and SB dolphins. In order to fit a linear model between the predictors (EBC metabolites) and the

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responses (blood analysis parameters), stepwise regression25 using forward selection was applied

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to select the top 5 most important predictors for each response using the minimum BIC with K-

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fold cross-validation (K=5). All calculations were performed using the PLS_Toolbox v. 7.9

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(Eigenvector Research, Manson, WA, USA) in MATLAB v. 7.8 (The Mathworks AS,

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Massachusetts, USA) and JMP10 (SAS Institute Inc., USA).

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We next examined possible correlation between the EBC metabolite content and

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pulmonary abnormalities identified by ultrasound examination including pulmonary nodules,

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consolidation and alveolar-interstitial syndrome (AIS). In order to find potential clinically-

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relevant biomarkers, a stepwise linear regression using forward selection was also applied to

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each pulmonary abnormality.

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RESULTS

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Comprehensive Exhaled Breath Condensate (EBC) Metabolite Profiling.

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We collected and analyzed exhaled breath condensate from a managed collection San

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Diego (SD) and wild (Sarasota Bay (SB) and Barataria Bay (BB)) bottlenose dolphin

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populations. Principal component analysis (PCA) was initially applied to the LC/MS data for SB

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and BB animals (Figure S1). Partial least square discriminant analysis (PLSDA) was applied and 8 ACS Paragon Plus Environment

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validated using cross-validation, and the global accuracy of the PLSDA model was found to be

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95%. Table S1 lists the most important metabolite which allow discrimination between these

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groups (SB and BB dolphins) and corresponding tentative chemical metabolite identification.

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This table includes the unique metabolites present in only one of the groups, as well as

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statistically different common metabolites present in both groups, but at different abundance

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levels.

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Next, it was important to examine possible external confounding factors unrelated to

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health conditions that could artificially influence any observed differences between groups,

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including geographic location. To do this, we added a second healthy control group of managed

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collection animals from San Diego Bay, CA in the analysis (Figure 1). The PCA-score plot

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shows the SD dolphins cluster with the SB control population, indicating a similarity in the EBC

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samples and total metabolite profile between these two healthy reference groups. Compared to

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Figure 1S, the separation between SB and BB increased due to we are emphasizing the variance

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related to the healthy condition and decreasing the impact of confounding factors. PLSDA was

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also applied to the data comparing BB animals versus the combined SB and SD animals.

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Compared to this combined group, BB dolphins had a number of unique metabolites, and the

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accuracy of the model in this case was 85%. Table 1 lists the most important EBC metabolite

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that discriminate BB dolphins from the two healthy reference groups and the corresponding

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tentative chemical identifications.

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EBC Metabolite Correlation with Pulmonary Radiographic Analysis.

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We have examined possible correlation between the EBC metabolite content (BB

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dolphins) and pulmonary abnormalities including pulmonary nodules, consolidation, and

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alveolar-interstitial syndrome (AIS). No significant differences (p < 0.05) were observed for

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pulmonary nodules or AIS. However, there was a distinct correlation between dolphins with

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pulmonary consolidation (n=6) and specific breath-based metabolites. No pulmonary

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consolidation was detected in Sarasota Bay dolphins. The list of breath chemicals that correlate

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with pulmonary consolidation are considered putative biomarkers, and the corresponding

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tentative identification of these potential biomarkers are provided (Table 2).

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EBC Metabolite Correlation to Common Blood Measures. 9 ACS Paragon Plus Environment


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In order to elucidate whether specific blood parameters correlate to the exhaled

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metabolites, the first step was to apply PLSDA to obtain the most important blood parameter to

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discriminate the SB and BB groups. The VIP versus coefficients of the PSLDA model plot is

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shown (Figure S2). This plot identifies blood parameters that are influential relative to the fit for

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the response. For example, we saw that cortisol and glucose have both VIP values that exceed

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0.8 and relatively large coefficients. This finding is consistent with that reported in Schwacke et

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al.10

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The second step was to correlate the blood variables with EBC metabolites. To do so,

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stepwise regression was applied to find the most important EBC features. As an example, results

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for lymphocyte counts and cortisol are shown (Figure S3). To assess the quality of the results,

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the coefficient of regression and RMSE (Root Mean Squared Error) were reported. As can be

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seen, low values of cortisol and high values of lymphocytes are specific to BB dolphins. The

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remaining blood variables along with top five EBC metabolites that correlate with each variable

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are reported (Table S2).

