Branched-chain amino acids in liver disease: new aspects of long known phenomena

Frailty in end-stage liver disease: Understanding pathophysiology, tools for assessment, and strategies for management

Frailty and sarcopenia are frequently observed in patients with end-stage liver disease. Frailty is a complex condition that arises from deteriorations across various physiological systems, including the musculoskeletal, cardiovascular, and immune systems, resulting in a reduced ability of the body to withstand stressors. This condition is associated with declined resilience and increased vulnerability to negative outcomes, including disability, hospitalization, and mortality. In cirrhotic patients, frailty is influenced by multiple factors, such as hyperammonemia, hormonal imbalance, malnutrition, ascites, hepatic encephalopathy, and alcohol intake. Assessing frailty is crucial in predicting morbidity and mortality in cirrhotic patients. It can aid in making critical decisions regarding patients' eligibility for critical care and transplantation. This, in turn, can guide the development of an individualized treatment plan for each patient with cirrhosis, with a focus on prioritizing exercise, proper nutrition, and appropriate treatment of hepatic complications as the primary lines of treatment. In this review, we aim to explore the topic of frailty in liver diseases, with a particular emphasis on pathophysiology, clinical assessment, and discuss strategies for preventing frailty through effective treatment of hepatic complications. Furthermore, we explore novel assessment and management strategies that have emerged in recent years, including the use of wearable technology and telemedicine.

ESPEN practical guideline: Clinical nutrition in liver disease

BACKGROUND

The Practical guideline is based on the current scientific ESPEN guideline on Clinical Nutrition in Liver Disease.

METHODS

It has been shortened and transformed into flow charts for easier use in clinical practice. The guideline is dedicated to all professionals including physicians, dieticians, nutritionists and nurses working with patients with chronic liver disease.

RESULTS

A total of 103 statements and recommendations are presented with short commentaries for the nutritional and metabolic management of patients with (i) acute liver failure, (ii) alcoholic steatohepatitis, (iii) non-alcoholic fatty liver disease, (iv) liver cirrhosis, and (v) liver surgery/transplantation. The disease-related recommendations are preceded by general recommendations on the diagnostics of nutritional status in liver patients and on liver complications associated with medical nutrition.

CONCLUSION

This practical guideline gives guidance to health care providers involved in the management of liver disease to offer optimal nutritional care.

A Metabonomics Approach to Drug Toxicology in Liver Disease and its Application in Traditional Chinese Medicine

BACKGROUND

The progression of liver disease causes metabolic transformation in vivo and thus affects corresponding endogenous small molecular compounds. Metabonomics is a powerful technology which is able to assess global low-molecular-weight endogenous metabolites in a biological system. This review is intended to provide an overview of a metabonomics approach to the drug toxicology of diseases of the liver.

METHODS

The regulation of, and relationship between, endogenous metabolites and diseases of the liver is discussed in detail. Furthermore, the metabolic pathways involved in drug interventions of liver diseases are reviewed. Evaluation of the protective mechanisms of traditional Chinese medicine in liver diseases using metabonomics is also reviewed. Examples of applications of metabolite profiling concerning biomarker discovery are highlighted. In addition, new developments and future prospects are described.

RESULTS

Metabonomics can measure changes in metabolism relating to different stages of liver disease, so metabolic differences can provide a basis for the diagnosis, treatment and prognosis of various diseases.

CONCLUSION

Metabonomics has great advantages in all aspects of the therapy of liver diseases, with good prospects for clinical application.

