8 carbohydrates

8/26/2014

1

CARBOHYDRATES

Contents

1. Introduction

2. Pathways of Glucose Metabolism

3. Regulation of Glucose Metabolism

4. Disease states in Glucose Metabolism Hyperglycemia

Hypoglycemia

5. Diagnosis of patients with Glucose Metabolic Alterations

Introduction

Primary energy source stored primarily glycogen (muscle and liver)

Disease states involved hyperglycemia and hypoglycemia

Contain C, H, and O (Cx (H20)y with C=O and –OH functional groups

Introduction

Carbohydrate Models

Introduction

Classification Definition

Monosaccharidesor simple sugars

Sugar that cannot be hydrolyzed to a simpler form Sugar that contain 3, 4, 5, 6 carbon atoms

(triose, tetroses, pentoses and hexoses, etc.) Examples include fructose, glucose, galactose

Disaccharides

Formed by interaction of two monosaccharides Examples

Maltose = glucose + glucoseLactose = glucose + galactoseSucrose = glucose + fructose

Polysaccharides Linkage of many monosaccharide units Include starch, glycogen and cellulose

Introduction


Monosaccharidesor simple sugars

Sugar that cannot be hydrolyzed to a simpler form Sugar that contain 3, 4, 5, 6 carbon atoms

(triose, tetroses, pentoses and hexoses, etc.) Examples include fructose, glucose, galactose

8/26/2014

2

Introduction


Disaccharides

Formed by interaction of two monosaccharides Examples

Maltose = glucose + glucoseLactose = glucose + galactoseSucrose = glucose + fructose

Introduction


Polysaccharides Linkage of many monosaccharide units Include starch, glycogen and cellulose

Starch

Cellulose

Glycogen

Contents

1. Introduction




Hypoglycemia


Glucose Metabolism

Glucose Metabolism Glucose Metabolism

1

GlycolysisMetabolism of glucose to lactate or pyruvate

for production of energy

Gluconeogenesis Formation of glucose-6-phosphate from non

carbohydrate source

Glycogenolysis Breakdown of glycogen to glucose for use as

energy

Glycogenesis Conversion of glucose to glycogen for storage

Lipogenesis Conversion of carbohydrates to fatty acids

Lipolysis Decomposition of fat

8/26/2014

3

Glucose Metabolism

1

Glycolysis(EMP Pathway)

Metabolism of glucose to lactate or pyruvate for production of energy Glucose –Insulin ATP + lactate/pyruvate

Glucose Metabolism

1

Gluconeogenesis

Formation of glucose-6-phosphate from non carbohydrate source Fats glucose + ketone bodies Protein glucose + urea nitrogen

Glucose Metabolism

1

Glycogenesis Conversion of glucose to glycogen for storage Glucose –Insulin Glycogen

Glucose Metabolism

1

Glycogenolysis Breakdown of glycogen to

glucose-6-phosphate Glycogen –Glucagon Glucose

Glucose Metabolism

1

Glycolysis(EMP Pathway)

Metabolism of glucose to lactate or pyruvate for production of energy Glucose –Insulin ATP + lactate/pyruvate

Gluconeogenesis

Formation of glucose-6-phosphate from non carbohydrate source Fats glucose + ketone bodies Protein glucose + urea nitrogen

Glycogenolysis Breakdown of glycogen to glucose for use as

energyGlycogen –Glucagon Glucose

Glycogenesis Conversion of glucose to glycogen for storage Glucose –Insulin Glycogen

Glucose Metabolism

1

Lipogenesis Conversion of carbohydrates to fatty acids

Lipolysis Decomposition of fat

8/26/2014

4

CONTENTS

1. Introduction




Hypoglycemia


Regulation of Glucose Metabolism

1. Insulin

2. Glucagon

3. Epinephrine

4. Cortisol

5. Growth hormone

6. Thyroxine

7. Somatostatin


Insulin (Hypoglycemic agent)

1. Primary hormone responsible for decreasing blood glucose2. Synthesized by the β cells of the islets of Langerhan (pancreas)3. Regulates blood glucose by ↑ glycogenesis, glycolysis and

lipogenesis; and ↓ glycogenolysis.


