Increased entropy production in diaphragm muscle of PPAR alpha knockout mice

J Theor Biol. 2008 Jan 7;250(1):92-102. doi: 10.1016/j.jtbi.2007.09.022. Epub 2007 Sep 21.

Abstract

Peroxisome proliferator activated receptor alpha (PPAR alpha) regulates fatty acid beta-oxidation (FAO) and plays a central role in the metabolic and energetic homeostasis of striated muscles. The thermodynamic consequences of the absence of PPAR alpha were investigated in diaphragm muscle of PPAR alpha knockout mice (KO). Statistical mechanics provides a powerful tool for determining entropy production, which quantifies irreversible chemical processes generated by myosin molecular motors and which is the product of thermodynamic force A/T (chemical affinity A and temperature T) and thermodynamic flow (myosin crossbridge (CB) cycle velocity upsilon). The behavior of both wild type (WT) and KO diaphragm was shown to be near-equilibrium and in a stationary state, but KO was farther from equilibrium than WT. In KO diaphragm, a substantial decrease in contractile function was associated with an increase in both A/T and upsilon and with profound histological injuries such as contraction band necrosis. There were no changes in PPAR delta and gamma expression levels or myosin heavy chain (MHC) patterns. In KO diaphragm, a marked increase in entropy production (A/T x upsilon) accounted for major thermodynamic dysfunction and a dramatic increase in irreversible chemical processes during the myosin CB cycle.

MeSH terms

  • Animals
  • Body Weight
  • Diaphragm / metabolism
  • Diaphragm / pathology
  • Diaphragm / physiopathology*
  • Entropy
  • Gene Expression Regulation
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Myosin Heavy Chains / analysis
  • Myosins / metabolism
  • PPAR alpha / biosynthesis
  • PPAR alpha / deficiency*
  • PPAR alpha / genetics
  • PPAR delta / biosynthesis
  • PPAR delta / genetics
  • PPAR gamma / biosynthesis
  • PPAR gamma / genetics
  • Protein Isoforms / analysis
  • RNA, Messenger / genetics
  • Reverse Transcriptase Polymerase Chain Reaction / methods
  • Thermodynamics

Substances

  • PPAR alpha
  • PPAR delta
  • PPAR gamma
  • Protein Isoforms
  • RNA, Messenger
  • Myosin Heavy Chains
  • Myosins