Effects of dietary betaine on cholesterol metabolism and hepatopancreas function in gibel carp (Carassius gibelio) fed with a high-fat diet

This research aimed to investigate the role of dietary betaine in high-fat diet in cholesterol metabolism in gibel carp. Fish were randomly allocated to five groups and fed with basic diet, high-fat diet and high-fat diet with 1 g/kg, 4 g/kg and 16 g/kg betaine, respectively. The feeding trial lasted 10 weeks. The results showed that though betaine addition decreased fish final body weight, it alleviated lipid metabolism disorder caused by high-fat diet according to serum TC, TG, LDLC and HDLC levels. More importantly, betaine supplementation enhanced cholesterol synthesis as well as conversion of cholesterol to bile acid by promoting expression of HMGCR and CYP7A1 genes. Meanwhile, betaine supplementation not only promoted bile acid efflux and increased total bile acid level in the intestine but also improved intestinal lipase activity. Moreover, high-fat diet with betaine addition improved the hepatopancreas' antioxidant capacity, lessened hepatopancreas injury and increased fish survival during the feeding trial and under bacterial challenge. In summary, dietary betaine supplementation was beneficial to alleviate high-fat feeding-induced lipid metabolism disorder, promote cholesterol conversion to bile acid and enhance hepatopancreas function in gibel carp.