title: Increased fetal glucose concentration decreases ovine fetal leucine oxidation independent of insulin.
abstract: Fetal leucine oxidation rate is elevated during fasting of the ewe. Euglycemic hyperinsulinemia causes the leucine oxidation rate to decline. However, it is unclear whether this is a direct effect of insulin or is secondary to increased insulin-mediated glucose utilization. To better delineate the mechanism of decreased oxidation, we suppressed fetal insulin secretion by somatostatin infusion. Glucose was infused at a variable rate to achieve glucose concentrations 125 and 150% of basal. Leucine rate of appearance (Ra) was determined by infusion of [15N, 1-13C]leucine. Fraction of leucine appearance oxidized was determined by [1-14C]leucine infusion and determination of fetal 14CO2 excretion. Each fetus was studied during ad libitum maternal feeding and after a 5-day complete maternal fast. Changes were noted in fetal leucine oxidation, which declined from 8.4 +/- 1.2 to 5.0 +/- 0.8 mumol/min in the fed state during glucose infusion. Basal leucine oxidation was elevated during fasting (11 +/- 1.5 mumol/min, P < 0.05) and declined to 8.0 +/- 1.4 mumol/min during glucose infusion (P = 0.056). Leucine carbon Ra was unchanged by fasting and by glucose infusion; leucine nitrogen Ra declined in the fed state only. Leucine oxidation was inversely correlated with glucose concentration (oxidation = 12-0.26 x glucose concentration, r = 0.42, P = 0.004). Leucine oxidation was not correlated with insulin concentration (r = 0.2). Changes in fetal glucose concentration may alter the pattern of utilization of essential amino acids, independent of changes in insulin and insulin-mediated glucose utilization rate.
authors.affiliation: Department of Pediatrics, Indiana University School of Medicine, Indianapolis 46202-5210.
authors.forename: E A
authors.initials: EA
authors.lastname: Liechty
authors.forename: D W
authors.initials: DW
authors.lastname: Boyle
authors.forename: H
authors.initials: H
authors.lastname: Moorehead
authors.forename: Y M
authors.initials: YM
authors.lastname: Liu
authors.forename: S C
authors.initials: SC
authors.lastname: Denne
mesh_terms: D000597:Amino Acids, Branched-Chain / Q000097:blood; D000818:Animals; D001786:Blood Glucose / Q000378:metabolism*; D002245:Carbon Dioxide / Q000097:blood; D004435:Eating; D005215:Fasting; D005312:Fetal Blood; D007328:Insulin / Q000494:pharmacology*; D007651:Keto Acids / Q000097:blood; D007930:Leucine / Q000097:blood*; D009994:Osmolar Concentration; D010084:Oxidation-Reduction; D012756:Sheep; D013004:Somatostatin / Q000494:pharmacology
chemical_list: D000597:Amino Acids, Branched-Chain; D001786:Blood Glucose; D007328:Insulin; D007651:Keto Acids; D002245:Carbon Dioxide; D013004:Somatostatin; C013082:alpha-ketoisocaproic acid; D007930:Leucine