Frailty in metabolic syndrome, focusing on nonalcoholic fatty liver disease

In recent years, frailty has been increasingly recognized among researchers of distinct medical specialties worldwide. Frailty comprises a complex of multisystemic physiological decline, reduced physiologic reserve, and vulnerability to stressors. Frail people tend to have a shorter lifespan and greater disability, morbidity and mortality. In the field of hepatology, frailty is identified in nearly 50% of patients who have cirrhosis of any cause. The most predominant cause of chronic liver disease is nonalcoholic fatty liver disease (NAFLD), considered as the hepatic manifestation of the metabolic syndrome (MetS). Although it is viewed as a benign disease, it may progress to nonalcoholic steatohepatitis (NASH), characterized by the additional emergence of inflammation and hepatocyte ballooning, with or without fibrosis. During the progression of NAFLD to NASH and liver cirrhosis, NAFLD patients present sarcopenia along with lower skeletal muscle strength and function. Moreover, aging and the increased prevalence of comorbidities further exacerbate their physical performance. The aforementioned features are strongly associated with the frailty phenotype, implying that the latter could be associated with both MetS and NAFLD. Although it is a relatively new topic of research interest, in this review we aim to provide a synopsis of the current literature dealing with the interplay between frailty and MetS, and to shed more light on the association between NAFLD and frailty. Finally, we discuss the potential pathophysiological mechanisms linking the distinct features of MetS and NAFLD with aspects of the frailty phenotype.