Jiangzhi Capsule improves fructose-induced insulin resistance in rats: Association with repair of the impaired sarcolemmal glucose transporter-4 recycling

Abstract

Ethnopharmacological relevanceJiangzhi Capsule, originated from an experienced formula in traditional Chinese Medicine, has been listed and used for the management of metabolic abnormalities in Australia for a long time. To better understand Jiangzhi Capsule, this study investigated its effect on insulin resistance. Materials and methodsMale rats were treated with liquid fructose in their drinking water over 14 weeks. Jiangzhi Capsule was co-administered (once daily, by oral gavage) during the last 7 weeks. Indexes of lipid and glucose homeostasis were determined enzymatically, by ELISA and/or histologically. Gene expression was analyzed by real-time PCR, Western blot and/or immunohistochemistry. ResultsTreatment with Jiangzhi Capsule (100mg/kg) attenuated fructose overconsumption-induced increases in basal plasma insulin concentrations, the homeostasis model assessment of insulin resistance index and the adipose tissue insulin resistance index in rats. The increased plasma glucose concentrations during oral glucose tolerance test were also inhibited. Furthermore, Jiangzhi Capsule had a trend to attenuate the decreased ratios of glucose and non-esterified fatty acids to plasma insulin concentrations. Mechanistically, this insulin-sensitizing action was accompanied by normalization of the downregulated sarcolemmal glucose transporter (GLUT)-4 protein expression and the decreased phosphorylated Akt to total Akt protein ratio in gastrocnemius. ConclusionsThese results suggest that Jiangzhi Capsule ameliorates fructose-induced insulin resistance with a link to repair of the impaired sarcolemmal GLUT-4 recycling through modulation of the ratio of phosphorylated Akt to total Akt in gastrocnemius. Our findings provide an evidence-based and mechanistic understanding of Jiangzhi Capsule for the management of insulin resistance-associated disorders.