Skip to main content
Advertisement
Browse Subject Areas
?

Click through the PLOS taxonomy to find articles in your field.

For more information about PLOS Subject Areas, click here.

  • Loading metrics

Effect of dietary branched chain amino acids on liver related mortality: Results from a large cohort of North American patients with advanced HCV infection

  • Lei Yu ,

    Roles Conceptualization, Investigation, Project administration, Supervision, Visualization, Writing – original draft

    leiy@medicine.washington.edu

    Affiliation Division of Gastroenterology, University of Washington, Seattle, Washington, United States of America

  • Shirley C. Paski,

    Roles Conceptualization, Writing – review & editing

    Affiliation Division of Gastroenterology, Cedar Sinai School of Medicine, Los Angeles, California, United States of America

  • Jennifer Dodge,

    Roles Conceptualization, Writing – review & editing

    Affiliation Department of Surgery, Division of Transplant Surgery, University of California San Francisco, San Francisco, California, United States of America

  • Kiran Bambha,

    Roles Conceptualization, Writing – review & editing

    Affiliation Division of Gastroenterology, University of Washington, Seattle, Washington, United States of America

  • Scott W. Biggins,

    Roles Conceptualization, Writing – review & editing

    Affiliation Division of Gastroenterology, University of Washington, Seattle, Washington, United States of America

  • George N. Ioannou

    Roles Conceptualization, Resources, Writing – review & editing

    Affiliations Division of Gastroenterology, University of Washington, Seattle, Washington, United States of America, Veterans Affairs Puget Sound Health Care System, Seattle, Washington, United States of America

Abstract

Branched chain amino acids (BCAA) supplementation may reduce the incidence of liver failure and hepatocellular carcinoma in patients with cirrhosis. We aimed to determine whether long-term dietary intake of BCAA is associated with liver-related mortality in a well-characterized cohort of North American patients with advanced fibrosis or compensated cirrhosis. We performed a retrospective cohort study using extended follow-up data from the Hepatitis C Antiviral Long-term Treatment against Cirrhosis (HALT–C) Trial. The analysis included 656 patients who completed two Food Frequency Questionnaires. The primary exposure was BCAA intake measured in grams (g) per 1000 kilocalories (kcal) of energy intake (range 3.0–34.8 g/1000 kcal). During a median follow-up of 5.0 years, the incidence of liver-related death or transplantation was not significantly different among the four quartiles of BCAA intake before and after adjustment of confounders (AHR 1.02, 95% CI 0.81–1.27, P-value for trend = 0.89). There remains no association when BCAA was modeled as a ratio of BCAA to total protein intake or as absolute BCAA intake. Finally, BCAA intake was not associated with the risk of hepatocellular carcinoma, encephalopathy or clinical hepatic decompensation. We concluded that dietary BCAA intake was not associated with liver-related outcomes in HCV-infected patients with advanced fibrosis or compensated cirrhosis. The precise effect of BCAA in patients with liver disease warrants further study.

Introduction

Leucine, isoleucine and valine, collectively known as the branched chain amino acids (BCAA), have been the subject of intense investigation in liver disease. Compared to normal controls, patients with a wide range of liver disease etiologies and severity have significantly lower plasma concentrations of the BCAA and higher concentrations of the aromatic amino acids (AAA) tyrosine and phenylalanine [1, 2]. This imbalance of plasma amino acids correlated with histological severity and portal systemic shunting [1, 3], but not with serum biochemical parameters or the presence of hepatic encephalopathy [1]. From a therapeutic perspective, the majority of investigations have focused on the effect of BCAA on hepatic encephalopathy. The rationale was proposed by James et al. who theorized that BCAA would compete with AAA for entry into the brain, thereby limiting the formation of “false” neurotransmitters [4]. While most short-term randomized control trials of intravenous BCAA showed benefits in acute episodes of encephalopathy [5], long-term oral formulations in chronic encephalopathy were associated with mixed results [68]. More recently, beneficial effects of BCAA have been expanded to the prevention of liver failure, hepatocellular carcinoma (HCC) and its recurrence following treatment [6, 914]. The most plausible mechanisms include the ability of BCAA, in particular leucine, to stimulate liver regeneration via the production of hepatocyte growth factor and their ability to improve insulin resistance–a key driver in hepatic fibrogenesis and carcinogenesis [1518]. In Japan, BCAA is an approved pharmaconutrient for patients with cirrhosis [19, 20].

