One evidence of mTOR signaling affects Ghrelin to regulate the food intake of Schizothorax prenanti

Mechanistic target of rapamycin (mTOR), an evolutionarily conserved serine/threonine kinase with diverse functions, is expressed ubiquitously in central and peripheral tissues. Recent data strongly implicated mTOR signaling in the regulation of food intake, but the relevant information is still limited in teleost. To reveal the effects of mTOR on food intake in an endemic economic fish in the upper reaches of the Yangtze River, this study firstly cloned the full length cDNA of mTOR in Schizothorax prenanti (S. prenanti) and found its mRNA was widely distributed in various tissues. Rapamycin (1 mg/kg body weight), the specific inhibitor of mTOR, significantly increased the food intake of S. prenanti (P < 0.05), which was accompanied by significantly elevated Ghrelin mRNA levels and had no influence on NUCB2 mRNA levels in the hepatopancreas and intestine (P < 0.05). Whereas L-leucine (10 mg/kg body weight), an activator of mTOR, inhibited the expression of Ghrelin mRNA and stimulated the transcription level of NUCB2 in hepatopancreas and intestine at 4 h post intraperitoneal (i.p.) injection (P < 0.05), but failed to induce a significant decrease in food intake. Collectively, this study provides a novel information on mTOR in the regulation of food intake, which is linked to Ghrelin but not NUCB2 in S. prenanti.