Dietary lecithin attenuates adverse effects of high fat diet on growth performance, lipid metabolism, endoplasmic reticulum stress and antioxidant capacity in the intestine of largemouth bass (Micropterus salmoides)

This study was conducted to investigate the effects of dietary lipid and lecithin levels on growth performance, lipid metabolism, endoplasmic reticulum stress and antioxidant capacity in intestinal tissues of largemouth bass (Micropterus salmoides). Five experimental diets include the control (10.67 % lipid, normal dietary lipid without extra lecithin addition), 1.0 g/kg lecithin diet with normal dietary lipid level (Lec diet, 10.94 % lipid), high fat diet without extra lecithin addition (HFD, 18.65 % lipid), and HFD supplemented with 1.0 g/kg and 2.0 g/kg lecithin (HFD + Lec1 and HFD + Lec2 diets, respectively). Largemouth bass (initial body weight: 5.39 +/- 0.04 g/fish) were fed five diets for 10 weeks. Dietary lecithin alleviated the growth retardation and intestinal damage induced by HFD. HFD-induced increase of whole body and intestinal crude lipid contents and decline of intestinal poly-unsaturated fatty acids content were also alleviated by dietary lecithin addition. Dietary lecithin alleviated the increase of TG content, activities of lipogenic enzymes (G6PD, 6PGD, ME, ICDH and FAS), mRNA expression of lipogenic genes ( g6pd, 6pgd, fas, acc alpha, dgat1, dgat2 and srebp1) and protein expression of Srebp1, and down- regulation of mRNA expression of lipolytic gene cpt1) ) and protein expression of Ppar alpha induced by HFD. Lecithin addition mitigated the up-regulation of mRNA expression of lipid absorption genes (fabp2, fatp4, sr-1b and npc1l1), and the down-regulation of mRNA expression of chylomicron assembly- and secretion-relevant genes (mttp and acat2) and proteins (Mttp, Apob and Sar1b), chylomicron components (TG, phosphatidylcholine and apolipoprotein) and MTTP activity induced by HFD. Compared with HFD, HFD + Lec1 diet significantly decreased the mRNA expression of endoplasmic reticulum (ER) stress genes (grp94, grp78, calr, chop, ire1 alpha and xbp1) and Grp78 protein expression. Compared with HFD, the activities of antioxidant enzymes (CAT, T-SOD and GPx) and mRNA expression of genes (sod1, cat, gpx1 and nrf2) were significantly increased but MDA content and keap1 mRNA expression were significantly decreased in HFD supplemented with 1.0 g/kg and 2.0 g/kg lecithin. These results indicated that dietary lecithin supplementation increased growth rate, improved lipid metabolism, relieved ER stress, and enhanced antioxidant capacity, thereby alleviating negative effects of HFD on the function and health of intestinal tract of largemouth bass.