MO440KLOTHO AS A BIOMARKER OF SUBCLINICAL CARDIOVASCULAR DISEASE IN CHRONIC KIDNEY DISEASE: A PROOF-OF-CONCEPT STUDY*
Authors: Ferri Carla , Donate-Correa Javier , Martín-Núñez Ernesto , Pérez-Delgado Nayra , González-Luis Ainhoa , Mora-Fernández Carmen , Navarro-González Juan F 
Published: May 2021

Abstract

Background and Aims
Cardiovascular disease (CVD) is the major cause of mortality among chronic kidney disease (CKD) patients. Reductions in serum Klotho levels are related to the prevalence of CVD in CKD patients. However, it is unclear whether circulating Klotho, and its expression in peripheral blood cells (PBCs), are associated with subclinical atherosclerotic cardiovascular disease (sCVD) in these subjects. In this proof-of-concept study, we analyzed in a group of CKD patients the relationship between Klotho and two markers of sCVD: ankle-brachial index (ABI) and carotid intima-media thickness (CIMT).

Method
Gene expression in PBCs and serum levels of Klotho and inflammatory cytokines (TNF, IL6 and IL10) were measured in 103 CKD patients (stages 3-4), older than 18 years of age, and without known atherosclerotic cardiovascular disease. Biochemical data were obtained following standardized clinical methods. The presence of sCVD was defined as ABI &lt; 0.9 and/or CIMT ≥ 0.9 mm. Patients with ABI values ≥ 1.3 were excluded.

Results
Patients with sCVD presented lower serum and PBCs expression levels of Klotho (P&lt;0.001 for both). Stratified analysis showed that upper tertiles of both serum and PBCs expression levels of Klotho presented significantly higher ABI (P&lt;0.001 for both Klotho determinations) and lower CIMT (P&lt;0.001 for serum levels and P&lt;0.01 for KL expression in PBCs), which resulted in a lower prevalence of sCVD (P&lt;0.001 for both determinations of Klotho).
Correlation analysis showed that both serum and PBCs mRNA Klotho levels were positively correlated with ABI (r=0.556, P&lt;0.0001; and r=0.373, P&lt;0.0001, respectively) and inversely correlated with CIMT (r=-0.541, P&lt;0.0001; and r=-0.437, P&lt;0.0001, respectively). Among inflammatory markers, only serum IL6 levels presented significant associations with sCVD, being inversely related with ABI (r=-0.568, P&lt;0.0001) and positively associated with CIMT (r=0.558, P&lt;0.0001).
Multiple regression analysis with ABI and CIMT as dependent variables demonstrated that both Klotho variables, together with serum IL6, were positively and significantly associated with ABI (adjusted R2=0.511, P&lt;0,0001) and CIMT (adjusted R2=0.445, P&lt;0,0001) values, independently of traditional and emergent cardiovascular risk factors.
Multivariate logistic regression, using the presence/absence of sCVD as the dependent variable, showed that circulating Klotho, and its expression in PBCs constituted independent protective factors for sCVD [OR (95% CI): 0.993 (P=0.002) and 0.231 (P=0.025), respectively]. Receiver operating curve (ROC) analysis pointed to the prognostic ability for sCVD of serum Klotho (area under the curve [AUC]: 0.817, 95% CI: 0.736–0.898, P&lt;0.001) and its gene expression in PBCs (AUC: 0.742, 95% CI: 0.647–0.836, P&lt;0.001).

Conclusion
The reductions in serum soluble and PBCs expression levels of Klotho in CKD patients are independently associated with the presence of sCVD. Further research exploring whether therapeutic approaches to maintain or elevate the Klotho level could reduce the impact of CVD in CKD patients is warranted.