Human milk in disease: Lipid Composition

Hamosh, Margit; Bitman, Joel

doi:10.1007/bf02535863

Cited by 25 publications

(12 citation statements)

References 68 publications

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“…Indeed, Hiltunen et al (1986) have demonstrated the retroconversion of 20:4n-6 to 14:2n-6 in rat liver peroxisomes. Likewise, 14:ln-9 must be derived from 18:ln-9 because the double bond in 14:l produced by de nouo synthesis is in the n-5 position [reviewed by Jensen et al (1990);Hamosh & Bitman, 1992;Kolezko & Springer, 19921. Since retroconversion is an active catabolic pathway in retina, it should be considered a potential source of these short-chain unsaturated fatty acids.…”

Section: Discussionmentioning

confidence: 99%

Synthesis of docosahexaenoic acid by retina and retinal pigment epithelium

Wang

Anderson

1993

Biochemistry

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Rod outer segments of vertebrate retinas are highly enriched in docosahexaenoic acid (22:n-3), a fatty acid that is essential for optimal retinal function. The high levels of retinal 22:6n-3 are maintained through conservation (recycling) within the eye and incorporation from the circulation. The liver is thought to be a major source of 22:6n-3 through synthesis from appropriate n-3 precursors and delivery to target tissues via plasma lipoproteins. The contribution of other tissues to the total body pool of 22:6n-3 is not known. We investigated the synthesis of 22:6n-3 from [1-14C]18:3n-3 or [3-14C]22:5n-3 in frog retina and retinal pigment epithelium (RPE). RPE cells rapidly converted each precursor to 22:6n-3, which contained about 23 and 35%, respectively, of the label after 8 h. Significant labeling of 24:6n-3 and 24:5n-3 occurred when [3-14C]22:5n-3 was the substrate. In contrast, the major end products of retinas incubated with [1-14C]18:3n-3 and [3-14C]22:5n-3 were 18:4n-3 and 20:5n-3, respectively, neither of which is found in retinal lipids. Less than 5% of the radioactivity from either precursor was in 22:6n-3 after an 8-h incubation. Our results demonstrate an active in vitro synthesis of 22:6n-3 in frog RPE, but not in the retina. The labeling of 24:5n-3 and 24:6n-3 is consistent with the proposal of Voss et al. [Voss, A., Reinhart, M., Sankarappa, S., & Sprecher, H. (1991) J. Biol. Chem. 266, 19995-20000] that they are intermediates in the conversion of 22:5n-3 to 22:6n-3. Since frog RPE contains measurable amounts of 18:3n-3, 20:5n-3, and 22:5n-3, which are readily converted to 22:6n-3 in these cells, we suggest that the RPE is a source of 22:6n-3 for the retina.

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Section: Discussionmentioning

confidence: 99%

Synthesis of docosahexaenoic acid by retina and retinal pigment epithelium

Wang

Anderson

1993

Biochemistry

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“…Contrariando a literatura [32][33][34] , neste trabalho foram obtidos maiores valores energéticos no colostro que no leite maduro (Tabela 2), embora os resultados possam ser considerados estatisticamente iguais em função do alto desvio padrão. Os lipídios são os componentes mais variáveis na composição do leite humano e sua quantidade pode variar em função do perío-do de lactação (colostro e maduro), do período da mamada (diurno ou noturno) e ao longo de cada mamada (leite do início e do fim) 5 .…”

