Effect of ChREBP on carbohydrate feeding regulation in mandarin fish Siniperca chuatsi

Carnivorous fish have poor tolerance to carbohydrate in feed and low utilization rate of carbohydrate. Therefore, the balance of carbohydrate and lipids in the nutrient metabolism of carnivorous fish, the effective conversion and utilization of carbohydrate and lipids, and the feedback regulation of feeding are the key links for the efficient utilization of carnivorous fish feed. Carbohydrate response element binding protein (ChREBP) is a new transcription factor found in recent years in the glucose signaling pathway, and can also participate in feeding regulation. We performed in-vivo and in-vitro experiments to reveal the role of ChREBP in the glucose metabolism and feeding in mandarin fish. The mRNA expression of ChREBP and appetite regulatory factors were measured after intraperitoneal injection of glucose in mandarin fish Siniperca chuatsi and cotransfection with glucose and glucose+siRNA in the hypothalamic cells in mandarin fish. The results reveal that at hour 2 and 4 post intraperitoneal injection with 1 mg/g BW glucose, the blood glucose level of the mandarin fish increased significantly, but food intake decreased significantly, and it also displayed a significantly increased ChREBP mRNA expression levels in liver. At hour 4 post injection, hypothalamic ChREBP mRNA level was significantly increased, whereas the mRNA expression levels of appetite genes neuropeptide Y (npy) and agouti-related peptide (AgRP) were decreased significantly. When the glucose concentration was 40 mmol/L, the expression level of ChREBP mRNA in mandarin fish hypothalamic cells was significantly up-regulated, but the expression level of appetite gene npy mRNA was down-regulated. When siRNA and glucose were co-transfected into mandarin fish brain cells, the expression level of chrebp mRNA was significantly decreased, and the appetite gene npy mRNA was significantly increased. The results indicated that glucose regulated food intake through the modulation of appetite gene npy by ChREBP.