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de Moraes Salgado C, da Silva Miyaguti NA, de Oliveira SCP, Favero-Santos BC, Viana LR, de Moraes Santos Oliveira M, Gomes-Marcondes MCC. Cancer during pregnancy. Maternal, placenta, and fetal damage. Nutrition, antioxidant defenses, and adult offspring tumor-bearing. Cancer 2021. [DOI: 10.1016/b978-0-12-819547-5.00012-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Prenatal Amino Acid Supplementation to Improve Fetal Growth: A Systematic Review and Meta-Analysis. Nutrients 2020; 12:nu12092535. [PMID: 32825593 PMCID: PMC7551332 DOI: 10.3390/nu12092535] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Revised: 08/16/2020] [Accepted: 08/19/2020] [Indexed: 12/12/2022] Open
Abstract
Aberrant fetal growth remains a leading cause of perinatal morbidity and mortality and is associated with a risk of developing non-communicable diseases later in life. We performed a systematic review and meta-analysis combining human and animal studies to assess whether prenatal amino acid (AA) supplementation could be a promising approach to promote healthy fetal growth. PubMed, Embase, and Cochrane libraries were searched to identify studies orally supplementing the following AA groups during gestation: (1) arginine family, (2) branched chain (BCAA), and (3) methyl donors. The primary outcome was fetal/birth weight. Twenty-two human and 89 animal studies were included in the systematic review. The arginine family and, especially, arginine itself were studied the most. Our meta-analysis showed beneficial effects of arginine and (N-Carbamyl) glutamate (NCG) but not aspartic acid and citrulline on fetal/birth weight. However, no effects were reported when an isonitrogenous control diet was included. BCAA and methyl donor supplementation did not affect fetal/birth weight. Arginine family supplementation, in particular arginine and NCG, improves fetal growth in complicated pregnancies. BCAA and methyl donor supplementation do not seem to be as promising in targeting fetal growth. Well-controlled research in complicated pregnancies is needed before ruling out AA supplements or preferring arginine above other AAs.
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Cruz B, Oliveira A, Gomes-Marcondes MCC. L-leucine dietary supplementation modulates muscle protein degradation and increases pro-inflammatory cytokines in tumour-bearing rats. Cytokine 2017; 96:253-260. [PMID: 28494385 DOI: 10.1016/j.cyto.2017.04.019] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2016] [Revised: 04/11/2017] [Accepted: 04/18/2017] [Indexed: 11/16/2022]
Abstract
Cancer cachexia is characterised by involuntary weight loss associated with systemic inflammation and metabolic changes. Studies aimed at maintaining lean body mass in cachectic tumour-bearing hosts have made important contributions reducing the number of deaths and improving the quality of life. In recent years, leucine has demonstrated effective action in maintaining lean body mass by decreasing muscle protein degradation. Currently, there is a growing need to understand how leucine stimulates protein synthesis and acts protectively in a cachectic organism. Thus, this study aimed to assess the effects of a leucine-rich diet on protein degradation signalling in muscle over the course of tumour growth. Animals were distributed into four experimental groups, which did or did not receive 2×106 viable Walker-tumour cells. Some were fed a leucine-rich diet, and the groups were subsequently sacrificed at three different time points of tumour evolution (7th, 14th, and 21st days). Protein degradation signals, as indicated by ubiquitin-proteasome subunits (11S, 19S, and 20S) and pro- and anti-inflammatory cytokines, were analysed in all experimental groups. In tumour-bearing animals without nutritional supplementation (W7, W14, and W21 groups), we observed that the tumour growth promoted a concurrent decrease in muscle protein, a sharp increase in pro-inflammatory cytokines (TNFα, IL-6, and IFNγ), and a progressive increase in proteasome subunits (19S and 20S). Thus, the leucine-supplemented tumour-bearing groups showed improvements in muscle mass and protein content, and in this specific situation, the leucine-rich diet led to an increase on the day in cytokine profile and proteasome subunits mainly on the 14th day, which subsequently had a modulating effect on tumour growth on the 21st day. These results indicate that the presence of leucine in the diet may modulate important aspects of the proteasomal pathway in cancer cachexia and may prevent muscle wasting due to the decrease in the cachexia index.
