Nicotinamide riboside and dietary restriction effects on gut microbiota and liver inflammatory and morphologic markers in cafeteria diet-induced obesity in rats

Objectives: No specific therapy is available for metabolic dysfunction-associated fatty liver disease. We investigated nicotinamide riboside (NR) and dietary restriction (DR) effects in liver lipids, inflammation, his-tology, intestinal permeability, and gut microbiota in a cafeteria diet (CAFD)-induced obesity model. Methods: Adult male Wistar rats were randomly assigned to standard diet (SD) or CAFD. After 6 wk, they were subdivided into six groups-SD + vehicle (Veh) (distilled water), SD + NR (400 mg/kg), DR + Veh, DR + NR, CAFD + Veh, and CAFD + NR-for 4 wk more until euthanasia. Results: CAFD increased the hepatic content of lipids, triacylglycerols, and total cholesterol and promoted hepato-megaly, steatosis, steatohepatitis, and liver fibrosis. DR intervention successfully delayed the onset of CAFD-induced liver abnormalities except for steatosis and fibrosis. CAFD suppressed Sirt1 expression in the liver and DR increased Sirt3 expression. CAFD did not affect hepatic inflammatory genes but DR enhanced Il10 expression while decreasing Il1b expression. CAFD reduced Firmicutes and increased Bacteroidetes and Cyanobacteria, with no changes in intestinal permeability. Gut microbiota patterns in animals exposed to DR were similar to those of ani-mals in SD. NR, specifically in CAFD, reduced hepatic triacylglycerols and total cholesterol deposition and collagen fiber accumulation in the liver and limited the colonization of CAFD-induced Cyanobacteria. NR combined with DR decreased the liver's relative weight and Tnfa expression and suppressed Sirt1 and Sirt3 hepatic expression. Conclusions: This study suggests that NR can be a potential adjuvant to metabolic dysfunction-associated fatty liver disease therapy, encouraging further research in this field. & COPY; 2023 Published by Elsevier Inc.