Effects of Low Carbohydrate High Protein (LCHP) diet on atherosclerotic plaque phenotype in ApoE/LDLR−/− mice: FT-IR and Raman imaging

Abstract

Low Carbohydrate High Protein (LCHP) diet displays pro-atherogenic effects, however, the exact mechanisms involved are still unclear. Here, with the use of vibrational imaging, such as Fourier transform infrared (FT-IR) and Raman (RS) spectroscopies, we characterize biochemical content of plaques in Brachiocephalic Arteries (BCA) from ApoE/LDLR−/− mice fed LCHP diet as compared to control, recomended by American Institute of Nutrition, AIN diet. FT-IR images were taken from 6–10 sections of BCA from each mice and were complemented with RS measurements with higher spatial resolution of chosen areas of plaque sections. In aortic plaques from LCHP fed ApoE/LDLR−/− mice, the content of cholesterol and cholesterol esters was increased, while that of proteins was decreased as evidenced by global FT-IR analysis. High resolution imaging by RS identified necrotic core/foam cells, lipids (including cholesterol crystals), calcium mineralization and fibrous cap. The decreased relative thickness of the outer fibrous cap and the presence of buried caps were prominent features of the plaques in ApoE/LDLR−/− mice fed LCHP diet. In conclusion, FT-IR and Raman-based imaging provided a complementary insight into the biochemical composition of the plaque suggesting that LCHP diet increased plaque cholesterol and cholesterol esters contents of atherosclerotic plaque, supporting the cholesterol-driven pathogenesis of LCHP–induced atherogenesis.

IR and Raman imaging of murine brains from control and ApoE/LDLR−/−mice with advanced atherosclerosis

“…2 suggest that the composition of the tissue in the region of whole white matter is similar. 23 As previously reported, 20 the cholesterol and cholesteryl esters can be differentiated mainly by the presence of bands at 1740 cm −1 , an increase in the band at 2887 cm −1 for esters, and the spectral region below 705 cm −1 , which is characteristic of pure cholesterol. To detect a greater distinction in the brain tissue components, a higher sampling density of 0.33 µm was used.…”

“…23,24 Herein, we present the results from a less invasive type of fixation. As previously reported, such a method can be applied to both of the most commonly used methods of tissue preparation ( paraffin and frozen samples).…”

Distinct Chemical Changes in Abdominal but Not in Thoracic Aorta upon Atherosclerosis Studied Using Fiber Optic Raman Spectroscopy

“…In order to exclude additional factors that could disturb the results, and because the male mice model is more stable, we used only males. The Apoe -/- /Ldlr -/- murine model developed initially by Ishibashi and coworkers [ 57 ] represents a validated model of murine atherosclerosis as shown in numerous previous studies from our group using various methodologies [ 51 , 58 , 59 , 60 ] including also Raman and IR spectroscopy [ 32 , 61 , 62 ].…”

High-definition Fourier transform infrared spectroscopic imaging of prostate tissue

“…Recent applications of Fourier transform infrared (FT-IR) imaging has proven the technique's power in potentially aiding medical diagnosis 1-4 as well as the understanding of different diseases such as diabetes 5 or atherosclerosis [6][7][8][9] . In such studies FT-IR has been able to provide sufficient contrast in terms of chemical composition of tissues for multiple purposes.…”