Even though BCAA are readily available in the diet, to our knowledge, no study has closely examined dietary BCAA intake in cirrhotic patients and whether the variability in intake affects disease progression. While several of these aforementioned trials attempted to control dietary protein intake [6, 7, 10], none specifically estimated or accounted for dietary BCAA in their analysis. In the current study, we aimed to determine whether long-term intake of BCAA from diet is associated with liver-related mortality in patients with advanced fibrosis or compensated cirrhosis.

Subjects and methods

Study design and ethics statement

We performed a retrospective cohort study using extended long-term follow-up data from the Hepatitis C Antiviral Long-term Treatment against Cirrhosis (HALT-C) Trial (ClinicalTrials.gov #NCT00006164). The trial included HCV-infected patients with histologically defined advanced fibrosis (Ishak fibrosis score 3 or 4) or compensated cirrhosis (Ishak fibrosis score 5 or 6). No patients had a history of Child-Turcotte-Pugh (CTP) score ≥7, bleeding related to esophageal varices, ascites, encephalopathy or HCC at the time of entry into the study. Patients were followed for a median duration of 6 years for clinical decompensation, HCC and death. The data generated by the HALT-C study have been used to evaluate multiple risk factors for liver disease progression in HCV-infected patients [21, 22]. Details on the design, patient population and study outcomes have been published elsewhere [23, 24]. All study subjects provided written informed consent and the study protocol were approved by Institutional Review Boards of all participating centers. The current study analyzed deidentified trial data provided by the National Institutes of Health. The University of Washington Institutional Review Board waived the requirement for informed consent.

Assessment of dietary branched chain amino acids: Leucine, isoleucine and valine

Dietary intake was assessed using the well-validated Block 98.2 Food Frequency Questionnaire (FFQ, Block Data Systems, Berkeley, California), which estimates nutrient intake over the past year based on self-reported frequency and portion of foods [25]. The Block FFQ estimates the amount of specific nutrients primarily based on the United States Department of Agriculture (USDA) Database for Standard Reference, Release 27. These nutrient values were then combined with population and consumption-weighted intake data from NHANES (2007–2010) 24-hour dietary recalls, in order to determine the amount of nutrients found in the food or beverage in the questionnaire response. The average intake of a nutrient from a specific food item is calculated as the product of reported frequency of intake, reported portion size and the estimated nutrient amount from USDA and NHANES. Out of 1,050 patients who participated in the randomized phase of the study, 808 patients completed FFQ at enrollment, 822 patients completed a follow-up FFQ 661±269 days after enrollment and 672 patients completed both FFQs. Because diet may change over time, the average nutrient intake, calculated using multiple assessments, can capture dietary intake more accurately than a single assessment [26]. We therefore defined BCAA intake as the average intake estimated from the baseline and the follow-up FFQ’s calculated as following: (BCAA from baseline FFQ in grams + BCAA from follow-up FFQ in grams)/2.

Study population

Among 672 patients who completed both FFQ’s, we excluded one patient who reported an extremely high caloric intake (more than 2 interquartile ranges from the median). We also excluded 15 patients who underwent transplantation before the second FFQ (N = 2), whose date of completion of the second FFQ was unknown (N = 10), who enrolled greater than 1 year prior to completing the second FFQ (N = 1), and who did not have any follow-up after completing their second FFQ (N = 2), leaving 656 patients in the current analysis.

