Branched-chain amino acids: the best compromise to achieve anabolism?

Research progress on branched-chain amino acid aminotransferases

Branched-chain amino acid aminotransferases, widely present in natural organisms, catalyze bidirectional amino transfer between branched-chain amino acids and branched-chain α-ketoacids in cells. Branched-chain amino acid aminotransferases play an important role in the metabolism of branched-chain amino acids. In this paper, the interspecific evolution and biological characteristics of branched-chain amino acid aminotransferases are introduced, the related research of branched-chain amino acid aminotransferases in animals, plants, microorganisms and humans is summarized and the molecular mechanism of branched-chain amino acid aminotransferase is analyzed. It has been found that branched-chain amino acid metabolism disorders are closely related to various diseases in humans and animals and plants, such as diabetes, cardiovascular diseases, brain diseases, neurological diseases and cancer. In particular, branched-chain amino acid aminotransferases play an important role in the development of various tumors. Branched-chain amino acid aminotransferases have been used as potential targets for various cancers. This article reviews the research on branched-chain amino acid aminotransferases, aiming to provide a reference for clinical research on targeted therapy for various diseases and different cancers.

Review of the endocrine organ-like tumor hypothesis of cancer cachexia in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is one of the most fatal types of solid tumors, associated with a high prevalence of cachexia (~80%). PDAC-derived cachexia (PDAC-CC) is a systemic disease involving the complex interplay between the tumor and multiple organs. The endocrine organ-like tumor (EOLT) hypothesis may explain the systemic crosstalk underlying the deleterious homeostatic shifts that occur in PDAC-CC. Several studies have reported a markedly heterogeneous collection of cachectic mediators, signaling mechanisms, and metabolic pathways, including exocrine pancreatic insufficiency, hormonal disturbance, pro-inflammatory cytokine storm, digestive and tumor-derived factors, and PDAC progression. The complexities of PDAC-CC necessitate a careful review of recent literature summarizing cachectic mediators, corresponding metabolic functions, and the collateral impacts on wasting organs. The EOLT hypothesis suggests that metabolites, genetic instability, and epigenetic changes (microRNAs) are involved in cachexia development. Both tumors and host tissues can secrete multiple cachectic factors (beyond only inflammatory mediators). Some regulatory molecules, metabolites, and microRNAs are tissue-specific, resulting in insufficient energy production to support tumor/cachexia development. Due to these complexities, changes in a single factor can trigger bi-directional feedback circuits that exacerbate PDAC and result in the development of irreversible cachexia. We provide an integrated review based on 267 papers and 20 clinical trials from PubMed and ClinicalTrials.gov database proposed under the EOLT hypothesis that may provide a fundamental understanding of cachexia development and response to current treatments.

The Critical Role of the Branched Chain Amino Acids (BCAAs) Catabolism-Regulating Enzymes, Branched-Chain Aminotransferase (BCAT) and Branched-Chain α-Keto Acid Dehydrogenase (BCKD), in Human Pathophysiology

Branched chain amino acids (BCAAs), leucine, isoleucine and valine, are essential amino acids widely studied for their crucial role in the regulation of protein synthesis mainly through the activation of the mTOR signaling pathway and their emerging recognition as players in the regulation of various physiological and metabolic processes, such as glucose homeostasis. BCAA supplementation is primarily used as a beneficial nutritional intervention in chronic liver and kidney disease as well as in muscle wasting disorders. However, downregulated/upregulated plasma BCAAs and their defective catabolism in various tissues, mainly due to altered enzymatic activity of the first two enzymes in their catabolic pathway, BCAA aminotransferase (BCAT) and branched-chain α-keto acid dehydrogenase (BCKD), have been investigated in many nutritional and disease states. The current review focused on the underlying mechanisms of altered BCAA catabolism and its contribution to the pathogenesis of a numerous pathological conditions such as diabetes, heart failure and cancer. In addition, we summarize findings that indicate that the recovery of the dysregulated BCAA catabolism may be associated with an improved outcome and the prevention of serious disease complications.

Determination of Branched-Chain Amino Acids in Food Supplements and Human Plasma by a CE-MS/MS Method with Enhanced Resolution

In the presented study, a capillary electrophoresis-mass spectrometry method combining high separation efficiency and sensitive detection has been developed and validated, for the first time, to quantify branched chain amino acids (valine, isoleucine, leucine) in commercial food and sport supplement samples and human plasma samples. The separations were performed in a bare fused silica capillary. The background electrolyte was composed of 500 mM formic acid with pH 2.0. The plasma sample pretreatment was realized by simple protein precipitation with acetonitrile. Injection of a short zone of highly basic electrolyte before the sample injection and application of the negative pressure on the separation were accompanied by enhanced resolution of the isobaric amino acids—isoleucine and leucine. The developed method was characterized by favorable validation parameters, such as linearity (r² > 0.99), accuracy and precision, the limit of detection, lower limit of quantification, or robustness. These parameters were more than sufficient for the quantification of branched chain amino acids in various samples. The determined concentrations of branched chain amino acids in food and sports supplements were in very good agreement with the content declared by the manufacturer. The investigated concentrations of branched chain amino acids were in the range 294.68–359.24 µM for valine, 91.76–95.67 µM for isoleucine, and 196.78–251.24 µM for leucine. These concentrations fall within the physiological limits. The developed CE-MS/MS method represents a suitable alternative to traditional approaches used in branched chain amino acid quality control and bioanalysis.

