Yoshihisa Katsuragi

Green Tea Catechin Consumption Enhances Exercise-Induced Abdominal Fat Loss in Overweight and Obese Adults

This study evaluated the influence of a green tea catechin beverage on body composition and fat distribution in overweight and obese adults during exercise-induced weight loss. Participants (n = 132 with 107 completers) were randomly assigned to receive a beverage containing approximately 625 mg of catechins with 39 mg caffeine or a control beverage (39 mg caffeine, no catechins) for 12 wk. Participants were asked to maintain constant energy intake and engage in >or=180 min/wk moderate intensity exercise, including >or=3 supervised sessions per week. Body composition (dual X-ray absorptiometry), abdominal fat areas (computed tomography), and clinical laboratory tests were measured at baseline and wk 12. There was a trend (P = 0.079) toward greater loss of body weight in the catechin group compared with the control group; least squares mean (95% CI) changes, adjusted for baseline value, age, and sex, were -2.2 (-3.1, -1.3) and -1.0 (-1.9, -0.1) kg, respectively. Percentage changes in fat mass did not differ between the catechin [5.2 (-7.0, -3.4)] and control groups [-3.5 (-5.4, 1.6)] (P = 0.208). However, percentage changes in total abdominal fat area [-7.7 (-11.7, -3.8) vs. -0.3 (-4.4, 3.9); P = 0.013], subcutaneous abdominal fat area [-6.2 (-10.2, -2.2) vs. 0.8 (-3.3, 4.9); P = 0.019], and fasting serum triglycerides (TG) [-11.2 (-18.8, -3.6) vs. 1.9 (-5.9, 9.7); P = 0.023] were greater in the catechin group. These findings suggest that green tea catechin consumption enhances exercise-induced changes in abdominal fat and serum TG.

Basic studies for the practical use of bitterness inhibitors: selective inhibition of bitterness by phospholipids.

AbstractPurpose. We examined the effects of phospholipids such as phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol (PI), and phosphatidic acid (PA) on human taste sensation to various substances. Methods. The effects were evaluated psychophysically using paid volunteers. Results. PA inhibited the bitterness of various substances dissolved in water without affecting sweetness, saltiness, and sourness, although its inhibitory activity was less than that of PA-LG. PI also showed inhibitory activity on bitterness, although its activity was less than PA. A soybean lecithin fraction containing high contents of PA and PI also demonstrated inhibitory activity on the bitterness of various substances. Both the incorporation of either PA or the lecithin fraction into granules containing quinine and the coating of the granules with PA or the fraction effectively inhibited the bitterness of quinine. Conclusions. The lecithin fraction is permitted for use as an additive to drugs and food and can be produced on an industrial scale. It is expected that the lecithin fraction will be used safely as a bitterness inhibitor for practical applications.

Selective Inhibition of Bitter Taste of Various Drugs by Lipoprotein

Previously, we demonstrated that lipoprotein composed of phosphatidic acid (PA) and β-lactoglobulin (LG) selectively and reversibly suppress the frog taste nerve response to bitter substances. In the present study, we examined the effects of various lipoproteins on the taste sensation to various stimuli in humans by a psychophysical method. Among various lipoproteins composed of different of lipids and proteins, the lipoproteins composed of PA and proteins were most effective in suppressing bitter taste. The lipoproteins composed of PA and LG, bovine serum albumin, ovalbumin, α-lactoalbumin or casein similarly suppressed effects on sensation of bitter taste. Using PA-LG, the effects on taste sensation to various stimuli were examined. The bitter taste of all twelve substances examined was inhibited, while saltiness of NaCl and sweetness of sucrose were not inhibited. The inhibition of bitter taste was completely reversible. Masking of the target sites for bitter substances on the taste receptor membranes with PA-LG seems to contribute to the inhibition of bitter taste. Direct binding of the bitter substances to PA-LG in the medium also contributes to the inhibition of bitter taste of certain substances. Among various drugs, basic and hydrophobic substances such as quinine, denatortium and propranolol have low taste thresholds and are said to be the most bitter. PA-LG most effectively suppressed the bitter taste of such substances. PA originates from soybeans and the proteins used except for bovine serum albumin originate from milk or eggs, and hence the lipoproteins can be safely used to mask the bitter taste of drugs.

