Possible Interaction: Glucagon and Glutamine

“ Glucagon plays an essential role in robust feedback regulation between the liver and α‐cells, and exerts suppressive or static effects on the plasma concentration of amino acids, especially glutamine.”

“Thereby, “glutaminostatin” might be an alternative name in recognition of another facet of glucagon as a suppressor of plasma glutamine levels.”

“Now, a new study reports that elevated levels of glucagon promote the release of glutamine from the liver and increase gluconeogenesis.”

“ Glutamine stimulated glucagon secretion in all 3 study groups.”

“ Glucagon is important to this response because it increases glutamine uptake.”

“ Glucagon decreased the leucine concentration (-11% +/- 3% in study 2 v study 0, P < .02) and caused a small increment in proteolysis (+6% in study 2 v study 0, P < .01) that was related to the decrement in glutamine concentrations.”

“ Glucagon … glutamine concentration (-10% +/- 2% and -22% +/- 2% in studies 1 and 2 v study 0, P < .05), because glutamine uptake became greater than glutamine release (… in study 0 to -8.1 +/- 1.1 and -13.6 +/- 1.0 micromol/kg/h in studies 1 and 2, P < .01).”

“ Glucagon significantly stimulated the uptake of 15N-labeled glutamine and its metabolism via phosphate-dependent glutaminase (PDG) to form U m+1 andU m+2 (urea containing one or two atoms of15N).”

“The activation of both enzymes by glutamine was antagonized by the addition of raffinose to prevent cell swelling, or by glucagon and microcystin.”

“Dexamethasone, insulin and glucagon each stimulated glutamine uptake about 2-fold in cultures maintained in W/AB 77 medium, while the combination of dexamethasone with either glucagon or insulin resulted in a 3-4-fold increase.”

“ Glutamine significantly enhanced glucagon release from 297 +/- 54 to 528 +/- 53 pg/micrograms DNA/h in normal islets and from 553 +/- 31 to 806 +/- 50 pg/micrograms DNA/h in A-cell rich islets.”

“Glutamine synthetase flux was slightly increased by glucagon at portal glutamine concentrations of about 0.2-0.3 mM, but was strongly inhibited above 0.6 mMs.”