The new Roche Vitamin D Total assay: fit for its purpose?

Associations between serum 25-hydroxyvitamin D and bone turnover markers in a population based sample of German children

Severe vitamin D deficiency is known to cause rickets, however epidemiological studies and RCTs did not reveal conclusive associations for other parameters of bone health. In our study, we aimed to investigate the association between serum levels of 25(OH) vitamin D and bone turnover markers in a population-based sample of children. 25(OH)D, calcium (Ca), osteocalcin (OC), and β-Crosslaps (β-CTx) were measured in 2798 ten-year-old children from the German birth cohorts GINIplus and LISAplus. Linear regression was used to determine the association between bone turnover markers and 25(OH)D levels. 25(OH)D, OC, and β-CTx showed a clear seasonal variation. A 10 nmol/l increase in 25(OH)D was significantly associated with a 10.5 ng/l decrease (p < 0.001) in β-CTx after adjustment for design, sex, fasting status, time of blood drawn, BMI, growth rate, and detectable testosterone/estradiol. For OC alone no significant association with 25(OH)D was observed, whereas the β-CTx-to-OC ratio was inversely associated with 25(OH)D (−1.7% change, p < 0.001). When stratifying the analyses by serum calcium levels, associations were stronger in children with Ca levels below the median. This study in school-aged children showed a seasonal variation of 25(OH)D and the bone turnover markers OC and β-CTx. Furthermore a negative association between 25(OH)D and the bone resorption marker β-CTx was observed.

Vitamin D as a risk factor for premature atherosclerosis in patients with type 2 diabetes

BACKGROUND

Several cardiovascular risk factors have been recognized in patients with diabetes and vitamin D deficiency is emerging as a new risk. The aim of this study was to determine the effect of vitamin D deficiency on the incidence of premature atherosclerosis in patients with type 2 diabetes.

METHODS

A total of 78 patients with type 2 diabetes were subjected to history taking, physical examination, fasting glucose level, homeostasis model assessment of insulin resistance, lipid profile, 25(OH) vitamin D measurement, and carotid Doppler.

RESULTS

Patients with normal carotid intima-media thickness (CIMT) had sufficient vitamin D. Of those with increased CIMT 23.1% had insufficient vitamin D while 76.9% had sufficient vitamin D (six patients had plaques, one of them had vitamin D insufficiency, and the other five patients had sufficient vitamin D). There was a statistically significant difference in the serum level of vitamin D between patients with increased CIMT, and those with normal intima, with a decreased level in the first group. There was a significant negative correlation between vitamin D and fasting blood glucose. There was a statistically significant correlation in left CIMT between the vitamin D sufficiency group and the vitamin D insufficiency group, with higher values in the second group. There was no statistically significant difference in serum cholesterol, triglycerides, HDL cholesterol, and LDL cholesterol in patients with increased CIMT and those with normal intima.

CONCLUSIONS

Decreased vitamin D levels in patients with diabetes lead to increased CIMT. The absence of a statistically significance difference in lipid profile between increased and normal CIMT groups raises the possibility of underlying causes for atherosclerosis in patients with diabetes other than dyslipidemia.

Vitamin D deficiency and its characteristics among patients with acute stroke at a national referral hospital in Kampala Uganda

BACKGROUND

Vitamin D deficiency has been associated with acute stroke and other cardiovascular diseases in the developed world. Low 25-hydroxyvitamin D (25OHD) has been described in some populations in Sub-Saharan Africa (SSA) in spite of adequate sunshine all year round. There is no information on the magnitude of vitamin D deficiency among patients with stroke and other cardiovascular diseases in Uganda or SSA. The aim of this study was to determine the burden and characteristics of vitamin D deficiency among patients with acute stroke, the most common form of cardiovascular events in SSA.

METHODS

We conducted a cross-sectional study between October 2012 and March 2013. We consecutively recruited 142 subjects with acute stroke admitted to the medical wards of Mulago hospital. We administered a pre-tested questionnaire to the study participants, and did a detailed physical examination and laboratory evaluation. Serum levels of 25OHD were determined using an electrochemiluminescence assay. Data were analyzed using STATA version 12 software.

RESULTS

The prevalence of vitamin D deficiency (25OHD < 20 ng/ml) was 15 %. Longer hours of sunshine exposure decreased the likelihood vitamin D deficiency significantly (adjusted OR 0.85, p = 0.03). Higher HDL cholesterol had a significant inverse association with vitamin D deficiency (adjusted OR 0.15, p = 0.02). In addition, the likelihood of vitamin D deficiency increased with rising age (adjusted OR 1.03, p = 0.05).

