Reduced Circulating α‐Klotho Levels Are Associated With Elevated Mortality and Arterial Calcifications of Aorta and Iliac Arteries

Background α‐Klotho is a multifunctional protein implicated in vascular aging. Declining Klotho levels are associated with arterial stiffness, endothelial dysfunction, and vascular calcification. We investigated the associations between circulating klotho, aortoiliac calcification, endothelial progenitor cells, and 10‐year survival. Methods In this retrospective cohort, blinded clinicians scored calcification on computed tomography (0–10 scale: aorta 6 points, iliac 4 points). Plasma klotho was measured by ELISA; endothelial progenitor cell subsets were quantified via flow cytometry. Mortality data were obtained from the Minnesota Death Registry. Results This study included 148 participants (mean age 72.4±9.6 years; 41% female). Median calcification score was 3 (interquartile range, 1–5). Patients with low calcification had higher Klotho levels (669 [567–841] versus 556 [457–678] pg/mL; P <0.01), with Klotho inversely correlated with calcification (r=−0.315, P <0.01). Stratified by calcification location and severity, the highest Klotho levels were seen in patients without aortic or iliac calcification ( P =0.015). Over 10 years, low Klotho was independently associated with higher mortality (hazard ratio [HR], 3.056 [95% CI 1.288–7.878]; P =0.014). Klotho inversely correlated with mature osteocalcin‐positive EPCs; B=−0.16 (95% CI, −0.29 to −0.02; P =0.027). Immunohistochemistry and immunofluorescence confirmed endothelial Klotho expression in internal mammary artery. Conclusions Lower circulating Klotho levels are associated with increased aortoiliac calcification and higher 10‐year mortality, supporting a role for Klotho in vascular aging.