Probiotic supplementation affects IGF-1 and leptin levels in Nile tilapia hepatopancreatic tissue

ABSTRACT This work aimed to assess the effect of the probiotic strain, Lactobacillus plantarum, on the levels of leptin, IGF-1 and their receptors on the hepatopancreatic tissues of Nile tilapia (Oreochromis niloticus) and then correlate fish growth performance and gut microbiological parameters. Fish juveniles (±23g) were reared in a recirculation system with constant aeration and temperature (25°C). They were distributed into six polyethylene tanks (45L) and fed twice a day at 5% of the tank biomass with the respective diets: control (commercial diet without probiotic) and supplemented with L. plantarum inoculum (1 x 108 CFU mL-1), both in triplicate. After 30 days of feeding, L. plantarum-fed fishes showed greater weekly growth rate, final weight, and feed conversion rate, in addition to higher count of lactic-acid bacteria and lower count of pathogenic bacteria in the intestinal tract, when compared to the control group. The immunostaining intensity for IGF-1 and leptin hormones was lower after L. plantarum supplementation than in the control group, with no change in the level for receptors. This reduction could implicate important changes in fish metabolism and homeostasis.

摘要 本研究旨在评估益生菌菌株植物乳杆菌（Lactobacillus plantarum）对尼罗罗非鱼（Oreochromis niloticus）肝胰脏组织中瘦素（leptin）、胰岛素样生长因子-1（Insulin-like Growth Factor 1，IGF-1）及其受体表达水平的影响，并探究该菌株与鱼类生长性能及肠道微生物学参数之间的相关性。试验选取初始体重约23g的尼罗罗非鱼幼鱼，于持续曝气、温度恒定为25℃的循环养殖系统中饲养。试验分为对照组与处理组，每组设置3个生物学重复；将幼鱼随机分配至6个45L聚乙烯养殖桶中，对照组投喂不含益生菌的商品配合饲料，处理组则在饲料中添加植物乳杆菌接种物（1×10^8 CFU·mL^-1），每日按养殖桶总生物量的5%分两次投喂。投喂30天后，与对照组相比，植物乳杆菌投喂组的尼罗罗非鱼周生长率、终末体重及饲料转化率均显著提升，肠道内乳酸菌数量显著升高，致病菌数量显著降低。植物乳杆菌添加组的肝胰脏组织中IGF-1与瘦素的免疫染色强度低于对照组，而两种激素对应的受体表达水平无显著变化。该激素表达水平的下调可能对鱼类的代谢与生理稳态产生重要调控作用。