The impact of chronic low-grade inflammation in the development of non-alcoholic fatty liver disease (NAFLD) has been studied widely. Previous studies showed gut pathogens' effects on inflammation development in NAFLD patients; hence, hypothetically, gut microbial therapy by administration of probiotics, synbiotics, and prebiotics may alleviate inflammation in these individuals. Several studies were performed in this regard; however, conflicting results were obtained. In this study, we aimed to comprehensively evaluate the effects of gut microbial therapy on inflammatory markers in NAFLD patients in a meta-umbrella design. Two independent researchers investigated international databases, including PubMed, Web of Science, Scopus, and Cochrane Library, from inception until March 2023. Meta-analyses evaluating the impact of probiotics, synbiotics, or prebiotics on inflammatory markers of patients with NAFLD were eligible for our study. AMASTAR 2 checklist was used to evaluate the quality of included studies. Random effect model was performed for the analysis, and Egger's regression test was conducted to determine publication bias. A total number of 12 studies were entered into our analysis. Our findings revealed that gut microbial therapy could significantly reduce serum C-reactive protein (CRP) levels among NAFLD patients (ES:-0.58; 95% CI:-0.73,-0.44, P<0.001). In subgroup analysis, this reduction was observed with both probiotics (ES:-0.63; 95% CI:-0.81,-0.45, P<0.001) and synbiotics (ES:-0.49; 95% CI:-0.74,-0.24, P<0.001). In addition, gut microbial therapy could significantly decrease tumor necrosis factor-a (TNF-a) levels in NAFLD patients (ES:-0.48; 95% CI:-0.67 to-0.30, P<0.001). In subgroup analysis, this decrease was observed with probiotics (ES:-0.32; 95% CI:-0.53,-0.11, P=0.002) and synbiotics (ES:-0.96; 95% CI:-1.32,-0.60, P<0.001). Not enough information was available for assessing prebiotics' impacts. The results of this umbrella review suggest that probiotics and synbiotics have promising effects on inflammatory markers, including TNF-a and CRP; however, more research is needed regarding the effects of prebiotics. CRD42022346998.
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