High-throughput FTIR spectroscopy of intact HepG2 cells reveals additive and non-additive effects of individual fatty acids when given as mixtures

In the present study we investigated the ability of high-throughput FTIR spectroscopy in combination with multivariate data analysis to reveal if any combinatory effects of fatty acids in mixture are present in liver HepG2 cell cultures after three days of exposure. For this investigation we used an experimental mixture design containing three different octadecenoic acids (oleic acid: C18:1 cis- 9, elaidic acid: C18:1 trans- 9 and vaccenic acid: C18:1 trans- 11) of a total concentration of 100 μM. The results obtained revealed both additive and non-additive effects of individual fatty acids when combined in mixtures. Furthermore, we demonstrate by use of scanning electron microscopy that cells are preserved as intact structures ensuring that FTIR measurements are obtained on whole cell keeping cell compounds in their natural surroundings during measurements.

NMR-based metabolomics reveals that conjugated double bond content and lipid storage efficiency in HepG2 cells are affected by fatty acid cis/trans configuration and chain length

In the present study the metabolic response to various fatty acids was investigated in HepG2 cells by using a (1)H NMR-based approach. To elucidate the effect of cis/trans configuration, the cells were exposed to either oleic acid (C18:1 cis-9), elaidic acid (C18:1 trans-9), vaccenic acid (C18:1 trans-11), linoleic acid (C18:2), or palmitic acid (C16:0), and multivariate data analysis revealed a strong effect of fatty acid on the lipophilic metabolite fraction. Inspection of the spectra revealed that the difference between the observed responses could be ascribed to the appearance of resonances from conjugated double bonds (5.65, 5.94, and 6.28 ppm) in cells exposed to vaccenic acid, revealing that vaccenic acid upon uptake by the HepG2 cells is converted into a conjugated fatty acid. Upon exposure of the HepG2 cells to either butyric acid (C4:0), caproic acid (C6:0), lauric acid (C12:0), myristic acid (C14:0), or palmitic acid (C16:0), an effect of fatty acid length was also evident, and data indicated that short-chain fatty acids (C4-C6) are immediately converted, whereas medium-long-chain fatty acids (C12-16) are incorporated into triglycerides and deposited in the cells. In conclusion, the present study demonstrates that (1)H NMR spectroscopy is a useful method for studying the uptake of fatty acids in in vitro cells.