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Food and Beverage Chemistry/Biochemistry
Roasted barley extract (mugi-cha) containing cyclo (D-Phe-L-Pro) prevents lowering of cutaneous blood flow and skin temperature under air-conditioning – A randomized, double-blind, placebo-controlled, crossover study Hiroshi Ashigai, Mai Mizutani, Yoshimasa Taniguchi, Yasuko Matsukura, Keiko Nakashima, Emiko Ikeshima, and Hiroaki Yajima J. Agric. Food Chem., Just Accepted Manuscript • DOI: 10.1021/acs.jafc.8b02485 • Publication Date (Web): 24 May 2018 Downloaded from http://pubs.acs.org on May 24, 2018
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Title
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Roasted barley extract (mugi-cha) containing cyclo (D-Phe-L-Pro) prevents lowering of
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cutaneous blood flow and skin temperature under air-conditioning – A randomized,
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double-blind, placebo-controlled, crossover study -
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Authors
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Hiroshi Ashigai, Mai Mizutani, Yoshimasa Taniguchi, Yasuko Matsukura, Keiko
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Nakashima, Emiko Ikeshima, Hiroaki Yajima
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†
Corresponding author: Hiroshi Ashigai
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Kirin Co. Ltd., Research Laboratories for Health Science and Food Technologies,
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1-17-5, Namamugi, Tsurumi-ku, Yokohama 230-8628 Japan
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Tel: +81-90-1930-9950,
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Fax: +81-45-500-8311,
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E-mail:
[email protected] 1
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Abstract
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Roasted barley extract (RBE), also known as mugi-cha, is a well-known healthy
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non-caffeinated beverage and its health functionality has been widely reported. Our
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previous clinical study showed that RBE affects cutaneous blood flow and skin
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temperature after cold water immersion, and that cyclo (D-Phe-L-Pro) is responsible for
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its effect. In this study, we investigated whether cyclo (D-Phe-L-Pro)-containing RBE
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prevents the decrease in cutaneous blood flow and skin temperature. Subjects remained
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in the air-conditioned room while ingesting RBE or a placebo. We measured cutaneous
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blood flow and skin temperature. We evaluated effect of RBE administration by
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two-way repeated measures ANOVA. Fifteen subjects were enrolled. The change in
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cutaneous blood flow in the RBE group and placebo group was −0.79 ± 0.38
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(ml/min/100 g) and −2.03 ± 0.35 (ml/min/100 g), p-value was 0.041. The change in skin
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temperature in the RBE group and placebo group was −1.85 ± 0.35°C and −3.02 ±
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0.30°C, p-value was < 0.001.
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We also did subclass analysis with cold feeling subjects. Seven subjects who had cold
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sensation, the change in cutaneous blood flow in the RBE group and placebo group was
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−0.48 ± 0.58 (ml/min/100 g) and −2.56 ± 0.48 (ml/min/100 g), p-value was 0.008, The
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change in skin temperature in the RBE group and placebo group was −1.46 ± 0.74°C
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and −2.89 ± 0.39°C, respectively. p-value was 0.009.
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Thus, RBE containing cyclo (D-Phe-L-Pro) prevents the decrease in cutaneous blood
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flow and skin temperature under air conditioning.
