Diabetes & Metabolism Journal

Original Articles

The Role of Hypothalamic FoxO1 on Hyperphagia in Streptozotocin-Induced Diabetic Mice.: Il Seong Nam-Goong, Jae Geun Kim, Se Jin Kim, Seong Jae Hur, Jin Woo Lee, Eun Sook Kim, Chang Ho Yun, Byung Ju Lee, Young Il Kim; Korean Diabetes J. 2009;33(5):375-381. Published online October 1, 2009; DOI: https://doi.org/10.4093/kdj.2009.33.5.375

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Abstract PDF: BACKGROUND
Streptozotocin-induced diabetic animals are characterized by hyperphagia due to deficiencies of insulin and leptin. Forkhead box-containing protein of the O subfamily-1 (FoxO1) regulates energy homeostasis by regulating energy expenditure and food intake as well as mediating insulin and leptin signals in the hypothalamus. To identify the mediator of diabetic hyperphagia, we examined the effects of insulin or leptin on hypothalamic FoxO1 expression in a diabetic animal model. METHODS: Diabetes was induced in mice (C57BL/6) by intraperitoneal administration of streptozotocin (200 mg/kg). Stainless steel cannula was implanted into the lateral ventricle of the brain in each mouse. After three weeks, the mice were administered saline, insulin or leptin via intracerebroventricular (ICV) route. The medial hypothalamus was isolated to evaluate the mRNA expressions of FoxO1 and neuropeptides. RESULTS: Streptozotocin-induced diabetic mice exhibited significant elevations of blood glucose and food intake and significantly low levels of serum insulin and leptin. The levels of hypothalamic FoxO1 mRNA were significantly increased in diabetic mice. The hypothalamic expression of neuropeptide Y (NPY) mRNA was increased, but the expression of preproopiomelanocortin (POMC) mRNA was decreased in diabetic mice. ICV administration of insulin or leptin attenuated the upregulation of hypothalamic FoxO1 mRNA, and resulted in downregulation of NPY mRNA and upregulation of POMC mRNA in diabetic mice. CONCLUSION: We observed that the expression of hypothalamic FoxO1 mRNA was increased in streptozotocin-induced diabetic mice, and that it was significantly attenuated by central administration of insulin or leptin. These results suggest that hypothalamic FoxO1 is the direct mediator of diabetic hyperphagia.

Hypothalamic AMPK Activity in Diabetic Rats.: Churl Namkoong, Min Seon Kim, Woo Je Lee, Pil Geum Jang, Seong Min Han, Eun Hee Koh, Joong Yeol Park, Ki Up Lee; Korean Diabetes J. 2004;28(6):468-477. Published online December 1, 2004

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Abstract PDF: 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

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