Outcome definition

The primary outcome of the study is the development of either liver-related death or liver transplantation from the time of the completion of the follow-up FFQ. Secondary outcomes are the development of 1. HCC, 2. hepatic encephalopathy or 3. a composite endpoint of first clinical decompensation including ascites, spontaneous peritonitis, variceal bleeding or encephalopathy. Liver-related death is defined as death from end stage liver disease progression, liver cancer or Peg-interferon treatment induced injury as judged by a 7-person central review committee using the following likelihood categories: “unlikely” or <25% likelihood, “possible” or 25–49% likelihood, “probable” or 50–75% likelihood, and “highly likely” or >75% likelihood. When the likelihood is in the “probable” or “highly likely” categories, the cause of death would be considered as liver-related [24].

Statistical analysis

We used Cox proportional-hazards regression to determine whether total BCAA consumption was associated with liver-related death or transplantation. Since total BCAA intake was positively correlated with total energy intake (Pearson’s correlation: r = 0.771, p < 0.001), quartiles of total BCAA intake were created after dividing BCAA intake by total energy intake, according to the nutrient density model of total energy adjustment [27]. BCAA intake quartiles were modeled in two ways: 1. As a “dummy” categorical variable, where each higher quartile of intake (2nd, 3rd and 4th) was compared to the lowest (1st) quartile; and 2. As an ordinal variable (1 through 4) to yield a “test for trend” where each higher quartile of BCAA intake was compared to the lower quartile. Patients were censored at their last clinic visit. We performed multivariable Cox regression analyses adjusting for the following variables that may influence disease progression in chronic liver diseases: age, gender, race, body mass index (BMI), diabetes, lifetime alcohol consumption, smoking status, self-reported health status (excellent, very good, good, fair and poor), coffee intake (nondrinker, <1, 1–2 and ≥3 cups/day), duration of HCV infection, treatment with low-dose peginterferon, presence of cirrhosis, total energy intake and cholesterol intake. Variables were modeled linearly except for gender, race, diabetes, self-reported health status, low-dose peginterferon treatment group, current smoking status, cirrhosis status and coffee intake. The assumption of proportional hazards was tested and met using weighted residual methods.

We performed sensitivity analyses using two additional methods of capturing BCAA intake as an exposure variable. First, because total BCAA intake was positively correlated with total amino acids (protein) intake (Pearson’s correlation: r = 0.859, p < 0.001), and different amino acids are metabolized differently [28], particularly in advanced cirrhosis [29], we hypothesize that the “ratio” of BCAA to total protein intake may have a different effect on the incidence of liver-related death or liver transplantation. This ratio, “BCAA/total protein,” was first obtained by dividing the average BCAA intake by the average total protein intake. Quartiles of BCAA/Protein intake were then created by dividing “BCAA/total protein” by total energy intake according to the nutrient density model of total energy adjustment as we did above for our primary analysis. Cox regression models included the same variables as the primary analysis. Second, because the true relationship between dietary BCAA and liver disease outcomes may not be affected by total energy intake, we aimed to assess whether the absolute intake of BCAA affected liver-related death or transplantation. Quartiles of absolute BCAA intake were created using the average intake of BCAA from both FFQ’s. In this model, Cox regression models included the same variables as the primary analysis except total energy intake. Sample size was pre-determined by the HALT-C trial. Analyses were performed with SAS version 9.4 (Cary, NC), Stata/IC 14.2 and Stata/SE 11.0 (College Station, TX).

