2015_06 Curso Illa - present cristina MIOPATÍAS METABÓLICAS Y

2015_06 Curso Illa - present cristina MIOPATÍAS METABÓLICAS Y

MIOPATÍAS METABÓLICAS Y MITOCONDRIALES
CURSO DE NEUROMUSCULAR
3 de Junio de 2016
INDICE
1. Alteración del metabolismo energético del músculo. Vías metabólicas.
2. Defectos en la vía glucolítica. Enfermedad de McArdle. Enfermedad de
Pompe del adulto.
3. Alteración del metabolismo/trasporte de los ácidos grasos. Déficit de CPT2
4. Enfermedades mitocondriales sistema OXPHOS.
1. Características generales
2. Características clínicas y genéticas
3. Aproximación diagnóstica y terapéutica
1274
S. DiMauro et al.
Bashar Katirji
Henry J. Kaminski
Robert L. Ruff Editors
Glucose
CGI-58
ATGL
TG droplets
Pyruvate
Fatty acids
CPT-I
123
H+
Pyruvate
Long chain
ADP
Pyruvate
Malate
ATP
Carnitine-Acylcarnitine
Translocase
CPT-II
VLCAD
ADP
Long chain Acyl-CoA
Acetyl-CoA
PDHC
Oxaloacetate
acyl-carnitine
ATP
TP
H+
Carnitine
Citrate
TCA Cycle
KT
Isocitrate
H+
SuccinyI-CoA
Fumarate
ETF-ox
Succinate
H+
I
II
CoQ
b-Oxidation
HAD
3-Hydroxyacyl-CoA
3Enoyl-CoA
LCAD
MCAD
SCAD
ETF-red
ETF-DH
FADH2
3-Ketoacyl-CoA
Acyl-CoA
AKetoglutarate
Hydratase
H+
H+
ADP
ATP
Inner introchondrial membrane
Second Edition
Outer mitochondrial membrane
Neuromuscular
Disorders in
Clinical Practice
H+
III
Cyt c
IV
V
Fig. 63.2 Schematic representation of mitochondrial metabolism.
Abbreviations: PDHC pyruvate dehydrogenase complex, CPT carnitine
palmitoyltransferase, VLCAD very-long-chain acyl-CoA dehydrogenase, TP trifunctional protein, LCAD long-chain acyl-CoA dehydrogenase, MCAD medium-chain acyl-CoA dehydrogenase, SCAD
short-chain acyl-CoA dehydrogenase, HAD 3-hydroxyacyl-CoA
dehydrogenase, KT 3-ketothiolase, ETFox oxidized form of electron
transfer flavoprotein, ETFred reduced form of electron transfer
flavoprotein, ETFDH ETF-coenzyme Q oxidoreductase, CG!-58 is the
protein that activates ATGL, ATGL adipocyte triglyceride lipase
(Reproduced from DiMauro and Haller [198], with permission)
exercise, lipid oxidation becomes the major source of energy.
Because the availability of FFA from adipose tissue is
virtually unlimited, a normal person can perform moderate
dynamic exercise for many hours.
includes two enzymes (carnitine palmitoyltransferase [CPT]
I and CPT II), a carrier molecule (l-carnitine), and a translocase (carnitine-acylcarnitine translocase, CACT). After
oxidation of pyruvate through the pyruvate dehydrogenase
1275
(the electron transport chain) to
oduction of water. The electron
four multimeric complexes (I to
carriers, coenzyme Q (or ubiquiThe energy generated by these
protons from the mitochondrial
een inner and outer mitochondrial
n electrochemical proton gradient
ne. A fifth multimeric complex
triphosphate [ATP] synthase), a
s the energy of the electrochemiTP, in a process known as oxidapling. The terminal pathway of
mprising the electron transport
own as the respiratory chain.
Glycogen
PLD
III, V
Glucose 1-P
ATP
VIII
Phosphorylase b
XIV
Glucose
Glucose 6-P
ADP+Pi
ATP
ADP+Pi
Fructose 6-P
VII
Fructose1,6 D-P
XII
Glyceraldehyde3-P
2X ATP
correlation between the circumproblems and the different roles of
sm in the provision of energy. Thus,
ith glycogenoses are almost invarile, and usually strenuous, bout of
at hurt, swell, or cramp up are those
hat particular type of exercise.
disorders of lipid metabolism, such
-chain acyl-CoA dehydrogenase
have no warning of an impending
which usually follows prolonged
be heralded by myalgia of exercisccompanied by painful cramps. In
in and by itself may cause myony muscle group may be affected,
les; a few patients with CPT II
to the emergency room in respiraode of myoglobinuria [1]. The delPT II deficiency is easily explained
ce of muscle on FFA oxidation,
. Conversely, some patients with
cy, a glycogen storage disease, note
g on their exercise ability. This is
ion of FFA, which facilitates the
arbohydrate to lipid utilization.
