Vitamin D Augmentation of Tekturna (Aliskiren) in Hypertension (VDATH)

In this research study, the goal is to find out if a currently FDA-approved medication called Tekturna(Aliskiren) along with the addition of Vitamin D will lower blood pressure and improve heart function in the African American population. High blood pressure occurs earlier in life in African Americans, is more severe, and is associated with greater organ damage in relation to uncontrolled hypertension. Having low levels of Vitamin D is also very common in the African American population. Research has shown that there may be a link between low Vitamin D levels and the ability of high blood pressure medications to be fully effective.

The overarching hypothesis is that African Americans with hypertension have an overactive RAS (Renin Angiotensin System) in the body that is responsible for internally regulating blood pressure. Many blood pressure medications change regulation of the RAS system in order to keep blood pressure down. The purpose of this research study is to determine whether or not African American adults with hypertension have an overactive RAS system due to Vitamin D deficiency, resulting in the inability of the medication Tekturna to lower blood pressure. In this study, all participants will receive 300mg of Tekturna per day. Additionally half of the participants will randomly be selected to receive either 50,000 IU of Vitamin D (in its cholecalciferol form) orally once every other week or a vitamin D placebo once every other week. There will be 4 study visits over 18 weeks and follow up phone calls every two weeks for the duration of the study. Specific Aims: To demonstrate in African American Hypertensives consuming a calcium replete diet that Tekturna + Vitamin D will lower blood pressure more than Tekturna + placebo. To demonstrate in African American hypertensives consuming a calcium replete diet that albuminuria will be lowered more with Tekturna + Vitamin D versus Tekturna + placebo. To demonstrate in African American hypertensives consuming a calcium replete diet that Tekturna + Vitamin D will improve measures on non-invasively measured vascular function (peripheral vascular resistance, augmentation index, carotid-femoral pulse wave velocity and central aortic pressure) more than Tekturna + placebo.

Inclusion Criteria: Ages 30-74 Systolic Blood Pressure 140-159 mm Hg and Diastolic Blood Pressure <100 OR Diastolic Blood Pressure 90-99mm Hg and Systolic Blood Pressure <160mm Hg Vitamin D deficiency: Serum 25-OH D >= 10 ng/ml (25 nmol/L) to < 20 ng/ml (50 nmol/L) Not using any antihypertensive medication(s) for the previous 3 months Exclusion Criteria: Cancer(other than skin) known HIV or other medical condition that might limit life expectancy. Pregnant or nursing Know adverse reactions to DRI's Hepatitis or liver enzyme elevations > 1.5x normal Estimated glomerular filtration rate (EGFR) <50 ml/min/1.7m2 Diabetes Mellitus Serum calcium > 10.5 mg/dl or history of hypercalcemia History of primary hyperparathyroidism Sarcoidosis or other granulomatous disease Taking > 500 mg/d of supplemental elemental calcium Taking any drugs that decrease absorption of vitamin D, ex:xenical Taking the drug cyclosporine Taking any antihypertensive medications in the previous 3 months History of kidney stones Planning to move > 50 miles in the next 9 months