Associations between vitamin D, osteocalcin, adipokines and markers of energy metabolism among Brazilian and American adolescents

Abstract

Adipokines such as adiponectin and leptin play, through hypothalamic modulation, an important role on bone formation, glucose homeostasis and satiety control. Leptin and osteocalcin genes are both controlled by vitamin D receptor. The effects of overweight and vitamin D deficiency at the bone mass of adolescents are not completely known, and substances such as leptin seem to have strong involvement in the regulation of their bone metabolism and glucose homeostasis. Objective: To investigate the relationship between serum vitamin D and osteocalcin with adipokines (leptin and adiponectin), biomarkers from energy metabolism (serum glucose, insulin, HOMA-IR) and nutritional status among Brazilian adolescents, and to integrate the results of the study conducted in Brazil with results obtained with an American population. Methods: This cross sectional study included 198 adolescents from 14 to 18 years old living in São Paulo, Brazil. Participants were interviewed by trained personnel and answered socioeconomic and demographic questionnaires, a 24-hour Food Recall, the International Physical Activity Questionnaire (IPAQ), and questions about sun exposure. Height and weight were measured in duplicate, as well as waist circumference. Blood collection after 12-hour fasting was done for biochemical analysis of: 25 hydroxyvitamin D, parathyroid hormone, glucose, insulin, carboxylated and non-carboxylated osteocalcin, leptin, adiponectin and lipid profile (total cholesterol, triglycerides, VLDL-c, LDL-c and HDL-c). Data from American adolescents come from the Camp Calcium, a summer camp from Purdue University designed to study calcium metabolism in adolescents, and from the GAPI (University of Georgia [UGA], Purdue University [PU] and Indiana University [IU]) trial. (AU)