Effect of severe burn injury on substrate cycling by glucose and fatty acids

N Engl J Med. 1987 Aug 13;317(7):403-8. doi: 10.1056/NEJM198708133170702.

Abstract

Increases in metabolic rate and core temperature are common responses to severe injury. We have investigated the hypothesis that these responses are due to increases in substrate cycling. A substrate cycle exists when opposing, nonequilibrium reactions catalyzed by different enzymes are operating simultaneously. At least one of the reactions must involve the hydrolysis of ATP. Thus, a substrate cycle both liberates heat and increases energy expenditure, yet there is not net conversion of substrate to product. In studies in volunteers (n = 18) and in patients with severe burns who were in a hypermetabolic state (n = 18), we used stable-isotope tracers to quantify substrate cycling in the pathways of glycolysis and gluconeogenesis and a cycle involving the simultaneous breakdown and synthesis of stored triglyceride (triglyceride-fatty acid cycle). The total rates of triglyceride-fatty acid and glycolytic-gluconeogenic cycling were elevated in the patients by 450 and 250 percent, respectively (P less than 0.01). An infusion of propranolol in the patients greatly reduced triglyceride-fatty acid cycling but did not affect gluconeogenic-glycolytic cycling. We conclude that increased substrate cycling contributes to the increased thermogenesis and energy expenditure following severe burns and that the increased triglyceride-fatty acid cycling is due to beta-adrenergic stimulation.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adolescent
  • Adult
  • Body Temperature Regulation
  • Burns / metabolism*
  • Burns / physiopathology
  • Child
  • Child, Preschool
  • Energy Metabolism
  • Fatty Acids / metabolism*
  • Gluconeogenesis
  • Glucose / metabolism*
  • Glycolysis
  • Humans
  • Propranolol / pharmacology
  • Triglycerides / metabolism

Substances

  • Fatty Acids
  • Triglycerides
  • Propranolol
  • Glucose