Hyperammonemia in cirrhosis induces transcriptional regulation of myostatin by an NF-κB-mediated mechanism. Proc Natl Acad Sci U S A. 2013;110:18162-18167. [PMID: 24145431 DOI: 10.1073/pnas.1317049110]

Integrated Multiomics Analyses of the Molecular Landscape of Sarcopenia in Alcohol-Related Liver Disease

BACKGROUND

Skeletal muscle is a major target for ethanol-induced perturbations, leading to sarcopenia in alcohol-related liver disease (ALD). The complex interactions and pathways involved in adaptive and maladaptive responses to ethanol in skeletal muscle are not well understood. Unlike hypothesis-driven experiments, an integrated multiomics-experimental validation approach provides a comprehensive view of these interactions.

METHODS

We performed multiomics analyses with experimental validation to identify novel regulatory mechanisms of sarcopenia in ALD. Studies were done in a comprehensive array of models including ethanol-treated (ET) murine and human-induced pluripotent stem cell-derived myotubes (hiPSCm), skeletal muscle from a mouse model of ALD (mALD) and human patients with alcohol-related cirrhosis and controls. We generated 13 untargeted datasets, including chromatin accessibility (assay for transposase accessible chromatin), RNA sequencing, proteomics, phosphoproteomics, acetylomics and metabolomics, and conducted integrated multiomics analyses using UpSet plots and feature extraction. Key findings were validated using immunoblots, redox measurements (NAD+/NADH ratio), imaging and senescence-associated molecular phenotype (SAMP) assays. Mechanistic studies included mitochondrial-targeted Lactobacillus brevis NADH oxidase (MitoLbNOX) to increase redox ratio and MitoTempo as a mitochondrial free radical scavenger.

RESULTS

Multiomics analyses revealed enrichment in mitochondrial oxidative function, protein synthesis and senescence pathways consistent with the known effects of hypoxia-inducible factor 1α (HIF1α) during normoxia. Across preclinical and clinical models, HIF1α targets (n = 32 genes) and signalling genes (n > 100 genes) (n = 3 ATACseq, n = 65 phosphoproteomics, n = 10 acetylomics, n = 6 C2C12 proteomics, n = 106 C2C12 RNAseq, n = 64 hiPSC RNAseq, n = 30 hiPSC proteomics, n = 3 mouse proteomics, n = 25 mouse RNAseq, n = 8 human RNAseq, n = 3 human proteomics) were increased. Stabilization of HIF1α (C2C12, 6hEtOH 0.24 ± 0.09; p = 0.043; mALD 0.32 ± 0.074; p = 0.005; data shown as mean difference ± standard error mean) was accompanied by enrichment in the early transient and late change clusters, -log(p-value) = 1.5-3.8, of the HIF1α signalling pathway. Redox ratio was reduced in ET myotubes (C2C12: 15512 ± 872.1, p < 0.001) and mALD muscle, with decreased expression of electron transport chain components (CI-V, p < 0.05) and Sirt3 (C2C12: 0.067 ± 0.023, p = 0.025; mALD: 0.41 ± 0.12, p = 0.013). Acetylation of mitochondrial proteins was increased in both models (C2C12: 107364 ± 4558, p = 0.03; mALD: 40036 ± 18 987, p = 0.049). Ethanol-induced SAMP was observed across models (P16: C2C12: 0.2845 ± 0.1145, p < 0.05; hiPSCm: 0.2591, p = 0.041). MitoLbNOX treatment reversed redox imbalance, HIF1α stabilization, global acetylation and myostatin expression (p < 0.05).

CONCLUSIONS

An integrated multiomics approach, combined with experimental validation, identifies HIF1α stabilization and accelerated post-mitotic senescence as novel mechanisms of sarcopenia in ALD. These findings show the complex molecular interactions leading to mitochondrial dysfunction and progressive sarcopenia in ALD.

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.

Changes in serum myostatin levels among patients with type C liver cirrhosis treated with direct-acting antivirals

AIM

To clarify whether direct-acting antiviral treatment improves serum myostatin levels of patients with cirrhosis caused by hepatitis C virus.

METHODS

A total of 99 patients with type C liver cirrhosis were administered direct-acting antiviral treatment. The median age was 73 years, and 58 patients were women. We measured the levels of serum myostatin, decorin, follistatin, and insulin-like growth factor-1, as well as the skeletal muscle mass index at baseline. We measured the sustained virological response at 48 weeks.

RESULTS

Serum myostatin levels of the Child-Pugh class B or C group (n = 30) were significantly higher than those of the Child-Pugh class A group (n = 69) at baseline. The multivariate analysis indicated that the total bilirubin level and Mac-2 binding protein glycosylation isomer level were independent factors associated with serum myostatin levels. Serum myostatin levels significantly decreased, whereas the skeletal muscle mass index and insulin-like growth factor-1 level were significantly increased at 48 weeks.

CONCLUSIONS

Direct-acting antiviral treatment decreased serum myostatin levels and may improve sarcopenia in patients with cirrhosis.

Rifaximin-α use is associated with improved muscle mass in patients with cirrhosis

BACKGROUND

Sarcopaenia is associated with a two-fold higher mortality rate in patients with cirrhosis independent of liver disease severity. Few treatments for cirrhosis related sarcopaenia exist beyond optimal nutritional management.

AIM

To assess if rifaximin-α, a minimally absorbed antimicrobial used to manage hepatic encephalopathy (HE), may improve sarcopaenia in cirrhosis through its ammonia lowering and anti-inflammatory properties.

METHODS

This single-centre retrospective cohort study of patients with prior HE compared patients treated with lactulose alone to those on combination therapy with rifaximin-α. The primary outcome was a change in skeletal muscle area (SMA) as measured by computed tomography over two time points. Secondary outcomes included episodes of spontaneous bacterial peritonitis, variceal bleeding, and gastrointestinal Clostridium difficile infection.

RESULTS

Of the 142 patients included, 63 were on rifaximin-α [35% female, median age 57 (51, 62)], and 79 were on lactulose without rifaximin-α [20% female, median age 55 (51, 60)]. Univariate analysis for SMA found that male sex (P < 0.001), hepatocellular carcinoma presence (P = 0.024), and greater baseline body mass index (P = 0.001) were associated with improvement of SMA. Multivariate analysis that adjusted for baseline SMA was performed and found only use of rifaximin-α (P = 0.029) to be associated with improvement of SMA.

CONCLUSION

This study demonstrates a significant independent association between rifaximin-α therapy and muscle mass in patients with cirrhosis and HE. Prospective studies of rifaximin-α therapy examining its impact on sarcopenia are required to assess its potential therapeutic role in this cohort.

Aging: A struggle for beneficial to overcome negative factors made by muscle and bone

Musculoskeletal health is strongly influenced by regulatory interactions of bone and muscle. Recent discoveries have identified a number of key mechanisms through which soluble factors released during exercise by bone exert positive effects on muscle and by muscle on bone. Although exercise can delay the negative effects of aging, these beneficial effects are diminished with aging. The limited response of aged muscle and bone tissue to exercise are accompanied by a failure in bone and muscle communication. Here, we propose that exercise induced beneficial factors must battle changes in circulating endocrine and inflammatory factors that occur with aging. Furthermore, sedentary behavior results in the release of negative factors impacting the ability of bone and muscle to respond to physical activity especially with aging. In this review we report on exercise responsive factors and evidence of modification occurring with aging.

Post-TIPS Overt Hepatic Encephalopathy Increases Long-Term but Not Short-Term Mortality in Cirrhotic Patients With Variceal Bleeding: A Large-Scale, Multicenter Real-World Study

BACKGROUND

Transjugular intrahepatic portosystemic shunt (TIPS) is an established procedure for managing portal hypertension in cirrhotic patients, but the impact of post-TIPS overt hepatic encephalopathy (OHE) on survival remains controversial. While its effect on short-term survival is well-documented, its long-term implications remain unclear.

AIMS

This study aims to investigate the long-term impact of post-TIPS OHE on mortality in cirrhotic patients for variceal bleeding, focusing on the timing and predictive value of OHE beyond the first year post-TIPS.

METHODS

A multicenter, retrospective cohort study was conducted involving 3262 cirrhotic patients who underwent TIPS for variceal bleeding at seven Chinese tertiary centers between January 2010 and June 2020. Clinical data, including demographics, procedure details, post-TIPS complications and survival outcomes, were collected. The primary endpoints were all-cause mortality and OHE, with follow-up until death, liver transplantation or 60 months. Propensity score matching minimised confounding effects, and multivariate Fine-Grey competing risk models identified independent mortality predictors.

RESULTS

During a median follow-up of 1077 days, 33.2% developed post-TIPS OHE, associated with higher MELD and Child-Pugh scores. Among these, 19.3% died, with a median time from OHE onset to death of 947 days. Post-TIPS OHE was not linked to early survival (within 12 months) but emerged as an independent predictor of long-term mortality beyond 24 months, consistent across various clinical scenarios.

CONCLUSION

Post-TIPS OHE does not affect short-term survival but significantly increases long-term mortality risk. These findings highlight the need for continuous monitoring and tailored interventions to improve long-term outcomes in post-TIPS patients.

Nutritional Approach to Diabetic Sarcopenia: A Comprehensive Review

PURPOSE OF THE REVIEW

The aim of this review is to discuss and evaluate diabetic sarcopenia (DS) and its relationship with nutrition by discussing the mechanisms of diabetic sarcopenia in detail and comprehensively reviewing the literature.

