Hypothalamic AMPK Activity in Diabetic Rats

Namkoong, Churl; Kim, Min Seon; Lee, Woo Je; Jang, Pil Geum; Han, Seong Min; Koh, Eun Hee; Park, Joong Yeol; Lee, Ki Up

Abstract

BACKGROUND: AMP-activated protein kinase (AMPK) acts as a cellular energy sensor that is activated during states of low energy charge and it regulates the various metabolic pathways to reestablish the normal cellular energy balance. It has recently been demonstrated that AMPK activity is altered by the state of energy metabolism in the hypothalamic neurons and this mediates the feeding response.
METHODS
Diabetes was induced by an intra-peritoneal injection of streptozotocin (STZ) in Sprague-Dawley rats. The diabetic rats were maintained for 3 weeks with or without insulin treatment. 3 weeks later, we collected hypothalamus and we then assayed the phosphorylation of AMPK and the activity of acetyl CoA carboxylase (ACC) and isoform-specfic AMPK. To determine the effect of hypothalamic AMPK inhibition on diabetic hyperphagia, we administered an AMPK inhibitor, compound C, into the third ventricle in the STZ-induced diabetic rats.
RESULTS
Phosphorylation of AMPK, which is a marker of AMPK activation, increased in the hypothalamus of the STZ-induced diabetic rats (DR). Moreover, 2-AMPK activity, but not 1-AMPK activity, increased by 2-fold in hypothalamus of the DRs. Phosphorylation of hypothalamic acetyl CoA carboxylase (ACC), a key downstream enzyme of AMPK, also increased in the DRs and this caused a reduction in ACC activity. Insulin treatment completely reversed the diabetesinduced changes in the hypothalamic AMPK and ACC, suggesting that insulin deficiency was associated with the changes in hypothalamic AMPK and ACC. Inhibition of AMPK by an intracerebroventricular administration of AMPK inhibitor, compound C, attenuated the development of diabetic hyperphagia and reduced the blood glucose levels in DRs.
CONCLUSION
We have demonstrated that hypothalamic AMPK activity increased in the DRs, and inhibition of hypothalamic AMPK activity attenuated the development of diabetic hyperphagia. These data indicate that the enhanced hypothalamic AMPK activity may contribute to the development of diabetic hyperphagia