CONCLUSIONS

There was a relatively low burden of vitamin D deficiency among patients with acute stroke in Uganda. With increasing longevity and indoor lifestyles vitamin D deficiency may assume a greater role in stroke and other cardiovascular diseases in tropical sub Saharan Africa. Future studies on the mechanisms of vitamin D deficiency and its relationship to outcomes among patients with stroke may be necessary.

Associations between 25-hydroxyvitamin D levels and pregnancy outcomes: a prospective observational study in southern China

BACKGROUND/OBJECTIVES

Observational studies relating 25-hydroxyvitamin D (25(OH)D) and pregnancy outcomes have reported conflicting results. The aim was to assess maternal 25(OH)D status and its association with pregnancy outcomes. A prospective observational study was carried out in Guangzhou city (23 ºN), China.

SUBJECTS/METHODS

Pregnant women (n=2960) and healthy controls (n=100) were recruited at a teaching hospital. Maternal 25(OH)D levels were measured at 16-20-week gestation. The pregnant women, if met inclusion and exclusion criteria, were enrolled in further analysis for pregnancy outcomes (n=1953).

RESULTS

Mean serum 25(OH)D in pregnant women was 27.03±7.92 ng/ml. In total, 18.9 and 48.6% of pregnant women had low (25(OH)D less than or equal to 20 ng/ml) and medium level (25(OH)D 21-29 ng/ml) of vitamin D, respectively. 25(OH)D was highest in summer and lowest in winter, which showed a positive correlation with temperature (R=0.942) and calcium (R=0.074). Most maternal outcomes (premature rupture of membranes break, polyhydramnios, oligohydramnios, pre-eclampsia, cesarean section), fetal outcomes (spontaneous abortions, medically induced labor, fetal death, fetal distress, fetal growth restriction) and neonatal outcomes (malformations, birth weight and height, low birth weight, macrosomia, small-for-gestational age, score of Apgar 1',5', asphyxia of newborn) were not significantly different between groups, but prevalence of gestational diabetes (adjusted odds ratio (OR) 1.017; 95% confidence interval (CI) 1.002-1.033) and preterm delivery (adjusted OR 1.038; 95% CI 1.018-1.059) in high level group (25(OH)D ⩾30 ng/ml) was higher than that in low and medium level groups.

CONCLUSIONS

The prevalence of low level of vitamin D (serum 25OHD ⩽20 ng/ml) was 18.9% among pregnant women in southern China. There were no significant differences in most adverse pregnancy outcomes among pregnant women with different levels of vitamin D at 16-20-week gestation except for higher prevalence of gestational diabetes and preterm delivery in women with high level of vitamin D, possibly related to the older age and higher body mass index of this group.

Vitamin D deficiency in childhood obesity is associated with high levels of circulating inflammatory mediators, and low insulin sensitivity

HYPOTHESIS

Childhood obesity is accompanied by low-grade systemic inflammation, which contributes to the development of insulin resistance and cardiovascular complications later in life. As vitamin D exhibits profound immunomodulatory functions and vitamin D deficiency is highly prevalent in childhood obesity, we hypothesized that vitamin D deficiency in childhood obesity coincides with enhanced systemic inflammation and reduced insulin sensitivity.

METHODS

In a cross-sectional study of 64 obese and 32 healthy children aged 6-16 years, comprehensive profiling of 32 circulating inflammatory mediators was performed, together with assessment of 25-hydroxyvitamin D (25(OH)D) levels and measures for insulin sensitivity.

RESULTS

Severe vitamin D insufficiency, which is further referred to as vitamin D deficiency, was defined as a 25(OH)D level ≤37.5 nmol l(-1), and was highly prevalent in obese (56%) versus healthy control children (16%). Throughout the study, 25(OH)D-deficient children were compared with the other children, including 25(OH)D insufficient (37.5-50 nmol l(-1)) and 25(OH)D sufficient children (≥50 nmol l(-1)). First, 25(OH)D-deficient obese children showed a lower insulin sensitivity than other obese children, as measured by a lower quantitative insulin sensitivity check index. Second, the association between 25(OH)D deficiency and insulin resistance in childhood obesity was confirmed with multiple regression analysis. Third, 25(OH)D-deficient obese children showed higher levels of the inflammatory mediators cathepsin S, chemerin and soluble vascular adhesion molecule (sVCAM), compared with the other obese children. Finally, hierarchical cluster analysis revealed an over-representation of 25(OH)D deficiency in obese children expressing inflammatory mediator clusters with high levels of cathepsin S, sVCAM and chemerin.

CONCLUSION

25(OH)D deficiency in childhood obesity was associated with enhanced systemic inflammation and reduced insulin sensitivity. The high cathepsin S and sVCAM levels may reflect activation of a pro-inflammatory, pro-diabetic and atherogenic pathway, which could be inhibited by vitamin D supplementation.