Cancer- and Chemotherapy-Induced Musculoskeletal Degradation

Mobility in advanced cancer patients is a major health care concern and is often lost in advanced metastatic cancers. Erosion of mobility is a major component in determining quality of life but also starts a process of loss of muscle and bone mass that further devastates patients. In addition, treatment options become limited in these advanced cancer patients. Loss of bone and muscle occurs concomitantly. Advanced cancers that are metastatic to bone often lead to bone loss (osteolytic lesions) but may also lead to abnormal deposition of new bone (osteoblastic lesions). However, in both cases there is a disruption to normal bone remodeling and radiologic evidence of bone loss. Many antitumor therapies can also lead to loss of bone in cancer survivors. Bone loss releases cytokines (TGFβ) stored in the mineralized matrix that can act on skeletal muscle and lead to weakness. Likewise, loss of skeletal muscle mass leads to reduced bone mass and quality via mechanical and endocrine signals. Collectively these interactions are termed bone-muscle cross-talk, which has garnered much attention recently as a prime target for musculoskeletal health. Pharmacological approaches as well as nutrition and exercise can improve muscle and bone but have fallen short in the context of advanced cancers and cachexia. This review highlights our current knowledge of these interventions and discusses the difficulties in treating severe musculoskeletal deficits with the emphasis on improving not only bone mass and muscle size but also functional outcomes. © 2019 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.

Weight-Loss Cognitive-Behavioural Treatment and Essential Amino Acid Supplementation in a Patient with Spinal Muscular Atrophy and Obesity

Spinal muscular atrophy is a genetic neuromuscular disease characterised by muscle atrophy, hypotonia, weakness, and progressive paralysis. Usually, these patients display increased fat mass deposition and reductions in fat-free mass and resting energy expenditure—an unfavourable condition that facilitates the development of obesity. However, weight management of these patients remains poorly described. Hence, the aim of this case report was to describe the clinical presentation and weight management of a 31-year-old male patient with spinal muscular atrophy type III, class I obesity, and metabolic syndrome treated for 1 year by means of a personalised multistep cognitive-behavioural treatment for obesity. The treatment produced a weight loss of 7.2 kg (7.1%), which was associated with a marked improvement in both the patient's self-reported general conditions and obesity-related cardiometabolic profile, and no adverse effects in terms of spinal muscular atrophy (i.e., reductions in fat-free mass or resting energy expenditure).

Modulating Metabolism to Improve Cancer-Induced Muscle Wasting

Muscle wasting is one of the main features of cancer cachexia, a multifactorial syndrome frequently occurring in oncologic patients. The onset of cachexia is associated with reduced tolerance and response to antineoplastic treatments, eventually leading to clinical conditions that are not compatible with survival. Among the mechanisms underlying cachexia, protein and energy dysmetabolism play a major role. In this regard, several potential treatments have been proposed, mainly on the basis of promising results obtained in preclinical models. However, at present, no treatment yet reached validation to be used in the clinical practice, although several drugs are currently tested in clinical trials for their ability to improve muscle metabolism in cancer patients. Along this line, the results obtained in both experimental and clinical studies clearly show that cachexia can be effectively approached by a multidirectional strategy targeting nutrition, inflammation, catabolism, and inactivity at the same time. In the present study, approaches aimed to modulate muscle metabolism in cachexia will be reviewed.

Cancer-induced muscle wasting: latest findings in prevention and treatment

Cancer cachexia is a severe and disabling clinical condition that frequently accompanies the development of many types of cancer. Muscle wasting is the hallmark of cancer cachexia and is associated with serious clinical consequences such as physical impairment, poor quality of life, reduced tolerance to treatments and shorter survival. Cancer cachexia may evolve through different stages of clinical relevance, namely pre-cachexia, cachexia and refractory cachexia. Given its detrimental clinical consequences, it appears mandatory to prevent and/or delay the progression of cancer cachexia to its refractory stage by implementing the early recognition and treatment of the nutritional and metabolic alterations occurring during cancer. Research on the molecular mechanisms underlying muscle wasting during cancer cachexia has expanded in the last few years, allowing the identification of several potential therapeutic targets and the development of many promising drugs. Several of these agents have already reached the clinical evaluation, but it is becoming increasingly evident that a single therapy may not be completely successful in the treatment of cancer-related muscle wasting, given its multifactorial and complex pathogenesis. This suggests that early and structured multimodal interventions (including targeted nutritional supplementation, physical exercise and pharmacological interventions) are necessary to prevent and/or treat the devastating consequences of this cancer comorbidity, and future research should focus on this approach.

Simultaneous Infusion of Glutamine and Branched-Chain Amino Acids (BCAA) to Septic Rats Does Not Have More Favorable Effect on Protein Synthesis in Muscle, Liver, and Small Intestine Than Separate Infusions

BACKGROUND

Glutamine and branched-chain amino acids (BCAA; valine, leucine, and isoleucine) are used as nutrition supplements in the treatment of proteocatabolic illness. We hypothesized that simultaneous administration of BCAA and glutamine affects protein metabolism more significantly than separate administration. In the present study, we evaluated their effect on protein synthesis in skeletal muscle, liver, and jejunum of septic rats.

METHODS

Twenty-four hours after induction of sepsis by subcutaneous injection of turpentine, the rats were infused for 6 hours with 5 mL of 1.75% glutamine, 1.75% BCAA, 1.75% glutamine+BCAA, or saline solution. The control group consisted of intact rats infused with saline. Protein synthesis was measured at the end of infusion by a "flooding method" with [3,4,5-(3)H]phenylalanine.

RESULTS

In turpentine-treated animals, we observed a decrease in glutamine concentration in blood plasma and skeletal muscle, a decrease in BCAA concentration in liver and jejunum, and a decrease in protein synthesis in all tissues. Glutamine or glutamine+BCAA infusion increased glutamine concentration in plasma and muscle and stimulated protein synthesis in the liver. The BCAA infusion enhanced concentrations of BCAA in plasma and tissues, but the effect of BCAA on protein synthesis was insignificant. Synergistic effect of simultaneous infusion of glutamine and BCAA on protein synthesis was not observed.

CONCLUSIONS

We conclude that glutamine infusion to rats with septic injury may significantly improve impaired protein synthesis in the liver and that there is no synergistic effect of glutamine and BCAA infusion on protein synthesis in skeletal muscle, liver, and jejunum.

