30 research outputs found
Particularité du passage de l'acide α-linolénique à travers la membrane mitochondriale externe : comparaison avec les acides palmitique et oléique
International audienc
Les CLA, ânouveaux nutriments fonctionnelsâ ?
Les diĂšnes conjuguĂ©s de lâacide linolĂ©ique (CLA) constituent un groupe dâacides
gras atypiques produits au cours de lâhydrogĂ©nation progressive de lâacide
linoléique. Dans différentes espÚces de mammifÚre, les mélanges isomériques
commerciaux vendus comme complĂ©ments alimentaires provoquent dâune chute plus ou
moins marquée de la masse grasse. Cet effet anti-obésité est strictement
dĂ©pendant de lâisomĂšre t10,c12-CLA trouvĂ© normalement Ă lâĂ©tat de trace dans
lâalimentation. Chez la souris, la consommation chronique de cet isomĂšre
entraĂźne lâapparition dâun syndrome complexe caractĂ©risĂ© par une lipoatrophie,
une hyperinsulinémie, une insulinorésistance et une stéatose hépatique dont
lâorigine et la chronologie sont prĂ©sentĂ©es et commentĂ©es dans cette synthĂšse.
Chez lâHomme, lâimpact des CLA sur la masse grasse est anecdotique. Cependant,
des essais cliniques indiquent que la consommation de t10,c12-CLA peut
sâaccompagner dâeffets secondaires indĂ©sirables. Lâintroduction de mĂ©langes de
CLA riches en t10,c12-CLA dans lâalimentation humaine ne semble donc pas
justiïŹĂ©e, que ce soit sous forme de complĂ©ments ou sous forme dâingrĂ©dients
alimentaires
Enzymatic properties and cholesterol content of mitochondrial outer membranes in liver of obese and lean Zucker rats
International audienc
Differential involvement of peroxisome-proliferator-activated receptors alpha and delta in fibrate and fatty-acid-mediated inductions of the gene encoding liver fatty-acid-binding protein in the liver and the small intestine.
Liver fatty-acid-binding protein (L-FABP) is a cytoplasmic polypeptide that binds with strong affinity especially to long-chain fatty acids (LCFAs). It is highly expressed in both the liver and small intestine, where it is thought to have an essential role in the control of the cellular fatty acid (FA) flux. Because expression of the gene encoding L-FABP is increased by both fibrate hypolipidaemic drugs and LCFAs, it seems to be under the control of transcription factors, termed peroxisome-proliferator-activated receptors (PPARs), activated by fibrate or FAs. However, the precise molecular mechanism by which these regulations take place remain to be fully substantiated. Using transfection assays, we found that the different PPAR subtypes (alpha, gamma and delta) are able to mediate the up-regulation by FAs of the gene encoding L-FABP in vitro. Through analysis of LCFA- and fibrate-mediated effects on L-FABP mRNA levels in wild-type and PPARalpha-null mice, we have found that PPARalpha in the intestine does not constitute a dominant regulator of L-FABP gene expression, in contrast with what is known in the liver. Only the PPARdelta/alpha agonist GW2433 is able to up-regulate the gene encoding L-FABP in the intestine of PPARalpha-null mice. These findings demonstrate that PPARdelta can act as a fibrate/FA-activated receptor in tissues in which it is highly expressed and that L-FABP is a PPARdelta target gene in the small intestine. We propose that PPARdelta contributes to metabolic adaptation of the small intestine to changes in the lipid content of the diet