The effect of probiotic and synbiotic supplementation on biomarkers of inflammation and oxidative stress in diabetic patients: A systematic review and meta-analysis of randomized controlled trials

The role of gut microbiota in the management of diabetes has been shown. Several current trials are investigating the effect of probiotics and prebiotics, which are widely used to modulate intestinal microbiota, on inflammatory factors and biomarkers of oxidative stress in diabetic patients; however, their findings are controversial. The aim of the current meta-analysis was to evaluate the effects of probiotic and synbiotic supplementation on levels of serum high-sensitivity C-reactive protein (hs-CRP) and biomarkers of oxidative stress in diabetic patients. We searched the PubMed, Web of Science, and The Cochrane Library databases from the inception to October 31, 2018. Randomized controlled trials (RCTs) which reported the effect of probiotics or synbiotics on circulating (serum and plasma) inflammatory marker (hs-CRP) and oxidative stress indicators (malondialdehyde [MDA], glutathione [GSH], nitric oxide [NO], and total antioxidant capacity [TAC]) among patients with diabetes were included. Eligible studies were assessed for risk of bias and subjected to qualitative and quantitative synthesis using either fixed- or random-effects models accounting for clinical heterogeneity. Our meta-analysis identified 16 eligible RCTs (n = 1060). The methodological quality varied across these trials. Pooled data from these trials demonstrated that probiotic and synbiotic consumption significantly decreased hs-CRP level (standardized mean difference [SMD]=-0.38; 95% confidence interval [CI]:-0.51,-0.24; P = 0.000) and MDA (SMD=-0.61; 95% CI: -0.89, -0.32; P = 0.000) in diabetic patients compared to those in subjects receiving placebos. In addition, probiotic and symbiotic supplementation was found to increase TAC (SMD = 0.31; 95% CI: 0.09, 0.52; P = 0.006), NO (SMD, 0.62; 95% CI, 0.25 to 0.99; P = 0.001) and GSH (SMD = 0.41; 95% CI: 0.26, 0.55, P = 0.000) levels. The results of this systematic review and meta-analysis suggest that probiotic and synbiotic supplementation may help to improve biomarkers of inflammation and oxidative stress in diabetic patients. Further studies are needed to develop clinical practice guidelines for the management of inflammation and oxidative stress in these patients.