Astragaloside IV Mediates the PI3K/Akt/mTOR Pathway to Alleviate Injury and Modulate the Composition of Intestinal Flora in ApoE ^-/- Atherosclerosis Model Rats

Abstract

Background: Atherosclerosis (AS) is a chronic inflammatory vascular disease with a complex pathogenesis. Astragaloside IV (AST IV), the primary active component of Astragalus, possesses anti-inflammatory, antioxidant, and immunomodulatory properties. This research aims to investigate the outcome of AST IV on AS and its potential molecular mechanism. Methods: A high-fat diet (21% fat, 50% carbohydrate, 20% protein, 0.15% cholesterol, and 34% sucrose) was utilized to feed Apolipoprotein E deficient (ApoE^-/-) SD rats for 8 weeks, followed by continuous intragastric administration of AST IV for 8 weeks. Biochemical detection was conducted for serum lipid levels and changes in vasoactive substances. After Masson staining, aortic root oil red O staining, and Hematoxylin Eosin (HE) staining, the efficacy of AST IV was verified using quantitative reverse transcription polymerase chain reaction (qRT-PCR). The mRNA expression levels of inflammatory factors and endothelial dysfunction-related biomarkers in rat aortic root tissues were appraised. The changes in the composition of intestinal flora in rats after AST IV treatment were appraised using Image J (Multi-point Tool). Western blot was used to evaluate phosphatidylinositol-3-kinase/protein kinase B/mammalian target of rapamycin (PI3K/Akt/mTOR) pathway-related protein levels in rat aortic root tissues. Results: AST IV administration alleviated the pathological symptoms of AS rats. AST IV administration reduced serum total cholesterol (TC), triglycerides (TG), low-density lipoprotein cholesterol (LDL-C), endothelin-1 (ET-1) and angiotensin (Ang)-II (Ang-II) levels, and augmented serum high-density lipoprotein cholesterol (HDL-C) and nitric oxide (NO) levels. At the same time, AST IV administration inhibited the levels of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), IL-1β, vascular cell adhesion molecule-1 (VCAM-1), matrix metalloproteinase-2 (MMP-2), macrophage inflammatory protein-1 (MCP-1), and intercellular adhesion molecule-1 (ICAM-1) in the aortic root tissue of AS rats. In addition, the intestinal flora changed significantly after AST IV administration. The number of Bifidobacterium, Lactobacillus, and Bacteroides augmented significantly, and <i>Enterobacter</i>, <i>Enterococcus</i>, <i>Fusobacterium</i>, and <i>Clostridium</i> significantly decreased. Mechanistically, AST IV administration inhibited the phosphorylation of PI3K, Akt, and mTOR in AS rats. When combined with Dactolisib (BEZ235) (a PI3K/Akt/mTOR pathway inhibitor), AST IV could further inhibit phosphorylation and reduce inflammation. Conclusion: AST IV has a potential anti-AS effect, which can improve the pathological changes of the aorta in ApoE^-/- rats fed with a high-fat diet, reduce the level of inflammatory factors, and modulate the composition of intestinal flora via the PI3K/Akt/mTOR pathway.

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