Vitamin D Supplementation for Treatment of Heart Failure

Primary Objective To determine how rapid vitamin D supplementation affects biomarkers and submaximal exercise capacity in systolic HF patients with low vitamin D status. Working Hypothesis 1: HF patients when supplemented with vitamin D for 6 months will have lower measures of inflammation and extracellular-matrix remodeling compared with placebo. Working Hypothesis 2: HF patients when supplemented with vitamin D for 6 months will have longer 6-minute walk length compared with placebo. Secondary Objectives To establish a relationship between the CYP2R1 variant and surrogate markers in systolic HF patients. Working Hypothesis 3: HF patients with the CYP2R1 G allele will have higher measures of inflammation and extracellular-matrix remodeling compared to AA subjects. This relationship will also be seen in subjects with the CYP2R1 TagSNP variants. Working Hypothesis 4: HF patients with CYP2R1 variant alleles will have shorter 6-minute walk length compared to subjects without these variants. To genotype HF subjects for the VDR variants and additional tag SNPs, to ascertain the relationship between VDR genetic variation and surrogate markers in systolic HF patients. Working Hypothesis 5: HF patients with VDR variants will have greater measures of inflammation and extracellular-matrix remodeling compared to subjects without VDR variants. Working Hypothesis 6: HF patients with VDR variants will have a shorter 6-minute walk length compared to subjects without these variants.