Verification of the Nutritional and Dietary Factors Associated with Skeletal Muscle Index in Japanese Patients with Nonalcoholic Fatty Liver Disease

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.

Sarcopenia as a Risk Factor for Mortality in NAFLD: How Should We Diagnose It?

OBJECTIVES

Sarcopenia increases the risk of nonalcoholic steatohepatitis (NASH) and cirrhosis in patients with nonalcoholic fatty liver disease (NAFLD). Subsequently, poorly managed NAFLD can result in adverse health outcomes. Lifestyle interventions are effective for both NAFLD and sarcopenia; however, diagnosis of sarcopenia in this population is not well defined. This review aimed to examine current methods to diagnose sarcopenia in NAFLD patients.

METHODS

MEDLINE, EMBASE, and CINAHL databases were searched for articles published until July 2023 using the terms "Non-alcoholic fatty liver disease," "NAFLD," "fatty liver," "sarcopenia," and "myoatrophy." Studies were excluded if they included pediatric populations, did not diagnose both sarcopenia and NAFLD, or included patients with alternate causes of liver disease.

RESULTS

Twenty studies, predominantly from Asian countries (14 [70.0%]), involving 68 848 participants (45.5% females) were included. In 15 studies, most participants had a BMI > 25 kg/m2. Heterogeneity in the tools used to diagnose NAFLD was identified, with abdominal ultrasound being the most commonly used. European, Asian, and Australasian Sarcopenia Working Groups had differing diagnostic definitions of sarcopenia. Of the three potential diagnostic elements of sarcopenia (muscle mass, strength, function), all studies measured muscle mass, commonly through bioelectrical impedance analysis (12 [60.0%]). Seven studies (35.0%) measured muscle strength, with the majority (n = 6) utilizing hand grip strength. Four (20.0%) measured muscle function, through gait speed or a timed up-and-go test.

CONCLUSIONS

The lack of standardization in sarcopenia diagnosis for NAFLD patients is concerning. A consistent definition is necessary to prevent this comorbidity from being overlooked, improve care, and outcomes.

Sarcobesity: New paradigms for healthy aging related to taurine supplementation, gut microbiota and exercise

Enigmatic sarcopenic obesity is still a challenge for science and adds to the global public health burden. The progressive accumulation of body fat combined with a dysfunctional skeletal muscle structure and composition, oxidative stress, mitochondrial dysfunction, and anabolic resistance, among other aggravating factors, together represent the seriousness and complexity of treating the metabolic disorder of sarcobesity in aging. For this reason, further studies are needed that encourage the support of therapeutic management. It is along these lines that we direct the reader to therapeutic approaches that demonstrate important, but still obscure, outcomes in the physiological conditions of sarcobesity, such as the role of taurine in modulating inflammatory and antioxidant mechanisms in muscle and adipose tissue, as well as the management of gut microbiota, able to systemically re-establish the structure and function of the gut-muscle axis, in addition to the merits of physical exercise as an instrument to improve muscular health and lifestyle quality.

The Roles of Non-Pharmacologic and Emerging Pharmacologic Management of Non-alcoholic Fatty Liver Disease and Sarcopenia: A Narrative Review

Non-alcoholic fatty liver disease (NAFLD) is one of the most prevalent causes of chronic liver disease worldwide which is often seen in patients with metabolic abnormalities such as those with obesity and insulin resistance. On the other hand, sarcopenia is a generalized and progressive skeletal muscle disorder characterized by low muscle strength, low muscle quality, low physical performance, or a combination of the three. Both disease entities share several underlying risk factors and pathophysiologic mechanisms. These include: (1) cardiometabolic overlaps such as insulin resistance, chronic systemic inflammation, decreased vitamin D levels, sex hormone modifications; (2) muscle-related factors such as those mitigated by myostatin signaling, and myokines (i.e., irisin); and (3) liver-dysfunction related factors such as those associated with growth hormone/insulin-like growth factor 1 Axis, hepatokines (i.e., selenoprotein P and leukocyte cell-derived chemotaxin-2), fibroblast growth factors 21 and 19 (FGF21 and FGF19), and hyperammonemia. This narrative review will examine the pathophysiologic overlaps that can explain the links between NAFLD and sarcopenia. Furthermore, this review will explore the emerging roles of nonpharmacologic (e.g., weight reduction, diet, alcohol, and smoking cessation, and physical activity) and pharmacologic management (e.g., roles of β-hydroxy-β-methylbutyrate, branched-chain amino acid supplements, and testosterone therapy) to improve care, intervention sustainability, and acceptability for patients with sarcopenia-associated NAFLD.

Epigenetic Regulation in Lean Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD), the most prominent cause of chronic liver disease worldwide, is a rapidly growing epidemic. It consists of a wide range of liver diseases, from steatosis to nonalcoholic steatohepatitis, and predisposes patients to liver fibrosis, cirrhosis, and even hepatocellular carcinoma. NAFLD is strongly correlated with obesity; however, it has been extensively reported among lean/nonobese individuals in recent years. Although lean patients demonstrate a lower prevalence of diabetes mellitus, central obesity, dyslipidemia, hypertension, and metabolic syndrome, a percentage of these patients may develop steatohepatitis, advanced liver fibrosis, and cardiovascular disease, and have increased all-cause mortality. The pathophysiological mechanisms of lean NAFLD remain vague. Studies have reported that lean NAFLD demonstrates a close association with environmental factors, genetic predisposition, and epigenetic modifications. In this review, we aim to discuss and summarize the epigenetic mechanisms involved in lean NAFLD and to introduce the interaction between epigenetic patterns and genetic or non genetic factors. Several epigenetic mechanisms have been implicated in the regulation of lean NAFLD. These include DNA methylation, histone modifications, and noncoding-RNA-mediated gene regulation. Epigenetics is an area of special interest in the setting of lean NAFLD as it could provide new insights into the therapeutic options and noninvasive biomarkers that target this under-recognized and challenging disorder.