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Keywords
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roasted barley extract / cyclo (D-Phe-L-Pro) / cutaneous blood flow / skin temperature /
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air conditioning
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Introduction
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Roasted barley extract (RBE), or mugi-cha, is a popular traditional beverage in Japan.1
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RBE is also well-known as a healthy caffeine-free beverage. many Japanese people, 3
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children, infants as well as adults, drink RBE because RBE is uncaffeinated and low
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calorie. It is normally made with roasted barley, which has a slightly bitter taste. RBE
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lowers blood glucose and has an antioxidant activity.2,3 We have reported that RBE
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containing cyclo (D-Phe-L-Pro) affects cutaneous blood flow and skin temperature after
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cold water immersion.1
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2,5-Diketopyperazine is a cyclic peptide that is produced by roasting food
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ingredients.4-10 RBE is made by roasting barley. Thus, RBE contained various
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2,5-diketopyperazines, which is not contained unroasted barley extract. Especially,
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cyclo (D-Phe-L-Pro) is the most quantity in RBE, and the most effective for blood flow
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circulation.1 We have previously reported that cyclo (D-Phe-L-Pro) is the key chemical
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in RBE that improves blood circulation, and that it affects vasodilatation through NO
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releasing in the endothelium.1
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Cold sensation (hiesho) is known as blood stasis (Oketsu) in traditional Chinese
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medicine.11,12 It decreases quality of life and can be related to various vascular diseases
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such as hypertension and arteriosclerosis.13,14 Cold sensation is caused by an imbalance
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of the autonomic nerve system, which causes vasoconstriction and lowers cutaneous
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blood flow.15,16 Blood flow plays a role in controlling body temperature.17 Thus,
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decreased skin temperature leads to a decline in cutaneous blood flow.18
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Air-conditioning systems are increasingly used to control the room temperature. Public
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transportation systems and workplaces sometimes make excessive use of their
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air-conditioning systems. Thus, many people, especially women, experience cold
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sensation caused by excessive air-cooling.19,20 Ameliorating cold sensation in situations
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with excessive air-conditioning is important for quality of life. Consumption of
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functional beverages is one safety way to ameliorate cold sensation in daily life. Our
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research question was that RBE with cyclo (D-Phe-L-Pro) prevents lowering of
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cutaneous blood flow and skin temperature under air-conditioning.
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In this study, we demonstrated the effect of RBE with cyclo (D-Phe-L-Pro) for
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increasing cutaneous blood flow and skin temperature in air-conditioned rooms, using a
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randomized, double-blind, placebo-controlled, crossover study design. We also
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investigated whether cold sensation severity is related to RBE effect.
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Materials and Methods
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Chemical
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Cyclo (D-Phe-L-Pro) was purchased from Peptide Institute, Inc. (Osaka, Japan).
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Its’ purity is >99% (w/w). Formic acid and acetonitrile were purchased from Wako
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FUJIFILM Wako Pure Chemical Corporation (Osaka, Japan).
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Ethics
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This clinical study followed the ethical standards of the Helsinki Declaration of 1964, as
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modified by subsequent revisions and the Ethical Guidelines for Epidemiological
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Research of the Ministry of Education, Culture, Science, and Technology and the
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Ministry of Health, Labor and Welfare of Japan, and the experimental protocol (protocol
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no. 33) was approved by the Institutional Review Board of Kirin Group Japan
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Integrated Beverages, Kirin Company Ltd. This study was registered with the UMIN
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Clinical Trials Registry as UMIN000032521 and was conducted in compliance with the 6
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protocol as registered. This clinical trial was performed from September 28th, 2012 to
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October 26th, 2012.
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Participants
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All subjects were healthy Japanese males and females; they provided informed consent
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complying with the Helsinki Declaration. The exclusion criteria were as follows: under
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treatment; possible onset of allergy symptoms; any history of serious disease (e.g., heart
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disease, diabetes, kidney disease, liver disease); and possible pregnancy, pregnancy, or
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lactation.
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Target sample size
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Based on a preliminary human study, RBE (with 250 mg Cyclo (D-Phe-L-Pro)) was
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expected to be higher cutaneous blood flow by 0.15 (ml/min/100 g) with a standard
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deviation of 0.27 compared to the placebo group. Setting the significance level at 5% by
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an unpaired Student's t-test and the power at 0.90, the number of subjects required per 7
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group was estimated to be 15.
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Test beverage
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Roasted barley was purchased from the MC Foods Company (Tokyo, Japan). RBE was
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prepared as follows: roasted barley (100 g) was added to boiling water (1000 g) and
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steeped for 30 min, and diluted with 4000 g water. RBE was divided into aliquots of
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250 g. For placebo preparation, we used food coloring into water so that the two
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beverages would not differ in appearance to ensure that the two beverages were similar
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in taste. The components of RBE and the placebo are shown in Table 1. The RBE drink
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contained 250 µg cyclo (D-Phe-L-Pro)/250 mL bottle.
