Blueberry Tea Enhances Insulin Sensitivity by Augmenting Insulin-Mediated Metabolic and Microvascular Responses in Skeletal Muscle of High Fat Fed Rats

Abstract

Background: The aim of the current study was to determine whether a unique blueberry tea (BT) ameliorates insulin resistance by improving metabolic and vascular actions of insulin in skeletal muscle. Methods: Male Sprague Dawley rats were fed normal (4.8% fat wt/wt, ND) or high (22.6% fat wt/wt, HFD) fat diets for 4 weeks. A second group of HFD rats was provided BT (4.0% wt/vol) in the drinking water during the final 2 weeks. Animals were subjected to an intraperitoneal glucose tolerance test (1g glucose/kg IPGTT) or euglycaemic hyperinsulinaemic clamp (10mU/min/kg x 2hr). Results: HFD rats displayed significantly (p<0.05) higher plasma glucose levels at 15 and 30 mins following the IPGTT compared to ND, and this increase was completely abolished by BT treatment. Glucose infusion rate, muscle glucose uptake, and microvascular perfusion in muscle were significantly (p<0.05) impaired during clamps in HFD and all markedly improved (p<0.05) with BT treatment. Insulin-mediated changes in femoral artery blood flow were unaffected by HFD or BT treatment. Conclusions: We conclude that BT treatment ameliorates glucose intolerance and insulin resistance by restoring both metabolic and microvascular insulin sensitivity in high fat-fed rats. Therefore, BT consumption may have therapeutic implications for insulin resistance and type 2 diabetes.