Figure 4.

Raman microspectroscopy reveals predominance of unsaturated spectra in induced adipocytes, with heterogeneity in the unsaturation ratio for the spontaneous condition. (A) Representative Raman spectrum of saturated-rich, unsaturated-rich lipids and mixture identified by unguided hierarchical cluster analysis. (B) Loading plot PC1 indicates the discriminant peaks for saturated versus unsaturated designation, the color is associated to the attribution of specific Raman bands: saturated in blue, unsaturated in red (n = 3 independent experiments, pooled for PCA analysis). (C) PCA score plot of Raman spectra labelled according to spontaneous (orange) and induced (green) OP9-adipocytes. (D) The same PCA score plot as (C) labelled according to the assignment of Raman spectra as saturated (red) and unsaturated (blue) lipids based on the PC1 loading determined by (B) For panels C and D, each point is a single adipocyte with all its lipid droplet data points averaged. n (induced) = 138 adipocytes, 2971 spectra; n (spontaneous) = 120 adipocytes, 2944 spectra. (E) Unsaturation ratios of spontaneous and induced at adipocyte level. The unsaturation ratio of sOP9 adipocytes is not different from iOP9 adipocytes (P = 0.0855 by Mann-Whitney test).