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Affiliation(s)
- Bread Cruz
- Department of Structural and Functional Biology, Biology Institute, State University of Campinas, UNICAMP, CP 6109, 13083862 Campinas, Sao Paulo, Brazil
| | - André Oliveira
- Department of Structural and Functional Biology, Biology Institute, State University of Campinas, UNICAMP, CP 6109, 13083862 Campinas, Sao Paulo, Brazil
| | - Maria Cristina Cintra Gomes-Marcondes
- Department of Structural and Functional Biology, Biology Institute, State University of Campinas, UNICAMP, CP 6109, 13083862 Campinas, Sao Paulo, Brazil.
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Viana LR, Canevarolo R, Luiz ACP, Soares RF, Lubaczeuski C, Zeri ACDM, Gomes-Marcondes MCC. Leucine-rich diet alters the 1H-NMR based metabolomic profile without changing the Walker-256 tumour mass in rats. BMC Cancer 2016; 16:764. [PMID: 27716121 PMCID: PMC5048609 DOI: 10.1186/s12885-016-2811-2] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2016] [Accepted: 09/23/2016] [Indexed: 01/09/2023] Open
Abstract
Background Cachexia is one of the most important causes of cancer-related death. Supplementation with branched-chain amino acids, particularly leucine, has been used to minimise loss of muscle tissue, although few studies have examined the effect of this type of nutritional supplementation on the metabolism of the tumour-bearing host. Therefore, the present study evaluated whether a leucine-rich diet affects metabolomic derangements in serum and tumour tissues in tumour-bearing Walker-256 rats (providing an experimental model of cachexia). Methods After 21 days feeding Wistar female rats a leucine-rich diet, distributed in L-leucine and LW-leucine Walker-256 tumour-bearing groups, we examined the metabolomic profile of serum and tumour tissue samples and compared them with samples from tumour-bearing rats fed a normal protein diet (C – control; W – tumour-bearing groups). We utilised 1H-NMR as a means to study the serum and tumour metabolomic profile, tumour proliferation and tumour protein synthesis pathway. Results Among the 58 serum metabolites examined, we found that 12 were altered in the tumour-bearing group, reflecting an increase in activity of some metabolic pathways related to energy production, which diverted many nutrients toward tumour growth. Despite displaying increased tumour cell activity (i.e., higher Ki-67 and mTOR expression), there were no differences in tumour mass associated with changes in 23 metabolites (resulting from valine, leucine and isoleucine synthesis and degradation, and from the synthesis and degradation of ketone bodies) in the leucine-tumour group. This result suggests that the majority of nutrients were used for host maintenance. Conclusion A leucine rich-diet, largely used to prevent skeletal muscle loss, did not affect Walker 256 tumour growth and led to metabolomic alterations that may partially explain the positive effects of leucine for the whole tumour-bearing host.
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Affiliation(s)
- Laís Rosa Viana
- Department of Structural and Functional Biology, Laboratory of Nutrition and Cancer, Institute of Biology, University of Campinas-UNICAMP, Campinas, 13083862, São Paulo, Brazil
| | - Rafael Canevarolo
- Brazilian Biosciences National Laboratory, Campinas, São Paulo, Brazil
| | - Anna Caroline Perina Luiz
- Department of Structural and Functional Biology, Laboratory of Nutrition and Cancer, Institute of Biology, University of Campinas-UNICAMP, Campinas, 13083862, São Paulo, Brazil
| | - Raquel Frias Soares
- Department of Structural and Functional Biology, Laboratory of Nutrition and Cancer, Institute of Biology, University of Campinas-UNICAMP, Campinas, 13083862, São Paulo, Brazil
| | - Camila Lubaczeuski
- Department of Structural and Functional Biology, Laboratory of Nutrition and Cancer, Institute of Biology, University of Campinas-UNICAMP, Campinas, 13083862, São Paulo, Brazil
| | | | - Maria Cristina Cintra Gomes-Marcondes
- Department of Structural and Functional Biology, Laboratory of Nutrition and Cancer, Institute of Biology, University of Campinas-UNICAMP, Campinas, 13083862, São Paulo, Brazil.