Section: Composição Centesimalunclassified

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

Silva¹,

Escobedo²,

Gioielli³

et al. 2007

Quím. Nova

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Recebido em 29/5/06; aceito em 1/2/07; publicado na web em 30/7/07 CENTESIMAL COMPOSITION OF HUMAN MILK AND PHYSICO-CHEMICAL PROPERTIES OF ITS FAT. Human milk fat is essential for development of newborn infants. Many studies detail chemical characteristics of human milk fat; however there are no studies about its physical properties. The objective of this work was to analyze the centesimal composition of human milk and to compare the calculated energy value with the estimated energy by the creamatocrit method. Chemical composition and physical properties of human milk lipids and Betapol -a structured lipid -were also studied. The results showed that energy values of human milk estimated by creamatocrit and calculated by the centesimal composition didn't present significant correlation. Human milk lipids and Betapol presented distinct physico-chemical properties.Keywords: human milk; creamatocrit; Betapol. INTRODUÇÃOO leite humano é o único alimento energético, nutricional e imunológico consumido em quantidades suficientes pelos recém-nascidos 1,2 . O aleitamento materno fortalece a imunidade, mantém o crescimento e desenvolvimento normais, melhora o processo digestivo no sistema gastro-intestinal, favorece o vínculo mãe-filho e facilita o desenvolvimento emocional, cognitivo e do sistema nervoso [2][3][4] .O leite humano contém de 3 a 5% de lipídios, dentre os quais 98% são de triacilgliceróis, 1% de fosfolipídios e 0,5% de esteróis 5 . Os lipídios apresentam-se na forma de glóbulos de cerca de 4 μm de diâmetro em emulsão do tipo óleo em água, que é estabilizada por uma membrana contendo fosfolipídios e proteínas 6 . Cerca de 50% do valor calórico total do leite humano é proveniente da gordura, que é fonte de colesterol, ácidos graxos essenciais e vitaminas lipossolúveis 7 . O conteúdo de ácidos graxos insaturados no leite humano é maior que no de leite de vaca 8 .As proteínas do leite humano são qualitativamente diferentes das do leite de vaca. Do conteúdo protéico no leite humano, 80% é lactoalbumina, enquanto que no leite de vaca essa proporção é de caseína. A relação proteínas do soro/caseína no leite humano é aproximadamente 80/20, enquanto a no leite bovino é 20/80. A baixa concentração de caseína no leite humano resulta na formação de coalho gástrico mais leve, com flóculos de mais fácil digestão e com reduzido tempo de esvaziamento gástrico. O leite humano contém também, diferentemente do leite de vaca, maiores concentrações de aminoácidos essenciais de alto valor biológico (cistina e taurina) que são fundamentais ao desenvolvimento do sistema nervoso central. Isso é particularmente importante para o prematuro, que não consegue sintetizá-los a partir de outros aminoácidos por deficiência enzimática 9 .A partir da década de 70, com o incentivo ao aleitamento materno, houve crescimento na pesquisa sobre o leite humano 10 . Assim, as nutrizes foram incentivadas a ordenhar e doar o excesso de leite produzido, ficando os bancos de leite humano responsáveis pela atividade de coleta, processamento e controle de...

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“…We first tested whether 14:1n-9 and 14:2n-6 might be generated by de novo synthesis, because the 14:1n-5 isomer can be synthesized via a ⌬ 9 -desaturase (Hamosh and Bitman, 1992;Koletzko et al, 1992), but we found that 14:0 does not serve as a desaturase substrate in the retina and only 16:0 and 18:0 are produced. We next considered that 14:1n-9 and 14:2n-6 might be produced during the ␤-oxidation (retroconversion) of long chain unsaturated fatty acids.…”

Section: Distribution Of Desaturation Elongation or Retroconversionmentioning

confidence: 99%

Biosynthesis of the Unsaturated 14-Carbon Fatty Acids Found on the N Termini of Photoreceptor-specific Proteins

DeMar

Wensel

Anderson

1996

Journal of Biological Chemistry

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In the vertebrate retina, a number of proteins involved in signal transduction are known to be N-terminal acylated with the unusual 14 carbon fatty acids 14:1n-9 and 14:2n-6. We have explored possible pathways for producing these fatty acids in the frog retina by incubation in vitro with candidate precursor fatty acids bearing radiolabels, including [3H]14:0, [3H]18:1n-9, [3H]18:2n-6, and [3H]18:3n-3. Rod outer segments were prepared from the radiolabeled retinas for analysis of protein-linked fatty acids, and total lipids were extracted from the remaining retinal pellet. Following saponification of extracted lipids, fatty acid phenacyl esters were prepared and analyzed by high pressure liquid chromatography (HPLC) with detection by continuous scintillation counting. Transducin, whose alpha-subunit (Gt alpha) is known to bear N-terminal acyl chains, was extracted from the rod outer segments and subjected to SDS-polyacrylamide gel electrophoresis and fluorography to detect radiolabeled proteins. Gt alpha was also subjected to methanolysis, and the resulting fatty acyl methyl esters were analyzed by HPLC. The identities of HPLC peaks coinciding with unsaturated species of both phenacyl esters and methyl esters were confirmed by reanalyzing them after catalytic hydrogenation. The results showed that 14:1n-9 can be derived in the retina from 18:1n-9 and 14:2n-6 from 18:2n-6, most likely by two rounds of beta-oxidation, but that neither is produced in detectable amounts from 14:0. Retroconversion of unsaturated 18 carbon fatty acids to the corresponding 14 carbon species showed specificity, in that 18:3n-3 was not converted to 14 carbon fatty acids in detectable amounts. Myristic acid (14:0), 14:1n-9, and 14:2n-6 were all incorporated into Gt alpha. A much less efficient incorporation of 18:1n-9 into Gt alpha was also observed, but no radiolabeling of Gt alpha was observed in retinas incubated with 18:3n-3. Thus, retroconversion by limited beta-oxidation of longer chain unsaturated fatty acids appears to be the most likely metabolic source of the unusual fatty acids found on the N termini of signal transducing proteins in the retina.

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Human milk in disease: Lipid Composition

Cited by 25 publications

References 68 publications

Synthesis of docosahexaenoic acid by retina and retinal pigment epithelium

Synthesis of docosahexaenoic acid by retina and retinal pigment epithelium

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

Biosynthesis of the Unsaturated 14-Carbon Fatty Acids Found on the N Termini of Photoreceptor-specific Proteins

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