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Flashcards in Quiz 1: Glucose Deck (19)
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Methods of glucose metabolism regulation

1. Store glucose as a reservoir (glycogen) in Liver
Moved to cells via Insulin
2. Mobilize the stored glucose to maintain the blood glucose levels
Moved back to blood by hormones: glucagon, epinephrine, cortisol, Thyroxine, growth hormone


Reactions For Determining Glucose

• Oxidation: glucose oxidase
• Phosphorylation:
hexokinase catalysis of ATP + glucose to ADP + G-6-P
• Oxidation reduction methods: copper reduction, ferricyanide
• Schiff’s Base formation with amines, glucose + Hgb to HgbA1C



• Hyperinsulinism: too much insulin, with an excessive amount of glucose is removed
May occur when a diabetic injects too much insulin:
Insulin shock may result in coma, glucose does not reach the brain
• Over stimulation of insulin: after heavily sugared food. Initial high glucose leves over-stimulates the pancreas, causing blood sugar levels to drop below normal after 2-3 hours.
• A Quick fix: (eating more sugar) causes more insulin production, Protein corrects by allowing glucose to enter bloodstream slowly


Glucose Tolerance Testing

Establishes when glucose reaches the highest concentration and how rapidly it returns to normal levels.
• Patient is given specific amount of glucose (100g)
• Blood samples drawn at specific intervals: Fasting or Hourly intervals
• Detection of glucose in urine, (glycosuria)
Normal: doesn't exceed 200 mg/dL, returns to 120 mg/dL after 2 hours
D. mellitus: peaks above 200 mg/dL, does not return to 120 mg/dL after 2 hours


Function of Insulin

Increases the rate of glycolysis, glyogenesis, lipogenesis and synthesis of protein
Decreases rate of glycogenolysis and gluconeogensis
Lack of Insulin causes the opposite effect



• If carbohydrate metabolism is severely limited, the cell begins to oxidize fat reserves for energy.
- Proteins are degraded to amino acids leading to glucose
- Cells begin to oxidize fat reserves for energy, causes excess of AcetylCoA, which leads to excess ketone bodies, acidosis and can cause coma and death


Glycosated Hgb Detection

• Glycosylated Hgb is formed when glucose reacts with the amino group of Hgb.
• The rate of formation is directly porportional to the plasma glucose concentration.
• Reflects the average blood glucose over the previous 2 to 3 months.


Glycosated Hgb A1C Detection

• A minor component of Hgb to which glucose is bound
• Levels of Hgb A1C depend on blood glucose concentration
- The higher glucose = higher level of A1C
- Does not fluctuate with daily blood glucose levels
- Reflects an average glucose level over a 6 to 8 week period, can be used to diagnose Diabetes
Useful as indicator of how glucose level is controlled by drugs, diet, exercise with the normal range =


Glycosated Hgb A1C Range

Normally <7%
HbA1c may be increased falsely in certain medical conditions: uremia (kidney failure), chronic excessive alcohol intake, and hypertriglyceridemia.
Falsely decrease HbA1c include acute or chronic blood loss, sickle cell disease or thalassemia.
Diabetes during pregnancy, commonly referred to as gestational diabetes, may falsely increase or decrease HbA1c.


CSF Glucose Testing

• Normal CSF glucose = 60-80% of blood glucose level
- 450-800 mg/L (Kaplan pg 791), 40-70 mg/dL (Tietz 2006)
• Abnormal CSF glucose = (once equilibrated over 4 hrs) less than 40% of the blood glucose
• Distinguishes bacterial from viral meningitis
- Bacterial: glucose low, less than 40% of serum glucose
- Viral: glucose generally normal


Most Commonly Preformed Glucose Tests

• Creatinine clearance vs glomerular filtration rate
• Urine osmolality for tubular concentration ability
• Urine protein electrophoresis: glomerular permeability and detection of Bence Jones Protein
• Serum creatinine and blood urea nitrogen (BUN) constant predictors of renal function


Glucose's Purpose in Body

Digestion, Metabolism, Regulation
End product of carbohydrate digestion in Intestine
Blood Glucose is maintained at a constant level by hormones (Insulin increases, all others decrease)


Fasting Blood Glucose Reference Ranges

Reference Range for Serum/Plasma: 70-99mg/dL
Arterial and Capillary values are 2-3 mg/dL higher


Hormones affecting Blood Glucose Levels

Insulin (increases) - produced by Beta cells in the pancreatic islets of Langerhans, promotes storage of glucose in Liver/Muscle/Adipose
Glucagon (Alpha cells of Pancreatic Islets of Langerhans, glycogenolysis and gluconeogenesis)
ACTH/Growth Hormone (secreted by anterior pituitary to raise blood glucose)
Cortisol (From Adrenal glands, stimulates glycogeno/lipolysis and gluconeogenesis)
Human Placental Lactogen
Epinephrine (medulla of adrenal glands, glycogeno/lipolysis and inhibits insulin secretion)
T3/T4 (Increases Glucose uptake in GI, glycogenolysis and gluconeogenesis)


Diabetes Mellitus Diagnosis

Fasting Plasma Glucose > 126 mg/dL, Random Glucose > 200 mg/dL, 2 hr Peak Glucose > 200mg/dL, A1c > 6.5%


Diabetes Monitoring Tests

Glycosylated Hgb, HbA1c
Urinary Microalbumin
C Peptide


Urinary Microalbumin

Detects small amounts of albumin in urine to detect early renal damage


C Peptide

Proinsulin is cleaved to produce C Peptide and Insulin
Shows level of endogenous Insulin production is patient is taking Insulin



After 24-48 hours of fasting, glycogen stores are used up so Gluconeogenesis occurs