Vitamin D and bone health in childhood and adolescence

The vitamin D analogue ED71 but Not 1,25(OH)2D3 targets HIF1α protein in osteoclasts

Although both an active form of the vitamin D metabolite, 1,25(OH)₂D₃, and the vitamin D analogue, ED71 have been used to treat osteoporosis, anti-bone resorbing activity is reportedly seen only in ED71- but not in 1,25(OH)₂D₃ -treated patients. In addition, how ED71 inhibits osteoclast activity in patients has not been fully characterized. Recently, HIF1α expression in osteoclasts was demonstrated to be required for development of post-menopausal osteoporosis. Here we show that ED71 but not 1,25(OH)₂D₃, suppress HIF1α protein expression in osteoclasts in vitro. We found that 1,25(OH)₂D₃ or ED71 function in osteoclasts requires the vitamin D receptor (VDR). ED71 was significantly less effective in inhibiting M-CSF and RANKL-stimulated osteoclastogenesis than was 1,25(OH)₂D₃in vitro. Downregulation of c-Fos protein and induction of Ifnβ mRNA in osteoclasts, both of which reportedly block osteoclastogenesis induced by 1,25(OH)₂D₃in vitro, were both significantly higher following treatment with 1,25(OH)₂D₃ than with ED71. Thus, suppression of HIF1α protein activity in osteoclasts in vitro, which is more efficiently achieved by ED71 rather than by 1,25(OH)₂D₃, could be a reliable read-out in either developing or screening reagents targeting osteoporosis.

The importance of body weight for the dose response relationship of oral vitamin D supplementation and serum 25-hydroxyvitamin D in healthy volunteers

Unlike vitamin D recommendations by the Institute of Medicine, the Clinical Practice Guidelines by the Endocrine Society acknowledge body weight differentials and recommend obese subjects be given two to three times more vitamin D to satisfy their body's vitamin D requirement. However, the Endocrine Society also acknowledges that there are no good studies that clearly justify this. In this study we examined the combined effect of vitamin D supplementation and body weight on serum 25-hydroxyvitamin (25(OH)D) and serum calcium in healthy volunteers. We analyzed 22,214 recordings of vitamin D supplement use and serum 25(OH)D from 17,614 healthy adult volunteers participating in a preventive health program. This program encourages the use of vitamin D supplementation and monitors its use and serum 25(OH)D and serum calcium levels. Participants reported vitamin D supplementation ranging from 0 to 55,000 IU per day and had serum 25(OH)D levels ranging from 10.1 to 394 nmol/L. The dose response relationship between vitamin D supplementation and serum 25(OH)D followed an exponential curve. On average, serum 25(OH)D increased by 12.0 nmol/L per 1,000 IU in the supplementation interval of 0 to 1,000 IU per day and by 1.1 nmol/L per 1,000 IU in the supplementation interval of 15,000 to 20,000 IU per day. BMI, relative to absolute body weight, was found to be the better determinant of 25(OH)D. Relative to normal weight subjects, obese and overweight participants had serum 25(OH)D that were on average 19.8 nmol/L and 8.0 nmol/L lower, respectively (P<0.001). We did not observe any increase in the risk for hypercalcemia with increasing vitamin D supplementation. We recommend vitamin D supplementation be 2 to 3 times higher for obese subjects and 1.5 times higher for overweight subjects relative to normal weight subjects. This observational study provides body weight specific recommendations to achieve 25(OH)D targets.

Lifestyle modifications to improve musculoskeletal and bone health and reduce disability--a life-course approach

This review covers the evidence relating to lifestye modification in the big three musculoskeletal conditions: osteoarthritis, osteoporosis and rheumatoid arthritis. Lifestyle is of considerable importance in the first two and there is emerging evidence for rheumatoid arthritis despite it not traditionally being considered a lifestyle disease.

Variations in the vitamin D-binding protein (DBP) gene are related to lower 25-hydroxyvitamin D levels in healthy girls: a cross-sectional study

BACKGROUND/AIMS

Vitamin D deficiency has been recognized as a worldwide epidemic affecting several pediatric and adolescent populations. We determined the genotype and haplotype distribution of the rs4588 and rs7041 polymorphisms of the GC gene encoding vitamin D-binding protein (DBP) and investigated the associations between these gene variants and their haplotypes with 25-hydroxyvitamin D [25(OH)D] levels in girls from South Brazil.

