1. Bruno Sopko Alice Skoumalová

2.  Regulation of Carbohydrate metabolism  Hormonal Regulation  Markers  Additional effects

7. Types of regulationsMechanismExample Substrate concentrationSaturation kinetics (Michaelis-Menten equation) Glucokinase (activation after a meal - high K m ) AllostericallyA conformational change after an allosteric activator binding Enzymes of glycolysis and gluconeogenesis (allosteric efectors: ATP, AMP, citrate) Covalent modificationA conformational change after phosphorylation by a protein kinase Phosphorylation of glycogen synthase and glycogen phosphorylase (glucagon) Protein-protein interaction A conformational change after a modulator protein binding Muscle glycogen phosphorylase (activation by Ca 2+ -calmodulin) Zymogen cleavageActivation by proteolysis of a precursor molecule Blood clotting proteins Enzyme synthesisInduction or represion of enzyme synthesis Enzymes of gluconeogenesis (induction during fasting)

8. Glucose homeostasis:  maintenance of blood glucose levels near 80 to 100 mg/dL (4.4-5.6 mmol/l)  insulin and glucagon (regulate fuel mobilization and storage) Hypoglycemia prevention: 1.release of glucose from the large glycogen stores in the liver (glycogenolysis) 2.synthesis of glucose from lactate, glycerol, and amino acids in liver (gluconeogenesis) 3.release of fatty acids from adipose tissue (lipolysis) Hyperglycemia prevention: 1.conversion of glucose to glycogen (glycogen synthesis) 2.conversion of glucose to triacylglycerols in liver and adipose tissue (lipogenesis)

9. Pathways regulated by the release of:  glucagon (in response to a lowering of blood glucose levels)  insulin (in response to an elevation of blood glucose levels)

10.  the islets of Langerhans (β- and α-cells)  preprohormone (modification - in ER, GC, SV)

11. The storage of nutriens glucose transport into muscle and adipose tissue glucose storage as glycogen (liver, muscle) conversion of glucose to TG (liver) and their storage (adipose tissue) protein synthesis (liver, muscle) inhibition of fuel mobilization

12. Insulin receptor signaling:  the tyrosine kinase activity  a dimer (α and ß subunits) Signal transduction: 1. the ß-subunits autophosphorylate each other when insulin binds (activating the receptor) 2. the activated receptor binds and phosphorylates IRS (insulin receptor substrate) 3. multiple binding sites for different proteins

13. Mobilization of energy stores 1.release of glucose from liver glycogen 2.stimulating gluconeogenesis from lactate, glycerol, and amino acids (liver) 3.mobilizing fatty acids (adipose tissue)

14. GlucoseInsulinAmino acids Insulin + + Glucagon --+

15. HormoneFunctionMajor metabolic pathways affected Insulin Promotes fuel storage after a meal Promote growth Stimulates glucose storage as glycogen (muscle,liver) Stimulates FA synthesis and storage after a high-carbohydrate meal Stimulates amino acids uptake and protein synthesis Glucagon Mobilizes fuels Maintains blood glucose levels during fasting Activates gluconeogenesis and glycogenolysis (liver) during fasting Activates FA release from adipose tissue Epinephrine Mobilizes fuels during acute stress Stimulates glucose production from glycogen (muscle, liver) Stimulates FA release from adipose tissue Cortisol Provides for changing requirements over the long- term Stimulates amino acid mobilization from muscle protein Stimulates gluconeogenesis Stimulates FA release from adipose tissue

16. TransporterTissue distributionComments GLUT 1Erythrocytes Blood-brain barier Blood-placentar barier Present in high concentrations GLUT 2Liver Kidney Pancreatic β-cells Intestinal mucosa cells A high K m for glucose The glucose sensor in the pancreas GLUT 3Brain Major transporter in the brain GLUT 4Adipose tissue Sceletal muscle Heart muscle Insulin-sensitive transporter! The number increases on the cell surface. GLUT 5Intestinal epithelium A fructose transporter

17. Binding of insulin to its cell membrane receptor causes vesicles containing glucose transport proteins to move from inside the cell to the cell membrane

18. Pathways affected by insulin 1. Carbohydrate metabolism stimulation of glucose utilization: glycogen synthase ↑ glycolysis ↑ inhibition of gluconeogenesis the transport of glucose into tissues (muscle, adipose tissue) 2. Lipid metabolism stimulation of the glucose conversion into FA: acetyl CoA carboxylase ↑ NADPH (PPP ↑) storage of fat: lipoprotein lipase ↑ inhibition of the degradation of fat: hormone sensitive lipase ↓

