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Transcript of Bilirubin and Jaundice - columbia.edu · Bilirubin and Jaundice ... Jaundice Defect in Conjugation...
1
Bilirubin and Jaundice
Pathways of Bilirubin Synthesis and Catabolism
Porphogens
Fe
Heme
Globin
Hgb
+
+
Urobilinogen StercobilinFecalPigments
UrineUrobilinogen
Heme PrecursorsMyoglobinNon-Hgb HemeProteins
ShuntPathwayFree Bilirubin – Albumin Complex
ConjugatedBilirubin
Hgb
Biliverdin
Bilirubin
Fe
Globin
RBCsBone
MarrowReticuloendothelial
System (RES)
2mg
70mg
68mg
2
Labeling of RBC hemoglobin and fecal stercobilin
0.3
0.2
0.1
0.1
0.08
0.06
0.04
0.02
20 40 60 80 100 120 140 160 180
A:
Ato
m %
exc
ess
15N
of
ster
cob
ilin
B:
Ato
m %
exc
ess
15N
of
hae
min
B
A
Times ( days)
Labeling of red cell hemoglobin and fecal stercobilinin a normal human given 15N orally
X
X X
X X X
XX
X
X X
X
X
X
X
Sources of bilirubin production in the rat
Early Bilirubin15%
0-3 Days
Late Bilirubin65%
40-80 Days
Non-HemoglobinSources (liver)
Red CellSenescence
IncreasedErythropoiesis
Sources of bilirubin production in the rat, as adduced from studies of thelabeling of plasma bilirubin in Gunn rats and bile bilirubin in normal rats.
3
NN
N NFe
COO COO
C
NN
N N
OOC COO
OH HO
H H
H
NN
NH N
OOC COO
OH HO
H
NADPH NADP
O2NADPHNADP
Fe (II)O2 CO
Biliverdin
reductase
NADPHNADP
Hemin +
heme-oxygenase complex
hydroxyheme-oxygenase complex
biliverdin
bilirubin
NN
N NFe
COO COO
OH
5
N NH
NNHFe
Me
CH
CHCH2
Me
CH2 CH2 CO2H
MeMe
H2C CH2 CH2 CO2H
A B
CD
γ
β
α
δ
NH
NH
NH
CH CH2CH
NH
O
MeCH2MeCHMe Me CH
O
CH2
C
CH2
CH2
CCH2
OO O OO O
OH
OHHO
COOH COOH
OHHO
HOCH2
NH
NH
NH
CH CH2CH
NH
O
MeCH2MeMe Me CH
OA B C D
CHCH2 CH2
CO2H
CH2
CH2
CO2HCH2
A B
C
D
BILIRUBIN - IX α DIGLUCURONIDE
BILIRUBIN – IX α (convoluted structure)
BILIRUBIN – IX α (planar structure)
A.
B.
C.
