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Direct retroconversion of dietary trans-vaccenic acid to trans-palmitoleic acid: proof of concept and quantification in both cultured rat hepatocytes and pregnant rats

Abstract : According to epidemiological data, circulating trans-palmitoleic acid (TPA, C16:1 n-7 trans) is associated with a lower risk of metabolic syndrome. Since humans are not able to endogenously synthesise trans fatty acids, nor can they rely on a high TPA intake (0.03% of total fatty acids of cow’s milk), it was proposed that circulating TPA comes from direct retroconversion of dietary trans-vaccenic acid (TVA, C18:1 n-7 trans). Therefore, this study aimed at demonstrating the existence of this pathway. Rat hepatocytes were incubated during either 12h or 24h with growing concentrations of TVA (50 to 200 μM). Inhibitors of mitochondrial (etomoxir, 10 and 100 nM) and peroxisomal (thioridazin, 10 and 100 μM) β-oxydation were used. Sprague-Dawley pregnant rats (day 14) were fed during the last week of pregnancy plus two weeks of lactation, either with a TVA-diet or with the corresponding cis isomer (2% of total energy). TPA content was assessed in the main organs of dams and pups. Fatty acids (FAs) were analysed by GC-MS. Pure standards and 2-alkenyl-4,4-dimethyloxazoline derivatives (DMOX) were used for TPA identification. In hepatocytes, TPA grew along with TVA concentration in the medium, according to a 10% conversion-rate. This held for both total lipids and secreted triacylglycerols (TAG). TPA content significantly decreased only when blocking peroxisomal β-oxydation. TPA was specifically detected only in rats belonging to the TVA group. In the dams, TPA came from TVA’s retroconversion probably ensured by the liver. TPA was found in TAG of the mammary gland (0.07 ± 0.00 % of total FAs): therefore, pups also received TPA directly from their mothers’ milk, in agreement with TPA’s levels in gastric content (0.04 ± 0.00 % of total FAs). These results give evidence of a new metabolic pathway, and calls for deeper knowledge about TPA’s origin and impacts on health.
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https://hal.archives-ouvertes.fr/hal-02177692
Contributor : Etienne Guillocheau Connect in order to contact the contributor
Submitted on : Tuesday, July 9, 2019 - 11:51:56 AM
Last modification on : Wednesday, April 6, 2022 - 4:08:21 PM

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Étienne Guillocheau, Cyrielle Garcia, Léo Richard, Daniel D. Catheline, Philippe P. Legrand, et al.. Direct retroconversion of dietary trans-vaccenic acid to trans-palmitoleic acid: proof of concept and quantification in both cultured rat hepatocytes and pregnant rats. GERLI Meeting 2017, Oct 2017, Dijon, France. 2017, ⟨10.13140/RG.2.2.28471.21920⟩. ⟨hal-02177692⟩

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