Creatine supplementation attenuates high-starch-induced hepatic metabolic dysregulation and intestinal barrier dysfunction in largemouth bass (Micropterus salmoides)

A 10-week feeding trial was conducted to investigate the effects of dietary creatine supplementation on growth and enterohepatic health in largemouth bass ( Micropterus salmoides ) under high-starch-induced stress. Juvenile fish (12.00 ± 0.30 g) were distributed into 18 tanks (30 fish/tank) across six dietary groups in triplicate. Diets were isolipidic and isocaloric: a positive control (PC) with 10 % corn starch and 40 % fish meal; a high-starch diet (HSD) with 15 % corn starch and 36 % fish meal; and the HSD supplemented with 0.5 %, 1.0 %, 1.5 %, or 2.0 % creatine (Cr0.5, Cr1.0, Cr1.5, Cr2.0). Results showed that the HSD impaired feed utilization, growth, antioxidant capacity, immunity, liver metabolism, and intestinal barrier function. Compared to the HSD group, the Cr1.0 group significantly improved weight gain rate, specific growth rate, and protein efficiency ratio ( P < 0.05), achieving performance comparable to the PC group ( P > 0.05). Furthermore, Cr1.0 supplementation enhanced intestinal morphology, upregulated the expression of tight junction proteins ( ZO1, Claudin 4, Claudin 1 ) and the anti-apoptotic gene Bcl2, and increased the abundance of beneficial bacteria. Concurrently, it significantly downregulated the endoplasmic reticulum stress pathway genes ( GRP78, PERK, IRE1, ATF6, eIF2α, Chopα ; P < 0.05). In the liver, creatine upregulated anti-inflammatory factors ( Nrf2 , TGFβ1 , IL10 ), glycolytic genes ( PK , PFKL2 , GK ), the β-oxidation gene CPT1 , the anti-apoptotic gene Bag , and the glucose transporter Glut2 ( P < 0.05), while downregulating pro-inflammatory factor TNF-α , gluconeogenesis gene PEPCK , lipogenesis genes ( ACC1 , FASN ), and the pro-apoptotic gene Bad ( P < 0.05). Optimal creatine supplementation (0.92–0.96 %) based on growth and feed utilization effectively repaired intestinal barriers, regulated gut microbiota, alleviated oxidative stress and inflammation, and maintained glucose-lipid metabolism homeostasis in the liver of HSD-fed largemouth bass. • To date, no studies have been conducted to ascertain whether creatine supplementation mitigates liver and intestinal damage caused by high-starch diets (HSDs) in largemouth bass. • High-starch diets (HSDs) with 0.92 %-0.96 % creatine reduced fish meal usage from 40 % to 36 % without affecting growth. • HSDs with 1.0 % creatine might reduce intestinal oxidative damage induced by high-starch diet by lowering endoplasmic reticulum stress, repairing the intestinal barrier by regulating the expression of tight junction proteins, and modulating intestinal microbial homeostasis. • HSDs with 1.0 % creatine might mitigate hepatic metabolic disorders and inflammatory responses induced by high-starch diet through regulation of glycolytic pathways and lipid metabolism, thereby reducing abnormal hepatic lipid accumulation and cell apoptosis while improving glucose homeostasis and liver health in the organism. • The findings may provide a theoretical foundation for the development of more rational additive strategies with the objective of enhancing fish health.