Paraprobiotic and postbiotic forms of Bacillus altitudinis F7 relieved high starch diet-induced growth retardation, glycolipid metabolism disorders and liver damage in Micropterus salmoides

Live host-derived Bacillus altitudinis F7 demonstrated potentials in mitigating the detrimental impacts of high wheat starch diet in largemouth bass ( Micropterus salmoides ), but the possible mechanisms and benefits of its paraprobiotic (heat-inactivated B. altitudinis F7, HIB) and postbiotic (cell-free extract, CE; cell-free supernatant, CS) forms were not yet known. Therefore, C6 (6 % starch diet) and C18 (18 % starch diet) were set as positive and negative controls respectively, and LB (live B. altitudinis F7), HIB, CE and CS were added to 18 % wheat starch diets to investigate their functions on growth performance, glycolipid metabolism, and liver health in an eight weeks feeding experiment in M. salmoides. LB, HIB, CE and CS efficiently alleviated growth suppression caused by high starch diet. LB, HIB, CE and CS improved glycolipid metabolism by activating IRS-1/PI3K/AKT signal pathways, and regulated glycolysis, gluconeogenesis, bile acid synthesis and lipid metabolism. LB, HIB, CE and CS reduced the hepatic mRNA expressions of interleukin-1β ( il-1β ), interleukin-8 ( il-8 ) and tumor necrosis factor-α ( tnf-α ), increased the hepatic interleukin-11β ( il-11β ) mRNA expression, reduced the serum glutamic oxaloacetic transaminase (AST) activity and the hepatic fat deposition, and improved the liver morphology. In conclusion, paraprobiotic (HIB) and postbiotic (CE and CS) forms of B. altitudinis F7 improved growth, glycolipid metabolism, and liver health in M. salmoides fed with high starch diet, among which the paraprobiotic had the better functions. The results provide reference for paraprobiotics and postbiotics application to relieve the detrimental impacts of high starch diet in M. salmoides . • Paraprobiotic and postbiotic forms of B. altitudinis F7 alleviated the growth inhibition of high starch diet . • Paraprobiotic and postbiotic forms promoted the glycolipid metabolism . • Paraprobiotic and postbiotic forms promoted the liver health . • Paraprobiotic form had better potentials compared with postbiotic forms.