High carbohydrate increases amylase, plasma glucose, and gene expression related to glycolysis in giant gourami Osphronemus goramy.

Abstract

The present study elucidated hepatic molecular and physiological responses of giant gourami to high dietary carbohydrates. Two levels of dietary carbohydrate, normal carbohydrate (34%, NC) and high carbohydrate (53%, HC), were offered to the fish for 60days. We evaluated the expression of genes that are related to carbohydrate metabolism, lipogenic capacities, amino acid catabolism, Krebs cycle, and energy sensing. In addition, we also observed the digestive enzyme activities, plasma glucose, glycogen content, whole-body composition, and growth performance of the fish. On day 30 after treatment, fish fed with high dietary carbohydrate level has significantly higher expression of gck, pk, hk, and ldh than the NC group (P < 0.05). In contrast, fish in the HC group had lower expression of irs1, igf-1, sdh, fbp, g6pc, gyp, and ampk compared to the NC fish (P < 0.05). On day 60 of the feeding trial, gck and hk expressions were still higher in the HC group (P < 0.05), and gyp, gdh, and ampk became increasingly expressed in the HC group. The increase of dietary carbohydrates resulted in significant increases in amylase and protease activity, plasma glucose, liver glycogen, crude protein, and lipid contents of the fish whole-body (P < 0.05). The high carbohydrate feeding reduced the fish growth rate but increased feed efficiency and did not affect mortality. In conclusion, giant gourami could utilize high carbohydrates due to a high amylase secretion, high modulation of carbohydrate metabolism, and large glucose storage capacity.