Possible Interaction: Dexamethasone and Glutamine

“Several studies in the 1980s about the interorgan metabolism of amino acids showed that, in starvation and in the catabolic state, glutamine (GLN) is … influence of glucocorticoids on GLN release from skeletal muscle was demonstrated 1984 by Muhlbacher et al. 2 who showed that chronic administration of dexamethasone … GLN ….”

“ Dexamethasone decreased glutamine transport by 20%, but this decrease was not apparent for 48 hours.”

“ DEX did not affect EHPF or SGO, but doubled basal splanchnic AA uptake (5,446 +/- 3,635 nmol/kg.min) and increased that of Gln by 110%.”

“However, even in the total absence of glutamine, dex treatment elicited a 2.0–2.5‐fold increase in GS activity, ruling out inhibition of glutamine uptake as a mechanism for the dex‐induced increase.”

“In C2C12 myoblast cells, addition of glutamine to dexamethasone prevented the hyperexpression of myostatin induced by dexamethasone.”

“Myostatin promoter activity increased in cells exposed to dexamethasone , but this increase was partially blocked by addition of the glutamine.”

“Pair-fed rats given dexamethasone plus glutamine had significantly less reduction in body and muscle weights and lower myostatin expression when compared with those treated with dexamethasone alone.”

“ Dexamethasone treatment increased serine and glutamine levels in conditioned medium and increased glutamate induced glutamine release suggesting an upregulation of glutamine synthase activity.”

“ Dex decreased hepatic glutamine and alanine uptakes (P < 0.01) and hepatic glutamate output (P < 0.001).”

“Intravenous infusion of dexamethasone Dex ) in the fetal lamb causes a two- to threefold increase in plasma glutamine and other glucogenic amino acids and a decrease of plasma glutamate to approximately one-third of normal.”

“ Dexamethasone exposure for 18 h increased glutaminase mRNA and activity by 32 and 42%, respectively (both P< 0.05, paired t-test), associated with a small (9%) but significant increase in glutamine utilization (P<0.05).”

“Transfected cells expressed a 39-fold increase in CAT activity with dexamethasone treatment, confirming a higher level of functional receptors, but glutaminase mRNA and activity were now decreased by 34 and 32%, respectively, associated with a 15% fall in glutamine utilization after 18-h exposure to dexamethasone.”

“Four hours after dexamethasone injection, a nearly a 5-fold increase in glutamine synthetase mRNA levels in lung and muscle, as well as an approximately 2-fold increase in heart were observed.”

“The reduction in muscle glutamine concentration after dexamethasone treatment may be primarily due to a reduction in the driving force for intramuscular glutamine accumulation, i.e., in the Na+ electrochemical gradient.”