Background Trachinotus ovatus is a tropical-subtropical marine fish species. In recent years, the aquaculture industry of T. ovatus in China has developed rapidly, with key breakthroughs in breeding and cultivation technologies. However, With the expansion of aquaculture scale and the subsequent increase in feed demand, optimizing feed formulations to reduce production costs has become a crucial approach for enhancing economic returns in aquaculture.

Objective This study investigated the role of G-protein-coupled receptor 43 (GPR43) gene in energy metabolism in T. ovatus.

Methods Based on the GPR43 gene sequence, primers were designed to identify homologs and clone the coding sequence (CDS). Bioinformatics analysis was subsequently employed to investigate the structural characteristics of the gene and its encoded protein. To further elucidate the functional roles, both in vivo and in vitro experiments were conducted. In vivo, the expression levels of GPR43 in ten different tissues of T. ovatus were detected using quantitative real-time polymerase chain reaction (qRT-PCR). Furthermore, the effects of high-sugar feeding and starvation on the expression of this gene in liver and muscle tissues were analyzed. In vitro studies involved isolating primary hepatocytes from T. ovatus liver, which were then subjected to high-sugar and starvation treatments to assess their impact on gene expression.

Results The CDS of T. ovatus GPR43 gene was 1011 bp, encoding 336 amino acids, and it functions as a receptor specifically recognizing short-chain fatty acids. Protein structure analysis revealed that T. ovatus GPR43 trotein contains seven transmembrane domains. Homology analysis indicated that T. ovatus GPR43gene shared high homology with GPR43 gene of the same species (amino acid similarity>86%) and was most closely related to T. anak. In contrast, its homology with mammals was relatively low (amino acid similarity was 50%). Tissue distribution analysis showed that GPR43 gene expression was the highest in the liver, followed by the intestine, brain, and muscle, and the lowest in the skin. In vivo results demonstrated that GPR43 gene expression in the liver and muscle of fish fed a high-glucose diet was generally lower than that in the starvation group. Similarly, in vitro experiments showed that GPR43 gene expression in primary hepatocytes treated with high glucose was lower compared to the starvation group, consistent with the in vivo trend.

Conclusion The results demonstrate that the expression levels of GPR43 gene in the liver and the muscle of T. ovatus are significantly modulated by dietary carbohydrate levels. These findings suggest that GPR43 gene plays a crucial role in sensing energy status and regulating lipid metabolism, thereby serving as a potential biomarker for energy homeostasis in this species. The present study provides significant reference value for reducing feeding costs, controlling body fat content, and improving flesh quality in T. ovatus aquaculture.