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BioMed Research International
Volume 2013 (2013), Article ID 921348, 6 pages
http://dx.doi.org/10.1155/2013/921348
Research Article

Possible Role of Hyperinsulinemia and Insulin Resistance in Lower Vitamin D Levels in Overweight and Obese Patients

1Clinical Nutrition Unit, Department of Biomedical Sciences and Human Oncology, Section of Clinical Oncology, School of Medicine, University of Bari, Policlinico, Piazza Giulio Cesare 11, 70124 Bari, Italy
2Department of Biomedical Sciences and Human Oncology, School of Medicine, University of Bari, Policlinico, Piazza Giulio Cesare, 70124 Bari, Italy
3Outpatient Clinic for Metabolic Diseases and Endocrinology, Conversano Hospital, ASL Bari, 70014 Conversano, Italy
4Section of Endocrinology and Metabolic Diseases, Department of Emergency and Organ Transplantation, School of Medicine, University of Bari, Policlinico, Piazza Giulio Cesare, 70124 Bari, Italy

Received 5 August 2012; Revised 6 December 2012; Accepted 8 December 2012

Academic Editor: Joseph Fomusi Ndisang

Copyright © 2013 Giovanni De Pergola et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

A cohort of 66 healthy overweight and obese patients, 53 women and 13 men were examined. Waist circumference and fasting 25(OH)D, insulin, glucose, lipid (cholesterol, HDL cholesterol, and triglyceride), C-reactive protein (CRP), and complement 3 (C3), and 4 (C4) serum concentrations were measured. Insulin resistance was assessed by the homeostasis model assessment (HOMAIR). Results. 25(OH)D levels showed a significant negative correlation with BMI ( ), waist circumference ( ), fasting insulin ( ), HOMAIR ( ), triglycerides ( ), CRP ( ), C3 ( ), and C4 ( ). Multiple regression analyses were performed with 25(OH)D as the dependent variable and BMI (or waist circumferences), fasting insulin (or HOMAIR), triglycerides, and CRP (or C3 or C4) as independent variables. Only insulin or HOMAIR maintained a significant independent association with 25(OH)D levels, whereas vitamin D did not maintain a significant independent association with CRP or C3 or C4 concentrations. Conclusions. The present study, performed in overweight and obese subjects, shows that 25(OH)D levels are negatively associated with inflammatory parameters such as CRP and C3 and C4 levels, but not independently of BMI, body fat distribution, insulin levels, or insulin resistance. Our results suggest that hyperinsulinemia and/or insulin resistance are directly responsible for decrease of 25(OH)D levels in obesity.