alpha-lipoic acid regulates AMP-activated protein kinase and inhibits insulin secretion from beta cells. 2006

E D Targonsky, and F Dai, and V Koshkin, and G T Karaman, and A V Gyulkhandanyan, and Y Zhang, and C B Chan, and M B Wheeler
Department of Physiology, University of Toronto, 1 King's College Circle, Toronto, ON, Canada, M5S 1A8.

OBJECTIVE The antioxidant compound alpha-lipoic acid (alpha-LA) possesses antidiabetic and anti-obesity properties. In the hypothalamus, alpha-LA suppresses appetite and prevents obesity by inhibiting AMP-activated protein kinase (AMPK). Given the therapeutic potential of alpha-LA for the treatment of type 2 diabetes and obesity, and the importance of AMPK in beta cells, we examined the effect of alpha-LA on pancreatic beta cell function. METHODS Isolated rat islets and MIN6 beta cells were treated acutely (15-90 min) or chronically (18-24 h) with alpha-LA or the known AMPK-activating compounds 5'-amino-imidazole-4-carboxamide ribonucleoside (AICAR) and metformin. Insulin secretion, the AMPK-signalling pathway, mitochondrial function and cell growth were assessed. RESULTS Acute or chronic treatment of islets and MIN6 cells with alpha-LA led to dose-dependent rises in phosphorylation of the AMPK alpha-subunit and acetyl CoA carboxylase. Chronic exposure to alpha-LA, AICAR or metformin caused a reduction in insulin secretion. alpha-LA inhibited the p70 s6 kinase translational control pathway, and inhibited MIN6 growth in a manner similar to rapamycin. Unlike AICAR and metformin, alpha-LA also acutely inhibited insulin secretion. Examination of the effect of alpha-LA on mitochondrial function showed that acute treatment with this compound elevated reactive oxygen species (ROS) production and enhanced mitochondrial depolarisation induced by Ca(2+). CONCLUSIONS This study is the first to demonstrate that alpha-LA directly affects beta cell function. The chronic effects of alpha-LA include AMPK activation and reductions in insulin secretion and content, and cell growth. Acutely, alpha-LA also inhibits insulin secretion, an effect probably involving the ROS-induced impairment of mitochondrial function.

UI MeSH Term Description Entries
D007328 Insulin A 51-amino acid pancreatic hormone that plays a major role in the regulation of glucose metabolism, directly by suppressing endogenous glucose production (GLYCOGENOLYSIS; GLUCONEOGENESIS) and indirectly by suppressing GLUCAGON secretion and LIPOLYSIS. Native insulin is a globular protein comprised of a zinc-coordinated hexamer. Each insulin monomer containing two chains, A (21 residues) and B (30 residues), linked by two disulfide bonds. Insulin is used as a drug to control insulin-dependent diabetes mellitus (DIABETES MELLITUS, TYPE 1). Iletin,Insulin A Chain,Insulin B Chain,Insulin, Regular,Novolin,Sodium Insulin,Soluble Insulin,Chain, Insulin B,Insulin, Sodium,Insulin, Soluble,Regular Insulin
D008063 Thioctic Acid An octanoic acid bridged with two sulfurs so that it is sometimes also called a pentanoic acid in some naming schemes. It is biosynthesized by cleavage of LINOLEIC ACID and is a coenzyme of oxoglutarate dehydrogenase (KETOGLUTARATE DEHYDROGENASE COMPLEX). It is used in DIETARY SUPPLEMENTS. Lipoic Acid,Alpha-Lipogamma,Alpha-Lipon Stada,Alpha-Liponsaure Sofotec,Alpha-Lippon AL,Alphaflam,Azulipont,Fenint,Juthiac,Liponsaure-ratiopharm,MTW-Alphaliponsaure,Neurium,Pleomix-Alpha,Pleomix-Alpha N,Thioctacid,Thioctacide T,Thiogamma Injekt,Thiogamma oral,Tromlipon,Verla-Lipon,alpha-Lipoic Acid,alpha-Liponaure Heumann,alpha-Liponsaure von ct,alpha-Vibolex,biomo-lipon,duralipon,espa-lipon,Acid, alpha-Lipoic,Alpha Lipogamma,Alpha Lipon Stada,Alpha Liponsaure Sofotec,Alpha Lippon AL,AlphaLipogamma,AlphaLipon Stada,AlphaLiponsaure Sofotec,AlphaLippon AL,Injekt, Thiogamma,Liponsaure ratiopharm,Liponsaureratiopharm,MTW Alphaliponsaure,MTWAlphaliponsaure,Pleomix Alpha,Pleomix Alpha N,PleomixAlpha,PleomixAlpha N,Verla Lipon,VerlaLipon,alpha Lipoic Acid,alpha Liponaure Heumann,alpha Liponsaure von ct,alpha Vibolex,alphaLiponaure Heumann,alphaLiponsaure von ct,alphaVibolex,biomo lipon,biomolipon,espa lipon,espalipon
D008297 Male Males
D008810 Mice, Inbred C57BL One of the first INBRED MOUSE STRAINS to be sequenced. This strain is commonly used as genetic background for transgenic mouse models. Refractory to many tumors, this strain is also preferred model for studying role of genetic variations in development of diseases. Mice, C57BL,Mouse, C57BL,Mouse, Inbred C57BL,C57BL Mice,C57BL Mice, Inbred,C57BL Mouse,C57BL Mouse, Inbred,Inbred C57BL Mice,Inbred C57BL Mouse
D008954 Models, Biological Theoretical representations that simulate the behavior or activity of biological processes or diseases. For disease models in living animals, DISEASE MODELS, ANIMAL is available. Biological models include the use of mathematical equations, computers, and other electronic equipment. Biological Model,Biological Models,Model, Biological,Models, Biologic,Biologic Model,Biologic Models,Model, Biologic
D009097 Multienzyme Complexes Systems of enzymes which function sequentially by catalyzing consecutive reactions linked by common metabolic intermediates. They may involve simply a transfer of water molecules or hydrogen atoms and may be associated with large supramolecular structures such as MITOCHONDRIA or RIBOSOMES. Complexes, Multienzyme
D011494 Protein Kinases A family of enzymes that catalyze the conversion of ATP and a protein to ADP and a phosphoprotein. Protein Kinase,Kinase, Protein,Kinases, Protein
D002478 Cells, Cultured Cells propagated in vitro in special media conducive to their growth. Cultured cells are used to study developmental, morphologic, metabolic, physiologic, and genetic processes, among others. Cultured Cells,Cell, Cultured,Cultured Cell
D000078790 Insulin Secretion Production and release of insulin from PANCREATIC BETA CELLS that primarily occurs in response to elevated BLOOD GLUCOSE levels. Secretion, Insulin
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia

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