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 1HNMRbased 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 (C4C6) are immediately converted, whereas mediumlong-chain fatty acids (C1216) are incorporated into triglycerides and deposited in the cells. In conclusion, the present study demonstrates that 1HNMRspectroscopy is a useful method for studying the uptake of fatty acids in in vitro cells.