disorders of bcca & urea cycle genetics medicine.ppt

disorders of bcca and urea cycle

1. ByBy
Dr. Phaneeshwar.Dr. Phaneeshwar.
Guide Dr. C. SorenGuide Dr. C. Soren
DISORDERS OF BCAA AND UREA CYCLE

2. BCAABCAA
Def:-Def:-
Branched Chain Organic acidurias are a Branched Chain Organic acidurias are a
group of disorders that result from an group of disorders that result from an
abnormality of specific enzymes involving abnormality of specific enzymes involving
the catabolism of Branched chain amino the catabolism of Branched chain amino
acids [Valine, Leucine & isoleucine]acids [Valine, Leucine & isoleucine]

4. 
The most common are The most common are
1.1.MSUDMSUD  Branched Chain Branched Chain αα- Ketoacid - Ketoacid
dehydrogenase def. dehydrogenase def.
2.2.IVAIVA Isovaleryl CoA dehydrogenase def. Isovaleryl CoA dehydrogenase def.
3.3.PAPA Propionyl CoA carboxylase def. Propionyl CoA carboxylase def.
4.4.MMAMMA Methyl malonyl CoA mutase def. Methyl malonyl CoA mutase def.

5. 
valinevaline

6. MSUDMSUD:- is an :- is an AR disorderAR disorder

Which causes accumulation of Valine,Leucine & Which causes accumulation of Valine,Leucine &
Isoleucine.Isoleucine.

The Synthesis of Protein, Lipoproteins & Myelin The Synthesis of Protein, Lipoproteins & Myelin
are diminished.are diminished.

Branched chain ketoacids inhibit glutamic acid Branched chain ketoacids inhibit glutamic acid
decarboxylation in the Braindecarboxylation in the Brain

8. CLINICAL FEATURES :-CLINICAL FEATURES :-

Symptoms :-Symptoms :-

Poor feeding, Lethargy, Vomiting - first week of Poor feeding, Lethargy, Vomiting - first week of
life.life.

Ataxia,convulsions,spasticity are noted.Ataxia,convulsions,spasticity are noted.

Rapid and progressive neurodegeneration .Rapid and progressive neurodegeneration .

Coma and death occurs with in a few weeks or Coma and death occurs with in a few weeks or
monthsmonths

Maple syrup odor ( ketoacids).Maple syrup odor ( ketoacids).

High level of leucine Hypoglycemic attacksHigh level of leucine Hypoglycemic attacks

9. DIAGNOSIS:-DIAGNOSIS:-
1.1.Ferric chloride--gives navy blue color Ferric chloride--gives navy blue color
with patients urine.with patients urine.
2.2. 2-4 dinitro phenyl hydrazine [DNPH] 2-4 dinitro phenyl hydrazine [DNPH]
gives yellow ppt with patients serum.gives yellow ppt with patients serum.

10. TREATMENT:-TREATMENT:-
Acute state:-Acute state:-

Maintain hydration.Maintain hydration.

Removal of BCAA and their metabolites : Removal of BCAA and their metabolites :
dialysis (Peritoneal or hemo) dialysis (Peritoneal or hemo)

Cerebral oedema : mannitol, lasix or hypertonic Cerebral oedema : mannitol, lasix or hypertonic
saline.saline.

Diet low in BCAA.Diet low in BCAA.

Orthotopic whole liver transplantation.Orthotopic whole liver transplantation.

11. Molecular basis of maple syrup urine
disease: novel mutations at the E1-alpha
locus that impair E1(alpha-2-beta-2)
assembly or decrease steady-state E1-
alpha mRNA levels of branched-chain
alpha-keto acid dehydrogenase
complex.
Characterized by an infant with sweet-smelling
urine with an odor similar to that of maple syrup,
infants with this disease seem healthy at birth but if
left untreated suffer severe brain damage and
eventually die.
A diet with minimal levels of the
amino acids leucine, isoleucine, and
valine must be maintained in order to
prevent neurological damage.

12. Isovaleric acidemia :-Isovaleric acidemia :-
Def of isovaleryl-coA dehydrogenaseDef of isovaleryl-coA dehydrogenase
Clinical manifestations :-Clinical manifestations :-

Acute form Acute form  vomiting, & severe acidosis in 1 vomiting, & severe acidosis in 1
stst
few few
days of life.days of life.
Lethargy ,convulsions , coma and Lethargy ,convulsions , coma and
death.death.

OdorOdor  sweaty feet odor sweaty feet odor. .

