Branched chain amino acids in liver disease: fact or fantasy?

Nutritional issues in patients with obesity and cirrhosis

Obesity and metabolic syndrome are considered as responsible for a condition known as the non-alcoholic fatty liver disease that goes from simple accumulation of triglycerides to hepatic inflammation and may progress to cirrhosis. Patients with obesity also have an increased risk of primary liver malignancies and increased body mass index is a predictor of decompensation of liver cirrhosis. Sarcopenic obesity confers a risk of physical impairment and disability that is significantly higher than the risk induced by each of the two conditions alone as it has been shown to be an independent risk factor for chronic liver disease in patients with obesity and a prognostic negative marker for the evolution of liver cirrhosis and the results of liver transplantation. Cirrhotic patients with obesity are at high risk for depletion of various fat-soluble, water-soluble vitamins and trace elements and should be supplemented appropriately. Diet, physical activity and protein intake should be carefully monitored in these fragile patients according to recent recommendations. Bariatric surgery is sporadically used in patients with morbid obesity and cirrhosis also in the setting of liver transplantation. The risk of sarcopenia, micronutrient status, and the recommended supplementation in patients with obesity and cirrhosis are discussed in this review. Furthermore, the indications and contraindications of bariatric surgery-induced weight loss in the cirrhotic patient with obesity are discussed.

Branched-chain amino acids for hepatic encephalopathy

BACKGROUND

Hepatic encephalopathy may be caused by a decreased plasma ratio of branched-chain amino acids (BCAA) to aromatic amino acids. Treatment with BCAA may therefore have a beneficial effect on patients with hepatic encephalopathy.

OBJECTIVES

To evaluate the beneficial and harmful effects of BCAA for patients with hepatic encephalopathy.

SEARCH STRATEGY

We identified trials through The Cochrane Hepato-Biliary Group Controlled Trials Register (September 2002), (Issue 3, 2002), MEDLINE (1966-2002/09) and EMBASE (1980-2002/05), manual searches of bibliographies and journals, authors of trials, and pharmaceutical companies.

SELECTION CRITERIA

Randomised trials comparing BCAA with any kind of control therapy for hepatic encephalopathy were included, regardless of blinding, language, or publication status.

DATA COLLECTION AND ANALYSIS

Trial inclusion and data extraction were made independently by two reviewers. Our primary outcome was improvement of hepatic encephalopathy. Statistical heterogeneity was tested using random effects and fixed effect models. Binary outcomes are reported as risk ratios (RR) based on a random effects model.

MAIN RESULTS

Eleven randomised trials (556 patients) assessing BCAA versus carbohydrates, neomycin/lactulose, or isonitrogenous control were included. The median number of patients in each trial was 55 (range 22 to 75). Follow-up after treatment was reported in four trials (median 17 days (range 6 to 30 days)). Compared to the control regimens, BCAA significantly increased the number of patients improving from hepatic encephalopathy at the end of treatment (risk ratio (RR) 1.31, 95% confidence interval (CI) 1.04 to 1.66, nine trials). We found no evidence of an effect of BCAA on survival (RR 1.06, 95% CI 0.98 to 1.14, eight trials) or adverse events (RR 0.97, 95% CI 0.41 to 2.31, three trials). Sensitivity analyses indicated that methodological quality had significant impact on the results. We found no evidence of an effect of BCAA on improvement of hepatic encephalopathy in trials with adequate generation of the allocation sequence (RR 1.01, 95% CI 0.84 to 1.23, three trials), adequate allocation concealment (RR 1.09, 95% CI 0.89 to 1.33, five trials), or adequate double-blinding (RR 1.20, 95% CI 0.83 to 1.73, three trials).

REVIEWER'S CONCLUSIONS

We did not find convincing evidence that BCAA had a significant beneficial effect on patients with hepatic encephalopathy. The trials performed in this field were small with short follow-up and most had low methodological quality.

Formulation of enteral diets

The number of enteral diets has increased from a handful in the 1970s to over 100 at present. These can be classified as polymeric, chemically defined, disease-specific, and specialized diets, as well as oral dietary supplements. The properties, indications, pros and cons for the use of these diets are outlined in an effort to assist clinicians in their selection.

Branched chain amino acids improve body composition and nitrogen balance in a rat model of extra hepatic biliary atresia

Malnutrition and growth retardation remain a major complication in infants with extrahepatic biliary atresia associated cholestasis. The purpose of this study was to investigate whether oral supplementation with branched chain amino acids (BCAA) can correct malnutrition in a rat model of biliary atresia. Four groups of 15 rats, 30 d old, were used. Group A were shamoperated animals, given a normal laboratory diet (17.5% of caloric intake as proteins). Group B were cholestatic rats (biliary atresia) fed a diet enriched in BCAA (supplement of 8.5%, valine/leucine/isoleucine ratio 1:1:1). Group C were cholestatic mice fed a diet enriched in casein (supplement of 8.5%). Group D were cholestatic mice fed a normal diet. Thirty-two days after surgery, groups were compared for body weight, serum amino acid content, nitrogen balance, muscle mass, and carcass composition. The results showed that the weight of group B, C, and D animals was 85, 81, and 64% of group A (controls). Serum BCAA levels were markedly increased in group B animals. Nitrogen retention was similar in groups B and A, but reduced to 63 and 44% in groups C and D, respectively. Dry weights were similar in group A (39.1% of body weight) and B (37.7%), but reduced to 28.1 and 28.6% of body weight in groups C and D. Body proteins were higher in groups A (13.9%) and B (14.2%) than in group D (9.7%) rats. Mineral content of group B animals was 84% of those of group A, 50% in group C, and 23% in group D rats. It was concluded that an oral supplement of BCAA can correct growth, nitrogen retention, and body composition in experimental biliary atresia. Administration of BCAA supplements to cholestatic infants should be considered.

Assessment of effects of amino acids and branched chain keto acids on leucine oxidation in human lymphocytes

Effects of amino acids and branched chain keto acids on leucine transamination and oxidation were assessed in peripheral human lymphocytes. Isoleucine (80-200 mumol/l) and valine (250-500 mumol/l) diminished transamination and oxidation of leucine up to 25%, glutamine (50-1000 mumol/l) up to 55%. alpha-Ketoisocaproic acid (KIC; 200 mumol/l) augmented the activity state of branched chain keto acid dehydrogenase by 40%. It is concluded that in peripheral human lymphocytes (1) isoleucine, valine and glutamine are physiological inhibitors of leucine catabolism, and (2) leucine can promote its own degradation via KIC.

Enteral nutrition: background, indications and management

Enteral nutrition is only part of the wider field of clinical nutrition in which great advances in both theory and practice have been made over the last decade. We have attempted to summarize what we consider to be the advances that have most relevance to the clinical practice of enteral nutrition. This chapter reviews our present understanding of the processes of digestion and absorption of protein, carbohydrate and fats, and examines how this theoretical understanding can be applied to patients in the clinical situation. A broad classification of the different enteral diets is undertaken, and the reasons for the development of particular diets are discussed. The clinical value of these diets is assessed. The wide variety of indications for enteral (as opposed to parenteral) nutrition are discussed and the specific benefits of enteral nutrition for the patient are highlighted. Techniques of administration of enteral nutrition are reviewed in detail, and the methods by which enteral nutrition should be monitored are outlined. Finally, complications of enteral nutrition are summarized and advice given on how to prevent or treat them.

Future of enteral nutrition

Although there has been agreement that enteral nutrition remains an excellent means of providing nutritional support to malnourished patients with normal or near normal gastrointestinal function, it is clear that areas of controversy do exist, and attention needs to be directed towards these in the future.