Amylin activates glycogen phosphorylase and inactivates glycogen synthase via a cAMP-independent mechanism
| Autor: | Douglas A. Young, Rhonda O. Deems, Richard W. Deacon |
|---|---|
| Rok vydání: | 1991 |
| Předmět: |
Male
endocrine system medicine.medical_specialty Amyloid Glycogenolysis endocrine system diseases Phosphorylases Biophysics macromolecular substances In Vitro Techniques Biochemistry Glycogen debranching enzyme chemistry.chemical_compound Glycogen phosphorylase Internal medicine medicine Glycogen branching enzyme Cyclic AMP Animals Insulin Glycogen synthase Phosphorylase kinase Molecular Biology biology Glycogen Muscles Isoproterenol Rats Inbred Strains Cell Biology Fasting Islet Amyloid Polypeptide Rats Enzyme Activation Kinetics Endocrinology Glycogen Synthase chemistry Glycogenesis biology.protein |
| Zdroj: | Biochemical and biophysical research communications. 174(2) |
| ISSN: | 0006-291X |
| Popis: | Although the novel pancreatic peptide amylin has been shown to induce insulin resistance and decrease glucose uptake, the mechanism of amylin's actions is unknown. The following study evaluated the effect of amylin on glycogen metabolism in isolated soleus muscles in the presence and absence of insulin (200 microU/ml). Total glycogen, glycogen phosphorylase and glycogen synthases activities, and cAMP levels were measured. Total glycogen levels were significantly decreased by amylin (100 nM) in fed or fasted muscles under conditions of insulin stimulation. Amylin (100 nM) activated glycogen phosphorylase by as much as 100% and decreased glycogen synthase activity by over 60%, depending on the metabolic state of the muscles. These effects where comparable to those of the beta adrenergic agonist isoproterenol. A lower concentration of amylin (1 nM) did not significantly affect glycogen levels, glycogen phosphorylase, or glycogen synthase activity. Cyclic AMP levels were increased two-fold by isoproterenol but were unaffected by amylin. In conclusion, amylin induces glycogenolysis by decreasing glycogen synthesis and increasing breakdown. The effect of amylin on enzyme activity is consistent with a phosphorylation-dependent mechanism. It is likely that these events are mediated via a cAMP independent protein kinase. |
| Databáze: | OpenAIRE |
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