In vitro and in vivo evidence of dietary trans-vaccenic acid retroconversion to trans-palmitoleic acid
Résumé
High levels of circulating trans-palmitoleic acid (TPA, C16:1 n-7 trans) are associated with a lower risk of metabolic syndrome. It was actually assumed that TPA arises from dietary transvaccenic acid (TVA, C18:1 n-7 trans) through the β-oxydation pathway. This study aimed at providing evidence of such retroconversion. Fresh rat hepatocytes were incubated with growing amounts of TVA to assess the conversion rate. Inhibitors of mitochondrial and peroxisomal β-oxydation were also used. Sprague-Dawley pregnant rats 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). Pups were exclusively fed with maternal milk for two weeks. TPA content was assessed in the main organs of both dams and pups. TPA was properly identified in hepatocytes. The conversion rate was estimated at 10%. Triacylglycerols secreted by hepatocytes did contain TPA. Blocking peroxisomal β-oxydation significantly decreased the conversion rate. TPA was quantified in the dams fed the TVA-supplemented diet and their pups, excepted in the brain. Importantly, TPA was found in the maternal milk. Liver ensures the retroconversion of dietary TVA to TPA, which can be exported to other tissues. Circulating levels of TPA are explained by dietary intakes of TVA. Given epidemiological data about TPA, future research is needed to assess dietary intakes of TVA.