Different contribution of substrates oxidation to insulin resistance in malnourished elderly patients with cancer.

Background: The relative contribution of malnutrition and cancer to insulin resistance in elderly patients is still poorly understood.

Methods: Twenty malnourished and 15 well-nourished patients with cancer matched for age (70 +/- 0.3 versus 69 +/- 0.3 years; P = not significant), mean arterial blood pressure (104 +/- 8 versus 107 +/- 7 mm Hg; P = not significant), gender ratio (10 males/10 females versus 7 males/8 females), and sedentary life style underwent an euglycemic glucose clamp. Simultaneous infusion of 3-D-H-glucose and indirect calorimetry allowed the authors to determine glucose turnover parameters and analyze substrates oxidation.

Results: Malnourished patients displayed a reduced total body glucose metabolism (36 +/- 2 versus 31 +/- 3 mumol/kg of lean body mass x min P < 0.04) despite higher glucose oxidation. In the same group of patients, the authors demonstrated a significant increase in lipid oxidation and the lack of the inverse relationship between glucose and lipid oxidation (r = 0.07; P = not significant). Insulin infusion enhanced glucose oxidation and suppressed lipid oxidation, but such changes were at lower extent in malnourished patients.

Conclusions: Our study confirms the presence of insulin resistance in malnourished patients and demonstrates the relative contribution of substrates oxidation to the insulin resistance itself.