CARBOHYRATES IN CLINICAL BIOCHEMISTRY

1. CARBOHYRATES IN CLINICAL BIOCHEMISTRY Prof. Dr. Serdar Öztezcan

2. Regulation of bloodglucoseconcentration • The concentration of glucose in the blood is regulated by a complex interplay of multiple pathways • Glycogenesis • Glycogenolysis • Glyconeogenesis

3. Hormones • The concentration of glucose in the blood is normally maintained within a narrow interval by hormones : • Insulin • Counterregulatory hormones • Glucagon • Epinephrine • Cortisol • Growth hormone

4. Insulin • Anabolic hormone • stimulates the uptake of glucose into fat and muscle • promotes the conversion of glucose to glycogen or fat for storage • inhibits glucose production by the liver • stimulates protein synthesis and inhibits protein breakdown • uptake ions (specially K+ and PO4-3) • The major insulin target organs are the liver, skeletal muscle andadipose tissue

5. Insulin

6. Counterregulatory Hormones • These hormones are catabolic • increase hepatic glucose production • initially by enhancing the breakdown of glycogen to glucose (glycogenolysis) • later by stimulating the synthesis of glucose (glyconeogenesis)

9. Diabetes Mellitus • Dm is actually a group of metabolic diseases characterized by hyperglycemia resulting from defects in insulinsecretion, insulinaction,orboth • Clasification and diagnostic scheme for diabetes mellitus (ADA/WHO) • Type 1 diabetes • Type 2 diabetes • Other specific types of diabetes • Gestational diabetes mellitus • Impaired Fasting Glucose • Impaired Glucose Tolerance

10. Type 1 diabetes • Formerly known as IDDM or juvenile-onset diabetes • Approximatelly 5-10% of all individuals with diabetes mellitus are in this category • Symptoms (eg. Polyuria, polydipsia, and rapid weight loss) usually present acutely • Patients has insulinopenia because of loss of pancreatic islet b cells • Depend on insulin treatment to sustain life and prevent ketosis • Most individuals have antibodies that identify an autoimmun prosess

11. Type 2 diabetes • Formerly known as NIDDM • This type consititues approx. 90% of all cases Patients have minimal symptoms and are not prone to ketosis • Insulin concentration may be within the reference interval, decreased, or increased • Most people with this form of diabetes have impaired insulin action • Obesity is commonly associated, and weight loss alone usually improves the hyperglycemia • Many individuals may require dietary manipulation, an oral hypoglycemic agent, or insulin terapy

12. Other specific types of diabetes • This subclass is associated with certain conditions such as • Genetic defects of b-cell function • Genetic defects in insulin action • Disease of exocrine pancreas • Endocrinopathies (e.g., Cushing disease, acromegaly, glucagonoma) • The administration of hormones and drugs known to induce b-cell dysfunction (e.g., dilantine and pentamidine) or impair insulin action (e.g., glucocorticoides, thiazides, and b-adrenergics) • Infections • The characteristics and prognosis of this form of diabetes depends on the primary disorder

13. Gestational diabetes mellitus • GDM is “any degree of carbohyrates intolerance with onset or first recognation during pregnancy” • Patient with GDM frequently return to normal postpartum • However GDM is associated with increased perinatal complications and an increase risk for development of diabets (predominantly Type 2) in later years

14. Impaired Fasting Glucose and Impaired Glucose Tolerance • Impaired fasting glucose • is diagnosed in people who have a fasting glucose value above normal but below the concentration for diagnosis of diabetes • It is a metabolic stage between normal glucose homeostasis and diabetes

15. Impaired Fasting Glucose and Impaired Glucose Tolerance • Impaired glucose tolerance • OGTT is required to assign a patient to this class • have plasma glucose response between normal and diabetic states during the OGTT • Development of overt diabetes occurs at a rate 1-5% per year in people with IGT

16. Complications of DM • Diabetic ketoacidosis • arises from a number of metabolic problems caused by insulin lack • Hyperosmolar non-ketotic coma (HONK) • occurs mostly in elderly, tip 2 diabetics • level of insulin is sufficient to prevent ketosis but does not prevent hyperglycemia and osmotic diuresis

17. Late complications of DM • DM is not only characterized by the presence of hyperglycaemia but also by the occurrence of late complications • Microangiopathy • Retionopathy • Nephropathy • Neuropathy • Macroangiopathy • Ateroscleorosis

