Insulin Resistance and Vascular Dysfunction in Nondiabetic Asian Indians

Abstract

Asian Indians are at higher risk for diabetes and cardiovascular disease than European Caucasians. To examine the pathophysiology of this increased risk, we measured insulin sensitivity, cardiovascular risk factors, fat distribution, and endothelium-dependent (reactive hyperemia) and -independent (nitroglycerin) vasodilation before and after a 2-h hyperinsulinemic clamp (40 mU/m(2).min) in 25 nondiabetic Asian Indians and 15 Caucasians with similar age and body mass index. Asian Indians had higher fasting insulin than Caucasians (6.7 +/- 0.8 vs. 3.7 +/- 0.3 microU/ml, P = 0.007) but similar FPG (90 +/- 2 vs. 88 +/- 2 mg/dl). Glucose uptake during the clamp was markedly reduced in Asian Indians vs. Caucasians (4.5 +/- 0.3 vs. 7.5 +/- 0.4 mg/kg x min, P < 0.0001). During the clamp, basal brachial artery diameter increased less in Asian Indians vs. Caucasians (2.6 +/- 1.0 vs. 5.7 +/- 1.0%, P = 0.04), and the reduction was correlated with the impairment in insulin sensitivity (r = 0.38, P = 0.04). In contrast, vasodilatory responses to reactive hyperemia and nitroglycerin were similar in Asian Indians and Caucasians both before and during hyperinsulinemia. Plasminogen activator inhibitor-1 and FFA were significantly elevated and adiponectin was significantly lower in Asian Indians vs. Caucasians, and there were trends toward higher low-density lipoprotein and triglycerides, lower high-density lipoprotein, and increased total, sc, and visceral fat. These risk factors were all significantly correlated with insulin sensitivity. Thus, apparently healthy Asian Indians have severe insulin resistance, dyslipidemia, elevated plasminogen activator inhibitor-1, impaired insulin-mediated vasodilation, and trends toward altered body fat distribution. These abnormalities may contribute to the increased risk of diabetes and cardiovascular disease in this population.

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

“…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.…”

Cold-induced activity of brown adipose tissue in young lean men of South-Asian and European origin

“…To overcome any order bias 18 F-FDG PET-CT and 123 I-MIBG SPECT-CT were performed in random order. Furthermore, as healthy South Asians are less insulin sensitive than their European counterparts at a given BMI and age [11], and insulin sensitivity might influence BAT activity [12], we performed hyperinsulinaemic-euglycaemic clamps to assess insulin sensitivity in both ethnic groups. The institutional ethics committee of the Academic Medical Center approved the study protocol and all participants provided written informed consent.…”

Born with low birth weight in rural Southern India: what are the metabolic consequences 20 years later?

“…Furthermore, the Indian patient with type 2 diabetes (T2D) tends to be diagnosed a decade earlier, is characterised by a lower body mass index (BMI) and is more centrally obese when compared with patients of Caucasian origin (3). Additionally, non-diabetic south Asians are more insulin resistant (4,5) and have an adverse fat distribution with more abdominal, hepatic and intramyocellular fat (6, 7) when compared with those from other ethnic groups with a similar BMI.…”