PDK1-Foxo1 in agouti-related peptide neurons regulates energy homeostasis by modulating food intake and energy expenditure

PLoS One. 2011;6(4):e18324. doi: 10.1371/journal.pone.0018324. Epub 2011 Apr 7.

Abstract

Insulin and leptin intracellular signaling pathways converge and act synergistically on the hypothalamic phosphatidylinositol-3-OH kinase/3-phosphoinositide-dependent protein kinase 1 (PDK1). However, little is known about whether PDK1 in agouti-related peptide (AGRP) neurons contributes to energy homeostasis. We generated AGRP neuron-specific PDK1 knockout (AGRPPdk1(-/-)) mice and mice with selective expression of transactivation-defective Foxo1 (Δ256Foxo1(AGRP)Pdk1(-/-)). The AGRPPdk1(-/-) mice showed reductions in food intake, body length, and body weight. The Δ256Foxo1(AGRP)Pdk1(-/-) mice showed increased body weight, food intake, and reduced locomotor activity. After four weeks of calorie-restricted feeding, oxygen consumption and locomotor activity were elevated in AGRPPdk1(-/-) mice and reduced in Δ256Foxo1(AGRP)Pdk1(-/-) mice. In vitro, ghrelin-induced changes in [Ca(2+)](i) and inhibition of ghrelin by leptin were significantly attenuated in AGRPPdk1(-/-) neurons compared to control neurons. However, ghrelin-induced [Ca(2+)](i) changes and leptin inhibition were restored in Δ256Foxo1(AGRP)Pdk1(-/-) mice. These results suggested that PDK1 and Foxo1 signaling pathways play important roles in the control of energy homeostasis through AGRP-independent mechanisms.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 3-Phosphoinositide-Dependent Protein Kinases
  • Agouti-Related Protein / metabolism*
  • Animals
  • Calcium / metabolism
  • Caloric Restriction
  • Eating* / drug effects
  • Energy Metabolism* / drug effects
  • Female
  • Forkhead Box Protein O1
  • Forkhead Transcription Factors / metabolism*
  • Gene Knockout Techniques
  • Ghrelin / pharmacology
  • Homeostasis / drug effects
  • Intracellular Space / drug effects
  • Intracellular Space / metabolism
  • Leptin / metabolism
  • Male
  • Melanocortins / metabolism*
  • Mice
  • Neurons / cytology
  • Neurons / drug effects
  • Neurons / metabolism*
  • Neuropeptides / metabolism
  • Phenotype
  • Protein Serine-Threonine Kinases / deficiency
  • Protein Serine-Threonine Kinases / genetics
  • Protein Serine-Threonine Kinases / metabolism*
  • Protein Transport / drug effects
  • Rats
  • Signal Transduction / drug effects
  • Transcriptional Activation / drug effects

Substances

  • Agouti-Related Protein
  • Forkhead Box Protein O1
  • Forkhead Transcription Factors
  • Foxo1 protein, mouse
  • Ghrelin
  • Leptin
  • Melanocortins
  • Neuropeptides
  • 3-Phosphoinositide-Dependent Protein Kinases
  • Pdpk1 protein, mouse
  • Pdpk1 protein, rat
  • Protein Serine-Threonine Kinases
  • Calcium