李少华
云南博亚医院有限公司 肾内科
BACKGROUND:The effect of green tea catechins (GTCs) with or without caffeine on glycemic control is controversial.OBJECTIVE:We aimed to identify and quantify the effects of GTCs or GTC-caffeine mixtures on glucose metabolism in adults.DESIGN:A comprehensive literature search was conducted to identify relevant trials of GTCs with or without caffeine on markers of glycemic control [fasting blood glucose (FBG), fasting blood insulin (FBI), glycated hemoglobin (Hb A1c), and homeostatic model assessment of insulin resistance (HOMA-IR)]. Weighted mean differences were calculated for net changes by using fixed-effects models. Prespecified subgroup analyses were performed to explore the influence of covariates on net changes in FBG and FBI concentrations.RESULTS:Twenty-two eligible randomized controlled trials with 1584 subjects were identified. Pooled analyses showed that FBG (-1.48 mg/dL; 95% CI: -2.57, -0.40 mg/dL) decreased significantly with GTCs with or without caffeine, whereas FBI (0.04 μU/mL; 95% CI: -0.36, 0.45 μU/mL), Hb A1c (-0.04%; 95% CI: -0.15, 0.08%), and HOMA-IR (-0.05; 95% CI: -0.37, 0.26) did not. Subgroup analyses indicated that the glucose-lowering effect was apparent when the duration of follow-up was over a median of 12 wk. Overall, no significant heterogeneity was detected for FBG, FBI, Hb A1c, or HOMA-IR.CONCLUSIONS:The meta-analysis showed that the administration of GTCs with or without caffeine resulted in a significant reduction in FBG. The limited data available on GTCs did not support a positive effect on FBI, Hb A1c, or HOMA-IR. Thus, more large and well-designed trials are needed in the future. This trial was registered at http://www.crd.york.ac.uk/prospero as CRD42012002139.
The American journal of clinical nutrition 2013
BACKGROUND:The effect of green tea beverage and green tea extract on lipid changes is controversial.OBJECTIVE:We aimed to identify and quantify the effect of green tea and its extract on total cholesterol (TC), LDL cholesterol, and HDL cholesterol.DESIGN:We performed a comprehensive literature search to identify relevant trials of green tea beverages and extracts on lipid profiles in adults. Weighted mean differences were calculated for net changes in lipid concentrations by using fixed-effects or random-effects models. Study quality was assessed by using the Jadad score, and a meta-analysis was conducted.RESULTS:Fourteen eligible randomized controlled trials with 1136 subjects were enrolled in our current meta-analysis. Green tea consumption significantly lowered the TC concentration by 7.20 mg/dL (95% CI: -8.19, -6.21 mg/dL; P < 0.001) and significantly lowered the LDL-cholesterol concentration by 2.19 mg/dL (95% CI: -3.16, -1.21 mg/dL; P < 0.001). The mean change in blood HDL-cholesterol concentration was not significant. Subgroup and sensitivity analyses showed that these changes were not influenced by the type of intervention, treatment dose of green tea catechins, study duration, individual health status, or quality of the study. Overall, no significant heterogeneity was detected for TC, LDL cholesterol, and HDL cholesterol; and results were reported on the basis of fixed-effects models.CONCLUSION:The analysis of eligible studies showed that the administration of green tea beverages or extracts resulted in significant reductions in serum TC and LDL-cholesterol concentrations, but no effect on HDL cholesterol was observed.
