Endothelial nitric oxide synthase (eNOS) knockout mice have defective mitochondrial beta-oxidation.
OBJECTIVE
Recent observations indicate that the delivery of nitric oxide by endothelial nitric oxide synthase (eNOS) is not only critical for metabolic homeostasis, but could also be important for mitochondrial biogenesis, a key organelle for free fatty acid (FFA) oxidation and energy production. Because mice deficient for the gene of eNOS (eNOS(-/-)) have increased triglycerides and FFA levels, in addition to hypertension and insulin resistance, we hypothesized that these knockout mice may have decreased energy expenditure and defective beta-oxidation.


METHODS
Several markers of mitochondrial activity were assessed in C57BL/6J wild-type or eNOS(-/-) mice including the energy expenditure and oxygen consumption by indirect calorimetry, in vitro beta-oxidation in isolated mitochondria from skeletal muscle, and expression of genes involved in fatty acid oxidation.


RESULTS
eNOS(-/-) mice had markedly lower energy expenditure (-10%, P < 0.05) and oxygen consumption (-15%, P < 0.05) than control mice. This was associated with a roughly 30% decrease of the mitochondria content (P < 0.05) and, most importantly, with mitochondrial dysfunction, as evidenced by a markedly lower beta-oxidation of subsarcolemmal mitochondria in skeletal muscle (-30%, P < 0.05). Finally, impaired mitochondrial beta-oxidation was associated with a significant increase of the intramyocellular lipid content (30%, P < 0.05) in gastrocnemius muscle.


CONCLUSIONS
These data indicate that elevated FFA and triglyceride in eNOS(-/-) mice result in defective mitochondrial beta-oxidation in muscle cells.
Department of Cellular Biology and Morphology, University of Lausanne, Lausanne, Switzerland.
Eric
E
Le Gouill
Maria
M
Jimenez
Christophe
C
Binnert
Pierre-Yves
PY
Jayet
Sebastien
S
Thalmann
Pascal
P
Nicod
Urs
U
Scherrer
Peter
P
Vollenweider
D000818:Animals; D049628:Body Size; D002153:Calorimetry, Indirect; D004272:DNA, Mitochondrial / Q000235:genetics; D004734:Energy Metabolism; D004822:Epididymis / Q000502:physiology; D005230:Fatty Acids, Nonesterified / Q000378:metabolism; D008066:Lipolysis; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D008928:Mitochondria / Q000378:metabolism*; D008931:Mitochondria, Muscle / Q000502:physiology; D018482:Muscle, Skeletal / Q000503:physiopathology; D019001:Nitric Oxide Synthase / Q000378:metabolism; D052248:Nitric Oxide Synthase Type I / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III / Q000172:deficiency*; D010084:Oxidation-Reduction; D010101:Oxygen Consumption; D016133:Polymerase Chain Reaction; D014280:Triglycerides / Q000378:metabolism
D004272:DNA, Mitochondrial; D005230:Fatty Acids, Nonesterified; D014280:Triglycerides; D019001:Nitric Oxide Synthase; D052248:Nitric Oxide Synthase Type I; D052250:Nitric Oxide Synthase Type III