Citrate diminishes hypothalamic acetyl-CoA carboxylase phosphorylation and modulates satiety signals and hepatic mechanisms involved in glucose homeostasis in rats

Life Sci. 2008 Jun 20;82(25-26):1262-71. doi: 10.1016/j.lfs.2008.04.015. Epub 2008 May 6.

Abstract

The hypothalamic AMP-activated protein kinase (AMPK)/acetyl-CoA carboxylase (ACC) pathway is known to play an important role in the control of food intake and energy expenditure. Here, we hypothesize that citrate, an intermediate metabolite, activates hypothalamic ACC and is involved in the control of energy mobilization. Initially, we showed that ICV citrate injection decreased food intake and diminished weight gain significantly when compared to control and pair-fed group results. In addition, we showed that intracerebroventricular (ICV) injection of citrate diminished (80% of control) the phosphorylation of ACC, an important AMPK substrate. Furthermore, citrate treatment inhibited (75% of control) hypothalamic AMPK phosphorylation during fasting. In addition to its central effect, ICV citrate injection led to low blood glucose levels during glucose tolerance test (GTT) and high glucose uptake during hyperglycemic-euglycemic clamp. Accordingly, liver glycogen content was higher in animals given citrate (ICV) than in the control group (23.3+/-2.5 vs. 2.7+/-0.5 microg mL(-1) mg(-1), respectively). Interestingly, liver AMPK phosphorylation was reduced (80%) by the citrate treatment. The pharmacological blockade of beta3-adrenergic receptor (SR 59230A) blocked the effect of ICV citrate and citrate plus insulin on liver AMPK phosphorylation. Consistently with these results, rats treated with citrate (ICV) presented improved insulin signal transduction in liver, skeletal muscle, and epididymal fat pad. Similar results were obtained by hypothalamic administration of ARA-A, a competitive inhibitor of AMPK. Our results suggest that the citrate produced by mitochondria may modulate ACC phosphorylation in the hypothalamus, controlling food intake and coordinating a multiorgan network that controls glucose homeostasis and energy uptake through the adrenergic system.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • AMP-Activated Protein Kinases
  • Acetyl-CoA Carboxylase / metabolism*
  • Animals
  • Body Weight / drug effects
  • Citric Acid / administration & dosage
  • Citric Acid / pharmacology*
  • Corticosterone / blood
  • Feeding Behavior / drug effects
  • Glucose / metabolism*
  • Glucose Tolerance Test
  • Glycogen / metabolism
  • Homeostasis / drug effects*
  • Hypothalamus / drug effects
  • Hypothalamus / enzymology*
  • Injections, Intraventricular
  • Insulin / blood
  • Liver / enzymology
  • Liver / metabolism*
  • Male
  • Multienzyme Complexes / metabolism
  • Phosphorylation / drug effects
  • Propanolamines
  • Protein-Serine-Threonine Kinases / metabolism
  • Rats
  • Rats, Wistar
  • Satiety Response / drug effects*
  • Signal Transduction / drug effects

Substances

  • 3-(2-ethylphenoxy)-1-(1,2,3,4-tetrahydronaphth-1-ylamino)-2-propanol oxalate
  • Insulin
  • Multienzyme Complexes
  • Propanolamines
  • Citric Acid
  • Glycogen
  • Protein-Serine-Threonine Kinases
  • AMP-Activated Protein Kinases
  • Acetyl-CoA Carboxylase
  • Glucose
  • Corticosterone