Potential application of Klotho as a prognostic biomarker for patients with diabetic kidney disease: a meta-analysis of clinical studies

Background: Diabetic kidney disease (DKD) is a serious diabetic complication and the performance of serum Klotho in DKD’s prognostic evaluation is controversial. Objective: To assess the association of serum Klotho with adverse kidney and non-kidney clinical outcomes in patients with DKD. Design: Clinical studies regarding the relationship of serum Klotho with DKD were included. Study quality was assessed using the Newcastle–Ottawa scale. Subgroup and sensitive analyses were performed to search for the source of heterogeneity. Data sources and methods: We comprehensively searched PubMed, Embase, Web of Science, and Cochrane library databases up to 27 September 2022. The associations of Klotho with albuminuria, such as the urinary albumin creatinine ratio (UACR), kidney outcomes such as persistent albuminuria, estimated glomerular filtration rate decline, and non-kidney outcomes such as diabetic retinopathy, cardiovascular morbidity, and mortality, were evaluated. The indicators, such as the correlation coefficient ( r), odds ratio (OR), relative risk, and hazard ratio, were retrieved or calculated from the eligible studies. Results: In all, 17 studies involving 5682 participants fulfilled the inclusion criteria and were included in this meta-analysis. There was no significant association of serum Klotho with UACR in DKD patients [summary r, −0.28 (−0.55, 0.04)] with high heterogeneity. By contrast, a strong association was observed regarding serum Klotho with kidney outcomes [pooled OR, 1.60 (1.15, 2.23)], non-kidney outcomes [pooled OR, 2.78 (2.11, 3.66)], or combined kidney and non-kidney outcomes [pooled OR, 1.96 (1.45, 2.65)] with moderate heterogeneity. Subgroup analysis indicated that age, study design, and the estimated glomerular filtration rate may be the sources of heterogeneity. Conclusion: A decreased serum Klotho level is possibly associated with an increased risk of developing kidney and non-kidney clinical outcomes in DKD patients; thus, Klotho may be a possible biomarker to predict DKD clinical outcomes. Additional studies are needed to clarify and validate Klotho’s prognostic value.