Black and white female adolescents lose vitamin D metabolites into urine

Racial Differences in Bone Microarchitecture and Estimated Strength at the Distal Radius and Distal Tibia in Older Adolescent Girls: a Cross-Sectional Study

BACKGROUND

Previous studies have demonstrated that an individual's race and ethnicity are important determinants of their areal bone mineral density (aBMD), assessed by dual-energy X-ray absorptiometry. However, there are few data assessing the impact of race on bone microarchitecture and strength estimates, particularly in older adolescent girls and young adults. We hypothesized that bone microarchitecture and strength estimates would be superior in Blacks compared to White and Asian American adolescent girls and young adults of similar age based on reports of higher aBMD in Blacks.

METHODS

We assessed BMD using dual-energy X-ray absoptiometry (DXA), bone microarchitecture at the distal radius and distal tibia using high-resolution peripheral quantitative computed tomography (HRpQCT) and estimated measures of bone strength using micro-finite element analysis (FEA) in 35 White, 15 Asian American, and 10 Black girls 14-21 years.

RESULTS

After controlling for height, most DXA measures of aBMD and aBMD Z scores were higher in Black girls compared with Whites and Asian Americans. HRpQCT and FEA showed that at the distal radius, Blacks had greater cortical perimeter, cortical area, trabecular thickness, trabecular BMD, estimated failure load, and stiffness than the other two groups. For the distal tibia, trabecular number and BMD were higher in Blacks than Asian Americans.

CONCLUSIONS

Particularly at the distal radius, adolescent and young adult White and Asian American girls have less favorable bone microarchitecture and lower bone strength than Blacks, possibly explaining the lower risk of fracture seen in Blacks.

LEVEL OF EVIDENCE

Level II.

Quantitation of 25-OH-Vitamin-D₂ and 25-OH-Vitamin-D₃ in Urine Using LC-MS/MS

Patients with significant proteinuria represent a unique population with respect to vitamin D status due to the urinary losses of vitamin D-binding protein (DBP) to which >99 % of circulating 25-hydroxy vitamin D (25(OH)D) is bound. Low serum concentrations of 25(OH)D have been found in children and adults with nephrotic syndrome (NS). However, previously described assays developed to quantify the magnitude of urinary loss are technically challenging. This chapter describes a simple and sensitive method to quantify 25(OH)D2 and 25(OH)D3 in urine specimens in a single analytical LC-MS/MS analysis. This assay is more sensitive than previously described radioimmunoassays and offers the ability to quantitate both forms of 25-hydroxy vitamin D. The assay involves no chemical derivitization, has a linear measurement range of 20-1500 pg/mL and displays imprecision (CVs) below 7 % at various concentrations across the analytical measurement range.

Disease activity, proteinuria, and vitamin D status in children with systemic lupus erythematosus and juvenile dermatomyositis

OBJECTIVE

To evaluate relationships among vitamin D, proteinuria, and disease activity in pediatric systemic lupus erythematosus (SLE) and juvenile dermatomyositis (JDM).

STUDY DESIGN

Multiple linear regression was used to associate subject-reported race, sunscreen use, and vitamin D intake with physician-assessed disease activity and serum 25-hydroxyvitamin D (25[OH]D) in 58 subjects with pediatric SLE (n=37) or JDM (n=21). Serum 25(OH)D was correlated with urinary vitamin D binding protein/creatinine ratio (DBP/C) and other indicators of proteinuria.

RESULTS

Serum 25(OH)D levels in subjects with SLE were inversely associated with the natural log of urinary DBP/C (r=-0.63, P<.001) and urine protein to creatinine ratio (r=-0.60, P<.001), with an adjusted mean 10.9-ng/mL (95% CI, 5.1-16.8) decrease in 25(OH)D for those with proteinuria. Excluding subjects with proteinuria, serum 25(OH)D levels were inversely associated with disease activity in JDM, but not in SLE. Overall, 66% of all subjects were taking concurrent corticosteroids, but this was not associated with 25(OH)D levels.

CONCLUSIONS

Low serum 25(OH)D in patients with SLE is associated with proteinuria and urinary DBP. Vitamin D deficiency is associated with disease activity in patients with JDM and SLE; this relationship in SLE may be confounded by proteinuria.

Vitamin D and cancer: clinical aspects

There are substantial preclinical and epidemiologic data that suggest that vitamin D plays a role in the prevention and treatment of cancer. Numerous observational studies have shown that low blood levels of 25(OH) vitamin D (cholecalciferol), estimated by geographical location, diet and activity assessment or measured serum levels are associated with a higher risk of cancer and worse cancer-specific survival as well as numerous morbidities to e.g. cardiovascular disease, stroke, infection, autoimmune disease, and neuromuscular dysfunction among large populations. A considerable number of in vitro and in vivo studies indicate that the most active metabolite of vitamin D--1,25-dihydroxycholecalciferol or calcitriol--has anti-proliferative, pro-apoptotic, pro-differentiating, and anti-angiogenic properties. Combined treatment of calcitriol and many types of cytotoxic agents has synergistic or at least additive effects. However, clinical trials testing these hypotheses have been less encouraging, though a number of methodological, pharmacological, and pharmaceutical issues confound all trials ever conducted. In order to properly assess the clinical value of vitamin D, its metabolites and analogs in cancer prevention and treatment, more studies are needed.