13. Lab findingsLab findings :- :-

Ketoacidosis,Ketoacidosis,

Neutropenia,Neutropenia,

Thrombocytopenia,Thrombocytopenia,

Pancytopenia,Pancytopenia,

Hypocalcemia,Hypocalcemia,

Hyperglycemia and Hyperglycemia and

Hyperammonemia.Hyperammonemia.

14. DIAGNOSIS :-DIAGNOSIS :-

Marked elevations of isovaleric acid Marked elevations of isovaleric acid
and its metabolites in the body fluids, and its metabolites in the body fluids,
especially urine.especially urine.

The main compound in plasma is The main compound in plasma is
isovaleryl carnitine.isovaleryl carnitine.

15. TREATMENT :-TREATMENT :-
1.1.Hydration.Hydration.
2.2.Reversal of the catabolic state (by providing Reversal of the catabolic state (by providing
adequate calories orally or IV ).adequate calories orally or IV ).
3.3. Correction of metabolic acidosis by infusing Correction of metabolic acidosis by infusing
sodium bicarbonate.sodium bicarbonate.
4.4. Removal of the excess isovaleric acid.Removal of the excess isovaleric acid.
5.5. Glycine[250mg/kg/24hr]is recommended to Glycine[250mg/kg/24hr]is recommended to
enhance formation of isovaleryl glycine.enhance formation of isovaleryl glycine.

16. Cofactor/adjunctive therapyCofactor/adjunctive therapy
Disorders Vitamin/Cofactor(dose)Disorders Vitamin/Cofactor(dose)

MSUD Thiamine (5 mg/kg/day).MSUD Thiamine (5 mg/kg/day).

MMA B12(1-2mg/day); Metronidazole MMA B12(1-2mg/day); Metronidazole

(10-20mg/kg/d);(10-20mg/kg/d);
L-Carnitine(100mg/kg/d).L-Carnitine(100mg/kg/d).

PA L-Carnitine (100mg/kg/d).PA L-Carnitine (100mg/kg/d).

IVA L-Carnitine(50-100mg/kg/d);IVA L-Carnitine(50-100mg/kg/d);
L-Glycine(150-300mg/kg/d).L-Glycine(150-300mg/kg/d).

Glutaric aciduria Carnitine.Glutaric aciduria Carnitine.

Multiple carboxylase-Biotin(10-40mg/day).Multiple carboxylase-Biotin(10-40mg/day).

18. UREA CYCLEUREA CYCLE

Reactions of the Urea CycleReactions of the Urea Cycle

Enzyme Regulation of the Urea CycleEnzyme Regulation of the Urea Cycle

Nutritional Regulation of Urea SynthesisNutritional Regulation of Urea Synthesis

Urea Cycle Disorders & TreatmentUrea Cycle Disorders & Treatment

19. Urea CycleUrea Cycle
1.1.First described by Sir Hans Krebs.First described by Sir Hans Krebs.
2.2.Removes toxic NH Removes toxic NH
44
+ +
therefore permitting therefore permitting
the use of AA as an energy source. the use of AA as an energy source.
3.3.LiverLiver major site major site

20. Most terrestrial land animals convert excess nitrogen to Most terrestrial land animals convert excess nitrogen to
ureaurea, prior to excreting it. , prior to excreting it.
Urea is less toxic than ammonia.Urea is less toxic than ammonia.
The The Urea CycleUrea Cycle occurs mainly in occurs mainly in liverliver. .
The 2 nitrogen atoms of urea enter the Urea Cycle as The 2 nitrogen atoms of urea enter the Urea Cycle as
NHNH
33
(produced mainly via Glutamate Dehydrogenase) (produced mainly via Glutamate Dehydrogenase)
and as the aminoand as the amino N of aspartateN of aspartate. .

The NHThe NH
33 and HCO and HCO
33
--
(carbonyl C) that will be part of (carbonyl C) that will be part of
urea are incorporated first into urea are incorporated first into carbamoyl phosphatecarbamoyl phosphate. .

H2NC
O
NH2
Urea

23. 
CPS & OTC Def---Hyperammonemia.CPS & OTC Def---Hyperammonemia.

ASS Def -------------Citrullinemia. ASS Def -------------Citrullinemia.

Type 1(classic citrullinemia)Type 1(classic citrullinemia)

Type 2(Neonatal Intrahepatic Cholestasis)Type 2(Neonatal Intrahepatic Cholestasis)

Type 2(Adult form)Type 2(Adult form)

ASL Def--------------Argininosuccinic Aciduria.ASL Def--------------Argininosuccinic Aciduria.

