Long-term safety and efficacy of anacetrapib in patients with atherosclerotic vascular disease.

AIMS: REVEAL was the first randomized controlled trial to demonstrate that adding cholesteryl ester transfer protein inhibitor therapy to intensive statin therapy reduced the risk of major coronary events. We now report results from extended follow-up beyond the scheduled study treatment period. METHODS AND RESULTS: A total of 30 449 adults with prior atherosclerotic vascular disease were randomly allocated to anacetrapib 100 mg daily or matching placebo, in addition to open-label atorvastatin therapy. After stopping the randomly allocated treatment, 26 129 survivors entered a post-trial follow-up period, blind to their original treatment allocation. The primary outcome was first post-randomization major coronary event (i.e. coronary death, myocardial infarction, or coronary revascularization) during the in-trial and post-trial treatment periods, with analysis by intention-to-treat. Allocation to anacetrapib conferred a 9% [95% confidence interval (CI) 3-15%; P = 0.004] proportional reduction in the incidence of major coronary events during the study treatment period (median 4.1 years). During extended follow-up (median 2.2 years), there was a further 20% (95% CI 10-29%; P < 0.001) reduction. Overall, there was a 12% (95% CI 7-17%, P < 0.001) proportional reduction in major coronary events during the overall follow-up period (median 6.3 years), corresponding to a 1.8% (95% CI 1.0-2.6%) absolute reduction. There were no significant effects on non-vascular mortality, site-specific cancer, or other serious adverse events. Morbidity follow-up was obtained for 25 784 (99%) participants. CONCLUSION: The beneficial effects of anacetrapib on major coronary events increased with longer follow-up, and no adverse effects emerged on non-vascular mortality or morbidity. These findings illustrate the importance of sufficiently long treatment and follow-up duration in randomized trials of lipid-modifying agents to assess their full benefits and potential harms. TRIAL REGISTRATION: International Standard Randomized Controlled Trial Number (ISRCTN) 48678192; ClinicalTrials.gov No. NCT01252953; EudraCT No. 2010-023467-18.

A model for isotopic sampling and administration in constant infusion experiments: a test with 13C-palmitate.

We have proposed and tested a model that demonstrates the importance of the site of isotopic sampling relative to the site of infusion for the constant infusion of labeled palmitate. Palmitate enrichment is significantly increased downstream from the infusion catheter. However, palmitate production is underestimated unless sampling is performed upstream from the catheter. There was no significant difference between upstream sampling from the femoral vein versus the right heart, whereas the downstream arterial sampling gave significantly higher enrichments compared to the femoral vein. We have also discussed the importance of sampling sites for other substrates and the constraints that this model places on the design and interpretation of whole body primed constant infusion experiments using labeled substrates.

Effect of total parenteral nutrition on free fatty acid metabolism in burned patients.

Free fatty acid (FFA) and energy metabolism were studied in six severely burned humans after an 8-hr fast, after 1 hr of total parenteral nutrition, and after 72 hr of uninterrupted total parenteral nutrition. Caloric intake was twice the predicted basal metabolic rate, with 5 mg kg-1 min-1 of glucose, 2.5 g kg-1 day-1 of amino acid and the remainder of calories supplied as a fat emulsion. 1,2-13C-palmitate bound to albumin was continuously infused in order to quantitate FFA turnover and oxidation. Endogenous FFA turnover and oxidation were markedly suppressed by parenteral feeding, presumably due to increased insulin release. A modest recovery occurred in the initial suppression of FFA oxidation after 72 hr, but not in FFA turnover. Fat emulsion provided about one-quarter of the energy released during parenteral feeding, with endogenous FFA oxidation as the major component. This was roughly equivalent to the percentage of calories supplied as fat. This work indicates that the direct oxidation of a lipid emulsion contributes only a small amount of energy released in the setting of the severely traumatized human receiving total parenteral nutrition but serves mainly to preserve endogenous fat stores.

Isotopic approaches to the estimation of protein requirements in burn patients.

