Astragalus Polysaccharide Improves Insulin Sensitivity via AMPK Activation in 3T3-L1 Adipocytes

Abstract

<i>Astragalus</i> polysaccharide (APS) is an important bioactive component of <i>Astragalus membranaceus</i> which is used as an anti-diabetes herb in traditional Chinese medicine. The objective of this study was to investigate the effects and mechanisms of APS on insulin-sensitizing of adipocytes. Mouse 3T3-L1 preadipocytes were used as a model. The results showed that APS increased preadipocytes proliferation in a dose dependent manner, and 0.1 μg/mL APS sufficiently increased Proliferating Cell Nuclear Antigen (PCNA) content (<i>p</i> < 0.01). Moreover, APS enhanced intracellular lipid accumulation and mRNA expression of proliferator-activated receptor γ (PPARγ, <i>p</i> < 0.01), CCAAT/enhancer binding protein α (C/EBPα, <i>p</i> < 0.01) and fatty acid binding protein (<i>a</i>P2, <i>p</i> < 0.01). As expected, corresponding protein contents were elevated. Importantly, APS increased 2-(<i>N</i>-(7-Nitrobenz-2-oxa-1,3-diazol-4-yl)Amino)-2-Deoxyglucose (2-NBDG) uptake (<i>p</i> < 0.01). Meanwhile, both mRNA and protein content of glucose transporter 4 (Glut4) were elevated by APS (<i>p</i> < 0.01). The APS treatment enhanced tyrosine phosphorylation of insulin receptor substrate 1 (IRS1, <i>p</i> < 0.05) and phosphor-Akt content (<i>p</i> < 0.01). Besides, phosphorylated AMP-activated protein kinase (AMPK) content was increased in the APS treated cells (<i>p</i> < 0.01). Taken together, APS improved insulin sensitivity by enhancing glucose uptake, possibly through AMPK activation. These results suggested that APS might be a therapeutic candidate for insulin resistance.