β-Klotho as novel therapeutic target in Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD): A narrative review.

Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD) represents the most frequent cause of hepatic disorder, and its progressive form defined as Metabolic Dysfunction-Associated Steatohepatitis (MASH) contributes to the development of fibrosis/cirrhosis and hepatocellular carcinoma (HCC). Today effective therapeutic strategies addressing MASH-related comorbidities, inflammation, and fibrosis are needed. The fibroblast growth factor (FGF) 19 and 21 and their fibroblast growth factor receptor/β-Klotho (KLB) complexes have recently emerged as promising druggable targets for MASLD. However, less is known regarding the causative association between KLB activity and advanced stages of liver disease. In the present narrative review, we aimed to provide an up-to-date picture of the role of the KLB co-receptor in MASLD development and progression. We performed a detailed analysis of recently published preclinical and clinical data to decipher the molecular mechanisms underlying KLB function and to correlate the presence of inherited or acquired KLB aberrancies with the predisposition towards MASLD. Moreover, we described ongoing clinical trials evaluating the therapeutic approaches targeting FGF19-21/FGFR/KLB in patients with MASLD and discussed the challenges related to their use. We furtherly described that KLB exhibits protective effects against metabolic disorders by acting in an FGF-dependent and independent manner thus triggering the hypothesis that KLB soluble forms may play a critical role in preserving liver health. Therefore, targeting KLB may provide promising strategies for treating MASLD, as supported by experimental evidence and ongoing clinical trials.