Results

The quartiles of average BCAA intake among 656 patients with advanced fibrosis or compensated cirrhosis were categorized as follows: < 5.6 g/1000 kcal, 5.6−6.4 g/1000 kcal, 6.4−7.4 g/1000 kcal and > 7.4 g/1000 kcal. The median absolute BCAA intake for the quartiles were 9.6 g/day (IQR 6.2−12.6 g/day), 11.7 g/day (IQR 8.2−14.4 g/day), 12.4 g/day (IQR 9.4−16.5 g/day) and 15.7 g/day (IQR 11.2−21.4 g/day), respectively. The median absolute BCAA intake for the entire study cohort was 11.9 g/day (IQR 8.6−16.2 g/day). For the entire cohort, there was no significant change in median BCAA intake estimated from the follow-up FFQ (6.4 g/1000 kcal, IQR 5.4–7.5 g/1000 kcal) compared to that from baseline (6.4 g/1000 kcal, IQR 5.4–7.3 g/1000 kcal). On an individual level, the median difference between BCAA intake estimated from the follow-up and baseline FFQ was only 0.05 g/1000 kcal (IQR -0.9–1.2 g/1000 kcal).

Higher BCAA intake was associated with higher intake of AAA, total protein and cholesterol, but lower intake of carbohydrates, fats and lifetime alcohol. Dietary intake of fiber, vegetables and fruits were not significantly different among the BCAA intake categories (Table 1). In terms of metabolic parameters, higher BCAA intake was associated with higher prevalence of diabetes (Table 2). Higher BCAA intake was not associated with baseline liver enzyme levels or histological scores of inflammation or fibrosis. The proportion of patients with cirrhosis or varices at baseline did not vary significantly among categories of BCAA intake (Table 2).

thumbnail
Table 1. Nutrients intake of 656 patients according to quartiles of average dietary BCAA intake (measured in grams per 1000 kcal of daily energy intake).

https://doi.org/10.1371/journal.pone.0284739.t001

thumbnail
Table 2. Baseline characteristics of 656 patients according to quartiles of average dietary BCAA intake (measured in grams per 1000 kcal of daily energy intake).

https://doi.org/10.1371/journal.pone.0284739.t002

During a median follow-up of 5.0 years, the incidence of liver-related death (N = 45) or transplantation (N = 52) was 31.5 per 1000 person-years. There were 32 non-liver related deaths during the study period. The incidence of all-cause mortality (liver and non-liver related death) or liver transplantation was 41.9 per 100 person-years. The incidence of HCC (N = 53), hepatic encephalopathy (N = 35) and first clinical hepatic decompensation (N = 74) were 17.2, 11.4 and 25.1 per 1000 person-years, respectively. Rates of individual decompensation events such as variceal bleeding, ascites and bacterial peritonitis are presented in S1 Table. Overall, the incidence of liver-related death or transplantation was not significantly different among the quartiles of BCAA intake before or after adjustment of potential confounders (Fig 1 and Table 3, AHR 1.02, 95% CI 0.81−1.27, P-value for trend = 0.89). Crude and adjusted hazard ratios for other confounding variables are presented in S2 Table. The incidence of HCC (AHR 0.89, 95% CI 0.65−1.21, P-value for trend = 0.45) or hepatic encephalopathy (AHR 0.98, 95% CI 0.68−1.42, P-value for trend = 0.93) were also not significantly different among the groups. Similarly, there was no significant association between BCAA intake categories and first clinical hepatic decompensation (variceal bleeding, ascites, peritonitis or encephalopathy). Details of hazard ratio estimates are presented in S3 Table.

thumbnail
Fig 1. Kaplan-Meier survival graph according to quartiles of dietary BCAA intake, censoring occurred when a patient either died from liver-related death or underwent liver transplantation.

https://doi.org/10.1371/journal.pone.0284739.g001

thumbnail
Table 3. Risk of liver-related death or transplantation according to quartiles of average BCAA intake (measured in grams of BCAA per 1000 kcal of daily energy intake).

https://doi.org/10.1371/journal.pone.0284739.t003

Finally, there was no significant association between BCAA intake and liver-related death or transplantation when BCAA intake was modeled in terms of quartiles of BCAA to total protein ratio (with total energy intake adjustment, AHR 1.05, 95% CI 0.72−1.52, P-value for trend = 0.80, S4 Table) or quartiles of absolute BCAA intake (without total energy intake adjustment, AHR 1.04, 95% CI 0.78−1.41, P-value for trend = 0.77, S5 Table).

