Serum 25-hydroxyvitamin D concentrations in relation to cardiometabolic risk factors and metabolic syndrome in postmenopausal women

Abstract

Low concentrations of serum 25-hydroxyvitamin D [25(OH)D] may be associated with cardiometabolic disorders; however, little is known about their relation to intermediate metabolic and lipid markers. We investigated the relation of serum 25(OH)D concentrations to fasting insulin, glucose, dyslipidemia, adiposity, and prevalent metabolic syndrome. We conducted this cross-sectional analysis in 292 postmenopausal women aged 50-79 y in the Women's Health Initiative Calcium-Vitamin D (WHI-CaD) trial. Data were collected from 3 nested case-control studies that measured baseline serum 25(OH)D concentrations. Inverse probability weighting was used to approximate parameter estimates for the WHI-CaD population. In weighted linear regression models adjusted for age, race-ethnicity, month of blood draw, region, case-control status, smoking, alcohol, physical activity, and history of cardiometabolic risk factors, there was an inverse association of serum 25(OH)D with adiposity [body mass index (BMI): β = -1.12 ± 0.30, P = 0.0002; waist circumference: β = -3.57 ± 0.49, P < 0.0001; waist-hip ratio: β = -0.01 ± 0.002, P < 0.0001], triglycerides (β = -0.10 ± 0.02, P < 0.0001), and triglyceride:HDL-cholesterol ratio (β = -0.11 ± 0.03, P = 0.0003). The multivariable-adjusted odds ratio for metabolic syndrome for the highest (≥52 nmol/L) compared with the lowest (<35 nmol/L) tertile of serum 25(OH)D concentrations was 0.28 (95% CI: 0.14, 0.56). Significant associations remained after adjustment for BMI. We observed no significant associations with LDL cholesterol, HDL cholesterol, insulin, glucose, homeostatic model assessment of insulin resistance (HOMA-IR), or homeostatic model assessment of β cell function (HOMA-β). Higher serum 25(OH)D concentrations may be inversely associated with adiposity, triglycerides, triglyceride:HDL-cholesterol ratio, and metabolic syndrome but are not associated with LDL and HDL cholesterol, insulin, glucose, HOMA-IR, or HOMA-β in postmenopausal women. This trial was registered at clinicaltrials.gov as NCT00000611.