Effects of dietary polyphenols in the glycemic, renal, inflammatory, and oxidative stress biomarkers in diabetic nephropathy: a systematic review with meta-analysis of randomized controlled trials

Abstract

Context Polyphenols have antioxidant, anti-inflammatory, and anti-glycation properties. Objective To assess the effects of dietary polyphenols, from food sources or supplements, on the anthropometric, glycemic, renal, inflammatory, and oxidative stress markers in adults with diabetic nephropathy (DN). Data sources Systematic searches for randomized clinical trials were performed in MEDLINE, Embase, CENTRAL, Web of Science, LILACS, SciELO, opengrey.eu, and ClinicalTrials.gov databases until December 2021. Data extraction Studies with adults with DN were included. Random-effects meta-analyses were conducted. Risk of bias of the studies and Grading of Recommendations, Assessment, Development, and Evaluation assessment were carried out. Data analysis The searches resulted in 5614 unique occurrences, and 34 full-text articles were retrieved. Of these, 17 studies were included in the qualitative synthesis. Most of the studies used soy protein or milk (n = 5; 0.5–1 g/kg of body weight/d of soy protein, or introduction of 240 mL/d of soy milk) or turmeric/curcumin (n = 5; dose range, 80 to 1500 mg/d) as the intervention. The following outcomes were analyzed: body mass index, glycated hemoglobin (HbA1c), proteinuria, creatinine clearance, glomerular filtration rate (GFR), urinary albumin to creatinine ratio, and levels of fasting blood glucose, insulin, serum urea and creatinine, C-reactive protein, serum tumor necrosis factor-α, and serum malondialdehyde (MDA). The polyphenol intervention significantly decreased HbA1c (n = 7 studies; –0.27% [95%CI, –0.51%, –0.04%]), proteinuria (n = 5 studies; –109.10 [95%CI, –216.57, –1.63] mg/24 h), and MDA (n = 5 studies; z-score: –0.41; 95%CI, –0.71, –0.10), and significantly increased GFR (n = 7 studies; 3.65 [95%CI, 0.15–7.15] mL/min/1.73 m2). Overall, studies showed a high risk of bias, and outcomes showed a low or very-low quality in the Grading of Recommendations, Assessment, Development, and Evaluation assessment. Conclusions There is a clinically modest effect of dietary polyphenols intervention in HbA1c, proteinuria, GFR, MDA, and C-reactive protein levels in patients with DN. It is impossible to establish clinical recommendations, because the evidence was of’ low or very-low quality and because of the heterogeneity of types and dose regimens used in the studies. Systematic Review Registration PROSPERO registration no. ID245406.

Effects of turmeric (Curcuma longa) supplementation on glucose metabolism in diabetes mellitus and metabolic syndrome: An umbrella review and updated meta-analysis

“…Identification and selection of SRMAs and individual RCTs. Of 3,507 identified studies, 14 SRMAs [15][16][17][18][19][20][33][34][35][36][37][38][39][40]…”

“…Description of SRMAs. [33][34][35][36][37][38][39][40] were pairwise MAs, published in 2015-2022 and included 5-26 RCTs with sample sizes of 290-1,790 patients (S3 Table in S1 File). The outcome measures were pooled using either SMD (6 studies) or UMD (9 studies).…”

“…Quality of SRMAs. All 14 included SRMAs [15][16][17][18][19][20][33][34][35][36][37][38][39][40] were graded with critically low quality based on the AMSTAR-2 rating (S4 Table in S1 File) due to missing information on the justification of excluded studies (100%), the funding sources of included studies (100%), missing consideration for the risk of bias when interpreting the results of the review (90.91%), missing assessment of the impact of risk of bias on study results (72.73%), and a lack of established review methods (63.64%).…”

Updated Information of the Effects of (Poly)phenols against Type-2 Diabetes Mellitus in Humans: Reinforcing the Recommendations for Future Research

“…We went through some of the most recent reviews and meta-analyses gathering different RCTs testing the antidiabetic effects of different (poly)phenols [5,[15][16][17][18]. The main evidence refers most commonly to changes in FPG and HbA1c, while the effects on other related variables such as HOMA-IR or insulin are less frequently indicated.…”

“…The authors widely discussed several issues related to the quality of studies and the factors that affect interindividual variability, which must be addressed in future studies to validate the effects of (poly)phenols against T2DM in specific and well-characterized individuals. The effects of (poly)phenols in on glycemic biomarkers in a population of individuals with diabetes characterized by a developed nephropathy have also recently been reviewed [17]. The authors collected 13 trials and reported a general non-significant effect in FPG (+2.78 mg/dL) but a significant mean reduction in HbA1c (−0.27%).…”