Barbara Garanty-Bogacka

Association between serum osteocalcin, adiposity and metabolic risk in obese children and adolescents

INTRODUCTION Childhood obesity has been associated with the development of insulin resistance, potentially leading to several metabolic disorders. Osteocalcin has been reported to contribute to the regulation of glucose tolerance and insulin sensitivity. The purpose of this study was to examine the relationship between serum osteocalcin and metabolic risk factors in obese children and adolescents. MATERIAL AND METHODS Age, gender, pubertal stage, adiposity markers (standard deviation score of body mass index: BMI-SDS, percentage of body fat, waist circumference), blood pressure, serum osteocalcin (OC), fasting plasma glucose and insulin, glycated haemoglobin level (HbA1c), insulin resistance estimated by homeostasis model assessment (HOMA-IR), lipid profile, C-reactive protein (CRP), fibrinogen (FB), white blood cell count (WBC) and 25-hydroxyvitamin D (25-OH-D) were evaluated in 142 obese children and adolescents. Stepwise multiple regression analysis was used to determine the relationship between serum osteocalcin and metabolic risk parameters. RESULTS Mean serum osteocalcin level was 72.0 ± 20.5 μg/L (range: 16.8-181.5 µg/L). After adjustment for multiple potential confounders, serum osteocalcin concentration was inversely associated with adiposity markers as well as HOMA-IR, HbA1c, triglycerides, CRP, FB and positively with 25-OH-D and HDL-cholesterol. In stepwise multiple linear regression analysis adjusted for age, gender and pubertal stage, osteocalcin was significantly negatively related to HOMA-IR, triglycerides and waist circumference. CONCLUSIONS Serum osteocalcin concentration is associated with blood markers of dysmetabolic phenotype and measures of adiposity, suggesting that osteocalcin is important not only for bones but also for glucose and fat metabolism as early as during childhood.

Polymorphism of CD36 gene, carbohydrate metabolism and plasma CD36 concentration in obese children. A preliminary study.

INTRODUCTION CD36 may play an important role in removal of oxidized LDLs from plasma, protein glycation, the pathogenesis of insulin resistance, type 2 diabetes, and diabetic micro- and macroangiopathy. Some reports have pointed to decreased expression of macrophages in association with mutations of the CD36 gene in hyperglycemic and obese subjects. The aim of the study was to search for an association between CD36 gene polymorphism and carbohydrate metabolism disturbances or variability of plasma soluble CD36 concentrations in obese children. MATERIAL/METHODS The study included 60 children aged 10 to 15 years: 30 with (study group) and 30 without (control group) obesity. Each patients glycated hemoglobin, weight, height, waist and hip circumference, and systolic and diastolic blood pressure were measured, BMI, WHR and MAP were calculated, and oral glucose tolerance test was performed with glucose and insulin concentration measurements. Amplicons of exons 4-6 of CD36 were studied using DHPLC technique. The PCR products with alterations were bidirectionally sequenced. Plasma concentrations of human antigen CD36 was measured using a commercially available enzyme-linked immunosorbent assay (ELISA). RESULTS We found two intronic alterations: IVS3-6 T/C (rs3173798) and IVS4-10 G/A (rs3211892), one nonsynonymous substitution: G367A (Glu123Lys, rs183461468) in exon 5 and two synonymous transitions in exon 6: G573A (Pro191Pro, rs5956) and A591T (Thr197Thr, rs141680676). There were no significant differences in any biochemical or morphometric parameters between genotype groups. DISCUSSION The polymorphisms of the studied fragment of CD36 are not associated with carbohydrate metabolism disturbances or the variability of plasma soluble CD36 concentrations in obese children, but further research is necessary to assess their functional implications.