Supplemental lipoic acid relieves post-weaning diarrhoea by decreasing intestinal permeability in rats

Lipoic acid (LA) is a naturally existing substance which widely distributed in the cellular membranes and cytosol of animal cells. Its intracellular functions include quenching of free radicals and repairing oxidized proteins. The purpose of this study was to evaluate the effects of LA on post-weaning diarrhoea using a rat model. Sixty weaned rats were fed either a basal diet or a LA-supplemented diet, or a zinc oxide (ZnO)-supplemented diet as a positive control. Rats in the LA and ZnO groups had better performance and reduced incidence of diarrhoea (p < 0.05). Both LA and ZnO treatments enhanced intestinal homeostatic and architecture, significantly decreased urinary lactulose to mannitol ratios (p < 0.05) and increased the expression of the intestinal mucosal tight junction proteins occludin (OCLN) and zonula occludens protein-1 (ZO-1) (p < 0.05). LA significantly increased the activities of antioxidant enzymes, and reduced glutathione while decreasing the levels of oxidative glutathione and malondialdehyde in the intestinal mucosa (p < 0.05). Furthermore, an in vitro study indicated that supplementation with LA in IEC-6 intestinal epithelial cells significantly enhanced the expression of OCLN and ZO-1 under hydrogen peroxide-induced oxidative stress. Collectively, these results suggest that LA relieves post-weaning diarrhoea by reducing intestinal permeability and improving antioxidant indices.