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Measurement of cyclo (D-Phe-L-Pro) levels
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Aliquots (1 µL) of the extracts were analyzed by liquid chromatography-mass
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spectrometry (LC-MS) using a Develosil column (C30-UG-3; 2.0 × 250 mm;
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Phenomenex, Torrance, CA, USA) coupled to a 4000 QTRAP LC-MS system (AB 8
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Sciex, Tokyo, Japan) in selected-ion monitoring (SIM) mode. The mobile phase
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consisted of formic acid (0.1% in water) and acetonitrile, and was set at a flow rate of
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0.2 mL/min. The analysis was started with 10% acetonitrile for 10 min. Next, the
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acetonitrile content was increased to 30% within 30 min, increased to 100% within 10
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min, and then held at 100% for 10 min. The mass spectrometry was performed in
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positive electrospray ionization mode with a quadrupole mass spectrometer with a
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ionspray voltage of 5.5 kV. The desolvation temperature was 650°C. Cyclo
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(D-Phe-L-Pro) was detected by measuring the corresponding mass traces in SIM mode
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by setting [M+H]+. Peaks at 245 (m/z) indicated the presence of cyclo (L-Pro-D-Phe).
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Study design
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This was a randomized, double-blind, placebo-controlled, crossover study. The site
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investigator enrolled the participants. Participants were divided into two groups by
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stratified randomization by the assigning controller, and each group was assigned either
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the RBE or placebo beverage before the first trial period. The assigning controller kept
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the assignment list in a sealed container until the trial was complete. Participants,
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investigators, and any persons concerned with the study, excluding the assigning
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controller, remained blinded. Participants were asked to drink the RBE beverage or
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placebo beverage on experimental day.
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During the test period, participants were asked to refrain from ingesting
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pharmaceuticals containing caffeine or vitamin K. On the one day before the experiment,
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they asked to refrain from alcoholic drinking excessively; exercising vigorously;
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drinking beverages or eating foods containing ingredients known to affect blood flow.
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On the experimental day, they were asked to refrain from smoking.
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Cold sensation questionnaire
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Cold sensation used Terasawa’s cold feeling questionnaire.20
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Measurement of cutaneous blood flow and skin temperature
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On the day of the experiment, all subjects were asked to wear thin clothing, the same 10
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clothing they would wear on the alternative experimental day. The conditions in the test
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room were as follows: the temperature was 25.5 ± 0.5°C, the humidity was 52.5 ± 7.5%,
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and air flow was < 0.1 m/s. There was no day other than set temperature between testing
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day. After entering the room, subjects were allowed to acclimate to the test room
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conditions for 30 min. Before intake of beverages, we measured cutaneous blood flow
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and skin temperature (pre-intake data, 0 min). Subjects sat in chairs without moving.11
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Then subjects removed their socks and ingested their beverages. The beverages
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temperature was 25°C for adjusting beverages temperature same as room temperature.
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We used the instep of the left foot for cutaneous blood flow and skin temperature
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measurements. Cutaneous blood flow and skin temperature were measured at intervals
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of 5 min for 90 min.21 Cutaneous blood flow measurement was performed using a Laser
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Doppler blood perfusion imager (ALF-21, Advance Company, Tokyo, Japan). Analog
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signals were converted to digital signals using an A/D converter (Power-Lab; AD
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Instruments, Dunedin, New Zealand). Skin temperature was estimated using an Infrared
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Thermography H2640 (Nippon Avionics Company, Tokyo, Japan). Fig. 1 shows a
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schematic representation of the study. 11
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Statistical analysis
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We evaluated value change from 0min for skin blood flow and temperature. Results are
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presented as mean ± standard deviation of the mean, determined using the statistical
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software Ekuseru-Toukei 2010 (Social Survey Research Information Co., Ltd., Tokyo,
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Japan). We evaluated skewness and kurtosis. Significant differences in cutaneous blood
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flow or skin temperature between the RBE and placebo groups were estimated using
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two-way, repeated measures ANOVA (p < 0.05).