CO (excreted via lungs)
Fe (reutilized)
HN
HN
NH
NH
C OO
C
C
OO
OO
H
H
HN
HN
NH
NH
C OO
C
C
OO
OO
H
GA
HN
HN
NH
NH
C OO
C
C
OO
O
GA
OGAConjugation prevents
internal H-bonding by the-COOH groups of Bilirubin
BILIRUBINS:
UNCONJUGATED (UCB)
MONO-GLUCURONIDE
(BMG)
DIGLUCURONIDE(BDG)
2
1
BILIRUBIN CONJUGATION IN MICROSOMESINVOLVES TWO STEPS, MEDIATED BY
ONE BILIRUBIN-UDPGA TRANSFERASE
UDPGA
UDP
UDPGA
UDP
UDPGATRANSFERASE
6
OATP MDR2
(=cMOAT)
UROBILINOGENS ARE FORMED BY DECONJUGATION AND REDUCTION OF BILIRUBINS BY INTESTINAL BACTERIA
CONJUGATED BILIRUBIN
UNCONJUGATEDBILIRUBIN
Deconju-gation
A UROBILINOGEN
Reduction
NHN
HH
N HN
COOGA COOGA
M
MV
M VO O
M
NHN
HH
N HN
COOH COOH
M
MV
M VO O
M
NHN
HH
N HN
H2C CH2
COOH COOH
M
ME
M EO O
M
H H
2 GA + 8HM = MethylE = EthylV = Vinyl
7
Slow
Fast
FRACTIONAL DIAZO REACTION OF PLASMA
R R
Directreaction
Indirectreaction
CONJUGATEDBILIRUBIN
UNCONJUGATEDBILIRUBIN
N+
N
SO3H
+
N+
N
SO3H
+
DIA
ZO
RE
AG
EN
T
8
R R
CONJUGATEDBILIRUBIN
UNCONJUGATEDBILIRUBIN
N+
N
SO3H
+ + ACCELERATOR
(ALCOHOL, CAFFEINE)
TOTAL – DIRECT INDIRECT=
TOTAL DIAZO REACTION OF PLASMA
Bilirubinuria in Jaundice
UNCONJUGATED PLASMA BILIRUBIN (B) CONJUGATED
NO BILIRUBIN BILIRUBIN ++
URINE
PLASMA
(A=ALBUMIN)
11
NH
NH
NH
CH CH2CH
NH
O
MeCH2MeMe Me CH
OA B C D
CHCH2 CH2
COOH
CH2
CH2
COOHCH2
NH
NH
NH
CH CH2CH
NH
O
CH2MeMe Me CH
O
CH2
COOHCH2
CH2
CH2
COOH
Me CHCH2
Structure of the α and β isomers of bilirubin IX. In the IXβ isomer (and in the γ and δ isomers, not shown) the propionic acid groups are moved to positions other than those indicated on the central pyrrole rings B and C of bilirubin IXα.
Bilirubin IX α
Bilirubin IX β
2.5
2.0
1.5
1.0
0.5
16
12
8
4
0 8 16 24 0 2 4 6 8 10
LiverCo-PPLiverSn-PP
Hem
e O
xyge
nase
(nm
ol b
ilirub
in/m
g ph
Effect of Sn-protoporphyrin (Sn-PP) and CO-protoporphyrin (Co-PP) when administeredonce at a dose of 50 μmol/kg body wt on hepatic heme oxygenase activity in the rat.
Time(hours) (days)
12
18
16
14
10
-4 0 2 4 0 1 2 3 4 5 6 7
12
2.5
5.0
7.5
10.0
Effect of Sn-protoporphyrin (Sn-PP) (100 μmol/kg body wt) administeredat 4d before and on the day of surgery on hyperbilirubinemia in the
bile-duct-ligated rat. Effect of Sn-PP (2 x 0.25 μmol/kg body wt) on the levels of serum bilirubin in a patient with primary biliary cirrhosis (PBC).