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DISCUSSION

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Exhaled breath condensate (EBC) analysis.

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We observed a distinctly different breath-based metabolome in the population within

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Barataria Bay, Louisiana compared to reference populations in Sarasota Bay, Florida, and San

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Diego, California. Importantly, we found putative breath-based biomarkers in Barataria Bay

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dolphins that correlated with consolidations in lungs and multiple blood changes, including

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lower blood glucose and cortisol concentrations consistent with the hypoadrenocorticism seen

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previously observed10. Although the identification of a distinct breath-based metabolome in

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Barataria Bay dolphins does not confirm that the origin of all metabolite differences were

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directly related to petroleum product exposure, the findings of multiple unique compound classes

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in dolphins exposed to petroleum products paired with breath-based metabolite profiles

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associated with identified diseases caused by the oil spill provides a compelling case.


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Extensive, multi-year and multidisciplinary investigation of live and dead bottlenose

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dolphins in the northern Gulf of Mexico, especially those in heavily-oiled Barataria Bay,

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Louisiana, demonstrated that exposure to the spill’s petroleum products caused chronic lung and

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adrenal disease which contributed to increased mortality, lower survival, and poor reproductive

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success14,

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bacterial pneumonia and lung consolidation, possibly secondary to lung injury, and

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hypoadrenocorticism evidenced by low blood cortisol, aldosterone, glucose, and thin adrenal

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cortices. The results of this present study that are outlined in the previous sections corroborate

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these findings. Data for the comprehensive health assessments then allowed us to document

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specific breath-borne biomarkers that correlate with specific blood parameters as well as

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specified health conditions - most importantly lung consolidations.

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. Specifically, Barataria Bay post-spill dolphins had an increased prevalence of

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EBC and Lung Consolidation.

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Several interesting EBC metabolites were associated with lung consolidation identified

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by pulmonary ultrasound of BB dolphins. Lung consolidation on ultrasound can be an indicator

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of pneumonia in animals, including bottlenose dolphins and humans10, and can be used to help

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identify bacterial, viral, or fungal infections in the lung. Tentative metabolites associated with

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lung consolidation in BB dolphins are listed (Table 2). In several cases, postulated EBC

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molecular structures associated with lung consolidation in dolphins contain a glycan moiety (e.g.

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Ganglioside GT3 or Ganglioside GM2). These compounds tend to possess complex and difficult-

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to-characterize isomers, which often defines their biological functions. Therefore, instead of

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focusing on specific compounds, we considered general classes of identified compounds.

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Encouragingly, a number of compounds found in dolphin EBC would be expected to be

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observed given the presence of lung disease. In particular, we found evidence of cellular bilayer

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degradation (phospholipid moieties) that indicates nonspecific lung epithelial breakdown in

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lungs of animals with consolidation. Several of the tentatively proposed metabolites may be

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related to DNA and cellular damage processes, but unambiguous chemical identification is

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required to elucidate this possibility further. Some of the compounds were not expected in the

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context of the study, and chemical identification of these compounds may be of lower certainty. 11 ACS Paragon Plus Environment


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One such group of compounds includes glycosides, e.g., steroidal glycosides. Many of these

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compounds are usually of plant origin, although they may also occur in the marine environment.

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Also, we have tentatively identified several anti-infective agents that also often naturally occur in

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plants (e.g. alkaloids), although these may originate from marine algae11,

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bacterial metabolites. These compounds include, among other metabolites, leptomycin B,

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norselic acid A, and yiamoloside. Leptomycin B, a secondary metabolites of the Streptomyces

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spp actinobacteria, is an anti-fungal agent that also possesses anti-tumor activities10, 11, 14-16. The

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Streptomyces can be found in soil and rotting vegetation that are resent in animals’ habitat in

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coastal estuaries.

