Relationship between sarcopenia and metabolic dysfunction-associated steatotic liver disease (MASLD): A systematic review and meta-analysis

Skeletal muscle and MASLD: Mechanistic and clinical insights

Metabolic dysfunction-associated steatotic liver disease (MASLD) is intrinsically linked with widespread metabolic perturbations, including within skeletal muscle. Indeed, MASLD is associated with a range of skeletal muscle abnormalities, including insulin resistance, myosteatosis, and sarcopenia, which all converge on the liver to drive disease progression and adverse patient outcomes. This review explores the mechanistic links between skeletal muscle and MASLD, including the role of abnormal glycemic control, systemic inflammation, and disordered myokine signaling. In turn, we discuss how intrinsic liver pathology can feed back to further exacerbate poor skeletal muscle health. Given the central importance of skeletal muscle in MASLD pathogenesis, it offers clinicians an opportunity to intervene for therapeutic benefit. We, therefore, summarize the role of nutrition and physical activity on skeletal muscle mass, quality, and metabolic function and discuss the knock-on effect this has on the liver. An awareness of these treatment strategies is particularly important in the era of effective pharmacological and surgical weight loss interventions, which can be associated with the development of sarcopenia. Finally, we highlight a number of promising drug agents in the clinical trial pipeline that specifically target skeletal muscle in an attempt to improve metabolic and physical functioning.

Metabolic dysfunction-associated steatotic liver disease: A story of muscle and mass

Skeletal muscle alterations (SMA) are increasingly recognized as both contributors and consequences of metabolic dysfunction-associated steatotic liver disease (MASLD), affecting disease progression and outcomes. Sarcopenia is common in patients with MASLD, with a prevalence ranging from 20% to 40% depending on the population and diagnostic criteria used. In advanced stages, such as metabolic dysfunction-associated steatohepatitis and fibrosis, its prevalence is even higher. Sarcopenia exacerbates insulin resistance, systemic inflammation, and oxidative stress, all of which worsen MASLD. It is an independent risk factor for fibrosis progression and poor outcomes including mortality. Myosteatosis refers to the abnormal accumulation of fat within muscle tissue, leading to decreased muscle quality. Myosteatosis is prevalent (> 30%) in patients with MASLD, especially those with obesity or type 2 diabetes, although this can vary with the imaging techniques used. It reduces muscle strength and metabolic efficiency, further contributing to insulin resistance and is usually associated with advanced liver disease, cardiovascular complications, and lower levels of physical activity. Altered muscle metabolism, which includes mitochondrial dysfunction and impaired amino acid metabolism, has been reported in metabolic syndromes, including MASLD, although its actual prevalence is unknown. Altered muscle metabolism limits glucose uptake and oxidation, worsening hyperglycemia and lipotoxicity. Reduced muscle perfusion and oxygenation due to endothelial dysfunction and systemic metabolic alterations are common in MASLD associated with comorbidities, such as obesity, hypertension, and atherosclerosis. It decreases the muscle capacity for aerobic metabolism, leading to fatigue and reduced physical activity in patients with MASLD, aggravating metabolic dysfunction. Various SMA in MASLD worsen insulin resistance and hepatic fat accumulation, may accelerate progression to fibrosis and cirrhosis, and increase the risk of cardiovascular disease and mortality. Management strategies for SMA include resistance training, aerobic exercise, and nutritional support (e.g., high-protein diets, vitamin D, and omega-3 fatty acids), which are essential for mitigating skeletal muscle loss and improving outcomes. However, pharmacological agents that target the muscle and liver (such as glucagon-like peptide-1 receptor agonists) show promise but have not yet been approved for the treatment of MASLD.

Unraveling the Metabolic Pathways Between Metabolic-Associated Fatty Liver Disease (MAFLD) and Sarcopenia

Metabolic-Associated Fatty Liver Disease (MAFLD) is a public health concern that is constantly expanding, with a fast-growing prevalence, and it affects about a quarter of the world's population. This condition is a significant risk factor for cardiovascular, hepatic, and oncologic diseases, such as hypertension, hepatoma, and atherosclerosis. Sarcopenia was long considered to be an aging-related syndrome, but today, it is acknowledged to be secondarily related to chronic diseases such as metabolic syndrome, cardiovascular conditions, and liver diseases, among other comorbidities associated with insulin resistance and chronic inflammation, besides inactivity and poor nutrition. The physiopathology involving MAFLD and sarcopenia has still not been solved. Inflammation, oxidative stress, mitochondrial dysfunction, and insulin resistance seem to be some of the keys to this relationship since this hormone target is mainly the skeletal muscle. This review aimed to comprehensively discuss the main metabolic and physiological pathways involved in these conditions. MAFLD and sarcopenia are interconnected by a complex network of pathophysiological mechanisms, such as insulin resistance, skeletal muscle tissue production capacity, chronic inflammatory state, oxidative stress, and mitochondrial dysfunction, which are the main contributors to this relationship. In addition, in a clinical analysis, patients with sarcopenia and MAFLD manifest more severe hepatitis fibrosis when compared to patients with only MAFLD. These patients, with both disorders, also present clinical improvement in their MAFLD when treated for sarcopenia, reinforcing the association between them. Lifestyle changes accompanied by non-pharmacological interventions, such as dietary therapy and increased physical activity, undoubtedly improve this scenario.

