Background: Immigrants from South Asia to Western countries have a high prevalence of type 2 diabetes mellitus (T2DM). We explored pathogenic factors that might contribute to the high risk of T2DM in Pakistani immigrants to Norway.
Methods: A cross-sectional study was performed in 18 Pakistani and 21 Norwegian men and women with T2DM (age 29 - 45 years), recruited from two hospital out-patient clinics. Anthropometrics and a two-step euglycemic, hyperinsulinemic clamp with measurements of non-esterified fatty acids (NEFA) during clamp, was performed in all patients. Insulin sensitivity, given as the Glucose Infusion Rate (GIR) and Insulin Sensitivity Index (ISI), was calculated from the two euglycemic clamp steps. Fasting adipokines and inflammatory mediators were measured. Continuous variables between groups were compared using Student's t test or Mann-Whitney U test as appropriate. Spearman's correlation coefficient and multiple linear regression analyses were used.
Results: Despite having a lower BMI, Pakistani patients were more insulin resistant than Norwegian patients, during both low and high insulin infusion rates, after adjustment for sex and % body fat: median (interquartile range) GIR(low insulin): 339.8(468.0) vs 468.4(587.3) μmol/m2/min (p = 0.060), ISI(low insulin): 57.1(74.1) vs 79.7(137.9) μmol/m2/min (p = 0.012), GIR(high insulin): 1661.1(672.3) vs 2055.6(907.0) μmol/m2/min (p = 0.042), ISI(high insulin): 14.2(7.3) vs 20.7(17.2) μmol/m2/min (p = 0.014). Pakistani patients had lower percentage NEFA suppression 30 minutes into clamp hyperinsulinemia than Norwegians: 41.9(90.6)% vs 71.2(42.1)%, (p = 0.042). The relationship of ISI to BMI, leptin and interleukin-1 receptor antagonist also differed between Norwegians and Pakistanis.
Conclusions: Compared with Norwegian patients, Pakistani patients with T2DM had lower insulin sensitivity, affecting both glucose and lipid metabolism. The relation of insulin sensitivity to BMI and some adipokines also differed between the groups.