title: Chronological approach of diet-induced alterations in muscle mitochondrial functions in rats.
abstract: OBJECTIVE
  Mitochondrial dysfunction might predispose individuals to develop insulin resistance. Our objective was to determine whether mitochondrial dysfunction or insulin resistance was the primary event during high-fat (HF) diet.
  
  
  METHODS
  Rats were fed an HF diet for 0, 3, 6, 9, 14, 20, or 40 days and compared with control. Soleus and tibialis muscle mitochondrial activity were assessed using permeabilized fiber technique. Insulin [area under the curve for insulin (AUC(I))] and glucose [area under the curve for glucose (AUC(G))] responses to intraperitoneal glucose tolerance test as well as fasting plasma non-esterified fatty acids (NEFAs), triglyceride, and glycerol concentrations were determined.
  
  
  RESULTS
  AUC(I) and AUC(G) were altered from Day 6 (p < 0.01 vs. Day 0). In soleus, oxidative phosphorylation (OXPHOS) activity was transiently enhanced by 26% after 14 days of HF diet (p < 0.05 vs. Day 0) conjointly with 62% increase in NEFA concentration (p < 0.05 vs. Day 0). This was associated with normalized AUC(G) at Day 14 and with a decline of plasma NEFA concentration together with stabilization of intra-abdominal adiposity at Day 20. Prolongation of HF diet again caused an increase in plasma NEFA concentration, intra-abdominal adiposity, AUC(I), and AUC(G). At Day 40, significant decrease in OXPHOS activity was observed in soleus.
  
  
  CONCLUSIONS
  Mitochondria first adapt to overfeeding in oxidative muscle limiting excess fat deposition. This potentially contributes to maintain glucose homeostasis. Persistent overfeeding causes insulin resistance and results in a slow decline in oxidative muscle OXPHOS activity. This shows that the involvement of mitochondria in the predisposition to insulin resistance is mainly due to an inability to face prolonged excess fat delivery.
authors.affiliation: Lipid and Energy Metabolism Research Unit, Human Nutrition Laboratory, Institut National de la Recherche Agronomique, Unité Mixte de Recherche 1019, Clermont-Ferrand, France.
authors.forename: Emilie
authors.initials: E
authors.lastname: Chanséaume
authors.forename: Anne-Laure
authors.initials: AL
authors.lastname: Tardy
authors.forename: Jérôme
authors.initials: J
authors.lastname: Salles
authors.forename: Christophe
authors.initials: C
authors.lastname: Giraudet
authors.forename: Paulette
authors.initials: P
authors.lastname: Rousset
authors.forename: Antoine
authors.initials: A
authors.lastname: Tissandier
authors.forename: Yves
authors.initials: Y
authors.lastname: Boirie
authors.forename: Béatrice
authors.initials: B
authors.lastname: Morio
mesh_terms: D000222:Adaptation, Physiological; D000273:Adipose Tissue / Q000378:metabolism; D000818:Animals; D019540:Area Under Curve; D001786:Blood Glucose / Q000378:metabolism; D004032:Diet; D004041:Dietary Fats / Q000008:administration & dosage*; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005951:Glucose Tolerance Test; D005990:Glycerol / Q000378:metabolism; D007328:Insulin / Q000097:blood; D007333:Insulin Resistance; D050356:Lipid Metabolism / Q000187:drug effects*; D008297:Male; D008931:Mitochondria, Muscle / Q000378:metabolism / Q000502:physiology*; D009765:Obesity / Q000378:metabolism* / Q000503:physiopathology; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors; D014280:Triglycerides / Q000378:metabolism
chemical_list: D001786:Blood Glucose; D004041:Dietary Fats; D005230:Fatty Acids, Nonesterified; D007328:Insulin; D014280:Triglycerides; D005990:Glycerol