Journal of Renal and Hepatic Disorders 2019; 3(1): 40–46 40 REVIEW ARTICLE Wasting Away with Cirrhosis: A Review of Hepatic Sarcopenia Ernesto Robalino Gonzaga1, Austin Andrew2, Freeman Jan George2 1Department of Internal Medicine, University of Central Florida College of Medicine, Orlando, FL, USA 2Hepatology Unit, University Hospitals of Derby and Burton on Trent, Derby, United Kingdom Abstract The complications of decompensated cirrhosis are well documented and include variceal bleeding, fluid retention, and hepatic encephalopathy. A less well recognized complication of cirrhosis is muscle wasting or sarcopenia. It is now recognized to have a significant impact on patient survival, especially in patients who are awaiting liver transplantation. An understanding of the pathophysiology of muscle protein homeostasis has led to several proposed mechanisms of sarcopenia and the potential to reverse muscle loss. This review discusses the potential mechanisms of sarcopenia and highlights the possible future means of reversing sarcopenia. Keywords: sarcopenia; cirrhosis; wasting; end-stage liver disease; muscle Received: 14 June 2019; Accepted after revision: 30 July 2019; Published: 09 September 2019 Author for correspondence: Freeman Jan George, Hepatology Unit, University Hospitals of Derby and Burton on Trent, Derby, DE22 3NE, United Kingdom. Email: j.freeman115@btinternet.com How to cite: Gonzaga ER et al. Wasting away with cirrhosis: a review of Hepatic Sarcopenia. J Ren Hepat Disord. 2019;3(1):40–46. Doi: http://dx.doi.org/10.15586/jrenhep.2019.56 Copyright: Gonzaga ER et al. License: This open access article is licensed under Creative Commons Attribution 4.0 International (CC BY 4.0). http://creativecommons.org/ licenses/by/4.0 Introduction Malnutrition is a common finding in end-stage liver disease (ESLD) (1), leading to a loss of muscle mass and an increase in frailty. The causes of malnutrition include inadequate dietary intake, anorexia, malabsorption, low salt and protein diets offered, and the complications of ESLD such as encephalopa- thy and ascites. ESLD patients with malnutrition have longer hospital stays, increased hepatic complications, and in-hospital mortality (2). Loss of muscle mass, sarcopenia, is not synonymous with malnutrition although they often overlap. Sarcopenia is a common complication of cirrhosis and is fre- quently overlooked. It is defined as a reduction in the skeletal muscle mass and strength. It is often not addressed as  a prognostic factor in ESLD or in patients assessed for liver transplantation. The mechanisms behind the cause of sar- copenia are not fully understood, but it is a complication that adversely affects ESLD patient’s survival and quality of life. The prevalence of sarcopenia is higher than any other compli- cations of ESLD. The mean prevalence is 48% compared to esophageal varices (10–15%), refractory ascites (−10%), or hepatocellular cancer (3, 4). There appears to be some gender and ethnicity factors in the development of sarcopenia, with it being more prevalent in Western societies (5). The prevalence of sarcopenia in cirrhosis is higher than any other gastrointes- tinal disorder, being only 21% in patients with inflammatory bowel disease (4). The aim of this review is to assess the current state of knowledge of the mechanisms of muscle wasting in liver disease, diagnostic issues, and potential therapies. P U B L I C A T I O N S CODON Journal of Renal and Hepatic Disorders mailto:j.freeman115@btinternet.com http://dx.doi.org/10.15586/jrenhep.2019.56 http://creativecommons.org/licenses/by/4.0 http://creativecommons.org/licenses/by/4.0 Hepatic sarcopenia Journal of Renal and Hepatic Disorders 2019; 3(1): 40–46 41 Body Composition and Muscle Physiology In order to assess the loss of muscle mass, it is important to have an understanding of relative body composition and muscle physiology in a healthy individual. The assessment of body composition and of somatic protein stores relies on measuring the different body compartments, that is, water, fat, bone, muscle, and visceral organs. Body composition techniques aid in the diagnosis of protein depletion. Protein levels are usually preserved at the expense of fat utilization as an energy source. The amount of body fat compared to mus- cle volume varies according to the cirrhotic stage. In compen- sated cirrhotics, there is a high amount of body fat. While in decompensated cirrhotics there is a much lower amount of body fat, implying lipolysis occurring in the latter stages of cirrhosis is an alternative energy source (6). The utilization of fat thus spares muscle in the early stages of cirrhosis but as it becomes depleted glycogenesis in the muscle leads to a rapid muscle breakdown leading to sarcopenia. The assess- ment of body composition ranges from simple anthropomet- ric tests such as skin thickness to more complex measures such as bioelectrical impedance. Measuring such composi- tion is essential when evaluating malnutrition and sarcopenia in liver patients. The homeostasis of muscle bulk is tightly regulated requir- ing a balance between muscle protein synthesis and muscle proteolysis. Muscle protein synthesis and muscle satellite cell recruitment are important factors in maintaining muscle bulk. The major pathway regulating protein synthesis is the