indeed the “business end” of mitore the energy generated by carbois released as ATP. This raises an
turbances of glycogen and lipid
ntolerance, cramps, and myoglobiduction, why did it take so long to
Phosphorylase a
0, IV, XV
UDPG
2X ADP+Pi
ercise Intolerance
) AMP kinase
P (+
AM (-)
Phosphorylase
ATP
b kinase
Lysosome
Glycdogen
II
2X ADP+Pi
3-P Glycerol-P
IX
3-P Glycerate
X
2-P Glycerate
XIII
Phosphoenolpyruvate
XI
2X ATP
Pyruvate
XI
Lactate
Fig. 63.3 Scheme of glycogen metabolism and glycolysis. Roman
numerals indicate enzymes whose deficiencies are associated with
muscle glycogenoses: II acid maltase (GAA, Pompe disease), III debrancher (GDE, Cori-Forbes disease), IV brancher (GBE, Andersen disease), V myophosphorylase (PYGM, McArdle’s disease), VII
phosphofructokinase (PFK, Tarui disease), VIII phosphorylase kinase
(PHK), IX phoshoglycerate kinase (PGK), X phosphoglycerate mutase
(PGAM), XI lactate dehydrogenase (LDH), XII aldolase A. Normal
numerals indicate glycogenoses causing exercise intolerance, cramps,
and myoglobinuria; italic numerals indicate glycogenoses causing fixed
weakness. Abbreviations: UDPG uridine diphosphate glucose, PLD
phosphorylase-limit dextrin, AMP adenosine monophosphate, ADP
adenosine diphosphate, ATP adenosine triphosphate, Pi inorganic
phosphate
GLUCOGENOGÉNESIS
DEGRADACIÓN DE TAG
CADENA RESPIRATORIA
GLUCOGENOLISIS
TRASNSPORTE AG
MITOCONDRIAL
GLUCOLISIS
BETAOXIDACIÓN DE AG
63
Alteración en el metabolismo energético del músculo
lic Myopathies
associate this syndrome with defects in the respiratory chain,
the energetic pathway “par excellence”? The answer is that
these patients often stay below the clinical radar because they
contradict the rules of mitochondrial genetics (see below) [2].
Producción de ATP
Glycogenoses
In reviewing the glycogenoses causing exercise intolerance
and myoglobinuria, we follow the metabolic “flow” in the
glycogenolytic and glycolytic pathways rather than the historical numeration (Fig. 63.3).
iMauro, Hasan Orhan Akman,
n Paradas
Glycogenoses
bolism that cause
ar disorders are
Dynamic sympsfunctions, manr without painful
in muscle breakc symptoms are
ness, sometimes
s (Fig. 63.1).
age disorders, a
and during exer-
GAA
GDE
ALD
GBE
GYG1
PHK
PYGM
B-Enolase
GYS1
PGM
PFK
PGK
PGAM
LDH
Fixed weakness
Disorders of lipid
metabolism
Carnitine transporter
Myopathic and secondary
carnitine deficiencies
MCAD
MADD
SCAD
GA II
NLSDI
NLSDM
Exercise intolerance
Cramps/myalgia
Myoglobinuria
CPT II
LIPIN
VLCAD
MTP
SCHAD
Respiratory chain defects
Complex I
Complex III
Complex IV
ISCU
CoQ10
63
nMyopathies
several factors,
ation of exercise
Neuromuscular
Disorders in
ClinicalutiPractice
rest, muscle
uro,
Akman,
ositeHasan
end of Orhan
the Fig.
63.1 The two major clinical syndromes seen in metabolic myopaxercise (close to thies. Deficient enzymes are denoted by abbreviations or gene symbols
radas
n dynamic exer- as follows: GAA acid maltase (acid D-glucosidase) (GSD II), GDE glyn isometric exer- cogen debranching (GSD III), ALD aldolase (GSD IX), GBE glycogen
branching (GSD IV), GYG1 glycogenin (GSD 0), PHK phosphorylase
especially when kinase (GSD VIII), PYGM myophosphorylase (GSD V), GYS1 glycoeration to maxi- gen synthetase, PGM phosphoglucomutase (GSD IV), PFK phosphothe type of fuel fructokinase (GSD VII), PGK phosphoglycerate kinase (GSD IX),
phosphoglycerate
mutase (GSD X), LDH lactate dehydrogenase
63 Metabolic
Myopathies
1275
ntensity of exer- PGAM
(GSD
XI), MTP mitochondrial trifunctional enzyme, MCAD mediummitochondrial membrane (the electron transport chain) to
) AMP kinase
), blood glucose chain
P (+
Lysosome
M
A
molecular
oxygen with
production of water. The
electron multiple acyl-CoA dehydrogeacyl-CoA
dehydrogenase,
MADD
(-)
Phosphorylase
ATP
Glycdogen of lipid Glycogen
chain consists of four multimeric complexes (I toDisorders
Glycogenoses
urces of energy.