Arginase Def--------Hyperargininemia.Arginase Def--------Hyperargininemia.

HHH Syndrome---Hyperammonemia-HHH Syndrome---Hyperammonemia-
Hyperornithinemia-Homocitrullinemia.Hyperornithinemia-Homocitrullinemia.

24. UREA CYCLE DISORDERSUREA CYCLE DISORDERS

Prevalence : 1/30,000 live births Prevalence : 1/30,000 live births

inheritance usually autosomal recessive inheritance usually autosomal recessive

OTC (most common) X-linked OTC (most common) X-linked

(i) Deficiency of CPS and OTC causes hyperammonemia. (i) Deficiency of CPS and OTC causes hyperammonemia.
In general: concentration of AA metabolites In general: concentration of AA metabolites  proximal & proximal &
 distal. distal.

(ii) In all disorders: (ii) In all disorders:  NH4, NH4,  GLN, GLN,  ALA ALA

(iii) Less severe defects: (partial deficiencies) (iii) Less severe defects: (partial deficiencies)  less side less side
effects, manifested only in later childhood or adulthood.effects, manifested only in later childhood or adulthood.

25. HYPERAMMONEMIAHYPERAMMONEMIA

CARBAMYLPHOSPHATE CARBAMYLPHOSPHATE
SYNTHETASE SYNTHETASE

↑ ↑ NH4NH4

↑ ↑ Blood glutamineBlood glutamine

↓ ↓ BUNBUN

Uracil and orotic acid-NUracil and orotic acid-N


Cerebral edemaCerebral edema

Lethargy, convulsions, Lethargy, convulsions,
coma &death.coma &death.

ORNITHINE ORNITHINE
TRANSCARBAMYLASETRANSCARBAMYLASE

↑ ↑ NH4NH4

↑ ↑ Blood glutamineBlood glutamine

↓ ↓ BUNBUN

↑ ↑ URACIL AND OROTIC URACIL AND OROTIC
ACID IN BLOOD AND ACID IN BLOOD AND
URINE.URINE.

Cerebral edemaCerebral edema

Lethargy, convulsions, Lethargy, convulsions,
coma & death.coma & death.

26. Defects of Urea CycleDefects of Urea Cycle

27. PresentationPresentation

Usually normal in first 24h of life.Usually normal in first 24h of life.

Symptoms of hyperammonemia within 1-3 daysSymptoms of hyperammonemia within 1-3 days
Include: Feeding intoleranceInclude: Feeding intolerance
VomitingVomiting
LethargyLethargy
IrritabilityIrritability
Respiratory DistressRespiratory Distress
SeizuresSeizures
Coma Coma

28. DIAGNOSISDIAGNOSIS

The main criterion for diagnosis is The main criterion for diagnosis is
hyperammonemia.hyperammonemia.

Plasma ammonia conc is >200 Plasma ammonia conc is >200 µmole/L µmole/L
(normal value <35µmole/L)(normal value <35µmole/L)

↑ ↑ levels of glutamine,aspartic acid,and alanine.levels of glutamine,aspartic acid,and alanine.

A marked ↑in urinary orotic acid in pts with A marked ↑in urinary orotic acid in pts with
OTC def differs from CPS def.OTC def differs from CPS def.

31. OutcomeOutcome
MortalityMortality

Improvements in treatment have increased 1 year Improvements in treatment have increased 1 year
survival rate. survival rate.

Once past the neonatal period, long term survival Once past the neonatal period, long term survival
rate =rate =
50% OTC (Type II)50% OTC (Type II)
75% CPS (Type I)75% CPS (Type I)
95% AS and AL (Steps 3+4)95% AS and AL (Steps 3+4)

32. 
75% mental retardation (mean IQ 50), 75% mental retardation (mean IQ 50),

Seizure disorders, Seizure disorders,
 Visual deficits (proportional to extent of Visual deficits (proportional to extent of  NH NH
4 4 ), ),

Protein intoleranceProtein intolerance
 Brain: Brain:  NH NH
4 4 causes increased permeability causes increased permeability
 serotonin serotonin  behavior abnormalities behavior abnormalities
quinolinic acid quinolinic acid  neuronal injury neuronal injury
Morbidity

33. TREATMENTTREATMENT

ADEQUATE CALORIES.ADEQUATE CALORIES.

FLUID AND ELECTROLYTES.FLUID AND ELECTROLYTES.

IV LIPIDS (1G/KG/24HR).IV LIPIDS (1G/KG/24HR).

