KL and early-onset autosomal dominant Alzheimer disease: As an anti-aging protein, Klotho expression decreases with age, and its underexpression has been reported in many aging-related diseases such as Alzheimer’s disease, kidney disease, chronic obstructive pulmonary disease (COPD), certain cancers, cardiovascular and cerebrovascular diseases, as well as diabetes and its complications (Duce et al., 2008; Kuro-o 2012; Semba et al., 2014; Akasaka-Manya et al., 2016; Zhou et al., 2018; Lim et al., 2019).