nase,transport
SCAD
acyl-CoA
dehydrogenase,
GAII glutaric b kinase
II
Fixed
weakness
IV) plus
two smallshort-chain
electron
carriers,
coenzyme
Q (or ubiquimetabolism
Phosphorylase a VIII
0, IV, XV with ichthyosis
none) and
cytochrome
c. The energy
generated
by these
type
II, NLSDI
neutral
lipid
storage diseases
gy derived from aciduria
UDPG
PLD
reactions is used to pump protons from the mitochondrial Carnitine transporter
III, V
m that cause
(Chanarin-Dorfman
neutral storageGlucose
disease
with
Phosphorylase b
matrix into the space betweendisease),
inner and outer NLSDM
mitochondrial
1-P
Myopathic and secondary
uscle glycogen GAA
ATP
membranes.CPT
This creates
an electrochemical
proton gradient carnitine deficiencies
XIV
myopathy,
II
carnitine
palmitoyltransferase
II,
VLCAD
very-longsorders are
GDE
across the inner membrane. A fifth multimeric complex
Glucose
Glucose
6-P
VO2max, aerobic ALD
MCAD
chain
acyl-CoA
dehydrogenase,
SCHAD
short-chain
3-hydroxyacyl(complex
V or adenosine
triphosphate [ATP] synthase),
a
amic sympctions, manhout painful
dical Center,
uscle breakmptoms are
sometimes
g. 63.1).
disorders,
a
dical Center,
uring exer-
Bashar Katirji
Henry J. Kaminski
Robert L. Ruff Editors
Second Edition
123
ADP+Pi
rotary engine, converts the energy of the electrochemiMADD(Fe-S)Fructose
GBE
6-P
CoAtinydehydrogenase,
ISCU nonheme iron-sulfur
protein,
CoQ10
proton gradient into ATP, in a process known as oxidaVII
SCAD ATP
GYG1 cal
tion/phosphorylation
coupling. intolerance
The terminal pathway of
ADP+Pi
coenzyme
Q10 Exercise
Fructose1,6 D-P
GA
II
oxidative metabolism, comprising the electron transport
XII
PHK chain and complex V,Cramps/myalgia
is known as the respiratory chain.
NLSDI
Glyceraldehyde3-P
Myoglobinuria
PYGM
NLSDM
3-P Glycerol-P
ADP+Pi
metabolism
of glycogen is the crucial2Xsource
of
energy,
and
B-Enolase
IX
Disorders Causing Exercise Intolerance
2X ATP
3-P Glycerate
GYS1
and Myoglobinuria
fatigue
appears to set in when glycogen is exhausted.
The
X
PGM
2-P Glycerate
CPT II
there is a good correlation
between the circumXIII
typeIn general,
of circulating
substrate
utilizedLIPIN
during mild exercise
PFK
stances leading to clinical problems and the different roles of
Phosphoenolpyruvate
PGK
2X
ADP+Pi
VLCAD increase in the
glycogen
and lipid metabolism
the provision
of energy.
varies
with
time, inand
there
isThus,a gradual
Respiratory
chain
defects
XI
2X ATP
PGAMthe complaints of patients with glycogenoses are almost invariMTP
ably related to an
and over
usually strenuous,
bout of until, a fewPyruvate
utilization
ofidentifiable,
FFA
glucose
hours XIintoLactate
LDH
SCHAD
Complex
I cramp up are those
exertion, and the muscles that
hurt, swell, or
that have been engaged inComplex
that particular type
III of exercise.
Fig. 63.3 Scheme of glycogen metabolism and glycolysis. Roman
In contrast, patients with disorders of lipid metabolism, such numerals indicate enzymes whose deficiencies are associated with
Complex IV
as CPT II or very-long-chain acyl-CoA dehydrogenase muscle glycogenoses: II acid maltase (GAA, Pompe disease), III debrancher (GDE, Cori-Forbes disease), IV brancher (GBE, Andersen disISCU
(VLCAD) deficiency, often
have no warning of an impending ease), V myophosphorylase (PYGM, McArdle’s disease), VII
episode of myoglobinuria,
which10usually follows prolonged phosphofructokinase (PFK, Tarui disease), VIII1273
CoQ
phosphorylase kinase
eral factors,
of exercise
Clinical Practice,
muscle
utimoderate exercise and may be heralded by myalgia of exercis- (PHK), IX phoshoglycerate kinase (PGK), X phosphoglycerate mutase
cience+Business
Media New
York 2014
ing muscles but is never accompanied by painful cramps. In (PGAM), XI lactate dehydrogenase (LDH), XII aldolase A. Normal
numerals indicate glycogenoses causing exercise intolerance, cramps,
end of the Fig. 63.1 The
addition,
in andsyndromes
by itself may cause
myotwoprolonged
majorfasting
clinical
seen
in metabolic
myopaand myoglobinuria;
italic numerals indicate glycogenoses causing fixed
globinuria, in which case any muscle group may be affected, weakness. Abbreviations: UDPG uridine diphosphate glucose, PLD
se (close to thies. Deficient
enzymes
denoted
by abbreviations
or gene symbols
dextrin, AMP adenosine monophosphate, ADP
including
respiratoryare
muscles;
a few patients
with CPT II phosphorylase-limit
adenosine
diphosphate,
ATP adenosine triphosphate, P inorganic
deficiency
havemaltase
been taken to
the emergency
room in respira-(GSD II), GDE glyacid
(acid
D-glucosidase)
namic exer- as follows: GAA
phosphate
tory distress during an episode of myoglobinuria [1]. The delcogen
debranching
(GSD
III),
ALD
aldolase
(GSD
IX),
GBE
glycogen
eterious
effect
of
fasting
in
CPT
II
deficiency
is
easily
explained
metric exerby the increased
dependence
of muscle on (GSD
FFA oxidation,
associate
this syndrome with defects in the respiratory chain,
branching (GSD
IV), GYG1
glycogenin
0), PHK
phosphorylase
is partially blocked. Conversely, some patients with the energetic pathway “par excellence”? The answer is that
ially when kinase (GSDwhich
VIII),
PYGM myophosphorylase (GSD V), GYS1 glycomyophosphorylase deficiency, a glycogen storage disease, note these patients often stay below the clinical radar because they
on to maxi- gen synthetase,
PGM
phosphoglucomutase
(GSD
PFKthephosphoa beneficial
effect
of fasting on their exercise ability.
