A casein hydrolysate with glycaemic control properties: evidence from

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Bioactive Constituents, Metabolites, and Functions

A casein hydrolysate with glycaemic control properties: evidence from cell, animal models and humans. Elaine Drummond, Sarah Flynn, Helena Whelan, Alice B Nongonierma, Therese Anne Holton, Aisling Robinson, Thelma Egan, Gerard Cagney, Denis C Shields, Eileen R. Gibney, Philip Newsholme, Celine Gaudel, Jean-Christophe Jacquier, Nessa Noronha, Richard J Fitzgerald, and Lorraine Brennan J. Agric. Food Chem., Just Accepted Manuscript • DOI: 10.1021/acs.jafc.7b05550 • Publication Date (Web): 11 Apr 2018 Downloaded from http://pubs.acs.org on April 11, 2018

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

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A casein hydrolysate with glycaemic control properties: evidence from cell, animal

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models and humans.

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Elaine Drummond1*, Sarah Flynn1*, Helena Whelan1, Alice B Nongonierma2, Thérèse A

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Holton3, Aisling Robinson4, Thelma Egan1, Gerard Cagney4, Denis C Shields3, Eileen R

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Gibney1, Philip Newsholme4, Celine Gaudel4, Jean Christophe Jacquier1, Nessa Noronha1,

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Richard J FitzGerald2, Lorraine Brennan1#

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Affiliations:

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1

School of Agriculture and Food Science, Institute of Food and Health and Food for Health

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Ireland (FHI), University College Dublin, Belfield, Dublin 4, Ireland

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2

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Health Ireland (FHI), University of Limerick, Limerick, Ireland.

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3

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Biomolecular and Biomedical Research, University College Dublin, Belfield, Dublin

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4, Ireland.

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4

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Conway Institute of Biomolecular and Biomedical Research, University College Dublin,

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Belfield, Dublin 4, Ireland.

Department of Biological Sciences, University of Limerick, Limerick, Ireland; Food for

School of Medicine, Food for Health Ireland (FHI) and UCD Conway Institute of

School of Biomolecular and Biomedical Sciences, Food for Health Ireland (FHI) and UCD

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# Corresponding author:

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Professor Lorraine Brennan, Institute of Food and Health, University College Dublin,

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Belfield, Dublin 4, Ireland.

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Email: [email protected]

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Phone: 00353 1 7162811

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Fax: 00 252 1 716000

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*Both authors contributed equally to the manuscript

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Abstract

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Evidence exists to support the role the dairy derived proteins whey and casein in glycaemic

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management. The objective of the present study was to use a cell screening method to

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identify a suitable casein hydrolysate and to examine its ability to impact on glycaemia

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related parameters in an animal model and in humans. Following screening for ability to

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stimulate insulin secretion in pancreatic beta cells a casein hydrolysate was selected and

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further studied in the ob/ob mouse model. An acute postprandial study was performed in 62

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overweight and obese adults. Acute and long term supplementation with the casein

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hydrolysate in in vivo studies in mice revealed a glucose lowering effect and a lipid reducing

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effect of the hydrolysate (43% reduction in overall liver fat). The postprandial human study

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revealed a significant increase in insulin secretion (p=0.04) concomitant with a reduction in

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glucose (p=0.03). The area under the curve for the change in glucose decreased from 181.84

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± 14.6 to 153.87 ± 13.02 (p=0.009). Overall, the data supports further work on the

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hydrolysate to develop into a functional food product.

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Keywords: Casein, Hydrolysate, Postprandial Glycaemia, insulin, nutrition

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Introduction

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Poor metabolic health increases the risk of the development of Type II Diabetes Mellitus

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(T2DM) (1) and the associated frequent hyperglycaemic episodes greatly increase

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cardiovascular disease risk, which occurs 2-4 times more often in the diabetic population (2).

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In 2010, the International Diabetes Federation (IDF) estimated that diabetes care accounted

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for €260 billion or 11.6 % of the total world expenditure on healthcare (3). It is understood

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that altering environmental factors such as diet can modify disease risk and improve long-

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term health outcomes (4) and accumulating evidence links dairy consumption with a reduced

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likelihood of developing metabolic syndrome (5-13). Consumption of Fermented dairy

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products, including low-fat cheese, buttermilk, and yoghurt has been associated with a

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reduced likelihood of T2DM onset (14, 15). Multiple components of milk have shown a

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propensity to improve postprandial glycaemic function (16-18), yet the key constituents

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appear to be casein and whey protein fractions. In particular, most likely due to an elevated

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rate of digestion and absorption (19, 20), hydrolysed casein and whey peptides have shown

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particular efficacy in optimising glycaemic management (21, 22). As a result of the

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demonstrated functional ability these are often referred to as bioactive peptides.