ESPEN guideline on clinical nutrition in liver disease

This update of evidence-based guidelines (GL) aims to translate current evidence and expert opinion into recommendations for multidisciplinary teams responsible for the optimal nutritional and metabolic management of adult patients with liver disease. The GL was commissioned and financially supported by ESPEN. Members of the guideline group were selected by ESPEN. We searched for meta-analyses, systematic reviews and single clinical trials based on clinical questions according to the PICO format. The evidence was evaluated and used to develop clinical recommendations implementing the SIGN method. A total of 85 recommendations were made for the nutritional and metabolic management of patients with acute liver failure, severe alcoholic steatohepatitis, non-alcoholic fatty liver disease, liver cirrhosis, liver surgery and transplantation as well as nutrition associated liver injury distinct from fatty liver disease. The recommendations are preceded by statements covering current knowledge of the underlying pathophysiology and pathobiochemistry as well as pertinent methods for the assessment of nutritional status and body composition.

Muscle wasting and branched-chain amino acid, alpha-ketoglutarate, and ATP depletion in a rat model of liver cirrhosis

The aim of the study was to examine whether a rat model of liver cirrhosis induced by carbon tetrachloride (CCl4) is a suitable model of muscle wasting and alterations in amino acid metabolism in cirrhotic humans. Rats were treated by intragastric gavage of CCl4 or vehicle for 45 days. Blood plasma and different muscle types-tibialis anterior (mostly white fibres), soleus (red muscle) and extensor digitorum longus (white muscle) - were analysed at the end of the study. Characteristic biomarkers of impaired hepatic function were found in the plasma of cirrhotic animals. The weights and protein contents of all muscles of CCl4-treated animals were lower when compared with controls. Increased concentrations of glutamine (GLN) and aromatic amino acids (phenylalanine and tyrosine) and decreased concentrations of branched-chain amino acids (BCAA), glutamate (GLU), alanine and aspartate were found in plasma and muscles. In the soleus muscle, GLN increased more and GLU and BCAA decreased less than in the extensor digitorum and tibialis muscles. Increased chymotrypsin-like activity (indicating enhanced proteolysis) and decreased α-ketoglutarate and ATP levels were found in muscles of cirrhotic animals. ATP concentration also decreased in blood plasma. It is concluded that a rat model of CCl4-induced cirrhosis is a valid model for the investigation of hepatic cachexia that exhibits alterations in line with a theory of role of ammonia in pathogenesis of BCAA depletion, citric cycle and mitochondria dysfunction, and muscle wasting in cirrhotic subjects. The findings indicate more effective ammonia detoxification to GLN in red than in white muscles.

Dietary management and supplementation with branched-chain amino acids in cirrhosis of the liver

One of the most important characteristics of malnutrition is the loss of muscle mass and the severe depletion of the protein reserve, secondarily affecting energy metabolism. That impacts nutritional status and the progression of disease-related complications. Nutritional treatment is one of the main factors in the comprehensive management of those patients. Achieving adequate energy intake that provides the macronutrients and micronutrients necessary to prevent or correct malnutrition is attempted through dietary measures. ESPEN, the European Society for Clinical Nutrition and Metabolism, recommends a caloric intake of 30-40kcal/kg/day, in which carbohydrates provide 45-60% of the daily energy intake and proteins supply 1.0-1.5g/kg/day. The remaining portion of the total energy expenditure should be covered by lipids. The administration of branched-chain amino acids has been shown to be beneficial not only in counteracting malnutrition, but also as a coadjuvant treatment in specific complications, thus playing a favorable role in outcome and quality of life. Therefore, branched-chain amino acids should be considered part of nutritional treatment in patients with advanced stages of cirrhosis of the liver, particularly in the presence of complications.

Serum Metabonomics Analysis of Liver Failure Treated by Nonbioartificial Liver Support Systems

OBJECTIVE

To analyze the small molecular metabolic compounds of nonbioartificial liver for treatment of hepatic failure and make further efforts to study the clinical efficacy, mechanism of action, and pathogenesis of hepatic failure.