This isIV),
contradict
rules of mitochondrial genetics (see below) [2].
the mobilization
FFA, which facilitates the kinase (GSD IX),
(GSDby VII),
PGK ofphosphoglycerate
ype of fuel fructokinaseexplained
physiological switch from carbohydrate to lipid utilization.
PGAM
phosphoglycerate
mutase
(GSD
X),
LDH
lactate
dehydrogenase
The respiratory chain is indeed the “business end” of mito- Glycogenoses
ity of exerchondrial
metabolism, where the
energy generated enzyme,
by carbo(GSD XI), MTP
mitochondrial
trifunctional
MCAD mediumhydrate and lipid oxidation is released as ATP. This raises an In reviewing the glycogenoses causing exercise intolerance
ood glucose chain acyl-CoA
dehydrogenase, MADD multiple acyl-CoA dehydroge-
GLUCOGENOSIS
i
interesting question: if disturbances of glycogen and lipid
metabolism cause exercise intolerance, cramps, and myoglobi-
and myoglobinuria, we follow the metabolic “flow” in the
glycogenolytic and glycolytic pathways rather than the his-
sport chain) to
r. The electron
complexes (I to
me Q (or ubiquirated by these
mitochondrial
r mitochondrial
proton gradient
meric complex
P] synthase), a
e electrocheminown as oxidaal pathway of
ctron transport
atory chain.
nce
een the circumifferent roles of
of energy. Thus,
re almost invarienuous, bout of
mp up are those
of exercise.
metabolism, such
dehydrogenase
of an impending
lows prolonged
algia of exercisnful cramps. In
may cause myomay be affected,
s with CPT II
oom in respira-
glucolisis anaeróbica
FISIOLOGÍA DEL
EJERCICIO
80%
Glucógeno
128
Nutrición aplicada al deporte
40%
VO2
Tasa de oxidación (kj/min)
de ATP aportadas por los macronutrimentos. En este caso,
la cantidad de ATP por molécula de glucosa sería de 28 y 30
ATP, según fuera la lanzadera usada.
Para el caso de los ácidos grasos, la cantidad de ATP
depende de la cantidad de átomos de carbono que componen al ácido graso. El ácido palmítico, un ácido graso de 16
carbonos, aporta 96 ATP por los ciclos de Krebs y 35 ATP
por β oxidación (un total de 131 ATP).
Glucosa
FFA
oxidación ácidos grasos
Utilización de macronutrimentos
durante el ejercicio físico
Durante el ejercicio físico de ritmo estable, la contribución
de lípidos e hidratos de carbono guarda relación con la intensidad y la duración del ejercicio. En relación con la intensidad, durante el ejercicio de baja intensidad existe un predominio del aporte de los lípidos al metabolismo energético.
Sin embargo, a la medida que la intensidad aumenta, se incrementa de forma paulatina el aporte de los hidratos de
carbono. Romjin et al. (1993) estudiaron la contribución
de lípidos e hidratos de carbono a tres intensidades diferen·
tes (25, 65 y 85% del VO2máx). Si bien la contribución porcentual de los lípidos fue mayor a la intensidad del 25% del
·
VO2máx, el gasto energético para este sustrato fue mayor a la
·
intensidad del 65% del VO2máx (fig. 6-13). Atchen et al. (2002),
al valorar la oxidación de lípidos (g/min), determinaron que
la zona de mayor oxidación de lípidos se encontraba a la
·
intensidad de 64% del VO2máx (límites, 55 a 72%). En la medida que la intensidad se incrementa, existe una mayor contribución de los hidratos de carbono, debido en parte a la
mayor actividad glucolítica producto de la estimulación por
el calcio intracelular a la fosforilasa y la mayor actividad
adrenérgica generada conforme la intensidad del ejercicio se
incrementa. Los hidratos de carbono (glucosa) son un sustrato ideal para trabajos de elevada intensidad; comparados
con los ácidos grasos, la glucosa puede metabolizarse en el
40
30
20
10
0
30
60
90 120 150 180 210 240
Minutos
Oxidación de hidratos de carbono
Oxidación de lípidos
Figura 6-14. Tasa de oxidación de hidratos de carbono y lípidos durante 4 horas de ciclismo al 57% del V̇O2máx. * Significativamente diferente de los 30 min. (Adaptada de Spriet, L. y
Watt, M. 2003).
citosol, requiere menos oxígeno para oxidarse (presenta una
mayor relación oxígeno-carbono) y tiene una potencia energética mayor. Estas condiciones son relevantes si se considera que durante un esfuerzo de intensidad elevada se necesita una potencia energética alta y que en la medida que la
tensión muscular y la velocidad de acortamiento muscular
aumentan, la disponibilidad de oxígeno muscular decrece.