Branched-chain amino acid supplementation in adults with cirrhosis and porto-systemic encephalopathy: systematic review

BACKGROUND & AIMS

Branched-chain amino acid supplementation in porto-systemic encephalopathy remains controversial. Here, we examined the systematic review evidence for their effect on encephalopathy, hepatic decompensation, survival, infection, hospital stay and quality of life, and review data on adherence, side-effects and cost/economic evaluation.

METHODS

Four electronic databases were searched from 1980 to June 2011, with an update search in two databases in July 2013. Hand-searching was performed of references lists from included trials and six conference proceedings from 2005 to 2010. We included randomised controlled trials of branched chain amino acids versus other nutritional supplements in adults with cirrhosis and porto-systemic encephalopathy. Data extraction and quality assessment were performed by two independent assessors. Meta-analysis was performed if data were sufficient.

RESULTS

The search identified nine randomised controlled trials (436 patients in total) of branched-chain amino acid therapy for ≥2 weeks' duration. The overall quality of trials was poor. At meta-analysis, a significant improvement in the grade of encephalopathy was demonstrated in favour of branched-chain amino acids compared to other nutritional supplements (Risk Ratio 2.6, 95% Confidence Interval 1.7-3.9, p < 0.001, 2 trials, n 122) but no significant difference was found for either resolution or worsening of encephalopathy, gastrointestinal bleeding, survival or infection. Limited data suggested no difference in health-related quality of life, ascites or admission to hospital. Studies did not include cost data or economic evaluations. Side-effects appeared mild and gastrointestinal in nature.

CONCLUSIONS

Branched-chain amino acids might improve porto-systemic encephalopathy but more robust trials are needed to determine their role.

The role of micronutrients and macronutrients in patients hospitalized for heart failure

The detrimental pathophysiology of heart failure (HF) leaves room for physiologic and metabolomic concepts that include supplementation of micronutrients and macronutrients in these patients. Hence myocardial energetics and nutrient metabolism may represent relevant treatment targets in HF. This review focuses on the role of nutritive compounds such as lipids, amino acids, antioxidants, and other trace elements in the setting of HF. Supplementation of ferric carboxymaltose improves iron status, functional capacity, and quality of life in HF patients. To close the current gap in evidence further interventional studies investigating the role of micro- and macronutrients are needed in this setting.

Leucine supplementation modulates fuel substrates utilization and glucose metabolism in previously obese mice

OBJECTIVE

High-protein diets favor weight loss and its maintenance. Whether these effects might be recapitulated by certain amino acids is unknown. Therefore, the impact of leucine supplementation on energy balance and associated metabolic changes in diet-induced obese (DIO) mice during and after weight loss was investigated.

METHODS

DIO C57BL/6J mice were fed a normocaloric diet to induce weight loss while receiving or not the amino acid leucine in drinking water. Body weight, food intake, body composition, energy expenditure, glucose tolerance, insulin, and leptin sensitivity were evaluated. Q-PCR analysis was performed on muscle, brown and white adipose tissues.

RESULTS

DIO mice decreased body weight and fat mass in response to chow, but supplementation with leucine did not affect these parameters. During weight maintenance, mice supplemented with leucine had improved glucose tolerance, increased leptin sensitivity, and lower respiratory quotient. The latter was associated with changes in the expression of several genes modulating fatty acid metabolism and mitochondrial activity in the epididymal white and the brown adipose tissues, but not muscle.

CONCLUSIONS

Leucine supplementation might represent an adjuvant beneficial nutritional therapy during weight loss and maintenance, because it improves lipid and glucose metabolism and restores leptin sensitivity in previously obese animals.

Clinical and seasonal variations of nutritional risk screening in patients scheduled for rehabilitation after heart surgery

BACKGROUND

Current knowledge on the pervasiveness of increased nutritional risk in cardiovascular diseases is limited. Our aim was to analyze the characteristics of nutritional risk screening in patients scheduled for rehabilitation after heart surgery. Prevalence and extent of nutritional risk were studied in connection with patients' characteristics and seasonal climate effects on weight loss dynamics.

METHODS

The cohort included 65 consecutive patients with an age range of 25-84 years, 2-6 months after surgical treatment for ischemic or valvular heart disease. Nutritional risk screening was appraised using a standardized NRS-2002 questionnaire. Groups were analyzed according to a timeline of rehabilitation according to the "cold" and "warm" seasons of the moderate Mediterranean climate in Opatija, Croatia.

RESULTS

Increased nutritional risk scores (NRS-2002) of >3 were found in 96% of studied patients. Mean NRS-2002 of patients was 5.0 ± 1.0, with a percentage weight loss history of 11.7% ± 2.2% (4.6-19.0). Risk was found to be more pronounced during the warmer season, with NRS-2002 scores of 5.3 ± 0.7 versus 4.8 ± 1.1 (P = 0.136) and greater loss of weight of 13.0% ± 3.2% versus 10.6% ± 3% (P = 0.005), respectively. Increased nutritional risk correlated significantly with creatinine concentrations (rho = 0.359; P = 0.034 versus 0.584; P = 0.001, respectively). Significant discordance in correlations was found between NRS-2002 and the decrease in left ventricle systolic function (rho correlation coefficient [rho-cc] = -0.428; P = 0.009), the increase in glucose concentrations (cc = 0.600; P < 0.001), and the decrease in erythrocyte counts (cc = -0.520; P = 0.001) during the colder season.

CONCLUSION

Increased nutritional risk was found to be frequently expressed in the course of rehabilitation after heart surgery. Although seasonal climate effects influenced the weight loss dynamics, the impact on reproducibility of NRS-2002 was clinically less important. Further studies on the connection of nutritional risk with composited end points might offer improvements in overall quality of treatment.

An interprofessional palliative care oncology rehabilitation program: effects on function and predictors of program completion

BACKGROUND

After treatment, patients with active cancer face a considerable burden from the effects of both the disease and its treatment. The Palliative Rehabilitation Program (prp) is designed to ameliorate disease effects and to improve the patient's functioning. The present study evaluated predictors of program completion and changes in functioning, symptoms, and well-being after the program.

