Vitamin D receptor gene polymorphism and bone mineral density in 0-6-year-old Han children

Association of Vitamin D Receptor BsmI Gene Polymorphism with BMD Z-Score in Iranian Children and Adolescents (9 - 18 Years Old)

BACKGROUND

The vitamin D receptor (VDR) gene variants are known as the main risk factor for low bone mass.

OBJECTIVES

In this study, the association of vitamin D receptor genetic variants, BsmI (rs1544410) and FokI (rs2228570), with bone mass in Iranian children and adolescents, was evaluated.

METHODS

The study population comprised of children and adolescents aged between 9 to 18 years (FokI: 123 boys and 120 girls, BsmI: 108 boys and 110 girls). Vitamin D, calcium, phosphorus, total cholesterol (TC), High-density lipoprotein-cholesterol (HDL-C) and triglyceride (TG) concentrations were assayed. Bone mineral density and body composition parameters were measured by the Hologic system DXA. BMD Z-score ≤ -2 was considered as low bone density for chronologic age. PCR-restriction fragment length polymorphism was done for genotyping of BsmI and FokI polymorphisms. The association between VDR variants and bone mineral density was investigated using logistic regression analysis.

RESULTS

No significant differences in body composition and biochemical parameters were detected among the evaluated VDR genotypes. For VDR BsmI, the mean values for Z-score of the lumbar spine, neck, inter and total femur was greater in the bb genotype compared to BB and Bb genotypes. Logistic regression analysis revealed a significant association between femoral neck Z-score and VDR BsmI genotypes in an additive genetic model (unadjusted model (P = 0.035; Bb vs. bb), model 1 (adjusted for age and sex, P = 0.021; Bb vs. bb), model 2 (adjusted for age, sex and BMI, P = 0.013; Bb vs. bb) and model 3 (adjusted for age, sex, BMI and puberty, P = 0.011; Bb vs. bb, P = 0.049; BB vs. bb)) and dominant genetic model ((unadjusted model, P = 0.033; BB+Bb vs. bb), model 1 (adjusted for age and sex, P = 0.023; BB+Bb vs. bb), model 2 (adjusted for age, sex and BMI, P = 0.012; BB+Bb vs. bb and model 3 (adjusted for age, sex, BMI and puberty, P = 0.012; BB+Bb vs. bb)).

CONCLUSIONS

This investigation indicated that VDR BsmI polymorphism may be associated with BMD Z-score of the femoral neck but not the lumbar spine, in Iranian children and adolescents.

Relationships between serum 25-hydroxyvitamin D and quantitative ultrasound bone mineral density in 0-6 year old children

The relationship between serum 25-hydroxyvitamin D and quantitative ultrasound bone mineral density in young children remains unclear. In addition, consensus has not been reached with regard to the concentration of 25(OH)D to define vitamin D deficiency for infants and children. In the present study, 203 children 0-6 years old were recruited in Shanghai, China. The concentrations of serum 25(OH)D, weight, length, and quantitative ultrasound bone mineral density (BMD) of left mid-tibia were determined. Low BMD was defined as <20th percentile of given age and sex. Low 25(OH)D was defined as 25(OH)D<20 ng/ml. The results showed that median serum 25(OH)D level was 19.0 ng/ml, and 58.6% had a serum 25(OH)D below 20 ng/ml. After adjusting for potential confounders, a linear relationship between serum 25(OH)D and BMD was observed. Serum 25(OH)D was positively associated with BMD (ß=323.3, 95% CI=201.0-445.7, p<0.001), and low 25(OH)D (<20 ng/ml) had a high risk for low BMD (OR=5.5, 95% CI=2.5-12). In addition, there is a nonlinear relationship between 25(OH)D and low BMD, and a threshold for 25(OH)D of 20 ng/ml existed for low BMD. The prevalence of low BMD was 47.1% in the group of 25(OH)D<20 ng/ml, much higher than 16.7% in the group of 25(OH)D ≥ 20 ng/ml (p<0.05). The results suggested that quantitative ultrasound BMD could be an indicator for vitamin D status in young children, and also provided further evidence to define vitamin D deficiency for infants and children.

Vitamin D receptor gene polymorphism and its association with Parkinson's disease in Chinese Han population

Vitamin D plays an important role in neurodegenerative disorders as a crucial neuro-immunomodulator, and accumulating data have provided evidence for that vitamin D receptor (VDR) gene is a candidate gene for susceptibility to Parkinson's disease (PD). In this study, we performed a case-control study to demonstrate whether the risk for the development of onset of sporadic PD might be influenced by VDR gene polymorphisms in a Chinese cohort. Two hundred and sixty PD patients and 282 matched-healthy controls were genotyped for two representative single nucleotide polymorphisms (SNPs) in VDR gene (FokI C/T and BsmI G/A) by polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) analysis in. Results from our study revealed that FokI C allele carriers were likely to associate with an increased risk of PD (P=0.004) as well as early-onset PD (EOPD) (P=0.010). Moreover, the frequency of FokI C allele was significantly increased in PD group and late-onset PD (LOPD) group relative to the control groups respectively (P=0.023 and P=0.033, respectively). For BsmI polymorphisms, no significant difference in genotype or allele distribution was found between PD patients and the controls, as well as gender- and age-related differences between PD patients and the controls subgroup. This study demonstrated a possible association between the VDR FokI T/C polymorphism and PD, indicating that VDR polymorphisms may well change genetic susceptibility to sporadic PD in a Han Chinese population.

Tanning predicts bone mass but not structure in adolescent females living in Hawaii

OBJECTIVES

To evaluate the relationship between facultative skin pigmentation, which predicts circulating levels of plasma 25-hydroxymitamin D, and several measures of bone mass and structure in a cross sectional sample of adolescent females living in Hawaii.

METHODS

Our sample was composed of adolescent females (n = 94) living in Hawaii where seasonal sun exposure is minimal, and who self-identified as either white (n = 16) or Asian (n = 78). Bone mineral content (BMC) of the total body, the lumbar spine and the hip, and cross sectional area (CSA) and section modulus (Z) at the proximal femur were quantified using DXA. Facultative skin pigmentation was measured at the forehead and non-facultative skin pigmentation was measured at the inner arm using a Chroma Meter CR-200b colorimeter.

RESULTS

There were no significant differences between ethnic groups in terms of skin pigmentation. The difference between a* taken at the forehead and inner upper arm significantly predicted BMC at the lumbar spine, total hip, and total body. Other measures of skin pigmentation were not significant predictors of any other measure of skeletal integrity.

CONCLUSIONS

The difference between facultative and non-facultative skin pigmentation for a* is a significant predictor BMC, but not bone structure. Our findings are limited by an inability to control for long term UVA and UVB exposure and lack of a measure of serum 25(OH)D status. Further research is needed to examine these questions, particularly in populations who live at high latitudes where a winter season limits vitamin D(3) synthesis.