ALTERATIONS OF PLASMA LACTATE AND GLUCOSE-METABOLISM IN OBESE CHILDREN

Using a double stable isotope infusion method, we quantified plasma gl ucose and lactate interrelationships in five recently obese children. Compared with five age-matched controls, obese children had an similar to 50% increase of total body lactate turnover [167 +/- 20 vs. 111 +/ - 20 ISE) mg/min, P < 0.05]. The rate of lactate conversion to glucose was double the normal rate (96 +/- 21 vs. 46 +/- 10 mg/min, P < 0.05) . Increased gluconeogenesis from plasma lactate correlated with total glucose production (r = 0.74), with plasma lactate contributing to 58% of glucose production in obese children vs. 38% in normal children (P < 0.05). Conversion into glucose correlated with the rate of lactate release in the circulation (r = 0.76). In turn. the obese children con verted a larger fraction (35 +/- 2 vs. 27 +/- 2%, P < 0.02) and amount (58 +/- 10 vs. 34 +/- 5 mg/min, P < 0.05) of glucose into plasma lact ate. The amount of lactate originating from plasma glucose correlated (r = 0.70) with lipid oxidation, which was increased in the obese chil dren (58 +/- 4 vs. 23 +/- 5 mg/min, P < 0.02). Our data suggest that i ncreased gluconeogenesis from lactate is associated with increased lip id oxidation and could contribute to the progressive development of in sulin resistance and glucose intolerance in juvenile obesity.