title: Metformin-induced stimulation of AMP-activated protein kinase in beta-cells impairs their glucose responsiveness and can lead to apoptosis.
abstract: Metformin is an anti-diabetic drug that increases glucose utilization in insulin-sensitive tissues. The effect is in part attributable to a stimulation of AMP-activated protein kinase (AMPK). The present study demonstrates that metformin (0.5-2mM) also dose-dependently activates AMPK in insulin-producing MIN6 cells and in primary rat beta-cells, leading to increased phosphorylation of acetyl coA carboxylase (ACC). The maximal effect was reached within 12h and sustained up to 48h. After 24h exposure to metformin (0.5-1mM), rat beta-cells exhibited a reduced secretory and synthetic responsiveness to 10mM glucose, which was also the case following 24h culture with the AMPK-activator 5-amino-imidazole-4-carboxamide riboside (AICAR; 1mM). Longer metformin exposure (>24h) resulted in a progressive increase in apoptotic beta-cells as was also reported for AICAR; metformin-induced apoptosis was reduced by compound C, an AMPK-inhibitor. As with AICAR, metformin activated c-Jun-N-terminal kinase (JNK) and caspase-3 prior to the appearance of apoptosis. It is concluded that metformin-induced AMPK-activation in beta-cells reduces their glucose responsiveness and may, following sustained exposure, result in apoptosis.
authors.affiliation: Diabetes Research Center, Partner of the Juvenile Diabetes Research Center for Beta-cell Therapy in Europe, Brussels Free University-VUB, Laarbeeklaan 103, B-1090 Brussels, Belgium.
authors.forename: Benjamin A
authors.initials: BA
authors.lastname: Kefas
authors.forename: Ying
authors.initials: Y
authors.lastname: Cai
authors.forename: Karen
authors.initials: K
authors.lastname: Kerckhofs
authors.forename: Zhidong
authors.initials: Z
authors.lastname: Ling
authors.forename: Geert
authors.initials: G
authors.lastname: Martens
authors.forename: Harry
authors.initials: H
authors.lastname: Heimberg
authors.forename: Daniël
authors.initials: D
authors.lastname: Pipeleers
authors.forename: Mark
authors.initials: M
authors.lastname: Van de Casteele
mesh_terms: D055372:AMP-Activated Protein Kinases; D000818:Animals; D017209:Apoptosis; D004789:Enzyme Activation / Q000187:drug effects; D005260:Female; D005947:Glucose / Q000378:metabolism*; D007004:Hypoglycemic Agents / Q000494:pharmacology; D007328:Insulin / Q000378:metabolism; D007515:Islets of Langerhans / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology; D048031:JNK Mitogen-Activated Protein Kinases; D008687:Metformin / Q000494:pharmacology*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009097:Multienzyme Complexes / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar
chemical_list: D007004:Hypoglycemic Agents; D007328:Insulin; D009097:Multienzyme Complexes; D008687:Metformin; D017346:Protein Serine-Threonine Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D055372:AMP-Activated Protein Kinases; D005947:Glucose