Agnieszka Szkudlarek

Competitive binding of glipizide and losartan to human serum albumin in diabetes therapy: spectroscopic studies

2024-12-02

Subject of study. The increasing prevalence of chronic conditions such as hypertension and type 2 diabetes has contributed to the widespread use of polypharmacotherapy. This strategy requires a comprehensive understanding of drug interactions and their biochemical effects, especially when these drugs interact with modified biological molecules, such as glycated human serum albumin (gHSA). gHSA is formed through the non-enzymatic glycation of albumin, and its levels are elevated in patients with diabetes. Due to its altered structure, biological function, and physicochemical properties, gHSA is clinically significant and remains an essential subject of scientific research.

The goal of the study. This study aims to estimate the binding strength of selected drugs used in combination therapy for chronic diseases, namely losartan (LOS, a drug used in the treatment of primary hypertension and diabetic nephropathy) and glipizide (GLP, a second-generation antihyperglycemic drug) with albumin whose structure has been destabilized by glycation under in vitro conditions and to determine their competition in binding to the macromolecule.

Materials and methods. The analysis of the competition between GLP and LOS for the binding site in unmodified (HSA) and galactose-glycated (gHSAGAL ) albumin was conducted in binary (GLP-HSA, GLP-gHSAGAL , LOS-HSA, LOS-gHSAGAL ) and ternary systems (GLP-HSA-LOSconst , GLP-gHSAGAL-LOSconst , LOS-HSA-GLPconst , LOS-gHSAGAL-GLPconst ). The Stern-Volmer method was applied to quantitatively evaluate quenching parameters, while the Klotz and Hill methods provided insights into association constants and coefficients of cooperativity Circular dichroism (CD) was used for further structural analysis of the complexes formed.

Results. Fluorescence quenching analyses revealed that LOS and GLP have higher binding affinity for non-glycated than glycated. Glycation altered the microenvironment around critical amino acid residues, reducing drug accessibility and impacting complex stability, as indicated by lower Stern-Volmer (KSV ) and association constants (Ka ). In ternary systems, the presence of a second drug appears to mitigate the effects of glycation. The quenching parameters of the LOS-HSA-GLPconst and LOS-gHSAGAL-GLPconst complexes are nearly identical, implying that GLP may induce conformational changes in gHSAGAL restoring macromolecule affinity similar to that of HSA. CD spectra indicated that neither glycation nor the presence of LOS significantly affects the secondary structure of HSA, which may indicate that differences in drug binding result from local conformational shifts rather than global structural modifications induced by the glycation process.

Conclusions. Spectroscopy enables the quantitative assessment of binding property changes in albumin induced by glycation and the determination of parameters that define ligand-albumin interaction strength in polypharmacotherapy, which is helpful at various stages of diagnostic research for multiple conditions associated with conformational changes in albumin, including diabetes and its complications, or metabolic disorders. The conducted in vitro studies provide insights into changes that occur in vivo during the binding and transport of drugs by albumin in individuals affected by chronic diseases and in the elderly.

Keywords: polypharmacotherapy, albumin glycation, spectroscopic analysis, drug-albumin interactions, diabetes therapy.

© Farm Pol, 2024, 80(7): 501–512