Glucagon (hyperglycemic agent)

1. Primary hormone responsible increasing blood glucose2. Synthesized by the α cells of the islets of Langerhan (pancreas)3. Regulates blood glucose by ↑ glycogenolysis and gluconeogenesis.


Epinephrine

1. Produced by the adrenal medulla, ↑ blood glucose2. Released during times of physical and emotional stress3. Inhibits insulin secretion, ↑ glycogenolysis and lipolysis


Cortisol (Glucocorticoids)

1. Produced by the adrenal cortex, in response to ACTH, ↑ plasma glucose

2. ↓ intestinal entry of glucose into the cell, ↑ gluconeogenesis, glycogenolysis and lipolysis

http://upload.wikimedia.org/wikipedia/commons/c/c6/Illu_endocrine_system.jpg

8/26/2014

5

Glucose Metabolism

Growth hormone

1. Produced by the anterior pituitary gland; ↑ plasma glucose2. ↓ glucose entry to cells, ↑ glycolysis

Glucose Metabolism

Thyroxine

1. Produced by the thyroid gland; ↑ plasma glucose2. ↑ glycogenolysis, gluconeogenesis and glucose intestinal absorption

Glucose Metabolism

Somastostatin

1. Produced by the Delta cells of the islet of Langerhans in the pancreasand hypothalamus

2. Increases plasma glucose by inhibition of insulin, glucagon, GH, etc.s


1. Insulin2. Glucagon3. Epinephrine4. Cortisol5. Growth hormone6. Thyroxine7. Somatostatin

CONTENTS

1. Introduction



4. Disease states in Glucose Metabolismi. Hyperglycemia

ii. Hypoglycemia


Hyperglycemia

Increase in plasma glucose

Insulin is secreted in the β cells of pancreatic islets

Increase in Plasma Glucose




8/26/2014

6

Hyperglycemia

Diabetes mellitus

Metabolic disease characterized by hyperglycemia resulting from defects in insulin secretion, insulin action or both

Diabetes Mellitus Classification

1. Type 1 (IDDM)

2. Type 2 (NIDDM)

3. Other

4. Gestational

Hyperglycemia


Epidemiology and Pathophysiology

Type 1 10-20% of all cases of diabetes

Occurs in childhood and adolescence

Absence of Insulin with excess in glucagon

Hyperglycemia


Pathogenesis

Type 1 β-Cell destruction

Absolute insulin deficiency

Autoantibodies• Islet cell autoantibodies• Insulin autoantibodies• Glutamic acid decarboxylase autoantibodies• Tyrosine phosphatase IA-2 & IA-2B autoabs.

Hyperglycemia


Characteristics

Type 1 Abrupt onset

Insulin dependence

Ketosis tendency

Sign and Symptoms• Polydipsia (excessive thirst)• Polyphagia (↑ food intake)• Polyuria (excessive urine production)•Rapid weight loss•Hyperventilation•Confusion and possible loss of consciousness

Hyperglycemia


Epidemiology

Type 2 90% of all cases of diabetes

Adult onset

Hyperglycemia


Pathogenesis and Pathophysiology

Type 2 Insulin resistance w/ insulin secretory defect

Relative insulin deficiency

Inc. with age , obesity and lack of exercise

Insulin is present (hyperinsulinemia)

Glucagon secretion is attenuated

8/26/2014

7

Hyperglycemia


Characteristics

Type 2 Non Insulin dependendent

Ketosis tendency is seldom with greatertendency to develop hyperosmolar nonketonic states (1,000 mg/dL of glucose: >320mOsm/dL)

Milder symptoms than type 1• Polydipsia (excessive thirst)• Polyphagia (↑ food intake)• Polyuria (excessive urine production)

Hyperglycemia


Pathogenesis

Others Associated with secondary conditions

• Genetic defects of β-cell function• Pancreatic disease• Endocrine disease• Drug or chemical induced• Insulin receptor abnormalities• Other genetic syndromes

Hyperglycemia

Laboratory Findings

↑ glucose in plasma and urine

↑ urine specific gravity

↑ serum and urine osmolality

Ketones in serum and urine (ketonemia and ketonuria) acetoacetate, β-hydroxybutyrate & acetoin is produced from FA