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Belizário JE, Fontes-Oliveira CC, Borges JP, Kashiabara JA, Vannier E. Skeletal muscle wasting and renewal: a pivotal role of myokine IL-6. SPRINGERPLUS 2016; 5:619. [PMID: 27330885 PMCID: PMC4870483 DOI: 10.1186/s40064-016-2197-2] [Citation(s) in RCA: 146] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/03/2016] [Accepted: 04/20/2016] [Indexed: 12/20/2022]
Abstract
Adult skeletal tissue is composed of heterogeneous population of cells that constantly self-renew by means of a controlled process of activation and proliferation of tissue-resident stem cells named satellite cells. Many growth factors, cytokines and myokines produced by skeletal muscle cells play critical roles in local regulation of the inflammatory process and skeletal muscle regeneration during different pathological conditions. IL-6 is a pleiotropic cytokine released in large amount during infection, autoimmunity and cancer. Low levels of IL-6 can promote activation of satellite cells and myotube regeneration while chronically elevated production promote skeletal muscle wasting. These distinct effects may be explained by a crosstalk of the IL-6/IL-6 receptor and gp130 trans-signaling pathway that oppose to regenerative and anti-inflammatory of the classical IL-6 receptor signaling pathway. Here we discuss on potential therapeutic strategies using monoclonal antibodies to IL-6R for the treatment of skeletal muscle wasting and cachexia. We also highlight on the IL-6/JAK/STAT and FGF/p38αβ MAPK signaling pathways in satellite cell activation and the use of protein kinase inhibitors for tailoring and optimizing satellite cell proliferation during the skeletal muscle renewal. Future investigations on the roles of the IL-6 classical and trans-signaling pathways in both immune and non-immune cells in skeletal muscle tissue will provide new basis for therapeutic approaches to reverse atrophy and degeneration of skeletal muscles in cancer and inflammatory diseases.
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Affiliation(s)
- José E Belizário
- Department of Pharmacology, Institute of Biomedical Sciences, University of São Paulo, Avenida Lineu Prestes, 1524, São Paulo, SP 05508-900 Brazil
| | | | - Janaina Padua Borges
- Department of Pharmacology, Institute of Biomedical Sciences, University of São Paulo, Avenida Lineu Prestes, 1524, São Paulo, SP 05508-900 Brazil
| | - Janete Akemi Kashiabara
- Department of Pharmacology, Institute of Biomedical Sciences, University of São Paulo, Avenida Lineu Prestes, 1524, São Paulo, SP 05508-900 Brazil
| | - Edouard Vannier
- Division of Geographic Medicine and Infectious Disease, Tufts Medical Center, Boston, MA 02111 USA
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Reviewing the Effects of L-Leucine Supplementation in the Regulation of Food Intake, Energy Balance, and Glucose Homeostasis. Nutrients 2015; 7:3914-37. [PMID: 26007339 PMCID: PMC4446786 DOI: 10.3390/nu7053914] [Citation(s) in RCA: 75] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2015] [Revised: 04/30/2015] [Accepted: 05/12/2015] [Indexed: 12/18/2022] Open
Abstract
Leucine is a well-known activator of the mammalian target of rapamycin (mTOR). Because mTOR signaling regulates several aspects of metabolism, the potential of leucine as a dietary supplement for treating obesity and diabetes mellitus has been investigated. The objective of the present review was to summarize and discuss the available evidence regarding the mechanisms and the effects of leucine supplementation on the regulation of food intake, energy balance, and glucose homeostasis. Based on the available evidence, we conclude that although central leucine injection decreases food intake, this effect is not well reproduced when leucine is provided as a dietary supplement. Consequently, no robust evidence indicates that oral leucine supplementation significantly affects food intake, although several studies have shown that leucine supplementation may help to decrease body adiposity in specific conditions. However, more studies are necessary to assess the effects of leucine supplementation in already-obese subjects. Finally, although several studies have found that leucine supplementation improves glucose homeostasis, the underlying mechanisms involved in these potential beneficial effects remain unknown and may be partially dependent on weight loss.
