cholecalciferol and Hyperemia

We sought to determine if vitamin D supplementation, to target 25(OH)D concentrations of 30-40 ng/mL, improves endothelial function in Singapore's multi-ethnic type 2 diabetes mellitus population. We randomised 64 type 2 diabetes mellitus patients with hypovitaminosis D to cholecalciferol 4000 International Unit/matching placebo [baseline 25(OH)D < 20 ng/mL] or cholecalciferol 2000 International Unit/matching placebo [baseline 25(OH)D: 20-30 ng/mL] daily for 16 weeks with a down titration at 8 weeks if 25(OH)D > 30 ng/mL. Endothelial function was assessed by peripheral tonometry (reactive hyperaemia index-endothelial peripheral arterial tonometry) and vascular biomarkers: E-selectin, von-Willebrand factor and high-sensitivity C-reactive protein. We compared the change from baseline parameters in the two groups using Student's t-test or Kruskal-Wallis test. A log-normal multivariate regression analysis was used to adjust for relevant baseline variables. The median reactive hyperaemia index in the vitamin D group increased from 0.65 (interquartile range: 0.42) to 0.73 (interquartile range: 0.36), whereas it decreased from 0.73 (interquartile range: 0.65) to 0.65 (interquartile range: 0.38) (p = 0.02) in the placebo group. After adjustment for baseline variables, the change was not statistically significant for reactive hyperaemia index (p = 0.07) and for other vascular biomarkers (p > 0.05). Targeted vitamin D supplementation for 16 weeks resulted in a small but non-significant improvement in endothelial function in a type 2 diabetes mellitus cohort.

Topics: Adult; Aged; Biomarkers; Cholecalciferol; Diabetes Mellitus, Type 2; Diabetic Angiopathies; Dietary Supplements; Double-Blind Method; Endothelium, Vascular; Female; Humans; Hyperemia; Male; Middle Aged; Singapore; Tertiary Care Centers; Time Factors; Treatment Outcome; Vasodilation; Vitamin D; Vitamin D Deficiency

Although altered cellular calcium handling plays a critical role in the pathophysiology of hypertension, little attention has been focused on the impact of calcium regulating hormones on target-organs (e.g. vascular tissue). Therefore the relationship between calcium, phosphorus, parathyroid hormone, 25- and 1,25-(di) hydroxyvitamin D3, blood pressure (BP) and regional circulation was examined in 25 patients (44 +/- 2.5 years) with moderate hypertension (systolic BP 164 +/- 4 mmHg, diastolic BP 105 +/- 2 mmHg). Calf and finger blood flow were measured simultaneously using ECG-triggered plethysmography at rest and after 3 min arterial occlusion (reactive hyperemia). Systolic and diastolic BP were inversely correlated with 25-hydroxyvitamin D3 (r = -0.511 and r = -0.445, p < 0.002). Calf vascular resistance at rest (r = -0.46, p = 0.02) and after 3 min arterial occlusion (r = -0.78, p = 0.0001) was related to 25-hydroxyvitamin D3 concentration. Only calf vascular resistance during reactive hyperemia was significantly related to 1,25-dihydroxyvitamin D3 (r = -0.44, p = 0.03). After correction for blood pressure calf vascular resistance after 3 min arterial occlusion remained significantly and inversely related with 25-hydroxyvitamin D3. There was no relation between finger (skin) circulation and vitamin D3. All other calcium regulating factors were unrelated to the parameters of peripheral circulation. Our results indicate that among the calcium regulating factors, particularly vitamin D3 seems to inversely influence muscle, but not skin vascular tone-independently of blood pressure in mild to moderate hypertension.

Topics: Adult; Blood Pressure; Calcifediol; Calcitriol; Calcium; Cholecalciferol; Electrocardiography; Female; Humans; Hyperemia; Hypertension; Magnesium; Male; Middle Aged; Muscles; Organ Specificity; Parathyroid Hormone; Phosphorus; Plethysmography; Regional Blood Flow; Skin; Vascular Resistance