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refractory to standard chemotherapy, and it appears to result in G1 cell cycle arrest. Norselic acid

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A derives from the Crella sponge species, functions as an anti-infective steroid that displays

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antibiotic activity against methicillin-resistant Staphylococcus aureus (MRSA), methicillin-

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sensitive S. aureus (MSSA), vancomycin-resistant Enterococcus faecium (VRE), and Candida

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albicans10. Yiamoloside B is a fungistatic chemical belonging to a class of saponin compounds

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released from Phytolacca octandra10. At the present time, the origin and role of the detected

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metabolites are putative. Although these compounds appear to be meaningful in the present

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biological context, no conclusions should be drawn about biological role of these metabolites

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until structural confirmation. However, when confirmed and validated, such compounds may

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serve as non-invasive biomarkers of lung consolidation.

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or as secondary

Leptomycin B has been studied in human lung cancer cells which are

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EBC and Blood Analysis

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The next phase of the analysis sought to correlate breath metabolites to blood parameters

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in dolphins. Blood-based biomarkers are essential to understanding the health of dolphins in

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managed populations, including detection of inflammatory processes and infectious diseases,

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anemia and iron abnormalities, renal and liver diseases and more. Some of the metabolites in

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breath are partitioned from blood at the alveoli and thus may directly correlate with blood

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composition; this may be especially true of cetaceans, which have a double layer of capillaries in

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the lung and exhale a large volume of deep lung air with each breath26. In humans and other

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terrestrial animals, there is some evidence of breath-serum correlation in glucose metabolism27,

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emphysema exacerbations28, and lung cancer29. These investigations are built on the premise that 12 ACS Paragon Plus Environment

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systemic inflammation may be recognized in the lungs (and eventually breath) given the

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extensive capillary-alveolar interface network.

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correlated with breath biomarkers to varying degrees. Here, we restrict our discussion to those

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correlations which are robust and show a clear separation between the SB and BB dolphins based

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on the serum biomarkers.

In this study, several serum biomarkers

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EBC and Hypoadrenocorticsm.

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It has been previously demonstrated that cortisol levels were lower in Barataria Bay

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dolphins compared to Sarasota Bay dolphins. Lower cortisol levels in BB dolphins, paired with

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lower glucose, lower aldosterone, and thin adrenal gland cortices previously reported in this

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population, support an impaired hypothalamus-pituitary-adrenal axis caused by oil spill

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exposure. In the healthy SB dolphins, five breath metabolites (Table S2) correlated with higher

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cortisol levels (R2=0.81) (Figure S3). Elevated cortisol levels in healthy dolphins during catch-

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and-release protocols represent a normal response. Since we did not see consistent breath

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metabolites in the BB dolphins that correlated with their serum markers of hypoadrenocorticism,

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we speculate that the breath metabolites seen in the SB dolphins are markers of health rather than

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disease. It is possible that the BB dolphins were not able to produce the breath metabolites that

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indicate elevated, appropriate adrenal activity. This conjecture needs further evaluation. The

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breath metabolites that correlated with the normally-elevated cortisol levels in the SB dolphins

357

include cellular membrane products and fatty acid hydrolyzing agents, although the exact

358

identification and possible explanations for roles of these compounds are limited at the present

359

time.

360

Next, five breath metabolites were found to correlate with glucose levels in the SB

361

dolphins (R2=0.79), and overall the SB dolphins had higher glucose levels compared to the BB

362

dolphins. The elevated glucose levels in SB dolphins appear to be normal in healthy animals30

363

and may represent a non-pathologic, potentially necessary response to feeding31. The tentatively

364

identified breath metabolites that correlate with elevated glucose levels include triglycerides and

365

Vitamin D2 3-glucuronide (Table S2). As with the cortisol levels described above, the lack of

366

correlation between breath metabolites and glucose levels in the BB dolphins may reflect a 13 ACS Paragon Plus Environment


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367

disease state. Glucose levels in the BB dolphins were pathologically low compared to their SB

368

counterparts, possibly a marker of a poor glycemic response to feeding and/or stress. The

369

absence of breath metabolites likely indicates that the dolphins have abnormal glucose

370

metabolism which may be a part of a depressed hypothalamus-pituitary-adrenal axis. Overall,

371

glucose and cortisol levels seen in healthy dolphins correlate with several breath metabolites.