↓ blood and urine pH (acidosis)

Electrolyte imbalance ↓ Na – polyuria and shift of water from cells, ↑ K – displacement from cells in acidosis

Hyperglycemia

Disease

Microvascular problems

• Nephropathy

• Retinopathy

• Neuropathy

• Increased heart disease

Hyperglycemia


Pathogenesis

Gestational Glucose intolerance during pregnancy

Due to metabolic and hormonal changes

↑ risk for respiratory distress syndrome, hypocalcemia and hyperbilirubinemia

Pathophysiology

Glucosuria: exceed 180 mg/dL

Type 1: ketosis prone

Due to difference in glucagon and insulin concentrations (increased β oxidation)

Type 2: fatty acid oxidation is inhibited VLDL

Non ketotic hyperosmolar state

Overproduction of glucose, imbalance between production and elimination in urine

Gross elevation of glucose( up to 1,000mg/dL)

8/26/2014

8

Hyperglycemia

Diagnostic Criteria for Diabetes Mellitus

1. Random plasma glucose ≥200mg/dL, + symptoms of diabetes

2. Fasting plasma glucose ≥126 mg/dL

3. 2-h plasma glucose ≥200 mg/dL during an OGTT4. HBA1C ≥6.5%

Categories of Fasting Plasma Glucose (FPG)

Normal fasting glucose FBG 70-99 mg/dL

Impaired fasting glucose FBG 100-125 mg/dL

Provisional diabetes diagnosis FPG ≥126 mg/dL

Hyperglycemia

Categories of Oral Glucose Tolerance

Normal Glucose Tolerance 2-h PG ≤140 mg/dL

Impaired Glucose Tolerance 2-h PG 140-199 mg/dL

Provisional diabetes diagnosis 2-h PG ≥200 mg/dL

ADA criteria:45 years aboveTested every 3 years for HBA1C and FBGInititaed earlier if overweightType 2 testing for children:10 years or onset of pubertyFollow up testing every 2 yearsPage 301

Hyperglycemia

Diagnostic Criteria for Gestational Diabetes Mellitus

Fasting plasma glucose ≥92mg/dL

1. 1-h plasma glucose ≥180 mg/dL during an OGTT + symptoms of gestational diabetes (100 grams glucose load)

2. 3-h plasma glucose: Fasting (8-14 hrs) – >95 mg/dL; 1 hr – ≥180 mg/dL; 2 hrs – ≥153 mg/dL ; 3 hrs – ≥140 mgdL)

CONTENTS

1. Introduction




ii. Hypoglycemia


Causes of Hypoglycemia

Patients Appears Healthy

No coexistingdisease

Drugs

Insulinoma, Islet hyperplasia/nesidioblastosis

Factitial hypoglycemia from insulin/sulfonylurea

Severe exercise, Ketotic hypoglycemia

Compensated coexistent

Drugs/disease

Patients Appears Ill

Drugs

Predisposing illness

Hospitalized patient

Hypoglycemia

Laboratory Findings

↓ glucose in plasma

↑↑↑ in patients with pancreatic β-cell tumors (insulinoma)

Epinephrine

Cortisol

Growth Hormone


8/26/2014

9

Hypoglycemia

Genetic Defects in Carbohydrate Metabolism

Von Gierke Disease (glucose-6-phosphatase deficiency type 1)

Glycogen build up in the liverdue to inhibition of hepatic glycogenolysis

Galactosemia(galactose-1-phosphate uridyltransferase dificiency)

Inhibition of glycogenolysis

CONTENTS

1. Introduction




ii. Hypoglycemia


Diagnosis of Glucose Metabolic Alterations

Methods:

1. Fasting Blood Glucose

2. POC

3. 2-Hr Post Prandial Sugar

4. OGTT

5. HbA1C

6. Ketone

7. Microalbuminuria


Considerations:

1. WB glucose concentration 11% lower than plasma

2. Serum or plasma must be refrigerated and separated from the cells within 1 hr

3. Sodium flouride (gray-top) can be used to inhibit glycolyticenzymes

4. FBG should be obtained in the morning after 8 to 10 hours fasting(not longer than 16 hours)


Non Enzymatic Methods of Glucose Measurement

1. Nelson Somogyi

Copper reduction method (uses BaSO4 to remove saccharoids)