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Results
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Participants
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Fifteen individuals were evaluated for eligibility to participate and 15 healthy adults (7
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males and 8 females) were enrolled. Subject background is shown on Table 2. Fig. 2
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shows a flow diagram of the study from assessment to final analysis. No participants
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dropped out of the study, and all participated in the experiment for effect and safety 12
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evaluation. Based on the criteria of cold sensation, as assessed by Terasawa’s
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questionnaire, we divided the participants into two groups: feeling cold sensation (n =
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7) or not feeling cold sensation (n = 8).
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Cutaneous blood flow measurement
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Cutaneous blood flow in the placebo group reduced compared to that at 0 min. In the
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RBE group, the change in cutaneous blood flow was greater than that in the placebo
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group, for all participants (Fig. 3). In subjects feeling cold sensation, the change in
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cutaneous blood flow was significantly greater in the RBE group than in the placebo
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group (Fig. 4 (a)). In subjects not feeling cold sensation, the change in cutaneous blood
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flow was slightly greater in the RBE group than in the placebo group, but the difference
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was not significant (Fig. 4 (b)).
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Skin temperature
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Skin temperature of participants in the placebo group decreased compared to that at 0 13
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min. The change in skin temperature was greater in the RBE group than in the placebo
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group, in all participants (Fig. 5). In particular, it was significantly greater than that in
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the placebo group (Fig. 5). In subjects feeling cold sensation, the change in skin
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temperature was significantly greater in the RBE group than in the placebo group (Fig.
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6 (a)). In subjects not feeling cold sensation, the change in skin temperature was
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significantly greater in those who ingested RBE than in those who ingested the placebo
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(Fig. 6 (b)).
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Safety endpoints
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No adverse events occurred during the study.
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Discussion
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We found that RBE containing cyclo (D-Phe-L-Pro) prevents lowering of cutaneous
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blood flow and skin temperature under air-conditioning.
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Cold sensation (hiesho) is one of severe malaise in traditional Chinese medicine.20 It is 14
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considered a pre-symptom of severe diseases such as insomnia and dysautonomia.22,23
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To induce cold sensation in the test subjects, we set the test room conditions to cold and
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requested that subjects not wear heavy clothing. In the placebo group, cutaneous blood
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flow and skin temperature decreased compared to before the start of the experiment (Fig.
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3,5). Based on these results, we set the test room conditions to moderately cold. It leads
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to vasoconstriction in peripheral skin and a decline of cutaneous blood flow.We
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observed that intake of RBE maintained cutaneous blood flow and skin temperature
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compared to the placebo in an air-conditioned room (Fig. 3,5). In a previous report, we
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noted that RBE showed effect for maintaining cutaneous blood flow and skin
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temperature with cold water immersion.1 This study revealed that RBE shows effect for
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maintaining cutaneous blood flow and skin temperature in an air-conditioned room. We
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hypothesized that RBE’s effect for maintaining blood flow is not restricted to situations
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of acute cold sensation (cold water immersion) and can affect cutaneous blood flow and
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skin temperature in situations of chronic cold sensation (air-conditioning). In our
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previous report, we also reported that cyclo (D-Phe-L-Pro) is the key chemical for RBE
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effect of blood flow.1 We revealed that blood flow change of RBE containing 30 mg 15
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cyclo (D-Phe-L-Pro) is similar to blood flow change of 30 mg cyclo (D-Phe-L-Pro), and
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30 mg cyclo (D-Phe-L-Pro) affects vasodilatation through NO production in the
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endothelium.1 Based on this evidence, we conclude that air-conditioning induces
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vasoconstriction leading to a lower cutaneous blood flow, and that RBE, especially
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cyclo (D-Phe-L-Pro), induces vasodilatation to maintain cutaneous blood flow.
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RBE-ingesting participants maintained their skin temperature compared to participants
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who received a placebo.
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Nitrate supplementation induces reflex cutaneous vasodilatation in heat-stressed healthy
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human24,25. On the other hand, nitrate does not response skin blood flow from cold
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water immersion in subject who have cold sensitivity26. Comparing to these evidences,
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we firstly demonstrated nitrate supplementation response to skin blood flow and skin
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temperature in subject who have cold sensitivity. Cooling method was differnt between
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our experiment and previous report. We think that cold water immersion induced strong
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vasodilatation compared to air-cooling room. Thus, previous report was not detected
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nitrate supplementation effect for skin blood flow.