Determination of the protein requirement of the severely burned patient has been hampered by the lack of an appropriate means of evaluating the effects of various levels of intake. We have used two new isotopic techniques in an attempt to assess the effects of two levels of protein intake in six severely burned adult patients. A crossover experimental design enabled us to study each patient at the end of two 3-day dietary regimens. All diets were isocaloric and provided approximately 25% more calories than the measured energy expenditure (means = 40 Kcal/kg X day). In one regimen, each patient received 2.2 g protein/kg X day; during the other treatment period they received 1.4 g protein/kg X day. The patients were studied in the fed state and after 10-12 h of fasting. Leucine kinetics were determined by means of the primed-constant infusion of (1-13C)-leucine. We were able to distinguish the oxidation of plasma leucine from the oxidation of leucine derived from intracellular protein at the site of the deamination of leucine (predominantly muscle) by simultaneously determining both leucine and alpha-ketoisocaproic acid enrichment. Also, rates of whole-body protein synthesis and catabolism were calculated by means of another stable-isotope technique involving the infusion of (15N2)-urea. Finally, a third means of estimating net protein catabolism based on urinary N-excretion data was used at the same time that the isotopic studies were performed. The 13C-leucine data and the N-excretion data indicated that a balance between protein synthesis and catabolism could be achieved with a protein intake of 1.4 protein/kg X day. When protein intake was increased to 2.2 g protein/kg X day, neither isotopic method indicated a further beneficial effect on net protein synthesis, although the absolute rates of protein synthesis and catabolism were stimulated. The N-excretion data, however, indicated a significant improvement in net protein synthesis with higher protein intake. Regardless of the level of protein intake, the underlying alterations in protein metabolism that occurred as a response to burn injury persisted.

Response of protein and urea kinetics in burn patients to different levels of protein intake.

The effects of two levels of protein intake on protein metabolism in six severely burned adult patients were studied (means of 70% BSA burned). A crossover experimental design enabled the authors to study each patient at the end of two three-day dietary regimens. All diets were isocaloric and provided approximately 25% more calories than the measured energy expenditure (means = 40.8 Kcal/kg X day). In one regimen, each patient received 2.2 g protein/kg X day, while during the other treatment period they received 1.4 g protein/kg X day. The patients were studied in the fed state and after 10 to 12 hours of fasting. Leucine kinetics were determined by means of the primed-constant infusion of [1--13C]--leucine. The authors were able to distinguish the oxidation of plasma leucine from the oxidation of leucine derived from intracellular protein at the site of the deamination of leucine (predominantly muscle) by simultaneously determining both leucine and alpha-ketoisocaproic acid enrichment. Also, rates of whole-body protein synthesis and catabolism were calculated from the leucine flux and oxidation data. Net protein synthesis was also calculated by means of another stable-isotope technique involving the infusion of [15N2]--urea. Finally, a third means of estimating net protein catabolism based on urinary N-excretion data was used at the same time that the isotopic studies were performed. The 13C leucine-data and the N-excretion data indicated that a balance between protein synthesis and catabolism could be achieved with a protein intake of 1.4 protein/kg X day. When protein intake was increased to 2.2 g protein/kg X day, neither isotopic method indicated a further beneficial effect on net protein synthesis, although the absolute rates of protein synthesis and catabolism were stimulated. The N-excretion data, on the other hand, indicated a significant improvement in net protein synthesis with higher protein intake. Regardless of the level of protein intake, the underlying alterations in protein metabolism that occurred as a response to burn injury persisted.

Isotopic analysis of leucine and urea metabolism in exercising humans.

We have used the primed constant infusion of di-[15N]urea and [1-13C]leucine to determine the effects of mild exercise (approx 30% Vo2max for 105 min) on urea production and leucine metabolism in human subjects. The oxidation of plasma leucine was distinguished from the oxidation of leucine that never entered the plasma pool ("intracellular" leucine) by means of determining the enrichment of alpha-ketoisocaproic acid (alpha-KICA). Total leucine oxidation increased from 0.38 +/0 0.05 to 1.41 +/- 0.14 micromol . kg-1 . min-1 during exercise due to increases in the oxidation of plasma leucine (150%) and intracellular leucine (600%). Plasma leucine flux decreased slightly, but not significantly (0.1 greater than P greater than 0.05), and the percent of alpha-KICA derived from plasma leucine dropped significantly (P less than 0.05) from 79.5 +/- 4.3 at rest to 62.0 +/- 5.3% over the last 30 min of exercise. Despite the increase in leucine oxidation during exercise, urea concentration and production did not change. Thus in exercise urea production does not accurately reflect all aspects of amino acid metabolism.

Leucine and urea metabolism in acute human cold exposure.

Four healthy males voluntarily underwent acute cold exposure at 10 degrees C. Metabolic rate doubled for the 100-min exposure. [1-13C]leucine and [15N2]urea were used as tracers of protein metabolism via a primed constant infusion. Total and plasma transported leucine oxidation approximately doubled, but the oxidation of leucine derived from protein in the tissue where oxidation occurred ("intracellular oxidation") did not change as it did when the same subjects underwent mild exercise. Rate of appearance of urea and leucine in plasma were not significantly different between control and cold. Although the rate of protein synthesis calculated from the leucine data did not change, the rate of catabolism increased. Net protein catabolism based on the urea data agreed well with the leucine data at rest but did not exhibit a significant increase during exposure. However, net protein catabolism based on the leucine data did increase significantly during acute cold exposure. Further, there appears to be a qualitative difference in the protein catabolism associated with the voluntary muscular activity of exercise and muscular shivering aimed at thermogenesis.