372

Further investigations are required to conclusively correlate the chemical identity of these

373

metabolites to specific physiological processes that cause such correlations. For example, for

374

blood glucose correlations, compounds that contain glycoside moiety were found (e.g. vitamin

375

D2 3-glucuronide), but the biological basis at this point is not elucidated. The fact that the BB

376

dolphins did not have correlative breath metabolites for glucose and cortisol levels also supports

377

impaired glucose and cortisol regulation. At the same time, though it is compelling to place

378

importance on one or two specific breath biomarkers, one must remember that the correlation

379

between any blood biomarker with breath metabolites must include the entire group of breath

380

metabolites.

381 382

EBC, inflammation, renal function, and iron metabolism.

383

Four additional serum biomarkers that differentiate BB from SB dolphins and correlate

384

with breath biomarkers in the BB group include: lymphocytes, blood urea nitrogen (BUN),

385

potassium levels, and transferrin saturation. Lymphocytes are white blood cells that generally

386

indicate a chronic infection or inflammation, as might be seen with a prolonged bacterial, viral,

387

or fungal pneumonia. Most acute infections engender an elevated peripheral segmented

388

neutrophil count, though this elevated neutrophil count may segue into a lymphocytosis given

389

enough time. Lymphocyte count is statistically higher overall in the BB group as shown Figure

390

S3b and this is likely a result of chronic inflammation and/or infection.

391

Last, levels of saturated transferrin correlated with several breath biomarkers in BB

392

dolphins (R2=0.81). Transferrin saturation is a biomarker of iron metabolism, and higher

393

saturations indicate iron overload. It has been described that bottlenose dolphins can develop iron

394

overload paired with insulin resistance, and that dolphins who eat fish with increased

395

heptadecanoic acid levels may have a reversal of the markers of iron overload and insulin 14 ACS Paragon Plus Environment

Page 15 of 28


396

resistance32. The exact dietary differences between SB and BB dolphins are not known, though

397

one would expect potential changes in prey to be accentuated by a large oil spill. It is possible

398

that the BB group did not have access to enough fish with adequate heptadecanoic acid levels to

399

effectively reduce their transferrin saturation levels compared to the SB group. However, the

400

clinical consequence of this presently remains unclear.

401 402

EBC Metabolites in Barataria Bay versus Healthy Reference Dolphin Populations.

403

Some of the more striking findings in BB dolphin breath are the tentatively identified

404

phospholipid moieties. Phosphatidic acid, phosphatidylethanolamine, and steroids were all found

405

in either higher abundance or uniquely in BB dolphins (Table 1S). The specific isomers of these

406

molecular species were not distinguished. In general, these lipid products suggest cellular

407

destruction including remnants of lipid bilayers, presumably from disintegrated respiratory

408

epithelial cells. This is an expected finding as petroleum products are toxic to mammalian

409

lungs33. However, phospatidylglycerol was also identified which comes from the breakdown of

410

lung surfactant, a phospholipid-protein mixture that confers both mechanical and immunologic

411

protection in animals34 and humans35. The finding of surfactant breakdown products in exhaled

412

breath suggests that aspirated contents, such as contaminated water, or inhalation of airborne

413

polycyclic aromatic hydrocarbons (PAHs) at the water surface, may have some role in

414

disintegrating surfactant. Or, as with lung infections or aspiration in humans, a clinical syndrome

415

similar to the human acute respiratory distress syndrome (a hyper-inflammatory syndrome of the

416

lungs marked by a loss of surfactant, alveolar filling with exudative fluid, dyspnea, and

417

hypoxemia) may have developed36.

418

When comparing BB to SB dolphins, we tentatively identified compounds that are likely

419

to be naturally-occurring macrolide-type antibiotics, arachidonic acid metabolites, and products

420

of lipid breakdown (Table S1). We tentatively identified the following macrolide antibiotics in

421

the BB and not in the SB dolphins’ breath: chivosazole E, leukomycin A1 and A7, lansonolide

422

A, jadomycin B, and mycolactone. Structural isomers of these compounds are also possible.

423

The identification of leukotriene E3 in the breath of Barataria Bay dolphins is particularly

424

notable. This compound is a metabolite of arachidonic acid and is known to be a stable marker of 15 ACS Paragon Plus Environment


Page 16 of 28

425

asthmatic inflammation found in biologic fluids including breath condensate37. Thus, leukotriene

426

E3 may be a breath-based indicator of lung disease in Barataria Bay dolphins.

