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MELS301 > Glucose > Flashcards

Glucose Flashcards

1
Q

What is glucose used for?

A

Energy for many different tissues in the body including brain, eyes, RBC, kidneys and endothelium.

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2
Q

How is glucose stored?

A

Glycogen in skeletal muscle and liver or triglyceride in adipose tissue.

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3
Q

What is glycogenesis?

A

Glucose to glycogen

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4
Q

What is glycolysis?

A

Glucose to lactate/pyruvate

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5
Q

What is glyocogenolysis?

A

Glycogen to glucose

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6
Q

What is gluconeogenesis?

A

Amino acids, glycerol or lactate to glucose.

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7
Q

How does insulin decrease blood glucose levels?

A

By facilitating cellular uptake of glucose, stimulating glycolysis and glycogenesis and inhibiting gluconeogenesis. Also stimulates lipogenesis, protein synthesis and inhibits lipolysis and ketogenesis.

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8
Q

How does glucagon increase blood glucose levels?

A

Stimulates glycogenolysis, and stimulates gluconeogenesis, lipolysis and ketogenesis.

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9
Q

What are the 5 main hormones important in glucose regulation?

A 
Insulin
Glucagon
Adrenalin
Cortisol
Growth hormone.
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10
Q

How does adrenalin regulate glucose?

A

It increases gluconeogenesis and lipolysis

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11
Q

How does cortisol regulate glucose?

A

Increases gluconeogenesis and lipolysis as well as decreasing tissue utilisation of glucose.

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12
Q

How does growth hormone regulate glucose?

A

Increases gluconeogenesis and lipolysis.

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13
Q

What are the symptoms of hypoglycaemia?

A

Trembling, sweating, nausea, headaches, tachycardia due to adrenalin.

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14
Q

What are the common causes of hypoglycaemia?

A

Fasting or skipping a meal, doing more activity than usual or taking too much insulin or other diabetic medication such as metformin.

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15
Q

Who are the at risk individuals for hypoglycaemia?

A

People on drugs that may interfere, alcohol, hormone deficiencies, neoplasia, sepsis, inborn errors of metabolism or glycogen storage diseases as well as neonatal babies.

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16
Q

How is hypoglycaemia managed?

A

Check the blood glucose ASAP if there is a point of care device close by. If not you can give them glucose as it is not going to cause a problem.

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17
Q

What are the 2 common causes of hyperglycaemia?

A

Type 1 diabetes and type 2 diabetes.

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18
Q

How does type 1 diabetes work?

A

There is an absolute deficiency of insulin due to autoimmune destruction of pancreatic beta cells.

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19
Q

How does type 2 diabetes work?

A

There is a relative deficiency of insulin due to insulin resistance in peripheral tissues so they produce enough insulin.

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20
Q

What is gestational diabetes?

A

Glucose intolerance that appears during pregnancy in a person with previously normal glucose tolerance.

21
Q

What are the symptoms of gestational diabetes?

A

Most women are asymptomatic but some may experience classic diabetes symptoms. These are often non-specific as they are also symptoms that occur in pregnancy.

22
Q

How is gestational diabetes controlled?

A

Diet but in 10-15% of cases it needs to be treated with insulin.

23
Q

Why it is important that gestational diabetes is not left untreated?

A

There are some bad complications for both the mother and baby including fetal hyperglycaemia, hypercalcaemia, hyperbilirubinaemia, macrosomia, respiratory distress.

24
Q

What are the factors contributing to gestational diabetes?

A 
Ethnicity
Physical inactivity
Obesity
Diet
PCOS
Genetics
25
Q

What is glycated haemoglobin?

A

Hb with sugar residue non-enzymatically bound to the amino group. Advanced glycated end products.

26
Q

How does HbA1c reflect blood glucose levels?

A

Reflects blood glucose levels over the past 8-12 weeks.

27
Q

When is HbA1c used?

A

For screening of type 2 diabetes and for long term monitoring and management of diabetes.

28
Q

What are the pros of HbA1c?

A

Fasting is not required, there is low intra-individual variation, less affected by exercise, sample transport and cell separation.

29
Q

What are the cons of HbA1c?