Discussion

Using carefully collected prospective data from the HALT-C trial, we did not find any association between BCAA intake from dietary sources and liver-related death or transplantation (our primary outcome) or development of HCC or hepatic encephalopthy (our secondary outcomes) in hepatitis C infected patients with advanced fibrosis or compensated cirrhosis.

Our negative finding differs from the majority of published reports [6, 913, 30]. In the literature, the first strong evidence on the benefit of BCAA came from the Italian double-blind randomized trial in which BCAA supplementation of 14.4 g/day for one year was associated with an improvement in overall outcomes in patients with Child-Pugh class B or C cirrhosis. Compared to two control groups who received lactoalbumin or maltodextrin, patients in the BCAA group had lower rates of death and clinical progression, reduced hospital admission rates and length of stay, less cirrhosis-related anorexia and better nutritional parameters [6]. Since then, a second randomized trial from Japan in which Child-Pugh class A cirrhotic patients were also included confirmed a modest benefit of BCAA supplementation of 12 g/day during a two-year study period [10]. Subsequent uncontrolled studies from Japan extended the benefit of BCAA supplementation to the prevention of de novo HCC and its recurrence [9, 1114]. These clinical benefits might reflect results from several in vitro and translational experiments: 1. BCAA, in particular leucine, is able to stimulate hepatocyte growth factor production by hepatic stellate cells, which may facilitate liver regeneration [15], 2. BCAA modifies the structure and improves the function of albumin, which may alleviate oxidative stress associated with advanced cirrhosis [31, 32] and 3. BCAA improves cirrhosis associated insulin resistance by inhibiting insulin mediated anti-apoptosis pathway in liver cancer cells [16, 33].

If BCAA does in fact have a benefit in patients with cirrhosis, two important differences between our study and others may explain our inability to detect it. The first is that the average BCAA exposure in the aforementioned clinical trials among those who received supplementation is substantially higher than even patients in the highest BCAA intake quartile (median intake 15.7 g/day) in our study. Assuming the median intake of BCAA from diet in these trials was similar to that of our study, at 11.9 g/day, supplementing 12 g/day of BCAA would increase one’s total BCAA intake to 24 g/day, or by 100%. In contrast, the difference in median absolute BCAA intake between the highest (15.7 g/day) and the lowest (9.6 g/day) quartile in our study was 6.1 g/day, which was only half of the difference between those who were and were not supplemented in the clinical trials. The lack of benefit observed in our study may be related to the low absolute levels of BCAA intake and the small variance in intake across the quartiles (comparison groups). The second important difference is that all other studies included patients with cirrhosis at varying stages whereas nearly two thirds of patients in our study had histologically confirmed advanced fibrosis without cirrhosis. The median serum albumin across the quartiles of dietary BCAA was 3.9 g/dL, reflecting excellent liver function. Our study may not have sufficient power to detect differences in liver related death, transplantation or HCC which were less common in noncirrhotic patients [24, 34].

As in all observational studies, it is impossible to exclude unmeasured confounding despite our extensive multivariate adjustment. However, several strengths of our study are worth highlighting. First, estimation of BCAA intake was based on a validated FFQ administered twice prior to the onset of clinical events–therefore allowing more accurate capture of long-term intake of BCAA. Multiple asssessments have been shown to reduce measurement errors from recall bias associated with FFQ [26]. Second, we found no associations between liver related outcomes and three different models of dietary BCAA intake which, as we outlined in the Methods, have different biological interpretations. These negative sensitivity analyses suggest that there is unlikely a “missing” association at least in our study population. Finally, the current analysis represents the largest study (N = 656) with the longest follow-up (5.0 years) on the relationship between BCAA and liver disease outcomes, and to our knowledge, the only study that assessed BCAA exposure from diet.

