Glucose Metabolism

CARBOHYDRATE MOLECULES ARE COMPOSED

C, H, AND O IN THE RATIO OF 1:2:1

If a carbohydrate consists of just one sugar molecule

It is a monosaccharide(Glucose)

Two linked monosaccharide form a

Disaccharide

A polymer of many monosaccharides is a

Polysaccharide

GLUCOSE(C6H12O6)

THE MOST COMMON MONOSACCHARIDE IN LIVING ORGANISMS

POLYSACCHARIDES

CHAINS OF SIMPLE SUGARS

Both Starch and Glycogen are polymers of glucose molecules

Starch

An energy storage molecule in plants, formed in roots and seeds

Glycogen

An energy storage molecule in animals, found in the liver and muscles

GLYCOPROTEINS

Conjugated proteins with oligosaccharide attached

Membrane proteins, antibodies, hormones, coagulation factors, and hemoglobin

Number of carbohydrate residues can be from 1-70% of the weight of the total glycoprotein

Glucose

The primary circulating sugar in the blood and the major energy source of the body – used to produce ATP

Gluconeogenesis

The formation of new glucose from non-carbohydrate sources (protein or fat) to store energy

In prolonged starvation

Glycolysis

The breakdown of glucose (to produce energy)

Cells require energy

Glycogen(body)

The main form of carbohydrate storage primarily in the liver and muscle tissue; readily converted to glucose to satisfy its energy needs – facilitated by hormone
glucagon

Glycogenesis

Formation/synthesis of glycogen from glucose (to store energy) – facilitated by action of insulin

Glycogenolysis

Breakdown of glycogen to glucose (to produce energy)

When plasma(serum) glucose falls

GLYCOLYSIS

GLU-6-PHOSPHATE A CENTRAL INTERMEDIATE GLUCOSE-6-PHOSPHATASE IS NECESSARY ENZYME

Glu=Glu-6-P=2 Pyruvate=2 Lactate

GLYCOGENOLYSIS

BREAKDOWN OF GLYCOGEN AND FORMATION OF GLU-6-PFORMATION OF GLU-6

Glycogen(In muscle/liver)=Glu-1-P=Glu-6-P

Controlled by glucagon( When low blood sugar) and epinephrine (Flight or fight)

GLYCOGENESIS

GLYCOGEN SYNTHESIS FROMSYNTHESIS FROM GLUCOSE

When glucose intake exceeds immediate needs

Facilitated by insulin and high blood glucose levels

Enzyme responsible is hexokinase (In Liver)

GLUCONEOGENESIS

THE PROCESS OF FORMING NEW GLUCOSE FROM NON-CARBOHYDRATE MOLECULES

AMINO ACIDS
•GLYCEROL(FROM FATS)

PROTECTS THE BODY, ESPECIALLY THE BRAIN, FROM THE DAMAGING EFFECTS OF HYPOGLYCEMIA BY ENSURING ATP SYNTHESIS CAN CONTINUE

Decrease blood glucose

Insulin

Increase blood glucose

Glucagon
Epinephrine
Cortisol
Growth Hormone
ACTH
Thyroxine

Somatostatin inhibit secretion

Of BOTH insulin and glucagon and different times. Indirect effect on blood glucose levels.

INSULIN

Body’s hypoglycemic agent

Secreted by the beta cell of islets of Langerhans in pancreas

Promote cellular uptake of glucose

Suppresses hepatic glucose production

Target organs: Liver, skeletal muscle, and adipose tissue

Insulin secretion is stimulated by

Glucose, amino acids, pancreatic and GI hormones and some medications.

Are the main signals in a feedback loop

Glucose and Insulin

ADVERSE EFFECTS OF INSULININSULI

HYPOGLYCEMIA UNAWARENESS

LIPODYSTROPHY

DAWN PHENOMENA—Poor blood glucose management at nights leads to waking up feeling sick and hypoglycemic

SOMOGYI EFFECT

COUNTER-REGULATORY HORMONES

OPPOSE ACTION OF INSULIN BY RAISING GLUCOSE LEVELS

GLUCAGON

Secreted by alpha cells of pancreas

Stimulates production of glucose in the liver

Secretion regulated by plasma glucose concertation

Stress, exercise and amino acids induce glucagon exercise

Insulin inhibits glucagon release and biosynthesis

EPINEPHRINE

Stimulates glycogenolysis

Inhibits: glucose movement into tissue & insulin secretion

Key role in glucose counter-regulation when glucagon secretion is impaired (in Type 1diabetes).

Physical or emotional stress increases secretion

GROWTH HORMONE

Produced by anterior pituitary gland

Stimulates gluconeogenesis

Enhances lipolysis (Breakdown of fats)

Opposes insulin stimulated glucose uptake

CORTISOL

SECRETED BY THE ADRENAL CORTEX IN RESPONSE TO ACTH

STIMULATES GLYCOGENOLYSIS AND GLUCONEOGENESIS

HYPOGLYCEMIA

Low blood sugar

Serum (Plasma) glucose level

Falls below 50 mg/dL

Glucagon is released when

Plasma glucose is < 70 mg / dL to inhibit insulin

Epinephrine, cortisol, and growth hormone

Released from adrenal gland to increase glucose metabolism and inhibit insulin

Age of onset of hypoglycemia

Is a convenient way to classify the disorder

Whipple’s Triad

Symptoms of hypoglycemia

Low plasma glucose at time of symptoms

Alleviation of symptoms with glucose
ingestion

HYPOGLYCEMIA IN NEWBORNS/ INFANTS

BLOOD GLUCOSE CONCENTRATION MUCH LOWER THAN ADULTS (35 MG/ML AVERAGE)

OFTEN IF MOTHER HAS DIABETES (ANY TYPE) THE INFANT IS BORN WITH
HYPOGLYCEMIA

FASTING HYPOGLYCHYPOGLYCEMIA IN ADULTS

Decreases rate of glucose production OR increased rate of glucose metabolism.

Symptoms usually arise around 55mg/mL (plasma glucose)

Brain function starts to go at less than 50mg/mL

72 hour fast often done to diagnose

HYPOGLYCEMIA AND DIABETES

Occurs very frequently in diabetic patients(Both type 1 and type 2)

Often occurs 1-2 times per week in type 1 diabetic patients

Counter Regulatory Mechanisms become impaired in diabetics (Glucagon and epinephrine secretion)

Often unaware of the condition until severe symptoms arise

GLYCOGEN STORAGE DISEASES

Enzyme deficiencies affecting glycogen storage

Most common and severe: von Gierke’s disease----Deficient in Glucose-6-phosphatase

Glycogen accumulates in liver(can’t be converted to glucose)

Liver transplant needed

GALACTOSEMIA

Galactose-1, Phosphate Uridyl-Transferase deficiency

Enzyme that converts galactose to glucose, patients can not change either galactose or lactose into glucose

Hypoglycemia an issue (Special needs)

LACTASE DEFICIENCY

GI deficient in lactase

Sensitive to dairy(Lactose Intolerant)

Most people self diagnose

Actual Diagnosis of Lactase Deficiency

Give Lactose and measure breath hydrogen levels ( Will see increase in hydrogen if intolerant).

Insulin release is inhibited by

Hypoglycemia, somatostatin (which inhibits growth hormone), and various drugs