No abstract

Replacing habitual consumption of SSBs with milk may have beneficial effects on lean body mass and growth in children, despite no changes in percentage body fat. This trial was registered at clinicaltrials.gov as NCT00149695.

Overweight postmenopausal women may be more susceptible to bone loss with weight reduction than previously studied obese women. The influence of energy restriction and Ca intake on BMD was assessed in 66 individuals. Weight reduction resulted in bone loss at several sites in women consuming 1 g Ca/day and was mitigated with higher calcium intake at 1.7 g/day.Introduction: Bone loss is associated with weight loss in obese postmenopausal women and can be prevented with calcium (Ca) supplementation. However, because bone loss caused by weight loss may be greater in overweight than obese women, it is not clear whether Ca supplementation is also beneficial in overweight women. Materials and Methods:We assessed the influence of caloric restriction at two levels of Ca intake on BMD and BMC in 66 overweight postmenopausal women (age, 61 ± 6 years; body mass index, 27.0 ± 1.8 kg/m

Bone mineral density (BMD) is highly correlated with body weight, and weight loss is associated with reduced BMD. Whether such losses of BMD increase skeletal fragility is unclear. We examined the effect of 9 wk of energy restriction (ER) on bone density, mineral and matrix protein composition and biomechanical properties in mature (20 wk old, n = 12) and aged (48 wk old, n = 16) female rats. Energy-restricted rats were fed 40% less energy than controls that consumed food ad libitum. Bone content of mineral (ash and calcium content) and matrix proteins (hydroxyproline, pyridinium crosslinks and proteoglycans), serum hormones, site-specific bone density and biomechanical properties (peak load, peak torque, shear stiffness and bending stiffness) were measured at the conclusion of the study. In both age groups, ER reduced body weight by 15 +/- 10% (P < 0.001) and dramatically decreased femoral bone density by 32-35% (P < 0.01) compared with controls. Energy restriction resulted in a small reduction in tibia and humerus density, as well as biomechanical properties in the aged but not mature rats (P < 0.05). Reduced serum levels of insulin and estradiol due to ER in aged rats (P < 0.05) may play a role in altering bone quality. These data show that although weight loss due to ER is detrimental to some bone parameters in mature rats, only aged rats show consistent reductions in bone density and biomechanical properties.

We suggest that WL is associated with elevated calcium requirements that, if not met, could activate the calcium-parathyroid hormone axis to absorb more calcium. Normal intakes of calcium during energy restriction result in inadequate total calcium absorption and could ultimately compromise calcium balance and bone mass.

Eukaryotic cells contain a variety of subcellular organelles, each of which performs unique tasks. Thus follows that in order to coordinate these different intracellular functions, a highly dynamic system of communication must exist between the various compartments. Direct endoplasmic reticulum (ER)-mitochondria communication is facilitated by the physical interaction of their membranes in dedicated structural domains known as mitochondria-associated membranes (MAMs), which facilitate calcium (Ca(2+)) and lipid transfer between organelles and also act as platforms for signaling. Numerous studies have demonstrated the importance of MAM in ensuring correct function of both organelles, and recently MAMs have been implicated in the genesis of various human diseases. Here, we review the salient structural features of interorganellar communication via MAM and discuss the most common experimental techniques employed to assess functionality of these domains. Finally, we will highlight the contribution of MAM to a variety of cellular functions and consider the potential role of MAM in the genesis of metabolic diseases. In doing so, the importance for cell functions of maintaining appropriate communication between ER and mitochondria will be emphasized.

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Osteopontin null-mice were previously shown to have bones containing more mineral and larger mineral crystals. These bones were independently seen to be resistant to ovariectomy-induced remodeling. To separate the physicochemical effects of osteopontin, which is an in vitro inhibitor of mineral crystal formation and growth, from effects of osteopontin on in vivo bone remodeling, this study examined mature (5-month-old) osteopontin-null (Opn-/-) and wildtype (WT) mice given a calcium-deficient diet. Biochemical parameters were measured during 4 weeks of Ca deficiency, followed by 1 week of refeeding adequate Ca. Ca deficiency caused a transiently greater rise in bone resorption in WT than Opn-/- mice (P = 0.01), whereas only the Opn-/- mice tended to increase Ca absorption (P = 0.08), yet both groups showed elevated levels of parathyroid hormone (PTH) (P < 0.001). The rise in markers of bone formation due to Ca deficiency was similar in both groups during Ca deficiency. Fourier transform infrared microspectroscopy assessed mineral properties at 20 microm spatial resolution in different anatomic regions of the bone. The Ca-deficient Opn-/- animals had slightly increased mineral content as compared to the WT, and there was a significant increase in the mineral content of older (endosteal) bone, implying that osteoclast recruitment was impaired. Crystallinity in the Ca-deficient Opn-/- bones was increased relative to the Ca-deficient WT at all sites except adjacent to the periosteum (younger mineral). These data suggest that osteopontin has both a physicochemical effect (inhibiting crystal growth and crystal proliferation) and a role in osteoclast recruitment, and in its absence, extraskeletal organs maintain calcium homeostasis.