Fucoidan isolated from the sea cucumber Acaudina molpadioides improves insulin resistance in adipocytes via activating PKB/GLUT4 pathway

Abstract

Fucoidan was extracted from the sea cucumber Acaudina molpadioides (Am-FUC), and its effect of improving insulin resistance was investigated in vitro and in vivo. Insulin resistance model 3T3-L1 adipocytes were established by treating with 20 ng/ml TNF-α for 24 h. Am-FUC significantly increased the glucose consumption, indicating that Am-FUC improved insulin resistance. Besides, Am-FUC up-regulated PKB/GLUT4 pathway in transcriptional level, enhanced phosphorylation of PI3K and PKB, promoted GLUT4 translocation, which indicated that the pathway was activated. In in vivo experiments, insulin resistance model mice were established by feeding a high-fat high-fructose diet. Am-FUC increased serum insulin level, decreased HOMA-IR, reduced fasting blood glucose level, and improved oral glucose tolerance ability, revealing that Am-FUC can still remit the insulin resistance in vivo. The protein expression levels and phosphorylation of PI3K and PKB in adipose tissue were in keeping with that in 3T3-L1 adipocytes. Combination of Am-FUC and rosiglitazone exerted better effect on improving insulin resistance. These findings suggested that Am-FUC improved the insulin resistance by activating the PKB/GLUT4 pathway.