En cuanto a la contribución de lípidos e hidratos de
carbono en función de la duración del esfuerzo, cabe señalar que a cualquier intensidad de ejercicio, conforme la duración de éste aumenta, se observa una mayor contribución
de los lípidos a la producción de energía (Spriet y Watt,
2003) (fig. 6-14).
INTOLERANCIA AL EJERCICIO
Cal/kg/min
300
Glucógeno muscular
Triglicéridos musculares
Ácidos grasos plasmáticos
Glucosa plasmática
200
100
25
65
85
% del VO2máx
Figura 6-13. Contribución de distintos combustibles al ejercicio continuo de distintas intensidades (adaptada de Romjin, J. y cols. 1993).
06_Peniche.indd 128
21/2/11 11:42:14
GLUCOGENOSIS V
ENFERMEDAD DE McARDLE
MUTACIÓN GEN PYGM
1275
) AMP kinase
P (+
AM (-)
Phosphorylase
ATP
b kinase
Lysosome
Glycdogen
II
Glycogen
0, IV, XV
UDPG
Phosphorylase a
PLD
III, V
Glucose 1-P
ATP
✤
VIII
Phosphorylase b
✤
XIV
Glucose
✤
Glucose 6-P
✤
Fructose 6-P
✤
ADP+Pi
✤
ATP
VII en
Test
de ejercicio
Fructose1,6 D-P
antebrazo
XII
CK basal
elevada
Glyceraldehyde3-P
Estudio
molecular dirigido
3-P Glycerol-P
Prevalencia mínima: 1/150.000
Intolerancia al ejercicio (fatiga precoz/
mialgias/contracturas prolongadas/
debilidad inducidas por ejercicio)
Second wind (100%)
Mioglobinuria recurrente (50%)
Debilidad fija proximal tardía (20%)
ADP+Pi
✤
✤
2X ADP+Pi
2X ATP
2X ADP+Pi
IX
3-P Glycerate
X
2-P Glycerate
XIII
Phosphoenolpyruvate
XI
2X ATP
Pyruvate
XI
Lactate
Fig. 63.3 Scheme of glycogen metabolism and glycolysis. Roman
numerals indicate enzymes whose deficiencies are associated with
muscle glycogenoses: II acid maltase (GAA, Pompe disease), III debrancher (GDE, Cori-Forbes disease), IV brancher (GBE, Andersen disease), V myophosphorylase (PYGM, McArdle’s disease), VII
phosphofructokinase (PFK, Tarui disease), VIII phosphorylase kinase
(PHK), IX phoshoglycerate kinase (PGK), X phosphoglycerate mutase
(PGAM), XI lactate dehydrogenase (LDH), XII aldolase A. Normal
numerals indicate glycogenoses causing exercise intolerance, cramps,
and myoglobinuria; italic numerals indicate glycogenoses causing fixed
weakness. Abbreviations: UDPG uridine diphosphate glucose, PLD
phosphorylase-limit dextrin, AMP adenosine monophosphate, ADP
adenosine diphosphate, ATP adenosine triphosphate, Pi inorganic
phosphate
Entrenamiento en ejercicio aeróbico
moderado
Vitamina B6 (piridoxina)
Sacarosa antes del ejercicio
sport chain) to
r. The electron
complexes (I to
me Q (or ubiquirated by these
mitochondrial
r mitochondrial
proton gradient
meric complex
P] synthase), a
e electrocheminown as oxidaal pathway of
ctron transport
atory chain.
nce
GLUCOGENOSIS II
ENFERMEDAD DE
POMPE DEL ADULTO
)
P (+
AM (-)
ATP
Lysosome
Glycdogen
II
Glycogen
0, IV, XV
UDPG
III, V
Glucose 1-P
ATP
1275
AMP kinase
VIII
✤
✤
Phosphorylase b
XIV
Glucose
✤
Phosphorylase
b kinase
Phosphorylase a
PLD
MUTACIÓN GEN GAA
Glucose 6-P
✤
✤
Debilidad de cintura pélvica, pared
abdominal, paraespinales y cuello
Debilidad diafragmática
Debilidad lingual
CK < 1000 UI
DBS
ADP+Pi
ATP
ADP+Pi
Fructose 6-P
VII
Fructose1,6 D-P
XII
Glyceraldehyde3-P
2X ADP+Pi
2X ATP
EMG$
3-P Glycerol-P
IX
3-P Glycerate
X
2-P Glycerate
XIII
Phosphoenolpyruvate
een the circumifferent roles of
50% no diagnóstica
2X ADP+Pi
of energy. Thus,
XI
2X ATP
re almost invariXI
enuous, bout of
Lactate
Pyruvate
mp up are those
of exercise.
