Endocrine Abstracts

Background: While 25-hydroxy-vitamin D (25(OH)D) has been thoroughly investigated, the role of active vitamin D metabolite 1,25(OH)₂D in a metabolic syndrome still remains unclear. The aim of our study was to determine the association between 25(OH)D and 1,25(OH)₂D levels and several metabolic parameters and inflammatory markers in postmenopausal women with diabetes type 2 (T2DM).

Methods: Anthropometric variables, serum 25(OH)D, 1,25(OH)₂D, C-reactive protein (CRP), fibrinogen, PAI-1, fasting glucose, fasting insulin, and HbA1c were measured in 125 postmenopausal women with T2DM. Insulin resistance was estimated by homeostasis model assessment (HOMA-IR) and β-cell function by HOMA-B. A total of 125 diabetic patients were divided by BMI in normal weight group (n=22, BMI 22.7±1.5 kg/m²) and adipose group (n=93, BMI 32.2±5.8 kg/m²). Control group consisted of healthy obese postmenopausal women (n=46, BMI 34.9±6 kg/m²).

Results: Serum 25(OH)D concentrations were highest in the lean diabetics compared with obese diabetics and control subjects (P<0.0007) and were significantly associated with fasting glucose, insulin, HOMA-B, BMI, and PAI-1. In diabetic patients 25(OH)D levels were positively associated with HDLC (P<0.01) and negatively with triglycerides (P<0.04) and PAI-1 (P<0.001). Serum 1,25(OH)₂D concentrations were significantly higher in control obese subjects (77.4±17.0 nmol/l) compared with adipose diabetics (P<0.001), with no difference in relation to lean diabetics. Fasting glucose and HbA1c negatively correlated (P<0.01), whereas cholesterol and LDLC positively correlated (P<0.01) with 1,25(OH)₂D. Furthermore, 25(OH)D correlated with PAI-1 in all subjects while 1,25(OH)₂D correlated with fibrinogen but only in obese control subjects.

Conclusions: In T2DM women low serum 25(OH)D and 1,25(OH)₂D levels were associated with atherogenic dyslipidemia, glucose parameters, and low grade inflammation. The active hormonal form of vitamin D, 1,25(OH)₂D correlated with cholesterol, LDLC, and fibrinogen, while 25(OH)D correlated with triglycerides, HDLC, and PAI-1, suggesting that there may be an independent mechanism of action for 1,25(OH)₂D in relation to metabolic dysregulation.