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A large body of evidence supports the insulinotropic function of certain amino acids

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and peptides (23). Although the major protein in milk is casein (comprising approximately

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80%), to date there has been a greater focus on whey proteins in the literature. When ingested

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intact, whey proteins have a rapid impact on insulin secretion, faster than micellar casein,

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which coagulates in the acidic gastric environment and transits more slowly (24). Following

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consumption whey exits the stomach more quickly and induces rapid increases in plasma

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amino acid levels (25). Recently, focus on the behaviour of casein hydrolysates has shown

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that these adopt a quicker transit time, thereby achieving more rapid uptake of amino acids.

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In 2013, Boutrou et al. (26) conducted a study on the gastrointestinal fate of casein,

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examining the release of various peptides in the jejunum of healthy human volunteers.

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Following ingestion of casein medium-sized peptides were released 6 hours later, while

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larger peptides were released from whey proteins at earlier time points.

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Much of the work examining bioactive peptides in the context of glycaemic

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management has targeted T2DM populations and many studies have used the bioactive

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peptides in combination with amino acids with insulin secretion promoting effects such as

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leucine. In a group of type II diabetic subjects consumption of casein hydrolysate/ leucine

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after a main meal demonstrated their ability to enhance insulin secretion compared to a

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placebo beverage (21). Manders et al (27) reported that administration of a carbohydrate

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bolus along with a casein hydrolysate plus added leucine in 10 T2DM males improved the

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insulin response in comparison to a carbohydrate-only control. Furthermore in a separate

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study it was shown that such a response could be maintained even without the addition of

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amino acids (28). Elsewhere, in a randomised controlled trial (RCT) of 13 T2DM patients (5

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females), a 50g oral glucose tolerance test was carried out using three test treatments: 0, 6 or

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12g casein hydrolysate (18). In this case the 12g casein hydrolysate had a significant, positive

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effect on the postprandial insulin and glucose AUC (area under the curve) values. The

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evidence for casein hydrolysates achieving a reduction in postprandial glucose in T2DM

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patients is growing; however, further studies on the long term effects are needed.

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The effects of dairy protein ingestion by non-diabetic, at risk overweight and obese

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human subjects have not been extensively studied. However, there is some evidence to

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support a functional role of hydrolysates in this population. In an RCT of 70 healthy,

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overweight or obese men and women, whey protein was compared to casein or glucose

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supplementation over a 12 week period (29). Significant reductions in fasting insulin and

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homeostasis model assessment of insulin resistance (HOMA-IR) levels were observed in the

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whey treated group compared with the control. No significant effects were demonstrated for

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the casein group, however it is noteworthy that the study utilised an intact casein. However,

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more favourable results were obtained when a hydrolysed casein was employed: Bendsten et

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al. (2014) (25) recruited 24 healthy, overweight men and women to compare the acute effects

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of hydrolysed casein (DH:37%), intact casein and intact whey on biochemical and perceptual

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markers of glycaemic and appetite regulation. Glucose concentrations were higher after

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ingestion of intact casein than after hydrolysed casein. In this case the intact whey was

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similar to the hydrolysed casein. No differences were seen in 24 hour or postprandial energy

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expenditure or appetite regulation. Animal studies have also highlighted the potential positive

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effects of hydrolysed casein: following consumption of the hydrolysed casein for 8 weeks the

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animals displayed an array of preferable metabolic characteristics such as lower respiratory

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exchange ratio and higher spontaneous locomotor activity (30). Furthermore, the mice fed

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with the hydrolysate had lower plasma glucose concentrations and concomitantly strongly

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reduced insulin levels.

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Overall, the current literature supports the concept of the use of casein hydolysate for

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blood glucose regulation. However, the type and extent of peptides and amino acids released

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during enzymatic hydrolysis (and consequently the bioactivity) is dependent on the

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parameters employed (i.e., temperature, time, pH, enzyme concentration, total solids, etc.)

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during the hydrolytic reaction (31). The objective of the present was to use a cell screening

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method to identify a suitable casein hydrolysate and to examine its glycaemic reduction

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ability in animal models and in humans.

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Materials and Method

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Chemicals

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All chemicals were purchased from Sigma unless otherwise stated. Ultrasensitive Rat Insulin

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ELISA, Mouse insulin ELISA, High sensitivity insulin ELISA, C-peptide ELISA kits were

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Mercodia.

