Soy ß-conglycinin improves glucose uptake in skeletal muscle and ameliorates hepatic insulin resistance in Goto-Kakizaki rats.

Although the underlying mechanism is unclear, ß-conglycinin (ßCG), the major component of soy proteins, regulates blood glucose levels. Here, we hypothesized that consumption of ßCG would normalize blood glucose levels by ameliorating insulin resistance and stimulating glucose uptake in skeletal muscles. To test our hypothesis, we investigated the antidiabetic action of ßCG in spontaneously diabetic Goto-Kakizaki (GK) rats. Our results revealed that plasma adiponectin levels and adiponectin receptor 1 messenger RNA expression in skeletal muscle were higher in ßCG-fed rats than in casein-fed rats. Phosphorylation of adenosine monophosphate-activated protein kinase (AMP kinase) but not phosphatidylinositol-3 kinase was activated in ßCG-fed GK rats. Subsequently, ßCG increased translocation of glucose transporter 4 to the plasma membrane. Unlike the results in skeletal muscle, the increase in adiponectin receptor 1 did not lead to AMP kinase activation in the liver of ßCG-fed rats. The down-regulation of sterol regulatory element-binding factor 1, which is induced by low insulin levels, promoted the increase in hepatic insulin receptor substrate 2 expression. Based on these findings, we concluded that consumption of soy ßCG improves glucose uptake in skeletal muscle via AMP kinase activation and ameliorates hepatic insulin resistance and that these actions may help normalize blood glucose levels in GK rats.