Comparison of two phantoms for body composition with dual-energy X-ray absorptiometry

Vitamin D receptorFokIgenotype influences bone mineral density response to strength training, but not aerobic training

To determine the influence of the vitamin D receptor (VDR) gene FokI and BsmI genotype on bone mineral density response to two exercise training modalities, 206 healthy men and women (50-81 years old) were studied before and after approximately 5-6 months of either aerobic exercise training (AT) or strength training (ST). A totla of 123 subjects completed AT (51 men, 72 women) and 83 subjects completed ST (40 men, 43 women). DNA was extracted from blood samples of all subjects and genotyping was performed at the VDR FokI and BsmI locus to determine its association to training response. Total body, greater trochanter and femoral neck bone mineral density (BMD) were measured before and after both training programmes using dual-energy X-ray absorptiometry. VDR BsmI genotype was not significantly related to BMD at baseline or after ST or AT. However, VDR FokI genotype was significantly related to ST- but not AT-induced changes in femoral neck BMD (P < 0.05). The heterozygotes (Ff) in the ST group approached a significantly greater increase in femoral neck BMD (P = 0.058) compared to f homozygotes. There were no significant genotype relationships in the AT group. These data indicate that VDR FokI genotype may influence femoral neck BMD response to ST, but not AT.

Endocrine control of body composition in infancy, childhood, and puberty

Body composition exhibits marked variations across the early human lifetime. The precise physiological mechanisms that drive such developmental adaptations are difficult to establish. This clinical challenge reflects an array of potentially confounding factors, such as marked intersubject differences in tissue compartments; the incremental nature of longitudinal intrasubject variations in body composition; technical limitations in quantitating the unobserved mass of mineral, fat, water, and muscle ad seriatim; and the multifold contributions of genetic, dietary, environmental, hormonal, nutritional, and behavioral signals to physical and sexual maturation. From an endocrine perspective (reviewed here), gonadal sex steroids and GH/IGF-I constitute prime determinants of evolving body composition. The present critical review examines hormonal regulation of body composition in infancy, childhood, and puberty.