In conclusion, we did not find an association between the level of dietary BCAA intake and liver-related death or transplantation, development of HCC, hepatic encephalopathy or clinical decompensation in a well-characterized cohort of HCV-infected patients. Our result suggests that BCAA at relatively low doses is unlikely to influence liver disease progression in patients with early stage cirrhosis. Whether BCAA supplementation at higher doses can reduce the risk of liver cancer in well-compensated cirrhosis warrants further study.

Trial information

Study data were derived from the extended follow-up data from the Hepatitis C Antiviral Long-term Treatment against Cirrhosis (HALT-C) Trial (ClinicalTrials.gov #NCT00006164).

Supporting information

S1 Table. Rates of liver related decompensations according to quartiles of BCAA intake derived from average daily BCAA intake (measured in grams of BCAA per 1000 kcal of daily energy intake).

https://doi.org/10.1371/journal.pone.0284739.s001

(DOCX)

S2 Table. Crude and adjusted hazard ratios of liver-related death or transplantation according to quartiles of BCAA intake derived from average daily energy adjusted BCAA intake (measured in grams of BCAA per 1000 kcal of daily energy intake).

https://doi.org/10.1371/journal.pone.0284739.s002

(DOCX)

S3 Table. Crude and adjusted hazard ratios of first liver related decompensations (including first event of variceal bleeding, ascites, spontaneous peritonitis or encephalopathy) according to quartiles of BCAA intake derived from average daily BCAA intake (measured in grams of BCAA per 1000 kcal of daily energy intake).

https://doi.org/10.1371/journal.pone.0284739.s003

(DOCX)

S4 Table. Risk of liver-related death or transplantation according to quartiles of average BCAA/total protein/caloric intake (measured in grams BCAA per grams total protein per 1000 kcal).

https://doi.org/10.1371/journal.pone.0284739.s004

(DOCX)

S5 Table. Risk of liver-related death or transplantation according to quartiles of average daily absolute BCAA intake without accounting for total energy intake (measured in grams of BCAA).

https://doi.org/10.1371/journal.pone.0284739.s005

(DOCX)

Acknowledgments

The Hepatitis C Antiviral Long-term Treatment against Cirrhosis (HALT-C) Trial was conducted by the HALT-C Investigators and supported by the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). The data from the HALT-C Trial reported here was supplied by the NIDDK Central Repository. This manuscript does not necessarily reflect the opinions or views of the HALT-C study, the NIDDK Central Repository or the NIDDK.