Fig. 63.3 Scheme of glycogen metabolism and glycolysis. Roman
metabolism, such numerals indicate enzymes whose deficiencies are associated with
dehydrogenase muscle glycogenoses: II acid maltase (GAA, Pompe disease), III debrancher (GDE, Cori-Forbes disease), IV brancher (GBE, Andersen disof an impending ease), V myophosphorylase (PYGM, McArdle’s disease), VII
lows prolonged phosphofructokinase (PFK, Tarui disease), VIII phosphorylase kinase
algia of exercis- (PHK), IX phoshoglycerate kinase (PGK), X phosphoglycerate mutase
nful cramps. In (PGAM), XI lactate dehydrogenase (LDH), XII aldolase A. Normal
numerals indicate glycogenoses causing exercise intolerance, cramps,
may cause myo- and myoglobinuria; italic numerals indicate glycogenoses causing fixed
may be affected, weakness. Abbreviations: UDPG uridine diphosphate glucose, PLD
s with CPT II phosphorylase-limit dextrin, AMP adenosine monophosphate, ADP
oom in respira- adenosine diphosphate, ATP adenosine triphosphate, Pi inorganic
Salvatore DiMauro, Hasan Orhan Akman,
phosphate
ria [1]. The delAcido graso (FA)
carnitina
and Carman Paradas
easily explained
Transportador
de FA
OCTN2
Membrana
plasmática
FFA oxidation, associate this syndrome with defects in the respiratory
chain,
e patients with the energetic
pathway “par excellence”? The answer is that
Fosfolípidos
ATGL (PNPLA2)
ge disease, note these patients oftenTriglicerido
stay below
the clinical
radar because theyLC-Acil-CoA
Diglicérido
GCI-58 (ABHD5)
ability. This is contradict the rules of mitochondrial
genetics (see below) [2].
Diacilglicerol
CPT1
h facilitates the
LC-Acil-carnitina
Membrana mitocondrial
LIPIN1
d utilization.
Fosfatidato
MTP
VLCAD
CPT2
CACT
ss end” of mito- Glycogenoses
Glicerol-3-P
rated by carbocarnitina
MC-Acil-CoA
Disorders of lipid
LC-Acil-CoA
Introduction
Glycogenoses
Fixed weakness
the glycogenoses causing exercise intolerance
P. This raises an In reviewing
Dihidroxiacetona-3-P
metabolism
in the
ogen and lipid and myoglobinuria, we follow the metabolic
MCAD “flow” Β-oxidación
Carnitine transporter
SCAD that cause
Acetil-CoA
Inborn errors Glucolisis
of glycogen and fatty acid metabolism
GAA
Myopathic and secondary
, and myoglobi- glycogenolytic and glycolytic pathways rather than the hiscarnitine deficiencies
ETFox
or predominantly
GDE
torical numeration
(Fig. 63.3). neuromuscular disorders are
t take so long to exclusively
MCAD
ALD
ETFred
characterized by dynamic or static
symptoms. Dynamic
sympETDFDH
MADD
GBE
toms are acute, recurrent,CoQ
reversible muscle dysfunctions, manSCAD
GYG1
Cadena
Exercise intolerance
GA II
ifesting as exercise intolerance,
Respiratoria myalgia with or without painful
Cramps/myalgia
PHK
NLSDI
cramps (contractures), and often culminating in muscle breakMyoglobinuria
PYGM
NLSDM
B-Enolase
down and myoglobinuria. In contrast, static symptoms are
GYS1
manifested by fixed, often progressive weakness, sometimes
PGM
CPT II
simulating dystrophic or neurogenic processes (Fig. 63.1).
PFK
LIPIN
PGK
To understand glycogen and lipid storage disorders, a
VLCAD
Respiratory chain defects
PGAM
MTP
brief review of muscle metabolism at rest and during exerLDH
SCHAD
Complex I
cise is helpful.