METHODS

The program received referrals for 173 patients who had finished anticancer therapy. Of those 173 patients, 116 with advanced cancer were eligible and enrolled in the 8-week interprofessional prp; 67 completed it. Measures of physical, nutritional, social, and psychological functioning were evaluated at entry to the program and at completion.

RESULTS

Participants experienced significant improvements in physical performance (p < 0.000), nutrition (p = 0.001), symptom severity (p = 0.005 to 0.001), symptom interference with functioning (p = 0.003 to 0.001), fatigue (p = 0.001), and physical endurance, mobility, and balance or function (p = 0.001 to 0.001). Reasons that participants did not complete the prp were disease progression, geographic inaccessibility, being too well (program not challenging enough), death, and personal or unknown reasons. A normal level of C-reactive protein (<10 mg/L, p = 0.029) was a predictor of program completion.

CONCLUSIONS

Patients living with advanced cancers who underwent the interprofessional prp experienced significant improvement in functioning across several domains. Program completion can be predicted by a normal level of C-reactive protein.

The complex role of branched chain amino acids in diabetes and cancer

The obesity and diabetes epidemics are continuing to spread across the globe. There is increasing evidence that diabetes leads to a significantly higher risk for certain types of cancer. Both diabetes and cancer are characterized by severe metabolic perturbations and the branched chain amino acids (BCAAs) appear to play a significant role in both of these diseases. These essential amino acids participate in a wide variety of metabolic pathways, but it is now recognized that they are also critical regulators of a number of cell signaling pathways. An elevation in branched chain amino acids has recently been shown to be significantly correlated with insulin resistance and the future development of diabetes. In cancer, the normal demands for BCAAs are complicated by the conflicting needs of the tumor and the host. The severe muscle wasting syndrome experience by many cancer patients, known as cachexia, has motivated the use of BCAA supplementation. The desired improvement in muscle mass must be balanced by the need to avoid providing materials for tumor proliferation. A better understanding of the complex functions of BCAAs could lead to their use as biomarkers of the progression of certain cancers in diabetic patients.

Heart surgery stems increased nutritional risk, expressed during the course of stationary rehabilitation

BACKGROUND

Cardiovascular diseases are a vast global health burden. Despite common prevalence, current knowledge and investigations concerning nutritional aspects are limited. Characteristics and dynamics of nutritional risk are not entirely known for most of the entities, disease stages or treatment-induced fluctuations. This study assessed the effects of heart surgery on unintentional weight loss and nutritional risk using the NRS-2002.

METHODS

A noninterventional study that included patients scheduled for rehabilitation 1-6 months after heart surgery was performed. Evaluation included routine cardiovascular diagnostics and review of medical histories. Documented baseline weight was available for >85% of the patients. Nutritional risk screening was performed with the standardized NRS-2002 questionnaire.

RESULTS

A total of 145 patients were involved, with a mean age of 65.3 ± 11.5 years in a range of 23-84 years. The male to female ratio was 121:24 (83.4%:16.6%), respectively. Coronary artery bypass graft surgery (CABG) was performed in 89 patients (61.4%), valvular surgery (VS) in 34 (23.4%) and combined operations (CABG + VS) in 22 (15.2%). Percentage weight loss history was 11.1 ± 3.4% in a range of 0-20.1%, while NRS-2002 was 4.77 ± 1.05 in a range of 1-6. Increased nutritional risk (NRS-2002 ≥3) was found in nearly all patients. Combined ischemic and valvular etiology displayed the highest values of NRS-2002 (5.0 ± 1.2). Patient age and creatinine showed significant correlations with NRS-2002 (Rho = 0.521, p < 0.001 and Rho = 0.335, p < 0.001, respectively).

CONCLUSION

Increased nutritional risk was found to be frequently prevalent in patients scheduled for rehabilitation after heart surgery. Risk was found to be in relation with underlying coronary artery disease as well as with the age of patients and parameters of renal function. Routine application of nutritional risk screening appears to be a valuable clinical tool for detecting this relevant comorbidity, particularly since no connection was found with traditional anthropometrics.

Effects of a new mixture of essential amino acids (Aminotrofic(®)) in malnourished haemodialysis patients

The aim of this study was to verify the clinical efficacy of a diet associated with already commercially available oral amino acid functional cluster (AFC) compared to the administration of a diet associated with a nitrogen protein-based supplement (casein) in antagonizing malnutrition in patients with Chronic renal failure (CRF) undergoing haemodialysis. The secondary aim was to assess the changes in protein levels during the acute phase such as the expression of inflammatory cytokines. Twenty patients in haemodialysis aged between 18 and 85 of both genders (13 m, 7f) were recruited, randomized and divided into two groups and treated for 4 months respectively with: (1) oral AFC supplement (*)8 g/die: group A, and (2) oral supplementation of a protein nitrogenous mixture compared to AFC with a casein protein source) of 6.6 g: group P. During the initial assessment and thereafter on a monthly basis all patients underwent the following: Dietary recall 24 h; Anthropometric: Weight, height, BMI, expected dry weight, actual weight; Biochemical: Albumin, transferrin, Na, K, Cl, Ca, P, Mg, long-interval creatinine (Aminotrofic(®): Errekappa Euroterapici, Milano) pre-albumin, α1 acid glycoprotein, C reactive protein (CRP), protein nitrogen appearance (PNA); Instrumental: Handgrip strength evaluation, Calorimetry by means of Armband, Bio-impedance analysis (BIA), Spitzer Index (quality of life), Subjective Global Assessment Generated by the patient (PG SGA). Considering the nutritional parameters, no significant differences concerning dry weight emerged between the beginning (T0) and the end (T4) (weight A to T0: kg 64.41 ± 6.34; weight A to T4: kg 64.51 ± 7.05: P = NS; weight P to T0: kg 60.17 ± 11.94; weight P to T4: kg 59.86 ± 11.43: P = NS); biochemical parameters, significant differences were observed only for two parameters: pre-albumin (Pre-albumin A to T0 30.12 ± 7.23; Pre-albumin A to T4: 28.91 ± 5.8; Pre-albumin P to T0 22.51 ± 6.04; Pre-albumin P to T4: 26.10 ± 9.82), and Transferrin (Transferrin A to T0 171.77 ± 28.87 mg/dL, Transferrin A to T4: 181.44 ± 38.83 mg/dL: P < 0.005; Transferrin P to T0 160.29 ± 27.46 mg/dL, Transferrin P to T4: 146.57 ± 24.96 mg/dL: P < 0.005), but not in other parameters. From a nutritional perspective, after 4 months of treatment an increase in protein synthesis was noted in group A compared to group P which was proved by the significant increase of transferrin. This pilot study suggests the AFC oral supplementation may represent a valid alternative to intradialytic parenteral treatment and may also allow for an improvement in blood chemical values and nutritional status.