References

  1. 1. Morgan MY, Milsom JP, Sherlock S. Plasma ratio of valine, leucine and isoleucine to phenylalanine and tyrosine in liver disease. Gut 1978;19:1068–73. pmid:730076
  2. 2. Morgan MY, Marshall AW, Milsom JP, Sherlock S. Plasma amino-acid patterns in liver disease. Gut 1982;23:362–70. pmid:7076013
  3. 3. Iwasaki Y, Sato H, Ohkubo A, Sanjo T, Futagawa S, Sugiura M, et al. Effect of spontaneous portal-systemic shunting on plasma insulin and amino acid concentrations. Gastroenterology 1980;78:677–83. pmid:6986317
  4. 4. James JH, Ziparo V, Jeppsson B, Fischer JE. Hyperammonaemia, plasma aminoacid imbalance, and blood-brain aminoacid transport: a unified theory of portal-systemic encephalopathy. Lancet 1979;2:772–5. pmid:90864
  5. 5. Naylor CD, O’Rourke K, Detsky AS, Baker JP. Parenteral nutrition with branched-chain amino acids in hepatic encephalopathy. A meta-analysis. Gastroenterology 1989;97:1033–42. pmid:2506095
  6. 6. 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, randomized trial. Gastroenterology 2003;124:1792–801. pmid:12806613
  7. 7. Les I, Doval E, Garcia-Martinez R, Planas M, Cardenas G, Gomez P, et al. Effects of branched-chain amino acids supplementation in patients with cirrhosis and a previous episode of hepatic encephalopathy: a randomized study. Am J Gastroenterol 2011;106:1081–8. pmid:21326220
  8. 8. Metcalfe EL, Avenell A, Fraser A. Branched-chain amino acid supplementation in adults with cirrhosis and porto-systemic encephalopathy: systematic review. Clin Nutr 2014;33:958–65. pmid:24656171
  9. 9. Tada T, Kumada T, Toyoda H, Kiriyama S, Tanikawa M, Hisanaga Y, et al. Oral supplementation with branched-chain amino acid granules prevents hepatocarcinogenesis in patients with hepatitis C-related cirrhosis: A propensity score analysis. Hepatol Res 2014;44:288–95. pmid:23607436
  10. 10. 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;3:705–13. pmid:16206505
  11. 11. Kawaguchi T, Shiraishi K, Ito T, Suzuki K, Koreeda C, Ohtake T, et al. Branched-chain amino acids prevent hepatocarcinogenesis and prolong survival of patients with cirrhosis. Clin Gastroenterol Hepatol 2014;12:1012–8 e1. pmid:24036055
  12. 12. Hayaishi S, Chung H, Kudo M, Ishikawa E, Takita M, Ueda T, et al. Oral branched-chain amino acid granules reduce the incidence of hepatocellular carcinoma and improve event-free survival in patients with liver cirrhosis. Dig Dis 2011;29:326–32. pmid:21829025
  13. 13. Tada T, Kumada T, Toyoda H, Kiriyama S, Tanikawa M, Hisanaga Y, et al. Impact of the branched-chain amino acid to tyrosine ratio and branched-chain amino acid granule therapy in patients with hepatocellular carcinoma: A propensity score analysis. J Gastroenterol Hepatol 2015;30:1412–9. pmid:25799910
  14. 14. Nishikawa H, Osaki Y, Iguchi E, Koshikawa Y, Ako S, Inuzuka T, et al. The effect of long-term supplementation with branched-chain amino acid granules in patients with hepatitis C virus-related hepatocellular carcinoma after radiofrequency thermal ablation. J Clin Gastroenterol 2013;47:359–66. pmid:23090049
  15. 15. Tomiya T, Omata M, Fujiwara K. Significance of branched chain amino acids as possible stimulators of hepatocyte growth factor. Biochem Biophys Res Commun 2004;313:411–6. pmid:14684177
  16. 16. Kawaguchi T, Nagao Y, Matsuoka H, Ide T, Sata M. Branched-chain amino acid-enriched supplementation improves insulin resistance in patients with chronic liver disease. Int J Mol Med 2008;22:105–12. pmid:18575782
  17. 17. Muzzi A, Leandro G, Rubbia-Brandt L, James R, Keiser O, Malinverni R, et al. Insulin resistance is associated with liver fibrosis in non-diabetic chronic hepatitis C patients. J Hepatol 2005;42:41–6. pmid:15726693
  18. 18. Hassan MM, Hwang LY, Hatten CJ, Swaim M, Li D, Abbruzzese JL, et al. Risk factors for hepatocellular carcinoma: synergism of alcohol with viral hepatitis and diabetes mellitus. Hepatology 2002;36:1206–13. pmid:12395331
