FTIR microspectroscopy reveals fatty acid-induced biochemical changes in C. elegans

Fourier transform infrared microspectroscopy (FTIR) is a promising method for the analysis of biological samples. Recent studies reported that FTIR imaging allows determination of the distribution of several biomolecules in a sample with no staining or extraction. In this study, FTIR was used to monitor biochemical changes in C. elegans nematodes cultured in nematode maintenance media (CeMM) without supplementation and with supplementation with either a long chain polyunsatured omega 3 fatty acid, eicosapentaenoic acid (EPA) or a saturated fatty acid, palmitic acid (PA) at 100 μM. EPA is an omega 3 fatty acid with documented health benefits while PA is generally consumed in diets. Worms were placed on BaF ₂ slides, and FTIR spectra were collected from single worms in transmission mode using a focal plane array detector. Principal component analysis grouped the FTIR spectra into three clusters corresponding to spectra of worms cultured with no supplementation, worms cultured with supplementation with EPA, and worms cultured with supplementation with PA. The major differences between the FTIR spectra reside in the vibrations corresponding to unsaturated fatty acids (3008 cm ⁻¹ ), lipids (2928, 2848, and 1744 cm ⁻¹ ), and proteins (1680, 1648, and 1515 cm ⁻¹ ). This indicates that supplementation with EPA or PA leads to biochemical alterations related to unsaturated fatty acids, lipids, and proteins. Furthermore, supplementing mutant strains (tub-1 and fat-3) CeMM with PA resulted in the appearance of the vibration 3008 cm ⁻¹ , an increase in the intensity of the vibration 1744 cm ⁻¹ , and a new vibration at 1632 cm ⁻¹ , which is assigned to the amide I of β-pleated sheet component of proteins, in the spectra of tub-1 and fat-3 mutant strains. The results illustrated the potential use of FTIR alongside other techniques such as gas chromatography and staining techniques to investigate lipid metabolism and fat accumulation as well as induced changes in protein structures.