RPMI

1640

culture,

Foetal

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purchased

Calf

Serum

(FCS),

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Penicillin/streptomycin (100 units/ ml, 0.1 mg/ml) were purchased from Invitrogen

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Haematoxylin, Eosin were purchased from Clin-Tech. GIP ELISA, Glucagon-like peptide-1

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(GLP-1) ELISA kits were purchased from Merck Millipore. Rodent Islet isolation

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formulation was purchased from Roche. Bicinchoninic (BCA) assay kit was purchased from

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Pierce, Thermo Scientific.

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Bioactive hydrolysate

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A sodium caseinate hydrolysate, referred to as the “casein hydrolysate” was prepared as

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previously described by Nongonierma and FitzGerald using food-grade gastro-intestinal

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enzymes (32). Briefly, the starting milk protein substrate (sodium caseinate, Kerry Group Plc,

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Listowel, Ireland) was suspended at 10 % (w/w) on a protein basis in water and dispersed

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under agitation at 50°C for 1 h using an overhead stirrer (Heidolph RZR 1, Germany) and

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hydrolysed for 1 h at 50°C. A control sample without enzyme was removed from the protein

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dispersion and maintained at 50°C for the duration of the hydrolysis reaction. Hydrolysis was

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carried out at a constant pH of 8.0 or 7.0 using a pH Stat (Titrando 843, Tiamo 1.4 Metrohm,

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Dublin, Ireland). The gastro-intestinal enzyme preparation was inactivated by heating the

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hydrolysate samples at 90°C for 20 min.

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The casein hydrolysate was fractionated using an ultrafiltration (UF) unit (Sartoflow Alpha

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filtration system, Sartorius, Germany). Fractionation was carried out using membranes

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having 5 and 1 kDa molecular weight cut-off (MWCO) values for the casein hydrolysate. The

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hydrolysates and the four UF fractions (permeates and retentates for 5 and 1 kDa cutoffs)

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collected were freeze-dried (FreeZone 18L, Labconco, Kansas City, U.S.A.) and stored at -

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20°C until further analysis.

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Reversed-phase ultra-performance liquid chromatography and molecular mass distribution

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of peptides and proteins in the casein hydrolysates

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The sodium caseinate and corresponding hydrolysate (UL 291) and UF fractions were

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analysed by liquid chromatography using an ultra-performance liquid chromatograph (UPLC

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Acquity - Waters, Dublin, Ireland) as described by Nongonierma and FitzGerald (32). The

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molecular mass profile of the proteins and peptides was determined by gel permeation

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chromatography using high performance liquid chromatography (GPC-HPLC) essentially as

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described by Spellman et al. (33). Each sample was analysed in duplicate.

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BRIN-BD11 cell culture and Insulin secretion assay

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The BRIN-BD11 cell line is a functional rat clonal insulin-secreting pancreatic β-cell line.

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BRIN-BD11 cells were maintained in GI-1640 containing 11.1 mM glucose, supplemented

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with 10 % (v/v) foetal calf serum, 2 mM glutamine, 50 IU/ml penicillin, 0.05 mg/ml

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streptomycin and incubated at 37 ˚C in a humidified atmosphere containing 5 % CO2 and 95

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% air. BRIN-BD11 cells were seeded at a density of 2 x 105 cells/well in 1 ml of media in 24-

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well plates for 24 hour in GI-1640 media containing 11.1 mM D-glucose. The cells were

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incubated with 1 ml Kreb’s Ringer Bicarbonate buffer (KRB) (pH 7.4) (115 mM NaCl, 4.7

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mM KCl, 1.28 mM CaCl2, 1.2 mM MgSO4.7H2O, 1.2 mM KH2PO4, 10 mM NaHCO3, 0.1 %

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BSA), supplemented with 1.1 mM glucose for 40 min. The cells were stimulated with 1ml

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KRB supplemented with 16.7 mM glucose plus 1 mg/ml of solution of interest (casein

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hydrolysate) for 20 minutes at 37 ˚C. The positive control 16.7 mM glucose plus 10 mM

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alanine was used. Insulin secretion was determined using the Mercodia Ultrasensitive Rat

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Insulin ELISA kit (Mercodia AB, Uppsala, Sweden). For the insulin secretion assays with

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synthetic peptides, the peptides were supplied by Peptide 2.0, USA at > 98% purity.

