Fructose-human serum albumin interaction undergoes numerous biophysical and biochemical changes before forming AGEs and aggregates

Abstract

Fructose is a reducing and highly lipogenic sugar that has unique metabolic effects in the liver. Non-enzymatic fructosylation of proteins generates advanced glycation end products (AGEs). Human serum albumin (HSA) may undergo fructosylation vis-à-vis AGEs formation. High fructose consumption may lead to structurally altered and functionally compromised fructosylated-HSA-AGEs, which can cause damage to hepatocytes resulting in hepatic macro- and microvesicular steatosis. In this study, HSA was incubated with varying concentrations of fructose for 10days and the induced changes were studied. Fructosylated-HSA exhibited hyperchromicity, increased AGE-specific fluorescence, quenching of tryptophan fluorescence and increased melting temperature. Nε-[carboxymethyl]-lysine (CML), was detected by liquid chromatography mass spectrometry (LC-MS). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) results showed decreased mobility in fructosylated-HSA. Perturbations in secondary and tertiary structure were revealed by fourier transform-infrared spectroscopy (FT-IR), supported by far- and near-UV circular dichroism (CD). Dynamic light scattering (DLS) and Matrix-Assisted Laser Desorption Ionization-Time of Flight (MALDI-TOF) mass spectrometry studies suggested increase in molecular mass of fructosylated-HSA. Amyloidogenic aggregates were confirmed from Congo red, Thioflavin T assay and Scanning electron microscope (SEM). These investigations confirmed the structural alterations in fructosylated-HSA and warrants further study to probe the role of fructosylated-HSA-AGEs in hepatopathy vis-à-vis fatty liver diseases.

Keywords: AGEs; Fructose; Human serum albumin.