Structural and morphological features of the liver in the development of metabolically associated steatotic liver disease under conditions of experimentally induced obesity

Abstract

Metabolically associated steatotic liver disease (MASLD) represents a spectrum of liver pathology driven by obesity and metabolic dysregulation. The present study aimed to evaluate the structural and morphological liver changes during MASLD development under experimentally induced obesity. A prospective controlled experiment was conducted on 24 sexually mature outbred male white rats randomized into experimental (n=12) and control (n=12) groups. The experimental group received a hypercaloric high-fat diet (60% fat, 1% cholesterol) for 12 weeks, while controls were maintained on a standard diet. Body weight was monitored weekly. Liver tissue was collected at 4, 8, and 12 weeks for histological analysis using hematoxylin and eosin. Steatosis (grade 0–3), inflammatory activity (0–3), ballooning degeneration, and fibrosis stage (METAVIR) were assessed by two blinded morphologists. Serum ALT, AST, total cholesterol, triglycerides, and glucose levels were measured. By week 12, experimental animals demonstrated significant weight gain compared to controls (p<0.01), hepatomegaly, and macroscopic features of fatty infiltration. Histologically, early microvesicular steatosis at week 4 progressed to predominant macrovesicular steatosis with lobular inflammation and ballooning degeneration by week 12. Steatosis grade was significantly higher in the experimental group (2.4±0.5 vs 0.3±0.2, p<0.001), accompanied by early perisinusoidal fibrosis (METAVIR F1–F2). Biochemical analysis revealed elevated transaminases, dyslipidemia, and hyperglycemia, correlating with morphological severity. The findings confirm that prolonged high-fat, cholesterol-enriched feeding induces progressive metabolic and structural liver remodeling consistent with MASLD, providing a translationally relevant experimental model for pathogenetic and therapeutic research.