427

In general, antibiotics identified in BB dolphins are most likely metabolic products of

428

bacteria and fungi, and their exclusive presence in the BB group (and not in the SB group)

429

suggests high microbial presence within animals’ respiratory system and/or in the Barataria Bay

430

waters. This hypothesis would be consistent with the high prevalence of Barataria Bay dolphins

431

that stranded and died with bacterial pneumonia38. Chivosazole E is produced by Sorangium

432

cellulosum, and possesses antifungal and cytotoxic properties10,

433

mammalian cells40. Leukomycin A1 and A7 belong to a group of macrolide antibiotics produced

434

from Streptomyces kitasatoensis41 with a wide range of antibiotic, and some anti-neoplastic,

435

properties. Lansonolide is produced from the Caribbean sponge, Forcepia sp.42, and possesses

436

defined anti-neoplastic activity against lung cancer cells43. Jadomycin B is produced by

437

Streptomyces venezuelae, and it has a wide range of antimicrobial activity including methicillin-

438

resistant Staphylococcus aureus11. One of the tentatively identified compounds, mycolactone is a

439

potent macrolide antibiotic which is produced by mycobacteria, including Mycobacterium

440

marinum and M. ulcerans44. M. marinum is a bacterium with a global presence in fresh and

441

saltwater 45. M. ulcerans is also associated with water, although sources of M. ulcerans appear to

442

be predominantly fresh water with a potential vector-borne (mosquito or other aquatic insect)

443

component

444

other animals, including nodules and ulcers

445

cutaneous tissues, by inhibiting local immune responses, and it is the main toxin associated with

446

human buruli ulcers linked to M. ulcerans outbreaks48. M. ulcerans outbreaks in humans

447

typically occur in subtropical and tropical wetlands during periods of environmental

448

disturbance49, though there are no published reports of the mycobacterium affecting the Gulf

449

region or dolphins before or after the BP oil spill. Further, there was no evidence of

450

Mycobacterium-associated skin lesions noted during live health assessments or in dead, stranded

451

dolphins in BB50. Oil-contaminated seawater could alter endemic seawater bacteria, though little

452

data exist that has identified the ramifications of such alterations51. It is described that bacterial

453

populations around off-shore oil platforms and oil-contaminated seawater are unique52, 53, though

454

to date there is little connection between oil-contamination and antibiotic production from

455

bacteria. Possible bacterial metabolites identified in the breath of Barataria Bay dolphins suggest

46

39

with specific toxicity to

. Both M. marinum and M. ulcerans can cause cutaneous lesions in humans and 47

. Mycolactone can damage tissues, primarily


Page 17 of 28


456

that these metabolites reflected bacteria present in the lungs of dolphins with pneumonia,

457

although further studies are needed to confirm chemical identities of metabolites particular to the

458

BB animals, to demonstrate that bacterial populations change in response to oil contamination,

459

and that these changes result in increased antibiotic production. Therefore, at the present time the

460

findings of the antibiotic compounds should only be considered in the context of the present

461

study pending further confirmation.

462

Though the focus of this investigation is on the breath metabolites of the BB dolphin

463

population, there were some unique metabolites identified in the SB animals. These tentative

464

metabolites include L-gizzerosine and haemulcholic acid. L-gizzerosine may derive as a by-

465

product from mackerel ingestion, a common food source for dolphins, and haemulcholic acid is

466

found in bile. It is presumed that these metabolites may represent differences in prey availability

467

for SB and BB dolphins.

468

When the breath metabolites from the two unexposed groups (SB and SD dolphins) were

469

combined and compared to the BB group, many of the same compounds were identified (e.g.

470

DG, PC lipids, Leucomycin) while even more metabolites were found to be specific to BB

471

dolphins (Table 1). Many of these breath metabolites were again markers of lipid oxidation,

472

arachidonic acid metabolism and lung surfactant breakdown. These compounds were presumably

473

originating from epithelial injury seen at a higher proportion in the BB group than the SB or SD

474

dolphins. The increased number of BB-specific metabolites when compared to the combined

475

group of control healthy animals indicates that some of these compounds may be present in

476

control animals, albeit with lower occurrence. Increasing the number of healthy animals led to

477

some of these compounds to not pass the “70% filter” for peak selection (described in the

478

“Methods” supplemental material), as these metabolites were detectable in fewer healthy

479

animals.

