Vitamin D receptor activation is associated with improved survival in patients with
chronic kidney disease, but the mechanism of this benefit is unclear. To better understand the effects of
vitamin D on endothelial function, blood pressure,
albuminuria, and
inflammation in patients with
chronic kidney disease (2 patients stage 2, remaining stage 3), we conducted a pilot trial in 24 patients who were randomly allocated equally to 3 groups to receive 0, 1, or 2 microg of
paricalcitol, a
vitamin D analog, orally for 1 month. Placebo-corrected change in flow mediated dilatation with a 1-microg dose was 0.5% and 0.4% with a 2-microg dose (P>0.2). At 1 month, the treatment:baseline ratio of
high sensitivity C-reactive protein was 1.5 (95% CI: 1.1 to 2.1; P=0.02) with placebo, 0.8 (95% CI: 0.3 to 1.9; P=0.62) with a 1-microg dose, and 0.5 (95% CI: 0.3 to 0.9; P=0. 03) with a 2-microg dose of
paricalcitol. At 1 month, the treatment:baseline ratio of 24-hour
albumin excretion rate was 1.35 (95% CI: 1.08 to 1.69; P=0.01) with placebo, 0.52 (95% CI: 0.40 to 0.69; P<0.001) with a 1-microg dose, and 0.54 (95% CI: 0.35 to 0.83; P=0. 01) with a 2-microg dose (P<0.001 for between group changes). No differences were observed in
iothalamate clearance, 24-hour ambulatory blood pressure, or
parathyroid hormone with treatment or on washout. Thus,
paricalcitol-induced reduction in
albuminuria and
inflammation may be mediated independent of its effects on hemodynamics or
parathyroid hormone suppression. Long-term randomized, controlled trials are required to confirm these benefits of
vitamin D analogs.