Brown adipose tissue is involved in diet-induced thermogenesis and whole-body fat utilization in healthy humans

Background/Objectives:Brown adipose tissue (BAT) is a potential therapeutic target against obesity and diabetes through thermogenesis and substrate disposal with cold exposure. The role of BAT in energy metabolism under thermoneutral conditions, however, remains controversial. We assessed the contribution of BAT to energy expenditure (EE), particularly diet-induced thermogenesis (DIT), and substrate utilization in human adults.Methods:In this cross-sectional study, BAT activity was evaluated in 21 men using 18F-fluoro-2-deoxy-D-glucose positron emission tomography combined with computed tomography (18F-FDG-PET/CT) after cold exposure (19 °C). The subjects were divided into BAT-positive (n=13) and BAT-negative (n=8) groups according to the 18F-FDG-PET/CT findings. Twenty-four hour EE, DIT and respiratory quotient were measured using a whole-room indirect calorimeter at 27 °C.Results:Body composition, blood metabolites and 24-h EE did not differ between groups. DIT (%), calculated as DIT divided by total energy intake, however, was significantly higher in the BAT-positive group (BAT-positive: 9.7±2.5%, BAT-negative: 6.5±4.0%, P=0.03). The 24-h respiratory quotient was significantly lower (P=0.03) in the BAT-positive group (0.861±0.027) than in the BAT-negative group (0.889±0.024).Conclusion:DIT and fat utilization were higher in BAT-positive subjects compared to BAT-negative subjects, suggesting that BAT has a physiologic role in energy metabolism.

Coffee polyphenols improve peripheral endothelial function after glucose loading in healthy male adults

Brewed coffee is a widely consumed beverage, and many studies have examined its effects on human health. We investigated the vascular effects of coffee polyphenols (CPPs), hypothesizing that a single ingestion of CPP during glucose loading would improve endothelial function. To test this hypothesis, we conducted a randomized acute clinical intervention study with crossover design and measured reactive hyperemia index (RHI) to assess the acute effects of a 75-g glucose load with CPP in healthy, nondiabetic adult men. Blood glucose and insulin levels were elevated after glucose loading with and without CPP, with no significant differences between treatments. The RHI did not significantly decrease after glucose loading without CPP. With CPP, however, RHI significantly (P < .05) increased over baseline after glucose loading. The difference between treatments was statistically significant (P < .05). No significant changes were observed in an oxidative stress marker after glucose loading with or without CPP. These findings suggest that a single ingestion of CPP improves peripheral endothelial function after glucose loading in healthy subjects.

Receptor mechanisms of bitter substances.

The receptor mechanism of bitter substances was discussed from the following points of views. (a) Both electrostatic and hydrophobic interactions of bitter substances with taste receptor membranes contribute to reception of bitter substances having a positive charge. (b) In the frog, the responses to bitter substances are easily adapted. The presence of Ca ion in the medium prolongs the responses. (c) Bitter substances elicit electrical responses in nongustatory cells such as neuroblastoma cells and olfactory cells, suggesting that bitter substances induce the response by nonreceptor-mediated mechanism. (d) There is also a possibility that receptors for some bitter substances are G-protein coupled. We cloned G-protein coupled receptors from bovine taste tissues. (e) A specific inhibitor of bitter taste has been desired in pharmaceutical and food sciences, but it has not been available. We found that a lipoprotein made of phosphatidic acid and beta-lactoglobulin selectively inhibits the responses to bitter substances in the frog and humans. Binding of the lipoprotein to the receptor sites for bitter substances leads to suppression of the response.

Lipoprotein that selectively inhibits taste nerve responses to bitter substances

The development of a specific inhibitor for bitter taste has been widely required in the fields of taste physiology and pharmaceutical sciences, but no inhibitor has been available. We found that lipoproteins, PA-LG composed of phosphatidic acid (PA) and beta-lactoglobulin (LG) and PA-LA composed of PA and alpha-lactalbumin (LA) reversibly suppressed the responses of the frog glossopharyngeal nerve to the bitter substances. The frog tongue was treated with PA-LG solution for 10 min and then stimulated by a stimulus dissolved in water. The responses to the bitter substances such as quinine hydrochloride, papaverine hydrochloride, caffeine and L-leucine were completely suppressed by PA-LG, while those to the salt type bitter substances such as CsCl, MgCl2 and tetraethylammonium chloride were not suppressed. The responses to NaCl, galactose, acetic acid and L-alanine were unchanged or only slightly increased. The results suggested that binding of PA-LG to the hydrophobic region of the receptor membranes leads to suppression of the responses to the bitter substances. It was pointed out that PA-LG is useful not only for elucidating the receptor mechanisms of bitter substances, but also can be safely used to mask the bitter taste of foods and drugs, since PA, LG and LA are prepared from foods (soybean and milk).

