Low levels of 25-OH-vitamin D are related to markers of systemic inflammation in obese non diabetic patients

Hypovitaminosis D has been associated with insulin-resistance and diabetes. A low-grade systemic inflammation is largely reported in obese patients. However, the relationships between vitamin D status and inflammation in obese subjects have not been investigated yet. In 86 morbidly obese, non diabetic patients (47 females, 43 ± 12 years, BMI 44.1 ± 6.7 kg/m2 ) we collected: percent (FAT- %) and absolute (FAT-kg) fat mass (by DEXA), glucose and insulin concentrations (fasting and during OGTT), plasma and serum levels of 25(OH)D, HS CRP, IL-6, TNF-alfa, leptin and adiponectin. To assess vitamin D status, subjects were divided in two groups based on the cut-off value of 50 nmol/l of 25(OH)D. Patients with low 25(OH)D accounted for the 32% of the whole sample and appeared more insulin-resistant, according to HOMA-IR (7.3 ± 2.8 versus 5.7 ± 3.9, P = 0.01) and AUCinsulin (213.6 ± 83 versus 141.1 ± 70.1, P = 0.005), after adjustment for age, sex and FAT-Kg). No differences in glucose tolerance were observed. Noteworthy, subjects with low 25(OH)D had the highest levels of HS CRP (12.2 ± 5.8 versus 3.4 ± 1.3 mg/l, P = 0.02), TNF-alfa (12.7 ± 5.9 versus 6.4 ± 5.6 pg/ ml, P = 0.003) and IL-6 (20.5 ± 14.2 versus 9.2 ± 4.7 pg/ml, P = 0.03), while no significant differences were detected in adiponectin and leptin concentrations. Accordingly, controlling for age, sex and FAT-Kg, 25(OH)D concentrations were negatively related with HS CRP (b = –0.24, P = 0.056), TNF-alfa (b = –0.38, P = 0.02) and IL-6 (b = –0.61, P = 0.008). In conclusion, these preliminary data suggest a potential relationship between vitamin D status and systemic inflammation in obese non diabetic subjects. Further analysis in a more powerful study group is required.