Addition of low-dose calcitriol to renin-angiotensin-aldosterone system (RAAS) inhibitors may further reduce proteinuria in patients with chronic kidney disease (CKD) who have vitamin D insufficiency, new study findings suggest.

In a trial, investigators randomly assigned 60 patients with stage 3 to 4 CKD with a urine protein to creatinine ratio (UPCR) greater than 1.0 g/g and serum 25-hydroxyvitamin D levels of 25 to 26 ng/mL to oral calcitriol (0.25 µg every other day) plus a stable dose of an ACE inhibitor (ACEI) or angiotensin-receptor blocker (ARB) (vitamin D group) or ACEI or ARB alone (control group).

At baseline, proteinuria did not differ significantly between groups: 2.02 vs 1.84 g/g, respectively. Over 24 weeks, however, UPCR declined significantly by 0.66 in the vitamin D group to 1.35 g/g compared with just -0.01 in the control group to 1.84 g/g, Chia-Chao Wu, PhD, of National Defense Medical Center in Taiwan, and colleagues reported in the Journal of Renal Nutrition. The team found no significant intergroup differences in blood pressure, serum calcium, or serum phosphorus, but observed a lower intact parathyroid hormone level in the vitamin D group. The low dose of calcitriol did not cause hypercalcemia over the study period.

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“Hence, vitamin D may have had a renoprotective role beyond the traditional mineral regulation in this study,” Dr Wu and colleagues wrote. Vitamin D possibly has antiproliferative, anti-inflammatory, antioxidative, and immune-modulating effects, they noted.

The investigators encouraged future large, prospective, long-term studies in CKD patients to determine whether early vitamin D therapy would be beneficial and help delay CKD progression.

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Wu C-C, Liao M-T, Hsiao P-J, et al. Antiproteinuria effect of calcitriol in patients with chronic kidney disease and vitamin D deficiency: A randomized controlled Study. J Renal Nutr. 30:200-207. doi: 10.1053/j.jrn.2019.09.001