Time (days)
Bile-DuctLigation
RAT PBC(50 )
Sn-PP
Pla
sma
Bilir
ubin
mg/
dl Control
Sn-PP
UGT1 gene
1J 1I 1H 1G 1F 1E 1D 1C 1B 1A 2 3 4 5
5’ 3’
mRNA B-UGT1
Phenol
UGTs
NH2 COOH
enzymesubstrate binding site UDPGA
binding sitemembranespanningregion
285 amino acids 246 amino acids
13
UDPGT promoter A(TA)6TAA
UDPGT nullMutation
Bolivian Squirrel MonkeyGunn ratAnimal Model
BenignKernicterusPrognosis
2-7% of populationRarePrevalence
Increased proportion of monoglucuronide
Small amounts of unconjugatedbilirubin
Pigments in bile
ReductionNo effectEffect of Phenobarbital on plasma bilirubin
30-50% of normalUndetectableHepatic bilirubin-UDPGT activity
Usually normal; elevated in a minority of cases
NormalPlasma BSP retention at 45 min
50-85 μM (fluctuates)340-860 μMPlasma bilirubin
Gilbert SyndromeCrigler-Najjar Type ICharacteristics
Unconjugated Hyperbilirubinemia
MRP2Mutation
BenignBenignPrognosis
RareUncommon (1:1300 in Persian Jews)Prevalence
Autosomal recessiveAutosomal recessiveMode of inheritance
Elevated total; elevated proportion of coproporphyrin I but <80%
Normal total >80% as coproporphyrin IUrinary coproporphyrin
Elevated; no secondary rise at 90 min
Normal or elevated; secondary rise at 90 min45-min plasma BSP retention
Normal except for bilirubinNormal except for bilirubinRoutine liver function tests
Elevated, usually between 2 and 5 mg%, occasionally as high as 20 mg%; predominantly direct-reacting
Elevated, usually between 2 and 5 mg%, occasionally as high as 20 mg%; predominantly direct-reacting
Serum bilirubin
NormalDark pigment; predominantly in centrilobular areas; otherwise normal
Histology of liver
NormalGrossly blackAppearance of liver
Rotor SyndromeDubin-Johnson SyndromeCharacteristic
Chronic conjugated hyperbilirubinemias
14
Hemolysis Hepatocellular
Conjugated bilirubin
Jaundice
Defect in Conjugation
Unconjugated bilirubin
Intrahepatic Extrahepatic
Cholestatic
15
Hemolysis Hepatocellular
Conjugated bilirubin
Jaundice
Defect in Conjugation
Unconjugated bilirubin
Intrahepatic Extrahepatic
Cholestatic
16
Liver Function Tests
• Bilirubin• PT (Prothrombin time) • Glucose• Cholesterol• ALT (alanine aminotransferase)• AST (aspartate aminotransferase)• Alkaline phosphatase• GGT (γ-glutamyltranspeptidase)
Imaging
• Ultrasound• CT scan• Liver-spleen scan• Radionuclide biliary scan• ERCP (endoscopic retrograde
cholangiopancreatography)• Transhepatic cholangiography
17
Hemolysis Hepatocellular
Conjugated bilirubin
Jaundice
Defect in Conjugation
Unconjugated bilirubin
Intrahepatic Extrahepatic
Cholestatic
↑ BR
Nl BD Dilated BD
↑ AP↑ ALT
18
Bilirubin Metabolism
•Blood•Conjugated & Conjugated
•Urine – Urobilinogen•Stool – Stercobilin
NH
NH
NH
CH CH2CH
NH
O
MeCH2MeMe Me CH
OA B C D
CHCH2 CH2
COOH
CH2
CH2
COOHCH2
N
N N
N
Fe
MV
V
M
CH2
CH2
COOH
M
M
CH2
CH2
COOH
α
β
γ
δ
plus 3 O minus Fe
minus CO
A
B
D
C
Ferroprotoporphyrin IX(Protoheme)
Bilirubin IX α
Conversion of protoheme (ferroprotoporphyrin IX) to bilirubin IXα. Cleavage of the protoporphyrin ring occurs selectively at the α-methene bridge. The bridge carbon atom is oxidized to carbon monoxide.
19
BiliverdinReductase
M = MethylE = EthylPr = Propionyl
NN
N N
M
M
M V
M
Pr Pr
V
Fe
CH
α
β
γ
δ
NNH
HN H
N
M
M
M VO O
M
Pr Pr
V
NHN
HH
N HN
H2C
M
M
M
VO O
M
V
HemeOxygenase
BILIVERDIN IXα
BILIRUBIN IXαHEME
BILIRUBIN IS PRODUCED BYOXIDATION OF HEME AND
REDUCTION OF THE RESULTANT BILIVERDIN
O2 &NADPH
NADP+
CO Fe3+ NADPH
NADP+