The effect of graded doses of insulin on peripheral glucose uptake and lactate release in cancer cachexia

With the euglycemic clamp technique, we evaluated the effects of graded doses of insulin on glucose turnover rates and forearm lactate balance in five weight-losing patients with cancer before surgery and five age- and weight-matched healthy volunteers (control subjects). Insulin was infused sequentially at increasing rates of 0.5 (low physiologic), 1.0 (high physiologic), and 4.0 (supraphysiologic) mU/kg · min for 120 minutes each. Concurrently, rates of glucose appearance and disappearance were derived from [3-³H] glucose infusion. The mean postabsorptive rate of glucose appearance in patients (2.9 ± 0.1 mg/kg · min) was significantly higher (p < 0.02) than that of control subjects (1.98 ± 0.16 mg/kg · min). Complete suppression of endogenous glucose production occurred at high physiologic insulin concentrations. With progressive insulin infusion, the rate of glucose disappearance increased to 3.6 ± 1.2, 8.7 ± 0.8, and 13.7 ± 1.1 mg/kg/min in control subjects and 2.9 ± 0.4, 5.3 ± 0.3, and 10.9 ± 0.9 mg/kg · min in patients, significantly different from that of control subjects (p < 0.05) during the intermediate (high physiologic) insulin infusion. A comparable slight increase in arterial plasma lactate concentration was observed in both groups with progressive hyperinsulinemia. Baseline peripheral lactate flux was identical in patients (-272 ± 56 nmol/100 gm · min) and in controls (-271 ± 57 nmol/100 gm · min). Progressive physiologic hyperinsulinemia resulted in significantly (p < 0.05) augmented peripheral lactate efflux in patients (-824 ± 181 nmol/100 gm · min) compared with control subjects (-287 ± 64 nmol/100 gm · min). Supraphysiologic insulin abolished this increased lactate efflux in patients. Postabsorptive rates of endogenous glucose appearance in weight-losing patients with cancer were elevated, but complete suppression was achieved with insulin concentrations in the physiologic range. Total body glucose use was diminished in these patients, consistent with a state of insulin resistance. This impaired insulin action on peripheral glucose use was associated with an increase in peripheral lactate release in patients.