Serum vitamin D and risk of bladder cancer

Vitamin D may protect against several cancers, but data about the association between circulating vitamin D and bladder cancer are limited. Within the Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study, a randomized controlled trial conducted to determine the effects of α-tocopherol and β-carotene supplements on cancer incidence in male smokers, 250 bladder cancer cases were randomly sampled by month of blood collection. Controls were matched 1:1 to cases on age at randomization and date of blood collection. Conditional logistic regression was used to estimate odds ratios (OR) and 95% confidence intervals (CI) of bladder cancer by a priori categories of baseline serum 25-hydroxyvitamin D [25(OH)D; i.e., <25, 25 to <37.5, 37.5 to <50, ≥50 nmol/L] and by season-specific quartiles. After multivariable adjustment, we found that lower 25(OH)D was associated with a statistically significantly increased risk of bladder cancer (versus ≥50 nmol/L; <25 nmol/L: OR, 1.73; 95% CI, 1.03-2.91; 25 to <37.5 nmol/L: OR, 1.81; 95% CI, 1.05-3.14; 37.5 to <50 nmol/L: OR, 1.76; 95% CI, 1.02-3.02; P trend=0.04). Similarly, increased risks for the lowest vitamin D category were observed when season-specific quartiles were used (Q1 versus Q4: OR, 1.63; 95% CI, 0.96-2.75; P trend=0.03). In this prospective study of male smokers, lower serum 25(OH)D was associated with an increased risk of bladder cancer. Future studies should examine the association in other populations, especially nonsmokers and women.

Vitamin D status and impact of vitamin D3 and/or calcium supplementation in a randomized pilot study in the Southeastern United States

OBJECTIVE

Vitamin D supplementation may be required for certain subgroups in the United States in whom status and intake are inadequate, but the impact of various doses, and whether calcium administration jointly or independently influences vitamin D metabolite levels, is unclear.

METHODS

In a pilot chemoprevention trial of biomarkers of risk for colorectal adenoma, we measured the impact of vitamin D supplementation and/or calcium supplementation on plasma vitamin D metabolite concentrations. Ninety-two adult men and women living in the southeastern United States were randomized to 800 IU vitamin D(3), 2000 mg elemental calcium, both, or placebo daily for 6 months. We examined vitamin D status at baseline and postintervention and compared the change in plasma 25-hydroxyvitamin D (25(OH)D) and 1,25(OH)(2)D levels by intervention group using general linear models.

RESULTS

Eighty-two percent of the study population had insufficient plasma 25(OH)D concentrations (<75 nmol/L) at baseline, with the lowest levels observed among African American participants. Vitamin D supplements, with or without calcium supplementation, raised plasma 25(OH)D concentrations, on average, by 25 to 26 nmol/L. Half of the study participants were classified as having sufficient 25(OH)D status after 6 months of 800 IU of vitamin D(3) daily. Calcium alone did not influence 25(OH)D concentrations.

CONCLUSION

In this southeastern U.S. population, half of the study participants receiving 800 IU vitamin D(3) daily had blood 25(OH)D concentrations of Collapse

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MESH Headings

• Aged
• Alleles
• Analysis of Variance
• Calcium/administration & dosage
• Chi-Square Distribution
• Cholecalciferol/administration & dosage
• Dietary Supplements
• Double-Blind Method
• Female
• Genotype
• Georgia
• Humans
• Male
• Medication Adherence
• Middle Aged
• Pilot Projects
• Polymorphism, Single Nucleotide
• Receptors, Calcitriol/genetics
• Surveys and Questionnaires
• Treatment Outcome
• Vitamin D/analogs & derivatives
• Vitamin D/blood

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Grants

• R01 CA104637 NCI NIH HHS
• R03 CA121873 NCI NIH HHS

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Affiliation(s)

Marjorie L McCullough Epidemiology Research Program, American Cancer Society, Atlanta, Georgia 30303-1002, USA.
Roberd M Bostick
Carrie R Daniel
W Dana Flanders
Aasma Shaukat
Jill Davison
Udaya Rangaswamy
Bruce W Hollis

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Collaborators Collapse

High dietary cholecalciferol increases plasma 25-hydroxycholecalciferol concentration, but does not attenuate the hypertension of Dahl salt-sensitive rats fed a high salt diet

The Dahl salt-sensitive rat, a model for salt-induced hypertension, develops hypovitaminosis D during high salt intake, which is caused by loss of protein-bound vitamin D metabolites into urine. We tested the hypothesis that high dietary cholecalciferol (5- and 10-fold standard) would increase plasma 25-hydroxycholecalciferol (25-OHD(3)) concentration (indicator of vitamin D status) of salt-sensitive rats during high salt intake. Salt-sensitive rats were fed 0.3% salt (low salt, LS), 3% salt (HS), 3% salt and 7.5 microg cholecalciferol/d (HS-D5), or 3% salt and 15 microg cholecalciferol/d (HS-D10) and sacrificed at week 4. Plasma 25-OHD(3) concentrations of the two groups of HS-D rats were similar to that of LS rats and more than twice that of HS rats. Urinary cholecalciferol metabolite content of HS-D rats was more than seven times that of HS rats. Systolic blood pressures of the hypertensive HS and HS-D rats did not significantly differ, whereas LS rats were not hypertensive. We conclude that high dietary cholecalciferol increases plasma 25-OHD(3) concentration, but does not attenuate the hypertension of salt-sensitive rats during high salt intake. Low salt intake may be necessary to both maintain optimal vitamin D status and prevent hypertension in salt-sensitive individuals.