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Seong Min Han  (Han SM) 3 Articles
AMPK Activator AICAR Inhibits Hepatic Gluconeogenesis and Fatty Acid Oxidation.
Jin Yob Kim, Eun Hee Koh, Woo Je Lee, Seong Min Han, Ji Young Youn, Hye Sun Park, Hyun Sik Kim, Min Seon Kim, Joong Yeol Park, Ki Up Lee
Korean Diabetes J. 2005;29(1):6-14.   Published online January 1, 2005
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BACKGROUND
Recent studies have demonstrated that adiponectin and metformin activate AMPK in the liver, and adiponectin and metformin stimulate fatty acid oxidation while inhibiting glucose production in liver. These results are in contrast to previous studies that have demonstrated that increased fatty acid oxidation in the liver is associated with increased gluconeogenesis. The present study was undertaken to reinvestigate the effects of AMPK activation by AICAR on hepatic fatty acid oxidation and gluconeogenesis. METHODS: HePG2 cells were treated with various concentrations of AICAR, and then the fatty acid oxidation and gluconeogenesis of the cells were determined. To investigate the in vivo effect of AICAR, Sprague-Dawely rats were infused with AICAR (bolus, 40 mg/g; constant, 7.5 mg/g/min-1) for 90min. RESULTS: Incubation of the HePG2 cells with higher concentrations (=1 mM) of AICAR increased fatty acid oxidation and gluconeogenesis. On the other hand, incubation of HePG2 cells with lower concentrations (0.05 and 0.1 mM) of AICAR decreased fatty acid oxidation and gluconeogenesis. Consistent with this in vitro data, the intravenous administration of AICAR to rats lowered their plasma glucose concentration and inhibited hepatic gluconeogenesis. Fatty acid oxidation in the liver tissue was significantly decreased by the administration of AICAR. CONCLUSION: The present study has demonstrated that AICAR decreased gluconeo-genesis in the liver. In contrast to previous studies, AICAR profoundly decreased hepatic fatty acid oxidation in rats and also in cultured hepatocytes
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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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
Potential Role of Leptin Resistance in Metabolic Syndrome.
Seong Min Han, Joong Yeol Park
Korean Diabetes J. 2003;27(4):304-312.   Published online August 1, 2003
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Diabetes Metab J : Diabetes & Metabolism Journal