Energy and protein metabolism in sarcoma patients

Abstract

We have performed a series of isotopic infusions both in normal volunteers (N = 16) and in sarcoma patients (N = 7). Using the primed-constant infusion of stable or radioisotopes we have determined the rates of glucose turnover, glucose oxidation, glucose recycling, and net protein catabolism (NPC). In addition, we have measured VO2 and VCO2. The values for VCO2 and VO2 were higher in the patients than in the volunteers (mean VO2 values in volunteers and patients: 107 +/- 13 and 158 +/- 13 mumol/kg/min, respectively). The basal rate of glucose appearance in the sarcoma patients was twice the value seen in the volunteers (28.3 +/- 3.5 vs. 13.9 +/- 0.3 mumol/kg/min). Glucose infusion in the volunteers resulted in virtually total suppression of endogenous glucose production, while in the patients glucose infusion induced only a 30% suppression of endogenous glucose production (p less than 0.01). The rate of glucose clearance in the patients was approximately twice the value seen in the volunteers [5.4 +/- 1.0 vs. 2.7 +/- 0.1 mL/kg/min (p less than 0.01)]. The per cent of glucose uptake oxidized in the patients was significantly less than in the volunteers [22% vs. 36% (p less than 0.05)], and the per cent of glucose uptake that was recycled was significantly higher in the patients [55% vs. 10% (p less than 0.01)]. In addition, the basal rate of net protein loss was increased twofold in the patients [3.2 +/- 0.5 vs. 1.4 +/- 0.4 g (protein)/kg/d (p less than 0.01)], and in contrast to the situation in the volunteers there was no suppression in the rate of net protein loss when the patients were infused with glucose. The basal insulin concentration and the insulin response to glucose infusion in the patients were similar to that of the volunteers, but the plasma cortisol level was similar in volunteers and in the patients (p less than 0.05). We conclude from these studies the following: (1) Sarcoma patients have significantly elevated rates of glucose production and glucose clearance, but they have an impaired capacity to directly oxidize either endogenous or infused glucose, coupled with an increased rate of glucose recycling. (2) Sarcoma patients have an elevated metabolic rate and are catabolic. In addition, in contrast with normal volunteers, glucose infusion does not result in a suppression of protein loss.