Inhibition potential of glimepiride (gli) towards important UDP-glucuronosyltransferase (UGT) isoforms in human liver

The aim of the present study was to investigate the inhibitory potential of glimepiride towards important UDP-glucuronosyltransferase (UGT) isoforms in human liver, which play a key role in the elimination of drugs. The recombinant UGT enzymes were used as enzyme source, and a nonspecific substrate 4-methylumbelliferone (4-MU) was utilized as substrate. The results showed that 100 μM of glimepiride inhibited UGT1A1, UGT1A3, UGT1A6, UGT1A9, UGT2B7 and UGT2B15 by 54.7%, 43.1%, 100%, 70.5%, 32.7 and 37.2%, respectively. Given that glimepiride exhibited strong inhibition towards UGT1A6, further inhibitory kinetic behaviour was determined. Glimepiride exerted concentration-dependent inhibition towards UGT1A6. Both Dixon and Lineweaver-Burk plots demonstrated that inhibition of UGT1A6 was best fit for noncompetitive inhibition type, and the inhibition kinetic parameter (Ki) was calculated to be 59.8 μM. Given that UGT1A6 plays a key role in detoxification of many drugs, more attention should be given when glimepiride was co-administered with the drugs mainly undergoing UGT1A6-mediated metabolism.