RECENT FINDINGS

Type 2 diabetes (T2DM) affects approximately 25% of people aged 50 years and over and indicates a significant the cost of health for the elderly. Nutrition is an important part of these treatment approaches, and in this review, the literature was comprehensively reviewed, focusing on understanding the mechanisms of DS and discussing its relationship with nutrition. A comprehensive search was conducted on Web of Science, Google Scholar, Scopus, Science Direct, and PubMed from inception up to July 2024. The aim of nutritional treatment for DS is to improve muscle mass, muscle strength and physical performance while improving diabetes-related metabolic risk and glucose levels. In this context, it is important to determine energy intake in individuals with DS according to calorie intake exceeding 30 kcal/kg. For these individuals, a protein intake of at least 1-1.2 g/kg/day is recommended, with an emphasis on the number and timing of meals and a nutritional pattern rich in branched chain amino acids (BCAA). In addition, it is important to adopt a diet rich in antioxidants and to choose diet patterns that contain sufficient levels of macro and micronutrients. The Mediterranean diet model can be a good diet option for individuals with DS. Comprehensive studies in this field are needed so that clinicians can make specific dietary recommendations for DS.

Hyperammonemia induces programmed liver cell death

Hyperammonemia is common in liver cirrhosis and causally associated with hepatic encephalopathy development. Little is known about its hepatotoxic effects, which we aimed to characterize in this study. In a mouse model of chronic hyperammonemia without preexisting liver disease, we observed development of liver fibrogenesis and necroptotic cell death. Hyperammonemia also induced dysregulation of its main metabolic pathway, the urea cycle, as reflected by down-regulation of urea cycle enzyme protein expression and accumulation of its metabolites. Inhibition of receptor-interacting serine/threonine-protein kinase 1 (RIPK1) and its upstream inducer Toll-like receptor 4 (TLR4) protected against liver injury and further hyperammonemia. In clinically relevant rodent models of hyperammonemia (genetic ornithine transcarbamylase deficiency and bile duct ligation-induced cirrhosis), TLR4 inhibition reduced circulating ammonia. In conclusion, hyperammonemia induces liver fibrogenesis and RIPK1-mediated cell death, which is associated with urea cycle dysfunction. Inhibition of RIPK1 and TLR4 protects against hyperammonemia-induced liver injury and are potential therapeutic targets for hyperammonemia and chronic liver disease progression.

Amino Acid Metabolism and Immune Dysfunction in Urea Cycle Disorders: T and B Cell Perspectives

Urea cycle disorders (UCDs) are a group of genetic metabolic conditions characterized by enzyme deficiencies responsible for detoxifying ammonia. Hyperammonemia, the accumulation of intermediate metabolites, and a deficiency of essential amino acids-due to a protein-restrictive diet and the use of ammonia scavengers-can increase the risk of infections, particularly during metabolic crises. While the underlying mechanisms of immune suppression are still being fully elucidated, hyperammonemia may impair the function of immune cells, particularly T cells and macrophages, inhibiting the proliferation of T cells and cytokine production. Arginine, which is essential for T-cell activation and function, may also be limited in these patients, and its depletion can increase their vulnerability to infections. Twenty-four UCD patients and 31 healthy donors were recruited for the study. Peripheral lymphocyte subset analysis, intracellular protein and cytokine staining, and proliferation assays were performed by flow cytometry. Amino acid levels were measured using the HPLC method. The UCD patients exhibited low lymphocyte-proliferation capacity in both proximal and distal defects in response to phytohaemagglutinin (PHA) and anti-CD2, anti-CD3, and anti-CD28 (CD-mix), which was lower than healthy controls. Proximal-UCD patients exhibited a significantly higher response for IFN-γ compared to both distal-UCD patients and healthy controls. The different amino acids in the culture medium were changed significantly in the groups. This study highlights significant immune dysfunctions in UCD patients, particularly impaired T-cell proliferation and altered amino acid metabolism. Proximal UCD patients exhibited a higher IFN-γ response, indicating a potential for hyperinflammation. Despite this, infection rates did not significantly differ between proximal UCD and distal UCD patients, although distal UCD patients had higher hospitalization rates. Amino acid analysis revealed distinct metabolic disruptions, emphasizing the complex interplay between metabolism and immune function. These findings suggest that UCDs cause profound immune alterations, necessitating further research to develop targeted therapeutic strategies.

Type 2 Diabetes Mellitus Is a Risk Factor for Skeletal Muscle Loss in the Course of Dietary Treatment for Patients with Metabolic Dysfunction-associated Steatotic Liver Disease

Objective This study assessed the impact of dietary therapy and reduced body weight on the loss of skeletal muscle in patients with metabolic dysfunction-associated steatotic liver disease (MASLD). Methods This was a single-center retrospective observational study. We enrolled 129 patients with MASLD who had undergone dietary therapy at our facility. We assessed skeletal muscle mass using a bioelectrical impedance analysis at the start of dietary treatment and 12 months after the first assessment. Variables related to muscle reduction were analyzed using a logistic regression model. Results One hundred and eighteen cases were analyzed, excluding those with missing data. In the muscle reduction group, there were more subjects with body weight reduction than in the control group (68% and 40%, respectively, p=0.002), and their body mass index (BMI) was decreased (-0.7 kg/m2 and +0.3 kg/m2, respectively, p=0.0003). There was a significant correlation between the changes in the BMI and muscle mass (R=0.48, p<0.0001). We standardized muscle mass change by dividing it by weight change to analyze the severe decrease in muscle mass compared to weight change. A logistic regression analysis revealed that type 2 diabetes mellitus (T2DM) was an independent variable related to severe skeletal muscle loss (odds ratio, 2.69; 95% CI: 1.13-6.42, p=0.03). Conclusion Weight loss is associated with skeletal muscle loss during dietary treatment for MASLD. T2DM is a risk factor for severe skeletal muscle loss.

Clinical Relevancies of Sarcopenic Obesity in Patients with Metabolic Dysfunction-Associated Fatty Liver Disease (MASLD)

AIM

Sarcopenic obesity (SO) is associated with adverse outcomes in diseased patients. This study aimed to examine the prevalence and risks associated with SO, with a focus on the impact of SO on cardiovascular risk in patients with MASLD.

MATERIALS AND METHODS

In this cross-sectional study, patients with MASLD were prospectively enrolled. Through dual-energy X-ray absorptiometry (DXA) scans, their body compositions were analyzed to identify who had SO and osteopenia/osteoporosis. The primary aim is to investigate risks associated with SO, followed by analyzing the association between SO and cardiovascular disease (CVD).

RESULTS

Two hundred and twenty-three patients with MASLD were enrolled. The prevalence of SO was 47.1%, respectively. Patients coexisted with MASLD and SO had increased visceral adipose tissue (VAT), higher fatty liver index (FLI) and fibrosis 4 (FIB-4) score. Regression analysis revealed higher FLI and FIB-4 score, as well as history of hypertension, were risks associated with SO. The 10-year atherosclerotic cardiovascular disease (ASCVD) risk score was higher in patients coexisted with MASLD and SO compared to those without (10.1% vs. 7.3%, p = 0.006). Regression analysis showed that increased VAT and FIB-4 score were associated with raised risk of ASCVD.

CONCLUSION

Prevalence of SO in MASLD patients is considerable. The presence of SO also linked to higher risk of ASCVD. Therefore, the recognition of SO in patients with MASLD is important in clinical care.

Relationship between Sarcopenia and minimal hepatic encephalopathy in patients with cirrhosis: a prospective observational study

BACKGROUND

Sarcopenia, characterized by loss of muscle mass and function, has gained importance in the evaluation of cirrhotic patients. Evidence suggests its role in adverse clinical outcomes, including minimal hepatic encephalopathy (MHE). This study aimed to investigate the association between sarcopenia and MHE in patients with cirrhosis.

METHODS

We prospectively enrolled outpatients with cirrhosis to assess sarcopenia using the 2019 criteria from the Asian Working Group for Sarcopenia. MHE was diagnosed through the Psychometric Hepatic Encephalopathy Score.

RESULTS

Of the 210 cirrhotic patients (57.1% male, mean age 62.7 ± 9.6 years), 54 (25.7%) had sarcopenia, with 26 (12.3%) classified as severe. Thirty-seven patients (17.6%) were diagnosed with MHE. Sarcopenia prevalence was significantly higher in patients with MHE compared to those without MHE (45.9% vs. 21.4%). MHE was significantly associated with age, education level, Mini-Mental State Examination score, and a history of hepatic decompensation. No significant associations were found regarding gender, body mass index, comorbidities, sleep quality, and the etiology of cirrhosis. Multivariable logistic regression showed that MHE was significantly associated with age (adjusted odds ratio [aOR] 1.08, 95% CI 1.02-1.13), sarcopenia (aOR 3.29, 95% CI 1.44-7.50), history of overt hepatic encephalopathy (aOR 7.40, 95% CI 1.20-45.56), and variceal bleeding (aOR 3.13, 95% CI 1.38-7.10). Severe sarcopenia was also independently associated with MHE (aOR 3.64, 95% CI 1.32-10.05).

CONCLUSIONS

Sarcopenia is prevalent in cirrhotic patients and is associated with an increased risk of MHE. Our findings emphasize the importance of assessing sarcopenia to potentially mitigate MHE risk in managing patients with cirrhosis.

Circulating Extracellular Vesicles in Alcoholic Liver Disease Affect Skeletal Muscle Homeostasis and Differentiation

BACKGROUND

The mechanisms underlying muscle alteration associated to alcoholic liver disease (ALD) are not fully understood and the physiopathologic mediators of the liver-muscle interplay remains elusive. We investigated the role of circulating extracellular vesicles (EVs) in ALD as potential mediators of muscle atrophy.

METHODS

We established a mouse model of sarcopenia associated to ALD, by feeding mice with an alcoholic diet for 8 weeks. We investigated the effects of hepatic and circulating EVs isolated from these mice (EtOH mice; n = 7 females) on muscle cell cultures, comparing them with EVs from mice fed with a standard diet (CD mice; n = 6 females). Additionally, we examined the impact of circulating EVs from patients with alcohol-related cirrhosis (7 males and 2 females, mean age 55.4 years) on primary human muscle cells, comparing them with EVs from age-matched healthy subjects (6 males and 3 females). We analysed the miRNA profile of the EVs to identify potential mediators of ALD-associated sarcopenia.

