Vitamin D Supplementation Reduces Renin-Angiotensin System Activity in Obesity

Vitamin D Deficiency Augments Renin-Angiotensin System Activity in Obesity

Hypothesis: Vitamin D supplementation lower renin-angiotensin system activity in obesity.

Specific Aim: To investigate whether Vitamin D supplementation in obesity improves the vascular sensitivity to angiotensin II.

Vitamin D deficiency and obesity are international epidemics that have both been associated with increased activity of the renin-angiotensin system (RAS). Because increased RAS activity is associated with cardiovascular disease, interventions to lower RAS will have favorable public health impacts.

This study aims to evaluate whether the supplementation of Vitamin D in obese subjects will lower local tissue RAS activity. RAS activity will be evaluated by cross-sectional measurement of RAS components and by quantifying the vascular response to an infusion of angiotensin II. Subjects will be studied while Vitamin D deficient, and will return for repeat study following Vitamin D supplementation, for comparison.

Inclusion Criteria:

• age < 65,
• Cr < 1.6,
• 25-hydroxyvitamin D < 25 ng/mL,
• BMI > 30 kg/m2,
• stage I hypertension.

Exclusion Criteria:

• diabetes,
• coronary heart disease,
• heart failure,
• renal failure,
• liver failure,
• hyperparathyroidism,
• granulomatous disease.