PROTEIN (0.5-1.0G/KG/24HR).PROTEIN (0.5-1.0G/KG/24HR).

SODIUM BENZOATE (250MG/KG).SODIUM BENZOATE (250MG/KG).

PHENYLACETATE (250MG/KG).PHENYLACETATE (250MG/KG).

ARGININE HCL (200-600MG/KG).ARGININE HCL (200-600MG/KG).

PERITONEAL OR HEMO DIALYSIS.PERITONEAL OR HEMO DIALYSIS.

34. Treatment:Treatment:
Stimulate Alternate PathwaysStimulate Alternate Pathways

35. FutureFuture
(i) Enzyme Replacement Therapy(i) Enzyme Replacement Therapy
(Liver Transplant) (Liver Transplant) butbut expensive and lack donors expensive and lack donors
(ii) Gene Therapy (ii) Gene Therapy  In mice to date, In mice to date,
In OTC deficient mouse transfection using adeno In OTC deficient mouse transfection using adeno virus virus
vector is successfulvector is successful
(iii) Diagnosis(iii) Diagnosis
Molecular Diagnostics (RFLP) can reveal genetic defects by Molecular Diagnostics (RFLP) can reveal genetic defects by
prenatal diagnosis when indicated.prenatal diagnosis when indicated.
Direct enzyme determination in amniocytes or Direct enzyme determination in amniocytes or chorionic chorionic
villus biopsy to determine presence/absence enzyme villus biopsy to determine presence/absence enzyme
Reactive or anticipatory treatment if defect suspectedReactive or anticipatory treatment if defect suspected

36. Case DiscussionCase Discussion

A 6-month-old infant began to vomit occasionally and ceased A 6-month-old infant began to vomit occasionally and ceased
to gain weight. At age 8½
 months he was readmitted to the
to gain weight. At age 8½
 months he was readmitted to the
hospital. Routine examination and laboratory tests were hospital. Routine examination and laboratory tests were
normal, but after 1
 week he became habitually drowsy, his
normal, but after 1
 week he became habitually drowsy, his
temperature rose to 39.4oC, his pulse was elevated, and his temperature rose to 39.4oC, his pulse was elevated, and his
liver was enlarged. The electroencephalogram was grossly liver was enlarged. The electroencephalogram was grossly
abnormal. abnormal.

Since the infant could not retain milk given by gavage Since the infant could not retain milk given by gavage
feeding, intravenous glucose was administered. He improved feeding, intravenous glucose was administered. He improved
rapidly and came out of the coma in 24
 hours. Analysis of his
rapidly and came out of the coma in 24
 hours. Analysis of his
urine showed abnormally high amounts of glutamine, uracil & urine showed abnormally high amounts of glutamine, uracil &
orotic acid but ↓ urea, which suggested a high blood orotic acid but ↓ urea, which suggested a high blood
ammonium concentration. This was confirmed by the ammonium concentration. This was confirmed by the
laboratory.laboratory.

37. Discussion:Discussion:
1.Hereditary hyperammonemia can
result from defects in genes for urea
cycle enzymes. Which enzymes might be
affected?
1.Hyperammonemia is characteristic of
all steps (including NAG synthase) Most
frequent OTC

38. 2.Considering the data (↑ uracil & orotic
acid) which enzyme may be defective in
this patient?
2.  uracil & orotic acid due to ornithine
transcarbamylase def, which causes
↑carbamyl phosphate- which leaks from
mito  cyto  increased pyrimidine
synthesis.

39. 3.Why was the urine glutamine
concentration elevated?
3. Exceeds kidneys ability GLN 
GLU + NH4+

40. 4. Offer a genetic explanation for the
observation that this disease is usually
lethal in males but not in affected
females.
4. Disease is x linked, men have only 1 X
chromosome, women have two X
chromosomes. Therefore more severe in
men than women (usually).

41. 5. This patient was treated using procedures
available at the time. He was given a daily diet of
1.5
 g of protein/kg body weight. After 2 years on
this diet, his height and weight were judged to be
normal for his age. What is the effect of diet on a
growing child in terms of nitrogen balance?
5. Growing child requires increased N, therefore
load on urea  P diet. Balance between P
restriction (prevent NH4+) and enough for growth.
Not usually sufficient for patients -ve OTC

42. 6. How would you treat a similar
patient today?
6. Hemodialysis / transfusion asap
(prevent brain damage) IV benzoate,
phenylacetate to act as NH4 traps

43. THANK YOUTHANK YOU