exercise activation of mammalian target of rapamycin (mTOR). Recent evidence suggests that exercise increases intracellular calcium levels triggering both mTOR and mito- gen-activated protein kinase (MAPK) to stimulate muscle protein formation (7). Other suggested stimuli of muscle pro- tein production include insulin-like growth factor (IGF-1), insulin, leucine, testosterone (8), and interleukin (1). Muscle replacement requires the activation and recruit- ment of muscle satellite cells, the adult stem cell of skeletal muscle located between the sarcolemma and basal lamina within the muscle tissue. When activated they proliferate to expand the population of myoblasts and differentiate into myotubes capable of fusing together to form new myofibers. Muscle protein synthesis and satellite cell recruitment are negatively controlled by the cytokine myostatin. Myostatin belongs to the transforming growth factor beta family. Acting in a paracrine fashion, its action is via a linkage with activ- in(s), which is a type 2 transmembrane receptor leading to a serine threonine kinase phosphorylation of Smad2/3 that in turn transcriptionally regulates target genes responsible for muscle protein synthesis. To maintain muscle homeostasis, myostatin levels are regulated by follistatin, a widely expressed glycoprotein acting as an extracellular ligand trap to regulate the availability of myostatin and activins. Its actions are to increase/activate satellite cell recruitment and inhibit Smad2/3, thereby negating the action of myostatin. In exper- imental models, follistatin infusions increase muscle protein synthesis leading to muscle hypertrophy (9). Muscle breakdown or proteolysis is driven by two path- ways: ubiquitin–proteasome pathway (UPP) and the autoph- agy system. UPP is the major proteolysis pathway. Muscle protein is conjugated with ubiquitin, then degraded by 26S proteasome and removed. UPP can be induced by inactivity, injury, and inflammation driven by tumor necrosis factor (TNF), whereas it can be inhibited by protein kinase B. Autophagy contributes to cell homeostasis removing mis- folded proteins and damaged organelles by the formation of autophagasome, which in turn delivers its contents to lyso- somes for degradation. A factor in controlling autophagy rate is mTOR. Rapamycin has been demonstrated to stimu- late autophagy by inhibiting mTOR. Thus myostatin, which inhibits mTOR, probably increases muscle proteolysis as a consequence of autophagy stimulation. An ongoing trial of leucine-enriched essential amino acid mixture seeks to demonstrate a reduction in autophagia and thus improve hepatic sarcopenia as leucine is a direct stimulant of mTOR (Clinical trials identifier NCT03208868). Potential Mechanisms of Sarcopenia Dysregulated muscle proteostasis in ESLD may result from a number of factors including cirrhosis being a metabolic star- vation disorder, hormonal dysfunction (i.e., reduced testos- terone), defective ureagenesis, alterations in branched chain amino acids, and a chronic inflammatory response to endo- toxemia leading to elevated levels of TNF. This leads to an imbalance between muscle protein synthesis and proteolysis being disrupted in favor of proteolysis. As one may expect, there is marked interplay between the various potential mechanisms of sarcopenia. A considerable amount of research has concentrated on defective ureagenesis leading to elevated levels of ammonia or hyperammonemia. Ammonia is derived from purine, amino acid, and gut bacteria metabo- lism. In the face of a reduction of the number of effective hepatocytes, which are metabolically distressed, as a conse- quence of cirrhosis and portal hypertension leading to porto- caval shunting, ammonia levels are raised in cirrhosis to cytotoxic levels. As the cirrhotic liver is unable to metabolize ammonia, skeletal muscle uptake of ammonia increases where it is converted to glutamine via a glutamate pathway. Within the skeletal muscle, excess ammonia induces transreg- ulation of myostatin by a NF-kappa-mediated mechanism (10). Myostatin is a primary inhibitor of protein synthesis and increases autophagy leading to accelerated sarcopenia. It  is well established that myostatin levels are increased in cirrhosis (11). Gonzaga ER et al. Journal of Renal and Hepatic Disorders 2019; 3(1): 40–46 42 The resultant detoxification of ammonia within the mito- chondria leads to high levels of glutamine in the circulation. This is utilized by other peripheral tissues generating another source of ammonia thus maintaining the need for skeletal muscle to continually metabolize it. The biochemical step to  convert ammonia to glutamate requires the tricarboxylic acid cycle intermediary alpha-ketoglutarate. The constant demand for it eventually leads to its depletion resulting in mitochondrial dysfunction and consequently decreased protein synthesis. In addition, the mitochondria become increasingly leaky generating reactive oxidative species further inducing autophagy and proteolysis (12, 13). Hyperammonemia, and the resultant intracellular amino acid deficiency, further stresses the cell resulting in a reduc- tion of mRNA translation and protein synthesis, which occurs via a eukaryotic initiation factor (eIF2) alpha kinase, general control nondepressed two (GCN2) pathway (12–15). Due to cirrhosis being a