Triacylglycerol structure of human colostrum and mature milk

Abstract

Because triacylglycerol (TAG) structure influences the metabolic fate of its component fatty acids, we have examined human colostrum and mature milk TAG with particular attention to the location of the very long chain polyunsaturated fatty acid on the glycerol backbone. The analysis was based on the formation of various diacylglycerol species from human milk TAG upon chemical (Grignard degradation) or enzymatic degradation. The structure of the TAG was subsequently deduced from data obtained by gas chromatographic analysis of the fatty acid methyl esters in the diacylglycerol subfractions. The highly specific TAG structure observed was identical in mature milk and colostrum. The three major fatty acids (oleic, palmitic and linoleic acids) each showed a specific preference for a particular position within milk TAG: oleic acid for the sn-1 position, palmitic acid for the sn-2 position and linoleic acid for the sn-3 position. Linoleic and alpha-linolenic acids exhibited the same pattern of distribution and they were both found primarily in the sn-3 (50%) and sn-1 (30%) positions. Their longer chain analogs, arachidonic and docosahexaenoic acids, were located in the sn-2 and sn-3 positions. These results show that polyunsaturated fatty acids are distributed within the TAG molecule of human milk in a highly specific fashion, and that in the first month of lactation the maturation of the mammary gland does not affect the milk TAG structure.

Fatty acid and sn-2 fatty acid composition in human milk from Granada (Spain) and in infant formulas

“…Therefore, the carbon chain length (between 10 and 16 carbons) seems to be a discriminating factor in the distribution of these saturated fatty acids in the sn-2 position of the triacylglycerides. Similar results were found by Martin et al, (1993). Moreover, this increase was observed in C 18 fatty acids, in which we found that relative percentages of these fatty acids in the sn-2 position increased from C18:0 to C18:3 n-3.…”

“…The reason for this can be explained easily through an example. If we compared our result of sn-2 palmitic acid in mature milk (52.30%) with other studies (Martin et al, 1993;Nelson & Innis, 1999), our result was consistent with that of Martin et al, (51.22%), but was different from the result of Nelson and Innis (56.4%). The error is that we were comparing percentages of sn-2 palmitic acid, but without taking into account the total percentage of palmitic acid in human milk, which varies in Fatty acids and sn-2 fatty acids in human milk A López-López et al the studies.…”

“…Moreover, this increase was observed in C 18 fatty acids, in which we found that relative percentages of these fatty acids in the sn-2 position increased from C18:0 to C18:3 n-3. Martin et al, (1993) did not find this because they did not work with relative fatty acid in the sn-2 position percentages.…”

Composição centesimal do leite humano e caracterização das propriedades físico-químicas de sua gordura

“…40 . Para a gordura do leite humano, os esferulitos podem corresponder à forma polimórfica β, pois o alto nível de ácido palmítico na posição sn-2 da gordura do leite 35,39,42 torna os triacilgliceróis com estrutura molecular homogênena. Por outro lado, os esferulitos do Betapol mostraram-se opticamente ativos ("axial crosses"), que possivelmente representam cristalização na forma polimórfica β-prima, pois o produto Betapol apresenta alto teor de ácido láurico, o que torna os triacilgliceróis com estrutura molecular mais heterogênea.…”

Lipídios estruturados: alternativa para a produção de sucedâneos da gordura do leite humano

“…110,111 Cerca de 87% do DHA encontrado no leite humano está na forma de triacilgliceróis, sendo principalmente esterificado nas posições sn-2 (∼50%) e sn-3 (∼42%) dos triacilgliceróis. 112 Quando lactentes recebem dietas contendo altos teores de DHA, esse ácido graxo tem seu aumento refletido no leite humano, [113][114][115] e proporciona melhor desenvolvimento do sistema nervoso do recém-nascido.…”