Group C

Wedyan Meshreky

Helen Naguib

Sharon Naguib

Part One

Ms DF recently diagnosed with leukaemia and is receiving L-asparaginase, amongst other cytotoxic agents. There have been a number of reports linking the use of L-asparaginase to diabetes mellitis. Explain..

Diabetes Mellitus

Serum glucose levels are regulated by absorption, cellular uptake, gluconeogenesis, glycogenolysis.

These processes are regulated by the pancreas, intestine, liver, kidneys and muscle.

Hyperglycaemia can result from disruption of the hormones involved in glucose regulation such as insulin or glucagon or from dysfunction of the organs involved in glucose homeostasis.

L-asparaginase

Anti-leukaemic agent used in combination with prednisone and vincristine for remission induction.

Malignant cells must acquire asparagine from surrounding fluid (such as blood) for protein synthesis whereas normal cells can synthesise their own asparagine.

Cont..

Asparaginase is an enzyme derived from micro-organisms.

It deaminates asparagine to aspartic acid & ammonia in the plasma and ECF.

Therefore its deprives tumour cells of the AA asparagine for protein synthesis and so the cells die.

L-asparaginase & Diabetes

Hyperglycaemia is a well recognised side effect of therapy with L-asparaginase.

Hyperglycaemia & glycosuria without ketonemia occurs in 1-14% of patients treated with L-asparaginase, but is reversible upon discontinuation of the drug.

Insulin therapy is frequently required. Hyperglycaemia can be worsened by the concurrent

administration of high dose glucocorticoids in combination therapy.

Is the mechanism known?

Inhibition of insulin or insulin receptor synthesis leading to a combined insulin deficiency/resistance syndrome is the presumed mechanism.

It is unclear as to why L-asparaginase targets insulin, insulin receptors, thyroid binding protein and albumin synthesis but not other proteins such as glucagon.

Other mechanisms?

Another mechanism for the development of transient or permanent diabetes mellitus is pancreatitis which occurs in 1-2% of L-asparaginase treated patients.

Incidence of pancreatitis rises when L-asparaginase is combined with other cytotoxic agents.

Part two..

L-asparaginase may affect other clinical chemistry parameters such as potassium and lipids.

Please explain..

Hypertriglyceridemia

Parson’s et al observed an increase in fasting TG levels concluding it was due to an increase in endogenous synthesis of VLDLs

Apo-B100 is a major protein found in VLDLs increased levels detected suggesting an overproduction of VLDLs.

Hypertriglyceridemia…

Mechanism is unclear Although the incidence of

hypertriglyceridemia was 67%, this was found not to be associated with pancreatitis.

Hypercholesterolaemia

Changes in cholesterol levels not found to be related to treatment with l-asparaginase.

Most likely to be associated with the use of corticosteroids.

HDL

HDL levels in px’s with ALL found to be low

Decrease in HDL levels due to either- decreased formation, or- Increased removal from circulationlow

HDL levels indicative of active cell proliferation

HDL…

During and after treatment with l-asparaginase HDL levels increased

Structural change in HDL particle from a high to a lower density particle

L-asparaginase decreases hepatic protein synthesis

Changes in lipid metabolism is reversible

Hyperkalaemia

TLS – release of intracellular contents leading to: hyperuricaemia, hyperphosphataemia, hypocalcaemia and hyperkalaemia.

Can lead to renal failure.

Hyperkalaemia…

Treatment:- Px should receive IV fluids (no K+)- Use of sodium bicarbonate, insulin or

glucose can cause transcellular shift of K+ into muscle cells decrease in K+ levels.

- Monitor px for signs of hyperkalaemia

Part Three

Describe techniques used in the general monitoring of proteinuria and specifically, the measurement of albumin levels in urine

Dipstick Method

Semi-quantitative Inexpensive Takes less than 5 minutes to complete Most common commercial method

Basic Principle

Uses a pH-dependent dye-buffer combination.

Paper spot impregnated with a citrate buffer, pH3 and a tetrabromphenol-blue indicator

Relies on the ability of amino acid groups in proteins to bind and alter the colour of the acid-base indicators.

Most sensitive to Albumin because it contains the most amino groups.

RESULTS

YELLOW = NO PROTEIN

GREEN =PROTEIN

Interpretation of Results

GRADE PROTEIN (mg/dL)

negative <10

Trace 10-20

1+ 30

2+ 100

3+ 300

4+ 1000

.False Positive results

Alkaline urine (pH>7.5)

Dipstick immersed for too long

Presence of penicillin, sulfonamides or tolbutamide

False Negative results

Dilute urine

Low molecular weight proteins

Non Albumin Proteins eg, Bence Jones Proteins

The Sulfosalicylic Acid (SSA) Turbidity Test

Qualitative measure Requires a few millilitres of freshly voided,

centrifuged urine. An equal amount of 3% SSA is added to the

specimen Acidification causes precipitation of protein in the

sample. Detects albumin, globulins and Bence-Jones proteins In alkaline urine, it is a more accurate measure than

the dipstick.

The turbidity of the suspension is proportional to the amount of protein precipitated

Amount of protein is also graded from 1 to 4