Ethnic Variation in Adiponectin and Leptin Levels and Their Association With Adiposity and Insulin Resistance

Abstract

OBJECTIVETo investigate ethnic differences in adiponectin and leptin concentration and to determine whether these adipokines and a high–glycemic index diet account for ethnic variation in insulin resistance.RESEARCH DESIGN AND METHODSIn 1,176 South Asian, Chinese, Aboriginal, and European Canadians, fasting blood samples were drawn, and clinical history and dietary habits including glycemic index/glycemic load were recorded using standardized questionnaires. Insulin resistance was defined using homeostasis model assessment–insulin resistance (HOMA-IR).RESULTSAdiponectin concentrations were significantly higher in Europeans (adjusted mean 12.94 [95% CI 2.27–13.64]) and Aboriginal people (11.87 [11.19–12.59]) than in South Asians (9.35 [8.82–9.92]) and Chinese (8.52 [8.03–9.03]) (overall P < 0.001). Serum leptin was significantly higher in South Asians (11.82 [10.72–13.04]) and Aboriginal people (11.13 [10.13–12.23]) than in Europeans (9.21 [8.38–10.12]) and Chinese (8.25 [7.48–9.10]). BMI and waist circumference were inversely associated with adiponectin in every group except the South Asians (P < 0.001 for interaction). Adiponectin was inversely and leptin was positively associated with HOMA-IR (P < 0.001). The increase in HOMA-IR for each given decrease in adiponectin was larger among South Asians (P = 0.01) and Aboriginal people (P < 0.001) than among Europeans. A high glycemic index was associated with a larger decrease in adiponectin among South Asians (P = 0.03) and Aboriginal people (P < 0.001) and a larger increase in HOMA-IR among South Asians (P < 0.05) relative to that in other groups.CONCLUSIONSSouth Asians have the least favorable adipokine profile and, like the Aboriginal people, display a greater increase in insulin resistance with decreasing levels of adiponectin. Differences in adipokines and responses to glycemic foods parallel the ethnic differences in insulin resistance.

Can body fat distribution, adiponectin levels and inflammation explain differences in insulin resistance between ethnic Chinese, Malays and Asian Indians?

“…44 In a Canadian study, Chinese had lower adiponectin levels than whites in both men and women after adjusting for waist circumference. 3 In our study, we found a higher degree of insulin resistance and unfavorable metabolic profiles in Malays as compared with Chinese, whereas Malays were less insulin resistant as compared with Asian Indians. Ethnic Malays represent millions of people from different Southeast Asian Island populations including Malaysians, Filipinos and Indonesians who are experiencing a rapid increase in chronic disease burden.…”

“…28 Differences in adipocyte cell size 31 and a higher ratio of total body fat to lean mass 27 have also been suggested to contribute to greater insulin resistance in Asian Indians. Furthermore, Asian Indians have been shown to have a lower adiponectin levels 3,24,26,29,30,36 and higher CRP levels 30,32,37 as compared with whites independent of BMI. In addition, dietary factors may contribute to the higher susceptibility of Asian Indians to developing type 2 diabetes.…”

“…2 Insulin resistance is closely associated with type 2 diabetes mellitus (T2DM) and marked differences in insulin resistance have been observed between ethnic groups. 3 Asians, and particularly Asian Indians, have been shown to be more insulin resistant for a given degree of adiposity as compared with whites. 4 Substantial differences in insulin resistance may also exist between ethnic groups in Asia, with Asian Indians having worse insulin resistance and glucose tolerance than Chinese and Malays.…”

Circulating lipopolysaccharide-binding protein (LBP) as a marker of obesity-related insulin resistance

“…18 Otherwise, the strong circulating LBP reduction after fat mass loss opens new perspectives. The decrease in LBP concentration after weight loss ran in parallel with the decrease in leptin concentration, a protein produced mainly in adipocytes that circulates in proportion with body fat mass, 28 and with the decrease of complement factor B concentration, which has been reported to be expressed in human adipose tissue and adipocytes. 18 Further studies are necessary to explore these fascinating relationships.…”

Ethnic differences in BMI, subcutaneous fat, and serum leptin levels during and after pregnancy and risk of gestational diabetes

“…Serum leptin (s-leptin) levels reflect the proportion of adipose tissue in the body (13), is highly correlated with fat mass (14), and correlates particularly with subcutaneous fat in women (14,15). Several studies have observed higher s-leptin levels in individuals of South Asian than European descent for the same BMI (16,17), suggesting that BMI may be a poor indicator of adiposity in South Asians. Leptin levels increase in pregnancy, due to production by the placenta, and decline rapidly after delivery (18).…”