Inducing adipocyte hyperplasia improves growth performance, alleviates hepatic steatosis and counteracts muscle quality deterioration in largemouth bass (Micropterus salmoides) fed with high-carbohydrate diet.

High-carbohydrate diet (HCD) is commonly used in aquaculture to reduce feed costs, but its use in carnivorous fish is constrained by the low carbohydrate tolerance of these species. Recent studies in herbivorous grass carp have shown that promoting adipocyte hyperplasia shifts adipose tissue expansion from pathological hypertrophy to healthy hyperplasia, thereby improving carbohydrate tolerance. However, whether this strategy is equally effective in carnivorous fish remains unknown. In this study, we fed largemouth bass (Micropterus salmoides) with a control diet, an HCD, or HCD supplemented with 30, 60, or 90 mg/kg rosiglitazone, a PPARγ agonist that induces adipocyte hyperplasia, for 8 weeks. The results showed that promoting adipocyte hyperplasia enhanced glucose-to-lipid conversion and lipid storage capacity in adipose tissue, and also increased lipid catabolism, thereby reducing abdominal fat accumulation. Consequently, rosiglitazone improved serum metabolic parameters, as reflected by lower levels of glucose, ALT, AST, and pro-inflammatory cytokines Il-8 and Il-1β (P < 0.05). In addition, promoting adipocyte hyperplasia alleviated hepatic steatosis by reducing hepatic glucose-to-lipid conversion, and promoted muscle fiber development and enhanced the metabolic capacity of muscle for glucose and lipids. Ultimately, the improved carbohydrate tolerance restored growth performance and reversed muscle texture deterioration, as evidenced by increased chewiness and gumminess and normalized adhesiveness. These findings demonstrate that promoting adipocyte hyperplasia effectively counteracts HCD-induced growth suppression, hepatic steatosis and flesh quality deterioration in carnivorous largemouth bass, providing a promising strategy to improve carbohydrate utilization in carnivorous fish aquaculture.