Complex III
The “fuel” utilized by muscle depends on several factors,
Complex IV
ISCU
most importantly the type, intensity, and duration of exercise
CoQ10
but also diet and physical conditioning. At rest, muscle utilizes predominantly fatty acids. At the opposite end of the Fig. 63.1 The two major clinical syndromes seen in metabolic myopaspectrum, the energy for extremely intense exercise (close to thies. Deficient enzymes are denoted by abbreviations or gene symbols
one’s maximal oxygen uptake, or VO2max, in dynamic exer- as follows: GAA acid maltase (acid D-glucosidase) (GSD II), GDE glycise or close to maximal force generation in isometric exer- cogen debranching (GSD III), ALD aldolase (GSD IX), GBE glycogen
branching (GSD IV), GYG1 glycogenin (GSD 0), PHK phosphorylase
cise) derives from anaerobic glycolysis, especially when kinase (GSD VIII), PYGM myophosphorylase (GSD V), GYS1 glycothere is a “burst” of activity with rapid acceleration to maxi- gen synthetase, PGM phosphoglucomutase (GSD IV), PFK phosphomal exercise. During submaximal exercise, the type of fuel fructokinase (GSD VII), PGK phosphoglycerate kinase (GSD IX),
utilized by muscle depends on the relative intensity of exer- PGAM phosphoglycerate mutase (GSD X), LDH lactate dehydrogenase
(GSD XI), MTP mitochondrial trifunctional enzyme, MCAD mediumtion. At low intensity (below 50 % VO2max), blood glucose chain acyl-CoA dehydrogenase, MADD multiple acyl-CoA dehydrogeand free fatty acids (FFA) are the primary sources of energy. nase, SCAD short-chain acyl-CoA dehydrogenase, GAII glutaric
At higher intensities, the proportion of energy derived from aciduria type II, NLSDI neutral lipid storage diseases with ichthyosis
carbohydrate oxidation increases, and muscle glycogen (Chanarin-Dorfman disease), NLSDM neutral storage disease with
myopathy, CPT II carnitine palmitoyltransferase II, VLCAD very-longbecomes an important fuel; at 70–80 % VO2max, aerobic chain acyl-CoA dehydrogenase, SCHAD short-chain 3-hydroxyacyl-
Metabolic Myopathies
63
ALTERACIÓN EN EL METABOLISMO DE LOS LÍPIDOS
S. DiMauro, MD (*)
Department of Neurology, Columbia University Medical Center,
4-424B College of Physicians & Surgeons,
630 West 168th Street, New York, NY 10032, USA
e-mail: [email protected]
CoA dehydrogenase, ISCU nonheme iron-sulfur (Fe-S) protein, CoQ10
coenzyme Q10
DÉFICIT DE CARNITINPALMITOIL
MUTACIÓN
CPT2
metabolism of glycogen
is the crucialGEN
source of
energy, and
TRANSFERASA II
fatigue appears to set in when glycogen is exhausted. The
(/!KMAN0H$s#0ARADAS-$0H$
Department of Neurology, Columbia University Medical Center,
New York, NY, USA
type of circulating substrate utilized during mild exercise
varies with time, and there is a gradual increase in the
utilization of FFA over glucose until, a few hours into
B. Katirji et al. (eds.), Neuromuscular Disorders in Clinical Practice,
DOI 10.1007/978-1-4614-6567-6_63, © Springer Science+Business Media New York 2014
1273
✤
Intolerancia al ejercicio (prolongado)
✤
Rabdomiolisis de repetición (ayunas, ejercicio,
fiebre, estrés, frío)
Biopsia normal
✤
No calambres/contracturas
✤
CK basal normal
✤
Estudio molecular: p.S113L (75%)
✤
Tratamiento: dieta rica en HC, aceite MCT,
bezafibrato
Diagnóstico genético molecular Miopatías Metabólicas
EXERCISE INTOLERANCE COMMON MUTATIONS
(PYGM, AMPD1, CPT2)
MINISEQUENCING PANEL
p.Ser113Leu
Heterozygous
P
PYGM
AMPD1
WT
C
CPT2
METABOLIC MYOPATHIES NGS PANEL
CPT2
GYS1
AGL
PYGM
LDHA
PFKM
PHKA1
PGAM2
ALDOA
ENO3
PGM1
GYG1
AMPD1
PGK1
LPIN1
ACADVL
PHKB
SERCA1
ACE
ACTN3
PGC1A
carnitine palmitoyltransferase 2
glycogensynthase1(muscle)
solutecarrierfamily22(organiccation/carnitinetransporter),
SLC22A5 member5
ACADS
acyl-CoAdehydrogenase,C-2toC-3shortchain
ACADL
Acyl-CoADehydrogenase,LongChain
amylo-alpha-1,6-glucosidase,4-alpha-glucanotransferase
ACADM acyl-CoAdehydrogenase,C-4toC-12straightchain
phosphorylase,glycogen,muscle
hydroxyacyl-CoA dehydrogenase/3-ketoacyl-CoAthiolase/enoyl-CoA
lactatedehydrogenaseA
