PYY_3-36 potentiates semaglutide-mediated mitochondrial modulation in MASLD

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a frequent comorbidity of obesity. Incretins have emerged as promising therapeutics for MASLD, but their exact mechanisms of action remain unclear. In this study with obese rats, we investigated the cellular effects of the glucagon-like peptide 1 receptor agonist semaglutide and the neuropeptide Y-2 (NPY-2) receptor agonist peptide YY 3-36 (PYY_3-36) on hepatic mitochondria with a focus on mitochondrial oxygen consumption and reactive oxygen species (ROS) emission. Following an 8-wk feeding period with a high-fat/fructose diet and Nω-nitro-l-arginine methyl ester (l-NAME), male Wistar rats were randomized into the following treatment groups for further 8 wk: semaglutide (Sema, n = 10), PYY_3-36 (n = 7), semaglutide + PYY_3-36 (n = 10), food restriction (FR; n = 4), and saline control (n = 17). Mitochondrial respiration and peroxide emission were examined using an Oroboros O2K-respirometer. Hematoxylin and eosin, Oil Red, and Sirius Red stainings were analyzed for fibrosis, inflammation, and lipid storage. Hepatic inflammation and histological MASLD score were significantly mitigated by semaglutide and PYY_3-36 with additive effects in the combination group. Ribonucleic acid-sequencing revealed downregulation of pathways responsible for oxidative phosphorylation and beta-oxidation. Oxidative phosphorylation (OxPhos)-related genes were significantly reduced in Sema + PYY_3-36, consistent with mitochondrial respirometry. Hepatic medium-chain acyl-CoA dehydrogenase and proliferator-activated receptor gamma coactivator-1-alpha expression, key regulators of beta-oxidation, was significantly reduced by PYY_3-36. Superior effects occurred in the semaglutide + PYY_3-36 group with a decline in mitochondrial respiration, decreased mitochondrial H₂O₂ production and reduced hepatocellular stress, whereas FR and weight loss had no significant impact on mitochondrial respiration or OxPhos-regulating genes. This study highlights the favorable effects of semaglutide and PYY_3-36 mitigating mitochondrial dysfunction in MASLD, providing insight into their possible molecular mechanisms.NEW & NOTEWORTHY This study provides a mechanistic framework for investigating glucagon-like peptide 1 receptor (GLP-1R) and neuropeptide Y-2 receptor (NPY-2R) agonism as therapeutic strategies for MASLD. Semaglutide and PYY_3-36 restored mitochondrial function, reduced oxidative stress, and limited hepatocellular injury, revealing complementary pathways governing steatosis and metabolic resilience. A weight loss-matched food restriction group showed no improvement in mitochondrial respiration, indicating that benefits extend beyond weight loss. These findings support pathway targeted therapeutic selection and underscore the translational potential of dual agonist strategies in MASLD.