Recent advances in lean NAFLD

As the predominant type of chronic liver disease, the growing prevalence of nonalcoholic fatty liver disease (NAFLD) has become a concern worldwide. Although obesity plays the most pivotal role in NAFLD, approximately 10-20% of individuals with NAFLD who are not overweight or obese (BMI < 25 kg/m2, or BMI < 23 kg/m2 in Asians) have "lean NAFLD." Lean individuals with NAFLD have a lower prevalence of diabetes, hypertension, hypertriglyceridemia, central obesity, and metabolic syndrome than nonlean individuals with NAFLD, but higher fibrosis scores and rates of cardiovascular morbidity and all-cause mortality in advanced stages. The pathophysiological mechanisms of lean NAFLD remain poorly understood. Studies have shown that lean NAFLD is more correlated with factors such as environmental, genetic susceptibility, and epigenetic regulation. This review will examine the way in which the research progress and characteristic of lean NAFLD, and explore the function of epigenetic modification to provide the basis for the clinical treatment and diagnosis of lean NAFLD.

Sarcopenic obesity in liver disease: Handling both sides of the penny

Skeletal muscle and fat tissue show distinct pathophysiological roles and pivotal functions. The culmination of muscle wasting and fat accumulation represents an opposite terminal of each state. Specifically, this situation has been designated as sarcopenic obesity. However, sarcopenic obesity still lacks a unanimous definition, diagnostic criteria, and generalized modalities for assessment in the context of versatile liver diseases. Moreover, the underpinning mechanisms by which a combination of abnormal skeletal muscle and fat tissue leads to the progression of liver disease and impairs health‐related consequences are still elusive. Additionally, the interplay between skeletal muscle and fat, and the driving factors that shift different body compositions are not well understood. Therefore, in this review, we discuss skeletal muscle and fat components, with the purpose of conceptualization, as well as interpret their roles in liver diseases. We focus on the definitions, diagnostic criteria, and currently available measurements for sarcopenic obesity in the literature. We comprehensively discuss recent data and evidence regarding the potential role of sarcopenic obesity in the development and progression of numerous liver diseases and associated conditions, including nonalcoholic fatty liver disease, chronic viral hepatitis, cirrhosis, and liver transplantation. Furthermore, explicit information related to the pathogenesis of sarcopenic obesity from basic research is also provided in this narrative review. Finally, we discuss, from the clinical perspective of view, how to manage sarcopenic obesity using nutritional, physical, and pharmacological methods.

Management of non-alcoholic fatty liver disease in patients with sarcopenia

INTRODUCTION

Sarcopenia usually occurs with aging, sedentary lifestyle, unhealthy dietary habits, and chronic disorders pathophysiologically and bi-directionally linked to obesity and nonalcoholic fatty liver disease (NAFLD). Because of the global increase in aging and obesity populations, patients with concomitant sarcopenia and NAFLD are common, accompanied by various disorders relevant to obesity and sarcopenia, with across-the-board impact on socio-economic and public health life worldwide. Therefore, developing effective and practical management of these patients has become a pressing clinical issue.

AREAS COVERED

The authors searched literature from PubMed and Ovid MEDLINE up until Feb 2020. Emerging data on the management of sarcopenia and nonalcoholic fatty liver disease were examined and discussed.

EXPERT OPINION

Although NAFLD in patients with sarcopenia has become a critical problem worldwide, we still don't know much about the management of such patients. Based on theoretical speculations, we can recommend lifestyle intervention, including diet control with adequate protein intake, exercise intervention, and weight reduction as the mainstay of management at the first stage. More studies are needed in the future to identify the most suitable treatment and solve this important problem.

Current Trends of Essential Trace Elements in Patients with Chronic Liver Diseases

Essential trace elements play crucial roles in the maintenance of health, since they are involved in many metabolic pathways. A deficiency or an excess of some trace elements, including zinc, selenium, iron, and copper, frequently causes these metabolic disorders such as impaired glucose tolerance and dyslipidemia. The liver largely regulates most of the metabolism of trace elements, and accordingly, an impairment of liver functions can result in numerous metabolic disorders. The administration or depletion of these trace elements can improve such metabolic disorders and liver dysfunction. Recent advances in molecular biological techniques have helped to elucidate the putative mechanisms by which liver disorders evoke metabolic abnormalities that are due to deficiencies or excesses of these trace elements. A genome-wide association study revealed that a genetic polymorphism affected the metabolism of a specific trace element. Gut dysbiosis was also responsible for impairment of the metabolism of a trace element. This review focuses on the current trends of four trace elements in chronic liver diseases, including chronic hepatitis, liver cirrhosis, nonalcoholic fatty liver disease, and autoimmune liver diseases. The novel mechanisms by which the trace elements participated in the pathogenesis of the chronic liver diseases are also mentioned.