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PubMed1993

Development of primary culture of ovine fetal hepatocytes for studies of amino acid metabolism and insulinlike growth factors.

We report the development and characterization of a system of primary culture of ovine fetal hepatocytes to aid in the understanding of the cellular regulation of fetal growth and metabolism with emphasis on amino acid metabolism and insulinlike growth factor gene expression and to allow comparison to in vivo studies. Hepatocytes were isolated from late gestation fetal lambs by in situ perfusion and collagenase digestion utilizing occlusion of the ductus venosus to limit intrahepatic shunting. Hepatocytes were cultured in media modified to mimic fetal concentrations of glucose, lactate, and amino acids. Ovine fetal hepatocytes in primary culture maintain the pattern of fetal amino acid production and utilization seen across the fetal liver in vivo. Specifically, there is a net production of serine and a net utilization of glycine. Cultured ovine fetal hepatocytes specifically increase tritiated thymidine incorporation in response to insulin and insulinlike growth factor II (IGF-II). IGF-II mRNA abundance is high and IGF-I mRNA is low in cultured ovine fetal hepatocytes as in the fetal sheep liver in vivo. These data demonstrate the successful isolation of ovine fetal hepatocytes that retain some of the characteristics of the ovine fetal liver while maintained in short-term culture.

Amino Acids↗
PubMed2006

Essential polyunsaturated fatty acids in plasma and erythrocytes of children with inborn errors of amino acid metabolism.

Essential fatty acids (EFAs), and their longer-chain more-unsaturated derivatives (LCPUFAs) in particular, are essential for normal growth and cognitive development during childhood. Children with inborn errors of amino acid metabolism represent a risk population for a reduced LCPUFA status because their diet is low in EFAs and LCPUFAs. We have investigated the EFA and LCPUFA status of children with various amino acid metabolism disorders (not PKU) under treatment. Fatty acid profiles of plasma and erythrocyte phospholipids of 33 patients (aged 0-18 years) and 38 matched controls were determined by gas-liquid chromatography. Food-frequency questionnaires were used to assess the mean fatty acid intake. The dietary intake of the EFAs linoleic acid (LA) and alpha-linolenic acid (ALA) was comparable in both groups, while the LCPUFA intake was much lower in patients. This was associated with lower relative concentrations (% of total fatty acids) of n-3 docosahexaenoic acid (DHA) in plasma and erythrocyte phospholipids. Concentrations of arachidonic acid (AA) did not differ. The same was observed for the two EFAs LA and ALA. Thus, as compared to healthy controls, children with amino acid metabolism disorders have a lower intake of LCPUFAs and have lower concentrations of DHA but not of AA in plasma and erythrocyte phospholipids. This suggests that endogenous AA synthesis might guarantee an adequate AA status. The lower DHA status, however, warrants further investigations regarding the impact of DHA supplementation on growth and development of these children.

Adolescent↗
PubMed2001

Regulation of skeletal muscle amino acid metabolism during exercise.

The contribution of amino acid oxidation to total energy expenditure is negligible during short-term intense exercise and accounts for 3-6% of the total adenosine triphosphate supplied during prolonged exercise in humans. While not quantitatively important in terms of energy supply, the intermediary metabolism of several amino acids-notably glutamate, alanine, and the branched-chain amino acids-affects other metabolites, including the intermediates within the tricarboxylic acid (TCA) cycle. Glutamate appears to be a key substrate for the rapid increase in muscle TCA cycle intermediates (TCAI) that occurs at the onset of moderate to intense exercise, due to a rightward shift of the reaction catalyzed by alanine aminotransferase (glutamate + pyruvate <==> alanine + 2-oxoglutarate). The pool of muscle TCAI declines during prolonged exercise, and this has been attributed to an increase in leucine oxidation that relies on one of the TCAI. However, this mechanism does not appear to be quantitatively important due of the relatively low maximal activity of branched-chain oxoacid dehydrogenase, the key enzyme involved. It has been suggested that an increase in TCAI is necessary to attain high rates of aerobic energy production and that a decline in TCAI may be a causative factor in local muscle fatigue. These topics remain controversial, but recent evidence suggests that changes in TCAI during exercise are unrelated to oxidative energy provision in skeletal muscle.

Amino Acids↗