Diabetes Metab J > Volume 31(4); 2007 > Article
Korean Diabetes Journal 2007;31(4):310-318.
DOI: https://doi.org/10.4093/jkda.2007.31.4.310    Published online July 1, 2007.
AICAR Reversed the Glucolipotoxicity Induced beta-cell Dysfunction through Suppression of PPAR-gamma-coactivator-1 (PGC-1) Overexpression.
Hyuk Sang Kwon, Ji Won Kim, Heon Seok Park, Seung Hyun Ko, Bong Yun Cha, Ho Young Son, Kun Ho Yoon
1Department of Internal Medicine, The Catholic University of Korea.
2Catholic Research Institutes of Medical Science, The Catholic University of Korea.
Abstract
BACKGROUND
Glucolipotoxicity plays an important role in the progression of type 2 diabetes mellitus via inducing insulin secretory dysfunction. Expression of insulin gene in pancreatic beta cell might be regulated by AMP-activated protein kinase (AMPK), which is recognized as a key molecule of energy metabolism. We studied the effects of AMPK on glucolipotoxicity-induced beta-cell dysfunction by suppression of PPAR-gamma-coactivator-1 (PGC-1) in vitro and in vivo. Method: Glucolipotoxicity was induced by 33.3 mM glucose and 0.6 mM (palmitate and oleate) for 3 days in isolated rat islets. Messenger RNA (mRNA) expressions of beta-cell specific gene like insulin, BETA2/NeuroD and PGC-1 induced by glucolipotoxic condition and their changes with 5-aminoimidazole-4-carboxy-amide-1-D-ribofuranoside (AICAR) treatment were investigated using RT-PCR. We also examined glucose stimulated insulin secretion in same conditions. Furthermore, SD rats were submitted to a 90% partial pancreatectomy (Px) and randomized into two groups; Ad-GFP-infected Px rats (n = 3) and Ad-siPGC- 1-infected Px rats (n = 3). Then, the Px rats were infected with Ad-GFP or Ad-siPGC-1 (1 x 10(9) pfu) via celiac artery. After 12 days of viral infection, we measured body weight and performed the intraperitoneal glucose tolerance test (IP-GTT). RESULTS: Glucolipotoxicity resulted in blunting of glucose-stimulated insulin secretion, which was recovered by the AICAR treatment in vitro. Suppression in their expressions of insulin and BETA2/NeuroD gene by glucolipotoxic condition were improved with AICAR treatment. However, PGC-1alpha expression was gradually increased by glucolipotoxicity, and suppressed by AICAR treatment. Overexpression of PGC-1 using an adenoviral vector in freshly isolated rat islets suppressed insulin gene expression. We also confirmed the function of PGC-1 using an Ad-siPGC-1 in vivo. Direct infection of Ad-siPGC-1 in 90% pancreatectomized rats significantly improved glucose tolerance and increased body weight. CONCLUSION: AMPK could protect against glucolipotoxicity induced beta-cell dysfunction and the suppression of PGC-1 gene expression might involved in the insulin regulatory mechanism by AMPK.
Key Words: AICAR (5-aminoimidazole-4-carboxy-amide-1-D-ribofuranoside), AMP-activated protein Kinase (AMPK), Pancreatectomy, PPAR-gamma-coactivator-1 (PGC-1)
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