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3T3-L1 adipocyte cell culture and conditioned media collection and preparation

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The adipocyte cell line was maintained in DMEM containing 25 mM glucose, supplemented

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with 10 % (v/v) foetal calf serum, 50 IU/ml penicillin, 0.05 mg/ml streptomycin and

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incubated at 37 °C in a humidified atmosphere containing 5 % CO2 and 95 % air. 3T3-L1

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differentiation was induced in fully confluent 3T3-L1 pre-adipocytes by adding 3-isobutyl-1-

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methylxanthine (500 mM), dexamethasone (1 µM) and insulin (0.01 mg/ml) for 48 hours.

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Media was retrieved from the adipocytes both pre and post differentiation. The adipocyte

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conditioned media was removed from the cells 72 hours following the addition of the

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differentiation media. DMEM media was used as the control. All media were diluted 1 in 2

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with sterile water prior to cell treatment.

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BRIN-BD11 cell treatment with of differentiated conditioned media

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BRIN-BD11 cells were seeded in T175 flasks at a density of 3 x 106 cells and allowed to

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grow for 48 hours. Cells were treated with 15 ml of differentiated conditioned media,

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differentiated conditioned media with casein hydrolysate or DMEM as a control for 2 hours.

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Following treatment, cells underwent a methanol:chloroform metabolite extraction and,

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subsequently, a bicinchoninic (BCA) assay to determine protein content (Pierce, Thermo

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Scientific, Rockford, 1L61105, USA). Acute insulin secretion was measured as described

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above, following 2 hour incubation with the adipocyte conditioned media and conditioned

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media supplemented with either the casein hydrolysate or the backbone synthetic peptide.

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Islet isolation, culture and acute insulin secretion assay

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The pancreas was digested with 3 ml of isolation buffer consisting KRB buffer (pH 7.4)

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supplemented with 1.38 mg/ml liberase Rodent Islet isolation formulation (Roche, Welwyn

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Garden City, U.K.) and 1.83 mg/ml each of egg white and soybean trypsin inhibitors. The

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pancreas was digested by incubating in a water bath at 37 ˚C while shaking. Islets were

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washed twice in KRB buffer, resuspended in KRB buffer and place on ice until the islets

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were collected. Individual islets were isolated and cultured in batches of 20 in untreated

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culture plates overnight in RPMI 1640 culture medium, 10 % FCS (Invitrogen, Biosciences,

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Dublin, Ireland) and penicillin/streptomycin (100 units/ ml, 0.1 mg/ml; Invitrogen,

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Biosciences, Dublin, Ireland) and maintained at 37 ˚C in a 5 % CO2 humidified atmosphere.

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Islets in groups of three were incubated in 3 mmol glucose/l KRB for 30 minutes at 37˚C.

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Following this, islets were incubated in KRB buffer containing 20 mmol glucose/l plus casein

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hydrolysate or 3 mmol glucose/l KRB plus casein hydrolysate for 2 hours at 37˚C. Islets

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were treated with casein hydrolysate at concentrations of 0.1 mg/ml, 0.5 mg/ml and 1.0

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mg/ml. Islets were centrifuged, the supernatant was collected and the amount of secreted

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insulin was determined by Mouse insulin ELISA (Mercodia, Uppsala, Sweden). The data is

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presented as fold difference in insulin secretion between isolated islets which were treated

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with low (3.3 mM) and islets which were treated high glucose (20 mM).

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Animal studies

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All procedures were performed with the approval from the UCD research Ethical board

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(AREC-P-09-26). All mice were maintained in a controlled environment with 12h/12h

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dark/light cycles at 22˚± 2 and have specific pathogen free (SPF) status. They were given free

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access to standard pelleted laboratory rodent chow and filtered water. For all animal

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experimental studies, ob/ob and C57BL/6 male mice, at the age of 12 weeks were used.

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Ob/ob mice were sourced from Charles River, UK and C57BL6 mice were sourced in house

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from the UCD Biomedical facility, Dublin.

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Acute Treatment with casein hydrolysate

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Animals were fasted overnight for 16 hours prior to the acute experiment. The following day,

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commencing at 10am, fasting blood glucose levels were measured using a Medisense Optium

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Xceed (Abbott, Ireland) glucometer before the treated animals received 100 µl of casein

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hydrolysate at 100 mg/kg body weight via oral gavage (Instech PA, USA) 1 hour prior to the

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glucose tolerance test, control mice received 100 µl distilled H2O via oral gavage (Instech

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PA, USA) 1 hour prior to the glucose tolerance test. Animals were sacrificed by CO2

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asphyxiation and cervical dislocation.