19. Pathways affected by insulin 1. Carbohydrate metabolism stimulation of glucose utilization: glycogen synthase ↑ glycolysis ↑ inhibition of gluconeogenesis the transport of glucose into tissues (muscle, adipose tissue) 2. Lipid metabolism stimulation of the glucose conversion into FA: acetyl CoA carboxylase ↑ NADPH (PPP ↑) storage of fat: lipoprotein lipase ↑ inhibition of the degradation of fat: hormone sensitive lipase ↓

20. Effects of insulin deficiency 1. Glucose uptake and utilization↓ 2. Proteolysis↑ 3. Gluconeogenesis ↑ 3. Degradation of fat ↑ Hyperglycemia (≥ 9mmol/l) Glucosuria Hyperlipidemia Metabolic acidosis Ketonuria

21. Type I (insulin-dependent)Type II (non-insulin- dependent) Incidence10-20%80-90% Agechildhood, the teensMiddle-aged, older CauseAn autoimmune disease Complete absence of insulin Unknown Relative insulin deficiency SymptomsHyperglycemia, hypertriglyceridemia, ketoacidosis Hyperglycemia, hypertriglyceridemia HabitusThinnessObesity KetoacidosisYesNo InsulinVery low or absentNormal (increased) TherapyInsulinDiet, drugs, insulin Types of diabetes:

22. The oral glucose tolerance test (oGTT): Used if:  elevated fasting levels of glucose - 5,3-6,7 mmol/l (for diagnosis of diabetes, screening of patients with impaired glucose tolerance)  screening of gestational diabetes Procedure:  administration of 75g glucose in an aqueous solution  after overnight fasting (10h)  „common“ diet and physical activity during previous three days  be seated and do not smoke during the test  determination of the glucose levels in the capillary blood before the glucose load and after 60 and 120 minutes Factors affecting oGTT: previous diet, infection, stress

23. The oral glucose tolerance test (oGTT): The blood glucose level returns to the basal level by 2 hours

24. 1. or diabetic symptoms (polyuria, polydipsia, weight loss) + plasmatic glucose level ≥ 11,1 mmol/l 2. or plasmatic glucose level after fasting ≥ 7 mmol/l 3. or plasmatic glucose level 2h after glucose intake (oGTT) ≥ 11,1 mmol/l 4. Glycated haemoglobin 38-47 mmol/mol (prediabetes) Glycated haemoglobin over 48 mmol/mol (diabetes)

25. Biological materialMetodaCause of interference Explanation of interference BloodAllDelayErythrocytes oxidize glucose BloodGlucose-oxidaseAcetaminophenIncrease measured values PlasmaSpectrophotometryHaemolysis or hyperlipidemia increases opacity Change in measurement linearity UrineAllBacteriuriaGlucose consumption UrineBenedict's testReducing factors (vit. C, saccharides, ↑urates, ↑creatinine) False positive UrineGlucose-oxidaseDetergents Vit. C, keton bodies False positive False negative

26. 1. over 45 years old, mainly in case BMI > 25kg/m 2 repeat every 3 years 2. younger overweight people (BMI > 25kg/m 2 ) with further risk factors:  physical inactivity  parents or siblings with diagnosed diabetes  previous diagnosis of IGT or IFG  syndrome of polycystic ovaria  hypertension or dyslipidemia  gestational diabetes or newborn > 4kg  vascular diseases

27. A. Microvascular (diabetic retinopathy, nefropathy, neuropathy)  nonenzymatic glycation of proteins in vascular tissue B. Macrovascular (atherosclerosis)  nonenzymatic glycation of proteins in vascular tissue and lipoproteins C. Diabetic cataract:  increased osmolarity of the lens (increased activity of the polyol pathway → ↑sorbitol)  nonenzymatic glycation of proteins of lens

28. Hyperglycemia - protein glycation:  hemoglobin  vascular tissue proteins → contribute to the diabetic complications (cataracta, atherosclerosis, retinopathy, nephropathy) Glycated proteins: - impaired structure and fucntion The importance of the maintance of low glucose levels in diabetic patients !

29. Diabetic cataract : ↑glucose concentration in the lens → ↑aldose reductase activity → sorbitol accumulation → ↑osmolarity, structural changes of proteins Lens metabolism:

33. Marks´ Basic Medical Biochemistry, A Clinical Approach, third edition, 2009 (M. Lieberman, A.D. Marks) Color Atlas of Biochemistry (J. Koolman, K.H. Roehm) Francois R. Jornayvaz1 and Gerald I. Shulman, Diacylglycerol Activation of Protein Kinase Cε and Hepatic Insulin Resistance, Cell Metabolism 15, 2012