RESULTS

We demonstrated that circulating EVs were internalized by muscle cells and that EVs from ALD mice and cirrhotic patients caused alteration in the myogenic program. Molecular analysis revealed that serum EVs from ALD mice reduced protein synthesis in C2C12 cells, decreasing levels of p-AKT/AKT (-54.6%; p < 0.05), p-mTOR/mTOR (-54.5%; p < 0.05) and p-GSK3(Ser9)/GSK3 (-30.63%). Similarly, hepatic EVs induced defects in muscle differentiation, with reduced levels of p-AKT/AKT (-39.1%; p < 0.05), p-mTOR/mTOR (-30.1%; p < 0.05) and p-GSK3(Ser9)/GSK3 (-40%). C2C12 cells treated with either serum or hepatic EtOH-EVs exhibited upregulated expression of muscle-specific atrophy markers Atrogin-1 (+61.2% and +189.5%, respectively; p < 0.05) and MuRF1 (+260.4% and +112.5%, respectively; p < 0.05), along with an increased LC3-II/-I ratio (+131.5% and +40.2%, respectively; p < 0.05), indicating enhanced autophagy. MiRNA analysis revealed that both circulating and hepatic EVs from ALD mice showed elevated expression of miR-21, miR-155, miR-223 and miR-122 (+230% and +292%, respectively; p < 0.01) suggesting their potential role in sarcopenia. Human muscle cells exposed to EVs from cirrhotic patients exhibited reduced protein synthesis and upregulated Atrogin-1 (+113%; p < 0.05) and MuRF1 (+86.3%; p < 0.05), indicating proteasome activation. Circulating EVs of alcoholic patients showed upregulation of the same miRNAs observed in EtOH mice, including the liver-specific miR-122 (+260%; p < 0.05) suggesting, also in human liver disease, a hepatic origin of circulating EVs.

CONCLUSIONS

Our study highlights the critical role of ALD-derived circulating EVs in affecting muscle homeostasis and myogenic program, suggesting potential therapeutic targets for mitigating muscle loss in ALD.

Attenuating hyperammonemia preserves protein synthesis and muscle mass via restoration of perturbed metabolic pathways in bile duct-ligated rats

Sarcopenia and hepatic encephalopathy (HE) are complications of chronic liver disease (CLD), which negatively impact clinical outcomes. Hyperammonemia is considered to be the central component in the pathogenesis of HE, however ammonia's toxic effects have also been shown to impinge on extracerebral organs including the muscle. Our aim was to investigate the effect of attenuating hyperammonemia with ornithine phenylacetate (OP) on muscle mass loss and associated molecular mechanisms in rats with CLD. Six-week bile duct-ligated (BDL) rats and Sham-operated controls were treated with OP (1 g/kg, oral) for 5 weeks. Body composition, assessed by EchoMRI, and muscle protein fractional synthesis rate were evaluated. Signalling mechanisms regulating protein homeostasis, ATP content and metabolic intermediates in the tricarboxylic acid cycle (TCA) in skeletal muscle were quantified. OP treatment attenuated hyperammonemia, prevented brain edema and improved locomotor activity in BDL rats. Increased muscle ammonia, reduction in lean body mass, decreased muscle protein synthesis rate and ATP content were restored in OP-treated versus saline-treated BDL rats. TCA cycle intermediary metabolite, α-ketoglutarate, alterations of molecular markers regulating protein homeostasis including mTOR signalling and autophagy, were also preserved in muscle of OP-treated BDL rats. OP attenuated hyperammonemia, preserved muscle protein synthesis and prevented muscle mass loss in a preclinical model of CLD through restoration of perturbed signalling responses and altered TCA intermediary metabolites. Ammonia-lowering strategies have the potential for rapid clinical translation for simultaneous neuroprotection and sarcopenia prevention in patients with CLD.

Ultrasound-Defined Sarcopenia Independently Predicts Acute Decompensation in Advanced Chronic Liver Disease

BACKGROUND

It has been shown that in patients with liver cirrhosis, sarcopenia is a predictor of acute decompensation (AD), acute-on-chronic liver failure (ACLF) and death. However, computer tomography (CT), as a suggested standard method for diagnosing sarcopenia, is resource intensive and involves radiation exposure. Therefore, in this study, we evaluate the muscle thickness of quadriceps femoris measured by ultrasound (US) as a prognostic parameter for AD and all-cause mortality in chronic liver disease.

METHODS

Sixty-three patients with chronic liver disease and signs of portal hypertension were analysed in this prospective monocentric study for the occurrence of acute decompensation such as hepatic encephalopathy, ascites, haemorrhage and liver-related death within 1 year. We assessed muscle thickness at three different heights in terms of suitability as a predictor.

RESULTS

Among all 63 patients, 15 patients experienced acute decompensation, and 9 patients died due to liver-related death. We found the upper third of the muscle, measured without applying pressure with the transducer, to be the most significant for predicting AD/ACLF [AUC 0.739 (confidence interval (CI) 0.604-0.874, p = 0.006]. A cut-off value of US-defined muscle thickness standardized per height for identifying sarcopenia was determined (1.83 cm/m). Patients with US-defined sarcopenia showed significantly higher rates of AD (38.9% vs. 3.7%, p = 0.001) and all-over 1-year mortality (27.8% vs. 3.7%, p = 0.013). The mean AD free survival time is 8.3 months (95% CI 6.6-9.9) for sarcopenic patients and 11.8 months (95% CI 11.0-12.6) for the non-sarcopenic cohorts. Corresponding CT analysis displayed similar results for AD free survival for both groups (40% AD rate in the sarcopenic group vs. 7% AD rate in the non-sarcopenic group, p = 0.001). The risk for AD was significantly higher in the sarcopenic cohort compared with those without sarcopenia in both US and CT (US: HR 16.6; p = 0.009; 95% CI 2.0-136.0; CT: HR 8.7; p = 0.017; 95% CI 1.5-51.0). CT and US displayed a moderate agreement (p = 0.006; κ = 0.379).

CONCLUSIONS

Sarcopenia classification based on US measurements is shown to be an independent predictor of AD occurrence within 1 year. This pilot study is the first to suggest that screening for sarcopenia by ultrasonography may be useful for risk assessment in patients with chronic liver disease and signs of portal hypertension.

Myostatin as a plausible biomarker for early stage of sarcopenic obesity

Since sarcopenic obesity (SO) impacts negatively on our health, early detection of SO is essential. However, prevalence of SO in an apparently healthy population has not been well examined. This study aimed to elucidate the prevalence and related factors of SO in middle-aged women, and to investigate useful diagnostic criteria for SO. Body component analyses were conducted on 432 female Osaka University employees aged 30-59 during their health checkups. Healthy (H) and SO groups were defined using cutoff values of 5.7 kg/m2 for skeletal muscle mass index and 30% for percent body fat. Serum myostatin and insulin levels were additionally measured. Among 432 participants, the prevalence of SO was 6.3%. Grip strength (P < 0.0001) was lower and triglyceride (P = 0.0004) and low-density lipoprotein cholesterol (P = 0.0105) levels, and Homeostatic Model Assessment of Insulin Resistance (P = 0.0262) were higher in the SO group than in the H group. Serum myostatin levels in the SO group were lower than in the H group (3,107 pg/mL vs. 3,957 pg/mL, P = 0.0003). Myostatin levels may be suppressed in individuals with SO without any pre-existing conditions. Our diagnostic criteria for SO could reveal the risks for metabolic-related diseases and may be useful for the early detection of SO.

Ammonia-induced stress response in liver disease progression and hepatic encephalopathy

Ammonia levels are orchestrated by a series of complex interrelated pathways in which the urea cycle has a central role. Liver dysfunction leads to an accumulation of ammonia, which is toxic and is strongly associated with disruption of potassium homeostasis, mitochondrial dysfunction, oxidative stress, inflammation, hypoxaemia and dysregulation of neurotransmission. Hyperammonaemia is a hallmark of hepatic encephalopathy and has been strongly associated with liver-related outcomes in patients with cirrhosis and liver failure. In addition to the established role of ammonia as a neurotoxin in the pathogenesis of hepatic encephalopathy, an increasing number of studies suggest that it can lead to hepatic fibrosis progression, sarcopenia, immune dysfunction and cancer. However, elevated systemic ammonia levels are uncommon in patients with metabolic dysfunction-associated steatotic liver disease. A clear causal relationship between ammonia-induced immune dysfunction and risk of infection has not yet been definitively proven. In this Review, we discuss the mechanisms by which ammonia produces its diverse deleterious effects and their clinical relevance in liver diseases, the importance of measuring ammonia levels for the diagnosis of hepatic encephalopathy, the prognosis of patients with cirrhosis and liver failure, and how our knowledge of inter-organ ammonia metabolism is leading to the development of novel therapeutic approaches.

Possibilities of treating sarcopenia in liver cirrhosis with hypoammonemic agents

Introduction. The use of hypoammonemic agents to treat sarcopenia in liver cirrhosis has the potential to positively affect muscle mass, strength and function, given the pathogenetic basis of sarcopenia in liver cirrhosis.

Aim. To compare muscle mass, strength and function, as well as capillary blood ammonia levels in patients with decompensated liver cirrhosis in two groups with and without use of L-ornithine-L-aspartate (LOLA).

Materials and methods. A prospective cohort study was conducted. The treatment group included patients with decompensated liver cirrhosis of various etiologies and hyperammonemia, who received a hypoammonemic agent (LOLA) as part of complex therapy; the comparator group included patients with liver cirrhosis, hyperammonemia and sarcopenia, who did not receive LOLA. All patients underwent measurements of muscle mass (shoulder muscle volume, skeletal muscle mass indices (SMI) measured by dual-energy X-ray absorptiometry), strength (dynamometry, chair stand test) and function (short physical performance battery).