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Long term treatment with casein hydrolysate

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Animals were administered 100 µl of 100mg/kg body weight casein hydrolysate diluted in

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sterile distilled H2O using a 1 ml syringe and a 18ga (0.7x1.2mm) gavage feeding needle.

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Animals received the treatment every second day via oral gavage for a period of 12 weeks.

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Control mice received 100 µl sterile distilled H2O. Animals were fasted overnight for 16

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hours prior to the experiment. Fasting plasma glucose levels were measured using a

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Medisense Optium Xceed (Abbott, Ireland) glucometer at 0 minutes prior to administering

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each mouse with 2 g/kg body weight of glucose and plasma glucose levels were measured at

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15, 30, 60, 90, 120 minutes. Animals were sacrificed by CO2 asphyxiation and cervical

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dislocation.

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Liver histology

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Liver sections were stored in formalin 10% formaldehyde at room temperature before they

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were embedded in paraffin wax overnight. Liver sections were dehydrated in a series of

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increasing ethanol concentrations: once in 50 % (v/v) for 15 min, twice in 70 % ethanol for

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15 min, twice in 90 % ethanol for 10 min and three times in 100 % ethanol for 15 min.

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Samples were left overnight in 100 % ethanol at 4 °C before cutting at 4 µm. The

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haematoxylin and eosin (H&E) staining process consisted of 10 min at 62 ˚C, 3 x 5 min in

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xylene, 2 x 5 min in 100 % ethanol, 3 min in 95 % ethanol, 3 min in 70% ethanol and 5 min

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in PBS Leica. Sections were placed in haematoxylin (Clin-Tech, Guilford, UK) for 10 min,

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washed in ddH2O and 1 % acid ethanol, and incubated with eosin (Clin-Tech, Guilford, UK)

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for 90 sec. Sections were washed and dehydrated in PBS for 5 min, 70 % ethanol for 3 min,

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95 % ethanol for 3 min, 100 % ethanol for 10 min and in xylene for 3 x 5 min. Slides were

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scanned at 40x magnification using a ScanScope XT Digital slide scanner (Aperio

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Technologies CA, USA), digital images were analysed by k means clustering using image J

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to separate the fat globules from the remainder of the tissue. 6 images of each liver section

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was analysed, the area (µm) of fat in each 40x image of liver was measured. The average of

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the 6 images for each liver section from each animal was calculated and was presented as

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n=1.

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Human study participants and design

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The present study was a randomised, controlled, crossover design conducted according to the

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guidelines laid down in the Declaration of Helsinki and all procedures involving human

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subjects or patients were approved by the University College Dublin Human Ethics Research

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Committee (LS-12-92_BRENNAN). Written, informed consent was obtained from all

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participants. Eligible participants were healthy Caucasian men and women aged between 40-

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65 years with a BMI >25kg/m2 were recruited in the Dublin region by poster and radio

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advertising. Participants were excluded if they were taking hormone replacement therapy

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had a chronic or infectious disease, were pregnant or lactating or had an allergy or intolerance

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to dairy or wheat products.

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Anthropometric measurements were performed including body weight and height to

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calculate BMI (kg/m2), waist circumference, blood pressure and heart rate using an Omron

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M6 Comfort digital automatic blood pressure monitor (Omron Healthcare Europe). A single

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study coordinator was responsible for obtaining the random allocation sequence, enrolment

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and assignment of subjects. Subjects were assigned to treatment or control on their first visit

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using a randomization table. This was method was used to assign subjects to crossover from

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treatment to control, or vice versa, in a non-biased order. Controls and treatments were coded

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as A and B, respectively. The study coordinator was not blinded to controls and treatments,

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which were both plain white powders, however, study subjects were. Individuals were given

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de-identified codes using a random number generating tool (www.randomizer.org). The

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sample size was calculated using data from our unpublished previous studies (AUC for

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glucose curves) with similar primary outcomes and intervention products. Based on these

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data we expected a change in AUC glucose of approximately 80 units. A sample size of 50

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was calculated as sufficient to detect the difference with a level of significance of 0.05 for a

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difference of 80 units. Accounting for a 30% potential dropout rate we aimed to recruit 72

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individuals. Recruited subjects were invited to attend the study centre on two separate

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occasions, at least 7 days apart but no more than 21 days. Subjects fasted for 12 hours prior to

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each visit and were fitted with a peripheral 20-22 gauge cannula (BD Nexiva, Becton

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Dickson, Oxford, UK) before giving fasting blood samples. They then consumed a prescribed

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breakfast containing 74 g carbohydrate (Nutrient breakdown provided in Table S1 in

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supplementary material based upon on pack information) along with a 10 % (w/v) solution

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(100 ml) of casein hydrolysate or a sodium caseinate (intact control protein) in a randomised,

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crossover fashion. Subjects were instructed to consume the meal and beverage within 10

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minutes. The meal comprised 2 slices of white bread toasted with 40 g strawberry jam and

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100 ml of orange juice from concentrate (Table S1, supplementary material, provides the

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nutrient composition of the test meal).

