Aim. Adiponectin has demonstrated anti-inflammatory and insulin sensitising properties, and low circulating levels may be an important risk factor for diabetes. We examined levels of adiponectin and its insulin-sensitising HMW isoform and their relationship with metabolic parameters in Tongans, a population prone to type II diabetes. Methods. Adiponectin and its HMW isoform were quantitated by Elisa in specimens from a randomly recruited, multistage cluster population survey of Tongans and from a group of Caucasians. Anthropometric, clinical, and biochemical data were collected on each subject. Results. Both male and female Tongans had lower levels of total and HMW adiponectin than their Caucasian counterparts. Levels of total and HMW adiponectin were higher in females than males in each group. Adiponectin levels were inversely related to BMI, weight, and HOMA in Tongan males and females, as well as to dyslipidemia in both sexes. Conclusion. Tongans had lower levels of both total and HMW adiponectin than Caucasians population, even after matching Tongans to their Caucasian counterparts based on BMI, age, and sex. These findings may reflect differences in body composition between the populations not adequately assessed by BMI, lifestyle factors, or a genetic variant likely in a genetically homogenous population. 1. Introduction Insulin resistance is a major risk factor for type II diabetes and commonly associated with obesity and a high fat diet. The adipose-specific glycoprotein adiponectin, one of several adipokines produced by adipose tissue, promotes insulin sensitivity, protects against atherosclerosis, and has anti-inflammatory properties [1]. Adiponectin’s HMW isomer is the most important correlate of insulin sensitivity [2], and mutant forms of adiponectin unable to form HMW species are associated with diabetes in man [3]. Adiponectin has also been shown to activate different pathways in vitro according to its oligomeric state [4], while the two receptors for adiponectin, adiponectin receptor 1 (AdipoR1) and AdipoR2, display differing functionalities [5]. In mice, simultaneous disruption of both receptors abolished adiponectin binding and resulted in increased levels of tissue triglyceride, inflammation, insulin resistance, and marked glucose intolerance [6] demonstrating the important role for adiponectin in the regulation of glucose and lipid metabolism. Levels of adiponectin are decreased in the obese, those with coronary artery disease, and in type II diabetes [1]. The Tongan population is an ideal group to examine the pathophysiology of
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