Results. An analysis of clinical outcomes included 42 patients: 30 from the treatment group and 12 from the comparator group. In the treatment group, the proportion of patients with reduced muscle mass decreased from 76.67% to 73.33% (p = 0.012).

The average shoulder muscle volume in the treatment group was 20.86 cm, which reached 21.35 cm (p = 0.072) at 3 months of therapy. The growth in shoulder muscle values and changes in the skeletal muscle indices for the upper limbs showed an increase in muscle mass. In the treatment group, mean muscle mass values measured by handheld dynamometry (HHD) increased from 20.53 to 22.48 kg at 3 months of therapy (p = 0.011). The increase in dynamometry scores demonstrated an increase in muscle strength during LOLA therapy. The increase in balance test scores determining muscle function was reported (p < 0.001). The capillary blood ammonia levels did not change significantly in both groups.

Conclusion. The study showed a significant increase in muscle mass, strength and function in patients with liver cirrhosis and hyperammonemia, receiving LOLA as part of decompensated liver cirrhosis therapy.

Sarcopenia in cirrhosis: From pathophysiology to interventional therapy

Sarcopenia, characterized by the loss of skeletal muscle mass and function, is a significant complication in patients with cirrhosis. This condition not only exacerbates the overall morbidity and mortality associated with liver disease but also complicates patient management, increasing the risk of hospitalization, infections, and hepatic encephalopathy. Despite its clinical significance, sarcopenia in cirrhotic patients remains underdiagnosed and undertreated. This review aims to summarize current knowledge on the pathophysiology of sarcopenia in cirrhosis, including mechanisms such as altered metabolism, hormonal imbalances, and inflammation. Additionally, we explore diagnostic challenges and discuss emerging therapeutic strategies, including nutritional support, exercise, and pharmacological interventions. By highlighting the gaps in existing research and proposing directions for future studies, this review seeks to improve the management and outcomes of cirrhotic patients affected by sarcopenia.

Myokines are associated with progression, course and mortality in alcohol-associated liver disease

BACKGROUND AND AIMS

Myokines are the muscle-derived hormones orchestrating muscle and systemic health. Their role in the progression of alcohol-associated liver disease (ALD) remains elusive.

METHODS

Three-hundred-one patients across the spectrum of ALD including fatty liver (FL, N = 13), compensated cirrhosis (CC, N = 17), non-acute decompensation (NAD, N = 95), acute decompensation (AD, N = 51) and acute-on-chronic liver failure (ACLF, N = 125) were recruited between 2021 and 2023. Plasma myostatin, decorin levels, nutritional status, handgrip strength (HGS), systemic inflammation, infection, ammonia, disease course and 30-day mortality were recorded.

RESULTS

Patients aged 48 years (IQR: 38-52) and 97.7% of males were enrolled. Myostatin was elevated while decorin was reduced in cirrhosis compared to without cirrhosis, and further in DC compared to CC (p < 0.001). A step-wise increase in myostatin and reduction in decorin was observed transitioning from NAD to AD to ACLF (p < 0.001). Myostatin was further increased and decorin was reduced along with the grades and organ failures in AD and ACLF (p < 0.001, each). Baseline decorin (AUC: 0.797) and its combination with MELD (AUC: 0.814) predicted disease resolution in AD and ACLF. Although, both myostatin (aOR: 18.96) and decorin (aOR: 0.02) could predict mortality, decorin was independent (aOR: 0.04) and additive to MELD (AUC of MELD+logDecorin + logTLC + HE-grade:0.815); p < 0.05 each. Myostatin increased and decorin reduced with inflammation, hyperammonaemia, malnutrition and HGS in AD and ACLF (p < 0.05, each).

CONCLUSION

Myokines are linked with malnutrition, fibrosis, systemic inflammation, organ failures, disease course and mortality in ALD. Decorin enhances the risk estimation of mortality of MELD in AD and ACLF. Therapeutic modulation of myokines is a potentially disease-modifying target in ALD.

Bibliometrics and knowledge mapping of the pathogenesis of hepatic encephalopathy in patients with liver cirrhosis

Background

Hepatic encephalopathy is a common and serious complication of decompensated cirrhosis. It can considerably contribute to economic burden and impaired quality of life. However, its pathogenesis remains unclear.

Method

In this study, we aimed to visually analyse the research status and development trends in hepatic encephalopathy pathogenesis using bibliometrics and knowledge mapping. Information regarding publications between 1978 and 2022 were obtained from the Web of Science Core Collection. CiteSpace was used to analyse and present data by year, author, institution, country, journal, reference, and keyword.

Results

A total of 1578 publications on hepatic encephalopathy pathogenesis in patients with cirrhosis were retrieved from Web of Science Core Collection. A gradual increasing trend in annual publications has occurred. The collaborative network analysis results suggest the United States of America, the University of London, and Bajaj, Jasmohan S as the most influential country, institution, and author, respectively, in this research field. Notably, China appeariiuis to be the most promising country. Research on 'hepatology' garners the most significant papers in the field. Combined with reference co-citation and keyword co-occurrence analyses, we found that ammonia metabolism, gut microbiota, sarcopenia, and trace elements will become future research frontiers that are likely to be explored for a considerable length of time.

Conclusion

Future research directions in HE pathogenesis may target modulating the ammonia metabolism, the gut microbiota, sarcopenia, and trace elements.

The Value of Ammonia as a Biomarker in Patients with Cirrhosis

Ammonia is a product of amino acid metabolism that accumulates in the blood of patients with cirrhosis and plays a pivotal role in the pathogenesis of hepatic encephalopathy (HE). Despite being one of the main drivers of brain dysfunction, for many years international societies stated that increased blood ammonia does not add any diagnostic, staging, or prognostic value for HE in patients with cirrhosis. Nonetheless, in the last decades, evidence is emerging that supports the utility of ammonia for risk stratification, but its role in guiding HE diagnosis, staging, and treatment is unclear and there is equipoise in its use in clinical practice. This review provides the latest evidence on the value of ammonia as a biomarker in patients with cirrhosis. Although correct measurement of ammonia requires disciplined sample collection, it provides extremely useful clinical guidance for the diagnosis of HE, offers prognostic information, and it defines a therapeutic target.

Ammonia transporter RhBG initiates downstream signaling and functional responses by activating NFκB

Transceptors, solute transporters that facilitate intracellular entry of molecules and also initiate intracellular signaling events, have been primarily studied in lower-order species. Ammonia, a cytotoxic endogenous metabolite, is converted to urea in hepatocytes for urinary excretion in mammals. During hyperammonemia, when hepatic metabolism is impaired, nonureagenic ammonia disposal occurs primarily in skeletal muscle. Increased ammonia uptake in skeletal muscle is mediated by a membrane-bound, 12 transmembrane domain solute transporter, Rhesus blood group-associated B glycoprotein (RhBG). We show that in addition to its transport function, RhBG interacts with myeloid differentiation primary response-88 (MyD88) to initiate an intracellular signaling cascade that culminates in activation of NFκB. We also show that ammonia-induced MyD88 signaling is independent of the canonical toll-like receptor-initiated mechanism of MyD88-dependent NFκB activation. In silico, in vitro, and in situ experiments show that the conserved cytosolic J-domain of the RhBG protein interacts with the Toll-interleukin-1 receptor (TIR) domain of MyD88. In skeletal muscle from human patients, human-induced pluripotent stem cell-derived myotubes, and myobundles show an interaction of RhBG-MyD88 during hyperammonemia. Using complementary experimental and multiomics analyses in murine myotubes and mice with muscle-specific RhBG or MyD88 deletion, we show that the RhBG-MyD88 interaction is essential for the activation of NFkB but not ammonia transport. Our studies show a paradigm of substrate-dependent regulation of transceptor function with the potential for modulation of cellular responses in mammalian systems by decoupling transport and signaling functions of transceptors.

Association of Omega-3 Polyunsaturated Fatty Acids with Sarcopenia in Liver Cirrhosis Patients with Hepatocellular Carcinoma

Background and Aims

Sarcopenia is associated with the prognosis of patients with liver cirrhosis and hepatocellular carcinoma (HCC). Given their diverse physiological activities, we hypothesized that plasma fatty acids might influence the progression of sarcopenia. This study aimed to clarify the association between fatty acids and sarcopenia in cirrhotic patients with HCC.

Methods

In this single-center retrospective study, we registered 516 cases and analyzed 414 cases of liver cirrhosis and HCC. The skeletal muscle mass index was measured using a transverse computed tomography scan image at the third lumbar vertebra. The cutoff value for sarcopenia followed the criteria set by the Japan Society of Hepatology. Fatty acid concentrations were measured by gas chromatography.

Results

Fatty acid levels, particularly omega-3 (n-3) polyunsaturated fatty acid (PUFA), were lower in patients with poor liver function (Child-Pugh grade B/C) and were negatively correlated with the albumin-bilirubin score (p<0.0001). The prognosis of HCC patients with low PUFA levels was significantly worse. Among the different fatty acid fractions, only n-3 PUFAs significantly correlated with skeletal muscle mass index (p=0.0026). In the multivariate analysis, the n-3 PUFA level was an independent variable associated with sarcopenia (p=0.0006).

Conclusions

A low level of n-3 PUFAs was associated with sarcopenia in patients with liver cirrhosis and HCC.

Impact of osteopenia and osteosarcopenia on the outcomes after surgery of hepatobiliary-pancreatic cancers

Objective

The purpose of this study is to investigate potential associations between osteopenia, osteosarcopenia, and postoperative outcomes in patients with hepatobiliary-pancreatic cancer (HBPC).