state of accelerated starvation, and with the reduction in available branched chain amino acids (BCCA) because of their role in anaplerosis, it has also been suggested that muscle synthesis is restricted as amino acids are diverted to other cells for the synthesis of other crit- ical amino acids such as albumin (16). Reduced cellular amino acid concentrations also activate increased skeletal muscle autophagy in cirrhosis (17). Hormonal disarray may also play a role in sarcopenia. Both testosterone and growth hormone are known to inhibit myostatin expression and signaling (18, 19). In cirrhosis, both are reduced and there- fore may contribute to decreased muscle protein synthesis (20, 21). In addition to being a starvation disorder, cirrhosis is also a state of chronic endotoxemia leading to increased circulat- ing levels of TNF. TNF has been shown to impair muscle synthesis, activate autophagy, and inhibit hormones such as growth hormone and IGF-1 (22–24). Diagnosis of Sarcopenia in Cirrhosis A full dietary survey should be undertaken to address any concomitant malnutrition. Bioelectrical impedance anal- ysis, dual energy X-ray absorptiometry (DEXA), and air dis- placement plethismography reflect indirect measures of muscle mass (25). CT and MRI are now the recommended investigations offering both sensitive and specific measure of adiposity and muscle mass. Measurement of peripheral mus- cle mass is not acceptable due to changes in muscle bulk asso- ciated with activity. Evaluation of psoas and paraspinal muscles using CT at the level of the third lumbar vertebra (L3) is a more reproducible means of sequentially following muscle bulk. The definition of sarcopenia in patients with cirrhosis lacks a consensus regarding adequate cut-off values. Most studies defining sarcopenia use the L3 skeletal mass index cut-off values suggested by Prado (L3 SMI: ≤ 38.5 cm2/m2 for women and ≤ 52.4 cm2/m2 for men) (26). However, both CT and MRI have limited access in routine practice (27). Recently, the use of the combination of body mass index and thigh muscle thickness measured by ultrasound has been shown to be almost as good as CT in assessing cirrhotic sar- copenia and may offer a cheaper more accessible means of diagnosing sarcopenia (28). Potential Treatments of Sarcopenia There are no definitive therapies to reverse cirrhotic sarcope- nia. Attempts at improving muscle mass by means of nutri- tional support, increasing exercise, and correcting hormonal disarray have proved disappointing although reducing ammonia levels and myostatin levels are promising in some studies. General nutritional support The caloric and protein intake in ESLD is usually reduced due to alterations in taste, anorexia, salt restriction, and impaired gut motility leading to a relative malabsorptive state (29). This lack of intake accelerates the state of metabolic starvation in patients. Several studies of enteral and paren- teral feeding have not shown any improvement in muscle mass, nutritional status, nitrogen retention, or survival (30). Only a single study of high energy–high protein supplemen- tation was able to demonstrate significant nitrogen retention. The utilization of a multidisciplinary nutrition support team and patient education appears to benefit quality of life and improve survival (31). The timing of nutritional support appears to be important. Evidence suggests that a late eve- ning snack and an early morning protein supplement are the most likely to stabilize muscle homeostasis (32). The amounts of caloric and protein intake are well documented in the European Association for Study of the Liver (EASL) Clinical Practice guidelines on nutrition in chronic liver disease (33). Exercise Exercise stimulates muscle protein synthesis through the acti- vation of mTOR but whether this pathway in cirrhosis is inhibited by hyperammonemia and elevated myostatin is unknown. There is evidence that hyperammonemia alters muscle function by altering contractile function and increas- ing muscle fatigue in patients with ESLD (34). Exercise gen- erates muscle ammonia, which may negate any potential muscle protein synthesis (35). Despite these theoretical con- siderations, a combination of moderate intensity resistance and endurance exercise may benefit sarcopenia in ESLD (36). A recent study has suggested that a combination of BCAA supplementation and walking exercise improved muscle vol- ume and hand grip strength which if confirmed could be eas- ily implemented (37). Hepatic sarcopenia Journal of Renal and Hepatic Disorders 2019; 3(1): 40–46 43 Branched chain amino acid supplementation In ESLD, it is well established that there is a decrease in BCAA and an increase in aromatic amino acids (AAA) which may contribute to hepatic encephalopathy (HE) (38, 39). The role of BCAA therapy in HE is not established with some trials showing no benefit, while a recent Cochrane review favors benefit (40–42). A further study of BCAA supplementation in HE suggests that minimal HE can be pre- vented and interestingly muscle mass can be recovered (43). BCAA may be of benefit by acting as a substrate for anaple- rosis in the alpha-ketoglutamate, Glutamine–glutamate path- way in muscle, and thereby remove ammonia. A further potential mechanism of BCAA therapy maybe to act as an inhibitor of the amino acid deficiency