Effects of bioprocessed potato peel extract on hepatic steatosis in obese rats: modulation of lipid metabolism, bile acid synthesis, and oxidative stress

Abstract

Potato peels, a major component of food processing by-products, contribute substantially to the environmental waste burden. However, they contain diverse bioactive compounds with potential health-promoting properties. This study aimed to investigate the effects of potato peel extract (PPE) fermented with Rhizopus oryzae, enriched with bioactive metabolites through microbial biotransformation, on ameliorating high-fat diet (HFD)-induced metabolic dysfunction-associated steatotic liver disease (MASLD) in rats. Male Sprague–Dawley (SD) rats were fed an HFD for 4 weeks to induce obesity. The rats were then divided into 5 groups: control, HFD, and HFD +100 mg/kg BW PPE (PPE100), HFD +200 mg/kg BW PPE (PPE200), and HFD +20 mg/kg BW policosanol (P20). The treatments were administered over a period of 4 weeks. Blood and liver samples were collected to assess parameters associated with lipid accumulation by determining serum and hepatic levels of triglyceride, total cholesterol, and free fatty acid. The expression of cluster of differentiation 36 was evaluated to assess hepatic fatty acid uptake. Hepatic lipogenesis was evaluated through the expression of acetyl-CoA carboxylase and fatty acid synthase. In contrast, fatty acid oxidation was examined by peroxisome proliferator-activated receptor alpha, carnitine palmitoyltransferase-1A, hydroxyacyl-CoA dehydrogenase trifunctional multienzyme complex subunit alpha, and acetyl-CoA acyltransferase 2. Cholesterol homeostasis and bile acid metabolism involve the expression of low-density lipoprotein receptor, HMG-CoA reductase, cholesterol 7α-hydroxylase, and bile salt export pump were examined. Oxidative stress was assessed by measuring malondialdehyde levels, whereas antioxidant status was evaluated through antioxidant enzyme activities and nuclear factor erythroid 2-related factor 2 (Nrf2) signaling. Histopathological changes were evaluated through histopathological examination and assessment of the NAFLD activity score. Mechanistic analyses revealed that PPE ameliorates hepatic lipid accumulation by decreasing hepatic lipid transport and lipogenesis, while promoting fatty acid oxidation and modulating bile acid homeostasis. Additionally, PPE attenuated oxidative stress, as evidenced by reduced MDA levels, and enhanced antioxidant defense mechanisms through the upregulation of Nrf2 expression. These effects were further supported by improvements in liver histopathology. Collectively, these findings suggest that fermented PPE may serve as a functional food ingredient, integrating sustainable food processing with nutritional strategies and management of MASLD.