Methods

Three online databases, including Embase, PubMed, and the Cochrane Library, were thoroughly searched for literature describing the relationship between osteopenia, osteosarcopenia, and outcomes of surgical treatment of HBPC patients from the start of each database to September 29, 2023. The Newcastle-Ottawa Scale was used to rate the quality of the studies.

Results

This analysis included a total of 16 articles with a combined patient cohort of 2,599 individuals. The results demonstrated that HBPC patients with osteopenia had significantly inferior OS (HR: 2.27, 95% CI: 1.70-3.03, p < 0.001) and RFS (HR: 1.96, 95% CI: 1.42-2.71, p < 0.001) compared to those without osteopenia. Subgroup analysis demonstrated that these findings were consistent across univariate and multivariate analyses, as well as hepatocellular carcinoma, biliary tract cancer, and pancreatic cancer. The risk of postoperative major complications was significantly higher in patients with osteopenia compared to those without osteopenia (OR: 1.66, 95% CI: 1.19-2.33, p < 0.001). Besides, we also found that the presence of osteosarcopenia in HBPC patients was significantly related to poorer OS (HR: 3.31, 95% CI: 2.00-5.48, p < 0.001) and PFS (HR: 2.50, 95% CI: 1.62-3.84, p < 0.001) in comparison to those without osteosarcopenia.

Conclusion

Preoperative osteopenia and osteosarcopenia can predict poorer OS and RFS with HBPC after surgery.

Liver cirrhosis: current status and treatment options using western or traditional Chinese medicine

Liver cirrhosis arises from liver fibrosis and necroinflammation caused by various mechanisms of hepatic injury. It is a prevalent condition in clinical practice characterized by hepatocellular dysfunction, portal hypertension, and associated complications. Despite its common occurrence, the etiology and pathogenesis of liver cirrhosis remain incompletely understood, posing a significant health threat. Effective prevention of its onset and progression is paramount in medical research. Symptoms often include discomfort in the liver area, while complications such as sarcopenia, hepatic encephalopathy, ascites, upper gastrointestinal bleeding, and infection can arise. While the efficacy of Western medicine in treating liver cirrhosis is uncertain, Chinese medicine offers distinct advantages. This review explores advancements in liver cirrhosis treatment encompassing non-pharmacological and pharmacological modalities. Chinese medicine interventions, including Chinese medicine decoctions, Chinese patent medicines, and acupuncture, exhibit notable efficacy in cirrhosis reversal and offer improved prognoses. Nowadays, the combination of Chinese and Western medicine in the treatment of liver cirrhosis also has considerable advantages, which is worthy of further research and clinical promotion. Standardized treatment protocols based on these findings hold significant clinical implications.

Prevalence of Osteosarcopenia and Frailty in Patients with Chronic Liver Disease

Introduction

Chronic liver disease (CLD) can have a significant impact on the nutritional status of patients. Malnutrition is an under-recognized condition in patients with cirrhosis. Malnutrition increases the incidence and severity of decompensation, increases the risk of infections, and increases mortality. The present study aimed to assess osteosarcopenia and frailty in patients with CLD.

Materials and methods

This prospective cross-sectional study included 151 cases of CLD, aged between 18 and 85 years. Anthropometric measurements were performed. Sarcopenia was assessed by handgrip strength using a hand-held dynamometer. Bone mineral density was measured with the help of an office-based DEXA scan (Osteosys). Liver frailty was assessed through performance-based tests.

Results

Out of 151 patients, 98 were male (69.5%); mean age was 51.8 ± 13.2. The presarcopenia was seen in 91 (60%) patients, and sarcopenia in 45(30%). Osteopenia was present in 75 (50%) and osteoporosis in 24 (16%). The patients with osteopenia and osteoporosis had a high liver frailty index (LFI) (p-value < 0.001). A significant correlation between body mass index, waist circumference, LFI, calcium level, bilirubin and Child Pugh scores was seen with T and Z scores. Factors associated with low bone mineral density included increasing age and LFI, low calcium and higher PTH.

Conclusion

There is a high prevalence of pre-sarcopenia, sarcopenia, osteopenia, osteoporosis and high frailty in our patients with CLD. Early detection and timely intervention in these conditions are important to reduce the associated consequences. All patients with CLD should be assessed for osteosarcopenia and frailty, both at baseline and longitudinally.

How to cite this article

Nazir S, Abbas Z, Amjad S, et al. Prevalence of Osteosarcopenia and Frailty in Patients with Chronic Liver Disease. Euroasian J Hepato-Gastroenterol 2024;14(2):156-159.

Frontiers in sarcopenia: Advancements in diagnostics, molecular mechanisms, and therapeutic strategies

The onset of sarcopenia is intimately linked with aging, posing significant implications not only for individual patient quality of life but also for the broader societal healthcare framework. Early and accurate identification of sarcopenia and a comprehensive understanding of its mechanistic underpinnings and therapeutic targets paramount to addressing this condition effectively. This review endeavors to present a cohesive overview of recent advancements in sarcopenia research and diagnosis. We initially delve into the contemporary diagnostic criteria, specifically referencing the European Working Group on Sarcopenia in Older People (EWGSOP) 2 and Asian Working Group on Sarcopenia (AWGS) 2019 benchmarks. Additionally, we elucidate comprehensive assessment techniques for muscle strength, quantity, and physical performance, highlighting tools such as grip strength, chair stand test, dual-energy X-ray Absorptiometry (DEXA), bioelectrical impedance analysis (BIA), gait speed, and short physical performance battery (SPPB), while also discussing their inherent advantages and limitations. Such diagnostic advancements pave the way for early identification and unequivocal diagnosis of sarcopenia. Proceeding further, we provide a deep-dive into sarcopenia's pathogenesis, offering a thorough examination of associated signaling pathways like the Myostatin, AMP-activated protein kinase (AMPK), insulin/IGF-1 Signaling (IIS), and the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) pathways. Each pathway's role in sarcopenia mediation is detailed, underscoring potential therapeutic target avenues. From a mechanistic perspective, the review also underscores the pivotal role of mitochondrial dysfunction in sarcopenia, emphasizing elements such as mitochondrial oxidative overload, mitochondrial biogenesis, and mitophagy, and highlighting their therapeutic significance. At last, we capture recent strides made in sarcopenia treatment, ranging from nutritional and exercise interventions to potential pharmacological and supplementation strategies. In sum, this review meticulously synthesizes the latest scientific developments in sarcopenia, aiming to enhance diagnostic precision in clinical practice and provide comprehensive insights into refined mechanistic targets and innovative therapeutic interventions, ultimately contributing to optimized patient care and advancements in the field.

Review article: Evaluation and care of the critically ill patient with cirrhosis

BACKGROUND

The increase in prevalence of liver disease globally will lead to a substantial incremental burden on intensive care requirements. While liver transplantation offers a potential life-saving intervention, not all patients are eligible due to limitations such as organ availability, resource constraints, ongoing sepsis or multiple organ failures. Consequently, the focus of critical care of patients with advanced and decompensated cirrhosis turns to liver-centric intensive care protocols, to mitigate the high mortality in such patients.

AIM

Provide an updated and comprehensive understanding of cirrhosis management in critical care, and which includes emergency care, secondary organ failure management (mechanical ventilation, renal replacement therapy, haemodynamic support and intensive care nutrition), use of innovative liver support systems, infection control, liver transplantation and palliative and end-of life care.

METHODS

We conducted a structured bibliographic search on PubMed, sourcing articles published up to 31 March 2024, to cover topics addressed. We considered data from observational studies, recommendations of society guidelines, systematic reviews, and meta-analyses, randomised controlled trials, and incorporated our clinical expertise in liver critical care.

RESULTS

Critical care management of the patient with cirrhosis has evolved over time while mortality remains high despite aggressive management with liver transplantation serving as a crucial but not universally available resource.

CONCLUSIONS

Implementation of organ support therapies, intensive care protocols, nutrition, palliative care and end-of-life discussions and decisions are an integral part of critical care of the patient with cirrhosis. A multi-disciplinary approach towards critical care management is likely to yield better outcomes.

Recent advances in the prevention and treatment of decompensated cirrhosis and acute-on-chronic liver failure (ACLF) and the role of biomarkers

The progression of cirrhosis with clinically significant portal hypertension towards decompensated cirrhosis remains clinically challenging and the evolution towards acute-on-chronic liver failure (ACLF), with one or more extrahepatic organ failures, is associated with very high mortality. In the last decade, significant progress has been made in the understanding of the mechanisms leading to decompensation and ACLF. As portal hypertension advances, bacterial translocation across an impaired gut barrier culminates in endotoxaemia, systemic inflammation and cirrhosis-associated immune dysfunction (CAID). Gut-derived systemic inflammation and CAID have become the logical targets for innovative therapies that prevent hepatic decompensation episodes and the progression to ACLF.Furthermore, classification of disease and biomarker discovery to personalise care have advanced in the field. This review discusses progress in biomarker discovery and personalisation of treatment in decompensated cirrhosis and ACLF.

Advances in sarcopenia: mechanisms, therapeutic targets, and intervention strategies

Sarcopenia is a multifactorial condition characterized by loss of muscle mass. It poses significant health risks in older adults worldwide. Both pharmacological and non-pharmacological approaches are reported to address this disease. Certain dietary patterns, such as adequate energy intake and essential amino acids, have shown positive outcomes in preserving muscle function. Various medications, including myostatin inhibitors, growth hormones, and activin type II receptor inhibitors, have been evaluated for their effectiveness in managing sarcopenia. However, it is important to consider the variable efficacy and potential side effects associated with these treatments. There are currently no drugs approved by the Food and Drug Administration for sarcopenia. The ongoing research aims to develop more effective strategies in the future. Our review of research on disease mechanisms and drug development will be a valuable contribution to future research endeavors.