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Cruz B, Gomes-Marcondes MCC. Leucine-rich diet supplementation modulates foetal muscle protein metabolism impaired by Walker-256 tumour. Reprod Biol Endocrinol 2014; 12:2. [PMID: 24383706 PMCID: PMC3895792 DOI: 10.1186/1477-7827-12-2] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/20/2013] [Accepted: 12/29/2013] [Indexed: 12/23/2022] Open
Abstract
BACKGROUND Cancer-cachexia induces a variety of metabolic disorders of protein turnover and is more pronounced when associated with pregnancy. Tumour-bearing pregnant rats have impaired protein balance, which decreases protein synthesis and increases muscle breakdown. Because branched-chain amino acids, especially leucine, stimulate protein synthesis, we investigated the effect of a leucine-rich diet on protein metabolism in the foetal gastrocnemius muscles of tumour-bearing pregnant rats. METHODS Foetuses of pregnant rats with or without Walker 256 tumours were divided into six groups. During the 20 days of the experiment, the pregnant groups were fed with either a control diet (C, control rats; W, tumour-bearing rats; Cp, rats pair-fed the same normoprotein-diet as the W group) or with a leucine-rich diet (L, leucine rats; LW, leucine tumour-bearing rats; and Lp, rats pair-fed the same leucine-rich diet as the LW group). After the mothers were sacrificed, the foetal gastrocnemius muscle samples were resected, and the protein synthesis and degradation and tissue chymotrypsin-like, cathepsin and calpain enzyme activities were assayed. The muscle oxidative enzymes (catalase, glutathione-S-transferase and superoxide dismutase), alkaline phosphatase enzyme activities and lipid peroxidation (malondialdehyde) were also measured. RESULTS Tumour growth led to a reduction in foetal weight associated with decreased serum protein, albumin and glucose levels and low haematocrit in the foetuses of the W group, whereas in the LW foetuses, these changes were less pronounced. Muscle protein synthesis (measured by L-[3H]-phenylalanine incorporation) was reduced in the W foetuses but was restored in the LW group. Protein breakdown (as assessed by tyrosine release) was enhanced in the L and W groups, but chymotrypsin-like activity increased only in group W and tended toward an increase in the LW foetuses. The activity of cathepsin H was significantly higher in the W group foetuses, but the proteolytic calcium-dependent pathway showed similar enzyme activity. In parallel, an intense oxidative stress process was observed only in the group W foetuses. CONCLUSIONS These data suggested that the proteasomal and lysosomal proteolytic pathways and oxidative stress are likely to participate in the process of foetal muscle catabolism of Walker's tumour-bearing pregnant rats. The present work shows that foetal muscle can be protected by supplementation with a leucine-rich diet.
