Cardiac effect of vitamin D receptor modulators in uremic rats

Vitamin D receptor (VDR) modulators (VDRMs) are commonly used to control secondary hyperparathyroidism (SHPT) associated with chronic kidney disease, and are associated with beneficial outcomes in cardiovascular disease. In this study, we compared the cardiac effect of VS-105, a novel VDRM, with that of paricalcitol in 5/6 nephrectomized uremic rats. Male Sprague-Dawley rats were 5/6 nephrectomized, fed a standard diet for 4 weeks to establish uremia, and then treated (intraperitoneally, 3 times/week) with vehicle (propylene glycol), paricalcitol (0.025 and 0.15μg/kg), or VS-105 (0.05 and 0.3μg/kg) for 4 weeks. In uremic rats, neither VDRM (low and high doses) altered serum creatinine and phosphorus levels. Serum calcium was significantly higher with high dose paricalcitol compared to sham rats. PTH levels were significantly decreased with low dose paricalcitol and VS-105, and were further reduced in the high dose groups. Interestingly, serum FGF23 was significantly higher with high dose paricalcitol compared to sham rats, whereas VS-105 had no significant effect on FGF23 levels. Left ventricle (LV) weight and LV mass index determined by echocardiography were significantly suppressed in both high dose VDRM groups. This suppression was more evident with VS-105. Western blotting showed significant decreases in a fibrosis marker TGF-β1 in both high dose VDRM groups (vs. vehicle) and Masson trichrome staining showed significant decreases in cardiac fibrosis in these groups. These results suggest that VS-105 is less hypercalcemic than paricalcitol and has favorable effects on SHPT and cardiac parameters that are similar to those of paricalcitol in uremic rats. The cardioprotective effect is a noteworthy characteristic of VS-105.