sensor GCN2 and reverse eIF2 phosphorylation leading to an increase in mus- cle synthesis (44). The specific use of leucine-rich amino acid supplementation stimulates mTOR activation leading to higher rate of protein synthesis via messenger RNAs (mRNA) (45–47). If mTOR signaling is impaired, autophagy is increased in cirrhosis, and it has been shown that this can be reversed by an enriched leucine BCAA supplementation. In addition, the study suggested the reversal of the GNC2/ eIF2 pathway (48). Anabolic Hormones Testosterone, growth hormone, and insulin-like growth fac- tor-1 (IGF-1) are known to influence muscle protein synthe- sis by activating mTOR and suppressing myostatin (49). These anabolic hormones are reduced in cirrhosis (50) but studies have not shown any definitive benefit in cirrhotic sar- copenia. In a rat model of cirrhosis, IGF-1 treatment has been shown a decrease in myostatin and improved nitrogen retention (51, 52). Recently, Nutmeg extract has been demon- strated to increase skeletal muscle mass in the elderly acting via the IGF-1, protein kinase B(AKT), and mTOR pathway inhibiting autophagy (53). Whether this could be applied to ESLD patients with sarcopenia begs further clinical studies. Testosterone trials in reversing sarcopenia have been incon- clusive, although one small study demonstrated improved hand grip (54). A further study of men with cirrhosis was able to show an increase in bone mass and muscle mass, and a reduction in the fat mass (55). Ammonia Lowering Therapy Reducing ammonia levels may potentially reverse sarcopenia. However, sarcopenia continues to be a problem following liver transplantation which should correct the metabolic changes of ESLD (56) It has been suggested that the use of post-transplant immunosuppressant drugs, such as cyclospo- rine A and mTOR inhibitors, may be responsible for the ongoing sarcopenia (3, 57). In a recent animal model of por- tal hypertension, the use of rifaximin and l-orthenine l-aspartate (LOLA) for 4 weeks was seen to restore muscle proteostasis and reverse sarcopenia. The treatment was seen to downregulate the ammonia-induced myostatin produc- tion, reverse autophagy, and partially reverse GCN2/eIF2 pathway activity. As lowering of ammonia is an established therapy for hepatic encephalopathy, long-term clinical stud- ies of such therapy are now indicated (12). Myostatin inhibition Myostatin inhibitors have the potential to promote muscle protein synthesis although no human data are available. Recently, antibodies to myostatin and its precursor pro- myostatin have been shown in rats and non-human primates to inhibit myostatin activity and induce muscle anabolic activity. Similar results in non-human primates have been found with domagrozumab therapy (58, 59). The use of recombinant follistatin-288 has been shown to promote growth of skeletal muscle (9). Prognosis of Sarcopenia The overall rate of mortality in cirrhotic patients is 12.5 in every 100,000 patients (60). With the onset of sarcopenia, there is a threefold increase in mortality compared to cir- rhotic patients without sarcopenia (61). Sarcopenia is an independent prognostic indicator for patients awaiting liver transplantation with estimated survival rates at 1, 2, and 3 years being 63%, 51%, and 51%, respectively, compared to nonsarcopenic patients with survival rates of 79%, 74%, and 70% over a similar period (62). A number of studies have identified sarcopenia to be a prognostic factor in the increased mortality of patients await- ing liver transplantation. In a study of 232 consecutive trans- plant recipients, sarcopenia increased the length of hospital stay, intensive care unit (ICU) stay, and 12-month mortality; 6% of the sarcopenic patients did not survive the 12-month period (63). A meta-analysis comparing patients with sarco- penia and non-sarcopenia demonstrated an increased mor- tality by 3.25% for patients with ESLD and sarcopenia. The sarcopenia patients also had an increased complication rate in post-transplant infections, sepsis, and mechanical ventila- tion periods compared to non-sarcopenia patients who were less likely to experience these complications. The analysis highlights that due to sarcopenia’s significant influence on mortality and complications, it is an important prognostic factor, independent of the current model of end-stage liver disease (MELD) and Child-Turcotte-Pugh (CTP) scores used (4). A large retrospective study of sarcopenia-related ESLD (64) found that paraspinal muscles index (PSMI) seems to be the most reliable diagnostic aid in predicting transplant outcomes. Its use not only predicts death but also estimates associated complications for patients on the transplant Gonzaga ER et al. Journal of Renal and Hepatic Disorders 2019; 3(1): 40–46 44 waiting list. This study supports Kalafateli et al.’s paper, and in that it calculates the improved outcomes of patients per unit of improved muscle mass. The traditional MELD score does not incorporate sarco- penia as a factor of assessment. The evidence above and many other existing studies support that sarcopenia is, in itself, a prognostic indicator of survival for ESLD patients. A  more recent modified version, known as the MELD- sarcopenia score, has been proposed, offering a better prognostic value for patients awaiting or undergoing