The Fraction of α-Linolenic Acid Present in the sn-2 Position of Structured Triacylglycerols Decreases in Lymph Chylomicrons and Plasma Triacylglycerols during the Course of Lipid Absorption in Rats3

Abstract

Little is known about the ability of α-linolenic acid (Ln) to remain in the sn-2 position of TG during the absorption process. The goal of this study was to determine the Ln distribution in the lymph (Study 1) and plasma (Study 2) TG of rats fed a single i.g. load of structured TG [300 mg/rat of either oleic acid (O)/Ln/O TG (OLnO) or Ln/O/O TG (LnOO), n = 7 rats]. In an early fraction (3-4 h) of lymph (OLnO group; 100% Ln in the sn-2 position), 46 ± 2% Ln was maintained in this position in lymph TG. There was even less (29 ± 6%) in the last fraction (7-24 h) (P < 0.05). Ln was also found (9 ± 3%) in the sn-2 position of lymph TG in the LnOO group. The Ln content in lymph phospholipids was twice as high in rats when they were fed LnOO (4.2 ± 0.1%) than OLnO (2.3 ± 0.2%) (P < 0.005). Six hours postprandially (Study 2), 21 ± 3% of the Ln incorporated into plasma TG was located in the sn-2 position in the OLnO group compared to 13 ± 2% in the LnOO group (P < 0.001). Overall, these results indicate that the amount of Ln that moved from the sn-2 position of structured TG to the sn-1(3) position of lymph TG increased during absorption. This may account for a substantial hydrolysis of the 2-monolinolenylglycerols in enterocytes, leading to the intramolecular redistribution of Ln in lymph TG and, consequently, in plasma TG.

Comparison of catabolic rates of 13C‐labeled palmitic acid bound to the alpha and beta positions of triacylglycerol using CO2 expired from mice

“…Theoretically, fatty acids bound to the b position of TAG are not hydrolyzed in this pathway. In reality, 60-72% of fatty acids bound to the b position of TAG are maintained in their original positions in the resynthesized TAG [24]. Dietary fatty acids are important energy sources for the body.…”

Matrice lipidique et biodisponibilité de l’acide alpha-linolénique

“…Toutefois, le maintien de la position de l'ALA sn2 est moindre avec l'huile de colza (75 %) qu'avec l'huile de soja (93 %). Même si la position interne était majoritairement conservée en ce qui concerne l'ALA, il est probable qu'une partie des 2-MG pourrait être hydrolysée par des hydrolases intestinales et conduire à une redistribution de l'ALA sur le squelette glycéridique des TG lymphatiques (Christensen et al, 1995 ;Couëdelo et al, 2012).…”

“…1). Deux mécanismes peuvent expliquer l'introduction de l'ALA en position externe des TG synthétisés par l'entérocyte, soit par une isomérisation dans la lumière intestinale, soit une partie de la sn2 monolinolénine absorbée par l'entérocyte a pu être hydrolysée par une lipase avant de servir d'amorce à la synthèse de nouveaux TG (Couëdelo et al, 2012). À l'inverse, lorsque l'ALA était exclusivement greffé en position externe du TG, moins de 10 % de l'ALA était retrouvé en position sn2 des TG lymphatiques.…”

Molecular and structural organization of lipids in foods: their fate during digestion and impact in nutrition

“…Nevertheless, MAG can be further hydrolyzed by enzymes having monoglyceride activity like CEL and PLRP2 (Armand, 2007;Bakala N'Goma et al, 2012). This could explain why part of the FAs at position sn-2 of TAG can be exchanged upon digestion, absorption and chylomicron (CM) synthesis (Couedelo et al, 2012). To be absorbed by the border brush membrane of the enterocytes, FFA and 2-MAG must be incorporated in nanoscale structures containing bile salts and called mixed micelles (8-20 nm) or into larger structures designed as vesicles (40-200 nm) containing phospholipids as well (Armand, 2013).…”