title: Skeletal muscle respiratory capacity is enhanced in rats consuming an obesogenic Western diet.
abstract: Obesity-induced lipid oversupply promotes skeletal muscle mitochondrial biogenesis. Previous investigations have utilized extreme high-fat diets (HFD) to induce such mitochondrial perturbations despite their disparity from human obesogenic diets. Here, we evaluate the effects of Western diet (WD)-induced obesity on skeletal muscle mitochondrial function. Long-Evans rats were given ad libitum access to either a WD [40% energy (E) from fat, 17% protein, and 43% carbohydrate (30% sucrose); n = 12] or a control diet (CON; 16% of E from fat, 21% protein, and 63% carbohydrate; n = 12) for 12 wk. Rats fed the WD consumed 23% more E than CON (P = 0.0001), which was associated with greater increases in body mass (23%, P = 0.0002) and adiposity (17%, P = 0.03). There were no differences in fasting blood glucose concentration or glucose tolerance between diets, although fasting insulin was increased by 40% (P = 0.007). Fasting serum triglycerides were also elevated in WD (86%, P = 0.001). The maximal capacity of the electron transfer system was greater following WD (37%, P = 0.02), as were the maximal activities of several mitochondrial enzymes (citrate synthase, β-hydroxyacyl-CoA dehydrogenase, carnitine palmitoyltransferase). Protein expression of citrate synthase, UCP3, and individual respiratory complexes was greater after WD (P < 0.05) despite no differences in the expression of peroxisome proliferator-activated receptor (PPAR)α, PPARδ, or PPARγ coactivator-1 mRNA or protein abundance. We conclude that the respiratory capacity of skeletal muscle is enhanced in response to the excess energy supplied by a WD. This is likely due to an increase in mitochondrial density, which at least in the short term, and in the absence of increased energy demand, may protect the tissue from lipid-induced impairments in glycemic control.
authors.affiliation: School of Medical Sciences, Royal Melbourne Institute of Technology University, Bundoora, Australia.
authors.forename: Erin J
authors.initials: EJ
authors.lastname: Stephenson
authors.forename: Donny M
authors.initials: DM
authors.lastname: Camera
authors.forename: Trisha A
authors.initials: TA
authors.lastname: Jenkins
authors.forename: Sepideh
authors.initials: S
authors.lastname: Kosari
authors.forename: Jong Sam
authors.initials: JS
authors.lastname: Lee
authors.forename: John A
authors.initials: JA
authors.lastname: Hawley
authors.forename: Nigel K
authors.initials: NK
authors.lastname: Stepto
mesh_terms: D000818:Animals; D015153:Blotting, Western; D001835:Body Weight / Q000502:physiology; D004032:Diet / Q000009:adverse effects*; D004040:Dietary Carbohydrates / Q000494:pharmacology; D004041:Dietary Fats / Q000494:pharmacology; D002149:Energy Intake / Q000502:physiology; D005215:Fasting / Q000502:physiology; D005951:Glucose Tolerance Test; D006946:Hyperinsulinism / Q000378:metabolism; D008297:Male; D008931:Mitochondria, Muscle / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D018482:Muscle, Skeletal / Q000201:enzymology / Q000378:metabolism*; D009765:Obesity / Q000378:metabolism*; D010101:Oxygen Consumption / Q000502:physiology*; D047495:PPAR gamma / Q000378:metabolism; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; D016601:RNA-Binding Proteins / Q000378:metabolism; D051381:Rats; D020318:Rats, Long-Evans; D060888:Real-Time Polymerase Chain Reaction; D013395:Sucrose / Q000494:pharmacology; D014157:Transcription Factors / Q000378:metabolism; D014280:Triglycerides / Q000378:metabolism
chemical_list: D004040:Dietary Carbohydrates; D004041:Dietary Fats; D047495:PPAR gamma; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; C501429:Ppargc1a protein, rat; D016601:RNA-Binding Proteins; D014157:Transcription Factors; D014280:Triglycerides; D013395:Sucrose