Alterations of liver histology and blood biochemistry in blunt snout bream Megalobrama amblycephala fed high-fat diets

In this study we examined the effects of high-fat diets on alterations in liver histology features and blood biochemistry parameters in blunt snout bream Megalobrama amblycephala. Fish were fed three diets containing 5, 10, and 15 % fat, respectively, for 6 weeks prior to the liver histology examination and blood biochemistry testing. The livers of fish fed the 5 % fat diet showed a normal structure, whereas those of the fish fed the diets with a higher fat content presented nucleus polarization and lipid vacuolization. Transmission electron microscopy examination revealed that the hepatocytes of fish fed the 15 % fat diet had undergone ultrastructural alterations involving the mitochondria, nucleus, and endoplasmic reticulum (ER). Alterations in the blood biochemistry were evaluated to determine whether the blood biochemistry changes could be correlated with the observed alterations in liver histology with the aim of assessing the suitability of the investigated blood parameters as rapid indicators of liver condition. Significantly higher levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activities and of triglycerides and cholesterol were found in fish fed the 15 % fat diet. On the whole, the results clearly show that high fat intake resulted in fat accumulation and ultrastructural impairments of the mitochondria, nucleus, and ER. We conclude that blood sample measurements (AST, ALT, triglycerides, and cholesterol) could be used as a rapid test for determining liver status in blunt snout bream.