Dietary nicotinamide improves growth performance and ameliorates liver lipid profiles by alleviating glycerophospholipid and sphingolipids metabolism in swamp eel (Monopterus albus)

The effect of dietary niacinamide (NAM) on the growth performance and liver lipid metabolism of swamp eel have been poorly investigated. Therefore, a 120-day feeding trial was conducted to provide different levels of NAM in diet and an untargeted lipidome analysis was performed to address this subject. We found that dietary NAM improved the growth performance of swamp eel. It also decreased the contents of glucose and lipids, including glucose, glycogen, TG, and NEFA, as well as fat accumulation in liver, but increased HDL-C content. We speculated that NAM inhibited lipid accumulation in liver by decreasing the key enzyme activity of LPL, HL and LPS. Fatty acid profile analysis showed that the contents of MUFA and PUFA, such as palmitoleic acid, oleic acid, and eicosapentaenoic acid were significantly increased, while the contents of SFA, such as myristic acid, stearic acid, and palmitic acid were decreased in liver by dietary NAM. Lipidome analysis also indicated that the majority of differential lipid metabolites belonged to glycerophospholipids and sphingolipids, which were enriched in the pathways of insulin resistance, adipocytokine signaling pathway, cholesterol metabolism, fat digestion and absorption, lipid and atherosclerosis, and lipid cell lipolysis regulation. These findings gave scientific evidences and novel insights into the metabolic responses to dietary NAM in swamp eel, and provided basic knowledge for using NAM as a feed additive in swamp eel production.