Free deoxycholic acid exacerbates vascular calcification in chronic kidney disease through ER stress-mediated ATF4 activation

Background: Our metabolome approach found that levels of circulating free deoxycholic acid (DCA) is associated with the severity of vascular calcification in patients with chronic kidney disease (CKD). However, it is not known whether DCA directly causes vascular calcification in CKD. Method: Using various chemicals and animal and cell culture models, we investigated whether the modulation of DCA levels influences vascular calcification in CKD. Results: CKD increased levels of DCA in mice and humans by decreasing urinary DCA excretion. Treatment of cultured VSMCs with DCA but no other bile acids induced vascular calcification and osteogenic differentiation through endoplasmic reticulum (ER) stress-mediated ATF4 activation. Treatment of mice with FXR-specific agonists selectively reduced levels of circulating cholic acid (CA)-derived BAs such as DCA, protecting from CKD-dependent medial calcification and atherosclerotic calcification. Reciprocal Farnesoid X receptor (FXR) deficiency and DCA treatment induced vascular calcification by increasing levels of circulating DCA and activating the ER stress response. Conclusions: This study demonstrates that DCA plays a causative role in regulating CKD- dependent vascular diseases through ER stress-mediated ATF4 activation.