A

It can be affected by red cell number, if you have a haemolytic disease you will have more younger cells which have less time to become glycated so may falsely lower results.
Hb variants may give strange results
Carbamylated Hb is increased in renal disease and may interfere with the test.
Not sensitive enough for GDM and T1DM.

30
Q

When would you do an OGTT?

A

If the patient had a problem with HbA1c result or if the patient is pregnant.

31
Q

What are the rules around OGTT?

A

Patient has to have a normal diet for 3 days before the test, they must be fasting for 12 hours with no drink other than water in the last 8 hours and no exercise or smoking 1 hour before the test. Fasting sample is taken and then patient has to drink 75g of glucose in 200ml of water in 5 minutes, patient waits 2 hours and then gets another sample taken.

32
Q

What is a normal persons fasting glucose, OGTT and HbA1c?

A

Fasting glucose below 5.5 mmol/L and HbA1c below 40 mmol/mol

33
Q

What is a diabetic persons fasting glucose, OGTT and HbA1c?

A

Fasting glucose above 7mmol/L, 2 hours post 75g glucose is above 11.1mmol/L, HbA1c is above 50mmol/mol.

34
Q

What sample can glucose levels be tested on?

A

Urine, plasma, serum or csf so can use almost any tube but NaFl is recommended.

35
Q

Why is NaFl tube preferred for glucose tests?

A

Because it inhibits enolase of the glycolysis pathway inhibiting glycolysis and giving a result which is more representative of that within the patients body.

36
Q

What are the 2 tests used to measure glucose?

A 
Hexokinase (HK)
Glucose oxidase (GOD)
37
Q

How does the GOD test work?

A

It is a coupled reaction which uses GOD as an enzyme, this then produces a coloured product which is measured spectrophotometrically.

38
Q

How does the hexokinase test work?

A

It is another coupled reaction with hexokinase being the enzyme measured, it produces NADPH which is measured spectrophotometrically.

39
Q

What glucose test does the cobas use?

A

It can use both test but it is set up for the hexokinase test.

40
Q

How does transfusion affect HbA1c?

A

If the patient is diabetic but receives a transfusion from a donor which has normal HbA1c this can falsely lower results. If the donor red cells are stored in a high glucose media it could result in falsely increased HbA1c.

41
Q

How does HPLC work?

A

The Hb are separated based on interaction between stationary and mobile phases. Hb which has a negative charge binds to the positive charge of the column resin. Different Hb have different binding affinities and will elute at different rates, as they unbind they are washed through the column with a buffer and detected by a detector.

42
Q

Why are EDTA tubes commonly used for HbA1c?

A

Because the HPLC is optimised to be performed on EDTA tubes as this is done on whole blood samples.

43
Q

What are some things to look for when measuring HbA1c with HPLC?

A

Good baseline and peak shape, presence of other Hb other than HbA1c, phases P3 and P4 less than 10%, HbF less than 25%. The total area count within range of 1-3.5 million, any unknown peaks.

44
Q

How does the boronate-afifnity chromatography work?

A

Similar to HPLC but it separates glycated Hb from non glycated, HbA1c binds to the boronate resin with a higher affinity than any other Hb so is eluted off last.

45
Q

When is boronate-affinitiy chromatography used?

A

When there is a strange result or interference in HPLC HbA1c as a double check.

46
Q

What may interfere with boronate-affinity chromatography?

A

HbC may cause a small increase and high HbF may cause a falsely low HbA1c.

47
Q

How is HbA1c measured using immunoassay?

A

It is measured using a competitive immunoturbidimetric assay in which there are antibodies against HbA1c which may bind HbA1c or polyhaptins. If it binds to polyhaptens it forms an insoluble complex so the solution will become turbid and have a high absorbance. If it binds to antigen then it will form a soluble complex and lead to a lower absorbance so you have an inversely proportional relationship.

48
Q

What is fructosamine?

A

Glycated plasma proteins mainly albumin which reflect glucose control over 2-3 weeks but it is only good for measuring one patient, not good with liver or renal disease and affected by diet and drugs and it is not standardised.

MELS301 (10 decks)

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