Effects of Probiotics on Markers of Oxidative/Nitrosative Stress and Damage Associated with Inflammation in Non-communicable Diseases: A Systematic Review and Meta-analysis of Randomized Placebo-Controlled Trials.

Inflammation and oxidative/nitrosative stress (O&NS) are serious complications in non-communicable diseases (NCDs), including endocrine and metabolic and neurodegenerative diseases. The beneficial probiotic microbes, such as Lactobacillus, Bifidobacterium, and Streptococcus, can decrease O&NS and inflammation. We conducted this systematic review and meta-analysis of randomized controlled trials (RCTs) with aims to elucidate the effects of probiotics on O&NS and inflammation in NCDs. A systematic search of PubMed, Scopus, and EMBASE resulted in the inclusion of studies if they met the eligibility criteria. Methodological quality was assessed using the Cochrane Risk of Bias 2 tool. Data (combined effect size) were analyzed using Meta-Essentials software. Fifteen studies/16 trials with a total of 807 participants (421 cases/386 controls) were reviewed. There was high and moderate certainty of evidence (GRADE) for the effectiveness of probiotic intervention (vs. placebo) in increasing (↑) glutathione (GSH) levels (SMD(SE) = 0.89 (0.51)/p < 0.05, 95%CI - 0.23 to 2.1, I² = 92.77%) and total antioxidant capacity (TAC) (SMD(SE) = 0. 75 (0.22)/p < 0.01, 95%CI 0.28 to 1.23, I² = 87.50%) as well as decreased (↓) malondialdehyde (MDA) (SMD(SE) = 1.03 (0.31)/p < 0.01, 95%CI 0.37 to 1.7, I² = 93.88%) and C-reactive protein (hsCRP) (SMD(SE) = 0.74 (0.36)/p < 0.05, 95%CI - 0.07 to 1.55, I² = 94.32%). There were no effects on nitric oxide, 8-hydroxy-2'-deoxyguanosine, interleukin-6, and tumor necrosis factor-α. Subgroup analysis to reduce heterogeneity indicated probiotic effectiveness on strain number (one/↑GSH), age bracket (41-60 years/↓MDA or > 61 years/↓hsCRP), and NCD (nervous system/neurodegenerative diseases/↑GSH and ↓hsCRP or rheumatoid arthritis/polycystic ovary syndrome/↑TAC). An overall low risk of bias was observed. In conclusion, probiotics may have beneficial effects on markers of O&NS and inflammation in patients with NCDs.