liver transplant. Therefore, consideration and management of skeletal muscle may improve transplantation outcomes. Conclusion Sarcopenia is a common and significant complication of cir- rhosis. It is a prevalent and important issue to address in patient’s awaiting liver transplant, as sarcopenia greatly increases mortality. There have been multiple hypotheses pro- posed regarding the mechanism(s) underlying sarcopenia in order to determine an effective treatment. This includes defective ureagenesis with ammonia elevation, alterations in BCAA, and chronic inflammatory response with the presence of elevated TNF leading to increased proteolysis. Based on these hypotheses, interventions have been attempted with some promising results, including nutrition support, exercise focused on resistance and endurance, and BCAA supplemen- tation. Targeting ammonia has also shown to have benefits on sarcopenia, especially with the use of rifaximin and LOLA restoring muscle proteostasis, potentially reversing sarcope- nia. Although transplant remains the only curative treat- ment, patients with significant sarcopenia are less likely to survive transplant. Efforts should focus on improving muscle mass and nutrition in these patients prior to surgery. Increasing the awareness of sarcopenia should improve the prognosis and quality of life of patients with ESLD. Conflict of interest The authors declare no potential conflicts of interest with respect to research, authorship, and/or publication of this article. References 1. Tsochatzis E, Bosch J, Burroughs A. Liver cirrhosis. Lancet. 2014;383(9930):1749–61. https://doi.org/10.1016/S0140-6736(14) 60121-5 2. Bernal W, Martin-Mateos R, Lipcsey M, Tallis C, Woodsford K, Mcphail M, et al. Aerobic capacity during cardiopulmonary exercise testing and survival with and without liver transplanta- tion for patients with chronic liver disease. Liver Transplantation. 2013;20(1):54–62. https://doi.org/10.1002/lt.23766 3. Dasarathy S. Consilience in sarcopenia of cirrhosis. J Cachexia Sarcopenia Muscle. 2012;3(4):225–37. https://doi.org/10.1007/ s13539-012-0069-3 4. Kim G, Kang S, Kim M, Baik S. Prognostic value of sarcopenia in patients with liver cirrhosis: A systematic review and meta-analysis. PLoS One. 2017;12(10):e0186990. https://doi. org/10.1371/journal.pone.0186990 5. Benjamin J, Shasthry V, Kaal C, Anand L, Bhardwaj A, Pandit V, et al. Characterization of body composition and definition of sarcopenia in patients with alcoholic cirrhosis: A computed tomography based study. Liver Int. 2017;37(11):1668–74. https://doi.org/10.1111/liv.13509 6. Bryant R, Ooi S, Schultz C, Goess C, Grafton R, Hughes J, et al. Low muscle mass and sarcopenia: Common and predictive of osteopenia in inflammatory bowel disease. Aliment Pharmacol Therapeut. 2015;41(9):895–906. https://doi.org/ 10.1111/apt.13156 7. Ito N, Ruegg U, Takeda S. ATP-induced increase in intracellular calcium levels and subsequent activation of mTOR as regula- tors of skeletal muscle hypertrophy. Int J Mol Sci. 2018;19(9): 2804. https://doi.org/10.3390/ijms19092804 8. Drummond M, Dreyer H, Fry C, Glynn E, Rasmussen B. Nutritional and contractile regulation of human skeletal muscle protein synthesis and mTORC1 signaling. J Appl Physiol. 2009;106(4):1374–84. https://doi.org/10.1152/japplphysiol. 91397.2008 9. Castonguay R, Lachey J, Wallner S, Strand J, Liharska K, Watanabe A, et al. Follistatin-288-Fc fusion protein promotes localized growth of skeletal muscle. J Pharmacol Exp Therapeut. 2018;368(3):435–45. https://doi.org/10.1124/jpet.118.252304 10. Qiu J, Thapaliya S, Runkana A, Yang Y, Tsien C, Mohan M, et al. Hyperammonemia in cirrhosis induces transcriptional reg- ulation of myostatin by an NF- B-mediated mechanism. Proc Natl Acad Sci. 2013;110(45):18162–7. https://doi.org/10.1073/ pnas.1317049110 11. Nishikawa H, Enomoto H, Ishii A, Iwata Y, Miyamoto Y, Ishii N, et al. Elevated serum myostatin level is associated with worse survival in patients with liver cirrhosis. J Cachexia Sarcopenia Muscle. 2017;8(6):915–25. https://doi.org/10.1002/jcsm.12212 12. Kumar A, Davuluri G, Silva R, Engelen M, Ten Have G, Prayson R, et al. Ammonia lowering reverses sarcopenia of cir- rhosis by restoring skeletal muscle proteostasis. Hepatology. 2017;65(6):2045–58. https://doi.org/10.1002/hep.29107 13. Davuluri G, Krokowski D, Guan B, Kumar A, Thapaliya S, Singh D, et al. Metabolic adaptation of skeletal muscle to hyper- ammonemia drives the beneficial effects of l-leucine in cirrhosis. J Hepatol. 2016;65(5):929–37. https://doi.org/10.1016/j.jhep. 2016.06.004 14. Dasarathy S, Hatzoglou M. Hyperammonemia and proteostasis in cirrhosis. Curr Opin Clin Nutr Metab Care. 2018;21(1):30–6. https://doi.org/10.1097/MCO.0000000000000426 15. Anda S, Zach R, Grallert B. Activation of Gcn2 in response to different stresses. PLoS One. 2017;12(8):e0182143.https://doi. org/10.1371/journal.pone.0182143 16. Glass C, Hipskind P, Tsien C, Malin S, Kasumov T, Shah S, et al. Sarcopenia and a physiologically low respiratory quotient in patients with cirrhosis: A prospective controlled study. J Appl Physiol. 2013;114(5):559–65. https://doi.org/10.1152/japplphysiol. 01042.2012 17. Breuillard C, Cynober L, Moinard C. Citrulline and nitrogen homeostasis: An overview. Amino Acids. 