Modifications of Pyruvate Handling in Health and Disease Prof. Mary Sugden

Transcription

1 Modifications of Handling Modifications of Handling Centre for Diabetes and Metabolic Medicine Institute of Cell and Molecular Science Barts and the London School of Medicine and Dentistry 1 Potential metabolic fates of pyruvate Extracellular glucose Glycogen AAT Alanine 6-P LDH PC ATP synthesis Malonyl-CoA Fatty acids 2 transport Skeletal muscle Glycolytic type II Liver Gluconeogenesis MCT2 Glycolysis MCT4 Skeletal muscle (type 1) Oxidation MCT1 3 The screen versions of these slides have full details of copyright and acknowledgements 1

2 Modifications of Handling dehydrogenase complex CoASH E1 E2 E3 CO 2 NAD NAD CoASH CO 2 The three enzyme components of the complex are: E1: dehydrogenase E2: Dihydrolipoyl transacetylase E3: Dihydrolipoyl dehydrogenase 4 Physiological importance of maintaining flux via 6-P LDH Fatty acids/cholesterol synthesis CYCLE ATP synthesis CO 2 H 2O 5 Impact of excessive flux via Triacylglycerol Extracellular glucose Insulin Lipolysis Glycolysis Fatty acyl-coa cyt CPT 1 PC Fatty acyl-coa mit CYCLE Malonyl-CoA 6 The screen versions of these slides have full details of copyright and acknowledgements 2

3 Modifications of Handling Allosteric regulation of Fatty acids Fatty acyl-coa CoA FAD active NAD FAO CO 2 FADH 2 7 Covalent regulation of CoA NAD CO 2 active PDK PDP Site1 Site2 inactive Site3 8 Mechanisms of activation of NAD CoA CO 2 active PDP inactive Site1 Site2 Site3 Acetyl- CoA Ca 2 Insulin PDP1 PDP2 9 The screen versions of these slides have full details of copyright and acknowledgements 3

4 Modifications of Handling Regulation of PDP isoforms Free Mg 2 K m Mg 2 Free Mg 2 PDP1c 52-kDa PDP1r 96-kDa PDP2 Free Ca 2 PDP1 PDP2 Insulin PDP Exercise Neural/hormonal action active Site1 Site2 inactive Site3 1 Mechanisms of suppression of CoA NAD CO 2 active CoA NAD PDK inactive Site1 Site2 Site3 PDK1 PDK3 Acetyl- CoA 11 PDK expression Heart Brain Spleen Lung Liver Sk. muscle Kidney Testis Heart Brain Spleen Lung Liver Sk. muscle Kidney Testis A. B. C. D. A: PDK1 B: C: PDK3 D: R.A. Harris and co-workers, Biochem. J., 329: The screen versions of these slides have full details of copyright and acknowledgements 4

5 Modifications of Handling Site specificity of phosphorylation PDK1 Site 1 (ser 264) Site 2 (ser 271) E1α Site 3 (ser 23) 13 Multisite phosphorylation by may impair re-activation PDHa (% of fed value) Site 1 phosphorylated Site 2 phosphorylated Time of insulin stimulation Site 1 PDP Site 2 E1α Site 3 14 Increased lipid availability Potential transcription factors regulating expression: PPARα PPARα PPARα RXR promoter Fibrates, WY14,643 Hepatic protein expression (relative abundance) Fed Starved Wild type PPARα null FedStarved FedStarved (24 h) (24 h) 15 Wild type PPARα null The screen versions of these slides have full details of copyright and acknowledgements 5

6 Modifications of Handling Studies of PDK expression in Morris hepatoma 78 C1 cells Dexamethasone Insulin promoter promoter PPPARα RXR WY14,643 R.A. Harris and co-workers, Diabetes 51: Regulation of expression by glucocorticoids and insulin Insulin FOXO PI3K PKB FOXO IRSs promoter GRE GR GC R.A. Harris and co-workers, Diabetes 53: Consequence of a low activity (liver) Glycogen output 6-P Gluconeogenesis Circulating lactate 18 The screen versions of these slides have full details of copyright and acknowledgements 6

7 Modifications of Handling Anaplerosis and cataplerosis PC (4C) (2C) intermediates Increased intermediates ATP synthesis 19 carboxylase O O C C O - O CO 2 H 2O PC C C O - O H CH 3 ATP ATP P i CH 2 C O - O 2 Physiological roles of cataplerosis in liver LDH PC Fatty acids/ cholesterol Malate MDH Malate Malonyl-CoA α -ketoglutarate 21 The screen versions of these slides have full details of copyright and acknowledgements 7

8 Modifications of Handling Insulin secretion in relation to pyruvate handling Malonyl-CoA Malate NAD LDH PC Malate 22 /fatty-acid high lipid utilisation Extracellular glucose Triacylglycerol Intracellular glucose Lipolysis Glycolysis Fatty acids LDH PC β-oxidation Fatty acyl-coa 23 Upregulation of PDK expression PDK1 PDK3 Soleus ADL Heart F S F S F S F: fed S: starved promoter Increased expression in liver, kidney promoter Increased expression in liver and kidney 24 The screen versions of these slides have full details of copyright and acknowledgements 8

9 Modifications of Handling Acute regulation of PDK by metabolites CoA CoA NAD NAD NAD PDK1 25 PDK isoform shifts modify the sensitivity of feed-forward activation of by pyruvate 1 Soleus protein expression (fold change vs. control) Fed Starved Soleus active % of total Fed Starved concn. (mm) 26 Potential transcription factors regulating expression in muscle: PGC-1α Increased energy production PGC-1α PGC-1α ERRα ERRα promoter D.P. Kelly and co-workers, Mol. Cell Biol. 25: The screen versions of these slides have full details of copyright and acknowledgements 9

10 Modifications of Handling PPARα signalling has no obligatory participation in the regulation of skeletal-muscle pyruvate disposition Soleus muscle protein expression (relative abundance) Fed Wild type Starved PPARα null Fed Starved Fed Starved (24 h) (24 h) Wild type PPARα null 28 Skeletal muscle fuel handling Euglycaemic - hyperinsulinaemic clamp metabolism (mg/min per kg) Splanchnic Adipose Muscle Brain Normal Type 2 diabetes 29 Insulin resistance is associated with metabolic inflexibility with respect to pyruvate disposal oxidation 1 Leg RQ.9.8 Fat oxidation.7 Lean Plus insulin Obese Insulin resistant Fasting Kelley, D. E., J. Clin. Invest. 115: (25) 3 The screen versions of these slides have full details of copyright and acknowledgements 1

11 Modifications of Handling Dietary insulin resistance modifies muscle PDK and regulatory characteristics Soleus muscle protein expression (fold change vs. control) Soleus muscle activity (% of total) concn. (mm) Site 1 (ser 264) Site 2 (ser 271) E1α 31 Consequences of upregulation Starvation Insulin-resistance Dietary carbohydrate Hyperglycaemia Gut Glycolysis Cori Gluconeogenesis Liver Cori Glycolysis 32 Disorders of pyruvate handling: deficiencies LDH E1α gene mutation Thiamine (B 1) deficiency accumulation Lactic acidosis Decreased ATP synthesis Neurological disorders 33 The screen versions of these slides have full details of copyright and acknowledgements 11

12 Modifications of Handling Disorders of pyruvate handling: PC deficiencies Group A: mostly North American Indians, common 1828G>A mutation Group B: European, mainly French Group C: intermittent lactic acidosis Hypoglycaemia PC LDH Lactic acidosis Impaired ATP synthesis The screen versions of these slides have full details of copyright and acknowledgements 12