The American journal of clinical nutrition 2011
BACKGROUND:The effect of cocoa products on lipid changes is controversial.OBJECTIVES:We aimed to identify and quantify the effect of cocoa on total cholesterol, LDL cholesterol, and HDL cholesterol.DESIGN:A comprehensive literature search was conducted for relevant trials of cocoa on lipid profile. Weighted mean differences were calculated for net changes in lipid concentrations by using fixed-effects or random-effects models. Previously defined subgroup analyses were performed to identify the source of heterogeneity.RESULTS:Eight trials (involving 215 participants) were included and evaluated. Because there was only one relatively longer-term study, we focused on the short-term data to evaluate the effects of cocoa on plasma lipid. Cocoa consumption significantly lowered LDL cholesterol by 5.87 mg/dL (95% CI: -11.13, -0.61; P < 0.05) and marginally lowered total cholesterol by 5.82 mg/dL (95% CI: -12.39, 0.76; P = 0.08). However, no significant change was seen in LDL cholesterol in high-quality studies (3 studies included; -4.98 mg/dL; 95% CI: -13.18, 3.21; P = 0.23). Subgroup analyses suggested a cholesterol-lowering effect only in those subjects who consumed a low dose of cocoa and with cardiovascular disease risks. There was no evidence of a dose-effect relation, of any effect in healthy subjects, or of any change in HDL cholesterol.CONCLUSIONS:Short-term cocoa consumption significantly reduced blood cholesterol, but the changes were dependent on the dose of cocoa consumption and the healthy status of participants. There was no dose response and no effect in healthy participants. Future high-quality studies are needed to determine the efficiency of moderate cocoa consumption on lipid profile in long-term intervention and in subjects with other cardiometabolic risk factors.
The American journal of clinical nutrition 2010
BACKGROUND:The effect of isoflavone on endothelial function in postmenopausal women is controversial.OBJECTIVE:The objective of this study was to evaluate the effect of oral isoflavone supplementation on endothelial function, as measured by flow-mediated dilation (FMD), in postmenopausal women.DESIGN:A meta-analysis of randomized placebo-controlled trials was conducted to evaluate the effect of oral isoflavone supplementation on endothelial function in postmenopausal women. Trials were searched in PubMed, Embase, the Cochrane Library database, and reviews and reference lists of relevant articles. Summary estimates of weighted mean differences (WMDs) and 95% CIs were obtained by using random-effects models. Meta-regression and subgroup analyses were performed to identify the source of heterogeneity.RESULTS:A total of 9 trials were reviewed in the present meta-analysis. Overall, the results of the 9 trials showed that isoflavone significantly increased FMD (WMD: 1.75%; 95% CI: 0.83%, 2.67%; P = 0.0002). Meta-regression analysis indicated that the age-adjusted baseline FMD was inversely related to effect size. Subgroup analysis showed that oral supplementation of isoflavone had no influence on FMD if the age-adjusted baseline FMD was > or = 5.2% (4 trials; WMD: 0.24%; 95% CI: -0.94%, 1.42%; P = 0.69). This improvement seemed to be significant when the age-adjusted baseline FMD levels were <5.2% (5 trials; WMD: 2.22%; 95% CI: 1.15%, 3.30%; P < 0.0001), although significant heterogeneity was still detected in this low-baseline-FMD subgroup.CONCLUSIONS:Oral isoflavone supplementation does not improve endothelial function in postmenopausal women with high baseline FMD levels but leads to significant improvement in women with low baseline FMD levels.
The American journal of clinical nutrition 2010
Hypertension has become a large burden of global development, but the mechanisms of it have still not been well elucidated. Increased contractility of vascular smooth cells induced by the overactivity of neurohormonal system or stress is one of the main and popular explanations until now. Smoothelin-B, recognized as the actin-binding protein, is only expressed in vascular smooth muscle cells and takes part in the contraction process of vascular smooth cells. Rensen et al. demonstrated that deficiency of smoothelin-B resulted in reduced contractile capacity of vascular smooth muscle and hypertension in mice, which provides us a novel fact in the pathogenesis of hypertension. Therefore, we proposed that reduced contractile capacity of vascular smooth muscle could result in hypertension, the mechanism of which might be related to normal cardiac output but blood retention induced by reduced vasoconstriction, impaired vasodilatation and decreased blood vessels. Studies are needed to demonstrate our hypotheses and further investigation and discussion should be focused on the treatment in these patients because beta-blockers, angiotensin-converting enzyme inhibitor or angiotensin receptor blocker may be not suitable for them.
Medical hypotheses 2009