Coffee bean polyphenols ameliorate postprandial endothelial dysfunction in healthy male adults

Abstract To reveal the effect of coffee bean polyphenols (CBPs) on blood vessels, this study aimed to investigate the effect of CBPs on acute postprandial endothelial dysfunction. Thirteen healthy non-diabetic men (mean age, 44.9 ± 1.4 years) consumed a test beverage (active: containing CBPs, placebo: no CBPs) before a 554-kcal test meal containing 14 g of protein, 30 g of fat and 58 g of carbohydrates. Then, a crossover analysis was performed to investigate the time-dependent changes in flow-mediated dilation (FMD) in the brachial artery. In the active group, the postprandial impairment of FMD was significantly improved, the two-hour postprandial nitric oxide metabolite levels were significantly increased and the six-hour postprandial urinary 8-epi-prostaglandin F2α levels were significantly reduced compared to the placebo group. The test meal increased the levels of blood glucose, insulin and triglycerides in both groups with no significant intergroup differences. These findings indicate that CBPs intake ameliorates postprandial endothelial dysfunction in healthy men.

Fat utilization in healthy subjects consuming diacylglycerol oil diet: dietary and whole body fat oxidation.

Several studies in animals and humans have reported beneficial effects of diacylglycerol (DAG) on lipid and energy metabolism. We assessed the effect of DAG versus triacylglycerol (TAG) treatment on total energy expenditure (TEE), total fat oxidation (Fox) and respiratory quotient (RQ), and measured the oxidation rate of each oil using a respiratory chamber and the 13C-stable isotope. Eleven healthy subjects participated in a double-blind, randomized crossover study. Subjects consumed an energy maintenance diet consisting of 55% of total calories from carbohydrate, 15% from protein and 30% from fat during both the 3-day pre-chamber and 36-h chamber period. Fifty percent of the fat was test oil, containing either DAG oil or TAG oil. The oxidation rate of ingested test oils was determined by monitoring 13CO2 excretion in the breath from 13C-labeled diolein or 13C-labeled triolein. There were no significant differences in TEE, RQ and total Fox between the DAG and TAG treatment in the overall analysis. In the subgroup analysis, DAG treatment decreased RQ significantly in subjects with a high fat ratio (HFR) compared to TAG treatment. In addition, ingested diolein oxidation in DAG treatment was significantly faster than triolein oxidation in TAG treatment in the HFR group. Enhanced fat utilization with DAG treatment and rapid oxidation of ingested DAG may, at least in part, explain the greater loss of body weight and body fat related to DAG consumption found in the weight-loss studies.

Greater fat oxidation with diacylglycerol oil consumption for 14 days compared with triacylglycerol oil consumption in overweight men and women.

Background:Several studies have reported increased fat oxidation with diacylglycerol (DAG) oil consumption. However, the effects of long-term DAG oil consumption on energy metabolism remain to be investigated.Objective:The objective of this study was to compare the effects of 14 days of either DAG or triacylglycerol (TAG) oil consumption on substrate oxidation, energy expenditure (EE) and dietary fat oxidation.Design:Eight males and six females participated in this randomized, double-blind, crossover feeding study. Each patient consumed the 14-day controlled test diet containing either 10 g day−1 of DAG or TAG oil for acclimatization before a respiratory chamber measurement, followed by a 2-week washout period between diet treatments. Substrate oxidation and EE were measured in the respiratory chamber at the end of each dietary treatment. The patients consumed test oil as 15% of total caloric intake in the respiratory chamber (mean test oil intake was 36.1±6.6 g day−1).Results:Twenty-four hour fat oxidation was significantly greater with 14 days of DAG oil consumption compared with TAG oil consumption (78.6±19.6 and 72.6±14.9 g day−1, respectively, P<0.05). There were no differences in body weight or body composition between diet treatments. Dietary fat oxidation was determined using the recovery rate of 13CO2 in breath, and was significantly enhanced with DAG oil consumption compared with TAG oil consumption, measured over 22 h after ingestion of 13C-labelled triolein. Resting metabolic rate (RMR) was significantly greater with DAG oil consumption compared with TAG oil consumption (1766±337 and 1680±316 kcal day−1, respectively, P<0.05).Conclusion:Consumption of DAG oil for 14 days stimulates both fat oxidation and RMR compared with TAG oil consumption, which may explain the greater loss of body weight and body fat with DAG oil consumption that has been observed in weight-loss studies.