Effect of flavonoid intake on circulating levels of adiponectin and leptin: A systematic review and meta-analysis of randomized controlled clinical trials.

This meta-analysis of randomized controlled trials (RCTs) was conducted to explore the effects of flavonoid intake on adiponectin and leptin levels. The PubMed, EMBASE, and Cochrane Library databases were searched on March 1, 2021. Random-effects, subgroup, sensitivity, and meta-regression analyses were conducted on 40 publications. Flavonoid intake significantly increased circulating adiponectin (0.54 µg/ml, 95% CI [0.20, 0.88], p = .002; I2  = 86.4%) and significantly reduced leptin levels (weighted mean difference: -0.79 ng/ml, 95% CI [-1.33, -0.25], p = .004; I2  = 87.7%). Subgroup analysis demonstrated that flavonoid intervention produced a significant elevation in adiponectin levels only in studies that lasted more than 12 weeks, conducted in Asian regions, were parallel-designed, involved obese or overweight participants and participants with type 2 diabetes mellitus (T2DM) or cardiovascular diseases, used tea catechins, and used a dietary supplement intervention. A significantly negative effect on leptin levels was observed in studies conducted in Asian countries, with healthy participants and participants with T2DM, used whole food interventions, and involved participants with lower baseline leptin levels. In conclusion, flavonoid intake significantly increased circulating adiponectin and decreased leptin levels; however, study heterogeneity was very high. Future well-designed trials are required to address heterogeneous study designs and clarify the efficacy of plants in regulating adiponectin and leptin levels.

Effects of green tea polyphenols on trace metals level of rats on food restriction and high-fat diet.

Little evidence showed the interplay between tea and diet in the regulation of trace metal. Here, we examined the effects of green tea polyphenols (GTPs) on the level of trace elements (TEs) in rats on food restriction or high-fat diet. Thirty-six rats (Wistar, male) were randomly divided into 6 groups and fed on standard diet, food restriction and high-fat diet with or without GTPs (200 mg/kg bw/day) supplementation, respectively. Levels of vanadium (V), manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), selenium (Se), molybdenum (Mo) and cobalt (Co) in feed, whole blood, femur and urine were measured by inductively coupled plasma mass spectrometry (ICP-MS). Blood glucose, total cholesterol (TC), triglycerides (TG), high and low density lipoprotein-cholesterol (LDL-C, HDL-C) in serum were determined. Decreased daily intakes of TEs were observed in rats on food restriction and high-fat diet. Decreased whole blood level of Zn, femur level of Co and increase urinary excretion of Se were observed in rats fed on high-fat diet. GTPs altered the whole blood level of several TEs in rats on food restriction (V, Zn, Co) or high-fat diet (V, Se), respectively, but not in rats fed on standard diet. The level of several TEs in femur and the daily urinary excretion of V and Mo were altered by GTPs in rats on all of the three diets. In addition, rats fed on high-fat diet developed dyslipidemia, which was ameliorated by GTPs. The data indicated that diet status played a role in the effects of GTPs on TEs and lipid metabolism, and trace elements may play a role in the modulation of lipid metabolic disturbances by high-fat diet and GTPs.

Green Tea Polyphenols Ameliorate the Early Renal Damage Induced by a High-Fat Diet via Ketogenesis/SIRT3 Pathway.

SCOPE: Several reports in the literature have suggested the renoprotective effects of ketone bodies and green tea polyphenols (GTPs). Our previous study found that GTP consumption could elevate the renal expression of the ketogenic rate-limiting enzyme, which was decreased by a high-fat diet (HFD) in rats. Here, we investigated whether ketogenesis can mediate renoprotection by GTPs against an HFD. METHODS AND RESULTS: Wistar rats were fed a standard or HFD with or without GTPs for 18 weeks. The renal oxidative stress level, kidney function, renal expression, and activity levels of mitochondrial 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) synthase 2 (HMGCS2) and sirtuin 3(SIRT3) were detected. The increased renal oxidative stress and the loss of renal function induced by the HFD were ameliorated by GTPs. Renal ketogenesis and SIRT3 expression and activity levels, which were reduced by the HFD, were restored by GTPs. In vitro, HEK293 cells were transfected with the eukaryotic expression plasmid pcDNA HMGCS2. GTP treatment could upregulate HMGCS2 and SIRT3 expression. Although SIRT3 expression was not affected by HMGCS2 transfection, the 4-hydroxy-2-nonenal (4-HNE) level and the acetyl-MnSOD (K122)/MnSOD ratio were reduced in HMGCS2-transfected cells in the context of H2O2. CONCLUSION: The ketogenesis/SIRT3 pathway mediates the renoprotection of GTPs against the oxidative stress induced by an HFD.