Abstract
The Klotho gene is recognized for its anti-aging properties. Its downregulation leads to aging-like phenotypes, whereas overexpression can extend lifespan. Klotho protein exists in three forms: α-klotho, β-klotho and γ-klotho. The α-klotho has two isoforms: a membrane-bound form, primarily in the kidney and brain, and a secreted klotho protein present in blood, urine, and cerebrospinal fluid. Klotho functions as a co-receptor for fibroblast growth factor-23 (FGF23), regulating phosphate metabolism. The membrane-bound form controls various ion channels and receptors, while the secreted form regulates endocrine FGFs, including FGF19 and FGF21. The interaction between β-klotho and FGF21 in muscle is critical in the development of sarcopenic obesity. This systematic review, registered in PROSPERO and conducted following PRISMA guidelines, evaluates klotho levels in individuals with obesity or sarcopenic obesity. The study includes overweight, obese, and sarcopenic obese adults compared to those with a normal body mass index. After reviewing 713 articles, 20 studies were selected, including observational, cross-sectional, cohort studies, and clinical trials. Significant associations between klotho levels and obesity, metabolic syndrome (MS), and cardiovascular risk were observed. Exercise and dietary interventions positively influenced klotho levels, which were linked to improved muscle strength and slower decline. Klotho is a potential biomarker for obesity, MS, and sarcopenic obesity. Further research is needed to explore its mechanisms and therapeutic potential.