A single peer-reviewed cell experiment traced labeled stearic acid through human liver-derived cells, mouse fibroblasts and a plant control. Only the plant cells formed detectable labeled linoleic acid. The mammalian cells made a different omega-9 fatty acid, reinforcing the importance of distinguishing molecular identities when testing whether cells can produce essential dietary fats.
A single peer-reviewed cell study found that tested mammalian cells could make a fatty acid with two double bonds, but it was not linoleic acid. The distinction addresses a biochemical question about essential omega-3 and omega-6 fats, which mammals obtain through diet. Researchers traced the products of labeled stearic acid instead of inferring a molecule’s identity from the number of double bonds alone.[1]
The experiment supplied stearic acid carrying a carbon-13 label to two mammalian systems: liver-tumor-derived human HepG2 cells and primary fibroblasts from mice, cells associated with connective tissue. White sage, Salvia apiana, provided a plant-cell control. Gas chromatography and mass spectrometry detected labeled linoleic acid in the plant cells. The isotope label allowed the investigators to identify fatty acids made from the supplied starting material under the same analytical method.[1]
Neither mammalian test system yielded detectable isotope-labeled polyunsaturated fats belonging to either the omega-3 or omega-6 family. Both formed labeled C18:2n-9, which belongs to the omega-9 family. The finding agrees with the established view that mammals cannot synthesize essential omega-3 and omega-6 fats from scratch. Its scope is the selected cultured cells: the human tumor-derived line does not represent every healthy liver cell, and the experiment was not a clinical or dietary intervention.[1]
