Defining the Contribution of AMP-activated Protein Kinase (AMPK) and Protein Kinase C (PKC) in Regulation of Glucose Uptake by Metformin in Skeletal Muscle Cells*

Autor: Alexander Gray, Olivier Drouin, André Marette, Maria L. Watson, Louise Lantier, Harinder S. Hundal, Charlotte J. Green, Benoit Viollet, Sophie Turban, Fiona A. Ross, Clare Stretton, D. Grahame Hardie
Jazyk: angličtina
Rok vydání: 2012
Předmět:
Time Factors
endocrine system diseases
Glucose uptake
Muscle Fibers
Skeletal
Phenformin
AMP-Activated Protein Kinases
Biochemistry
chemistry.chemical_compound
Mice
Phosphatidylinositol 3-Kinases
0302 clinical medicine
Glucose Transport
AMP-activated protein kinase
Insulin
Phosphorylation
Cells
Cultured
Protein Kinase C
Phosphoinositide-3 Kinase Inhibitors
Mice
Knockout
0303 health sciences
biology
Metabolic Regulation
digestive
oral
and skin physiology
Metformin
3. Good health
medicine.anatomical_structure
Signal Transduction
medicine.medical_specialty
Skeletal Muscle
Enzyme Activators
030209 endocrinology & metabolism
03 medical and health sciences
Internal medicine
medicine
Animals
Hypoglycemic Agents
Protein kinase A
Molecular Biology
Protein kinase C
030304 developmental biology
AMPK
Skeletal muscle
nutritional and metabolic diseases
Cell Biology
Ribonucleotides
Aminoimidazole Carboxamide
Enzyme Activation
Endocrinology
Glucose
chemistry
biology.protein
Insulin Resistance
Zdroj: The Journal of Biological Chemistry
ISSN: 1083-351X
0021-9258
Popis: Background: The role of AMPK and PKCs as effectors of metformin action on glucose uptake (GU) in skeletal muscle cells was investigated. Results: Genetic loss/silencing of AMPK led to only a small repression in metformin-stimulated GU. Novel/conventional, but not atypical, PKCs support metformin-induced stimulation of GU. Conclusion: Metformin enhances GU by a mechanism largely independent of AMPK. Significance: Metformin can act via non-AMPK pathways to promote GU.
The importance of AMP-activated protein kinase (AMPK) and protein kinase C (PKC) as effectors of metformin (Met) action on glucose uptake (GU) in skeletal muscle cells was investigated. GU in L6 myotubes was stimulated 2-fold following 16 h of Met treatment and acutely enhanced by insulin in an additive fashion. Insulin-stimulated GU was sensitive to PI3K inhibition, whereas that induced by Met was not. Met and its related biguanide, phenformin, stimulated AMPK activation/phosphorylation to a level comparable with that induced by the AMPK activator, 5-amino-1-β-d-ribofuranosyl-imidazole-4-carboxamide (AICAR). However, the increase in GU elicited by AICAR was significantly lower than that induced by either biguanide. Expression of a constitutively active AMPK mimicked the effects of AICAR on GU, whereas a dominant interfering AMPK or shRNA silencing of AMPK prevented AICAR-stimulated GU and Met-induced AMPK signaling but only repressed biguanide-stimulated GU by ∼20%. Consistent with this, analysis of GU in muscle cells from α1−/−/α2−/− AMPK-deficient mice revealed a significant retention of Met-stimulated GU, being reduced by ∼35% compared with that of wild type cells. Atypical PKCs (aPKCs) have been implicated in Met-stimulated GU, and in line with this, Met and phenformin induced activation/phosphorylation of aPKC in L6 myotubes. However, although cellular depletion of aPKC (>90%) led to loss in biguanide-induced aPKC phosphorylation, it had no effect on Met-stimulated GU, whereas inhibitors targeting novel/conventional PKCs caused a significant reduction in biguanide-induced GU. Our findings indicate that although Met activates AMPK, a significant component of Met-stimulated GU in muscle cells is mediated via an AMPK-independent mechanism that involves novel/conventional PKCs.
Databáze: OpenAIRE
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