Extract from Dioscorea batatas Ameliorates Insulin Resistance in Mice Fed a High-Fat Diet

The aim of this study was to investigate whether Dioscorea balatas (DB) extract attenuates high-fat diet (HFD)-induced insulin resistance in the visceral adipose tissues of mice, and by what mechanism(s). Mice were fed a HFD for 4 weeks to induce the early development of insulin resistance. The DB extract was administered to mice fed a HFD by oral gavage at a dose of 100 mg/kg body weight daily for 7 weeks. Biochemical parameters in blood were measured using enzymatic kits, and the expression levels of glucose transporter 4 (GLUT4), phosphorylated (p-)S6K1, phosphorylated v-akt murine thymoma viral oncogene homolog (p-AKT), and phosphorylated extracellular regulated kinase (p-ERK) in epididymal fat tissue were determined by western blot analyses. The DB extract effectively reversed the HFD-induced elevations in plasma glucose and insulin levels, and the homeostasis mode:. assessment for insulin resistance and oral glucose tolerance test values. The level of p-AKT protein was up-regulated, whereas the levels of p-ERK and p-S6K1 proteins were down-regulated in the adipose tissues of DB mice compared with HFD mice. Furthermore, the DB extract significantly reversed the HFD-induced decrease in the plasma membrane GLUT4 level in the adipose tissue of mice. The DB extract improved glucose metabolism in HFD-fed mice through the up-regulation of plasma membrane GLUT4 content in the visceral adipose tissue. Activation of the insulin signaling cascade leading to GLUT4 translocation was the mechanism underlying the beneficial effects of the DB extract on early-stage obesity-induced insulin resistance.