2015;47(4):685–91. https://doi.org/10.1007/s00726-015-1932-2 18. Liu W, Thomas S, Asa S, Gonzalez-Cadavid N, Bhasin S, Ezzat S. Myostatin is a skeletal muscle target of growth hormone ana- bolic action. J Clin Endocrinol Metabol. 2003;88(11):5490–6. https://doi.org/10.1210/jc.2003-030497 https://doi.org/10.1002/lt.23766 https://doi.org/10.1007/s13539-012-0069-3 https://doi.org/10.1007/s13539-012-0069-3 https://doi.org/10.1371/journal.pone.0186990 https://doi.org/10.1371/journal.pone.0186990 https://doi.org/10.1111/liv.13509 https://doi.org/10.1111/apt.13156 https://doi.org/10.1111/apt.13156 https://doi.org/10.3390/ijms19092804 https://doi.org/10.1152/japplphysiol.91397.2008 https://doi.org/10.1152/japplphysiol.91397.2008 https://doi.org/10.1124/jpet.118.252304 https://doi.org/10.1073/pnas.1317049110 https://doi.org/10.1073/pnas.1317049110 https://doi.org/10.1002/jcsm.12212 https://doi.org/10.1002/hep.29107 https://doi.org/10.1016/j.jhep.2016.06.004 https://doi.org/10.1016/j.jhep.2016.06.004 https://doi.org/10.1097/MCO.0000000000000426 https://doi.org/10.1371/journal.pone.0182143 https://doi.org/10.1371/journal.pone.0182143 https://doi.org/10.1152/japplphysiol.01042.2012 https://doi.org/10.1152/japplphysiol.01042.2012 https://doi.org/10.1007/s00726-015-1932-2 https://doi.org/10.1210/jc.2003-030497 Hepatic sarcopenia Journal of Renal and Hepatic Disorders 2019; 3(1): 40–46 45 19. Lakshman K, Bhasin S, Corcoran C, Collins-Racie L, Tchistiakova L, Forlow S, et al. Measurement of myostatin con- centrations in human serum: Circulating concentrations in young and older men and effects of testosterone administration. Mol Cell Endocrinol. 2009;302(1):26–32. https://doi.org/ 10.1016/j.mce.2008.12.019 20. Handelsman D, Strasser S, McDonald J, Conway A, McCaughan G. Hypothalamic-pituitary-testicular function in end-stage non-alcoholic liver disease before and after liver transplantation. Clin Endocrinol. 1995;43(3):331–7. https://doi. org/10.1111/j.1365-2265.1995.tb02040.x 21. Dasarathy S, Mullen K, Dodig M, Donofrio B, McCullough A. Inhibition of aromatase improves nutritional status following portacaval anastomosis in male rats. J Hepatol. 2006;45(2): 214–20. https://doi.org/10.1016/j.jhep.2006.02.016 22. Lang C, Frost R, Nairn A, MacLean D, Vary T. TNF-α impairs heart and skeletal muscle protein synthesis by altering transla- tion initiation. Am J Physiol Endocrinol Metabol. 2002;282(2):E336–47. https://doi.org/10.1152/ajpendo.00366. 2001 23. Keller C, Fokken C, Turville S, Lünemann A, Schmidt J, Münz C, et al. TNF-α induces macroautophagy and regulates MHC class ii expression in human skeletal muscle cells. J Biol Chem. 2010;286(5):3970–80. https://doi.org/10.1074/jbc.M110.159392 24. Fernández-Celemín L, Pasko N, Blomart V, Thissen J. Inhibition of muscle insulin-like growth factor I expression by tumor necrosis factor-α. Am J Physiology Endocrinol Metabol. 2002;283(6):E1279–90. https://doi.org/10.1152/ajpendo.00054. 2002 25. Peng S, Plank L, McCall J, Gillanders L, McIlroy K, Gane E. Body composition, muscle function, and energy expenditure in  patients with liver cirrhosis: A comprehensive study. Am J Clin  Nutr. 2007;85(5):1257–66. https://doi.org/10.1093/ajcn/85. 5.1257 26. Prado C, Lieffers J, McCargar L, Reiman T, Sawyer M, Martin L, et al. Prevalence and clinical implications of sarcope- nic obesity in patients with solid tumours of the respiratory and gastrointestinal tracts: A population-based study. Lancet Oncol.  2008;9(7):629–35. https://doi.org/10.1016/S1470-2045 (08)70153-0 27. Andersson K, Salomon J, Goldie S, Chung R. Cost effectiveness of alternative surveillance strategies for hepatocellular carci- noma in patients with cirrhosis. Clin Gastroenterol Hepatol. 2008;6(12):1418–24. https://doi.org/10.1016/j.cgh.2008.08.005 28. Tandon P, Low G, Mourtzakis M, Zenith L, Myers R, Abraldes J, et al. A model to identify sarcopenia in patients with cirrhosis. Clin Gastroenterol Hepatol. 2016;14(10):1473–80.e3. https:// doi.org/10.1016/j.cgh.2016.04.040 29. Dasarathy S. Nutrition and alcoholic liver disease. Clin Liver Dis. 2016;20(3):535–50. https://doi.org/10.1016/j.cld.2016.02.010 30. Plauth M, Bernal W, Dasarathy S, Merli M, Plank L, Schütz T, et al. ESPEN guideline on clinical nutrition in liver disease. Clin Nutr. 2019;38(2):485–521. https://doi.org/10.1016/j.clnu.2018. 12.022 31. Iwasa M, Iwata K, Hara N, Hattori A, Ishidome M, Sekoguchi- Fujikawa N, et al. Nutrition therapy using a multidisciplinary team improves survival rates in patients with liver cirrhosis. Nutrition. 2013;29(11–12):1418–21. https://doi.org/10.1016/j. nut.2013.05.016 32. Rivera Irigoin R, Abilés J. Soporte nutricional en el paciente con cirrosis hepática. Gastroenterología y Hepatología. 2012;35(8):594–601. https://doi.org/10.1016/j.gastrohep.2012. 03.001 33. Merli M, Berzigotti A, Zelber-Sagi S, Dasarathy S, Montagnese S, Genton L, et al. EASL clinical practice guidelines on nutri- tion in chronic liver disease. J Hepatol. 2019;70(1):172–93. https://doi.org/10.1016/j.jhep.2018.06.024 34. McDaniel J, Davuluri G, Hill E, Moyer M, Runkana A, Prayson R, et al. Hyperammonemia results in reduced muscle function independent of muscle mass. Am J Physiol Gastrointest Liver Physiol. 2016;310(3):G163–70. https://doi.org/10.1152/ajpgi. 00322.2015 35. Dietrich R, Bachmann C, Lauterburg B. Exercise-induced hyperammonemia in patients with compensated chronic liver disease. Scand J Gastroenterol. 