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Affiliation(s)
- Bread Cruz
- Laboratory of Nutrition and Cancer, Department of Structural and Functional Biology, Institute of Biology, State University of Campinas - UNICAMP Campinas, 13083862 Sao Paulo, Brazil
| | - Maria CC Gomes-Marcondes
- Laboratory of Nutrition and Cancer, Department of Structural and Functional Biology, Institute of Biology, State University of Campinas - UNICAMP Campinas, 13083862 Sao Paulo, Brazil
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Leucine modulates the effect of Walker factor, a proteolysis-inducing factor-like protein from Walker tumours, on gene expression and cellular activity in C2C12 myotubes. Cytokine 2013; 64:343-50. [DOI: 10.1016/j.cyto.2013.05.018] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2013] [Revised: 05/15/2013] [Accepted: 05/17/2013] [Indexed: 01/26/2023]
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S–carboxyethylcysteine (a constituent of Acacia seed) negatively affects casein protein utilization by rats. Nutrition 2012; 28:785-92. [DOI: 10.1016/j.nut.2011.10.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2011] [Revised: 09/06/2011] [Accepted: 10/07/2011] [Indexed: 11/23/2022]
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Salomão EM, Gomes-Marcondes MCC. Light aerobic physical exercise in combination with leucine and/or glutamine-rich diet can improve the body composition and muscle protein metabolism in young tumor-bearing rats. J Physiol Biochem 2012; 68:493-501. [PMID: 22460363 DOI: 10.1007/s13105-012-0164-0] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2011] [Accepted: 03/13/2012] [Indexed: 01/15/2023]
Abstract
Nutritional supplementation with some amino acids may influence host's responses and also certain mechanism involved in tumor progression. It is known that exercise influences body weight and muscle composition. Previous findings from our group have shown that leucine has beneficial effects on protein composition in cachectic rat model as the Walker 256 tumor. The main purpose of this study was to analyze the effects of light exercise and leucine and/or glutamine-rich diet in body composition and skeletal muscle protein synthesis and degradation in young tumor-bearing rats. Walker tumor-bearing rats were subjected to light aerobic exercise (swimming 30 min/day) and fed a leucine-rich (3%) and/or glutamine-rich (4%) diet for 10 days and compared to healthy young rats. The carcasses were analyzed as total water and fat body content and lean body mass. The gastrocnemious muscles were isolated and used for determination of total protein synthesis and degradation. The chemical body composition changed with tumor growth, increasing body water and reducing body fat content and total body nitrogen. After tumor growth, the muscle protein metabolism was impaired, showing that the muscle protein synthesis was also reduced and the protein degradation process was increased in the gastrocnemius muscle of exercised rats. Although short-term exercise (10 days) alone did not produce beneficial effects that would reduce tumor damage, host protein metabolism was improved when exercise was combined with a leucine-rich diet. Only total carcass nitrogen and protein were recovered by a glutamine-rich diet. Exercise, in combination with an amino acid-rich diet, in particular, leucine, had effects beyond reducing tumoral weight such as improving protein turnover and carcass nitrogen content in the tumor-bearing host.
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Affiliation(s)
- Emilianne Miguel Salomão
- Department of Structural and Functional Biology, Biology Institute, State University of Campinas, UNICAMP, 13083-970, Campinas, São Paulo, Brazil
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Optimization of synthesizing leucine-binding nano-sized magnetite by a two-step transformation. KOREAN J CHEM ENG 2008. [DOI: 10.1007/s11814-008-0026-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Leucine-rich diet alters the eukaryotic translation initiation factors expression in skeletal muscle of tumour-bearing rats. BMC Cancer 2007; 7:42. [PMID: 17341295 PMCID: PMC1832207 DOI: 10.1186/1471-2407-7-42] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2006] [Accepted: 03/06/2007] [Indexed: 02/03/2023] Open
Abstract
Background Cancer-cachexia induces a variety of metabolic disorders on protein turnorver, decreasing protein synthesis and increasing protein degradation. Controversly, insulin, other hormones, and branched-chain amino acids, especially leucine, stimulate protein synthesis and modulate the activity of translation initiation factors involved in protein synthesis. Since the tumour effects are more pronounced when associated with pregnancy, ehancing muscle-wasting proteolysis, in this study, the influence of a leucine-rich diet on the protein synthesis caused by cancer were investigated. Methods Pregnant rats with or without Walker 256 tumour were distributed into six groups. During 20 days of experiment, three groups were fed with a control diet: C – pregnant control, W – tumour-bearing, and P – pair-fed, which received the same amount of food as ingested by the W group; three other groups of pregnant rats were fed a leucine-rich diet: L – pregnant leucine, WL – tumour-bearing, and PL – pair-fed, which received the same amount of food as ingested by the WL group. Results The gastrocnemius muscle of WL rats showed increased incorporation of leucine in protein compared to W rats; the leucine-rich diet also prevented the decrease in plasma insulin normally seen in W. The expression of translation initiation factors increased when tumour-bearing rats fed leucine-rich diet, with increase of ~35% for eIF2α and eIF5, ~17% for eIF4E and 20% for eIF4G; the expression of protein kinase S6K1 and protein kinase C was also highly enhanced. Conclusion The results suggest that a leucine-rich diet increased the protein synthesis in skeletal muscle in tumour-bearing rats possibly through the activation of eIF factors and/or the S6kinase pathway.
