Low methyl-esterified pectin induces abnormal hepatic lipid deposition in largemouth bass, Micropterus salmoides

Abstract

A 56-day trial investigated the influences of different methyl-esterified pectin on the digestive enzyme activity, lipid metabolism, gut and hepatic morphology, and growth of largemouth bass. Four practical diets with 13.7% crude lipids and 42.5% crude protein were formulated to contain 8% cellulose, two different methyl-esterified pectins (10.9% and 72.3% esterification degree, LMP and HMP), and mixed pectin (MMP, 50% LMP + 50% HMP). Results showed that dietary pectin inclusion has no detrimental influences on fish growth and feed utilization, and upregulated the expression of hepatic lipid synthesis and metabolism-related genes. Specifically, dietary HMP increased intestinal Na+/K+-ATPase and AKP activities, crypt depth, and growth of largemouth bass, whereas dietary LMP increased serum ALT activity and hepatic lipid content. In summary, dietary LMP led to abnormal hepatic lipid deposition by up-regulating the expression of hepatic lipogenesis and lipolysis-related genes, and ultimately induced hepatic impairment in largemouth bass. Conversely, dietary HMP exhibited a growth-improvement effect by improving digestive enzyme activity and intestinal digestive physiology. Our data demonstrated that HMP has better application value than LMP in the aquaculture industry.