Current pharmacotherapy options for cancer anorexia and cachexia

INTRODUCTION

Anorexia and cachexia syndrome represents a complex clinical picture that occurs in the late stage of several chronic inflammatory diseases, including cancer. Unless counteracted cancer-related anorexia and cachexia syndrome affects quality of life (QL) and survival. However, to date a standard effective treatment is lacking.

AREAS COVERED

The aim of this review is to describe the current pharmacological approaches for anorexia and cachexia syndrome, focusing on cancer-related syndrome. The several pharmacological agents tested so far are discussed, distinguishing them in unproven drugs, effective drugs, and drugs under investigation. Moreover, a section is devoted to the promising use of nutritional supplements and nutraceuticals. The emerging role of a multitargeted combined treatment approach is exhaustively reviewed.

EXPERT OPINION

Considering the complex clinical picture and the multifactorial pathogenesis of anorexia and cachexia syndrome, we believe that its clinical management requires a multidisciplinary and multipharmacological approach. In our opinion the anorexia and cachexia syndrome treatment should include drugs that target the following conditions: inflammatory status, oxidative stress, nutritional disorders, muscle catabolism, anemia, immunosuppression, and fatigue. The multidimensional therapies for anorexia and cachexia syndrome should ideally be introduced within a context of the "best supportive care," which includes optimal symptom management and careful psychosocial counseling.

Coupling nutrient sensing to metabolic homoeostasis: the role of the mammalian target of rapamycin complex 1 pathway

The mammalian target of rapamycin complex 1 (mTORC1) pathway is known to couple different environmental cues to the regulation of several energy-demanding functions within the cell, spanning from protein translation to mitochondrial activity. As a result, at the organism level, mTORC1 activity affects energy balance and general metabolic homoeostasis by modulating both the activity of neuronal populations that play key roles in the control of food intake and body weight, as well as by determining storage and use of fuel substrates in peripheral tissues. This review focuses on recent advances made in understanding the role of the mTORC1 pathway in the regulation of energy balance. More particularly, it aims at providing an overview of the status of knowledge regarding the mechanisms underlying the ability of certain amino acids, glucose and fatty acids, to affect mTORC1 activity and in turn illustrates how the mTORC1 pathway couples nutrient sensing to the hypothalamic regulation of the organisms' energy homoeostasis and to the control of intracellular metabolic processes, such as glucose uptake, protein and lipid biosynthesis. The evidence reviewed pinpoints the mTORC1 pathway as an integrator of the actions of nutrients on metabolic health and provides insight into the relevance of this intracellular pathway as a potential target for the therapy of metabolic diseases such as obesity and type-2 diabetes.

Effect of central and peripheral leucine on energy metabolism in the Djungarian hamster (Phodopus sungorus)

Branched-chain amino acids, particularly leucine, are thought to activate nutrient sensing pathways in the hypothalamus that regulate food intake and energy homeostasis. In the light of recent controversial findings of leucine's effect on energy homeostasis further clarification of the metabolic impact of dietary leucine supplementation is required. We examined the pharmacological and dietary effects of leucine on energy metabolism in the Djungarian hamster (Phodopus sungorus), a well-established model for studies of alterations in leptin sensitivity and energy metabolism. We acutely administered leucine into the lateral ventricle (1.1 μg) of hamsters to characterize whether leucine exhibits anorexigenic properties in this species as has been described in other rodents. Next the catabolic effect of dietary administered leucine via supplemented rodent diet (15 % leucine), drinking water (17 g/L leucine) and oral gavages (10 mg/day); as well as the effect of subcutaneously (0.1 and 3 mg/day) and intraperitoneally (0.1, 3 and 6 mg/day) injected leucine which avoids the gastrointestinal-track was analyzed. Centrally administered leucine reduced 24 h food intake (by 32 %) and body weight. Both parameters were also reduced in hamsters with leucine supplemented diet, but this catabolic response was based on a pronounced taste aversion to the leucine-diet. In all other experiments, dietary leucine and peripheral injections of leucine had no effect on food intake, body weight and basal blood glucose levels. Our data suggest that in the Djungarian hamster dietary leucine fails to exhibit catabolic effects that would override the evolutionary conserved adaptations of the species which is critical for its survival.

Differential effect of long-term leucine supplementation on skeletal muscle and adipose tissue in old rats: an insulin signaling pathway approach

Leucine acts as a signal nutrient in promoting protein synthesis in skeletal muscle and adipose tissue via mTOR pathway activation, and may be of interest in age-related sarcopenia. However, hyper-activation of mTOR/S6K1 has been suggested to inhibit the first steps of insulin signaling and finally promote insulin resistance. The impact of long-term dietary leucine supplementation on insulin signaling and sensitivity was investigated in old rats (18 months old) fed a 15% protein diet supplemented (LEU group) or not (C group) with 4.5% leucine for 6 months. The resulting effects on muscle and fat were examined. mTOR/S6K1 signaling pathway was not significantly altered in muscle from old rats subjected to long-term dietary leucine excess, whereas it was increased in adipose tissue. Overall glucose tolerance was not changed but insulin-stimulated glucose transport was improved in muscles from leucine-supplemented rats related to improvement in Akt expression and phosphorylation in response to food intake. No change in skeletal muscle mass was observed, whereas perirenal adipose tissue mass accumulated (+45%) in leucine-supplemented rats. A prolonged leucine supplementation in old rats differently modulates mTOR/S6K pathways in muscle and adipose tissue. It does not increase muscle mass but seems to promote hypertrophy and hyperplasia of adipose tissue that did not result in insulin resistance.

