Clinical aspects of protein and amino acid metabolism

Question 1

How is creatinine used clinically?

Answer 1

Estimate of muscle mass
Produced at a constant rate and amount produced depends on muscle mass

Also used as indicator of renal failure (increased in blood)

Question 2

Name one glucogenic protein

Answer 2

Alanine

Question 3

Name one ketogenic Amino Acid

Answer 3

Lysine and Leucine

Question 4

Name one Amino Acid that is both keto and glucogenic

Answer 4

Tyrosine

Question 5

In what syndrome can you see excessive break down of protein, leading to straie fromation?

Answer 5

Cushings

Question 6

Name the 9 essential Amino Acids

Answer 6

Isoleucine
Lysine
Threonine
Histidine
Leucine
Methionine
Phenylalanine
Tryptophan
Valine

Question 7

What are the two key aminotransferases? WHat are they used for clinically?

Answer 7

Alanine aminotrnsferase and aspartate aminotransferase

Their levels are increased in conditions causing extensive cellular necrosis eg. Viral hepatitis, Autoimmune liver diseases, Toxic injury

Question 8

Describe refeeding syndrome

Answer 8

When people who have been starved are given a lot of food, the enzymes involved in the urea cycle have been suppressed, so when the Amino Acids have been broken down, they are broken down to ammonia that cannot be removed, ammonia is toxic.

Question 9

Describe what a defect in the urea cycle would cause

Answer 9

partial loss of enzyme function

Leads to hyperammonia and accumulation and excretion of urea cycle intermediates

Question 10

What does the severity of a urea cycle defect depend on?

Answer 10

Nature of defect

Amount of protein eaten

Question 11

Describe 6 symptoms of jurea defect

Answer 11

vomiting
lethargy
irritability
mental retardation
seizures
coma

Question 12

How would you manage urea defect?

Answer 12

Low protein diet

replace aas in diet with keto acids

Question 13

Why is ammonia so toxic?

Answer 13

Readily diffusible and toxic to brain

Question 14

What can a prblem in amino acid metabolism lead to?

Answer 14

Intellectual impairment

Question 15

What is the most common Amino Acid metabolism

error? Describe it

Answer 15

Phenylketouria
Deficiency in phenylalanie hydroxylase
Acculmulation of phenylalanine
Get phenylketones in urine
Musty smell to urine

Note phenylalanine converted to tyrosine. Tyrosine used to make number of chemicaql (Noradrenaline, adrenaline, dopamine, melanin, thyroid hormone) so these pathways affected

Question 16

Treatment of phenylketouria?

Answer 16

Low phenylalanin diet

Question 17

Symptoms of phenylketouria?

Answer 17

Severe intellectual disability
developmental delay
microcephaly
seizures
hypopigmentation

Question 18

Describe homocysteinuria

Answer 18

problem breaking down methionine
Excess homocysteine excreted in urine
Affects connective tissue, muscle, Central Nervous System, and CVS

Question 19

Treatment of homocysteinurias?

Answer 19

Low methionine diet

Question 20

Describe how phenylketouria effects brain development

Answer 20

Competes for transport across blood brain barrier via Large neutral Amino Acid transporter
excess phenylalanine can saturate this
other LNAA in brain can decrease–>inhibition of protein and neurotransmitter

causes mental retardation

Question 21

What syndrome are the symptoms of homocysteinuria like?

Answer 21

Marfans

High levels of homocysteine affects collagen and elastic fibres
lens dislocation and skeletal deeformities caused