Beta Cell Function, Hepatic Insulin Clearance, and Insulin Sensitivity in South Asian and Nordic Women after Gestational Diabetes Mellitus
South Asians have higher risk of type 2 diabetes after gestational diabetes mellitus (GDM) than Nordic women; however the mechanisms behind this difference remain unclear. We investigated insulin sensitivity, beta cell function, and hepatic insulin clearance, in 179 South Asian and 108 Nordic women ~17 months after GDM (mean age 35.3 years and BMI 29.1 kg/m2), via an oral glucose tolerance test using deconvolution of C-peptide kinetics. 31% of South Asian and 53% of Nordic participants were normoglycemic at the time of measurement. South Asian women had higher area under the curve (AUC) for glucose, pre-hepatic insulin, peripheral insulin, and lower levels of insulin sensitivity, disposition index, and fasting hepatic insulin clearance compared with Nordic women. In the group with prediabetes or diabetes, South Asian women displayed similar AUC for glucose and pre-hepatic insulin, but higher AUC for peripheral insulin, and lower levels of disposition index, and fasting hepatic insulin clearance compared with Nordic women. The waist-to-height ratio mediated ~25-40% of the ethnic differences in insulin sensitivity in normoglycemic women. Overall, our novel data showed that normoglycemic South Asian women after GDM displayed lower insulin secretion for a given insulin resistance, and lower hepatic insulin clearance compared with Nordic women. South Asian women are at high risk of developing type 2 diabetes after GDM, and preventive efforts should be prioritized.