Intracerebroventricular injection with octanoic acid activates hypothalamic fatty acid sensing systems and regulates appetite in Chinese perch Siniperca chuatsi

There are unique hypothalamic fatty acid (FA) sensing systems in fish that are different from those in mammals. In order to explore the effect of medium-chain FA (MCFA) on the FA sensing systems and appetite regulation, Chinese perch Siniperca chuatsi were subjected to intracerebroventricular (ICV) injection with saline solution alone or saline containing octanoic acid. Food intake of these fish was computed at 2, 4, 6, 12 and 24 h post-treatment, respectively. The transcript levels of genes related to the FA sensing mechanism ( cpt1c , cd36 , pparα and srebp1c ) and hypothalamic neuropeptide ( agrp , npy , pomc and cart ) in the hypothalamus were estimated at 4 h post-treatment. Results showed that at 4 h post-ICV injection with octanoic acid, the food intake of Chinese perch was significantly reduced with the decreasing mRNA level of agrp and the increasing mRNA levels of cd36 and pparα in the hypothalamus. The data indicated that the hypothalamic FA sensing systems of Chinese perch could be activated by octanoic acid, and the underlying mechanism might be that the enhancement of binding ability of FAT/CD36 upregulates the mRNA level of pparα . In addition, with the decrease in the gene expression of agrp , the food intake of Chinese perch was significantly reduced as a result of ICV injection with octanoic acid. These results demonstrated that MCFA might play a key role in central FA sensing and appetite regulation of Chinese perch.