Tomonori Nagao

A Green Tea Extract High in Catechins Reduces Body Fat and Cardiovascular Risks in Humans

Objective: The body fat reducing effect and reduction of risks for cardiovascular disease by a green tea extract (GTE) high in catechins was investigated in humans with typical lifestyles.

Double-Blind Controlled Study on the Effects of Dietary Diacylglycerol on Postprandial Serum and Chylomicron Triacylglycerol Responses in Healthy Humans

Objective: The effects of dietary diacylglycerol (DG) on postprandial lipemia in healthy humans were investigated. Methods: Forty normolipidemic male volunteers ingested fat emulsions containing either DG oil or triacylglycerol (TG) oil, at different doses: 10 g (n = 13), 20 g (n = 10) and 44 g (n = 17). Two test emulsions were given at seven-days intervals in random order. Fatty acid compositions of the test oils had been adjusted to be equal. Fasting and postprandial serum lipid concentrations in each group and plasma lipoprotein lipids in the 20 g-fat ingestion group were measured during the postprandial intervals. Results: When DG emulsion was ingested, serum TG concentrations were significantly lower (p < 0.05) in the late postprandial phase, i.e., 4 hours, 6 hours as compared to the TG emulsion. The magnitude of postprandial lipemia (the area bounded by the curve above the fasting concentration) after ingestion of 44 g-DG emulsion was significantly less than that of 44 g-TG emulsion (6.54 ± 5.12 and 8.45 ± 7.54 mmol · h/L, mean ± SD, respectively). Chylomicron TG, cholesterol, and phospholipid concentrations at 4 hours after ingestion of DG emulsion were significantly lower (p < 0.05) than those after the ingestion of TG emulsion at the same time point. No marked differences were observed for VLDL, LDL and HDL lipids between the test emulsions. Conclusion: In the usual range of fat intake (10–44 g), postprandial response after ingestion of DG emulsion was significantly less than that after ingestion of TG emulsion in healthy human subjects.

A Catechin-rich Beverage Improves Obesity and Blood Glucose Control in Patients With Type 2 Diabetes

We investigated the effects of continuous ingestion of a catechin‐rich beverage in patients with type 2 diabetes who were not receiving insulin (Ins) therapy in a double‐blind controlled study. The participants ingested green tea containing either 582.8 mg of catechins (catechin group; n = 23) or 96.3 mg of catechins (control group; n = 20) per day for 12 weeks. At week 12, the decrease in waist circumference was significantly greater in the catechin group than in the control group. Adiponectin, which is negatively correlated with visceral adiposity, increased significantly only in the catechin group. Although the increase in Ins at week 12 was significantly greater in the catechin group than in the control group, no apparent difference was noted between the two groups in glucose and hemoglobin A1c. In patients treated with insulinotropic agents, the increase in Ins at week 12 was significantly greater in the catechin group than in the control group. This significant increase in Ins levels was observed only in the catechin group. In the catechin group receiving other treatments, Ins levels remained unchanged. In addition, in patients treated with insulinotropic agents, the decrease in hemoglobin A1c at week 12 was significantly greater in the catechin group than in the control group. These results suggest that a catechin‐rich beverage might have several therapeutic uses: in the prevention of obesity; in the recovery of Ins‐secretory ability; and, as a way to maintain low hemoglobin A1c levels in type 2 diabetic patients who do not yet require Ins therapy.

Energy value and digestibility of dietary oil containing mainly 1,3-diacylglycerol are similar to those of triacylglycerol.

Diacylglycerol (DAG) is a component of various vegetable oils. Approximately 70% of the DAG in edible oils are in the configuration of 1,3-DAG. We recently showed that long-term ingestion of dietary oil containing mainly 1,3-DAG reduces body fat accumulation in humans as compared to triacylglycerol (TAG) oil with a similar fatty acid composition. As the first step to elucidate the mechanism for this result, we examined the difference in the bioavailabilities of both oils by measuring food energy values and digestibilities in rats. Energy values of the DAG oil and the TAG oil, measured by bomb calorimeter, were 38.9 and 39.6 kJ/g, respectively. Apparent digestibility expressed according to the formula: (absorbed) x (ingested)−1x100=(ingested—excreted in feces)x(ingested)−1x100 for the DAG oil and the TAG oil were 96.3±0.4 and 96.3±0.3% (mean±SEM), respectively. The similarity in the bioavailabilities of both oils supports the hypothesis that the reduced fat accumulation by dietary DAG is caused by the different metabolic fates after the absorption into the gastrointestinal epithelial cells.