METHODS

Cross-sectional study including 198 apparently healthy girls aged 10-18 years. Plasma levels of 25(OH)D were assessed by radioimmunoassay. Participants were genotyped for rs4588 and rs7041 by real-time PCR, with allelic discrimination assays.

RESULTS

Mean chronological age and BMI percentile were 13.17 ± 1.74 years and 57.81 ± 29.03, respectively. Sufficient circulating 25(OH)D levels (≥30 ng/ml) were found in 9.1% of the overall group, insufficient levels (20-29.9 ng/ml) in 59.6%, and deficient levels (<20 ng/ml) in 31.3%. The AA genotype of rs4588, TT genotype of rs7041 and CT-AT/AT-AT (GC 1f-2/2-2) diplotypes were significantly associated with lower 25(OH)D levels, even after adjustment for age and season at the time of blood collection.

CONCLUSIONS

The GC gene genotype may be related to the susceptibility to low 25(OH)D levels in female children and adolescents.

Maternal vitamin D supplementation to meet the needs of the breastfed infant: a systematic review

Maternal vitamin D insufficiency during lactation, related to lack of sun exposure and minimal intake of vitamin D from the diet, contributes to low breast milk vitamin D content and, therefore, infant vitamin D deficiency. The objective of this review was to examine the literature regarding evidence for achieving maternal vitamin D status that promotes sufficient vitamin D transfer from mother to infant exclusively from breast milk. PubMed and CINAHL databases were searched using the terms lactation or breastfeeding or milk, human and vitamin D. The resulting articles were further limited to those written in English, published within the last 10 years, and involving clinical or randomized controlled trials of humans. The search yielded 13 studies, 3 of which provide evidence for maternal intake of vitamin D and the correlation with exclusively breastfed infants' serum 25-hydroxyvitamin D level. A strong positive correlation exists between maternal vitamin D intake during exclusive breastfeeding and infant serum 25-hydroxyvitamin D levels. There is support to conclude that when maternal vitamin D intake is sufficient, vitamin D transfer via breast milk is adequate to meet infant needs. In the reviewed studies, doses up to 10 times the current recommended daily intake of vitamin D were needed to produce sufficient transfer from mother to breastfed infant. Further research is needed to refine the dose and gestational timing of maternal vitamin D supplementation. Due to the high rates of vitamin D deficiency during lactation and the correlations between vitamin D deficiency and multiple diseases, providers should consider monitoring lactating mothers' vitamin D status.

Efficacy of vitamin D loading doses on serum 25-hydroxy vitamin D levels in school going adolescents: an open label non-randomized prospective trial

AIM

Vitamin D deficiency (VDD) among adolescents is a major health problem in India. The aim of this study was to assess the efficacy of therapeutic/loading doses of vitamin D supplementation on serum 25-hydroxy vitamin D (25OHD) levels in vitamin D deficient adolescents.

METHODS

A total of 482 out of the 511 subjects recruited for the study were divided into three groups, each group receiving 60,000 IU of vitamin D3 weekly for 4, 6 and 8 weeks followed by 600 IU daily for 12 weeks, respectively. Clinical evaluation was followed by estimation of biochemical markers and serum 25OHD levels.

RESULTS

VDD was observed in 94.8% of adolescents. All three vitamin D loading doses were equally efficacious in achieving vitamin D sufficiency >75 nmol/L (>30 ng/mL) in more than 90% subjects in the three groups. Mean 25OHD levels in groups 2 and 3 following maintenance therapy were 67.5±16.5 nmol/L (27.0±6.6 ng/mL) and 70.0±21.8 nmol/L (28.0±8.7 ng/mL), respectively.

CONCLUSION

Supplementing 60,000 IU of vitamin D3 per week for 4-8 weeks, followed by 600 IU daily through fortified milk, is an effective strategy for achieving vitamin D sufficiency in Indian adolescents.