Calcium homeostasis may influence resting energy expenditure with effects most apparent in early pubertal girls.

AIM: Perturbations in dietary and hormonal components of the calciotropic network may be mediated through the influence of calcium homoeostasis on resting energy expenditure (REE). We investigated the association of dietary and hormonal factors involved in the regulation of calcium homoeostasis with REE in girls. METHODS: Thirty-six girls aged 7-11 years participated. REE was assessed by indirect calorimetry, and body composition, dietary intake (calcium, vitamins D and K, phosphorus) and serum hormones (PTH, osteocalcin, 25OHD) were evaluated by DXA, 24 h recall and serum assay, respectively. RESULTS: A positive association between vitamin K and REE and an inverse association of parathyroid hormone (PTH) with REE (p = 0.05) were observed. PTH and REE were positively related in those having normal adiposity (p = 0.03) and inversely related in those with excess adiposity (p = 0.01). The association of REE with vitamin K intake was evident in lean individuals (p = 0.001), but was null in those with excess adiposity. CONCLUSION: Decreased calciotropic hormone levels along with increased related nutrient intakes were associated with greater REE, although these relationships differed according to adiposity. The physiologic response to the diet and subsequent energy partitioning needs to be considered in the context of puberty. In particular, regulation and signalling of the calciotropic network during pubertal maturation warrant investigation.

Short-term physical activity intervention decreases femoral bone marrow adipose tissue in young children: a pilot study.

Mechanical stimulation is necessary for maximization of geometrical properties of bone mineralization contributing to long-term strength. The amount of mineralization in bones has been reciprocally related to volume of bone marrow adipose tissue and this relationship is suggested to be an independent predictor of fracture. Physical activity represents an extrinsic factor that impacts both mineralization and marrow volume exerting permissive capacity of the growing skeleton to achieve its full genetic potential. Because geometry- and shape-determining processes primarily manifest during the linear growth period, the accelerated structural changes accompanying early childhood (ages 3 to 6 y) may have profound impact on lifelong bone health. The objective of this pilot study was to determine if a short-term physical activity intervention in young children would result in augmentation of geometric properties of bone. Three days per week the intervention group (n=10) participated in 30 min of moderate intensity physical activity, such as jumping, hopping and running, and stretching activities, whereas controls (n=10) underwent usual activities during the 10-week intervention period. Femoral bone marrow adipose tissue volume and total body composition were assessed by magnetic resonance imaging and dual-energy X-ray absorptiometry, respectively, at baseline and after 10 weeks. Although after 10-weeks, intergroup differences were not observed, a significant decrease in femoral marrow adipose tissue volume was observed in those participating in physical activity intervention. Our findings suggest that physical activity may improve bone quality via antagonistic effects on femoral bone marrow adipose tissue and possibly long-term agonistic effects on bone mineralization.