Racial differences in cortical bone and their relationship to biochemical variables in Black and White children in the early stages of puberty

Osteoporotic fracture rates differ according to race with Blacks having up to half the rate of Whites. The current study demonstrates that racial divergence in cortical bone properties develops in early childhood despite lower serum 25-hydroxyvitamin D in Blacks.

INTRODUCTION

Racial differences in bone structure likely have roots in childhood as bone size develops predominantly during growth. This study aimed to compare cortical bone health within the tibial diaphysis of Black and White children in the early stages of puberty and explore the contributions of biochemical variables in explaining racial variation in cortical bone properties.

METHODS

A cross-sectional study was performed comparing peripheral quantitative computed tomography-derived cortical bone measures of the tibial diaphysis and biochemical variables in 314 participants (n = 155 males; n = 164 Blacks) in the early stages of puberty.

RESULTS

Blacks had greater cortical volumetric bone mineral density, mass, and size compared to Whites (all p < 0.01), contributing to Blacks having 17.0 % greater tibial strength (polar strength-strain index (SSIP)) (p < 0.001). Turnover markers indicated that Blacks had higher bone formation (osteocalcin (OC) and bone-specific alkaline phosphatase) and lower bone resorption (N-terminal telopeptide) than Whites (all p < 0.01). Blacks also had lower 25-hydroxyvitamin D (25(OH)D) and higher 1,25-dihydroxyvitamin D (1,25(OH)2D) and parathyroid hormone (PTH) (all p < 0.05). There were no correlations between tibial bone properties and 25(OH)D and PTH in Whites (all p ≥ 0.10); however, SSIP was negatively and positively correlated with 25(OH)D and PTH in Blacks, respectively (all p ≤ 0.02). Variation in bone cross-sectional area and SSIP attributable to race was partially explained by tibial length, 25(OH)D/PTH, and OC.

CONCLUSIONS

Divergence in tibial cortical bone properties between Blacks and Whites is established by the early stages of puberty with the enhanced cortical bone properties in Black children possibly being explained by higher PTH and OC.

Reduced serum concentrations of 25-hydroxy vitamin D in Egyptian patients with systemic lupus erythematosus: relation to disease activity

BACKGROUND

Recently, vitamin D deficiency has been implicated as a potential environmental factor triggering some autoimmune disorders, including systemic lupus erythematosus (SLE)). In addition, patients with SLE, especially those with increased disease activity, were suggested to have decreased vitamin D level, suggesting that vitamin D might play a role in regulating autoantibody production.

MATERIAL/METHODS

To assess 25 hydroxy vitamin D [25(OH)D] status in Egyptian patients with SLE and its relation to disease activity. Clinical evaluation and assay of serum 25(OH)D, total calcium, phosphorous, alkaline phosphatase (ALP) and parathyroid hormone (PTH) were done on 60 SLE patients in comparison to 60 matched-healthy subjects. Serum 25(OH)D levels <30 and 10 ng/ml were defined as vitamin D insufficiency and deficiency, respectively.

RESULTS

Serum 25(OH)D was significantly lower in patients than in controls (26.33 ± 12.05 vs. 42.66 ± 9.20 respectively, p < 0.0001), with 13.30% and 60% being deficient and insufficient, respectively. Serum 25(OH)D levels were lower with increased disease activity (p = 0.03) and frequency of photosensitivity(p = 0.02) and photoprotection (p = 0.002). Systemic lupus erythematosus disease activity index (SLEDAI) score (OR: 2.72, 95% CI: 1.42-5.18, P = 0.002), photosensitivity (OR: 3.6, 95% CI: 1.9-6.8, P < 0.01) and photoprotection (OR: 6.7, 95% CI: 2.9-8.8, P < 0.001) were significant predictors of 25(OH)D level among SLE cases.

CONCLUSIONS

Low vitamin D status is prevalent in Egyptian SLE patients despite plentiful exposure to sunlight throughout the year, and its level is negatively correlated to disease activity. Future studies looking at a potential role of vitamin D in the pathophysiology and treatment of SLE are warranted.

Body size and serum 25 hydroxy vitamin D response to oral supplements in healthy older adults

BACKGROUND

Vitamin D insufficiency is prevalent in the northeast United States. Since vitamin D insufficiency is readily amenable to supplementation, it is important to understand what factors are associated with serum 25 hydroxy vitamin D (25(OH)D) response to vitamin D supplementation.

OBJECTIVE

In this study we examined the association of serum 25(OH)D response to vitamin D supplementation with body size in a population of elderly subjects.

METHODS

257 healthy, ambulatory men and women 65 years of age or older were randomly assigned to treatment with either 700 IU/day (17.5 microg/d) of supplemental vitamin D(3) and 500 mg/day (12.5 mmol/d) of supplemental calcium, or to placebo.

RESULTS

In multivariate regression analyses, after adjusting for baseline 25(OH)D, season, and sex, we found change in 25(OH)D to be inversely associated with baseline BMI (p = 0.01) in subjects treated with supplements for one year. Change in 25(OH)D was also negatively associated with other baseline anthropometric measurements in these subjects.

CONCLUSION

Our study implies that body size should be taken into account when estimating the amount of vitamin D intake needed to raise 25(OH)D to the desired level.