Diagnostic and Prognostic Value of Hyperammonemia in Patients with Liver Cirrhosis, Hepatic Encephalopathy, and Sarcopenia (Experts’ Agreement)

Introduction. In cirrhotic patients, hyperammonemia develops due to impaired ammonia detoxification and portosystemic blood shunting and is most commonly associated with hepatic encephalopathy and sarcopenia. Currently, there are questions regarding the diagnosis of hyperammonemia and the effect of ammonia-lowering therapy on disease outcomes.

Materials and methods. The Russian Scientific Liver Society selected a panel of seven experts in liver cirrhosis research and management of patients with this disease to make reasoned statements and recommendations on the issue of diagnostic and prognostic value of hyperammonemia in patients with liver cirrhosis, hepatic encephalopathy and sarcopenia.

Results. The Delphi panel identified the most relevant topics, in the form of PICO questions (patient or population, intervention, comparison, outcome). The Delphi panel made six questions relevant to clinical practice and gave reasoned answers, framed as ‘clinical practice recommendations and statements’ with evidence-based comments. The questions and statements were based on the search and critical analysis of medical literature by keywords in Englishand Russian-language databases. The formulated questions could be combined into four categories: hepatic encephalopathy, sarcopenia, hyperammonemia, and ammonia-lowering therapy.

Conclusions. The results of the experts' work are directly relevant to the quality management of patients with liver cirrhosis, and their recommendations and statements can be used in clinical practice.

Prevalence and effect on prognosis of sarcopenia in patients with primary biliary cholangitis

Background

Sarcopenia adversely affects the treatment outcomes in Cirrhosis and NAFLD. However, such research is limited in primary biliary cholangitis (PBC) patients. This study was performed to examine the prevalence of sarcopenia and its impact on PBC patients' prognoses.

Methods

This study enrolled confirmed PBC patients who had an abdominal CT scan. Sarcopenia was determined by the L3-skeletal muscle index with a Chinese population-based cut-off value. Laboratory test values and liver stiffness measurements values were obtained from the electronic medical records.

Results

In total, 174 PBC patients with a median age of 54 (IQR, 48, 62) years old, were enrolled. 45 (25.9%) patients among them were diagnosed with sarcopenia. Univariate and multivariate logistic regression results illustrated that male gender (OR = 9.152, 95%CI = 3.131-26.751, p < 0.001) and LSM ≥ 12.8 kPa (OR = 4.539, 95%CI = 1.651, 12.478, p = 0.003) were the independent risk factors of sarcopenia in PBC patients. In the prognosis analysis, sarcopenia was determined as a risk factor for indicating adverse events in PBC patients (HR = 4.058, 95%CI = 1.955-8.424, p < 0.001) by Cox proportional hazards regression.

Conclusion

The current findings illustrate that comprehensive evaluation and management of sarcopenia may contribute to the improvement of treatment outcomes and life quality of PBC patients.

Long-Range Epitaxial MOF Electronics for Continuous Monitoring of Human Breath Ammonia

As an important biomarker, ammonia exhibits a strong correlation with protein metabolism and specific organ dysfunction. Limited by the immobile instrumental structure, invasive and complicated procedures, and unsatisfactory online sensitivity and selectivity, current medical diagnosis fails to monitor this chemical in real time efficiently. Herein, we present the successful synthesis of a long-range epitaxial metal-organic framework on a millimeter domain-sized single-crystalline graphene substrate (LR-epi-MOF). With a perfect 30° epitaxial angle and a mere 2.8% coincidence site lattice mismatch between the MOF and graphene, this long-range-ordered epitaxial structure boosts the charge transfer from ammonia to the MOF and then to graphene, thereby promoting the overall charge delocalization and exhibiting extraordinary electrical global coupling properties. This unique characteristic imparts a remarkable sensitivity of 0.1 ppb toward ammonia. The sub-ppb detecting capability and high anti-interference ability enable continuous information recording of breath ammonia that is strongly correlated with the intriguing human lifestyle. Wearable electronics based on the LR-epi-MOF could accurately portray the active protein metabolism pattern in real time and provide personal assistance in health management.

Probiotics as Potential Therapeutic Agents: Safeguarding Skeletal Muscle against Alcohol-Induced Damage through the Gut-Liver-Muscle Axis

Probiotics have shown the potential to counteract the loss of muscle mass, reduce physical fatigue, and mitigate inflammatory response following intense exercise, although the mechanisms by which they work are not very clear. The objective of this review is to describe the main harmful effects of alcohol on skeletal muscle and to provide important strategies based on the use of probiotics. The excessive consumption of alcohol is a worldwide problem and has been shown to be crucial in the progression of alcoholic liver disease (ALD), for which, to date, the only therapy available is lifestyle modification, including cessation of drinking. In ALD, alcohol contributes significantly to the loss of skeletal muscle, and also to changes in the intestinal microbiota, which are the basis for a series of problems related to the onset of sarcopenia. Some of the main effects of alcohol on the skeletal muscle are described in this review, with particular emphasis on the "gut-liver-muscle axis", which seems to be the primary cause of a series of muscle dysfunctions related to the onset of ALD. The modulation of the intestinal microbiota through probiotics utilization has appeared to be crucial in mitigating the muscle damage induced by the high amounts of alcohol consumed.

Association between sarcopenia and hepatic encephalopathy after transjugular intrahepatic portosystemic shunt in patients with cirrhosis: a systematic review and meta-analysis

PURPOSE

The association between the presence of sarcopenia in patients with cirrhosis and the onset of hepatic encephalopathy (HE) after transjugular intrahepatic portosystemic shunt (TIPS) is yet to be established. We conducted a systematic review and meta-analysis to provide a thorough summary of the available evidence on this association.

METHODS

A thorough search of the literature was performed in the PubMed, EMBASE, and Web of Science databases. The protocol was duly registered on PROSPERO (CRD42023398856). The hazard ratio (HR) and corresponding 95% confidence intervals (CIs) for the occurrence of HE after TIPS were extracted from studies comparing cirrhotic patients with and without sarcopenia. These data were then combined using a random-effect model.

RESULTS

A total of 1135 patients from seven cohort studies that met our eligibility criteria were included in the meta-analysis. Our findings indicate a significantly higher risk of post-TIPS HE among cirrhotic patients with sarcopenia compared to those without sarcopenia (HR, 2.35; 95% CIs 1.32-4.19; p = 0.004; I2 = 75%). The findings remained consistent across subgroups stratified by liver disease etiology, study location, and severity of hepatic dysfunction.

CONCLUSION

The study demonstrated that sarcopenia was strongly linked to an increased likelihood post-TIPS HE among cirrhotic patients.

L-Isoleucine reverses hyperammonemia-induced myotube mitochondrial dysfunction and post-mitotic senescence

Perturbations in the metabolism of ammonia, a cytotoxic endogenous metabolite, occur in a number of chronic diseases, with consequent hyperammonemia. Increased skeletal muscle ammonia uptake causes metabolic, molecular, and phenotype alterations including cataplerosis of (loss of tricarboxylic acid cycle (TCA) cycle intermediate) α-ketoglutarate (αKG), mitochondrial oxidative dysfunction, and senescence-associated molecular phenotype (SAMP). L-Isoleucine (Ile) is an essential, branched-chain amino acid (BCAA) that simultaneously provides acetyl-CoA as an oxidative substrate and succinyl-CoA for anaplerosis (providing TCA cycle intermediates). Our multiomics analyses in myotubes and skeletal muscle from hyperammonemic mice and human patients with cirrhosis showed perturbations in BCAA transporters and catabolism. We, therefore, determined if Ile reverses hyperammonemia-induced impaired mitochondrial oxidative function and SAMP. Studies were performed in differentiated murine C2C12 myotubes that were early passage, late passage (senescent), or those depleted of LAT1/SLC7A5 and human induced pluripotent stem cell-derived myotubes (hiPSCM). Ile reverses hyperammonemia-induced reduction in the maximum respiratory capacity, complex I, II, and III functions in early passage murine myotubes and hiPSCM. Consistently, low ATP content and impaired global protein synthesis (high energy requiring cellular process) during hyperammonemia are reversed by Ile in murine myotubes and hiPSCM. Lower abundance of critical regulators of protein synthesis in mTORC1 signaling, and increased phosphorylation of eukaryotic initiation factor 2α are also reversed by Ile. Genetic depletion studies showed that Ile responses are independent of the amino acid transporter LAT1/SLC7A5. Our studies show that Ile reverses the hyperammonemia-induced impaired mitochondrial oxidative function, cataplerosis, and SAMP in a LAT1/SLC7A5 transporter-independent manner.

What Does Sarcopenia Have to Do with Nonalcoholic Fatty Liver Disease?

Nonalcoholic fatty liver disease (NAFLD) is one of the most common causes of chronic liver disease. As the second stage of developing steatosis, nonalcoholic hepatitis (NASH) carries the risk of fibrosis, cirrhosis, and hepatocellular carcinoma. Sarcopenia is defined as a condition characterized by a decrease in muscle mass and functional decline. Both NAFLD and sarcopenia are global problems. The pathophysiological mechanisms that link the two entities of the disease are insulin resistance, inflammation, nutritional deficiencies, impairment of myostatin and adiponectin, or physical inactivity. Furthermore, disorders of the gut-liver axis appear to induce the process of developing NAFLD and sarcopenia. The correlations between NAFLD and sarcopenia appear to be bidirectional, so the main objective of the review was to determine the cause-and-effect relationship between the two diseases.