480

It is important to point out that there is a large degree of overlap between exhaled

481

metabolites that differentiate dolphin populations (Table S2), and many of these biomarkers

482

statistically correlate with ultrasound findings and/or blood parameters. This strongly indicates

483

that these metabolites are most likely not statistical aberrations but rather meaningful chemicals

484

that are engendered by specific health conditions (e.g., pneumonia and inflammation). An

485

example compound is phosphatidylglycerol such as PG(12:0/15:1(9Z)) or isomer, which 17 ACS Paragon Plus Environment


486

differentiates oiled from healthy dolphins (Table S1), as well as is one of the most important

487

breath metabolites that correlate with lung consolidation (Table 2). In another example, a

488

compound postulated as Leucomycin is one of the compounds that differentiates SB and BB

489

animals while also correlates with inflammation (lymphocytes, Table S2).

Page 18 of 28

490

This study supports that exhaled breath analysis may become a key tool to non-invasively

491

assess dolphin54. EBC biomarkers appear to change in response to dolphin health in general and

492

specific issues such as infection or lung consolidation, in particular. Despite potential

493

confounding factors that may contribute to breath metabolite differences between groups (e.g.

494

geography, food supply, or water quality), we found the BB group differed from the SB and SD

495

dolphins. The managed collection animals were healthy, while some of the wild animals may

496

have had sporadic normal baseline health variations such as minor infections. The documented

497

breath metabolites that distinguished the affected BB population mostly fell into two categories:

498

products of cellular breakdown and naturally-occurring bacterial and fungal metabolites. The

499

increased amount of cellular breakdown products fit the proposed mechanism of aspirating or

500

inhaling noxious agents, though it is not yet clear if the products we detected were specific to BP

501

oil spill-associated petroleum products, dispersants, or to pulmonary inflammation in general.

502

Although it is tempting to draw conclusions based on biomarker differences between

503

groups, we see the main impact of this study to be the correlation of EBC metabolites with

504

established radiographic and blood markers of cetacean health. If the EBC metabolites can serve

505

as a proxy for biomarkers in blood (or other matrices) and correlate with ultrasound or other

506

assessment methodologies data, then EBC analysis could be used in lieu of those methodologies

507

for field health assessments, both routine and during critical events, such as environmental

508

disasters or mortality events. The methodology will facilitate such assessments for some species

509

and will enable them for others, for which these assessments have never been conducted due to

510

logistical difficulties.

511 512

ACKNOWLEDGEMENTS


Page 19 of 28


513

Support for these investigators was provided by: the Office of Naval Research grant #N-

514

00014-13-1-0580 [CED, SVW]; National Institutes of Health (NIH) grant number

515

#1U01EB022003-01 and #UL1RR024146-06 and #1P30ES023513-01A1 [CED]; NIH #T32-

516

HL007013

517

#8KL2TR000134-07 K12 mentored training award and NIH #1K23HL127185-01A1 [MS]; and

518

Dolphin Quest, Inc. [RSW]. Sample collections in Sarasota Bay and Barataria Bay were part of

519

the Deepwater Horizon NRDA being conducted cooperatively among NOAA, other Federal and

520

State Trustees, and BP. This work was performed under an animal care and use protocol

521

reviewed and approved by the Navy Marine Mammal Program Institutional Animal Care and

522

Use Committee and the Navy Bureau of Medicine. The authors would like to thank Daniel J.

523

Peirano for data analysis discussions.

524

responsibility of the authors and do not necessarily represent the official views of the funding

525

agencies.

526

Zoological Society and conducted under National Marine Fisheries Service Scientific Research

527

Permit No. 15543, and the study in Barataria Bay was led by NOAA and conducted under

528

National Marine Fisheries Service Scientific Research Permit No. 932-1905/MA-009526.

and #T32-ES007059 [MS]; UC Davis School of Medicine and NIH

The contents of this manuscript are solely the

The dolphin health assessment study in Sarasota Bay was led by the Chicago

529 530 531 532 533

The supporting information has 8 pages, containing 3 figures (Figure S1, Figure S2, and Figure S3) and 3 table (Table S0, Table S1, Table S2).

534 535 536 537 538 539 540 541 542 543 544 545

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698 699 700 701 702



703

Page 24 of 28

TOC

704 705 706 707

Figure 1: PCA score plot of the EBC metabolome sampled from San Diego and Sarasota and Barataria. N is the number of samples.

