Raman Study on Lipid Droplets in Hepatic Cells Co-Cultured with Fatty Acids

Abstract

The purpose of the present study was to investigate molecular compositions of lipid droplets changing in live hepatic cells stimulated with major fatty acids in the human body, i.e., palmitic, stearic, oleic, and linoleic acids. HepG2 cells were used as the model hepatic cells. Morphological changes of lipid droplets were observed by optical microscopy and transmission electron microscopy (TEM) during co-cultivation with fatty acids up to 5 days. The compositional changes in the fatty chains included in the lipid droplets were analyzed via Raman spectroscopy and chemometrics. The growth curves of the cells indicated that palmitic, stearic, and linoleic acids induced cell death in HepG2 cells, but oleic acid did not. Microscopic observations suggested that the rates of fat accumulation were high for oleic and linoleic acids, but low for palmitic and stearic acids. Raman analysis indicated that linoleic fatty chains taken into the cells are modified into oleic fatty chains. These results suggest that the signaling pathway of cell death is independent of fat stimulations. Moreover, these results suggest that hepatic cells have a high affinity for linoleic acid, but linoleic acid induces cell death in these cells. This may be one of the causes of inflammation in nonalcoholic fatty liver disease (NAFLD).

Analytical methods used for the characterisation of specific features of biological tissues related with obesity: A review

“…The Raman spectroscopy was also used to investigate molecular compositions of lipid droplets changing in live hepatic cells stimulated with major fatty acids in the human body, i.e. palmitic, stearic, oleic and linoleic acids [96]. Majka et al [97] developed a novel strategy of studying perivascular adipose tissue in human vessels with the application of fiberoptic Raman spectroscopy and spectral modelling.…”

Palmitic Acid Inhibits Cell Proliferation and Tumor Growth of Endometrial Cancer In Vitro and In Vivo

“…Similarly, treatment of HepG2 cells with 200 μM PA for 24 hours resulted in the formation of LDs and stimulated mitochondrial oxidative metabolism (78). Interestingly, Raman microscopic observations found that the average number and size of LDs in PA-treated cells were lower than those LDs in the cells treated with other FAs, suggesting that FA types may have varying influences on the formation of LDs (79). Inhibition of TAG synthesis by targeting DGAT1 and DGAT2 with specific small inhibitors effectively depleted the formation of LDs and had differential effects on cell growth depending on the type of FA in glioma cells (35,80).…”

Palmitic Acid Exerts Anti-Tumorigenic Activities by Modulating Cellular Stress and Lipid Droplet Formation in Endometrial Cancer

“…Similarly, treatment of HepG2 cells with 200 µM PA for 24 h resulted in the formation of LDs and stimulated mitochondrial oxidative metabolism [71]. Interestingly, Raman microscopic observations found that the average number and size of LDs in PA-treated cells were lower than those LDs in cells treated with other FAs, suggesting that FA types may have varying influences on the formation of LDs [72]. Inhibition of TAG synthesis by targeting DGAT1 and DGAT2 with specific small inhibitors effectively depleted the formation of LDs and had differential effects on cell growth depending on the type of FA in cancer cells [38,73,74].…”