Food-induced changes of lipids in rat neuronal tissue visualized by ToF-SIMS imaging

Abstract

Time of flight secondary ion mass spectrometry (ToF-SIMS) was used to image the lipid localization in brain tissue sections from rats fed specially processed cereals (SPC). An IonTof 5 instrument equipped with a Bi cluster ion gun was used to analyze the tissue sections. Data from 15 brain samples from control and cereal-fed rats were recorded and exported to principal components analysis (PCA). The data clearly show changes of certain lipids in the brain following cereal feeding. PCA score plots show a good separation in lipid distribution between the control and the SPC-fed group. The loadings plot reveal that the groups separated mainly due to changes in cholesterol, vitamin E and c18:2, c16:0 fatty acid distribution as well as some short chain monocarboxylic fatty acid compositions. These insights relate to the working mechanism of SPC as a dietary supplement. SPC is thought to activate antisecretory factor (AF), an endogenous protein with regulatory function for inflammation and fluid secretion. These data provide insights into lipid content in brain following SPC feeding and suggest a relation to activating AF.

Figure 1

Optical microscopy images of freeze-dried rat brain sections brain section containing cerebellum and stem are shown in (a) control and (b) the SPC-fed group. ToF-SIMS images showing the spatial signal intensity distribution from positive ions are shown for m/z 184 (phosphocholine): (c) control and (d) the SPC-fed group; for m/z 369 (cholesterol): (e) control and (f) the SPC-fed group; and for total ions: (g) control and (h) the SPC-fed group; across an analysis area of 11 × 11 mm covering the complete tissue.

Figure 2. PCA analysis of positive mode data for the ToF-SIMS experiment for 3 rats imaging 15 brain tissues containing the cerebellum and stem regions for SPC-fed versus control samples.

(a) Score plot of the first principle component (t[1]) vs. the third principle component (t[3]) from the spectra. (b) Corresponding loading plot of the first principle component (p[1]) representing the m/z peaks with strong impact on the separation between groups.

Figure 3

PCA analysis of negative mode data for the ToF-SIMS experiment for 3 rats imaging 15 brain tissues containing the cerebellum and stem regions for SPC-fed versus control samples (a) Score plot of the first principle component (t[1]) vs. the second principle component (t[2]) from the spectra. (b) Corresponding loading plot of the first principle component (p[1]) showing the m/z peaks with strong impact on the separation between groups.

Figure 4

(a) Normalized intensity for positive species at m/z 86 (PC: C₅H₁₂N), m/z 184 (phosphatidylcholine head group) and m/z 369 (cholesterol) in control (blue) and SPC-fed (red) rat brains. (b) Normalized intensity of negative ions at m/z 140 (phosphatidylethanolamine), m/z 180 (phosphinothricin), m/z 255 (palmitic acid), m/z 281 (oleic Acid), m/z 385 (cholesterol) and m/z 429 (Vitamin E) in control (blue) and SPC-fed (red) rat brains. In both charts, the bar heights show the average value and the error bars show 95% confidence level for each lipid peak in 3 animals containing 15 brain tissues for each control and SPC-fed sample.