Poster Topical Area: Energy and Macronutrient Metabolism
Location: Hall D
Poster Board Number: 493
Excess dietary saturated fat consumption has been linked to promotion or exacerbation of cardiometabolic diseases and other conditions associated with chronic low-grade inflammation. Based primarily on cell culture experiments, saturated fatty acids (SFAs) are proposed to promote inflammation and contribute to metabolic dysfunction through toll-like receptor activation. Studies are often complicated by a requirement for carriers (e.g. BSA) or solvents (e.g. ethanol) to increase SFA solubility, yet BSA can itself induce inflammation and ethanol is a cytotoxin. Objective: To ascertain if these factors influence SFA-associated inflammation, we measured responses of RAW264.7 monocyte/macrophages and C2C12 myotubes to various BSAs, ethanol and cyclodextrin (an alternative to BSA).
Methods: The inflammatory responses of RAW264.7 macrophages and C2C12 myotubes were determined in response to various lots and concentrations of commercially available low-endotoxin, fatty acid free BSA (0.33% to 2% wt/vol), multiple concentrations of ethanol (0.06% to 1% vol/vol), and cyclodextrins (0.3 – 6.0 mM). The cellular response to palmitic acid (PA) (200 – 600 µM) was assessed.
Results: Low-endotoxin BSA preparations activated, whereas 0.5 - 1.0% ethanol inhibited, RAW264.7 TNF-a release. Ethanol modestly increased IL-6 secretion in C2C12 myotubes. Cyclodextrins were tested as an alternative carrier of PA, but its usefulness in cell culture was limited due to toxicity and solubility issues. Using a lower-inflammation lot of BSA and no ethanol, ~24 hr sodium PA treatment (up to 600 µM) failed to trigger RAW264.7 TNF-a release, and in fact significantly dampened BSA-induced inflammation by >50%. In C2C12 myotubes, only high PA concentrations (500-600 µM) elicited IL-6 secretion (> 2.5-fold increase); acute PA (200 or 500 µM) did not activate MAP-kinase pathways above that of fresh media alone.
Conclusion: These results highlight the importance of experimental conditions in studies exploring SFA inflammation effects. The limited (or even anti-inflammatory) effects of PA that we observed indicate that immunomodulatory effects of SFAs are context-specific. Thus, caution is needed when interpreting the literature related to putative pro-inflammatory effects of SFA.
Senior Research Associate
Arkansas Children’s Nutrition Center
Little Rock, Arkansas