['Cancer and surgical stress interact to aggravate insulin resistance, protein catabolism, and glutamine depletion in skeletal muscle. We compared the effects of insulin-mediated euglycemia and moderate hyperglycemia on kinetics of protein and selected amino acids in skeletal muscle of female cancer patients after major surgery.', 'In each patient, a 24-hr period of insulin-mediated tight euglycemia (mean blood glucose, 5.8 +/- 0.4 mmol/L) preceded or followed a 24-hr control period of moderate hyperglycemia (mean blood glucose, 9.6 +/- 0.6 mmol/L) on the first and second day after surgery, in randomized order, according to a crossover experimental design.', 'Intensive care unit, cancer hospital.', 'Cancer patients after abdominal radical surgery combined with intraoperative radiation therapy.', 'Intensive (57 +/- 11 units/24 hrs) and conventional (25 +/- 5 units/24 hrs) insulin treatment during total parenteral nutrition.', 'Muscle metabolism was assessed at the end of each 24-hr period of euglycemia and of hyperglycemia by leg arteriovenous catheterization with stable isotopic tracers. We found that euglycemia as compared with hyperglycemia was associated with higher (p < .05) fractional glucose uptake (16% +/- 4% vs. 9% +/- 3%); higher (p < .05) muscle protein synthesis and neutral net protein balance (-3 +/- 3 vs. -11 +/- 3 nmol phenylalanine x 100 mL(-1) x min(-1), respectively); lower (-52% +/- 12%, p < .01) muscle nonprotein leucine disposal (an index of leucine oxidation) and higher (p < .05) plasma leucine concentrations; and higher (3.6 +/- 1.7 times, p < .01) net de novo muscle glutamine synthesis and plasma glutamine concentrations (p < .05). Euglycemia was associated with higher (23% +/- 7%, p < .05) plasma concentrations of arginine but did not affect either arginine release from muscle or plasma concentration and muscle flux of asymmetrical dimethylarginine. Rate of muscle proteolysis correlated (p < .05) with muscle release of asymmetrical dimethylarginine.'] Does treating hyperglycemia improve skeletal muscle protein metabolism in cancer patients after major surgery?