Efflux of 3-methylhistidine from the leg in cancer patients who experience weight loss.

An improved method for measurement of 3-methylhistidine in blood samples has been used to assess efflux of 3-methylhistidine from the leg in cancer patients experiencing weight loss. Three control groups were studied: malnourished depleted patients without cancer; comparatively well-nourished but acutely ill patients; and well-nourished controls, hospitalized for elective surgery, who showed no symptoms of metabolic disease. Well-nourished controls and acutely ill patients had a statistically significant release of 3-methylhistidine [1.92 +/- 0.40 (S.E.) nmol/min/100 g leg tissue and 0.93 +/- 0.32 nmol/min/100 g, respectively], but cancer patients and malnourished noncancer patients had insignificant efflux. When nutritional support was provided, noncancer patients abolished their previously negative tyrosine balance and increased the efflux of 3-methylhistidine; however, cancer patients as a group continued to show a negative tyrosine balance, and the efflux of 3-methylhistidine continued to decrease further in them. The results in this study demonstrate that weight loss in clinical cancer is not dependent on increased skeletal muscle protein degradation, not even at an early stage of the disease. It seems likely that decreased protein synthesis is a more important factor.