  19. 19. Kawaguchi T, Izumi N, Charlton MR, Sata M. Branched-chain amino acids as pharmacological nutrients in chronic liver disease. Hepatology 2011;54:1063–70. pmid:21563202
  20. 20. Suzuki K, Endo R, Kohgo Y, Ohtake T, Ueno Y, Kato A, et al. Guidelines on nutritional management in Japanese patients with liver cirrhosis from the perspective of preventing hepatocellular carcinoma. Hepatol Res 2012;42:621–6. pmid:22686857
  21. 21. Freedman ND, Everhart JE, Lindsay KL, Ghany MG, Curto TM, Shiffman ML, et al. Coffee intake is associated with lower rates of liver disease progression in chronic hepatitis C. Hepatology 2009;50:1360–9. pmid:19676128
  22. 22. Everhart JE, Lok AS, Kim HY, Morgan TR, Lindsay KL, Chung RT, et al. Weight-related effects on disease progression in the hepatitis C antiviral long-term treatment against cirrhosis trial. Gastroenterology 2009;137:549–57. pmid:19445938
  23. 23. Lee WM, Dienstag JL, Lindsay KL, Lok AS, Bonkovsky HL, Shiffman ML, et al. Evolution of the HALT-C Trial: pegylated interferon as maintenance therapy for chronic hepatitis C in previous interferon nonresponders. Control Clin Trials 2004;25:472–92. pmid:15465617
  24. 24. Di Bisceglie AM, Stoddard AM, Dienstag JL, Shiffman ML, Seeff LB, Bonkovsky HL, et al. Excess mortality in patients with advanced chronic hepatitis C treated with long-term peginterferon. Hepatology 2011;53:1100–8. pmid:21480316
  25. 25. Block G, Thompson FE, Hartman AM, Larkin FA, Guire KE. Comparison of two dietary questionnaires validated against multiple dietary records collected during a 1-year period. J Am Diet Assoc 1992;92:686–93. pmid:1607564
  26. 26. Hu FB, Stampfer MJ, Rimm E, Ascherio A, Rosner BA, Spiegelman D, et al. Dietary fat and coronary heart disease: a comparison of approaches for adjusting for total energy intake and modeling repeated dietary measurements. Am J Epidemiol 1999;149:531–40. pmid:10084242
  27. 27. Willett WC, Howe GR, Kushi LH. Adjustment for total energy intake in epidemiologic studies. Am J Clin Nutr 1997;65:1220S–1228S; discussion 1229S-1231S. pmid:9094926
  28. 28. Goldberg AL, Chang TW. Regulation and significance of amino acid metabolism in skeletal muscle. Fed Proc 1978;37:2301–7. pmid:350636
  29. 29. Tessari P, Zanetti M, Barazzoni R, Biolo G, Orlando R, Vettore M, et al. Response of phenylalanine and leucine kinetics to branched chain-enriched amino acids and insulin in patients with cirrhosis. Gastroenterology 1996;111:127–37. pmid:8698191
  30. 30. Kawamura E, Habu D, Morikawa H, Enomoto M, Kawabe J, Tamori A, et al. A randomized pilot trial of oral branched-chain amino acids in early cirrhosis: validation using prognostic markers for pre-liver transplant status. Liver Transpl 2009;15:790–7. pmid:19562716
  31. 31. Fukushima H, Miwa Y, Shiraki M, Gomi I, Toda K, Kuriyama S, et al. Oral branched-chain amino acid supplementation improves the oxidized/reduced albumin ratio in patients with liver cirrhosis. Hepatol Res 2007;37:765–70. pmid:17573945
  32. 32. Setoyama H, Tanaka M, Nagumo K, Naoe H, Watanabe T, Yoshimaru Y, et al. Oral branched-chain amino acid granules improve structure and function of human serum albumin in cirrhotic patients. J Gastroenterol 2017;52:754–765. pmid:27873095
  33. 33. Hagiwara A, Nishiyama M, Ishizaki S. Branched-chain amino acids prevent insulin-induced hepatic tumor cell proliferation by inducing apoptosis through mTORC1 and mTORC2-dependent mechanisms. J Cell Physiol 2012;227:2097–105. pmid:21769869
  34. 34. Lok AS, Seeff LB, Morgan TR, di Bisceglie AM, Sterling RK, Curto TM, et al. Incidence of hepatocellular carcinoma and associated risk factors in hepatitis C-related advanced liver disease. Gastroenterology 2009;136:138–48. pmid:18848939