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In the subclass analysis according to cold sensation, RBE had a stronger effect on
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cutaneous blood flow in subjects with cold sensation than in those without cold
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sensation (Fig. 4 (a), (b)). Comparing the change in cutaneous blood flow in subjects
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who received the placebo, subjects feeling cold sensation tended to show a decline in
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blood flow compared to subjects not feeling cold sensation (Fig. 4 (a), (b)). However,
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the change in skin temperature was similar between subjects with or without cold
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sensation (Fig. 6 (a), (b)). In this experiment, we exposed all subjects to
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air-conditioning. We assume that our intervention had the same effect on skin
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temperature for all subjects, but the effect of declining skin temperature on cutaneous
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blood flow was different between subjects with or without cold sensation. In general,
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dysfunction of blood flow causes cold sensation.27,28 Thus, we believed that cutaneous
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blood flow of subjects with cold sensation tended to be affected by room temperature.
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This does not contradict the concept of cold sensation (Hiesho).20 From these results,
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we assumed that subjects with cold sensation have dysfunctional blood circulation
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compared to subjects without cold sensation. Thus, the effects of air-conditioning
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(declining cutaneous blood flow) were stronger for subjects with cold sensation. We 17
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conclude that RBE’s effect was easily detected in subjects with cold sensation.
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In our previous study, we reported that cyclo (D-Phe-L-Pro) and RBE with cyclo
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(D-Phe-L-Pro) affect vasodilatation and increase blood flow in the tails of rats. Thus,
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we assume that that the effect of RBE for increasing blood flow in this air-conditioned
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room was also mediated by vasodilatation induced by cyclo (D-Phe-L-Pro).
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Hesperidin has been reported to have an effect on vasodilatation through autonomic
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nervous system.21 It also increased skin temperature and improved “hiesho” symptoms
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in a clinical study.21 These reports also support our discussion. Generally, cutaneous
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blood flow and skin temperature are related to cold sensation (Hiesyo).20,24,25 RBE
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containing cyclo (D-Phe-L-Pro) might affect cold sensation.
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This study has several limitations, such as that the subjects in this experiment were all
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Japanese. This limitation could be addressed by performing similar studies on subjects
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of different ancestry, and we hope that clinical studies of RBE will be performed in
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other countries. The tastes difference between test beverages, was one of the limitation
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of this study. In our experiment, the number of subjects was limited number, we will
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need larger clinical trial for more adequately powered. Number of subject especially
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with cold sensation for sub-analysis is small, was another one of the limitation of this 18
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study.
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In conclusion, RBE containing cyclo (D-Phe-L-Pro) prevents lowering of cutaneous
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blood flow and skin temperature under cold sensation conditions in humans, and RBE
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has a stronger effect on subjects who experience cold sensation.
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Non-standard abbreviations: roasted barley extract: RBE,
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Acknowledgments
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We would like to thank Kyoko Kato, Rie Sano, and Guanying Wang for valuable
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discussions and technical support.
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Conflict of interest
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We certify that there is no conflict of interest with any financial organization regarding
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the material discussed in the manuscript. This study was founded by Kirin company
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Ltd.
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Table 1 Nutrient Components of Test Beverages
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Table 2 Subject background
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List of figure caption
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Fig. 1 Schematic representation of intervention.
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Subject was acclimatized with test room condition for 30 min. Before intake of test
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beverage, we measured subject skin blood flow and skin temperature. After drinking
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test beverage, subject had to keep their body position same (not moving), and we
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measured their skin blood flow and skin temperature every 5 min for 90 min.
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Fig. 2 Flow diagram of the progress through the study.
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Fig. 3 skin blood flow change on intaking roasted barley extract (RBE) with cyclo
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(D-Phe-L-Pro).
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administration was statistically significant by two-way repeated measurement ANOVA
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(p