1990;25(4):329–34. https://doi. org/10.3109/00365529009095494 36. Berzigotti A, Albillos A, Villanueva C, Genescá J, Ardevol A, Augustín S, et al. Effects of an intensive lifestyle intervention program on portal hypertension in patients with cirrhosis and obesity: The SportDiet study. Hepatology. 2017;65(4):1293–305. https://doi.org/10.1002/hep.28992 37. Hiraoka A, Michitaka K, Kiguchi D, Izumoto H, Ueki H, Kaneto M, et al. Efficacy of branched-chain amino acid supple- mentation and walking exercise for preventing sarcopenia in patients with liver cirrhosis. Eur J Gastroenterol Hepatol. 2017;29(12):1416–23. https://doi.org/10.1097/MEG.0000000 000 000986 38. Campollo, O., Sprengers, D., McIntyre, N. The BCAA/AAA ratio of plasma amino acids in three different groups of cirrhot- ics. Rev Invest Clin. 1992; 44(4):513–18. 39. Tajiri K, Shimizu Y. Branched-chain amino acids in liver dis- eases. Transl Gastroenterol Hepatol. 2018;3:47–47. https://doi. org/10.21037/tgh.2018.07.06 40. Gluud L, Dam G, Les I, Marchesini G, Borre M, Aagaard N, et  al. Branched-chain amino acids for people with hepatic encephalopathy. Cochrane Database Syst Rev. 2015;(2): CD001939. https://doi.org/10.1002/14651858.CD001939.pub4 41. Muto Y, Sato S, Watanabe A, Moriwaki H, Suzuki K, Kato A, et al. Effects of oral branched-chain amino acid granules on event-free survival in patients with liver cirrhosis. Clin Gastroenterol Hepatol. 2005;3(7):705–13. https://doi.org/ 10.1016/S1542-3565(05)00017-0 42. Marchesini G, Bianchi G, Merli M, Amodio P, Panella C, Loguercio C, et al. Nutritional supplementation with branched- chain amino acids in advanced cirrhosis: A double-blind, ran- domized trial. Gastroenterology. 2003;124(7):1792–801. https:// doi.org/10.1016/S0016-5085(03)00323-8 43. Les I, Doval E, García-Martínez R, Planas M, Cárdenas G, Gómez P, et al. Effects of branched-chain amino acids supple- mentation in patients with cirrhosis and a previous episode of  hepatic encephalopathy: A randomized study. Am J Gastroenterol. 2011;106(6):1081–8. https://doi.org/10.1038/ ajg.2011.9 44. Zhang P, McGrath B, Reinert J, Olsen D, Lei L, Gill S, et al. The GCN2 eIF2 kinase is required for adaptation to amino acid deprivation in mice. Mol Cell Biol. 2002;22(19):6681–8. https:// doi.org/10.1128/MCB.22.19.6681-6688.2002 45. Anthony J, Yoshizawa F, Anthony T, Vary T, Jefferson L, Kimball S. Leucine stimulates translation initiation in skeletal muscle of postabsorptive rats via a rapamycin-sensitive pathway. J Nutr. 2000;130(10):2413–19. https://doi.org/10.1093/jn/130.10.2413 46. Anthony T, Anthony J, Yoshizawa F, Kimball S, Jefferson L. Oral administration of leucine stimulates ribosomal protein mRNA translation but not global rates of protein synthesis in the liver of rats. J Nutr. 2001;131(4):1171–6. https://doi.org/ 10.1093/jn/131.4.1171 https://doi.org/​10.1016/j.mce.2008.12.019 https://doi.org/​10.1016/j.mce.2008.12.019 https://doi.org/10.1111/j.1365-2265.1995.tb02040.x https://doi.org/10.1111/j.1365-2265.1995.tb02040.x https://doi.org/10.1016/j.jhep.2006.02.016 https://doi.org/10.1152/ajpendo.00366.​2001 https://doi.org/10.1152/ajpendo.00366.​2001 https://doi.org/10.1074/jbc.M110.159392 https://doi.org/10.1152/ajpendo.00054.2002 https://doi.org/10.1152/ajpendo.00054.2002 https://doi.org/10.1093/ajcn/85.5.1257 https://doi.org/10.1093/ajcn/85.5.1257 https://doi.org/10.1016/S1470-2045 (08)70153-0 https://doi.org/10.1016/S1470-2045 (08)70153-0 https://doi.org/10.1016/j.cgh.2008.08.005 https://doi.org/10.1016/j.cgh.2016.04.040 https://doi.org/10.1016/j.cgh.2016.04.040 https://doi.org/10.1016/j.cld.2016.02.010 https://doi.org/10.1016/j.clnu.2018.12.022 https://doi.org/10.1016/j.clnu.2018.12.022 https://doi.org/10.1016/j.nut.2013.05.016 https://doi.org/10.1016/j.nut.2013.05.016 https://doi.org/10.1016/j.gastrohep.2012.03.001 https://doi.org/10.1016/j.gastrohep.2012.03.001 https://doi.org/10.1016/j.jhep.2018.06.024 https://doi.org/10.1152/ajpgi.00322.2015 https://doi.org/10.1152/ajpgi.00322.2015 https://doi.org/10.3109/00365529009095494 https://doi.org/10.3109/00365529009095494 https://doi.org/10.1002/hep.28992 https://doi.org/10.1097/MEG.0000000000000986 https://doi.org/10.1097/MEG.0000000000000986 https://doi.org/10.21037/tgh.2018.07.06 https://doi.org/10.21037/tgh.2018.07.06 https://doi.org/10.1002/14651858.CD001939.pub4 https://doi.org/ 10.1016/S1542-3565(05)00017-0 https://doi.org/ 10.1016/S1542-3565(05)00017-0 https://doi.org/10.1016/S0016-5085(03)00323-8 https://doi.org/10.1016/S0016-5085(03)00323-8 https://doi.org/10.1038/ajg.2011.9 https://doi.org/10.1038/ajg.2011.9 https://doi.org/10.1128/MCB.22.19.6681-6688.2002 https://doi.org/10.1128/MCB.22.19.6681-6688.2002 https://doi.org/10.1093/jn/130.10.2413 https://doi.org/10.1093/jn/131.4.1171 https://doi.org/10.1093/jn/131.4.1171 Gonzaga ER et al. Journal of Renal and Hepatic Disorders 2019; 3(1): 40–46 46 47. Dardevet D, Sornet C, Balage M, Grizard J. Stimulation of in vitro rat muscle protein synthesis by leucine decreases with age. J Nutr. 2000;130(11):2630–5. https://doi.org/10.1093/jn/ 130. 11.2630 48. Tsien C, Davuluri G, Singh D, Allawy A, Ten Have G, Thapaliya S, et al. Metabolic and molecular responses to leucine-enriched branched chain amino acid supplementation in the skeletal muscle of alcoholic cirrhosis. Hepatology. 