Dietary starch levels modulate growth performance, glucose utilization, and lipogenesis in mandarin fish (Siniperca chuatsi)
摘要
The study investigated how varying levels of dietary starch influence the growth, health status, and glucose-lipid metabolism of mandarin fish (initial body weight: 106 ± 1 g). Five diets containing graded levels of digestive starch were formulated (6.56%, 9.03%, 13.03%, 16.46%, and 19.57%), designated as D6.56, D9.03, D13.03, D16.46, and D19.57, respectively. Each diet was administered to triplicate groups of mandarin fish twice daily over 8 weeks. Results showed that growth performance increased linearly, peaking in the D13.03 group starch level before declining (P < 0.05). Liver and muscle lipid content and hepatic glycogen increased significantly in a quadratic and linear manner, respectively (P < 0.05). Transcriptional analysis revealed a starch-dependent upregulation of insulin signaling (ira, pi3kr1, and akt1) and glycolysis (gk, pfkl, and pk) genes, with concurrent downregulation of gluconeogenesis (fbp1 and g6pc) (P < 0.05). Protein expression analysis showed the ratio of p-PI3KR1 to PI3KR1 was significantly elevated as dietary starch increased, with the D13.03 group showing higher ratios than the D19.57 group (P < 0.05). FoxO1 expression was decreased in high-starch groups and reached a peak in the D13.03 group, while the phosphorylation of FoxO1 was significantly elevated (P < 0.05). Additionally, ChREBP and SREBP-1 protein levels were elevated in the D13.03 and D19.57 groups compared to the D6.56 groups (P < 0.05). In conclusion, mandarin fish showed superior carbohydrate tolerance with optimal growth at 13.03% dietary starch, which was partly due to the superior capacity to convert carbohydrates into triglycerides.