Glucose fluxes and oxidation after an oral glucose load in patients with non-insulin-dependent diabetes mellitus of variable severity.

The relative contribution of liver and peripheral tissues to the postprandial glucose response has been examined in 19 obese non-insulin-dependent diabetes mellitus (NIDDM) patients and 11 matched nondiabetic control subjects during a 5-hour oral glucose tolerance test (OGTT) performed with a load of 75 g, corresponding to approximately 67 g/1.73 m2. A dual-tracer technique was used to measure exogenous and endogenous glucose fluxes separately. Glucose oxidation was measured by indirect calorimetry. Diabetic patients were subdivided into two subgroups designated as "mild" (n = 7) and "severe" (n = 12) NIDDM according to postabsorptive glucose concentration with a cut-off point of 140 mg/dL. In the basal state, glucose concentrations averaged 99, 117, and 194 mg/dL, respectively, in control subjects and in the two diabetic subgroups, but insulin concentrations were not significantly different between groups. In comparison to control subjects, the basal hyperglycemia of mildly diabetic patients was entirely caused by a reduced metabolic clearance rate (118 v 144 mL/min; P < .05), whereas in severely diabetic patients basal hyperglycemia resulted from a combination of increased hepatic glucose output (187 v 139 mg/min; P < .001) and decreased metabolic clearance rate (97 v 144 mL/min; P < .001). A similar situation prevailed during the initial 2 hours after glucose ingestion. In patients with mild NIDDM, glucose concentration increased by 121 +/- 10 mg/dL as compared with 36 +/- 7 mg/dL in control subjects (P < .001).(ABSTRACT TRUNCATED AT 250 WORDS)