Insulin detemir (IDt) is long-acting insulin whose protraction mechanism is based on a covalently attached fatty acid to an insulin molecule. Utilizing the high affinity of fatty acids towards human serum albumin (HA), the modified detemir molecule binds with good affinity to HA, which functions as a reservoir that leads to a slow and prolonged release of insulin. However, questions were raised over potential interactions between other drugs and IDt through competitive binding on the binding site(s) of HA. In a previous study, concomitant use of esomeprazole (Esom) and erythromycin resulted in severe hypoglycemia, and thus: the drugs including Esom were suggested as enhancers of IDt action through displacing it from its binding site on HA. To further study this possibility, studies utilizing different techniques including, semipermeable membrane dialysis, capillary electrophoresis, UV,NMR spectroscopy, and molecular docking were carried out. Results from various techniques supported the simultaneous binding of Esom along with IDt to HA (i.e., binding in two different sites without signs of competition between the two). Moreover, capillary electrophoresis suggested an increase in the binding affinity of Esom to HA in the presence of IDt (1.9 × 103 Vs 2.7 × 104M-1). Perhaps most interesting was the observation that Esom could bind directly to IDt which was evidenced by all the employed techniques. Direct binding of Esom to IDt, might explain the enhancement in insulin action associated with the concomitant use of Esom. Therefore, Esom might represent a leading insulin-sensitizing compound that might lead to more effective insulin enhancing and less unwanted effects.
Keywords: Albumin; Detemir; Esomeprazole; Insulin; Levemir; Molecular docking.
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