Increased myocardial lactate oxidation in lambs with aortopulmonary shunts at rest and during exercise

GCM Beaufort-Krol*, J Takens, MC Molenkamp, GB Smid, KJ Meuzelaar, WG Zijlstra, JRG Kuipers

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

7 Citations (Scopus)

Abstract

Free fatty acids are the major fuels for the myocardium, but during a higher load carbohydrates are preferred. Previously, we demonstrated that myocardial net lactate uptake was higher in lambs with aortopulmonary shunts than in control lambs. To determine whether this was caused by an increased lactate uptake and oxidation or by a decreased lactate release, we studied myocardial lactate and glucose metabolism with C-13-labeled substrates in 36 lambs in a fasting, conscious state. The lambs were assigned to two groups: a resting group consisting of 8 shunt and 9 control lambs, and an exercise group (50% of peak O-2 consumption) consisting of 9 shunt and 10 control lambs. Myocardial lactate oxidation was higher in shunt than in control lambs (mean +/- SE, rest: 10.33 +/- 2.61 vs. 0.17 +/- 0.82, exercise: 38.05 +/- 8.87 vs. 16.89 +/- 4.78 mu mol.min(-1).100 g(-1); P <0.05). There was no difference in myocardial lactate release between shunt and control lambs. Oxidation of exogenous glucose, which was approximately zero at rest, increased during exercise in shunt and control lambs. The contribution of glucose and lactate to myocardial oxidative metabolism increased during exercise compared with at rest in both shunt and control lambs. We conclude that myocardial lactate oxidation is higher in shunt than in control lambs, both at rest and during exercise, and that the contribution of carbohydrates in myocardial oxidative metabolism in shunt lambs is higher than in control lambs. Thus it appears that this higher contribution of carbohydrates occurs not only in the case of pressure-overloaded hearts but also in myocardial hypertrophy due to volume overloading.

Original languageEnglish
Pages (from-to)H1503-H1512
Number of pages10
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume275
Issue number5
Publication statusPublished - Nov-1998

Keywords

  • carbon-13-labeled substrates
  • congenital heart disease
  • left-to-right shunt
  • glucose
  • metabolism
  • FATTY-ACID UPTAKE
  • BLOOD-FLOW
  • HYPERTROPHIED HEARTS
  • CHEMICAL-EXTRACTION
  • PRESSURE-OVERLOAD
  • CONSCIOUS LAMBS
  • RAT HEARTS
  • METABOLISM
  • GLUCOSE
  • OXYGEN

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