Metabolic Syndrome and Liver Disease: Re-Appraisal of Screening, Diagnosis, and Treatment Through the Paradigm Shift from NAFLD to MASLD

Metabolic dysfunction-associated steatotic liver disease (MASLD), previously known as non-alcoholic fatty liver disease (NAFLD), encompasses a spectrum of liver diseases characterized by hepatic steatosis, the presence of at least one cardiometabolic risk factor, and no other apparent cause. Metabolic syndrome (MetS) is a cluster of clinical conditions associated with increased risk of cardiovascular disease, type 2 diabetes, and overall morbidity and mortality. This narrative review summarizes the changes in the management of people with MetS and NAFLD/MASLD from screening to therapeutic strategies that have occurred in the last decades. Specifically, we underline the clinical importance of considering the different impacts of simple steatosis and advanced fibrosis and provide an up-to-date overview on non-invasive diagnostic tests (i.e., imaging and serum biomarkers), which now offer acceptable accuracy and are globally more accessible. Early detection of MetS and MASLD is a top priority as it allows for timely interventions, primarily through lifestyle modification. The liver and cardiovascular benefits of a global and multidimensional approach are not negligible. Therefore, a holistic approach to both conditions, MetS and related chronic liver disease, should be applied to improve overall health and longevity.

Lean MASLD and Cardiovascular Disease: A Review

Metabolic-associated steatotic liver disease (MASLD), formerly known as nonalcoholic fatty liver disease, is prevalent worldwide and is highly associated with cardiovascular disease (CVD). Lean MASLD is defined by hepatic steatosis and cardiometabolic risk factors in individuals with a body mass index below 25 in Western populations or below 23 in Asian populations. Paradoxically, some studies indicate that lean MASLD is associated with an elevated risk of cardiovascular (CV) disease and CV mortality compared with nonlean MASLD. Lean MASLD patients exhibit distinctive metabolic, genetic, and microbiome profiles contributing to increased visceral adiposity, sarcopenia, hepatic fibrosis, systemic inflammation, and endothelial dysfunction. This review examines the epidemiology, pathophysiology, and CV outcomes associated with lean MASLD, addressing discrepancies in the literature. Furthermore, it highlights current clinical guidelines, emphasizes lifestyle modifications, and discusses emerging pharmacotherapies as potential treatment options.

Correlation of sarcopenia with progression of liver fibrosis in patients with metabolic dysfunction-associated steatotic liver disease: a study from two cohorts in China and the United States

OBJECTIVE

The objective of this study was to investigate the association between sarcopenia and liver fibrosis in patients aged 18-59 years with metabolic dysfunction-associated steatotic liver disease (MASLD) and to assess the potential of sarcopenia as a risk factor for the progression of liver fibrosis.

METHODS

The study included 821 patients with MASLD in the US cohort and 3,405 patients with MASLD in the Chinese cohort. Liver controlled attenuation parameters (CAP) and liver stiffness measurements (LSM) were assessed by vibration-controlled transient elastography (VCTE) to evaluate the extent of hepatic steatosis and fibrosis. Sarcopenia was assessed by measuring appendicular skeletal muscle mass (ASM) and calculating ASMI. To analyze the relationship between sarcopenia, ASMI, and liver fibrosis, logistic regression models, multivariate-adjusted models, and restricted cubic spline (RCS) models were employed, with stratification and interaction analyses.

RESULTS

The results demonstrated that patients with sarcopenia exhibited a markedly elevated risk of significant liver fibrosis, advanced liver fibrosis, and cirrhosis compared to those without sarcopenia in both cohorts. After adjusting for confounding variables, sarcopenia was identified as an independent risk factor for the progression of liver fibrosis in patients with MASLD. A significant negative correlation was observed between ASMI and the severity of liver fibrosis, with a progressive reduction in the risk of liver fibrosis associated with increasing ASMI. Additionally, a non-linear feature was evident in some liver fibrosis indicators. Subgroup analysis further corroborated the finding that the harmful effect of sarcopenia on liver fibrosis was consistent across all identified subgroups.

CONCLUSION

Sarcopenia may be associated with the progression of liver fibrosis in patients with MASLD. Monitoring ASMI may assist in identifying individuals at an elevated risk of liver fibrosis in MASLD patients.