Treatment of cachexia in oncology

Cachexia is a complex metabolic syndrome associated with many chronic or end-stage diseases, especially cancer, and is characterized by loss of muscle with or without loss of fat mass. The management of cachexia is a complex challenge that should address the different causes underlying this clinical event with an integrated or multimodal treatment approach targeting the different factors involved in its pathophysiology. The purpose of this article was to review the current medical treatment of cancer-related cachexia, in particular focusing on combination therapy and ongoing research. Among the treatments proposed in the literature for cancer-related cachexia, some proved to be ineffective, namely, cyproheptadine, hydrazine, metoclopramide, and pentoxifylline. Among effective treatments, progestagens are currently considered the best available treatment option for cancer-related cachexia, and they are the only drugs approved in Europe. Drugs with a strong rationale that have failed or have not shown univocal results in clinical trials so far include eicosapentaenoic acid, cannabinoids, bortezomib, and anti-TNF-alpha MoAb. Several emerging drugs have shown promising results but are still under clinical investigation (thalidomide, selective cox-2 inhibitors, ghrelin mimetics, insulin, oxandrolone, and olanzapine). To date, despite several years of coordinated efforts in basic and clinical research, practice guidelines for the prevention and treatment of cancer-related muscle wasting are lacking, mainly because of the multifactorial pathogenesis of the syndrome. From all the data presented, one can speculate that one single therapy may not be completely successful in the treatment of cachexia. From this point of view, treatments involving different combinations are more likely to be successful.

Nutritional supplements in the surgical patient

This article presents an overview of the current knowledge, status, and use of supplements by patients before surgical operations, together with the benefits expected of the supplements by the patients. The indications, potential advantages and disadvantages, and the relationships with various aspects of the preoperative preparation and postoperative management of surgical patients are discussed, with emphasis on the significant percentage of this population that is deficient in fundamental nutrients. Recent revisions and recommendations for some of the macronutrients are presented, together with a summary of federal regulations and an oversight of supplements.

Nutritional recommendations for the management of sarcopenia

The Society for Sarcopenia, Cachexia, and Wasting Disease convened an expert panel to develop nutritional recommendations for prevention and management of sarcopenia. Exercise (both resistance and aerobic) in combination with adequate protein and energy intake is the key component of the prevention and management of sarcopenia. Adequate protein supplementation alone only slows loss of muscle mass. Adequate protein intake (leucine-enriched balanced amino acids and possibly creatine) may enhance muscle strength. Low 25(OH) vitamin D levels require vitamin D replacement.

Pathogenesis of muscle wasting in cancer cachexia: targeted anabolic and anticatabolic therapies

PURPOSE OF REVIEW

Cancer-related muscle loss, or cachexia, is the cause of death for approximately 2 million people worldwide and severely reduces quality of life. The degree of cachexia is inversely correlated with survival time; however, the exact mechanisms behind cancer-induced muscle wasting remain under investigation.

RECENT FINDINGS

Cytokines such as tumor necrosis factor-alpha trigger degradatory pathways through nuclear factor-kappaB signaling that activate the ubiquitin-proteasome system and muscle proteolysis. Androgen treatment has been shown to reduce inflammatory cytokines and even stimulate anti-inflammatory cytokine production. Amino acid supplementation has been shown to induce muscle protein synthesis in ovarian cancer patients.

SUMMARY

Targeted anabolic therapies aimed at preventing or reversing cancer cachexia might involve the combined use of androgens and amino acids working concurrently to enhance muscle protein synthesis and reduce muscle protein breakdown. Additional focused clinical studies are needed to identify muscle-specific targets or biomarkers for defined therapeutic approaches to slow or prevent cancer cachexia. In this review, we summarize the pathogenesis of cancer-related muscle wasting and discuss potential interventions at reversing or preventing cancer-related muscle loss.

Cancer cachexia: medical management

BACKGROUND

Cachexia is a complex metabolic syndrome associated with many chronic or end-stage diseases, especially cancer, and is characterized by loss of muscle with or without loss of fat mass. The management of cachexia is a complex challenge that should address the different causes underlying this clinical event with an integrated or multimodal treatment approach targeting the different factors involved in its pathophysiology.

MATERIALS AND METHODS

The purpose of this article was to review the current medical treatment of cancer-related cachexia, in particular focusing on combination therapy and ongoing research.

RESULTS

Among the treatments proposed in the literature for cancer-related cachexia, some proved to be ineffective, namely, cyproheptadine, hydrazine, metoclopramide, and pentoxifylline. Among effective treatments, progestagens are currently considered the best available treatment option for cancer-related cachexia, and they are the only drugs approved in Europe. Drugs with a strong rationale that have failed or have not shown univocal results in clinical trials so far include eicosapentaenoic acid, cannabinoids, bortezomib, and anti-TNF-alpha MoAb. Several emerging drugs have shown promising results but are still under clinical investigation (thalidomide, selective cox-2 inhibitors, ghrelin mimetics, insulin, oxandrolone, and olanzapine).

CONCLUSIONS

To date, despite several years of co-ordinated efforts in basic and clinical research, practice guidelines for the prevention and treatment of cancer-related muscle wasting are lacking, mainly because of the multifactorial pathogenesis of the syndrome. From all the data presented, one can speculate that one single therapy may not be completely successful in the treatment of cachexia. From this point of view, treatments involving different combinations are more likely to be successful.