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Tie SL, Lin YQ, Lee HC, Bae YS, Lee CH. Amino acid-coated nano-sized magnetite particles prepared by two-step transformation. Colloids Surf A Physicochem Eng Asp 2006. [DOI: 10.1016/j.colsurfa.2005.08.027] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Baracos VE, Mackenzie ML. Investigations of branched-chain amino acids and their metabolites in animal models of cancer. J Nutr 2006; 136:237S-42S. [PMID: 16365090 DOI: 10.1093/jn/136.1.237s] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Many of the features of BCAA metabolism in the tumor-bearing state are similar to the other disease states that feature involuntary weight loss and skeletal muscle atrophy. These states are generally characterized by altered BCAA availability (low BCAA intakes, elevated rates of BCAA oxidation, and gluconeogenesis), which are concurrent with activation of proteolysis and suppression of protein synthesis in skeletal muscle and ultimately lead to erosion of lean tissue mass. These features in turn imply BCAA deficiency compared with whole-body requirements and are the basis of suggestions for dietary supplementation with BCAA or their metabolites. Recent studies on BCAA supplementation in cancer focus on leucine and its derivative, beta-methyl beta-hydroxybutyrate, as regulators of skeletal muscle metabolism, although their relative efficacy is unknown. However, what would otherwise be a relatively straightforward consideration of amino acid supply and demand is confounded by the presence of the tumor and its potential utilization of BCAA for its proliferative and invasive activities. Positron emission tomography with (11)C-leucine, used for in vivo tumor imaging, points to the high avidity of tumor amino acid uptake. These features have incited research in opposing directions, probing BCAA deprivation, with a view to limiting tumor growth, as well as BCAA supplementation, with a view to supporting maintenance of host lean tissue. No clear conclusion is presently available from the sum of these efforts. Animal models with relevant clinical features are essential to determine if amino acid therapy can alter the balance between the host and the tumor in a manner that favors the host overall.
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Affiliation(s)
- Vickie E Baracos
- Department of Agricultural, Food, and Nutritional Science, University of Alberta, Edmonton, Alberta, Canada.
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Abstract
PURPOSE OF REVIEW This review highlights recent publications dealing with the nature of the in-vivo response of skeletal muscle to critical illness and approaches to attenuating this response. Studies focused on molecular mechanisms of muscle catabolism are not reviewed. RECENT FINDINGS The general areas covered are the metabolic response to stress, particularly regarding the relationship between muscle protein breakdown, amino acid availability, and muscle protein synthesis. The impact of the profile of amino acids in the context of protein/amino acid intake is also discussed. Advances in our understanding of the hormonal response are considered, and use of insulin therapy to slow muscle catabolism is discussed. SUMMARY Muscle catabolism is a fundamental response to severe stress, and the resulting amino acid efflux from muscle provides important precursors for protein synthesis in other parts of the body. The nature of this response (i.e. transport kinetics favoring efflux of amino acids from muscle) makes amelioration of the catabolic response of muscle with nutrition alone very difficult. Many approaches have been used to reverse catabolism, mostly involving various anabolic hormones. Recent studies using insulin therapy are particularly intriguing because of the low cost and powerful anabolic stimulus of insulin.
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Affiliation(s)
- Robert R Wolfe
- The University of Texas Medical Branch, Department of Surgery and Shriners Burns Hospital, Metabolism Unit, Galveston, Texas, USA.
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