708

709 710 711 712 713 714


Page 25 of 28

715 716 717


Table 1. Significantly altered metabolites in exhaled breath condensate and key discriminants in oil spillaffected bottlenose dolphins living in Barataria Bay compared to healthy reference dolphins (San Diego and Sarasota Bay).

Retention Time

Tentative Chemical Identification

132.0788

4.392

Undetermined*

160.0873

1.754

4-Cyanoindole

246.0781

1.86

250.178

Mass

Class

Fold Change a

Directio nb Related to Healthy Referenc e Dolphins

pFDRc

4.65E09 2.36E12 5.67E08 3.53E03 5.92E07 8.79E03 1.06E10 5.82E07

78

UP

44

UP

Undetermined*

44

UP

2.172

Undetermined*

0.3

DOWN

300.1927

1.883

Undetermined*

133

UP

300.2773

9.072

Decanoylcholine

0.4

DOWN

310.1087

1.482

Undetermined*

32

UP

318.2025

1.884

Undetermined*, (Adrenosterone or other steroid)

Steroid/Li pid

96

UP

326.1946

4.464

Possibly 1-[(5-Amino-5carboxypentyl)amino]-1-deoxyfructose

Amino Acids Derivative

18

UP

2.72E21

365.2399

2.019

R/S-4-benzyl-3-((S)-3-hydroxy-2,2dimethyloctanoyl)oxazolidin-2-one

97

UP

3.29E11

1.762

lipid: Docosatetraenoyl Ethanolamide, Nethyl N-(2-hydroxy-ethyl) arachidonoyl amine etc.

0.5

DOWN

5.05E01

422.2343

1.467

Possibly 7α-(Thiomethyl)spironolactone sulfoxide or a 15beta-Hydroxy-7alphamercapto-pregn-4-ene-3,20-dione 7acetate

67

UP

1.39E48

429.3815

5.973

Possibly 25-Azacholesterol

0.5

DOWN

3.81E02

437.371

1.927

Steroid, e.g. 5beta-Cholestane3alpha,7alpha,24,26-tetrol, 5-bCholestane-3a-7-tetraol etc.

0.6

DOWN

1.05E01

458.2117

1.727

Undetermined*, possibly a metoxyphenol

67.3

UP

496.2308

6.459

Possibly WYE-354

62.6

UP

497.3201

2.311

Possibly a steroid, e.g. Pregnanediol-3glucuronide

Steroid/Li pid

138

UP

514.3156

1.956

Undetermined*, possibly G-418 or PG(17:1(9Z)/0:0)

Lipid

364

UP

393.3421

Amine

Lipid

Lipid

Lipid Lipid


4.93E07 3.43E12 3.11E37 5.79E07


537.4229

1.938

Possibly N-Methylindolo[3,2-b]-5alphacholest-2-ene

549.2809

1.724

Undetermined* (Antimycin A1 or Myristinin A)

549.3429

1.821

PG(O-20:0/0:0)

566.2995

1.759

Imazamethabenz or Archangelolide or Antimycin A1

583.2537

1.704

Possibly Biliverdin IX

627.4904

1.861

A diglyceride, e.g. DG(17:1(9Z)/20:5(5Z,8Z,11Z,14Z,17Z)/0: 0)[iso2]

633.4085

1.967

Oleanolic acid 3-O-beta-D-glucosiduronic acid

681.4653

2.268

A Phosphatidylglycerol, e.g. PG(17:0/12:0)

693.4024

2.221

Phosphatidylglycerol

722.3751

1.684

25-Acetyl-6,7-didehydrofevicordin F 3glucoside

737.4277

2.328

Myxochromide S2

743.5735

2.446

A Phosphatidylethanolamine lipid

755.4858

2.35

A Phosphatidylglycerol,

759.569

2.27

A Phosphatidylethanolamine or Phosphatidylcholine

780.4212

1.711

Leucomycin A7

781.4519

2.441

Digoxin or Gitoxin

797.3611

1.649

Possibly Rifamycin B

805.5958

1.784

A Phosphatidylglycerol or Phosphatidylserine

809.5625

1.889

A Phosphatidylglycerol or Phosphatidylinositol

819.5708

1.953

Undetermined* (a Phosphatidylcholine)

