Role of quercetin and caloric restriction on the biomolecular composition of aged rat cerebral cortex: An FTIR study

Aging brain is characterized by a change in biomolecular composition leading to a diverse range of neurological diseases. Anti-aging research is of current interest, to lessen the burden of age-related macromolecular damage through antioxidant supplementation and caloric restriction. However, data concerning the effect of these anti-aging regimens on age-related biomolecular changes in rat brain is still lacking. In the present study, for the first time, we employed Fourier transform infrared (FTIR) spectroscopy, to investigate the effect of quercetin, caloric restriction (CR) and combination of both on alterations in the composition of lipids and proteins of aged rat brain cerebral cortex. Aged male Wistar rats (21 months old) were divided into four groups: Control (CONT), fed pellet diet; Quercetin (QUER), fed quercetin (50 mg/kg/day); CR (caloric restriction) (fed 40% reduced CONT), and CRQ (40% CR and 50 mg/kg/day QUER). Three-month-old rats served as young control (YOUNG). Our short-term study (45 days) shows decreased band area of unsaturated lipids, decreased area ratios of olefinic/lipid and CH2 antisymmetric stretching (2925 cm(-1))/lipids in CONT group compared to young rats, suggesting age-associated lipid peroxidation in aged rats. A slight decrease in the frequency of CH2 antisymmetric mode of lipids (whereas no change in CH2 symmetric mode), but a decrease in bandwidths of both CH2 antisymmetric and symmetric modes of lipids was observed for CONT group compared to YOUNG. Further, a significant decrease in the peak area of infrared bands of proteins and an increase in the peak area of the C=O band of lipids was observed in the CONT group. Our data also show that lower levels of a-helical structures and higher levels of random coils, representing altered protein secondary structure composition in the CONT group compared to YOUNG group. Reduction in neuronal cell density and shrinked nucleus was also observed in aged rats. Increase in the accumulation of oxidative mediated damage to macromolecules and diminished antioxidant levels, could be the possible reason for the age-related alterations in the composition of lipids and proteins. However, the combination of quercetin and CR, but not either treatment alone, significantly prevented the age associated alterations in the lipid and protein profiles in the rat cerebral cortex. Further, our results help to understand the mechanism of action of antioxidants under non-restriction and CR conditions, this might help in the development of novel anti-aging treatments to ameliorate oxidative stress in age-related disorders. (C) 2019 Elsevier B.V. All rights reserved.