METHODS

52 patients who met the standard of artificial liver treatment for liver failure were enrolled; these patients included 6 cases of acute liver failure (11.54%), 3 cases of subacute liver failure (5.77%), acute-on-chronic liver failure in 10 cases (19.23%), and 33 cases of chronic liver failure (63.46%). Treatment modes included plasma exchange in 34 patients (65.38%), bilirubin adsorption in 9 patients (17.31%), and hemofiltration in 9 patients (17.31%). The clinical efficacy of artificial liver was assessed by monitoring the effects in the near future. Significant changes in metabolic compounds of liver failure in the treatment before and after artificial liver were screened by using Ultra-Performance Liquid Chromatography-Mass Spectrometry (UPLC-MS). Related metabolic pathways were analyzed by MetaboAnalyst.

RESULTS

After artificial liver treatment, the liver function and coagulation function of liver failure patients were significantly improved (P < 0.01), the Meld score was lower than that before treatment, and the difference was statistically significant (P < 0.05). Serum metabolomics identified 29 small metabolic compounds and 12 metabolic pathways with variable projection importance (VIP) greater than 1 before and after artificial liver treatment. There were 11 metabolic compounds of VIP over 1 and 7 metabolic pathways in the different modes of artificial liver treatment for chronic liver failure. Among them, bile acid metabolism, fatty acid metabolism, and amino acid metabolism are the main sources.

CONCLUSION

Artificial liver treatment can effectively improve liver function and blood coagulation function and Meld score, clinical symptoms and signs in patients with liver failure; the curative effect of artificial liver was verified, which reflected the clinical value of artificial liver in the treatment of liver failure. Artificial liver treatment of liver failure on fatty acids and primary bile acid synthesis pathway was the most significant. The difference of fatty acid, primary bile acid synthesis pathway, and phenylalanine metabolic pathway in different artificial liver patterns of chronic liver failure was the most significant. This provides a new basis for understanding the mechanism of hepatic failure and the mechanism of liver failure by artificial liver treatment.

Branched-chain amino acids in liver diseases

Branched chain amino acids (BCAAs) are involved in various bioprocess such as protein metabolism, gene expression, insulin resistance and proliferation of hepatocytes. BCAAs have also been reported to suppress the growth of hepatocellular carcinoma (HCC) cells in vitro and to be required for immune cells to perform the function. In advanced cirrhotic patients, it has been clarified that serum concentrations of BCAA are decreased, whereas those of aromatic amino acids (AAAs) are increased. These alterations are thought to be the causes of hepatic encephalopathy (HE), sarcopenia and hepatocarcinogenesis and may be associated with the poor prognosis of patients with these conditions. Administration of BCAA-rich medicines has shown positive results in patients with cirrhosis.

Plasma Amino Acid Concentrations Predict Mortality in Patients with End-Stage Liver Disease

BACKGROUND

The liver plays a key role in amino acid metabolism. In former studies, a ratio between branched-chain and aromatic amino acids (Fischer's ratio) revealed associations with hepatic encephalopathy. Furthermore, low concentrations of branched-chain amino acids were linked to sarcopenia in literature. Encephalopathy and sarcopenia are known to dramatically worsen the prognosis. Aim of this study was to investigate a complex panel of plasma amino acids in the context of mortality in patients with end-stage liver disease.

METHODS

166 patients evaluated for orthotopic liver transplantation were included. 19 amino acids were measured from citrated plasma samples using mass spectrometry. We performed survival analysis for plasma amino acid constellations and examined the relationship to established mortality predictors.

RESULTS

33/166 (19.9%) patients died during follow-up. Lower values of valine (p<0.001), Fischer's ratio (p<0.001) and valine to phenylalanine ratio (p<0.001) and higher values of phenylalanine (p<0.05) and tyrosine (p<0.05) were significantly associated with mortality. When divided in three groups, the tertiles discriminated cumulative survival for valine (p = 0.016), phenylalanine (p = 0.024) and in particular for valine to phenylalanine ratio (p = 0.003) and Fischer's ratio (p = 0.005). Parameters were also significantly correlated with MELD and MELD-Na score.

