Effect of endurance training supplemented with green tea extract on substrate metabolism during exercise in humans.

Endurance training and ingestion of green tea extract (GTE), composed mainly of tea catechins (TC), are well known to enhance fat metabolism. However, their synergistic effects remain to be fully elucidated. We tested the hypothesis that endurance training supplemented with GTE would further accelerate whole-body fat utilization during exercise, compared with training alone, in humans. Twelve healthy male subjects [peak oxygen consumption (VO2peak), 50.7 ± 1.3 (SEM) mL/kg/min] were divided into two groups: GTE and placebo (PLA) groups. Subjects in both groups performed a cycle ergometer exercise at 60% of VO2peak for 60 min/day, 3 days/week, and daily ingested 572.8 or 0 mg TC in GTE and PLA groups for 10 weeks, respectively. Before and after training, respiratory gas exchange was measured during 90-min exercise at pre-training ∼55% of VO2peak. After training, the average respiratory exchange ratio during exercise remained unchanged in the PLA group (post-training: 0.834 ± 0.008 vs pre-training: 0.841 ± 0.004), whereas it was lower in the GTE group (post-training: 0.816 ± 0.006 vs pre-training: 0.844 ± 0.005, P<0.05). These results suggest that habitual GTE ingestion, in combination with moderate-intense exercise, was beneficial to increase the proportion of whole-body fat utilization during exercise.

Effects of vegetable oils and C18-unsaturated fatty acids on plasma ethanol levels and gastric emptying in ethanol-administered rats.

The effects of vegetable oils (soybean oil and coconut oil) and C18-unsaturated fatty acids (oleic acid, C18:1; linoleic acid, C18:2; linolenic acid, C18:3) on plasma ethanol levels in male rats (6 weeks old) were investigated. Vegetable oils decreased and delayed the peak of plasma ethanol concentration: a dose-response to vegetable oils was observed in the concentration and time to maximum concentration of plasma ethanol but no change in disappearance time. These phenomena were observed in two conditions: 1) oral administration of vegetable oils before oral intubation of ethanol and 2) simultaneous oral administration of vegetable oils and ethanol. Similar responses were obtained in three C18-unsaturated fatty acids. No changes in hepatic alcohol and aldehyde dehydrogenase isozyme (high Km and low Km) activities were observed. The remaining rate of ethanol in stomach was significantly higher with administration of vegetable oils or linoleic acid. A high negative correlation between the maximum plasma ethanol concentration and the remaining rate of ethanol in stomach was found. These results suggest that the slowing of the gastric emptying is a major mechanism for the decreasing and delaying effects on plasma ethanol levels by vegetable oils. The present paper also suggests that fatty acids may participate in the decreasing and delaying actions on the peak of plasma ethanol concentration by vegetable oils.

Lowering and delaying actions of bovine bile on plasma ethanol levels in rats.

The effects of bovine bile (50-400 mg.kg-1 BW) on plasma ethanol levels in male rats (6-8 weeks old) were examined. Bovine bile decreased and delayed the peak of plasma ethanol concentration: a dose response to bovine bile was observed in the concentration and time to maximum concentration of ethanol but no change in disappearance rate. These phenomena were observed in two conditions: 1) oral administration of bovine bile before oral intubation of ethanol (1.0 g.kg-1 BW) and 2) simultaneous oral administration of bovine bile and ethanol. Similar responses were obtained in taurocholic acid. No changes in hepatic alcohol and aldehyde (low Km and high Km) dehydrogenase activities were observed. The remaining rate of ethanol in stomach was significantly higher with administration of bovine bile. A negative correlation between the maximum ethanol concentration and the remaining rate of ethanol in stomach was found. The intestinal absorption rate of ethanol decreased significantly in the presence of bovine bile. These results suggest that the delay of the gastric emptying and/or the decrease of the intestinal absorption rate of ethanol are major mechanisms for the decreasing and delaying effects on plasma ethanol by bovine bile. The present paper also suggests that bile acids such as taurocholic acid may participate in the lowering and delaying actions on the peak of plasma ethanol concentration by bovine bile.

Effect of sex hormones on rat liver cytosolic alcohol dehydrogenase activity.

Rat liver cytosolic alcohol dehydrogenase (ADH) activity is known to be significantly higher in females than in males. To elucidate a possible mechanism of sex difference in the ADH activities, we studied the in vivo effects of the administrations of beta-estradiol, progesterone or testosterone, and castrations (orchiectomy and ovariectomy) on the ADH activities in male and female Sprague-Dawley adult rats. Furthermore, we studied the ADH activities in six liver portions of sham-operated male, orchiectomized male, and female rats. The ADH activities were higher in orchiectomized male rats than in sham-operated male rats. These results were observed in all liver portions. The administration of testosterone (5 mg/kg BW, twice a day for 7 d) to orchiectomized male rats significantly decreased ADH activities. The ADH activities in ovariectomized female rats were comparable with those in sham-operated female rats. The administration of beta-estradiol (50 micrograms/kg BW, once every 2 d for 20 d) or progesterone (75 micrograms/kg BW, once every 2 d for 20 d) to rats increased the ADH activities in males more than in females. These results suggest that the inhibitory action of androgen and the slight facilitatory actions of progestin and estrogen are involved in the mechanism of sex difference in adult rat liver cytosolic ADH activity.

Sex-dependent developmental change of rat liver cytosolic alcohol dehydrogenase activity.

Rat liver cytosolic alcohol dehydrogenase (ADH) is the principal enzyme which catalyzes the oxidation of ethanol. ADH activity is known to be significantly higher in females than in males. However, the precise mechanism of the sex-difference in ADH activity is uncertain. Recently, we have shown that the inhibitory action of androgen and the slight facilitatory actions of progestin and estrogen are involved in the mechanism of sex-difference in adult rat liver ADH activity. In the present study, we studied the difference of the postnatal developmental changes of ADH activity between males and females. ADH activity increased rapidly after birth up to about 12 d of age, and was not different in the two sexes. In female rats, ADH activity peaked at about 30 d of age and then increased gradually to plateau levels. However, the ADH activity of male rats fell markedly between 30 and 45 d old, and the reduced enzyme activity was observed until 104 d old. In conclusion, the ADH activity of male rats fell between 30 and 45 d after birth. At the ages over the turning point, the ADH activity was significantly lower in male than in female rats.