In the human intestine, lipids are adsorbed as Sn-2 monoglyc- erides (Sn-2), as effect of the pancreatic lipase action, which hydrolyzes the triglyceride on alpha-position (Sn1-3). Hence, the fatty acids esterified in Sn-2 are preferentially adsorbed. In a pre- vious research we obtained a significant enrichment in Conjugated Linoleic Acid (CLA) and alpha-linolenic acid (ALA) of milk and cheese from sheep fed a diet supplemented with lin- seed. The aim of the present work was to study the triglyceride (TG) composition of the milk of the mentioned study, in order to evaluate the selectivity of CLA and ALA for the Sn-2 position on TG. Sn-2 monoglycerides were obtained by reacting the milk total lipids (TL) from 24 sheep fed with control diet (C) and 24 sheep fed with a diet containing 200 g/die of extruded linseed (L) with swine pancreatic lipase, separated by thin layer chromatography (TLC). The selectivity of individual fatty acids for the Sn-2 posi- tion was evaluated by means of a selectivity index (SI) calculated as FA(Sn-2)/FA(TG); where SI<1 indicated a preferential esteri- fication in alpha-position and SI>1 in Sn-2. As regard the fatty acid composition of triglycerides, L compared to C, showed a sig- nificant higher content of both ALA and CLA: +45% and +75% respectively (P<0.001). Regarding to the beta-position of TG, ALA was 1.1 g/100g of TL in C and 2.2 g/100 of TL in L (P<0.001), andCLAwas1.2g/100gofTLinCand3.5g/100gofTLinL (P<0.001). As a consequence, in the milk from L group, the con- tent of ALA and CLA increased by 100% and 191%, respectively, than in the milk from C group. These results seemed to indicate a preferential esterification of ALA and CLA in the beta-position of milk triglycerides, probably as a consequence of changes in selectivity of acyl-transferase enzyme (LPAAT). In particular, as regard CLA content, the affinity of LPAAT was inverted: in fact, in C milk, CLA was preferentially esterified in the alpha-position (SI=0.56), while in L milk the SI was higher than 2, suggesting a preferential esterification in the beta position.
The content of cla and alpha-linolenic acid in sn-2 of ovine milk triglycerides as affected by dietary lipid supplementation
SERRA, ANDREA;CONTE, GIUSEPPE;CAPPUCCI, ALICE;CASAROSA, LAURA;MELE, MARCELLO
2013-01-01
Abstract
In the human intestine, lipids are adsorbed as Sn-2 monoglyc- erides (Sn-2), as effect of the pancreatic lipase action, which hydrolyzes the triglyceride on alpha-position (Sn1-3). Hence, the fatty acids esterified in Sn-2 are preferentially adsorbed. In a pre- vious research we obtained a significant enrichment in Conjugated Linoleic Acid (CLA) and alpha-linolenic acid (ALA) of milk and cheese from sheep fed a diet supplemented with lin- seed. The aim of the present work was to study the triglyceride (TG) composition of the milk of the mentioned study, in order to evaluate the selectivity of CLA and ALA for the Sn-2 position on TG. Sn-2 monoglycerides were obtained by reacting the milk total lipids (TL) from 24 sheep fed with control diet (C) and 24 sheep fed with a diet containing 200 g/die of extruded linseed (L) with swine pancreatic lipase, separated by thin layer chromatography (TLC). The selectivity of individual fatty acids for the Sn-2 posi- tion was evaluated by means of a selectivity index (SI) calculated as FA(Sn-2)/FA(TG); where SI<1 indicated a preferential esteri- fication in alpha-position and SI>1 in Sn-2. As regard the fatty acid composition of triglycerides, L compared to C, showed a sig- nificant higher content of both ALA and CLA: +45% and +75% respectively (P<0.001). Regarding to the beta-position of TG, ALA was 1.1 g/100g of TL in C and 2.2 g/100 of TL in L (P<0.001), andCLAwas1.2g/100gofTLinCand3.5g/100gofTLinL (P<0.001). As a consequence, in the milk from L group, the con- tent of ALA and CLA increased by 100% and 191%, respectively, than in the milk from C group. These results seemed to indicate a preferential esterification of ALA and CLA in the beta-position of milk triglycerides, probably as a consequence of changes in selectivity of acyl-transferase enzyme (LPAAT). In particular, as regard CLA content, the affinity of LPAAT was inverted: in fact, in C milk, CLA was preferentially esterified in the alpha-position (SI=0.56), while in L milk the SI was higher than 2, suggesting a preferential esterification in the beta position.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
