The influence of diabetes on atherosclerosis and amyloid fibril formation of coronary arteries. A FT-IR spectroscopic study

E. Kotoulas, I. Mamarelis, E. Koutoulakis, M. Kyriakidou, V. Mamareli, O. Tanis, E. Malesiou, T. Theophanides, J. Anastassopoulou



In the present study the ATR-FT-IR (Attenuated total reflection Fourier transform infrared) spectroscopy was used to investigate 54 biopsies from atheromatic coronary arteries of patients who had elevated serum glucose. Comparison of FT-IR spectra among insulin-dependent patients and patients who were on oral hypoglycemic drugs treatment and patients with normal serum glucose showed that insulin-dependent diabetic patients pronounced changes across the absorption infrared spectral range 4,000-400 cm-1. The increase of the intensity of the characteristic stretching vibrations of antisymmetric (vasCH2) and symmetric (vsCH2) methylene groups indicates the increasing of lipophilic environment of the membranes. This finding is attributed to the damage on the membrane induced by free radicals produced during oxidative stress especially in diabetic patients. The new band at 1,744 cm-1 is assigned to aldehyde C=O vibration mode and the intensity is related to LDL cholesterol in serum of the patients. The appearance of a new band at 1,728 cm-1 only in the spectra of insulin-dependent patients, is attributed to influence of keto groups of cardiolipin due to atherosclerosis. Shifts to lower frequencies of the stretching vibration absorptions of amide I and amide II modes of proteins indicate that protein folding changed from a-helix to random coil and β-sheet configuration. The most significant changes were observed in the region 1,200-1,000 cm-1, where the vibration modes of C-O-C groups of the sugars and C-O-P of DNA and phospholipids absorb. SEM analysis showed the production of aggregates as a result of the protein amyloid formation and the increased lipophilic environment, in agreement with FT-IR spectroscopic data. The changes were related to clinical history of the patients and were more pronounced in insulin-dependent diabetic patients. The presence in the FT-IR spectra of cardiolipin vibrations in insulin dependent diabetic patients needs more investigation.

Keywords: Coronary arteries, Atherosclerosis,Amyloid proteins,Cardiolipin, insulin-dependent patients, Fourier Transform Infrared spectroscopy, Scanning Electron Microscopy