Poster Topical Area: Energy and Macronutrient Metabolism

Location: Hall D

Poster Board Number: 493

P10-094 - Do saturated fatty acids truly activate inflammation? Experimental confounders and context-specificity

Monday, Jun 11
8:00 AM – 3:00 PM

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).
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.
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.
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.

Funding Source:

ARS 6026-51000-010-05S

CoAuthors: Michael Blackburn – Arkansas Children’s Nutrition Center; Sean Adams – Arkansas Children’s Nutrition Center

Kikumi D. On-Moore

Senior Research Associate
Arkansas Children’s Nutrition Center
Little Rock, Arkansas