Gut microbiota-derived metabolites are involved in intestinal inflammation, which can affect the development of atherosclerotic plaques. Previous studies have shown that oat fiber can delay the progression of atherosclerosis via improving lipid metabolism. The aim of this study was to evaluate how oat fiber acted on gut microbiota-derived metabolites, inhibited intestinal inflammation, and protected the intestinal mucosal barrier.
Male low-density lipoprotein receptor knock-out (LDLR) mice were fed a high-fat/cholesterol diet with or without oat fiber for 14 wk. Histopathology of the aorta was detected by Oil Red O staining, and the small intestine mucosal pathology was measured through hematoxylin and eosin staining. Non-targeted metabolomics of feces was performed using liquid chromatography-mass spectrometry. Western blot method was used to assess the relative levels of the proteins involved in the toll-like receptor (TLR)4 signal pathway and intestinal mucosal barrier in interest tissues.
Pathologically, oat fiber reversed the increment of the atherosclerotic lesion and ameliorated intestinal mucosal barrier in LDLR mice. Oat fiber regulated the levels of gut microbiota-derived metabolites along with a decrease in isobutyrylcarnitine, valerylcarnitine, 1-methylguanosine, and 2-methylguanosine, and an increase in l-tyrosine and niacinamide. Notably, oat fiber blocked the TLR4 signal pathway and decreased the expression of nuclear factor-κB p65 in both the aorta and gut tissues. Also, oat fiber raised the expression of tight junction proteins including ZO-1 and occludin.
Taken together, the present study revealed that oat fiber feeding effectively attenuated the development of atherosclerosis, at least partly via affecting gut microbiota-derived metabolites, inhibiting the intestinal inflammatory response, and maintaining the integrity of the intestinal mucosal barrier.

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