18. Diagnosis of diabetes mellitus • Diagnosis depends solely on the demonstration of hyperglycemia • Diagnosis of type 1 is usually easy because • hyperglycemia appears abruptly, severe, accompained by serious metabolic problems • Diagnosis of type 2 may be difficult because • the metabolic changes are often not severe enough for the patient to notice symptoms • Complications are present in approximately 30% of patients at clinical diagnosis of type 2 diabets

19. Diagnosis of diabetes mellitus • All adults older than age 45 years should have a measurement of fasting blood glucose every 3 years • Earlier age or more frequently in individuals who display; • Obesity (BMI of 27 kg/m2) • Family history of diabetes in a first-degree relative • History of GDM or delivering a baby > 4.1 kg • Hypertension (> 140/90 mm Hg) • Low HDL concentration (< 35mg/dL) • Elevated triglyceride concentrations (> 250 mg/dL) • A history of IGF or OGT

20. Criteria for the diagnosis of diabetes mellitus • Any one of the following methods is diagnostic; • Classic symptoms of diabetes + causal/random plasma glucose concentration > 200 mg/dL • Fasting plasma glucose > 126 mg/dL • Two-hour plasma glucose > 200 mg/dL during the OGTT * If, any three criteria is positive, it must be confirmed on a subsequent day by any of the three methods

21. Criteria for the diagnosis of diabetes mellitus • Intermediate group • Impaired Fasting Glucose • Fasting plasma glucose between 100 (106) and 125 mg/dL. • Impaired Glucose Tolerance • Fasting plasma glucose < 126 mg/dL • Two-hour OGTT plasma glucose concentration is between 140 and 199 mg/dL

22. Oral glucose tolerance test (OGTT) • In OGTT plasma glucose concentrations are measured fasting, then every 30 minutes for 2 hours after an oral glucose load • Although more sensitive than FPG determinations, OGTT is affected by a large number of factors that result in poor reproducibility

23. Oral glucose tolerance test (OGTT) • The following conditions should be met for performing an OGTT; • discontinue, when possible, medications known to affect it (thiazides, oc, corticosteroids) • in the morning after 3 days of unrestricted diet (150 g ch/day) and activity • after a 10-14 hour fast • seated during the test without smoking cigarettes and drinking coffee ect. • For nonpregnant adults 75 g, • for children 1.75 g/kg (max 75g ), • dissolved in 300 ml water / 5 minutes

24. Diagnosis of GDM • ADA recommentation for laboratory diagnosis of GDM are • Low-risk patients require no testing • Average-risk patients should be testing at 24 to 28 weeks of gestation • High-risk patients should undergo immediate testing

25. Diagnosis of GDM • Risk factors for GDM include, • Family history of DM in a first-degree relative • Obesity • Advanced maternal age • Glycosuria • History of poor obstetric outcome (stillbirth or macrosomia) • Member of an ethnic group with a high prevalence of GDM

26. Diagnosis of GDM • First step is identical to that for diagnose diabetes in a nonpregnant individual (Fasting >126 or random >200) • However, in the absence of that degree of hyperglycemia, average and high risk patients receive a glucose tolerance test following one of two methods; • One step test • Two step test

27. Diagnosis of GDM • One step test ; perform a 100 g OGTT for 3 hour (or 75 g for 2 hour - it is not as well validated as the 100 g test) • Two step test ; the first step is a 50 g oral glucose load (the patient does not need to be fasting) followed by a plasma glucose determination at 1 hour • A value grater than or equal to 140 mg /dL (or 130) indicates the necessity for definive testing (one step test) • 90%-130, 80% 140

28. Diagnosis of GDM • To diagnose GDM with 100 g test at least two values must meet or exceed the following, • Fasting 95mg/dL • 1 hr 180mg/dL • 2 hr 155mg/dL • 3 hr 140mg/dL

29. Gestational diabetes mellitus • At 6 to 12 weeks postpartum, all patients who had GMD should be evaluated for diabetes • if not present, be reevaluated for diabetes at least every 3 years

30. Infants born to mothers with diabetes • Infants born to mothers with diabetes are increased risk for respiratuary distress syndrome, hypocalcemia and, hyperbilirubinemia • Fetal insulin secretion is stimulated in the neonate of mother with diabetes. When the infant is born and the umblical cord is severed, the infant’s oversupply of glucose is abruptly terminated, causing severe hypoglycemia

31. Hypoglycemia • Hypoglycemia involves decreased plasma glucose levels and can have many causes • Some are transient and relatively insignificant • Others can be life threating • Glucagon and other glycemic factors are released is between65-70 mg/dL • Symptoms of hypoglycemia appear at about 50-55 mg/dL