Assessing the risk factors associated with sarcopenia in patients with liver cirrhosis: a case-control study

Sarcopenia is a disease characterized by decreased muscle mass and strength, affecting 20-70% of patients with cirrhosis, and is associated with poor prognosis, complications, and high mortality. At present, the epidemiological investigation of sarcopenia in patients with liver cirrhosis is relatively limited, and because of the differences in population characteristics, regions, diagnostic criteria and diagnostic tools, the prevalence of sarcopenia in various studies varies greatly. The definition of sarcopenia in this study adopted the criteria of the Asian Working Group on Sarcopenia (AWGS 2019), including muscle mass and muscle strength / physical performance. A total of 271 patients with liver cirrhosis were included in this cross-sectional study to explore the influencing factors of sarcopenia in patients with liver cirrhosis. The prevalence of sarcopenia was 27.7%, 27.3% in male and 28.4% in female. The results of binary logistic regression analysis showed that age, physical activity, BMI, mid-upper arm muscle circumference, hepatic encephalopathy, nutritional status, alkaline phosphatase, albumin and total cholesterol were significantly correlated with the occurrence of sarcopenia in patients with liver cirrhosis. After adjusting for the potential influencing factors, it was found that the correlation between age and sarcopenia was weakened (OR = 0.870, 95% CI 0.338-2.239). The current findings show that sarcopenia is common in patients with cirrhosis and is independently associated with age, physical activity, BMI, nutritional status, and albumin, and serum alkaline phosphatase and total cholesterol are associated with the development of sarcopenia. Regular exercise may help maintain the grip strength of patients with cirrhosis and delay the deterioration of liver function.

The pan-liver network theory: From traditional chinese medicine to western medicine

In traditional Chinese medicine (TCM), the liver is the "general organ" that is responsible for governing/maintaining the free flow of qi over the entire body and storing blood. According to the classic five elements theory, zang-xiang theory, yin-yang theory, meridians and collaterals theory, and the five-viscera correlation theory, the liver has essential relationships with many extrahepatic organs or tissues, such as the mother-child relationships between the liver and the heart, and the yin-yang and exterior-interior relationships between the liver and the gallbladder. The influences of the liver to the extrahepatic organs or tissues have been well-established when treating the extrahepatic diseases from the perspective of modulating the liver by using the ancient classic prescriptions of TCM and the acupuncture and moxibustion. In modern medicine, as the largest solid organ in the human body, the liver has the typical functions of filtration and storage of blood; metabolism of carbohydrates, fats, proteins, hormones, and foreign chemicals; formation of bile; storage of vitamins and iron; and formation of coagulation factors. The liver also has essential endocrine function, and acts as an immunological organ due to containing the resident immune cells. In the perspective of modern human anatomy, physiology, and pathophysiology, the liver has the organ interactions with the extrahepatic organs or tissues, for example, the gut, pancreas, adipose, skeletal muscle, heart, lung, kidney, brain, spleen, eyes, skin, bone, and sexual organs, through the circulation (including hemodynamics, redox signals, hepatokines, metabolites, and the translocation of microbiota or its products, such as endotoxins), the neural signals, or other forms of pathogenic factors, under normal or diseases status. The organ interactions centered on the liver not only influence the homeostasis of these indicated organs or tissues, but also contribute to the pathogenesis of cardiometabolic diseases (including obesity, type 2 diabetes mellitus, metabolic [dysfunction]-associated fatty liver diseases, and cardio-cerebrovascular diseases), pulmonary diseases, hyperuricemia and gout, chronic kidney disease, and male and female sexual dysfunction. Therefore, based on TCM and modern medicine, the liver has the bidirectional interaction with the extrahepatic organ or tissue, and this established bidirectional interaction system may further interact with another one or more extrahepatic organs/tissues, thus depicting a complex "pan-hepatic network" model. The pan-hepatic network acts as one of the essential mechanisms of homeostasis and the pathogenesis of diseases.

Novel Therapeutic Approaches in Treatment of Acute-on-Chronic Liver Failure

Acute-on-chronic liver failure (ACLF), a clinical syndrome that can develop at any stage in the progression of cirrhotic liver disease, is characterized by an acute decompensation in liver function with associated multiorgan failure and high short-term mortality. Current evidence points to ACLF being reversible, particularly in those at the lower end of the severity spectrum. However, there are no specific treatments for ACLF, and overall outcomes remain poor. Expedited liver transplantation as a treatment option is limited by organ shortage and a lack of priority allocation for this indication. Other options are therefore urgently needed, and our improved understanding of the condition has led to significant efforts to develop novel therapies. In conclusion, this review aims to summarize the current understanding of the pathophysiological processes involved in the onset, progression, and recovery of ACLF and discuss novel therapies under development.

Sarcopenia in liver cirrhosis: perspectives from epigenetics and microbiota

Sarcopenia is characterized by the loss of muscle mass and function. It is well known that sarcopenia is often associated with aging, while in recent years, sarcopenia comorbid with chronic diseases such as cirrhosis has attracted widespread attention, whose underlying molecular mechanisms remain unclear. Since cirrhosis and sarcopenia are assumed to be closely interrelated in terms of pathogenesis, this review innovatively discussed the role of epigenetic modifications and microecological dysregulation in sarcopenia in the context of liver cirrhosis. Here we illustrated the relationship between sarcopenia and cirrhosis in the aspect of epigenetics, dysbiosis, and the crosstalk between gene modifications and intestinal microecology. Furthermore, the alterations in cirrhosis patients with sarcopenia, such as inflammatory response and oxidative stress, are found to present synergistic effects in the pathways of epigenetics and dysbiosis leading to sarcopenia. This review proposes that microbiome-based therapies are promising to break the vicious cycle between epigenetic modification and dysbiosis, providing strong support for the use of intestinal microecological interventions to prevent sarcopenia in cirrhotic patients.

Glucagon-like peptide-1 receptor agonist, semaglutide attenuates chronic liver disease-induced skeletal muscle atrophy in diabetic mice

A glucagon-like peptide-1 receptor agonist (GLP-1RA) has recently been established as a pharmacological option for the treatment of type 2 diabetes. Recent studies have demonstrated the molecular role of GLP-1R in skeletal muscle homeostasis; however, the therapeutic efficacy of semaglutide, a GLP-1RA, on skeletal muscle atrophy in chronic liver disease (CLD) under diabetic conditions remains unclear. In the present study, semaglutide effectively inhibited psoas muscle atrophy and suppressed declines in grip strength in a diethoxycarbonyl-1,4-dihydrocollidine (DDC) diet-fed diabetic KK-Ay mouse model. Moreover, semaglutide inhibited ubiquitin-proteosome-mediated skeletal muscle proteolysis and promoted myogenesis in palmitic acid (PA)-stimulated C2C12 murine myocytes. Mechanistically, this effect of semaglutide on skeletal muscle atrophy was mediated by multiple functional pathways. First, semaglutide protected against hepatic injury in mice accompanied by increased production of insulin-like growth factor 1 and reduced accumulation of reactive oxygen species (ROS). These effects were associated with decreased proinflammatory cytokines and ROS accumulation, leading to the suppression of ubiquitin-proteosome muscle degradation. Moreover, semaglutide inhibited the amino acid starvation-related stress signaling that was activated under chronic liver injury, resulting in the recovery of the mammalian target of rapamycin activity in the skeletal muscle of DDC-diet fed KK-Ay mice. Second, semaglutide improved skeletal muscle atrophy by directly stimulating GLP-1R in myocytes. Semaglutide induced cAMP-mediated activation of PKA and AKT, enhanced mitochondrial biogenesis, and reduced ROS accumulation, thereby resulting in inhibition of NF-κB/myostatin-mediated ubiquitin-proteosome degradation and the augmentation of heat-shock factor-1-mediated myogenesis. Collectively, semaglutide may have potential as a new therapeutic strategy for CLD-related skeletal muscle wasting.

Myostatin is associated with the presence and development of acute-on-chronic liver failure

BACKGROUND & AIMS

Acute-on-chronic liver failure (ACLF) has been linked to different pathophysiological mechanisms, including systemic inflammation and mitochondrial dysfunction. Sarcopenia has also been proposed as a potential mechanism; myostatin is a key factor inducing sarcopenia. Therefore, this study aimed to evaluate the association of myostatin levels with the development of ACLF and mortality in patients with cirrhosis.

METHODS

We performed a prospective cohort study, including both outpatient and hospitalized patients with cirrhosis. Clinical, biochemical, and nutritional parameters were evaluated, and the development of acute decompensation (AD) or ACLF during follow-up was recorded. ACLF was defined according to the EASL-CLIF criteria. Receiver-operating characteristic, Kaplan-Meier and Cox regression analyses were performed.

RESULTS

A total of 186 patients with the whole spectrum of cirrhosis were included; mean age was 53.4 ± 14 years, mean Child-Pugh score was 8 ± 2.5 and mean MELD score was 15 ± 8. There was a stepwise decrease in myostatin levels from a compensated stage to AD and ACLF. Myostatin correlated positively with nutritional markers and negatively with severity scores. The prevalence of sarcopenia was 73.6%. During follow-up, 27.9% of patients developed AD and 25.8% developed ACLF. Most episodes were grade 2-3, mainly (62.5%) precipitated by infections. The most common organ failures observed were in the liver (63.3%) and the kidney (64.6%). Receiver-operating characteristic analysis yielded <1,280 pg/ml as the best serum myostatin cut-off for the prediction of ACLF. In Kaplan-Meier curves and multivariate analysis, myostatin levels remained independently associated with the incidence of ACLF and survival.

CONCLUSIONS

There is a progressive decrease in myostatin levels as cirrhosis progresses, demonstrating an association of sarcopenia with the development of ACLF and increased mortality.

IMPACT AND IMPLICATIONS

Myostatin is a muscle hormone, it is decreased in patients with muscle loss and is a marker of impaired muscle function. In this study we show that myostatin levels are decreased in patients with cirrhosis, with lower levels in patients with acute decompensation and acute-on chronic liver failure (ACLF). Low myostatin levels in cirrhosis predict the development of ACLF and mortality independently of liver disease severity and sex.

