2 research outputs found
Synthesis of the suspected trans-11,cis-13 conjugated linoleic acid isomer in ruminant mammary tissue by FADS3-catalyzed Δ13-desaturation of vaccenic acid
14 páginas, 7 figuras, 1 tabla.The octadecadienoic conjugated linoleic acid (CLA)
isomer with trans-11 and cis-13 double bonds (trans11,cis-13
CLA) has been described in ruminant milk.
For now, this specific CLA is suspected to derive exclusively
from ruminal biohydrogenation of dietary
α-linolenic acid. However, in rodents, the fatty acid
desaturase 3 (FADS3) gene was recently shown to code
for an enzyme able to catalyze the unexpected Δ13-
desaturation of vaccenic acid, producing a Δ11,13-CLA
with all the structural characteristics of the trans11,cis-13
isomer, although no commercial standard
exists for complete conclusive identification. Because
the FADS3 gene has already been reported in bovine
animals, we hypothesized in the present study that an
alternative direct FADS3-catalyzed Δ13-desaturation
of vaccenic acid in mammary tissue may therefore coexist
with α-linolenic acid biohydrogenation to explain
the final ruminant milk trans-11,cis-13 CLA presence.
Here, we first confirm that the FADS3 gene is present
in ruminant mammal genomic sequence databases.
Second, we demonstrate that the Δ11,13-CLA found in
milk fat and the highly probable trans-11,cis-13 CLA
isomer produced by rodent FADS3 possess exactly the
same structural characteristics. Then, we show that
bovine mammary MAC-T and BME-UV epithelial cells
express both FADS3 and stearoyl-CoA desaturase 1
(SCD1) mRNA and are able to synthesize both the
suspected trans-11,cis-13 CLA and cis-9,trans-11CLA
(rumenic acid) isomers when incubated with vaccenic
acid. Finally, the concomitant presence of the suspected
trans-11,cis-13 CLA isomer with FADS3 mRNA was
shown in goat mammary tissue, whereas both were conversely
very low or even absent in goat liver. Therefore,
this study provides several lines of evidence that, by
analogy with rumenic acid, trans-11,cis-13 CLA may
originate both from ruminal biohydrogenation and
from direct FADS3-catalyzed Δ13-desaturation of vaccenic
acid in mammary tissue.The authors thank Frédéric Dessauge (UMR Pegase,
INRA Saint-Gilles, France) for the MAC-T and BMEUV
cell lines. The authors also gratefully acknowledge
O. Loreau (CEA, Saclay and Cadarache, France) for
the supply of [1-13C]-vaccenic acid and the Transqual
project (Clermont-Ferrand, France; ANR-05-PNRANo.5.E.24).
This work was supported by the Groupe
Lipides et Nutrition (GLN, Paris, France).Peer Reviewe
Synthesis of the suspected trans-11,cis-13 conjugated linoleic acid isomer in ruminant mammary tissue by FADS3-catalyzed Δ13-desaturation of vaccenic acid
The octadecadienoic conjugated linoleic acid (CLA) isomer with trans-11 and cis-13 double bonds (trans11,cis-13 CLA) has been described in ruminant milk. For now, this specific CLA is suspected to derive exclusively from ruminal biohydrogenation of dietary alpha-linolenic acid. However, in rodents, the fatty acid desaturase 3 (FADS3) gene was recently shown to code for an enzyme able to catalyze the unexpected Delta 13-desaturation of vaccenic acid, producing a Delta 11,13-CLA with all the structural characteristics of the trans 11, cis-13 isomer, although no commercial standard exists for complete conclusive identification. Because the FADS3 gene has already been reported in bovine animals, we hypothesized in the present study that an alternative direct FADS3-catalyzed Delta 13-desaturation of vaccenic acid in mammary tissue may therefore coexist with alpha-linolenic acid biohydrogenation to explain the final ruminant milk trans-11,cis-13 CLA presence. Here, we first confirm that the FADS3 gene is present in ruminant mammal genomic sequence databases. Second, we demonstrate that the 011,13-CLA found in milk fat and the highly probable trans-11,cis-13 CLA isomer produced by rodent FADS3 possess exactly the same structural characteristics. Then, we show that bovine mammary MAC-T and BME-UV epithelial cells express both FADS3 and stearoyl-CoA desaturase 1 (SCD1) mRNA and are able to synthesize both the suspected trans-11,cis-13 CLA and cis-9,trans-11CLA (rumenic acid) isomers when incubated with vaccenic acid. Finally, the concomitant presence of the suspected trans-11,cis-13 CLA isomer with FADS3 mRNA was shown in goat mammary tissue, whereas both were conversely very low or even absent in goat liver. Therefore, this study provides several lines of evidence that, by analogy with rumenic acid, trans-11, cis-13 CLA may originate both from ruminal biohydrogenation and from direct FADS3-catalyzed Delta 13-desaturation of vaccenic acid in mammary tissue