1 / 19

Glycogen Metabolism Storage and Mobilization of Glucose

Glycogen Metabolism Storage and Mobilization of Glucose. NUTR 543 – Advanced Nutritional Biochemistry David L. Gee, PhD Professor of Food Science and Nutrition Department of Health, Human Performance, and Nutrition Central Washington University. Glycogen Functions. Liver

omer
Télécharger la présentation

Glycogen Metabolism Storage and Mobilization of Glucose

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Glycogen Metabolism Storage and Mobilization of Glucose NUTR 543 – Advanced Nutritional Biochemistry David L. Gee, PhD Professor of Food Science and Nutrition Department of Health, Human Performance, and Nutrition Central Washington University

  2. Glycogen Functions • Liver • Buffer for regulating blood glucose levels • Muscle • Store of glucose as a fuel for exercise • high intensity exercise dependent on anaerobic glycolysis

  3. Glycogen SynthesisFigure 12-2

  4. Regulation of Glycogen SynthaseFigure 12-4 • Active/Inactive Forms • Active • dephosphorylated • Inactive • phosphorylated

  5. Regulation of Glycogen SynthaseFastingFigure 12-4 • Glucagon or epinephrine • G-protein linked receptors • increased [cAMP]

  6. Regulation of Glycogen SynthaseFastingFigure 12-4 • cAMP activates Protein Kinase A • Protein kinase A phosphorylates and inactivates glycogen synthase • Little glycogen synthesis during fasting

  7. Regulation of Glycogen SynthaseFeedingFigure 12-4 • Insulin • Reduces [cAMP] • Stimulates phosphodiesterase • Induces and activates protein phosphatase-1 • Activates GS • Feeding results in glycogen synthesis

  8. Glycogen Degradation • Glycogen Phosphorylase • Hydrolyzes glucose units from glycogen • Produces glucose-1-P • Removal of branch points • Debranching enzyme complex • Glucan transferase • Alpha-1,6-glucosidase

  9. Regulation of Glycogen PhosphorylaseFastingFigure 12-7 • Glucagon or epinephrine • Increase [cAMP] • Activates Protein Kinase A • Phosphorylates and activates glycogen phosphorylase • Fasting results in increased glycogenolysis

  10. Regulation of Glycogen PhosphorylaseFeedingFigure 12-7 • Insulin • Reduces [cAMP] • Induces and activates Protein Phosphatase-1 • Inactivates Glycogen Phosphorylase • Feeding results in decreased glycogenolysis

  11. Allosteric Regulation of Glycogen PhosphorylaseTable 12-1

  12. Regulation of Glycogen Degradation during ExerciseFigure 12-8

  13. Coordinated Regulation of Glycogen Metabolism (Table 12-2)

  14. Application:Pharmacological Agents for Diabetics • Insulin • Mandatory for Type 1 diabetics • Used in Type 2 diabetics as oral medications become less effective • Oral medications • Mechanisms • Increase insulin production • Improve insulin receptor sensitivity • Inhibit gluconeogenesis • Inhibit carbohydrate absorption

  15. Sulfonylureas • First widely used diabetic drug • Stimulates endogenous release of insulin from pancreas • Direct action on ATP-K channel protein on beta-cells • Short and longer acting forms • Glipizide (Glucotrol), glyburide (Diabeta), tolazamide (Tolinase) • Side Effects • Hypoglycemia • Weight gain

  16. Meglitinides • Like sulfonylureas, stimulate pancreatic secretion of insulin • Short-acting: taken with meals • Replaglinide (Prandin) • Side Effects • Hypoglycemia • Weight gain

  17. Biguanides • Mechanism of action • Reduces gluconeogenesis (stimulates (?) Protein kinase A) • Decrease absorption of dietary CHO • Increase insulin sensitivity • Metformin (Glucophage) (most widely used anti-diabetic drug) • Side effects (not hypoglycemia) • Lactic acidosis • Contraindicated in heart failure, liver and kidney disorders • Diarrhea • Other facts • Only drug shown to reduced risk diabetes related heart disease • Derived from French lilac (known as useful for treating symptoms of diabetes)

  18. Thiazolidinediones (TZDs) • Mechanism of action • Binds to nuclear receptors that increase transcription of certain genes • Decreased insulin resistance • Leptin levels decreased (increased appetite) • Rosiglitazone (Avandia) • Side effects: edema, risk of hepatitis, increased heart disease risk (5/07 – FDA safety alert)

  19. Incretin mimetic • Incretins are GI hormones that increase insulin production • Exenatide (39aa peptide from saliva of gila monster (lizard spit), synthesized) • 50% homology with Glugacon-Like Peptide (GLP), an incretin that stimulates insulin production and inhibits glucagon production • Self-regulating: active only when during hyperglycemia • Appetite suppresent effect: gradual weight loss • Side effects: • may increase hypoglycemic risk with sulfonylureas • must be injected 2x per day

More Related