2015;61(6):2018–29. https://doi.org/10.1002/hep.27717 49. Marcell T, Harman S, Urban R, Metz D, Rodgers B, Blackman M. Comparison of GH, IGF-I, and testosterone with mRNA of receptors and myostatin in skeletal muscle in older men. Am J Physiol Endocrinol Metabol. 2001;281(6):E1159–64. https:// doi.org/10.1152/ajpendo.2001.281.6.E1159 50. Moctezuma-Velázquez C, Low G, Mourtzakis M, Ma M, Burak K, Tandon P, et al. Association between low testosterone levels and sarcopenia in cirrhosis: A cross-sectional study. Ann Hepatol. 2018;17(4):615–23. https://doi.org/10.5604/ 01.3001. 0012.0930 51. Picardi A, de Oliveira A, Muguerza B, Tosar A, Quiroga J, Castilla-Cortázar I, et al. Low doses of insulin-like growth fac- tor-I improve nitrogen retention and food efficiency in rats with early cirrhosis. J Hepatol. 1997;26(1):191–202. https://doi. org/10.1016/S0168-8278(97)80026-8 52. Lang C, Frost R, Svanberg E, Vary T. IGF-I/IGFBP-3 amelio- rates alterations in protein synthesis, eIF4E availability, and  myostatin in alcohol-fed rats. Am J Physiol Endocrinol Metabol. 2004;286(6):E916–26. https://doi.org/10.1152/ajpendo. 00554.2003 53. Pratiwi Y, Lesmana R, Goenawan H, Sylviana N, Setiawan I, Tarawan V, et al. Nutmeg extract increases skeletal muscle mass in aging rats partly via IGF1-AKT-mTOR pathway and inhibi- tion of autophagy. Evid Base Compl Alternative Med. 2018;2018:1–8. https://doi.org/10.1155/2018/2810840 54. Yurci A, Yucesoy M, Unluhizarci K, Torun E, Gursoy S, Baskol M, et al. Effects of testosterone gel treatment in hypogonadal men with liver cirrhosis. Clin Res Hepatol Gastroenterol. 2011;35(12):845–54. https://doi.org/10.1016/j.clinre.2011.09.005 55. Sinclair M, Grossmann M, Hoermann R, Angus P, Gow P. Testosterone therapy increases muscle mass in men with cirrhosis and low testosterone: A randomised controlled trial. J Hepatol. 2016;65(5):906–13. https://doi.org/10.1016/j.jhep. 2016.06.007 56. Tsien C, Garber A, Narayanan A, Shah S, Barnes D, Eghtesad B, et al. Post-liver transplantation sarcopenia in cirrhosis: A prospective evaluation. J Gastroenterol Hepatol. 2014;29(6): 1250–7. https://doi.org/10.1111/jgh.12524 57. Dasarathy S. Posttransplant sarcopenia: An underrecognized early consequence of liver transplantation. Dig Dis Sci. 2013;58(11):3103–11. https://doi.org/10.1007/s10620-013- 2791-x 58. Pirruccello-Straub M, Jackson J, Wawersik S, Webster M, Salta L, Long K, et al. Blocking extracellular activation of myostatin as a strategy for treating muscle wasting. Sci Rep. 2018;8:2292. https://doi.org/10.1038/s41598-018-20524-9 59. St. Andre M, Johnson M, Bansal P, Wellen J, Robertson A, Opsahl A, et al. A mouse anti-myostatin antibody increases muscle mass and improves muscle strength and contractility in the mdx mouse model of Duchenne muscular dystrophy and its humanized equiv- alent, domagrozumab (PF-06252616), increases muscle volume in cynomolgus monkeys. Skeletal Muscle. 2017;7(1):25. https://doi. org/10.1186/s13395-017-0141-y 60. FastStats [Internet]. Cdc.gov. 2019 [cited 2019 Mar 11]. Available from: https://www.cdc.gov/nchs/fastats/liver-disease.htm 61. Kittiskulnam P, Chertow G, Carrero J, Delgado C, Kaysen G, Johansen K. Sarcopenia and its individual criteria are associ- ated, in part, with mortality among patients on hemodialysis. Kidney Int. 2017;92(1):238–47. https://doi.org/10.1016/j.kint. 2017.01.024 62. Tandon P, Ney M, Irwin I, Ma M, Gramlich L, Bain V, et al. Severe muscle depletion in patients on the liver transplant wait list: Its prevalence and independent prognostic value. Liver Transplant. 2012;18(10):1209–16. https://doi.org/10.1002/lt.23495 63. Kalafateli M, Mantzoukis K, Choi Yau Y, Mohammad A, Arora S, Rodrigues S, et al. Malnutrition and sarcopenia predict post-liver transplantation outcomes independently of the Model for end-stage liver disease score. J Cachexia Sarcopenia Muscle. 2016;8(1):113–21. https://doi.org/10.1002/jcsm.12095 64. Engelmann C, Schob S, Nonnenmacher I, Werlich L, Aehling N, Ullrich S, et al. Loss of paraspinal muscle mass is a gen- der-specific consequence of cirrhosis that predicts complica- tions and death. Aliment Pharmacol Therapeut. 2018;48(11–12): 1271–81. https://doi.org/10.1111/apt.15026 https://doi.org/10.1093/jn/130.11.2630 https://doi.org/10.1093/jn/130.11.2630 https://doi.org/10.1002/hep.27717 https://doi.org/10.1152/ajpendo.2001.281.6.E1159 https://doi.org/10.1152/ajpendo.2001.281.6.E1159 https://doi.org/10.5604/01.3001.0012.0930 https://doi.org/10.5604/01.3001.0012.0930 https://doi.org/10.1016/S0168-8278(97)80026-8 https://doi.org/10.1016/S0168-8278(97)80026-8 https://doi.org/10.1152/ajpendo.00554.2003 https://doi.org/10.1152/ajpendo.00554.2003 https://doi.org/10.1155/2018/2810840 https://doi.org/10.1016/j.clinre.2011.09.005 https://doi.org/10.1016/j.jhep.2016.06.007 https://doi.org/10.1016/j.jhep.2016.06.007 https://doi.org/10.1111/jgh.12524 https://doi.org/10.1007/s10620-013-2791-x https://doi.org/10.1038/s41598-018-20524-9 https://doi.org/10.1186/s13395-017-0141-y https://doi.org/10.1186/s13395-017-0141-y http://Cdc.gov https://www.cdc.gov/nchs/fastats/liver-disease.htm https://doi.org/10.1016/j.kint.2017.01.024 https://doi.org/10.1016/j.kint.2017.01.024 https://doi.org/10.1002/lt.23495 https://doi.org/10.1002/jcsm.12095 https://doi.org/10.1111/apt.15026