Low serum 25-Hydroxy (OH) vitamin D levels are associated with increased arterial stiffness in healthy children: An echocardiographic study from Turkey

OBJECTIVE

Arterial stiffness refers to arterial wall rigidity, particularly in central vessels, and is an independent predictor of cardiovascular disease in many chronic diseases. 25-Hydroxy (OH) vitamin D has beneficial effects on blood pressure, vascular endothelial function, and arterial stiffness; most importantly, its deficiency is common worldwide. Therefore, we aimed to elucidate the role of 25-OH vitamin D deficiency in arterial stiffness development and its relationship with arterial stiffness in healthy children.

METHODS

This study included 80 patients with low levels of 25-OH vitamin D and 40 healthy control subjects. The study participants were then divided into three groups: group 1 consisted of patients with a deficient 25-OH D level of < 19.9 ng/ml, group 2 with an insufficient 25-OH D level between 20 and 29.9 ng/ml; group 3 were considered control group with a sufficient serum 25-OH vitamin D level of ≥30 ng/ml. Aortic strain, distensibility, stiffness index, and standard left ventricular measurements were calculated using M-mode echocardiographic data.

RESULTS

Left ventricular mass index (LVMI) and inter-ventricular septal diastolic thickness (IVST) appeared to increase in group 1 compared to groups 2 and 3. Aortic strain and distensibility were significantly decreased in group 1, whereas aortic stiffness index and elastic modulus were significantly increased. The aortic stiffness index was negatively correlated with serum 25-OH vitamin D levels; however, aortic strain, aortic distensibility, and LVMI were positively correlated.

CONCLUSIONS

Our study results revealed a significant relationship between 25-OH vitamin D levels indicative of a deficiency and aortic stiffness. Hence, we suggest that arterial stiffness may also occur in healthy children with a 25-OH vitamin D deficiency. Future in-depth studies are needed to understand the exact mechanisms underlying the aortic stiffness development associated with 25-OH vitamin D deficiency.

Vitamin D Levels, Body Composition, and Metabolic Factors in Asian Indians: Results from the Metabolic Syndrome and Atherosclerosis in South Asians Living in America Pilot Study

BACKGROUND/AIMS

Asian Indians have a high prevalence of vitamin D deficiency and metabolic syndrome. Vitamin D deficiency is associated with an increased risk of cardiovascular disease and diabetes.

METHODS

We performed a cross-sectional study of 150 Asian Indians (50% male) from the San Francisco Bay Area. We assessed the association between 25-OH vitamin D (25-OHD) levels and vitamin D deficiency with body composition (anthropometric and radiographic measures) and metabolic outcomes.

RESULTS

In both men and women, the presence of vitamin D deficiency was associated with higher systolic (p = 0.004) and diastolic (p = 0.01) blood pressure, and fasting glucose (p = 0.01). Only in women, vitamin D deficiency status was associated with higher body mass index (BMI), waist-to-hip ratio, visceral fat area, and hepatic fat content after adjusting for age, income, and physical activity level. In women, 25-OHD was also associated with fasting glucose after adjusting for age, income, and physical activity and further adjusting for BMI and waist circumference (β -2.1, 95% CI -0.86 to -0.01, p = 0.04). This association between vitamin D deficiency and metabolic parameters was not significant in men.

CONCLUSIONS

A lower level of 25-OHD and vitamin D deficiency were associated with higher levels of metabolic factors among Asian Indians. Our findings suggest that 25-OHD metabolism may differ by the distribution of adipose tissue and involve previously unexplored pathways accounting for the variability in the role of vitamin D in cardiovascular disease.

Evaluation of the analytical performance of Unicel DXI 800 for the Total 25 (OH) Vitamin D measurements

OBJECTIVES

We assessed the analytical performance of newly developed Access 25(OH) Vitamin D Total assay with Beckman Coulter Unicel DXI 800 and evaluated the agreement between a reference method liquid chromatography/tandem mass spectrometry (LC-MS/MS) and a chemiluminescence method (LIAISON, DiaSorin).

DESIGN AND METHODS

160 serum samples were included. Deming Regression analysis and Bland-Altman plots were used. The concordance correlation coefficient (CCC) was used to assess the degree of agreement between assays and the reference method.

RESULTS

The CV% values of Unicel DXI 800 for within-run, between-run and between-day were lower than 6%. When compared to LC-MS/MS, the Access 25(OH) Vitamin D Total assay demonstrated an R value of 0.9444 (intercept -0.089, slope 0.951), with an average bias of -2.9%, and the LIAISON 25(OH) Vitamin D Total assay an R value of 0.9405 (intercept -0605, slope 0.924), with an average bias of -13.6%. In comparison with the LIAISON 25(OH) Vitamin D Total assay, the Access 25(OH) Vitamin D Total assay demonstrated an R value of 0.9498 (intercept 0.528, slope 1.029), with an average bias of 1.2%. The agreement with the LC-MS/MS method, based on values of the CCC, was moderate for the Unicel DXI 800 and LIAISON method (0.95, 0.94 respectively).

CONCLUSIONS

The new, automated Access 25(OH) Vitamin D Total assay showed an acceptable correlation with LC-MS/MS and LIAISON. Both methods moderately achieved to classify the patients according to their vitamin D status. However, we need further standardization of vitamin D assays to enhance the accuracy and comparability.