32. Hypoglycemia • Hypoglycemia was classified as • postabsorbative (fasting) • postprandial (reactive) • Current approaches suggest classification based on clinical characteristics. This classification separates patients into those who appearhealthyorsick

33. Hypoglycemia • Symptoms of hypoglycemia may be categorized as neurogenic (adrenergic) or neuroglycopenic • Neurogenic symptoms include sweating, shakiness, tachycardia, and anxiety • Neuroglycopenicsymptoms include weakness, tiredness, or dizziness; difficulty with concentration; confusion; blurred vision; and, in extreme cases, coma and death

34. Hypoglycemia • Some of causes of hypoglycemia • Drugs (insulin, oral ) and ethanol • Insulinoma • Severe exercise • Glucogen storage diseases: • Glucose 6-phospathase deficiency tip 1 (von Gierke) • Neonatal hypoglycemia • Galactosemia • Hormonal deficiencies - cortisol, growth hormone (in children), glucagon, and epinephrine • Critical illnesses - cardiac, hepatic, and renal diseases, sepsis • Congenital - carnitine deficiency

35. Role of laboratory • Glucose measurement • Serum or plasma glucose concentration • Self-monitoring of whole blood glucose concentrations (capillary) • Urine ( Treshold 170-180 mg/dL ) • Glucose tolerance tests • Glycosylated hemoglobine • Ketones • Microalbuminuria • Islet autoantibody • Insulin

36. Glycosylated hemoglobine • Long term blood glucose regulation can be followed by measurement of glycosylated hemoglobine • Formation of a hemoglobin compound when glucose reacts with the amino group of hemoglobin • The rate of formation is directly proportional to the plasma glucose concentrations • Reflects the avarage blood glucose level over the previous 2-3 months • Hemoglobin A1c the most common • Reference values 4,5 to 6% (> 6,5 diagnose ?) • %1 --- 35mg/dL

37. Fructosamine • Refers to the ketoamin linkage between glucose and protein • Since all serum protein can be glycated and albumin is the most abundant protein in serum, measurement of fructosamin is largely a measurement of albumin • Measure of glycemic control during the 3-week period before sampling, since the half-life of albumin is 2 to 3 weeks

38. Ketones • Ketone bodies are produced by the liver through metabolism of fatty acid to provide a ready energy source from stored lipids at times of low carbohyrate availability such as • diabetes mellitus, starvation/fasting, high-fat diets, prolonged vomiting, and glycogen storage disease • The three ketone bodies are • aceton (2%), • acetoacetic acid (20%), • b-hidroxybutyric acid (78%) • Recommended for patients with type 1 diabetes during • acute illness, stress, pregnancy, eleveted blood glucose above 300 mg/dL or when patient has sings of ketoacidosis

39. Microalbuminuria • Diabetes mellitus causes progressive changes to the kidneys and ultimately results in diabetic nephropathy • This complication progesses over years and may be delayed by aggresive glycemic control • An early sign is an increase in urinary albumine • Microalbumin measurements are useful to assist in diagnosis at an early stage andbefore the development of proteinuria • Microalbumin 30-300 mg/day (reference interval <30 mg/day) • Proteinuria; greater than 0,3/0,5 g/day

40. Islet autoantibody and insulin • Islet autoantibody • The presence of autoantibodies to the b cells of the pancreas is charactheristic of type 1 • Testing is not currently recommended for rutine screening for diabetes diagnosis • In the future, it might identify at-risk, prediabetik patients • Insulin • Not required for the diagnosis of diabetes mellitus • Insulin resistance • However, ın certain hypoglycemic states, it is important to know the concentration of insulin in relation to the plasma glucose concentration -insulinoma

41. HOMA-IR • The homeostatic model assessment (HOMA) is a method used to quantify insulin resistance and beta-cell function • It was first described under the name HOMA by Matthews et al. in 1985 • Glucose X Insulin X 0,055 : <2.3 22.5

42. Case study • Fasting glucose 95 • Fasting glucose 135 • Fasting glucose 115 • Random glucose 202 • OGTT 2 hour 145 • OGTT 2 hour 207 • Serial measurement • 1. quarter HbA1c 7.8% FPG 280 • 2. quarter HbA1c 15.3% FPG 85 • 3. quarter HbA1c 8.5% FPG 91 • Two test • Self monitoring 200 • In the laboratory with serum