Increased incorporation of an infused labelled amino acid into plasma proteins as a means of assessing the severity of injury or activity of disease in surgical patients

Improved protein kinetics and albumin synthesis by branched chain amino acid-enriched total parenteral nutrition in cancer cachexia. A prospective randomized crossover trial

A prospective randomized crossover trial was conducted to determine the effect of a branched chain amino acid (BCAA)-enriched solution on whole body leucine kinetics and fractional rates of albumin synthesis in patients with intra-abdominal metastatic adenocarcinoma. Ten malnourished cancer patients were provided isonitrogenous amounts of both a conventional total parenteral nutrition (TPN) formula containing 19% BCAA and a BCAA-enriched TPN formula containing 50% of the amino acids as BCAA in a random order. Whole body protein turnover was determined by a 10 hour continuous infusion of leucine 14C. Increased whole body leucine flux (68 +/- 5 mumols/kg BW/hr versus 145 +/- 11; mean +/- SEM; P less than 0.001) and oxidation (13 +/- 2 mumols/kg BW/hr to 46 +/- 5; P less than 0.001) were determined on the BCAA-enriched TPN. Increased whole body protein synthesis (2.2 +/- 0.2 g protein/kg BW/day versus 3.9 +/- 0.3; P less than 0.005) and leucine balance (2.5 +/- 0.4 g leucine/d versus 6.5 +/- 0.6; P less than 0.001) were also observed in patients receiving the BCAA-enriched TPN solution. Leucine release from protein breakdown was not statistically elevated (1.65 +/- 0.18 g protein/kg BW/d versus 2.48 +/- 0.40; P greater than 0.05) but, incorporation of leucine 14C into plasma albumin was significantly elevated (2.37 +/- 0.23 mumols/g/hr to 4.21 +/- 0.33; P less than 0.001) when the patients received BCAA-enriched TPN. Despite the better leucine balance, the improvement in the 24-hour urinary nitrogen balance was not statistically significant (6.6 +/- 3.9 g protein/d versus 11.4 +/- 2.9; control versus BCAA-enriched; P = 0.15). BCAA-enriched formulas improve whole body leucine kinetics, fractional rates of albumin synthesis, and leucine balance, and thus may favorably influence protein metabolism in cancer cachexia.

Demonstration of a reduction in postoperative body protein breakdown using the Clinitron fluidized bed with an ambient temperature of 32 degrees C

Patients managed at an elevated ambient temperature after major surgery have a less pronounced rise in postoperative urinary nitrogen excretion. To investigate the mechanism involved, body protein breakdown was assessed, using a tracer dose of labelled amino acid, in patients following aorto-bifemoral bypass surgery nursed on either a Clinitron fluidized bed at 32 degrees C or a hospital bed at 22 degrees C and correlated with urinary total nitrogen excretion. Results showed a small reduction in measured body protein breakdown on the second postoperative day in patients managed on the Clinitron fluidized bed at 32 degrees C (2.92 +/- 0.91 versus 3.23 +/- 0.84 g protein kg-1 day-1; mean +/- s.d.), which was equivalent to the mean protein sparing (0.29g protein kg-1 day-1) demonstrated by the significant improvement in urinary total nitrogen excretion (9.20 +/- 2.0 versus 12.48 +/- 3.9 g N day-1; mean +/- s.d.: P less than 0.05). Urinary total nitrogen excretion (N) and body protein breakdown (B) showed a weak though significant positive correlation (B = 1.25 + 13.13N; r = +0.55: P = 0.05), whereas no correlation existed between urinary total nitrogen excretion and the derived rate of body protein synthesis. There was also a significant decrease in postoperative stress, measured during the isotope infusion, in patients managed on the Clinitron fluidized bed at 32 degrees C (12.3 +/- 2.2 versus 16.1 +/- 3.2 per cent activity incorporated into plasma proteins; mean +/- s.d.: P less than 0.05). These results show the beneficial effect of managing postoperative patients on a Clinitron fluidized bed at 32 degrees C in conserving body nitrogen through a reduction in body protein breakdown, probably as a consequence of decreased postoperative stress.

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.