title: Time-dependent effects of Prkce deletion on glucose homeostasis and hepatic lipid metabolism on dietary lipid oversupply in mice.
abstract: OBJECTIVE
  We examined the time-dependent effects of deletion of the gene encoding protein kinase C epsilon (Prkce) on glucose homeostasis, insulin secretion and hepatic lipid metabolism in fat-fed mice.
  
  
  METHODS
  Prkce(-/-) and wild-type (WT) mice were fed a high-fat diet for 1 to 16 weeks and subjected to i.p. glucose tolerance tests (ipGTT) and indirect calorimetry. We also investigated gene expression and protein levels by RT-PCR, quantitative protein profiling (isobaric tag for relative and absolute quantification; iTRAQ) and immunoblotting. Lipid levels, mitochondrial oxidative capacity and lipid metabolism were assessed in liver and primary hepatocytes.
  
  
  RESULTS
  While fat-fed WT mice became glucose intolerant after 1 week, Prkce(-/-) mice exhibited normal glucose and insulin levels. iTRAQ suggested differences in lipid metabolism and oxidative phosphorylation between fat-fed WT and Prkce(-/-) animals. Liver triacylglycerols were increased in fat-fed Prkce(-/-) mice, resulting from altered lipid partitioning which promoted esterification of fatty acids in hepatocytes. In WT mice, fat feeding elevated oxygen consumption in vivo and in isolated liver mitochondria, but these increases were not seen in Prkce(-/-) mice. Prkce(-/-) hepatocytes also exhibited reduced production of reactive oxygen species (ROS) in the presence of palmitate. After 16 weeks of fat feeding, however, the improved glucose tolerance in fat-fed Prkce(-/-) mice was instead associated with increased insulin secretion during ipGTT, as we have previously reported.
  
  
  CONCLUSIONS
  Prkce deletion ameliorates diet-induced glucose intolerance via two temporally distinct phenotypes. Protection against insulin resistance is associated with changes in hepatic lipid partitioning, which may reduce the acute inhibitory effects of fatty acid catabolism, such as ROS generation. In the longer term, enhancement of glucose-stimulated insulin secretion prevails.
authors.affiliation: Garvan Institute of Medical Research, 384 Victoria Street, Sydney, NSW 2010, Australia. k.raddatz@garvan.org.au
authors.forename: K
authors.initials: K
authors.lastname: Raddatz
authors.forename: N
authors.initials: N
authors.lastname: Turner
authors.forename: G
authors.initials: G
authors.lastname: Frangioudakis
authors.forename: B M
authors.initials: BM
authors.lastname: Liao
authors.forename: D J
authors.initials: DJ
authors.lastname: Pedersen
authors.forename: J
authors.initials: J
authors.lastname: Cantley
authors.forename: D
authors.initials: D
authors.lastname: Wilks
authors.forename: E
authors.initials: E
authors.lastname: Preston
authors.forename: B D
authors.initials: BD
authors.lastname: Hegarty
authors.forename: M
authors.initials: M
authors.lastname: Leitges
authors.forename: M J
authors.initials: MJ
authors.lastname: Raftery
authors.forename: T J
authors.initials: TJ
authors.lastname: Biden
authors.forename: C
authors.initials: C
authors.lastname: Schmitz-Peiffer
mesh_terms: D000818:Animals; D004041:Dietary Fats / Q000378:metabolism*; D017353:Gene Deletion; D005947:Glucose / Q000378:metabolism*; D006706:Homeostasis / Q000502:physiology*; D007328:Insulin / Q000378:metabolism; D050356:Lipid Metabolism / Q000502:physiology*; D008099:Liver / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D023421:Models, Animal; D051744:Protein Kinase C-epsilon / Q000172:deficiency* / Q000235:genetics; D017382:Reactive Oxygen Species / Q000378:metabolism; D013997:Time Factors
chemical_list: D004041:Dietary Fats; D007328:Insulin; D017382:Reactive Oxygen Species; C497256:Prkce protein, mouse; D051744:Protein Kinase C-epsilon; D005947:Glucose