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Nutr Neurosci. 2018 Jul 21:1-14. doi: 10.1080/1028415X.2018.1501533. [Epub ahead of print]

Palmitic acid triggers inflammatory responses in N42 cultured hypothalamic cells partially via ceramide synthesis but not via TLR4.

Author information

1
a Rowett Institute, University of Aberdeen , Foresterhill, Aberdeen AB25 2ZD , UK.
2
b Institute of Medical Sciences, University of Aberdeen , Foresterhill, Aberdeen AB25 2ZD , UK.
3
c Cellular Neurobiology Group , Université du Québec , Trois-Rivières , Québec , G9A 5H7 Canada.

Abstract

A high-fat diet induces hypothalamic inflammation in rodents which, in turn, contributes to the development of obesity by eliciting both insulin and leptin resistance. However, the mechanism by which long-chain saturated fatty acids trigger inflammation is still contentious. To elucidate this mechanism, the effect of fatty acids on the expression of the pro-inflammatory cytokines IL-6 and TNFα was investigated in the mHypoE-N42 hypothalamic cell line (N42). N42 cells were treated with lauric acid (LA) and palmitic acid (PA). PA challenge was carried out in the presence of either a TLR4 inhibitor, a ceramide synthesis inhibitor (L-cycloserine), oleic acid (OA) or eicosapentaenoic acid (EPA). Intracellular ceramide accumulation was quantified using LC-ESI-MS/MS. PA but not LA upregulated IL-6 and TNFα. L-cycloserine, OA and EPA all counteracted PA-induced intracellular ceramide accumulation leading to a downregulation of IL-6 and TNFα. However, a TLR4 inhibitor failed to inhibit PA-induced upregulation of pro-inflammatory cytokines. In conclusion, PA induced the expression of IL-6 and TNFα in N42 neuronal cells independently of TLR4 but, partially, via ceramide synthesis with OA and EPA being anti-inflammatory by decreasing PA-induced intracellular ceramide build-up. Thus, ceramide accumulation represents one on the mechanisms by which PA induces inflammation in neurons.

KEYWORDS:

Ceramide; Fatty acids; Hypothalamic inflammation; Hypothalamic neurons; Toll-like receptor 4

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