[Astragalus polysaccharides improve adipose tissue aging in naturally aged mice via indole-3-lactic acid]

Plant polysaccharides are effective components that widely present in traditional Chinese medicine(TCM), exhibiting rich biological activities. However, as most plant polysaccharides cannot be directly absorbed and utilized by the human digestive system, it is now believed that their mode of action mainly involves interaction with intestinal microbiota, leading to the production of functional small molecules. The efficacy of Astragalus polysaccharide(APS) is extensive, including weight loss, improvement of fatty liver, reduction of blood lipids, and enhancement of insulin sensitivity, which may also be related to the regulation of intestinal microbiota. Adipose tissue senescence is an important characteristic of the physiological aging process in the body, often occurring prior to the aging of other important organs. Its main features include the accumulation of senescent cells and exacerbation of inflammation within the tissue. Therefore, to explore the potential protective effects of APS on aging, the improvement of adipose tissue aging phenotype in naturally aging mice was observed using APS, and combined with metagenomic metabolomics, corresponding microbial metabolic functional molecules were identified. Furthermore, functional tests in cell aging models were conducted. The results showed that APS significantly improved the adipocyte aging characteristics of naturally aging mice: specifically reducing aging-induced adipocyte hypertrophy; decreasing the protein expression of aging markers cyclin-dependent kinase inhibitor p21(P21) and multiple tumor suppressor 1(P16); lowering the tissue inflammation reaction. Metagenomic metabolomic analysis of serum from mice in each group revealed that APS significantly increased the content of indole-3-lactic acid(ILA) in naturally aging mice. Further in vitro studies showed that ILA could improve the aging of 3T3-L1 mouse embryonic fibroblasts induced by bleomycin, reduce the protein expression of the aging marker P21, alleviate inflammation, and enhance the ability of preadipocytes to mature. Therefore, APS had the efficacy of protecting naturally aging mice, and its action may be related to the increase in the intestinal microbiota metabolite ILA. This study suggested that TCM may serve as an important entry point for explaining the mechanism of action of TCM by regulating intestinal microbiota and their functional metabolites.