Klas Bennegård

Whole-body tyrosine flux in relation to energy expenditure in weight-losing cancer patients

Whole-body tyrosine flux was measured in seven weight-losing cancer patients and compared with that of seven noncancer patients with malnutrition. L[U-14C] tyrosine was infused intravenously (IV) after an overnight fast under resting conditions and flux rates, oxidation, and incorporation into proteins of tyrosine were calculated from plateau values of specific activity of tyrosine in plasma and of labeled expired carbon dioxide. Rates of protein synthesis were calculated from the flux rate of tyrosine after subtracting the proportion oxidized. Simultaneous measurements of whole-body carbon dioxide production and oxygen uptake were also performed in each subject. Cancer patients had elevated whole-body tyrosine flux, protein synthesis, and energy expenditure when expressed in relation to body weight and whole-body potassium while the differences in tyrosine kinetics became of borderline significance when expressed in relation to energy expenditure. Tyrosine incorporation into whole-body proteins corresponded to a synthesis rate of 2.70 +/- 0.17 protein/kg/d in cancer patients and 2.18 +/- 0.17 in control patients (P less than 0.025). The results show that elevated protein synthesis in weight-losing cancer patients may explain not more than one third of the elevated energy expenditure. Therefore, other systems that utilize energy must increase in activity.

Insufficient effect of total parenteral nutrition to improve protein balance in peripheral tissues of surgical patients.

Previous studies have indicated that unstressed and malnourished patients do not necessarily obtain amino acid balance across peripheral tissues during total parenteral nutrition (TPN) treatment, indicating treatment inefficiency. Therefore, the aim of this study was to evaluate to what extent (prevalence) insufficient therapeutic amino acid balance occurs in surgical patients receiving TPN for standard medical reasons. Thirty-two patients treated in an ordinary surgical ward (n = 17) or in the intensive care unit (ICU) (n = 15) were examined. The arteriovenous balance across the leg of amino acids, glucose, glycerol, lactate, and oxygen was measured in relationship to plasma levels of insulin. All patients had been receiving TPN for at least 7 days before the investigation. All measurements were performed when amino acids had been infused for at least 4 hours and thus expected to support the resynthesis of lean body mass. Patients treated in the ICU and the surgical ward were in positive whole-body energy balance (+1127 +/- 121 and +917 +/- 123 kcal, respectively). Glucose uptake and oxygen consumption across the leg were similar in both patient groups. Glycerol release was not different from zero balance, indicating that inhibition of lipolysis across the leg during feeding and lactate was normally released in both groups. However, approximately 50% of the patients treated in the ordinary ward and 80% to 100% of the patients in the ICU remained in negative amino acid balance across the leg as judged from significant release of either methionine, tyrosine, or phenylalanine despite concomitant infusion of amino acids (approximately 0.3 g of N per kilogram per day) and nonprotein calories.(ABSTRACT TRUNCATED AT 250 WORDS)

Is it Possible to Evaluate the Efficacy of Amino Acid Solutions after Major Surgical Procedures or Accidental Injuries? Evaluation in a Randomized and Prospective Study

Two unbalanced amino acid solutions (essential amino acids, branched-chain amino acids) were compared to a complete and balanced amino acid solution with regard to efficacy of nitrogen balance. Patients were randomized to receive the amino acid solutions over 3 days for each regimen. The patients were examined postoperatively or directly after accidental trauma. Nonprotein calories were given as 40 kcal/kg/day consisting of 50% fat and 50% glucose. Nitrogen was given at the amount of 0.15 g N/kg/day. Unbalanced amino acid solutions gave a 2-fold more negative nitrogen balance than a balanced and complete amino acid solution. However, this difference disappeared and nitrogen balance approached equilibrium irrespective of the amino acid composition of the infused solutions when nitrogen in blood products was accounted for. All patients received a considerable amount of blood products in a comparable but unpredictable way. Blood products corresponded to around 40% of the daily nitrogen intake. Our study demonstrates that it is not possible to test the efficacy of amino acids for nitrogen retention in patients who are in the need of blood-product transfusions. It is likely that amino acids in blood proteins serve as a significant amino acid source that is utilized for resynthesis of body proteins especially in flow-phase patients with high protein breakdown. This fact has not been sufficiently accounted for in the previous literature.