Exogenous Fatty Acids Are the Preferred Source of Membrane Lipids in Proliferating Fibroblasts

Abstract

Summary Cellular proliferation requires formation of additional cellular membrane material, and the current thinking in the field is that lipids required for this new membrane formation are mostly synthesized de novo. Here we measured the contribution of de novo lipid synthesis in proliferating and contact-inhibited fibroblasts and find that proliferating fibroblasts prefer exogenous palmitate over de novo synthesis. We determined that when exogenous palmitate is provided in culture media at physiological concentrations, de novo synthesis accounts for only ~10% of intracellular palmitate in proliferating fibroblasts, as well as HeLa and H460 lung cancer cells. Blocking fatty acid uptake decreased the rate of fibroblast, HeLa, and H460 cell proliferation, while supplementing media with exogenous palmitate resulted in decreased glucose uptake and rendered cells less sensitive to glycolytic inhibition. Thus, our results suggest that cells scavenging exogenous lipids may be less susceptible to both glycolytic and lipogenic inhibitors.

Analysis of Mammalian Cell Proliferation and Macromolecule Synthesis Using Deuterated Water and Gas Chromatography-Mass Spectrometry

“…In fact, in the case of the SKCO1 cancer cell line, the vast majority (~78%) of intracellular palmitate was exogenously derived. This capacity to use exogenous extracellular fatty acids for complex lipid synthesis has also been recently demonstrated by others in a range of rapidly dividing cell lines in vitro [58]. Conversely, in our predominantly non-dividing C2C12 myotube cultures, the reliance on the DNL pathway was relatively high (~77% palmitate was ‘self-made’), thus indicating the reliance on the DNL pathway is unlikely related to cell proliferation.…”

Physiologic Medium Rewires Cellular Metabolism and Reveals Uric Acid as an Endogenous Inhibitor of UMP Synthase

“…Efforts have been made to adjust the concentrations of media components, usually one or several nutrients at a time, to better reflect physiologic conditions (Birsoy et al, 2014; Favaro et al, 2012; Kamphorst et al, 2015; Pan et al, 2016; Schug et al, 2015; Tardito et al, 2015; Yao et al, 2016). Most such modified media not only contain other nutrients at non-physiological levels, but also lack defined concentrations of many metabolites now known to be present in human plasma.…”

The redox requirements of proliferating mammalian cells

“…A large fraction of cellular lipids are derived from the extracellular environment (39,54). De novo lipid synthesis depends on a source of NADPH, and potentially also on NAD + , but utilization of exogenous lipids allows cells to circumvent these costs (Fig.…”