Ethnicity modifies the effect of obesity on insulin resistance in pregnancy: a comparison of Asian, South Asian, and Caucasian women.
BACKGROUND
Women of Asian and South Asian descent are at increased risk of developing gestational diabetes mellitus compared with Caucasians, despite lower body mass index (BMI). Nevertheless, there has been limited study of insulin action during pregnancy in these ethnic groups.


OBJECTIVE
The objective of the study was to compare insulin sensitivity in pregnancy in Asian, South Asian, and Caucasian subjects and to determine whether the impact of obesity on insulin action is modified by ethnicity.


METHODS
A cross-sectional study was performed in outpatients undergoing oral glucose tolerance testing in late pregnancy. Participants were stratified into three groups: 1) Caucasian (n = 116); 2) South Asian (n = 31); and 3) Asian (n = 28).


METHODS
Insulin sensitivity was measured using the oral glucose tolerance test (IS(OGTT)) index of M. Matsuda and R. DeFronzo, previously validated in pregnancy.


RESULTS
There were no significant ethnic differences in insulin sensitivity despite variation in prepregnancy BMI (Caucasians, 25.2 kg/m(2); South Asians, 23.3 kg/m(2); Asians, 21.4 kg/m(2); overall P = 0.0001). On multiple linear regression analysis, the strongest independent determinants of IS(OGTT) were gestational diabetes mellitus (t = -5.71; P < 0.0001) and BMI (t = -5.43; P < 0.0001). Importantly, both Asian (t = -2.87; P = 0.0047) and South Asian (t = -2.46; P = 0.015) ethnicity also emerged as negative, independent determinants of IS(OGTT). Furthermore, Asian ethnicity significantly modified the association of prepregnancy BMI with IS(OGTT) (interaction term, t = -2.29; P = 0.0231).


CONCLUSIONS
Asian and South Asian ethnicity are both independently associated with increased insulin resistance in late pregnancy. Prepregnancy BMI has a much greater effect on insulin resistance in pregnancy in Asian women than in Caucasians. Ethnicity thus emerges as a factor that modulates the effect of obesity on insulin resistance in pregnancy.
Retnakaran
Ravi
R
Division of Endocrinology, University of Toronto, Toronto, Ontario, Canada M5G 1L5.
Hanley
Anthony J G
AJ
Connelly
Philip W
PW
Sermer
Mathew
M
Zinman
Bernard
B
D000328:Adult; D001210:Asia, Southeastern / Q000208:ethnology; D001213:Asian; D015415:Biomarkers; D015992:Body Mass Index; D002096:C-Peptide / Q000097:blood; D003430:Cross-Sectional Studies; D005260:Female; D005951:Glucose Tolerance Test; D006801:Humans; D007328:Insulin / Q000097:blood; D007333:Insulin Resistance / Q000502:physiology*; D008099:Liver / Q000378:metabolism; D009765:Obesity / Q000453:epidemiology* / Q000503:physiopathology*; D011247:Pregnancy; D011248:Pregnancy Complications / Q000453:epidemiology* / Q000503:physiopathology*; D011384:Proinsulin / Q000097:blood; D014481:United States; D044465:White People
D015415:Biomarkers; D002096:C-Peptide; D007328:Insulin; D011384:Proinsulin