Weight reduction induces bone loss by several factors, and the effect of higher protein (HP) intake during caloric restriction on bone mineral density (BMD) is not known. Previous study designs examining the longer-term effects of HP diets have not controlled for total calcium intake between groups and have not examined the relationship between bone and endocrine changes. In this randomized, controlled study, we examined how BMD (areal and volumetric), turnover markers, and hormones [insulin-like growth factor 1 (IGF-1), IGF-binding protein 3 (IGFBP-3), 25-hydroxyvitamin D, parathyroid hormone (PTH), and estradiol] respond to caloric restriction during a 1-year trial using two levels of protein intake. Forty-seven postmenopausal women (58.0 AE 4.4 years; body mass index of 32.1 AE 4.6 kg/ m 2 ) completed the 1-year weight-loss trial and were on a higher (HP, 24%, n ¼ 26) or normal protein (NP, 18%, n ¼ 21) and fat intake (28%) with controlled calcium intake of 1.2 g/d. After 1 year, subjects lost 7.0% AE 4.5% of body weight, and protein intake was 86 and 60 g/d in the HP and NP groups, respectively. HP compared with NP diet attenuated loss of BMD at the ultradistal radius, lumbar spine, and total hip and trabecular volumetric BMD and bone mineral content of the tibia. This is consistent with the higher final values of IGF-1 and IGFBP-3 and lower bone-resorption marker (deoxypyridinoline) in the HP group than in the NP group ( p < .05). These data show that a higher dietary protein during weight reduction increases serum IGF-1 and attenuates total and trabecular bone loss at certain sites in postmenopausal women. ß

Endogenous collagen cross-links influence cartilage biomechanical properties and resistance to degradation. Formalin fixation modifies collagen residues and forms new cross-links in a dose-dependent manner. We tested the hypothesis that magnetization transfer (MT) effects and T 2 depend on collagen cross-linking in cartilage. These parameters were measured in bovine nasal cartilage (BNC) prior to fixation, after 9 weeks of immersion in formalin solutions ranging in concentration from 0% to 10%, and after NaBH 3 CN reduction and washing. T 2 decreased by 59.4% ؎ 1.1% upon fixation in 10% formalin, and was 32.2% ؎ 5.2% shorter than initial values after washing. The apparent MT rate increased 25.9% ؎ 3.7% and 52.8% ؎ 7.1% over baseline under these conditions. Biochemical assays showed no significant differences in water, proteoglycan, natural cross-link, or collagen content between the 0% and 10% formalin-treated samples, while amino acid analysis demonstrated losses in (

Background: Weight loss is associated with bone loss, but this has not been examined in overweight premenopausal women. Objective: The aim of this study was to assess whether overweight premenopausal women lose bone with moderate weight loss at recommended or higher than recommended calcium intakes. Design: Overweight premenopausal women [n ҃ 44; x (ȀSD) age: 38 Ȁ 6.4 y; body mass index (BMI): 27.7 Ȁ 2.1 kg/m 2 ] were randomly assigned to either a normal (1 g/d) or high (1.8 g/d) calcium intake during 6 mo of energy restriction [weight loss (WL) groups] or were recruited for weight maintenance at 1 g Ca/d intake. Regional bone mineral density and content were measured by dual-energy X-ray absorptiometry, and markers of bone turnover were measured before and after weight loss. True fractional calcium absorption (TFCA) was measured at baseline and during caloric restriction by using a dual-stable calcium isotope method. Results: The WL groups lost 7.2 Ȁ 3.3% of initial body weight. No significant decrease in BMD or rise in bone turnover was observed with weight loss at normal or high calcium intake. The group that consumed high calcium showed a strong relation (r ҃ 0.71) between increased femoral neck bone mineral density and increased serum 25-hydroxyvitamin D. No significant effect of weight loss on TFCA was observed, and the total calcium absorbed was adequate at 238 Ȁ 81 and 310 Ȁ 91 mg/d for the normal-and high-calcium WL groups, respectively. Conclusion: Overweight premenopausal women do not lose bone during weight loss at the recommended calcium intake, which may be explained by sufficient amounts of absorbed calcium. Clin Nutr 2007;85:972-80. Am J

These data show that vitamin D supplementation increases TFCA and that WL decreases TFCA and suggest that, when calcium intake is 1.2 g/d, either 10 or 63 μg vitamin D/d is sufficient to maintain the calcium balance. This trial was registered at clinicaltrials.gov as NCT00473031.