PubMed Health⌕ Search

Biomedical subjects

Alan A Jackson

Publications and source records attributed to Alan A Jackson.

23 records · Page 2Linked to original sources
PubMed2002

Higher weight at birth is related to decreased maternal amino acid oxidation during pregnancy.

BACKGROUND: Small size at birth is associated with cardiovascular disease in adult life. Decreased fetal growth may result from a limitation in the nutrient supply to the fetus. Net tissue deposition in the mother and fetus increases the demand for nitrogen, but because maternal consumption of protein does not increase, there must be a change in the partitioning of amino acids, away from oxidation and toward deposition. OBJECTIVE: Our objective was to characterize amino acid oxidation in pregnancy and to investigate whether the relative partitioning of amino acids was related to fetal growth. DESIGN: We determined amino acid oxidation as urea production in 25 women during mid (17-19 wk) and late (26-29 wk) gestation. Urea production was measured from urinary [(15)N-(15)N]urea excretion over 48 h after a single oral dose of [(15)N-(15)N]urea. We measured the infant's size at birth. RESULTS: For the group as a whole, urea excretion decreased and amino acid oxidation remained similar between mid and late pregnancy, but there was wide variation between the women. Heavier infants were born to the mothers in whom amino acid oxidation decreased the most during pregnancy (slope of regression line: -80 g x g N(-1) x d(-1); 95% CI: -129, -31; P = 0.003). After adjustment for length of gestation and the infant's sex, the change in maternal amino acid oxidation explained 34% of the variation in birth weight. CONCLUSIONS: Amino acid oxidation varied widely between the women during pregnancy. Understanding the ability of a pregnant woman to adapt metabolically may have implications for establishing dietary recommendations in pregnancy.

Adult↗
PubMed2002

Protein, amino acid and nitrogen metabolism during pregnancy: how might the mother meet the needs of her fetus?

During pregnancy there is an increased demand for energy and protein to enable the fetus and placenta to grow. Current recommendations suggest an allowance for pregnancy of 6-10 g protein per day, however there is little consistent evidence that this is needed. Furthermore, there does not appear to be a simple relationship between the dietary protein intake of the mother and the size of the baby. If protein needs to be conserved, pregnant women must adapt metabolically. Methods for measuring protein metabolism have varied between studies. Some isotopic approaches are relatively invasive, but noninvasive methods are also available which can be used in larger numbers of women in free-living conditions. Taken together, isotopic studies during pregnancy indicate that there is a shift in the partitioning of amino acids towards net tissue deposition, reflected in an increased rate of protein synthesis, and away from oxidation, reflected in measures of urea synthesis. An understanding of the influences on fetal growth is needed to enable us to deal with the major problems in public health of our time. There is substantial evidence that impaired growth and development in utero is associated with a higher risk of cardiovascular and metabolic disease in adult life. In order to establish what dietary recommendations should be made, we need to explore further how women cope metabolically with the demands of pregnancy, particularly when faced with unusual demands over and above pregnancy, such as infection.

Adaptation, Physiological↗
PubMedDate not supplied

Docosahexaenoic acid is selectively enriched in plasma phospholipids during pregnancy in Trinidadian women--results of a pilot study.

The fetal demand for docosahexaenoic acid (DHA) has to be satisfied by the mother. We determined the fatty acids in maternal plasma non-esterified fatty acid (NEFA), triacylglycerol (TAG) and phosphatidylcholine (PC), in a cross-sectional study of non-pregnant (n = 10), pregnant (n = 19), and postpartum (n = 9) women. There were lipid class-dependent differences in plasma polyunsaturated fatty acid (PUFA) concentrations between groups. During pregnancy, DHA was most highly enriched in PC, about 230%, with more modest enrichment for linoleic acid (LA) and arachidonic acid (AA), and no enrichment of alpha-linolenic acid (alpha-LNA). There was relative enrichment of LA, AA and alpha-LNA in TAG, but not of DHA. There was no specific enrichment of any PUFA in the NEFA pool. These data accord with the suggestion that the enrichment of alpha-LNA in TAG and of DHA in phospholipids reflects hepatic regulation of n-3 PUFA metabolism which potentially enhances the delivery of DHA to the placenta.

Adult↗