ISSN:1363-1950    

出版商:OVID    

年代:1999

数据来源: OVID

ISSN:1363-1950    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

There is evidence that both counter-regulatory hormones, in particular glucocorticoids, and cytokines influence amino acid and protein metabolism in skeletal muscle, and that these two groups of regulators interact in the development of muscle catabolism. Glucocorticoids stimulate muscle proteolysis during sepsis and also in other catabolic conditions. In addition, glucocorticoids regulate muscle glutamine metabolism, resulting in increased glutamine release and reduced glutamine concentrations in skeletal muscle. Glucocorticoids inhibit the glutamine transporter in skeletal muscle and stimulate glutamine synthetase activity. Proinflammatory cytokines, in particular tumor necrosis factor and interleukin-1, inhibit muscle amino acid transport by system A, and these cytokine effects are probably indirect. Most of the catabolic effects of tumor necrosis factor in skeletal muscle, including stimulated protein degradation and inhibited amino acid uptake, are mediated by glucocorticoids.

ISSN:1363-1950    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

Participants in competitive sports have demonstrated that the use of growth factors and other anabolic agents enhance human performance, yet physicians are slow to adopt this approach in patients who have a disease-related decrease in strength and activity. Growth factors should be thought of as the next major step forward in providing more efficient and effective nutritional support to catabolic or wasted patients. The obstacles to the use of these agents include: the lack of convincing clinical studies; concerns with safety; anabolic effects and the patient's nutritional status; interaction with diet and route of nutrient administration; the training of health professionals to administer growth factors; and cost. The benefits from these agents should be directly translated into improved patient outcome. To achieve this goal, a uniquely educated group of investigators, working with sophisticated representatives from the pharmaceutical industry, must emerge to construct appropriate protocols and determine desirable endpoints to evaluate the true societal benefits of these agents.

ISSN:1363-1950    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

The advantages and problems, both practical and theoretical, of isotope dilution approaches to the determination of whole-body and tissue protein turnover are discussed. It was concluded that: (1) measurements made on the basis of the labelling of plasma and breath are well suited to the measurement of body amino acid oxidation and balance, but because of the problem of inhomogeneity of the body amino acid pools, this approach generally underestimates protein turnover; (2) in investigations of nutritional effects on whole-body amino acid turnover, closer attention should be paid to first-pass splanchnic amino acid metabolism; (3) the trans-organ tracer balance method, particularly if combined with the measurement of tissue amino acid labelling, is a potentially useful approach to the simultaneous and dynamic measurement of both protein synthesis and degradation; (4) leucine may be the most generally useful label for tracer level studies of both whole-body and muscle protein synthesis, as recent studies have shown quite close isotopic equilibrium between muscle-free and tRNA-bound leucine pools.

ISSN:1363-1950    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

To understand the mechanisms of muscle wasting, muscle protein turnover is measured. Several techniques are available, including whole body protein turnover measurements and incorporation of tracer into mixed muscle protein. In this brief review, we will focus on these techniques. We conclude that whole body measurements cannot be used as a parameter of muscle protein metabolism. It appears that whole body measurements mainly represent splanchnic protein metabolism. Muscle protein synthesis preferably is measured in individual proteins or protein subfractions.

ISSN:1363-1950    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

Theoretically, α-ketoglutarate is a precursor of glutamine, a fact that may be of importance given the key regulatory properties of this amino acid. Although the literature suggests that glutamine synthesis accounts only for a marginal part of the disposal of exogenously supplied α-ketoglutarate, administered α-ketoglutarate has a potent ‘sparing’ effect on endogenous glutamine pools. When α-ketoglutarate is supplied as an ornithine salt, a synergistic effect of the two parts of the molecule increases the synthesis of glutamine or the ‘sparing’ of endogenous glutamine pools. In addition, α-ketoglutarate in combination with ornithine dramatically increases the synthesis of arginine, proline and polyamines, which also play key roles in metabolic adaptation to trauma. The recent literature suggests that the administration of α-ketoglutarate in combination with ornithine improves gut morphology and functions, counteracts trauma-induced dysimmunity and exerts anabolic/anticatabolic actions on protein metabolism.

ISSN:1363-1950    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

This brief review is concerned with the status of our current understanding of the quantitative needs for dietary amino acids in healthy adults. The nutritional significance of the conditionally indispensable amino acids is assessed and the requirements for the indispensable amino acids are discussed. Recent research involving the use of the tracer balance approach is reviewed, and the importance of resolving the current uncertainties regarding adult human amino acid needs is highlighted.

ISSN:1363-1950    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

The impairment of transsulphuration during methionine degradation in hepatic failure can be counteracted by treatment withS-adenosylmethionine. Regarding the pathogenesis of hepatic encephalopathy, no convincing evidence exists for tryptophan, glutamine or glutamate being involved. Portal-systemic shunting-induced hyperammonaemia may reduce plasma branched-chain amino acids. The glucose effect on urea synthesis does not exist in cirrhosis.

ISSN:1363-1950    

出版商:OVID    

年代:1999

数据来源: OVID

ISSN:1363-1950    

出版商:OVID    

年代:1999

数据来源: OVID