PARENTERAL GLUTAMINE INFUSION ALTERS INSULIN-MEDIATED GLUCOSE-METABOLISM

Background: Glutamine is a conditionally essential amino acid that is critical for many basic cellular processes. Its supplementation has be en found to be beneficial during several critical illnesses. This stud y examines the effects of increased glutamine availability on insulin- mediated glucose homeostasis in vivo in multicatheterized conscious ca nines (n = 5). Methods: Two weeks before the study, catheters were pla ced in the femoral artery and the portal, hepatic, femoral, and renal veins for blood sampling and in the splenic vein for intraportal infus ion of insulin and glucagon. Doppler probes were placed to measure blo od flow The metabolic study consisted of equilibration, basal, and exp erimental periods during which [3-H-3]glucose was infused to measure g lucose kinetics. During the 5-hour experimental period, a hyperinsulin emic-euglycemic clamp was performed by infusing somatostatin, basal gl ucagon, fivefold basal insulin, and glucose to maintain euglycemia. Th e experimental period was divided evenly into two subperiods performed in random order: (1) IV glutamine infusion (0.72 mmol kg(-1) h(-1)) a nd (23 IV saline infusion. Results: With glutamine, the glucose requir ed to maintain euglycemia was increased 46% over saline (6.8 +/- 1.0 t o 9.9 +/-. 1.7 mg kg(-1) min(-1)). In addition, whole-body glucose pro duc tion and utilization were increased by 1.4 and 4.6 mg kg(-1) min(- 1), respectively. Finally, the increase in whole-body glucose utilizat ion as manifested by increased hepatic and hindlimb glucose utilizatio n. Conclusions: Increased glutamine availability blunted insulin's act ion on glucose production and enhanced insulin-mediated glucose utiliz ation with the changes in utilization being threefold greater than the changes in production. Thus parenteral glutamine has potential benefi t as a nutrient adjuvant during clinical cal situations associated wit h insulin resistance.