PGC-1alpha's relationship with skeletal muscle palmitate oxidation is not present with obesity despite maintained PGC-1alpha and PGC-1beta protein.
Reduced skeletal muscle mitochondrial content and fatty acid oxidation are associated with obesity and insulin resistance. Although the exact mechanisms remain elusive, this may result from impaired mitochondrial biogenesis or reductions in the mitochondrial reticulum network. Therefore, the purpose of this study was to determine whether the protein contents of various transcription factors, including PGC-1alpha and PGC-1beta and proteins associated with mitochondrial fusion events, were reduced in skeletal muscle of nine obese (BMI = 37.6 +/- 2.2 kg/m(-2)) compared with nine age-matched lean (BMI = 23.3 +/- 0.7 kg/m(-2)) women. The protein contents of PGC-1alpha, PGC-1beta, PPARalpha, and tFAM were not reduced with obesity. In contrast, PPARgamma was increased (+22%, P < 0.05) with obesity, and there was a trend toward an increase (+31%, P = 0.13) in PPARdelta/beta. In lean individuals, PGC-1alpha protein correlated with citrate synthase (CS; r = 0.67) and rates of palmitate oxidation (r = 0.87), whereas PGC-1beta correlated with PPARgamma (r = 0.90), PPARdelta/beta (r = 0.63), and cytochrome c oxidase IV (COX-IV; r = 0.63). In obese individuals, the relationship between PGC-1alpha and CS was maintained (r = 0.65); however, the associations between PGC-1alpha and palmitate oxidation (r = -0.38) and PGC-1beta with PPARgamma (r = 0.14), PPARdelta/beta (r = 0.21), and COX-IV (r = 0.01) were lost. In addition, mitofusin-1 (MFN-1), MFN-2, and dynamin-related protein-1 (DRP-1) total protein contents were not altered with obesity (P > 0.05). These data suggest that altered regulation, and not reductions in the protein contents of transcription factors, is associated with insulin resistance. Also, it does not appear that alterations in the proteins associated with mitochondrial network formation and degradation can account for the observed decrease in mitochondrial content.
Holloway
Graham P
GP
Human Health & Nutritional Sciences, University of Guelph, Guelph, ON, Canada. ghollowa@uoguelph.ca
Perry
Christopher G R
CG
Thrush
A Brianne
AB
Heigenhauser
George J F
GJ
Dyck
David J
DJ
Bonen
Arend
A
Spriet
Lawrence L
LL
D015153:Blotting, Western; D002950:Citrate (si)-Synthase / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D034281:Dynamins; D005260:Female; D020558:GTP Phosphohydrolases / Q000378:metabolism; D006360:Heat-Shock Proteins / Q000378:metabolism*; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000378:metabolism; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D008875:Middle Aged; D008931:Mitochondria, Muscle / Q000378:metabolism; D033681:Mitochondrial Membrane Transport Proteins; D024101:Mitochondrial Proteins / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000378:metabolism*; D009765:Obesity / Q000378:metabolism*; D010168:Palmitates / Q000378:metabolism*; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; D047492:Peroxisome Proliferator-Activated Receptors / Q000378:metabolism*; D012044:Regression Analysis; D014157:Transcription Factors / Q000378:metabolism*
D004268:DNA-Binding Proteins; D006360:Heat-Shock Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D008869:Microtubule-Associated Proteins; D033681:Mitochondrial Membrane Transport Proteins; D024101:Mitochondrial Proteins; C486497:PPARGC1A protein, human; D010168:Palmitates; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; D047492:Peroxisome Proliferator-Activated Receptors; C499631:TFAM protein, human; D014157:Transcription Factors; D002950:Citrate (si)-Synthase; D020558:GTP Phosphohydrolases; C470018:MFN2 protein, human; C470017:Mfn1 protein, human; C110768:DNM1L protein, human; D034281:Dynamins