Glucose + arsenomolybdic acid arsenomolybdenum blue

2. Hagedorn Jensen

Ferric reduction method (inverse colorimetry)

Glucose + Ferricyanide (yellow) Ferrocyanide (colorless)

3. Ortho-toluidine (Dubowski)

Condensation of carbohydrates with aromatic amines producing Schiff bases (green)


Enzymatic Methods of Glucose Measurement

1. Glucose oxidase (Saifer Gernstenfield)

2. Hexokinase (reference method)

3. Clinitest

8/26/2014

10




Β-D-glucose + O2 +H2O –glucose oxidase gluconic acid + H2O2

H2O2 + reduce chromogen –peroxidase oxidized chromogen + H2O

Couple reaction is known as Trinder’s reaction False Law results due to ↑ uric acid, bilirubin and ascorbic acid

O2 Consumption electrode (polarographic glucose analyzers) can also measure oxygen depletion




Glucose + ATP –hexokinase glucose 6-PO4 + ADP

Glucose 6-PO4 + NADP+ –G-6-PD NADPH + H+ + 6-phosphogluconate

↑ in absorbance is measured at 340 nm

False low results due to gross hemolysis and ↑↑↑ bilirubin




Glucose + ATP –hexokinase glucose 6-PO4 + ADP

Glucose 6-PO4 + NADP+ –G-6-PD NADPH + H+ + 6-phosphogluconate

3. Clinitest

Reducing substance + Cu+2 Cu+1O





3. Clinitest


Self-Monitoring of Blood Glucose

1. Type 1 diabetes – 3 to 4 times/day


2-Hour Postprandial Tests

A solution containing 75 g (adults) or 1.75 g/kg (children) of glucose is administered, and a specimen is drawn 2 hrs later

Oral Glucose Tolerance Test

The patients fasting blood glucose is takenGlucose load is administeredBlood glucose is determined in 30 min, 1st , 2nd and 3rd hr.

8/26/2014

11

HbA1C Measurement

Index for long term plasma glucose control (2-3 month period), indicating compliance and efficacy of DM therapy.

Formed by the attachment of glucose to Hb to form a ketoamine.

Specimen requirement is EDTA WB sample. N.V 4.0 to 6.0%


Methods of HbA1C Measurement

• Based on charged differences between glycosylated and nonglycosylated hemoglobin

• Structural characteristics of glycogroups on hemoglobin


Methods of HbA1C Measurement based on structural differences

ImmunoassaysPolyclonal or monoclonal antibodies toward the glycated N-terminal group of the β chain of Hb

Affinity Chromatography

Separated based on chemical structure using boronate group to bind glycosylated proteins


Methods of HbA1C Measurement based on charge differences

Cation-exchangeChromatography

Positive-charge resin bed attaches to negatively charged hemoglobin

Electrophoresis Separation is based on differences in charge

Isoelectricfocusing

Type of electrophoresis using isoelectric point to separate

HPLCA form of ion-exchange chromatographySeparates all forms of HbA1C (A1a, A1b, A1c)


Ketone

Produced by the liver through metabolism of stored lipids

3 ketone bodies• Acetone (2%)• Acetoacetic acid(20%)• 3-β-hydroxybutyric acid (78%)

Ketonemiaaccumulation of ketones in blood

Ketonuriaaccumulation of ketones in urine


Mtds. of Ketone Measurement

Gerhardt’s Test

Acetoacetic acid + Ferric chloride Red color

Nitroprusside

Acetoacetic acid + nitroprusside–alkaline pH Purple color

Enzymatic

NADH + H+ + acetoacetic acid β-HBD NAD + β-hydroxybutyricacid


8/26/2014

12

Microalbuminuria

Diagnosis at an early stage diabetic renal nephropathy and before the development of proteinuria

Persistent albuminuria in the range of 30-299 mg/24 h or albumin creatinine ratio of 30 to 300 µg/mg

Diagnosis of Glucose Metabolic Alterations CONTENTS

1. Introduction




ii. Hypoglycemia


8 carbohydrates

Documents