Tryptophan in wasting diseases: at the crossing between immune function and behaviour

PURPOSE OF REVIEW

Wasting diseases are characterized by progressive deterioration of nutritional status that negatively influences patients' outcome. The better understanding of the pathogenic mechanisms of wasting may lead to effective therapies. Tryptophan metabolism has unique features suggesting a critical role in influencing human metabolism under normal and pathological conditions.

RECENT FINDINGS

During disease, inflammatory response favours the local depletion of the essential amino acid tryptophan, thereby inhibiting cellular proliferation. Tryptophan depletion may also mediate immunotolerance to foreign antigens. In contrast, brain accumulation of tryptophan contributes to wasting by increasing oxidative stress and hypothalamic serotonin neurotransmission, and thereby triggering the onset of sickness behaviour followed by depressive-like behaviour.

SUMMARY

Tryptophan metabolism is critical in mediating a number of important biological responses. Restoring tryptophan metabolism may well result in enhanced recovery from disease.

Dietary supplementation with a specific combination of high protein, leucine, and fish oil improves muscle function and daily activity in tumour-bearing cachectic mice

Cancer cachexia is characterised by metabolic alterations leading to loss of adipose tissue and lean body mass and directly compromises physical performance and the quality of life of cancer patients. In a murine cancer cachectic model, the effects of dietary supplementation with a specific combination of high protein, leucine and fish oil on weight loss, muscle function and physical activity were investigated. Male CD2F1 mice, 6–7 weeks old, were divided into body weight-matched groups: (1) control, (2) tumour-bearing, and (3) tumour-bearing receiving experimental diets. Tumours were induced by s.c. inoculation with murine colon adenocarcinoma (C26) cells. Food intake, body mass, tumour size and 24 h-activity were monitored. Then, 20 days after tumour/vehicle inoculation, the animals were killed and muscle function was tested ex vivo. Tumour-bearing mice showed reduced carcass, muscle and fat mass compared with controls. EDL muscle performance and total daily activity were impaired in the tumour-bearing mice. Addition of single nutrients resulted in no or modest effects. However, supplementation of the diet with the all-in combination of high protein, leucine and fish oil significantly reduced loss of carcass, muscle and fat mass (loss in mass 45, 52 and 65% of TB-con, respectively (P<0.02)) and improved muscle performance (loss of max force reduced to 55–64% of TB-con (P<0.05)). Moreover, total daily activity normalised after intervention with the specific nutritional combination (50% of the reduction in activity of TB-con (P<0.05)). In conclusion, a nutritional combination of high protein, leucine and fish oil reduced cachectic symptoms and improved functional performance in cancer cachectic mice. Comparison of the nutritional combination with its individual modules revealed additive effects of the single components provided.

Cardiac cachexia: a systematic overview

Cardiac cachexia as a terminal stage of chronic heart failure carries a poor prognosis. The definition of this clinical syndrome has been a matter of debate in recent years. This review describes the ongoing discussion about this issue and the complex pathophysiology of cardiac cachexia and chronic heart failure with particular focus on immunological, metabolic, and hormonal aspects at the intracellular and extracellular level. These include regulators such as neuropeptide Y, leptin, melanocortins, ghrelin, growth hormone, and insulin. The regulation of feeding is discussed as are nutritional aspects in the treatment of the disease. The mechanisms of wasting in different body compartments are described. Moreover, we discuss several therapeutic approaches. These include appetite stimulants like megestrol acetate, medroxyprogesterone acetate, and cannabinoids. Other drug classes of interest comprise angiotensin-converting enzyme inhibitors, beta-blockers, anabolic steroids, beta-adrenergic agonists, anti-inflammatory substances, statins, thalidomide, proteasome inhibitors, and pentoxifylline.

Neural control of the anorexia-cachexia syndrome

The anorexia-cachexia syndrome is a debilitating clinical condition characterizing the course of chronic diseases, which heavily impacts on patients' morbidity and quality of life, ultimately accelerating death. The pathogenesis is multifactorial and reflects the complexity and redundancy of the mechanisms controlling energy homeostasis under physiological conditions. Accumulating evidence indicates that, during disease, disturbances of the hypothalamic pathways controlling energy homeostasis occur, leading to profound metabolic changes in peripheral tissues. In particular, the hypothalamic melanocortin system does not respond appropriately to peripheral inputs, and its activity is diverted largely toward the promotion of catabolic stimuli (i.e., reduced energy intake, increased energy expenditure, possibly increased muscle proteolysis, and adipose tissue loss). Hypothalamic proinflammatory cytokines and serotonin, among other factors, are key in triggering hypothalamic resistance. These catabolic effects represent the central response to peripheral challenges (i.e., growing tumor, renal, cardiac failure, disrupted hepatic metabolism) that are likely sensed by the brain through the vagus nerve. Also, disease-induced changes in fatty acid oxidation within hypothalamic neurons may contribute to the dysfunction of the hypothalamic melanocortin system. Ultimately, sympathetic outflow mediates, at least in part, the metabolic changes in peripheral tissues. Other factors are likely involved in the pathogenesis of the anorexia-cachexia syndrome, and their role is currently being elucidated. However, available evidence shows that the constellation of symptoms characterizing this syndrome should be considered, at least in part, as different phenotypes of common neurochemical/metabolic alterations in the presence of a chronic inflammatory state.

Nutritional considerations in heart failure

There are a number of factors related to heart failure pathophysiology and treatment that influence nutrient requirements for patients. These include catabolism, inflammation, oxidative stress, diuretic use, and presence of comorbidities. On the other hand, there is evidence that specific nutrients can alter heart failure pathophysiology. This article reviews the current evidence for nutritional recommendations regarding sodium and fluid restriction, macro- and micronutrient intake, and dietary changes required by the presence of common comorbidities.

