Weight cycling exacerbates hepatic and metabolic alterations associated with metabolic dysfunction-associated steatotic liver disease in a preclinical model

Weight cycling (WC) may contribute to metabolic dysfunction-associated steatotic liver disease (MASLD) progression through adaptations associated with obesogenic memory. The objective was to investigate WC effects on MASLD development in adult mice. Male C57BL/6 mice underwent an 18-week weight cycling protocol with chow or Western-style diets (HFS), divided into Control (C), Obesity (Ob), Weight Loss (WL), and Weight Cycling (WC) groups (n=10/group). The project was approved by CEUA (No. 020/2024). WC showed body weight and fat mass similar to Ob, whereas WL resembled C. WC showed higher TG (+52.4%), TC (+26.3%), AST (+19.2%), ALT (+31.3%), TNFa (+75.3%), and Il1b (+147.7%) than Ob, while LPS levels were similar. Histology showed similar steatosis in WC and Ob, but predominantly microvesicular in WC (+48.3% vs. Ob) and macrovesicular in Ob. WL showed reduced steatosis (-54% vs. Ob). Hepatic triacylglycerol was similar between WC and Ob. WC showed higher Srebf1 expression (+25.5%) than Ob and lower Ppara (-41.5%) and Cpt1a (-62.4%) than C, indicating impaired lipid metabolism. Inflammatory markers Pycard (+27.5%), Nek7 (+29.5%) and Casp1 (+26.8%) were higher in WC than Ob, whereas Nlrp3 was higher in Ob (+44.7%). Tnfa, Mcp1, Il1b and Il18 gene expression was similar between WC and Ob. Transmission electron microscopy revealed mitochondrial and rough endoplasmic reticulum (RER) alterations, nuclear chromatin condensation, and reduced RER cisternae in WC, consistent with correlated genes. Fission markers Fis1 (+18.1%), Mff (+30.2%), and Drp1 (+27.7%) were higher in WC than Ob, while fusion markers Mfn2, Opa1, and Ppargc1a were similar. ER stress markers Bip (+56.9%), Atf4 (+24.3%), and Chop (+33.9%) were increased in WC vs. Ob. Overall, WC induced metabolic and molecular alterations involving lipid metabolism, inflammation, mitochondrial dysfunction, and ER stress, suggesting greater hepatic impairment than continuous obesity and favoring MASLD progression.