Acute ingestion of catechin-rich green tea improves postprandial glucose status and increases serum thioredoxin concentrations in postmenopausal women.

Elevated postprandial hyperglycaemia and oxidative stress increase the risks of type 2 diabetes and CVD. Green tea catechin possesses antidiabetic properties and antioxidant capacity. In the present study, we examined the acute and continuous effects of ingestion of catechin-rich green tea on postprandial hyperglycaemia and oxidative stress in healthy postmenopausal women. Participants were randomly assigned into the placebo (P, n 11) or green tea (GT, n 11) group. The GT group consumed a catechin-rich green tea (catechins 615 mg/350 ml) beverage per d for 4 weeks. The P group consumed a placebo (catechins 92 mg/350 ml) beverage per d for 4 weeks. At baseline and after 4 weeks, participants of each group consumed their designated beverages with breakfast and consumed lunch 3 h after breakfast. Venous blood samples were collected in the fasted state (0 h) and at 2, 4 and 6 h after breakfast. Postprandial glucose concentrations were 3 % lower in the GT group than in the P group (three-factor ANOVA, group × time interaction, P< 0·05). Serum concentrations of the derivatives of reactive oxygen metabolites increased after meals (P< 0·05), but no effect of catechin-rich green tea intake was observed. Conversely, serum postprandial thioredoxin concentrations were 5 % higher in the GT group than in the P group (three-factor ANOVA, group × time interaction, P< 0·05). These findings indicate that an acute ingestion of catechin-rich green tea has beneficial effects on postprandial glucose and redox homeostasis in postmenopausal women.

Effects of low-volume walking programme and vitamin E supplementation on oxidative damage and health-related variables in healthy older adults.

BACKGROUND: Both exercise and vitamin E supplementation have been shown to reduce oxidative stress and cardiovascular disease risk in older adults, and when combined there is evidence suggesting that they act synergistically. The currently recommended amount of exercise for older adults is 150 min/week of moderate-intensity exercise; however, the minimum amount of exercise necessary to achieve health benefits is not known. The purpose of this study was to investigate the effects of 12 weeks of participation in a low-volume walking exercise programme (i.e. 90 min/week) combined with daily vitamin E supplementation on thiobarbituric acid reactive substances (TBARS) and oxidised low-density lipoprotein (LDL) concentrations in older adults. METHODS: The participants were recruited from the following four groups separately: 1) control (CG, n = 14), 2) vitamin E supplementation (SG, n = 10), 3) walking (WG, n = 7), or 4) walking + supplementation (WSG, n = 7). In the CG, participants were advised to maintain their normal lifestyle during the study. Participants in both the SG and WSG received 450 IU (300 mg) /day of α-tocopherol for 12 weeks. The exercise programme for the WG and WSG consisted of two 30-60 minute sessions weekly for 12 weeks (average walking time was 44.5 ± 1.6 min/session). Blood samples were collected at baseline and at 12 weeks. RESULTS: Delta plasma oxidised LDL concentrations did not differ among four groups (One-factor ANOVA, P = 0.116). However, negative delta plasma TBARS, a marker of oxidative damage, concentrations were observed in the WG, WSG and SG relative to the CG at the end of the study period (One-factor ANOVA, P = 0.001; post hoc tests; CG compared with WG, WSG and SG, P = 0.005; P = 0.021; P = 0.024, respectively). CONCLUSION: These findings suggest that a low-volume of physical activity and/or vitamin E supplementation may be an effective intervention strategy for reducing TBARS concentrations of older adults. TRIAL REGISTRATION: UMIN000008304.

Low-volume exercise training and vitamin E supplementation attenuates oxidative stress in postmenopausal women.

The purpose of this study was to investigate the effects of low-volume exercise training (90 min/wk) and vitamin E supplementation on oxidative stress markers in postmenopausal women. The participants were non-randomly assigned the following four groups: control (C, n=8), vitamin E (S, n=8), exercise (Ex, n=6), or vitamin E and exercise (S+Ex, n=7). The S and S+Ex groups were instructed to take vitamin E (α-tocopherol, 300 mg/d) capsules for 12 wk. The exercise program of Ex and S+Ex groups consisted of walking for a 30-60 min/session 2 d per week for 12 wk. The serum derivatives of reactive oxygen metabolites concentrations were significantly decreased in the Ex, and S+Ex groups after 12 wk compared with the baseline values (three-factor ANOVA, an interaction between exercise and time, p<0.05). Conversely, serum biological antioxidant potential concentrations in the S and Ex groups were significantly higher at 12 wk than at the baseline, but not in the S+Ex group (three-factor ANOVA, an interaction between supplementation, exercise and time, p<0.05). Plasma thioredoxin concentrations in the S, Ex, and S+Ex groups were significantly higher at 12 wk than at the baseline values (three-factor ANOVA, interactions between exercise and time, and between supplementation, exercise and time, p<0.05). Our findings suggest that low-volume physical activity may improve resting oxidative stress status in postmenopausal women.