Acer truncatum leaves reduce lipid accumulation and improve liver and intestine health of grass carp (Ctenopharyngodon idella) fed with high-fat diet

The purpose of this study was to explore whether Acer truncatum leaves alleviated lipid accumulation, and improved liver and intestine health of grass carp fed with high-fat diet (HFD). Grass carp were fed with regular diet (RD), HFD, HFD contained 2% A. truncatum leaves (HFD_2AL) and 4% A. truncatum leaves (HFD_4AL), respectively, for 8 weeks. Growth performance, serum biochemical indexes, histopathology, expression of genes involved in lipid metabolism, inflammation and tight junctions, and changes in intestinal microbiota of grass carp were detected. Firstly, the results show that adding A. truncatum leaves in HFD reduced liver lipid accumulation of grass carp. The 2% and 4% of A. truncatum leaves reduced the levels of serum total cholesterol (TC) and the amount of lipid droplets in the liver, and down-regulated the expression of lipogenesis-related genes (SREBP-1, PPARγ, ACC1 and FAS), but up-regulated the expression of lipolysis-related genes (CPT-1, LPL and HSL) in the liver of grass carp fed with HFD (P < 0.05). Further, the supplement of A. truncatum leaves in HFD alleviated liver injury of grass carp. The levels of serum aspartate aminotransferase (AST) and alanine transaminase (ALT) were reduced in HFD_4AL group (P < 0.05). And the supplement of A. truncatum leaves reduced the mRNA expression of inflammatory signaling molecules (NF-κB p65 and p38 MAPK) and proinflammatory factors (IL-1β, IL-6, TLR-2 and TLR-4) in the liver of grass carp fed with HFD (P < 0.05). Moreover, the supplement of A. truncatum leaves in HFD enhanced intestine health of grass carp. The 2% and 4% A. truncatum leaves up-regulated the mRNA expression of tight junction proteins (ZO-1) and anti-inflammatory factor (TGFβ1), but suppressed the mRNA expression of proinflammatory factors (IL-1β, IL-6, IL-8, TLR-2, TLR-4 and TNFα) and inflammatory signaling molecules (NF-κB p65) in the intestine of grass carp fed with HFD (P < 0.05). In particular, A. truncatum leaves alleviated intestinal microbiota imbalance caused by HFD, which was characterized by inhibiting the proliferation of harmful bacteria, such as Mycobacterium, but promoting the proliferation of beneficial bacteria, such as Cetobacterium. In summary, the supplement of 2% and 4% of A. truncatum leaves in HFD reduced liver lipid accumulation and inflammation, alleviated intestinal inflammation and microbiota imbalance caused by HFD in grass carp.