Fructose and methylglyoxal-induced glycation alters structural and functional properties of salivary proteins, albumin and lysozyme

PLoS One. 2022 Jan 21;17(1):e0262369. doi: 10.1371/journal.pone.0262369. eCollection 2022.

Abstract

Glycation process refers to reactions between reduction sugars and amino acids that can lead to formation of advanced glycation end products (AGEs) which are related to changes in chemical and functional properties of biological structures that accumulate during aging and diseases. The aim of this study was to perform and analyze in vitro glycation by fructose and methylglyoxal (MGO) using salivary fluid, albumin, lysozyme, and salivary α-amylase (sAA). Glycation effect was analyzed by biochemical and spectroscopic methods. The results were obtained by fluorescence analysis, infrared spectroscopy (total attenuated reflection-Fourier transform, ATR-FTIR) followed by multivariate analysis of principal components (PCA), protein profile, immunodetection, enzymatic activity and oxidative damage to proteins. Fluorescence increased in all glycated samples, except in saliva with fructose. The ATR-FTIR spectra and PCA analysis showed structural changes related to the vibrational mode of glycation of albumin, lysozyme, and salivary proteins. Glycation increased the relative molecular mass (Mr) in protein profile of albumin and lysozyme. Saliva showed a decrease in band intensity when glycated. The analysis of sAA immunoblotting indicated a relative reduction in intensity of its correspondent Mr after sAA glycation; and a decrease in its enzymatic activity was observed. Carbonylation levels increased in all glycated samples, except for saliva with fructose. Thiol content decreased only for glycated lysozyme and saliva with MGO. Therefore, glycation of salivary fluid and sAA may have the potential to identify products derived by glycation process. This opens perspectives for further studies on the use of saliva, an easy and non-invasive collection fluid, to monitor glycated proteins in the aging process and evolution of diseases.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Albumins / analysis
  • Albumins / chemistry
  • Female
  • Fructose / analysis*
  • Glycation End Products, Advanced / analysis
  • Glycation End Products, Advanced / metabolism*
  • Glycosylation
  • Healthy Volunteers
  • Humans
  • Male
  • Muramidase / analysis
  • Muramidase / chemistry
  • Oxidative Stress
  • Pyruvaldehyde / analysis*
  • Saliva / chemistry
  • Salivary Proteins and Peptides / metabolism
  • Spectrometry, Fluorescence

Substances

  • Albumins
  • Glycation End Products, Advanced
  • Salivary Proteins and Peptides
  • Fructose
  • Pyruvaldehyde
  • Muramidase

Grants and funding

M.Y.M and D.C.C. received graduate fellowships from Research Support Foundation of the State of Minas Gerais (FAPEMIG, http://www.fapemig.br/pt/), A.B.J. and J.S.Q. received graduate fellowships from Coordination for the Improvement of Higher Education Personnel (CAPES, https://www.gov.br/capes/pt-br). F.S.E. and R.S.S. received financial support of National Institute of Science and Technology in Theranostic and Nanobiotechnology (INCT-TeraNano, http://www.teranano.ufu.br/). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.