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. 2012 Apr;47(4):435-42.
doi: 10.1007/s11745-012-3653-6. Epub 2012 Jan 18.

Absorption and metabolism of cis-9,trans-11-CLA and of its oxidation product 9,11-furan fatty acid by Caco-2 cells

Thorsten Buhrke  1 , Roswitha Merkel, Imme Lengler, Alfonso Lampen
Affiliations

Absorption and metabolism of cis-9,trans-11-CLA and of its oxidation product 9,11-furan fatty acid by Caco-2 cells

Thorsten Buhrke et al. Lipids. 2012 Apr.

Abstract

Furan fatty acids (furan-FA) can be formed by auto-oxidation of conjugated linoleic acids (CLA) and may therefore be ingested when CLA-containing foodstuff is consumed. Due to the presence of a furan ring structure, furan-FA may have toxic properties, however, these substances are toxicologically not well characterized so far. Here we show that 9,11-furan-FA, the oxidation product of the major CLA isomer cis-9,trans-11-CLA (c9,t11-CLA), is not toxic to human intestinal Caco-2 cells up to a level of 100 μM. Oil-Red-O staining indicated that 9,11-furan-FA as well as c9,t11-CLA and linoleic acid are taken up by the cells and stored in the form of triglycerides in lipid droplets. Chemical analysis of total cellular lipids revealed that 9,11-furan-FA is partially elongated probably by the enzymatic activity of cellular fatty acid elongases whereas c9,t11-CLA is partially converted to other isomers such as c9,c11-CLA or t9,t11-CLA. In the case of 9,11-furan-FA, there is no indication for any modification or activation of the furan ring system. From these results, we conclude that 9,11-furan-FA has no properties of toxicological relevance at least for Caco-2 cells which serve as a model for enterocytes of the human small intestine.

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Figures

Fig. 1
Fig. 1
Structures of LNA, c9,t11-CLA and 9,11-furan-FA
Fig. 2
Fig. 2
Viability of Caco-2 cells. Cells were treated with various concentrations of (a) LNA, (b) c9,t11-CLA, and (c) 9,11-furan-FA for 48 h. Cellular viability was determined using the CTB assay and expressed as percentages of negative control which was exposed to medium containing 0.1% DMSO (set as 100%). Data are expressed as the means ± SD; n = 5
Fig. 3
Fig. 3
Oil-Red-O staining. Caco-2 cells were incubated with LNA, c9,t11-CLA, or 9,11-furan-FA for 48 h. Oil-Red-O staining was conducted as described in the methods section. Red staining is indicative of lipid droplets (color figure online)
Fig. 4
Fig. 4
Mass spectra of (a) 9,11-furan-FA and of (b) the metabolite that was formed upon incubation of Caco-2 cells with 9,11-furan-FA. The masses of the major cleavage products are assigned to the structures of the respective molecule
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