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The casein hydrolysate was produced specifically for this study was scaled up in the GMP

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manufacture facility of Moorepark Limited. As a control, sodium caseinate was provided by

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Kerry Group Plc. Both powders were dissolved to form a 10 %w/v solution using 12 g of

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protein dissolved in 120 ml of mineral water (Ballygowan, Ireland). Dissolution was aided

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with gentle agitation using a handheld blender. Beverages were refrigerated for 6-7 hours

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prior to consumption in order to improve palatability. The point of consumption of the

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protein (immediately following the breakfast meal) was recorded as time point zero (t=0) and

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blood was drawn at time points t = 15, 30, 60, 90 and 120 minutes. Blood was drawn into

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serum separator, EDTA, Lithium Heparin and DPPIV inhibitor tubes (BD Vacutainer).

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Serum samples were allowed to clot at room temperature (RT) for 30 minutes. Serum

300

separator and DPPIV inhibitor tubes were centrifuged at 1300 g for 10 minutes at RT. EDTA

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and Lithium Heparin tubes were centrifuged at 1500 g for 10 minutes at 4 ˚C. All aliquots

302

were frozen immediately and stored at -80 ˚C.

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Biochemical Measurements

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The primary outcome measures were blood glucose and insulin concentrations at six time

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points across the oral glucose tolerance test period of two hours. Secondary outcome

306

measures included c-peptide, Gastric inhibitory polypeptide (GIP), triacylglycerols and non-

307

esterified fatty acids (NEFA) concentrations. All measurements were made in accordance

308

with the manufacturers’ instructions. Plasma samples were analysed for insulin by high

309

sensitivity ELISA (Mercodia, Sweden) and by regular ELISA for c-peptide (Mercodia,

310

Uppsala, Sweden). Plasma samples protected by DPPIV inhibitor were analysed by ELISA

311

for GIP and Glucagon-like peptide-1 (GLP-1) (Merck Millipore, Cork, Ireland). Lithium-

312

heparin serum samples were analysed for glucose, NEFAs and trigylcerides using an Rx

313

Daytona autoanalyser (Randox Laboratories, Co Antrim, UK).

314

Statistical Analyses

315

The results are expressed as mean ± sem. The general linear model procedure under IBM

316

SPSS Statistics 20 was employed. Differences between treatment groups during the two hour

317

post prandial period were tested by repeated-measures analysis of variance using the mixed

318

models application. In each group, differences from baseline were measured using a t-test

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with a Bonferroni post hoc test. In any cases where the data was not normally distributed,

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non-parametric analysis methods were applied. The data is represented in the figures as the

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delta change from baseline and, unless otherwise indicated, the statistics were run on these

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values, rather than raw numbers. P values < 0.05 were considered as significantly different.

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The response of plasma glucose, insulin, c-peptide were calculated as area under the curve

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(AUC) for the change in values from 0 h using GraphPad Prism 5.0 (GraphPad Software, Inc.

325

La Jolla, USA). Paired samples t-tests were used to assess the difference between treatment

326

groups here.

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Characterisation of the Casein Hydrolysate

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The molecular mass distribution profile of the intact and hydrolysed caseinate and its

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associated UF fractions are illustrated in Supplementary Fig. S1A. The unhydrolysed sodium

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caseinate, as expected, consists of relatively large molecular mass proteins, with more than 98

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% of the sample being greater than 10 kDa (Supplementary Fig. S1A). In contrast, the

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hydrolysate UL 291contains 2.2 % of proteinaceous material > 10 kDa (Supplementary Fig.

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S1A). Upon hydrolysis, the proteins were broken down into peptides, resulting in a reduction

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in the molecular mass of the components within the casein hydrolysate. Analysis of the

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casein hydrolysate UF samples showed that the higher molecular weight components were

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retained in the UF membranes resulting in enrichment of lower molecular weight peptides (