Leucine kinetics and fuel utilization during a brief fast in human pregnancy

Scott Denne, Deepak Patel, Satish C. Kalhan

Research output: Contribution to journalArticle

24 Citations (Scopus)

Abstract

To examine proteolysis, protein and leucine oxidation, and fuel utilization during a brief fast (∼17 hours) in human pregnancy, we determined leucine kinetics, urea nitrogen excretion, and respiratory quotient (RQ) in 11 pregnant subjects during the second half of gestation, and in 11 normal nonpregnant controls. The total rate of appearance (Ra) of leucine was similar in the pregnant and control groups (pregnant 4.99 ± 0.60 v control 5.25 ± 1.60 mmol/h [mean ± SD]). However, leucine Ra per kilogram was significantly lower in pregnant subjects (pregnant 68 ± 7 v control 82 ± 13 μmol/kg/h, P <.01). In addition, urinary urea nitrogen excretion was also significantly less in pregnant subjects (pregnant 3.74 ± 1.09 v control 5.58 ± 1.6 mg/kg/h, P <.01). The RQ measured in the pregnant group was significantly higher than controls (0.82 ± 0.05 v 0.76 ± 0.04, P = .01), resulting in higher calculated carbohydrate oxidation rates during fasting in pregnancy. These data suggest that total rates of proteolysis (reflected by leucine flux) are similar in pregnant and nonpregnant subjects after an overnight fast. When normalized to body weight, proteolysis is lower in pregnant subjects. Urea excretion rates are also lower in pregnancy. These findings support the hypothesis that there is a pregnancy-induced adaptation to conserve maternal protein stores during a brief fast. The higher rate of carbohydrate oxidation during fasting in pregnancy may be a reflection of the fetal-placental unit's use of glucose as its predominant oxidative substrate.

Original languageEnglish (US)
Pages (from-to)1249-1256
Number of pages8
JournalMetabolism: Clinical and Experimental
Volume40
Issue number12
DOIs
StatePublished - 1991
Externally publishedYes

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Leucine
Pregnancy
Proteolysis
Urea
Fasting
Nitrogen
Carbohydrates
Proteins
Body Weight
Mothers
Glucose
Control Groups

ASJC Scopus subject areas

  • Endocrinology
  • Endocrinology, Diabetes and Metabolism

Cite this

Leucine kinetics and fuel utilization during a brief fast in human pregnancy. / Denne, Scott; Patel, Deepak; Kalhan, Satish C.

In: Metabolism: Clinical and Experimental, Vol. 40, No. 12, 1991, p. 1249-1256.

Research output: Contribution to journalArticle

Denne, Scott ; Patel, Deepak ; Kalhan, Satish C. / Leucine kinetics and fuel utilization during a brief fast in human pregnancy. In: Metabolism: Clinical and Experimental. 1991 ; Vol. 40, No. 12. pp. 1249-1256.
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