Increased fetal glucose concentration decreases ovine fetal leucine oxidation independent of insulin

E. A. Liechty, D. W. Boyle, H. Moorehead, Y. M. Liu, S. C. Denne

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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 (R(a)) 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 μmol/min in the fed state during glucose infusion. Basal leucine oxidation was elevated during fasting (11 ± 1.5 μmol/min, P < 0.05) and declined to 8.0 ± 1.4 μmol/min during glucose infusion (P = 0.056). Leucine carbon R(a) was unchanged by fasting and by glucose infusion; leucine nitrogen R(a) 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.

Original languageEnglish (US)
Pages (from-to)E617-E623
JournalAmerican Journal of Physiology - Endocrinology and Metabolism
Volume265
Issue number4 28-4
StatePublished - Jan 1 1993

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Keywords

  • placenta
  • somatostatin
  • tracer methodology
  • α-ketoisocaproate

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Physiology
  • Physiology (medical)

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