Effects of P-AKK on glucose and lipid metabolism and immunity of Micropterus salmoides induced by high starch diet

Abstract

As the cheapest energy substance, the carbohydrate exerts a protein-sparing effect in the fish feed. However, excessive dietary carbohydrate intake induces glucose and lipid metabolic dysregulation, intestinal inflammatory responses in teleost. The AKK has been reported that it takes part in regulating glucose and lipid metabolism, inflammatory responses in mammals. However, roles of AKK in teleost remains limited and requires further systematic investigation. In present study, largemouth bass (Micropterus salmoides) was selected as experimental model organism. Following an 8-week culture experiment, the condition factor, triglycerides (TG), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), and glycosylated hemoglobin (GHb) were promoted, while high-density lipoprotein cholesterol (HDLC) was lowered in high starch diet group. Moreover, lipid droplet and glycogen in liver were promoted in high starch diet group. However, the liver fat and glycogen and serum lipid were reduced in the P-AKK supplemental group. In the liver, the mRNA of g-6-pase, fas, and acc-a were significantly inhibited, while the levels of pk and lpl were markedly promoted in P-AKK supplemental group compared with high starch diet and control groups. In the intestinal tissue, the levels of tnf-α, MyD88, il-8, caspase3 and caspase9 were observably inhibited with P-AKK supplemented into diet. Moreover, the TGF-β and IL-10 protein levels were observably elevated, and the TNF-α protein level was dramatically reduced in P-AKK supplemental group compared with high starch diet and control groups. These results demonstrate that P-AKK plays the crucial part in regulating glucose and lipid metabolism and intestinal inflammatory response in largemouth bass.