Effects of dietary olive leaf extract on intestinal immune-related gene expressions in common carp, Cyprinus carpio

This study aimed to investigate the effects of dietary olive leaf extract (OLE) on intestinal immune-related genes expression of tumor necrosis factor alpha (TNFa), interleukin 1 beta (IL1b), lysozyme (LYS), and mucin2 (MUC2). For this purpose, common carp (~15 g) were fed with 0 (control), 0.1 (OLE-0.1), 0.5 (OLE-0.5) and 1 (OLE-1) % OLE diets for eight weeks. The fish were sampled after one and eight weeks to study intestinal TNFa, IL1b, LYS, and MUC2 gene expressions. The results showed that dietary OLE administration significantly up-regulated intestinal TNFa gene expression after one (all OLE-treated groups) and eight (OLE-0.5) weeks. Moreover, OLE-0.1 and OLE-1 groups showed up-regulated intestinal IL1b expression, after one week, all the OLE-treated fish had significantly higher intestinal IL1b expression, after eight weeks. OLE had no significant effects on LYS gene expression after one week, but OLE-0.1 and OLE-0.5 had significantly higher gene expressions after eight weeks. OLE-0.1 and OLE-1 had significantly lower MUC2 gene expression after one week, but all OLE-treated fish had significantly higher MUC2 gene expression after eight weeks. In conclusion, dietary 0.1-0.5% OLE supplementation is suitable to support common carp intestinal health.