Klotho was originally proposed to have anti-aging properties in 1997, when Kuro-o et al. reported that Klotho-deficient mice exhibit a short lifespan and multiple aging-related phenotypes, such as arteriosclerosis, hypoglycemia, osteoporosis, emphysema, skin atrophy and gonadal dysplasia [6]. Here, KL is linked to pulmonary emphysema.