The association between apolipoprotein M and insulin resistance varies with country of birth

Background and aims: Risk of type 2 diabetes mellitus (T2DM) differs according to ethnicity. Levels of apolipoprotein M (ApoM) have been shown to be decreased in T2DM. However, its role in different ethnicities is not known. We examined the differences in plasma ApoM levels in Swedish residents born in Iraq (Iraqis) and Sweden (Swedes) in relation to T2DM and insulin resistance (IR). Methods and results: Iraqis and Swedes, aged 45-65 years residing in Rosengård area of Malmö were randomly selected from census records and underwent an oral glucose tolerance test. Plasma levels of ApoM were quantified in 162 participants (Iraqis, n=91; Swedes, n=71) by a sandwich ELISA method. Age-, sex-, and body mass index (BMI) adjusted plasma ApoM levels differed by country of birth, with Swedes having 18% higher levels compared to Iraqis (p=0.001). ApoM levels (mean ± SD) were significantly decreased in Swedes with T2DM (0.73 ± 0.18) compared to those with normal glucose tolerance (NGT) (0.89 ± 0.24; p=0.03). By contrast, no significant difference in ApoM levels was found between Iraqis with T2DM (0.70 ± 0.17) and those with NGT (0.73 ± 0.13; p=0.41). In multivariate linear regression analysis with an interaction term between IR and country of birth, low ApoM levels remained significantly associated with IR in Swedes (p=0.008), independently of age, sex, BMI, family history of diabetes, HDL, LDL, and triglycerides, but not in Iraqis (p=0.35). Conclusion: Our results show that ApoM levels differ according to country of birth and are associated with IR and T2DM only in Swedes.