Changes in skeletal muscle mitochondria in response to the development of type 2 diabetes or prevention by daily wheel running in hyperphagic OLETF rats.
The temporal changes in skeletal muscle mitochondrial content and lipid metabolism that precede type 2 diabetes are largely unknown. Here we examined skeletal muscle mitochondrial fatty acid oxidation (MitoFAOX) and markers of mitochondrial gene expression and protein content in sedentary 20- and 40-wk-old hyperphagic, obese Otsuka Long-Evans Tokushima fatty (OLETF-SED) rats. Changes in OLETF-SED rats were compared with two groups of rats who maintained insulin sensitivity: age-matched OLETF rats given access to voluntary running wheels (OLETF-EX) and sedentary, nonobese Long-Evans Tokushima Otsuka (LETO-SED) rats. As expected, glucose tolerance tests revealed insulin resistance at 20 wk that progressed to type 2 diabetes at 40 wk in the OLETF-SED, whereas both the OLETF-EX and LETO-SED maintained whole body insulin sensitivity. At 40 wk, complete MitoFAOX (to CO(2)), beta-hydroxyacyl-CoA dehydrogenase activity, and citrate synthase activity did not differ between OLETF-SED and LETO-SED but were significantly (P < 0.05) higher in OLETF-EX compared with OLETF-SED rats. Genes controlling skeletal muscle MitoFAOX (PGC-1alpha, PPARdelta, mtTFA, cytochrome c) were not different between OLETF-SED and LETO-SED at any age. Compared with the OLETF-SED, the OLETF-EX rats had significantly (P < 0.05) higher skeletal muscle PGC-1alpha, cytochrome c, and mtTFA mRNA levels at 20 and 40 wk and PPARdelta at 40 wk; however, protein content for each of these markers did not differ between groups at 40 wk. Limited changes in skeletal muscle mitochondria were observed during the transition from insulin resistance to type 2 diabetes in the hyperphagic OLETF rat. However, diabetes prevention through increased physical activity appears to be mediated in part through maintenance of skeletal muscle mitochondrial function.
Harry S. Truman Memorial VA Hospital, Division of Gastroenterology and Hepatology, University of Missouri, Columbia, MO 65201, USA.
R Scott
RS
Rector
Grace M
GM
Uptergrove
Sarah J
SJ
Borengasser
Catherine R
CR
Mikus
E Matthew
EM
Morris
Scott P
SP
Naples
Matthew J
MJ
Laye
M Harold
MH
Laughlin
Frank W
FW
Booth
Jamal A
JA
Ibdah
John P
JP
Thyfault
D015094:3-Hydroxyacyl CoA Dehydrogenases / Q000235:genetics / Q000378:metabolism; D055372:AMP-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism; D000818:Animals; D015153:Blotting, Western; D001823:Body Composition / Q000502:physiology; D002950:Citrate (si)-Synthase / Q000235:genetics / Q000378:metabolism; D003924:Diabetes Mellitus, Type 2 / Q000378:metabolism* / Q000517:prevention & control; D003576:Electron Transport Complex IV / Q000235:genetics / Q000378:metabolism; D005227:Fatty Acids / Q000378:metabolism*; D007333:Insulin Resistance / Q000502:physiology; D008931:Mitochondria, Muscle / Q000201:enzymology / Q000378:metabolism*; D009043:Motor Activity / Q000502:physiology*; D018482:Muscle, Skeletal / Q000201:enzymology / Q000378:metabolism*; D047495:PPAR gamma / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000737:chemistry / Q000235:genetics; D011897:Random Allocation; D051381:Rats; D020334:Rats, Inbred OLETF; D020133:Reverse Transcriptase Polymerase Chain Reaction; D018709:Statistics, Nonparametric
D005227:Fatty Acids; D047495:PPAR gamma; D012333:RNA, Messenger; D015094:3-Hydroxyacyl CoA Dehydrogenases; D003576:Electron Transport Complex IV; D002950:Citrate (si)-Synthase; D055372:AMP-Activated Protein Kinases