The association between klotho and kidney and cardiovascular outcomes: a comprehensive systematic review and meta-analysis

Background Chronic kidney disease (CKD) and end-stage renal disease (ESKD) are significant global health challenges associated with progressive kidney dysfunction and numerous complications, including cardiovascular disease and mortality. This study aims to explore the potential association between plasma klotho levels and various prognostic outcomes in CKD and ESKD, including all-cause mortality, cardiovascular events, metabolic syndrome development and adverse renal events necessitating renal replacement therapies. Methods A literature search was conducted through 3 June 2024 using the electronic databases Cochrane Library, Ovid MEDLINE, CINAHL, Web of Science, SCOPUS and PubMed. This systematic review adheres to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Results Fourteen studies were included. For all-cause mortality, comparing CKD patients with low versus high klotho levels showed a significant association {odds ratio [OR] 1.81 [95% confidence interval (CI) 1.34-2.44], P = .0001}, with substantial heterogeneity (I-2 = 69%). Excluding one study reduced heterogeneity (I-2 = 43%) while maintaining significance [OR 1.97 (95% CI 1.45-2.66), P < .0001]. Cardiovascular mortality was higher in patients with low klotho levels [OR 2.11 (95% CI 1.61-2.76), P < .00001], with low heterogeneity (I-2 = 25%). Excluding one study eliminated heterogeneity (I-2 = 0%) while maintaining significance [OR 2.39 (95% CI 1.83-3.12), P < .00001]. Composite cardiovascular events did not differ significantly between low and high klotho groups [OR 1.51 (95% CI 0.82-2.77), P = .18], but with high heterogeneity (I-2 = 72%). Patients with low klotho levels had a higher risk of adverse renal events [OR 2.36 (95% CI 1.37-4.08), P = .002], with moderate heterogeneity (I-2 = 61%). Sensitivity analysis reduced heterogeneity (I-2 = 0%) while maintaining significance [OR 3.08 (95% CI 1.96-4.85), P < .00001]. Specifically, for ESKD or kidney replacement therapy risk, low klotho levels were associated with an increased risk [OR 2.30 (95% CI 1.26-4.21), P = .007]. Similarly, CKD progression risk was higher in patients with lower klotho levels [OR 2.48 (95% CI 1.45-4.23), P = .0009]. Conclusion Lower serum klotho levels serve as a significant predictor of adverse outcomes, including increased risks of all-cause mortality, cardiovascular mortality and progression to end-stage kidney disease among CKD patients.