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Suboptimal vitamin D status among the South Asian UK population is widely reported; however, its impact on bone health is unclear. The aim of the present study was to conduct a comparative investigation of vitamin D status in postmenopausal South Asian (SA) and Caucasian (C) women and its relationship to parathyroid hormone (PTH) concentration, biochemical markers of bone turnover and bone quality. A cross-sectional study of community-dwelling women aged 50-66 years was carried out. A total of sixty-six SA women of Pakistani origin and forty-two C women living in the same community were recruited. Fasting blood was taken for the measurement of vitamin D, PTH and biochemical markers of bone turnover, including type-1 collagen beta C-telopeptide (betaCTX), procollagen type-1 amino-terminal propeptide (P1NP), and bone-specific alkaline phosphatase (BAP) activity. Bone quality was assessed using broadband ultrasound attenuation (BUA). Total serum 25-hydroxyvitamin D (25(OH)D) was significantly lower in the SA women than the C women (medians: SA 10.5 v. C 47.1 nmol/l; P < 0.001) This was associated with a significantly elevated serum PTH concentration in the SA group (medians: SA 7.3 v. C 4.5 pmol/l; P < 0.01). BAP activity was also significantly higher in the SA group, indicating elevated osteoblast activity and bone turnover (medians: SA 23.0 v. C 20.0 U/l; P < 0.05). No significant differences were observed between the two groups for P1NP, betaCTX or BUA. Although the SA women had significantly higher serum PTH and lower 25(OH)D concentrations than C women, this was not associated with significantly higher markers of bone resorption, or reduced bone quality in the SA women.

The concurrent presence of low bone density (osteopenia/osteoporosis) and low muscle mass (sarcopenia) in older adults has led to the recognition of “osteosarcopenia” (OS) as a singular entity. Vitamin D may play important role in the manifestation of OS, in terms of intake, absorption, and bioavailability. Evidence suggests that bioavailable 25(OH)D may be a better indicator of Vitamin D compared to total 25(OH)D due to its weak bind to albumin, increasing its ‘availability’. The aim of this study was to assess total and bioavailable 25(OH)D levels in postmenopausal women and to determine their associations to bone density and muscle mass. We assessed body composition, bone density, and 25(OH)D indices of multiethnic, postmenopausal Malaysian women. A significant and negative correlation was found between body fat % and each index of 25(OH)D. Both bioavailable and total 25(OH)D were positively correlated with serum calcium and negatively correlated with iPTH(intact parathyroid hormone). VDBP(Vitamin D binding protein) level was significantly correlated with bioavailable 25(OH)D level, but not with the total 25(OH)D level. Stepwise regression analysis revealed that bioavailable, but not total, 25(OH)D was significantly correlated to bone density and muscle mass, (where stronger correlation was found with bone density), suggesting its superiority. Nevertheless, the low effect size warrants further studies.

Introduction: The optimal level of total 25(OH)D in Malaysian postmenopausal women that is necessary to ameliorate the combined effects of decreased bone mineral and muscle mass, and increase in adiposity, as seen in osteosarcopenic obesity, is unknown. Given that these are common pathologies existing in bone, muscle and excess fat-related disorders, this study investigated the association between body composition, functional capacity and total 25(OH)D levels. Methods: This was a cross-sectional study involving 117 postmenopausal Malaysian women aged 50-88 years. Total 25(OH)D was analysed by chemiluminescent microparticle immunoassay CMIA on Siemens® platforms. Bone mineral was measured by broadband ultrasound attenuation. Functional performance was assessed using modified components of short physical performance battery test. Statistical analysis was performed using the Statistical Package for Social Sciences (SPSS Version 25.0). Results: Overall, 47% women were vitamin D deficient; 3% had none, 22% had one, 65% had two, and 10% had all three adverse body composition indicators (osteosarcopenic obesity). Individuals without any adverse body composition indicator had higher total 25(OH) D (74.7±7.0nmol/L, p=0.004) compared to all the other groups [1 (53.0±3.8nmol/L); 2 (48.7±1.9nmol/L) and 3 (58.3±5.4nmol/L)]. The single inflection point (ROC curve) for total 25(OH)D in predicting osteosarcopenic obesity was 58.9nmol/L. Conclusion: Higher vitamin D levels were associated with lower body fat, enhanced bone quality, and improved functional capacity. Maintaining vitamin D levels above >58.9nmol/L may protect Malaysian postmenopausal women against the combined pathologies of bone, muscle and excess fat. [ABSTRACT FROM AUTHOR]

The concurrent presence of low bone density (osteopenia/osteoporosis) and low muscle mass (sarcopenia) in older adults has led to the recognition of "osteosarcopenia" (OS) as a singular entity. Vitamin D may play important role in the manifestation of OS, in terms of intake, absorption, and bioavailability. Evidence suggests that bioavailable 25(OH)D may be a better indicator of Vitamin D compared to total 25(OH)D due to its weak bind to albumin, increasing its 'availability'. The aim of this study was to assess total and bioavailable 25(OH)D levels in postmenopausal women and to determine their associations to bone density and muscle mass. We assessed body composition, bone density, and 25(OH)D indices of multiethnic, postmenopausal Malaysian women. A significant and negative correlation was found between body fat % and each index of 25(OH)D. Both bioavailable and total 25(OH)D were positively correlated with serum calcium and negatively correlated with iPTH(intact parathyroid hormone). VDBP(Vitamin D binding protein) level was significantly correlated with bioavailable 25(OH)D level, but not with the total 25(OH)D level. Stepwise regression analysis revealed that bioavailable, but not total, 25(OH)D was significantly correlated to bone density and muscle mass, (where stronger correlation was found with bone density), suggesting its superiority. Nevertheless, the low effect size warrants further studies. [ABSTRACT FROM AUTHOR]