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Glucagon increases glutamine uptake without affecting glutamine release in humans
A Battezzati1, D C Simonson, L Luzi
1Department of Medicine, Brigham and Women's Hospital, Boston, MA, USA.
Metabolism: Clinical and Experimental
|June 17, 1998
Summary
Glucagon temporarily raises blood glucose by increasing glucose production. However, it also decreases amino acids like glutamine and leucine, indicating it can contribute to protein breakdown during high glucagon levels.
Area of Science:
- Metabolic regulation
- Hormonal signaling
- Amino acid metabolism
Background:
- Glucagon is known to cause hyperglycemia and hypoaminoacidemia.
- The precise mechanisms underlying these effects remain unclear.
- Understanding glucagon's role is crucial for metabolic research.
Purpose of the Study:
- To investigate the kinetic effects of glucagon on glucose, glutamine, and leucine metabolism.
- To elucidate the mechanisms behind glucagon-induced hyperglycemia and hypoaminoacidemia.
- To determine glucagon's impact on protein catabolism.
Main Methods:
- Utilized pancreatic clamp studies in seven healthy subjects.
- Administered octreotide, insulin, and glucagon infusions over seven hours.
- Infused stable isotopes ([6,6-(2)H2]glucose, [2-(15)N]glutamine, 2H5-phenylalanine, 2H3-leucine) to measure substrate kinetics.
Main Results:
- Glucagon transiently increased glucose production and blood glucose levels.
- Glucagon significantly decreased glutamine concentrations by increasing uptake over release.
- Glucagon led to a small increase in proteolysis and decreased leucine concentrations, particularly at higher infusion rates.
Conclusions:
- Glucagon promotes gluconeogenic substrate uptake but not release, explaining transient hyperglycemia.
- Physiological hyperglucagonemia contributes to protein catabolism through glutamine depletion.
- These findings clarify glucagon's complex role in glucose and amino acid homeostasis.