Interleukin-35 attenuates hepatic lipotoxic stress through AMPK-associated metabolic and antioxidative regulation in NAFLD-like models.

Nonalcoholic fatty liver disease (NAFLD) is characterized by dysregulated hepatic lipid metabolism and oxidative stress under chronic metabolic overload. AMP-activated protein kinase (AMPK) is a central regulator of metabolic and redox homeostasis; however, immune-derived signals that coordinate metabolic adaptation in hepatocytes remain incompletely understood. Interleukin-35 (IL-35) is an immunoregulatory cytokine with emerging metabolic relevance, yet its role in hepatic metabolic reprogramming has not been fully elucidated. Here, we investigated whether IL-35 modulates hepatic lipid metabolism and oxidative stress in diet-induced obesity and palmitate-challenged hepatocytes. IL-35 administration attenuated hepatic steatosis, improved insulin resistance indices, and suppressed apoptotic signaling in high-fat diet (HFD)-fed mice. In hepatocytes, IL-35 reduced palmitate-induced lipid accumulation, enhanced fatty acid oxidation, and suppressed oxidative stress markers. Mechanistically, IL-35 increased AMPK phosphorylation and promoted Nrf2-associated antioxidant responses, which were accompanied by increased SOD activity and catalase activity. Genetic silencing of AMPK abrogated the IL-35-mediated improvements in lipid handling, oxidative stress, and apoptosis. Furthermore, IL-35 increased meteorin-like (METRNL) expression in an AMPK-associated manner, and METRNL knockdown partially reduced the hepatoprotective effects of IL-35 in palmitate-challenged hepatocytes. In hepatic stellate cells, IL-35 suppressed palmitate-induced profibrotic marker expression in association with AMPK-linked antioxidative responses. Collectively, these findings suggest that IL-35 supports hepatic metabolic and redox adaptation under lipotoxic stress, at least in part through AMPK-associated signaling and METRNL induction.