Application of FTIR imaging to detect dietary induced biochemical changes in brown and white adipocytes

Fourier Transform Infrared microspectroscopy Imaging (FTIR imaging) has powerful advantages when used as a complementary technique to histopathological investigations. The common histopathological investigations use a number of chemical fixatives and deparaffinizing agents that alter lipid profiles of biological tissues, particularly in lipid-rich adipose tissues. An infrared image is made of a multitude of pixels. For each pixel, identified by its (x,y) coordinates, corresponds an FTIR spectrum that reveals the chemical composition at this specific location. As a result, it allows biochemical analysis in selective locations within samples. Moreover, functional group distribution maps can be used as a staining free technique for spatial characterization of different biomolecules. Though FTIR imaging has been reported as a powerful approach to characterize adipose tissues, the biochemical heterogeneity within adipose tissues has not been acknowledged. This study shows relative changes in brown and white adipose tissues of mice due to consumption of high-fat diet. In particular, we report cryo-sectioning of adipose tissues, image acquisition, and different image analysis methods to evaluate dietary induced changes in lipids stored in brown and white adipocytes. Since biochemical changes in adipocytes constitute an important component in obesity investigations, this study shows the potential use of FTIR imaging to compare relative biochemical changes associated with dietary interventions.