Lactobacillus plantarum RLL68 fermented black tea beverage attenuates high-fat-diet-induced non- alcoholic fatty liver by modulating hepatic lipid metabolism and gut microbiota

Abstract Lactic acid bacteria (LAB)-fermented foods possess prominent gastrointestinal regulatory functions and excellent physiological nutritional value. This study aimed to investigate the ameliorative effects of L. plantarum RLL68-fermented black tea beverage (FBTB) on high-fat diet (HFD)-induced non-alcoholic fatty liver (NAFL) in mice. The results demonstrated that FBTB intervention significantly mitigated the elevation of serum lipid indicators, including total cholesterol, triglycerides, and low-density lipoprotein cholesterol (LDL-c), and effectively alleviated excessive hepatic lipid accumulation. Moreover, FBTB improved glyceride and glycerophospholipid metabolism by upregulating the levels of hepatoprotective unsaturated lipids and phospholipids, while reducing the abundance of lipogenic saturated lipids that drive hepatic steatosis. Additionally, FBTB supplementation improved gut microbial diversity in HFD-fed mice, remarkably enriched beneficial bacterial genera such as Lactobacillus , Akkermansia , and Dubosiella , and suppressed the proliferation of steatosis-associated detrimental taxa including Alistipes and Bacteroides . Correlation analysis verified that Lactobacillus and Akkermansia were positively correlated with unsaturated lipid contents and negatively correlated with saturated lipid levels. Collectively, two-month FBTB intervention effectively reshaped the gut microbiota structure and promoted short-chain fatty acid (SCFA) production in mice. Furthermore, FBTB synergistically modulated the expression of lipid metabolism-related genes (e.g.,Acaca, Cpt1a) and functional proteins (TLR4, ALDH2), thereby restoring disrupted hepatic lipid homeostasis. In conclusion, FBTB exerts protective effects against HFD-induced NAFL via regulating gut microbiota and hepatic lipid metabolism. This finding provides a theoretical basis for the development and application of LAB-fermented functional foods for the prevention and improvement of NAFL and related metabolic disorders.