Effects of α-sitosterol on growth, hematobiochemical profiles, immune-antioxidant resilience, histopathological features and expression of immune apoptotic genes of Nile tilapia, Oreochromis niloticus, challenged with Candida albicans

Abstract

In this study, the effect of the Streptomyces misakiensis metabolite (α- sitosterol, 0, 20, 40, 60, and 80 mg/kg) dietary supplementation on growth performance, antioxidant-immune stability and Candida albicans resistance of Nile tilapia was evaluated. The results revealed that the incorporation of α-sitosterol at doses of 60 and 80 mg/kg into the diet significantly improved the growth rate of Nile tilapia. The fish receiving 80 mg/kg showed an increased level of high-density lipoprotein, total protein, globulin, and albumin, and significantly reduced levels of indicators of hepato-renal damage, glucose, triglycerides, low-density lipoprotein, and total cholesterol. Dietary α-sitosterol induced a considerable increase in hepatopancreas glutathione peroxidase, superoxide dismutase and catalase activities and a significant drop in malondialdehyde levels. Supplementing the diet with 80 mg/kg of α-sitosterol increased nitric oxide, complement-3, nitro blue tetrazolium levels, lysozyme, and phagocytic activities. In particular, supplementing with α-sitosterol at 60–80 mg/kg of diet significantly enhanced the expression of pro/anti-inflammatory markers (il1b, il10, tgfb, ifng, tnfa and il8) after the C. albicans challenge. Also, there was a decrease in cumulative mortality percent, pro-apoptotic markers (casp3, bax and hsp70) and an increase in anti-apoptotic indicators (bcl2). Interestingly, following the C. albicans challenge, fish that received 0 and 20 mg α-sitosterol/kg exhibited significant inflammation in the hepatopancreas, spleen, and intestine. On the other hand, inflammation could be alleviated by feeding 60–80 mg α-sitosterol/kg. Due to these findings, α-sitosterol could be an innovative option to enhance growth, general physiological status, immune service, and antifungal resistance of Nile tilapia against C. albicans.