Free tryptophan/large neutral amino acids ratios in blood plasma do not predict cerebral spinal fluid tryptophan concentrations in interleukin-1-induced anorexia

Peripheral administration of interleukin-1 (IL-1) reduces food intake and affects brain serotonergic activity, suggesting a causal relationship. Furthermore, IL-1 increases the brain concentrations of the serotonin precursor, tryptophan (TRP), by unclear mechanism(s). We aimed at confirming the link between IL-1 administration, raised brain TRP concentrations and the development of anorexia, and at investigating the mechanisms of TRP entry into the brain. Thirty adult, overnight fasted Sprague-Dawley rats were randomly assigned to i.p. injections of 1 mug/kg BW of IL-1 alpha (n=10) or vehicle (n=10), or to pair-feeding with IL-1 animals (n=10). After 2 h, food intake, blood plasma concentrations of total TRP, free TRP, large neutral amino acids (LNAA; competing with TRP for brain entry) were measured. Cerebral spinal fluid (CSF) TRP concentrations were also measured. TRP brain availability was assessed by calculating the plasma ratio free TRP/LNAA. Following IL-1 injection, food intake significantly declined in IL-1 rats, which was paralleled by decreased plasma free TRP and increased plasma LNAA. Despite a decrease in the free TRP/LNAA ratios in plasma, IL-1 significantly increased concentrations of TRP in CSF. These data show that the acute peripheral administration of IL-1 induces anorexia and raises CSF TRP levels. Considering the possible role of the raised CSF TRP in influencing brain serotonin activity, it is postulated that increased serotonergic neurotransmission could be involved in IL-1 induced anorexia.

Development and validation of a liquid chromatographic method for the determination of branched-chain amino acids in new dosage forms

A reversed-phase liquid chromatographic method (RP-LC) is proposed and validated for the analysis of branched-chain amino acids (l-leucine, l-isoleucine and l-valine) in new pharmaceutical formulations. The pre-column derivatization reaction of these amino acids with 2,4-dinitrofluorobenzene (DNFB) has been investigated considering the matrix effect. The compound reacts at 60 degrees C for 10 min at pH 9 with the amino function, in presence of cetyltrimethylammonium bromide (CTAB), to give adducts that have been separated on a RP amide C16 column and detected at lambda=360 nm. Linear responses were observed for each derivative. The intra-day precision (R.S.D.) was <or=2.22% and there was no significant difference between intra- and inter-day data. Recovery studies showed good results for all amino acids (98.9-100.9%) with R.S.D. ranging from 0.1% to 0.8%. The limit of quantitation was about 20 nmol/mL.

Antimyopathic effects of carnitine and nicotine

PURPOSE OF REVIEW

The clinical course of most chronic diseases is associated with declined energy intake and nutrient-resistant progressive myopathy, characterized by accelerated proteolysis and impaired function. This anorexia/cachexia syndrome leads to deterioration of quality of life, and increased morbidity and mortality. The clinical efficacy of currently available therapeutic strategies is limited and more effective treatments are needed.

RECENT FINDINGS

Chronic systemic inflammation, triggered and sustained by cytokines, and increased oxidative stress contribute to the pathogenesis of the anorexia/cachexia syndrome. Carnitine and nicotine have recently been tested as immunomodulating and antioxidant agents. In particular, carnitine supplementation has been shown to reduce chronic inflammation and oxidative stress in hemodialysis patients and, in cancer patients, yielding to reduced fatigue and improved outcome. Nicotine is able to induce the anti-inflammatory activity of the vagus nerve. In animal models of sepsis and cancer, the nicotine-induced supplementation resulted in better protection of nutritional status and improved survival.

SUMMARY

In the continuous effort to develop more efficacious strategies against the anorexia/cachexia syndrome, carnitine and nicotine may represent a further therapeutic tool. More clinical studies are needed, however, before their use can be routinely suggested.

Determinants of Disuse-Induced Skeletal Muscle Atrophy: Exercise and Nutrition Countermeasures to Prevent Protein Loss

Muscle atrophy results from a variety of conditions such as disease states, neuromuscular injuries, disuse, and aging. Absence of gravitational loading during spaceflight or long-term bed rest predisposes humans to undergo substantial loss of muscle mass and, consequently, become unfit and/or unhealthy. Disuse- or inactivity-induced skeletal muscle protein loss takes place by differential modulation of proteolytic and synthetic systems. Transcriptional, translational, and posttranslational events are involved in the regulation of protein synthesis and degradation in myofibers, and these regulatory events are known to be responsive to contractile activity. However, regardless of the numerous studies which have been performed, the intracellular signals that mediate skeletal muscle wasting due to muscular disuse are not completely comprehended. Understanding the triggers of atrophy and the mechanisms that regulate protein loss in unloaded muscles may lead to the development of effective countermeasures such as exercise and dietary intervention. The objective of the present review is to provide a window into the molecular processes that underlie skeletal muscle remodeling and to examine what we know about exercise and nutrition countermeasures designed to minimize muscle atrophy.

Role of enteral and parenteral nutrition in the patient with gastrointestinal and liver disease

This chapter discusses a number of key issues: the importance of nutritional support, both enteral (oral nutritional supplements, enteral tube feeding) and parenteral nutrition in the treatment of the nutritionally compromised patient with gastrointestinal and liver disease; prescribing and monitoring nutritional support; refeeding syndrome; practicalities, indications and contraindications and complications of using enteral and parenteral nutrition; choosing feeds with an optimal nutrient composition for nutritional support, including specific feeds for disease states; the evidence base for using nutritional support in the patient with gastrointestinal and liver disease.

Nutrition in end stage liver disease

This chapter will focus on studies within the last 5 years of nutrition in end stage liver disease, but earlier studies illustrating the present state of affairs will also be mentioned. The first part will focus on descriptive epidemiological studies that help to set the scene for the intervention studies, which will be described in the second part. Each part will discuss liver cirrhosis, acute liver failure and liver transplantation separately. The aim is to provide the reader with sufficient background for the decision in clinical practice about when to see nutrition support as an important part of treatment of the patient.