Catechin safely improved higher levels of fatness, blood pressure, and cholesterol in children.

Objective: The purpose of this study was to evaluate the effects of a catechin‐rich beverage on body fat and cardiovascular disease risk factors in obese children and to verify the safety of its use.

Dietary diacylglycerol suppresses high fat diet-induced hepatic fat accumulation and microsomal triacylglycerol transfer protein activity in rats.

We have recently shown that the long-term ingestion of dietary diacylglycerol (DAG) mainly containing 1,3-isoform reduces body fat accumulation in humans as compared to triacylglycerol (TAG) with the same fatty acid composition. The fat reduction in this human experiment was most pronounced in visceral fat and hepatic fat. Recent animal studies have also indicated that dietary DAG induces alteration of lipid metabolism in the rat liver. In the present study, the dietary effects of DAG on high fat diet-induced hepatic fat accumulation and hepatic microsomal triglyceride transfer protein (MTP) activity were examined in comparison with those of TAG diet in rats. When the TAG oil content was increased from 10 to 30 g/100 g diet, hepatic TAG concentration, hepatic MTP activity and MTP large subunit mRNA levels were significantly increased after 21 days. However, when the dietary TAG oil (30 g/100 g diet) was replaced with the same concentration of DAG oil with the same fatty acid composition, the increase of the TAG concentration and the MTP activity in the liver were significantly less and the mRNA levels remained unchanged. The MTP activity levels correlated significantly with hepatic TAG concentration.These results showed that dietary DAG may suppress high fat diet-induced MTP activity in the liver, and indicated the possibility that hepatic TAG concentration may regulate hepatic MTP activity.

Fat-soluble vitamin status is not affected by diacylglycerol consumption

Objective: The objective of this study was to examine the effect of dietary diacylglycerol (DAG) on the bioavailability of fat-soluble vitamins in comparison with triacylglycerol (TAG). Methods: We conducted a long-term administration test of DAG and TAG in 27 healthy men aged 27–47 years. After measuring baseline values, subjects were randomized into two groups, one group (n = 15) was given DAG and the other (n = 12) was given TAG. Subjects ingested 20 g of DAG or TAG either in mayonnaise or an emulsion drink of their own choice at meals once a day for 12 weeks. At 4, 8 and 12 weeks, fasting blood samples were drawn and serum levels of vitamin A, E, and D were measured. Results: There were no significant changes in vitamin A levels throughout the study period. Compared to the initial values (using a Student’s t test for paired values), significant differences of vitamin E and D were seen at some points during the experiment. According to a two-way repeated measures analysis of variance, however, DAG and TAG (lipid) and time had no effect on fat-soluble vitamin levels. Conclusions: Our results indicate that DAG does not affect the absorption of the fat-soluble vitamins in diets.

Effects of Diacylglycerol Oil on Adiposity in Obese Children: Initial Communication

Several studies have shown that diacylglycerol (DAG) oil may suppress accumulation of body fat in adults compared to triacylglycerol (TAG) oil. In this study, we investigated the effect of DAG oil as part of dietetic therapy in obese children. The participants were 11 male and female obese children who were under treatment at the outpatient clinic (four boys, seven girls, age: 7-17 years old). Daily-use cooking oil was changed to DAG oil, and the effects on abdominal fat areas, adipocytokines, and serum lipids were investigated. The total and subcutaneous fat areas significantly decreased in the 5th month after ingestion of DAG oil. Leptin was significantly lower than the initial level after ingestion of DAG oil. The ingestion of DAG oil decreased both the abdominal fat area and leptin in obese children, suggesting that DAG oil prevents obesity in children as well as in adults.