N-terminal pro-B-type natriuretic peptide levels vary by ethnicity and are associated with insulin sensitivity after gestational diabetes mellitus

Background Individuals of South Asian origin have a greater risk of cardiovascular disease after gestational diabetes mellitus (GDM) than European individuals. B-type natriuretic peptide (BNP) and the amino-terminal fragment of its prohormone (NT-proBNP) are commonly used for heart failure screening and diagnosis, but biologically BNP exerts several beneficial cardiovascular effects primarily by counteracting the renin-angiotensin-aldosterone-system. We asked whether ethnic differences in circulating NT-proBNP levels could be explained by the differences in cardiometabolic and inflammatory risk markers? Methods We examined 162 South Asian and 107 Nordic women in Norway 1-3 years after GDM with a clinical examination, fasting blood samples and an oral glucose tolerance test. We measured the levels of NT-proBNP, high-sensitivity cardiac troponin T, high-sensitivity C-reactive protein (hsCRP), interleukin-6 (IL-6), leptin, adiponectin and markers of insulin sensitivity, such as the Matsuda insulin sensitivity index (ISI). Finally, we tried to identify which independent covariate best mediated the ethnic differences in NT-proBNP. Results The mean (SD) age was 35.3 (4.5) years, BMI 29.1 (6.0) kg/m(2), waist-height ratio 0.60 (0.08) and 164 women (61%) had prediabetes/diabetes. Notably, South Asian women had lower levels of NT-proBNP than Nordic women in both the normoglycemic and prediabetes/diabetes groups (median (IQR) 26 (15-38) vs. 42 (22-66) ng/L, p < 0.001). Higher NT-proBNP levels were associated with greater insulin sensitivity in both South Asian and Nordic women (p = 0.005 and p < 0.001). South Asian women had higher levels of hsCRP (median (IQR) 2.2 (1.1-4.4) vs. 1.2 (0.3-4.2) mg/L), IL-6 (2.3 (1.5-3.2) vs. 1.5 (1.5-2.5) pg/mL), leptin (1647 (1176-2480) vs. 1223 (876-2313) pmol/L), and lower adiponectin levels (7.2 (5.3-9.3) vs. 10.0 (7.2-13.5) mg/L) and Matsuda ISI (2.4 (1.7-3.7) vs. 4.2 (2.9-6.1), p(all)<0.01) than Nordic women. Even after adjusting for these differences, higher NT-proBNP levels remained associated with insulin sensitivity (22% higher NT-proBNP per SD Matsuda ISI, p = 0.015). Insulin sensitivity and adiponectin mediated 53% and 41% of the ethnic difference in NT-proBNP. Conclusions NT-proBNP levels are lower in South Asian than in Nordic women after GDM. Lower NT-proBNP levels correlate with impaired insulin sensitivity. Lower NT-proBNP levels in South Asian women could, therefore, be attributed to impaired insulin sensitivity rather than total body fat.