Glycerol monolaurate reduces lipid deposition and promotes the health of liver and intestine in grass carp fed with high-fat diet

Abstract

This study explores the improving impact of glycerol monolaurate (GML) on lipid accumulation, liver and intestinal inflammation, and intestinal microbiota imbalance of grass carp caused by high-fat diet (HFD). Grass carp were provided with regular diet (RD) and HFD containing 0, 0.5, 1, 2 and 4 g/kg of GML for 11 weeks. The results show that 1, 2 and 4 g/kg of GML alleviated the HFD-induced increase in triglyceride content of liver (P < 0.05), and reduced the adipocyte size (P < 0.05) and the lipid droplet number in the liver. Moreover, GML markedly reduced the mRNA expression of lipid synthesis-related genes (acc1) and 4 g/kg of GML markedly up-regulated the mRNA expression of lipolysis-related genes (atgl, hsl, and cpt1) in the liver (P < 0.05), and 4 g/kg of GML markedly up-regulated the mRNA expression of atgl and hsl in the intraperitoneal fat (P < 0.05), thereby alleviating the lipid accumulation induced by HFD. In addition, GML inhibited the mRNA expression of pro-inflammatory factors (il-6), and 2 and 4 g/kg of GML promoted the mRNA expression levels of anti-inflammatory factors (tgf-β1) in the liver (P < 0.05), thus alleviating liver inflammation caused by HFD. The 2 and 4 g/kg of GML significantly inhibited the mRNA expression of pro-inflammatory factors (tlr4 and nf-κb p65), and 1, 2 and 4 g/kg of GML significantly promoted the mRNA expression levels of tight junction proteins (claudin-3 and occludin) in the intestine (P < 0.05), thus alleviating the inflammation and injury of the intestine caused by HFD. Particularly, GML also normalized HFD-induced intestinal microbiota imbalance in grass carp, which was characterized by promoting the growth of beneficial bacteria (e.g., Cetobacterium) and inhibiting the harmful bacteria growth (e.g., Erysipelatoclostridium) in the intestine. To sum up, GML supplementation can alleviate HFD-induced lipid accumulation, inflammation and intestinal microbiota imbalance, and improve the health of liver and intestine in grass carp.