Sarcopenia in cirrhosis: Prospects for therapy targeted to gut microbiota

Decreased muscle mass and function, also known as sarcopenia, is common in patients with cirrhosis and is associated with a poor prognosis. Although the pathogenesis of this disorder has not been fully elucidated, a disordered gut-muscle axis probably plays an important role. Decreased barrier function of the gut and liver, gut dysbiosis, and small intestinal bacterial overgrowth (SIBO) can lead to increased blood levels of ammonia, lipopolysaccharides, pro-inflammatory mediators, and myostatin. These factors have complex negative effects on muscle mass and function. Drug interventions that target the gut microbiota (long-term use of rifaximin, lactulose, lactitol, or probiotics) positively affect most links of the compromised gut-muscle axis in patients with cirrhosis by decreasing the levels of hyperammonemia, bacterial translocation, and systemic inflammation and correcting gut dysbiosis and SIBO. However, although these drugs are promising, they have not yet been investigated in randomized controlled trials specifically for the treatment and prevention of sarcopenia in patients with cirrhosis. No data exist on the effects of fecal transplantation on most links of gut-muscle axis in cirrhosis; however, the results of animal experimental studies are promising.

GDF8 Contributes to Liver Fibrogenesis and Concomitant Skeletal Muscle Wasting

Patients with end-stage liver disease exhibit progressive skeletal muscle atrophy, highlighting a negative crosstalk between the injured liver and muscle. Our study was to determine whether TGFβ ligands function as the mediators. Acute or chronic liver injury was induced by a single or repeated administration of carbon tetrachloride. Skeletal muscle injury and repair was induced by intramuscular injection of cardiotoxin. Activin type IIB receptor (ActRIIB) ligands and growth differentiation factor 8 (Gdf8) were neutralized with ActRIIB-Fc fusion protein and a Gdf8-specific antibody, respectively. We found that acute hepatic injury induced rapid and adverse responses in muscle, which was blunted by neutralizing ActRIIB ligands. Chronic liver injury caused muscle atrophy and repair defects, which were prevented or reversed by inactivating ActRIIB ligands. Furthermore, we found that pericentral hepatocytes produce excessive Gdf8 in injured mouse liver and cirrhotic human liver. Specific inactivation of Gdf8 prevented liver injury-induced muscle atrophy, similar to neutralization of ActRIIB ligands. Inhibition of Gdf8 also reversed muscle atrophy in a treatment paradigm following chronic liver injury. Direct injection of exogenous Gdf8 protein into muscle along with acute focal muscle injury recapitulated similar dysregulated muscle regeneration as that observed with liver injury. The results indicate that injured liver negatively communicate with the muscle largely via Gdf8. Unexpectedly, inactivation of Gdf8 simultaneously ameliorated liver fibrosis in mice following chronic liver injury. In vitro, Gdf8 induced human hepatic stellate (LX-2) cells to form a septa-like structure and stimulated expression of profibrotic factors. Our findings identified Gdf8 as a novel hepatomyokine contributing to injured liver-muscle negative crosstalk along with liver injury progression.

Prevalence of Sarcopenia in Liver Cirrhosis: A Systematic Review and Meta-Analysis

INTRODUCTION

Chronic liver disease is often combined with a morbidity burden that strongly affects the functional domain. In liver cirrhosis (LC), qualitative and quantitative muscle wasting, known as sarcopenia, poses an added clinical burden, together with comorbidities and a poor quality of life.

METHODS

We conducted a systematic review and meta-analysis of the prevalence of sarcopenia in LC. The literature was screened through 6 electronic databases from the study's inception to January 2023. No exclusion criteria were applied to language, operative tools for diagnosing sarcopenia, population age, general health status, country, and study setting (cohort or cross-sectional). Two independent researchers applied the inclusion criteria in parallel to evaluate the eligibility of the 44 retrieved articles; only 36 met the eligibility requirements.

RESULTS

The total sample (N = 8,821) was slightly dominated by men (N = 4,941). The cross-sectional design predominated over the longitudinal, and the hospital setting was prevalent. The pooled prevalence of sarcopenia across the selected studies was 33% (95% confidence interval [CI] 0.32-0.34), with high heterogeneity ( I2 = 96%). A further meta-analysis using the Child-Pugh (CP) score to stage LC was conducted on 24 entries, and the results showed that for the LC populations classified with the CP-A, CP-B, and CP-C staging, respectively, the overall mean prevalence was 33% (95% CI 0.31-0.35), 36% (95% CI 0.34-0.39) and 46% (95% CI 0.43-0.50). The risk of bias was moderate. In LC, 1 in 3 patients suffers sarcopenia.

DISCUSSION

Poor management of muscle mass loss plays a role in the prognosis of death and quality of life of patients with LC. Clinicians in the field are recommended, when screening for sarcopenia, to pay close attention by carefully assessing body composition as part of the monitoring scheme.

Dysregulated cellular redox status during hyperammonemia causes mitochondrial dysfunction and senescence by inhibiting sirtuin-mediated deacetylation

Perturbed metabolism of ammonia, an endogenous cytotoxin, causes mitochondrial dysfunction, reduced NAD+ /NADH (redox) ratio, and postmitotic senescence. Sirtuins are NAD+ -dependent deacetylases that delay senescence. In multiomics analyses, NAD metabolism and sirtuin pathways are enriched during hyperammonemia. Consistently, NAD+ -dependent Sirtuin3 (Sirt3) expression and deacetylase activity were decreased, and protein acetylation was increased in human and murine skeletal muscle/myotubes. Global acetylomics and subcellular fractions from myotubes showed hyperammonemia-induced hyperacetylation of cellular signaling and mitochondrial proteins. We dissected the mechanisms and consequences of hyperammonemia-induced NAD metabolism by complementary genetic and chemical approaches. Hyperammonemia inhibited electron transport chain components, specifically complex I that oxidizes NADH to NAD+ , that resulted in lower redox ratio. Ammonia also caused mitochondrial oxidative dysfunction, lower mitochondrial NAD+ -sensor Sirt3, protein hyperacetylation, and postmitotic senescence. Mitochondrial-targeted Lactobacillus brevis NADH oxidase (MitoLbNOX), but not NAD+ precursor nicotinamide riboside, reversed ammonia-induced oxidative dysfunction, electron transport chain supercomplex disassembly, lower ATP and NAD+ content, protein hyperacetylation, Sirt3 dysfunction and postmitotic senescence in myotubes. Even though Sirt3 overexpression reversed ammonia-induced hyperacetylation, lower redox status or mitochondrial oxidative dysfunction were not reversed. These data show that acetylation is a consequence of, but is not the mechanism of, lower redox status or oxidative dysfunction during hyperammonemia. Targeting NADH oxidation is a potential approach to reverse and potentially prevent ammonia-induced postmitotic senescence in skeletal muscle. Since dysregulated ammonia metabolism occurs with aging, and NAD+ biosynthesis is reduced in sarcopenia, our studies provide a biochemical basis for cellular senescence and have relevance in multiple tissues.

Role of ammonia in NAFLD: An unusual suspect

Mechanistically, the symptomatology and disease progression of non-alcoholic fatty liver disease (NAFLD) remain poorly understood, which makes therapeutic progress difficult. In this review, we focus on the potential importance of decreased urea cycle activity as a pathogenic mechanism. Urea synthesis is an exclusive hepatic function and is the body's only on-demand and definitive pathway to remove toxic ammonia. The compromised urea cycle activity in NAFLD is likely caused by epigenetic damage to urea cycle enzyme genes and increased hepatocyte senescence. When the urea cycle is dysfunctional, ammonia accumulates in liver tissue and blood, as has been demonstrated in both animal models and patients with NAFLD. The problem may be augmented by parallel changes in the glutamine/glutamate system. In the liver, the accumulation of ammonia leads to inflammation, stellate cell activation and fibrogenesis, which is partially reversible. This may be an important mechanism for the transition of bland steatosis to steatohepatitis and further to cirrhosis and hepatocellular carcinoma. Systemic hyperammonaemia has widespread negative effects on other organs. Best known are the cerebral consequences that manifest as cognitive disturbances, which are prevalent in patients with NAFLD. Furthermore, high ammonia levels induce a negative muscle protein balance leading to sarcopenia, compromised immune function and increased risk of liver cancer. There is currently no rational way to reverse reduced urea cycle activity but there are promising animal and human reports of ammonia-lowering strategies correcting several of the mentioned untoward aspects of NAFLD. In conclusion, the ability of ammonia-lowering strategies to control the symptoms and prevent the progression of NAFLD should be explored in clinical trials.

Mechanisms of sarcopenia in liver cirrhosis and the role of myokines

Sarcopenia is a syndrome characterized by a decline in skeletal muscle quantity and/or quality, strength and performance, leading to unfortunate events, such as injurious falls or even death. It is not identical to frailty and malnutrition, even though there is a significant overlap among these syndromes. In patients with liver cirrhosis (LC), sarcopenia is classified as secondary and has been associated with increased morbidity and mortality during the pre- and post-transplantation period. It can be a result of malnutrition, hyperammonemia, low physical activity, endocrine abnormalities, accelerated starvation, metabolic disturbances, altered gut function leading to chronic inflammation, and alcohol abuse. Myokines are peptides mainly synthesized by contracting muscle and adipose tissue cells and may play a key role in the pathophysiology of sarcopenia. More than a hundred myokines have been recognized, but only a few have been investigated. They can be classified as negative regulators, such as myostatin, tumor growth factor-β, activins, growth differentiation factor-11, and positive regulators of muscle growth including follistatin, bone morphogenic proteins, and irisin. So far, only myostatin, follistatin, irisin and decorin have been studied in LC-associated sarcopenia. In this review, we focused on the mechanisms of cirrhosis-related sarcopenia and the role of myokines that have already been studied in the literature, either as markers helping in the diagnostic evaluation of sarcopenia, or as prognostic factors of survival. Standard therapeutic options to prevent or treat sarcopenia in LC are also being reported, as well as the possible therapeutic implication of myokines.