Effects of dietary betaine supplementation on biochemical parameters of blood and testicular oxidative stress in Hu sheep

Abstract

Betaine, a highly valuable feed additive, has been observed to alter the distribution of protein and fat in the bodies of ruminants and to exhibit strong antioxidant properties. However, the effects of dietary betaine supplementation on the biochemical parameters of blood and on testicular oxidative stress remain unknown. This study aimed to investigate the effects of dietary betaine supplementation on lipid metabolism, immunity, and testicular oxidative status in Hu sheep. Experimental sheep (n=3, three sheep per group) were fed betaine-containing diets, a basal diet supplemented with 0 g/day (control group), 1 g/day (B1), and 3 g/day betaine (B2). There were no differences in the serum concentrations of triglycerides and cholesterol in Hu sheep receiving diets supplemented with betaine. The ratio of basophils significantly increased in the B1 and B2 groups. ELISA (enzyme-linked immunosorbent assay) results showed that testicular superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activity were significantly higher, whereas malondialdehyde (MDA) content significantly decreased, after feeding betaine-supplemented diets. qPCR results showed that the mRNA expression levels of CAT, SOD2, and GSH-Px were significantly upregulated in both the B1 and B2 groups compared to those in the control group. Furthermore, the expression of proliferating cell nuclear antigen (PCNA) was significantly lower in the testes of betaine-treated Hu sheep than in the control group. Moreover, LKB1 (liver kinase B1) expression significantly increased, and mRNA expression of AMPK (AMP-activated serine/threonine protein kinase) significantly decreased in the B1 group. The relative gene expression of mTOR (mechanistic target of rapamycin) was significantly higher in the B2 group than in the control group. RAPTOR expression significantly increased in the B1 group. Western blot revealed that the ratio of P-mTOR and mTOR significantly increased after feeding betaine-supplemented diets. In conclusion, betaine supplementation improved serum lipid metabolism, immune response, and increased the testicular antioxidant capacity of Hu sheep, which might be regulated via mTOR signaling pathway.

Keywords: Antioxidant status; Betaine; Hu sheep; mTOR signaling pathway.