CONCLUSIONS

Amino acids in plasma are valuable biomarkers to determine increased risk of mortality in patients with end-stage liver disease. In particular, valine concentrations and constellations composed of branched-chain and aromatic amino acids were strongly associated with prognosis. Due to their pathophysiological importance, the identified amino acids could be used to examine individual dietary recommendations to serve as potential therapeutic targets.

Malnutrition assessed through phase angle and its relation to prognosis in patients with compensated liver cirrhosis: a prospective cohort study

BACKGROUND

Malnutrition is a frequent complication of cirrhosis and it has been associated to more severe disease and development of complications. Phase angle is a bedside reliable tool for nutritional assessment based on conductivity properties of body tissues.

AIM

To evaluate the association between malnutrition assessed through phase angle and mortality in patients with liver cirrhosis.

METHODS

We performed a prospective cohort study in a tertiary care centre; 249 patients were enrolled with 48 months of follow-up. Clinical, nutritional (malnutrition = phase angle ≤ 4.9°) and biochemical evaluations were performed. Student's t-test and χ(2) method were used as appropriate. Kaplan-Meier curves and multivariate Cox regression were used to evaluate mortality.

RESULTS

Mean follow-up was 33.5 months. Survival analysis showed higher mortality in the malnourished group compared to the well-nourished group (p = 0.076), Kaplan-Meier curves were further stratified according to compensated and decompensated status showing higher mortality in compensated patients according to Child-Pugh (p = 0.002) and Model for End-Stage Liver Disease score (p = 0.008) when malnutrition was present. Multivariate analysis showed that malnutrition was independently associated with mortality (HR = 2.15, 1.18-3.92).

CONCLUSIONS

In our cohort, malnutrition was independently associated with mortality. This is the first study showing higher mortality in malnourished compensated cirrhotic patients.

Branched-chain amino acids in liver diseases

Branched chain amino acids (BCAAs) have been shown to affect gene expression, protein metabolism, apoptosis and regeneration of hepatocytes, and insulin resistance. They have also been shown to inhibit the proliferation of liver cancer cells in vitro, and are essential for lymphocyte proliferation and dendritic cell maturation. In patients with advanced chronic liver disease, BCAA concentrations are low, whereas the concentrations of aromatic amino acids such as phenylalanine and tyrosine are high, conditions that may be closely associated with hepatic encephalopathy and the prognosis of these patients. Based on these basic observations, patients with advanced chronic liver disease have been treated clinically with BCAA-rich medicines, with positive effects.

Effects of oral branched-chain amino acids on hepatic encephalopathy and outcome in patients with liver cirrhosis

Branched-chain amino acids (BCAAs) constituting of valine, leucine, and isoleucine act as both substrates of proteins and as key regulators for various nutrient metabolisms. Patients with liver cirrhosis frequently lack sufficient BCAAs and therefore suffer from various metabolic disorders. Hepatic encephalopathy (HE) is a severe metabolic disorder with neurologic manifestations such as flapping tremors and coma in patients with liver cirrhosis. In addition, a mild form of HE known as minimal HE (MHE) is an important social issue because it occurs in up to 80% of patients with chronic liver disease and affects prognosis and activities of daily living, possibly resulting in falls and motor vehicle accidents. Although HE/MHE can be caused by various pathological conditions, including in an accumulation of mercaptans, short-chain fatty acids, and alterations in the gut flora, hyperammonemia has also been implicated in an important pathogenesis of HE/MHE. Besides urea cycle of liver, ammonia can be detoxified in the skeletal muscles by the amidation process for glutamine synthesis using BCAAs. Thus, BCAA supplementation may enhance detoxification of ammonia in skeletal muscle and may be a possible therapeutic strategy for HE/MHE. In this review, we summarize the clinical impacts of BCAA supplementation on HE/MHE and discuss possible mechanisms for a BCAA-induced improvement of HE/MHE. Furthermore, we present some modifications of oral BCAA therapy for improvement of efficacy in HE treatment. We also briefly describe pleiotropic benefits of BCAAs on life-threatening events and overall prognosis in patients with liver cirrhosis.