[Cachexia in cancer: disturbances in the protein and aminoacid metabolism]

Cancer induced cachexia is characterized by complex changes in the intermediary metabolism. There is a raised basal metabolism with increased turnover of lipids, carbohydrates and proteins. In this altered metabolic milieu, protein catabolism occurs in peripheral tissue resulting in release of amino acids for the benefit of visceral organs. These as a rule increase in protein mass and also produce more plasma proteins. The amino acid glutamine plays a central part in this. It is released in large amounts from muscle tissue and is consumed to a high degree by visceral organs and immune cells. Although biochemically glutamine is not an essential amino acid, in cancer-induced cachexia it appears to be a 'conditionally' essential amino acid. Changes in the protein metabolism appear to be controlled by chronically increased neuroendocrine and inflammatory activity (exerted among other things by tumour necrosis factor alpha, interleukins 1 and 6 and catecholamines). Fundamental research, animal experiments and certain clinical trials show that the metabolism altered by these mediators can be corrected using hormonal preparations such as growth hormone, beta 2-adrenergic agonists and insulin. In the future it may conceivably be possible to correct the metabolic disturbance with drugs and the depletion of nutrients with specific nutritional supplements.