825.479

2.568

Yiamoloside B

879.6141

1.93

A Phosphatidylglycerol

1.673

(3b,16a,20R)-3,16,20,22,25Pentahydroxy-5-cucurbiten-11-one 3[rhamnosyl-(1->4)-[glucosyl-(1->6)]glucoside]

994.5428

Steroid/Li pid Secondary bacterial metabolite Lipid Secondary bacterial metabolite

Page 26 of 28

80

UP

9.64E12

79

UP

1.26E05

374

UP

5.92E07

206

UP

6.05E07

139

UP

1.49E05

36.6

UP

3.13E11

72.4

UP

9.60E07

69

UP

7.34E08

40.9

UP

3.04E26

300.6

UP

1.45E05

69.2

UP

1.64E11

146

UP

46

UP

45

UP

381

UP

1.25E07

130

UP

1.27E44

272

UP

8.77E11

545

UP

1.86E11

53

UP

4.38E06

119

UP

188

UP

80

UP

301

UP

Lipid

Lipid Secondary bacterial metabolite

Secondary bacterial metabolite Lipid Lipid Lipid Secondary bacterial metabolite Secondary bacterial metabolite Lipid Lipid

Terpenoid Lipid


1.75E05 2.61E05 6.76E12

3.55E06 1.31E07 3.06E06 9.89E09

Page 27 of 28


* no reasonable matches, too many possible alternatives or identification not possible a ratio of means relative to Sarasota and San Diego samples

718 719 720 721 722 723 724 725 726 727

b

direction of change in means relative to Sarasota samples

c

false discovery rate adjusted mixed effects model p-value

Table 2: List of the most important EBC metabolite that correlate with the pulmonary disease in Barataria Bay bottlenose dolphins (consolidation) as determined by ultrasound examinations conducted during 2011 following the 2010 Deepwater Horizon oil spill. Fold Compared to BB Dolphins without Lung Consolidationa

Mass

Retention Time

t.test adjusted pvalue55

246.1016

2.695

0.051

3.5

Debromohymenialdisine

363.2358

12.708

0.051

2.9

Dimethisterone or other steroid

310.1082

1.492

0.051

2.5

Undetermined*

416.1507

2.049

0.051

2.5

Undetermined*

422.2346

1.495

0.051

2.5

Possibly 7α-(Thiomethyl)spironolactone sulfoxide or a 15beta-Hydroxy-7alphamercapto-pregn-4-ene-3,20-dione 7-acetate

580.2943

8.601

0.051

2.5

Protoporphyrin IX

458.2125

1.709

0.051

2.4

Undetermined*, possibly Metoxyphenol

825.4798

2.568

0.051

2.3

Yiamoloside B

318.2064

1.902

0.051

2.1

Undetermined*, possibly Adrenosterone or other steroid

625.4772

2.087

0.051

2.1

Diacylglycerol

739.4724

1.971

0.051

2.1

Antanapeptin B or a steroid glucoronide

1004.7853

1.697

0.051

2.1

LacCer(d18:0/26:0) or NAPE(16:0/18:1(9Z)/20:4(5Z,8Z,11Z,14Z)

453.2938

2.193

0.051

2

Norselic acid A

472.2984

5.849

0.051

2

Deoxodeoxydihydrogedunin

737.4288

2.333

0.051

2

Myxochromide S2

781.4548

2.436

0.051

2

Digoxin or Gitoxin

999.7644

1.75

0.051

2

PI-Cer(t20:0/26:0(2OH))

Tentative chemical Identification



742.4488

7.406

0.051

1.9

Erythromycin C or Phosphatidylinositol lipid, e.g. PI(10:0/16:1(9Z))

310.157

1.748

0.051

1.8

Undetermined*, possibly Butenachlor

541.3468

2.433

0.051

1.8

Leptomycin B or PG(20:0/0:0)

651.4197

1.864

0.051

1.8

Phosphatidylglycerol, e.g. PG(12:0/15:1(9Z))

695.5196

2.155

0.051

1.7

Undetermined*, likely a lipid e.g. PG(O16:0/15:0)

605.4459

1.974

0.051

1.5

Phospholipid, e.g. PA(P-18:0/12:0)

323.1987

3.877

0.001

Noninvasive Respiratory Metabolite Analysis Associated with Clinical

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