ENDOGENOUS GLUCOSE-PRODUCTION, GLUCONEOGENESIS AND LIVER-GLYCOGEN CONCENTRATION IN OBESE NONDIABETIC PATIENTS

Resting, post-absorptive endogenous glucose production (EGP), fraction al gluconeogenesis and liver glycogen concentration were assessed in 6 lean and 5 obese non-diabetic subjects undergoing elective abdominal surgery. During the 2 days preceding these measurements, 0.3 g/day U-C -13 glucose had been added to their usual diet to label their endogeno us glycogen stores. On the morning of day 3, EGP was measured with 6,6 -H-2 glucose. Their endogenous C-13 glycogen enrichment was calculated from (CO2)-C-13 and respiratory gas exchanges. Fractional gluconeogen esis was assessed as 1-(C-13 glucose/C-13 glycogen). 100. EGP was simi lar in lean subjects (113 +/- 5 mg/min) and in obese subjects (111 +/- 6). Fractional gluconeogenesis was higher in obese (59 +/- 10%) than in lean subjects (29 +/- 8%). However, overall EGP remained constant d ue to a decrease in glycogenolysis. Since an increased gluconeogenesis and a decreased glycogenolysis may both contribute to increase liver glycogen concentration in obesity, hepatic glycogen concentrations wer e assessed in hepatic needle biopsies obtained during surgery. Hepatic glycogen concentrations were increased in obese patients (515 +/- 38 mg/g protein) compared to lean subjects (308 +/- 58, p < 0.05). It is concluded that in obese patients: a) fractional gluconeogenesis is inc reased; b) overall EGP is unchanged due to a proportional inhibition o f glycogenolysis; c) liver glycogen concentration is increased.