Background: Laboratory research and previous retrospective study suggest that vitamin D and its analogues have profound effects on immune system function and glomerular mesangial cell proliferation. We conducted an open-label study to evaluate the antiproteinuric effect of calcitriol on proteinuria in patients with immunoglobulin A (IgA) nephropathy.
Study design: Open-label prospective uncontrolled trial.
Setting & participants: 10 patients (3 men) with biopsy-proven IgA nephropathy and persistent proteinuria despite angiotensin-converting enzyme-inhibitor or angiotensin receptor blocker therapy in a tertiary referral center.
Intervention: Calcitriol, 0.5 microg, twice weekly for 12 weeks.
Outcome measures: Changes in proteinuria, renal function, serum transforming growth factor beta (TGF-beta) and angiotensin II levels.
Results: After calcitriol treatment, there was a significant overall decrease in proteinuria with time by using a general linear model with repeated measures (P = 0.03). There was a progressive decrease in urine protein-creatinine ratio from 1.98 +/- 0.74 to 1.48 +/- 0.81 g/g (P = 0.007) during the first 6 weeks that persisted throughout the study period. No significant change in blood pressure or renal function was noted. There was a simultaneous decrease in serum TGF-beta level, and percentage of decrease in serum TGF-beta level significantly correlated with percentage of change in proteinuria (Spearman r = 0.643; P = 0.02). Serum angiotensin II level did not change throughout the study. One patient experienced transient hypercalcemia that normalized after a dosage decrease. No other major adverse effect was reported.
Limitations: This small study is uncontrolled and does not examine the long-term effect of calcitriol therapy.
Conclusion: Twice-weekly oral calcitriol has a modest antiproteinuric effect in patients with IgA nephropathy and persistent proteinuria despite angiotensin-converting enzyme-inhibitor or angiotensin receptor blocker therapy. Additional studies are needed to confirm the renal protecting effect of calcitriol in patients with chronic proteinuric kidney diseases.
Trial registration: ClinicalTrials.gov NCT00319761.