Roasted Barley Extract (Mugicha) Containing Cyclo(D-Phe-L-Pro) Prevents a Decrease in Skin Temperature in Cold Conditions: A Randomized, Double-Blind, Placebo-Controlled, Crossover Study.

Roasted barley extract (RBE) is a traditional Japanese beverage. Previously, we reported the effects of RBE containing cyclo(d-Phe-l-Pro) on blood flow in animals and humans and investigated rapid skin temperature recovery from cold-water immersion in women. The present randomized, double-blind study investigated the effects of RBE containing cyclo(d-Phe-l-Pro) on men's and women's skin temperature in excessively air-cooled conditions. Participants felt cold in the test room (25.5±0.5ºC). They ingested an RBE or placebo beverage and remained in the air-conditioned room for 100 min. Skin temperature of the left foot was measured every 5 min using infrared thermography. We evaluated effect of RBE administration by paired t-test. The skin temperature of the RBE group remained higher than that of the placebo group. The skin temperature changes 100 min after RBE or placebo ingestion were -3.67±1.14ºC and -4.59±0.89ºC, respectively in all participants. We also did subclass analysis focusing on men or women. In a previous study, RBE efficacy for skin temperature in men was not clearly demonstrated. RBE consumption was also effective not only in female participants but also in male participants. The skin temperature changes 100 min after RBE or placebo ingestion were -3.65±0.64ºC and -4.55±0.32ºC, respectively in male participants. Therefore, RBE containing cyclo(d-Phe-l-Pro) prevented skin temperature decreases in excessively air-cooled conditions in both men and women.

Roasted Barley Extract (Mugi-cha) Containing Cyclo(d-Phe-l-Pro) Prevents Lowering of the Cutaneous Blood Flow and Skin Temperature under Air Conditioning: A Randomized, Double-Blind, Placebo-Controlled, Crossover Study.

Roasted barley extract (RBE), also known as mugi-cha, is a well-known healthy non-caffeinated beverage, and its health functionality has been widely reported. Our previous clinical study showed that RBE affects the cutaneous blood flow and skin temperature after cold-water immersion and that cyclo(d-Phe-l-Pro) is responsible for its effect. In this study, we investigated whether cyclo(d-Phe-l-Pro)-containing RBE prevents the decrease in the cutaneous blood flow and skin temperature. Subjects remained in the air-conditioned room while ingesting RBE or a placebo. We measured the cutaneous blood flow and skin temperature. We evaluated the effect of RBE administration by two-way repeated measures analysis of variance. A total of 15 subjects were enrolled. The change in cutaneous blood flow in the RBE and placebo groups was -0.79 ± 0.38 and -2.03 ± 0.35 mL min-1 100 g-1, respectively ( p value of 0.041). The change in the skin temperature in the RBE and placebo groups was -1.85 ± 0.35 and -3.02 ± 0.30 °C, respectively ( p value of <0.001). We also did subclass analysis with cold-feeling subjects. For the seven subjects who had cold sensation, the change in the cutaneous blood flow in the RBE and placebo groups was -0.48 ± 0.58 and -2.56 ± 0.48 mL min-1 100 g-1, respectively ( p value of 0.008). The change in the skin temperature in the RBE and placebo groups was -1.46 ± 0.74 and -2.89 ± 0.39 °C, respectively ( p value of 0.009). Thus, RBE containing cyclo(d-Phe-l-Pro) prevents the decrease in the cutaneous blood flow and skin temperature under air conditioning.

Roasted Barley Extract Affects Blood Flow in the Rat Tail and Increases Cutaneous Blood Flow and Skin Temperature in Humans.

Roasted barley extract (RBE, "Mugicha") is a traditional Japanese beverage reported to improve blood viscosity and affect food functionality. RBE is suggested to contain 2,5-diketopiperazines, which are the functional component with neuroprotective and immunostimulatory effects that are produced in food through roasting. In this study, we investigated the effects of RBE on blood circulation, both clinically and in rats. At first, we confirmed five 2,5-diketopiperazine derivatives in RBE by LC-MS analysis. Secondarily, we revealed that RBE affects blood flow in the rat tail and compared the efficacy on rat tail blood flow among five 2,5-diketopiperazines in RBE. Especially, cyclo(d-Phe-l-Pro) was the most effective in increasing blood flow in the rat tail. We also researched the mechanism of cyclo(d-Phe-l-Pro) with rat aorta study. As a result, we confirmed that cyclo(d-Phe-l-Pro) has an effect on vasodilatation through the release of nitric oxide in the vascular endothelium. Finally, we also confirmed that RBE affects cutaneous blood flow and increases skin temperature in humans.

2-Ethylpyrazine Induces Vasodilatation by Releasing Nitric Oxide in the Endothelium.

Oxygen transportation and regulation of some physiological processes are facilitated by blood flow. Furthermore, blood flow is regulated by various factors such as nitric oxide (NO) and the autonomic nerve system. In modern life, many people suffer from chilliness (hiesho) because of mental stress and an excessive use air-conditioning systems, which induces vasoconstriction in the peripheral skin. In this study, we focused on pyrazine derivatives, particularly compounds that are used as food flavoring materials, and investigated their effects on vascular function and blood flow. We examined the vasodilatory effect of pyrazine derivatives in the rat thoracic aorta and found 2-ethylpyrazine (2-EP) to be the most active pyrazine compound. Additionally, we found that 2-EP induces vasodilatation through the activities of endothelium-derived relaxing factors. 2-EP activates NO synthesis through the effect of endothelial NO synthase in the endothelium. As a result, cyclic GMP levels rise in smooth muscle cells and vasodilatation is induced. We also confirmed that 2-EP increases peripheral blood flow in rats. From these results, we concluded that 2-EP induces vasodilatation by inducing the release of NO and increasing peripheral blood flow.

Isohumulones, the bitter component of beer, improve hyperglycemia and decrease body fat in Japanese subjects with prediabetes.

BACKGROUND & AIMS: A recent study reported that isohumulones, the bitter component of beer, activate peroxisome proliferator-activated receptor alpha (PPARalpha) and PPARgamma in vitro and decrease plasma glucose and lipid levels in diabetic mice. This study was to investigate the efficacy and safety of isohumulones for subjects with prediabetes. METHODS: Ninety-four subjects with prediabetes were randomly divided into four groups. A 12-week double-blind dose-finding study was performed in which subjects ingested placebo capsules or test capsules containing 16 mg, 32 mg or 48 mg of isohumulones per day. RESULT: After treatment, fasting blood glucose was decreased in the 32 mg and 48 mg groups after 4 weeks, but did not change in the placebo group. HbA1c was also significantly decreased after 4 weeks in the 16 mg group and after 8 weeks in the 32 mg and 48 mg groups. Body mass index (BMI) was significantly decreased in the 48 mg group as compared with the placebo group at 12 weeks. The decrease in total fat area was also significantly greater in the 48 mg group than in the placebo group at 12 weeks. CONCLUSION: The present study suggests that ingestion of isohumulones has beneficial effects in diabetes and obesity.