HADHA hydratase (trifunctional protein),alpha subunit
phosphofructokinase,muscle
hydroxyacyl-CoA dehydrogenase/3-ketoacyl-CoAthiolase/enoyl-CoA
phosphorylasekinase,alpha1(muscle)
HADHB hydratase (trifunctional protein),betasubunit
phosphoglyceratemutase2(muscle)
CPT1B
CarnitinePalmitoyltransferase1B(Muscle)
aldolaseA,fructose-bisphosphate
ETFA
electron-transfer-flavoprotein,alphapolypeptide
enolase3(beta,muscle)
ETFB
electron-transfer-flavoprotein,betapolypeptide
phosphoglucomutase1
ETFDH
electron-transferring-flavoproteindehydrogenase
glycogenin1
GBE1
glucan (1,4-alpha-),branching enzyme 1
adenosinemonophosphatedeaminase1
PNPLA2 patatin-likephospholipasedomaincontaining2
phosphoglycerate kinase 1
ABHD5 abhydrolasedomaincontaining5
lipin1
solute carrier family 25(carnitine/acylcarnitine translocase),member
acyl-CoAdehydrogenase,verylongchain
SLC25A20 20
phosphorylasekinase,beta
Sarcoplasmic/EndoplasmicReticulumCalciumATPase1
angiotensinIconvertingenzyme
actinin,alpha3
Peroxisome Proliferator-Activated ReceptorGamma,Coactivator 1
ENFERMEDADES MITOCONDRIAL DEL SISTEMA OXPHOS
Mutaciones en
responsables de enfermedad:
ALTERACIÓN
DEADNmt
LA FOSFORILACIÓN
OXIDATIVA
1/5000-1/10000
Mutaciones en ADNmtMITOCONDRIALES
en sujetos sanos: 1/200
ENFERMEDADES
ADNn
ADNmt
Herencia
mendeliana
Herencia materna
Esporádico
CONTROL GENÉTICO DUAL
✤
Subunidades de los complejos (13 de las 90)
22 tRNAs y 2 rRNAs
✤
Mantenimiento del ADNmt
✤
ADNmt
comunicación
intergenómica
ADNn
Maquinaria de replicación
Mantenimiento del pool de dNTPs
✤
✤
✤
✤
✤
Deleciones múltiples
Depleción ADNmt
Subunidades de los complejos (Leigh)
Proteínas de ensamblaje
Traducción del ADNmt
Composición lipídica de la membrana mitocondrial
Dinámica mitocondrial (DOA, CMT2A, CMT4A)
Oxidative
phosphorylation
biogenesis
and regulation
AAA
Membrane dynamics
and composition
Oxidative phosphorylation
subunits
V
IV
III
I
II
dN
dNMP
dNDP
dNTP
Nucleotide
transport
and synthesis
AAA
mtDNA maintenance
and expression
CARACTERÍSTICAS DEL ADNmt
✤
16569 pb-circular, doble cadena. 37 genes. 2 rRNA, 22tRNA, 13 polipéptidos
(subunidades de la cadena). No tiene intrones.
CARACTERÍSTICAS DEL ADNmt
✤
✤
16569 pb-circular, doble cadena. 37 genes. 2 rRNA, 22tRNA, 13 polipétidos
(subunidades de la cadena). No tiene intrones.
Herencia materna
Herencia materna
CARACTERÍSTICAS DEL ADNmt
✤
16569 pb-circular, doble cadena. 37 genes. 2 rRNA, 22tRNA, 13 polipétidos
(subunidades de la cadena). No tiene intrones.
✤
Herencia materna
✤
Poliplasmia
Poliplasmia
Homoplásmico
100% Normal
Homoplásmico
100% Mutante
Heteroplásmico
25% Mutante
CARACTERÍSTICAS DEL ADNmt
✤
16569 pb-circular, doble cadena. 37 genes. 2 rRNA, 22tRNA, 13 polipétidos
(subunidades de la cadena). No tiene intrones.
✤
Herencia materna
✤
Poliplasmia
✤
Segregación mitótica
Segregación mitótica
CIGOTO
ADN mt
ADN mt mutado
MITOSIS
SEGREGACIÓN
% ADN MUTADO
0
20
HOMOPLASMIA
40
60
HETEROPLASMIA
80
100
HOMOPLASMIA
CARACTERÍSTICAS DEL ADNmt
✤
16569 pb-circular, doble cadena. 37 genes. 2 rRNA, 22tRNA, 13 polipéptidos
(subunidades de la cadena). No tiene intrones.
✤
Herencia materna
✤
Poliplasmia
✤
Segregación mitótica
✤
Efecto Umbral
Efecto Umbral
CIGOTO
UMBRAL PATOLÓGICO
mt DNA
mt DNA mutado
MITOSIS
SEGREGACIÓN
% DNA MUTADO
0
20
40
HOMOPLASMIA
60
80
100
HETEROPLASMIA
CARACTERÍSTICAS DEL ADNmt
✤
16569 pb-circular, doble cadena. 37 genes. 2 rRNA, 22tRNA, 13
polipétidos (subunidades de la cadena). No tiene intrones.
✤
Herencia materna
✤
Poliplasmia
✤
Segregación mitótica
✤
Efecto Umbral
Heterogeneidad
clínica
m.8993 T>G
Ej.
70% NARP
> 90% MILS
Manifestaciones clínicas
ptosis - oftalmoplegia externa
retinopatía
neuropatía óptica
retraso mental
convulsiones
mioclonías
ataxia
leucoencefalopatía
migrañas
parkinsonismo
sordera
miocardiopatía
alteración de la conducción
síndrome de Fanconi
glomerulopatía
alteraciones endocrinas
dismotilidad intestinal
vómitos
insuficiencia pancreática
hepatopatía
intolerancia al ejercicio
debilidad
neuropatía
Mitochondrial Disorders
10/05/14 23:21
General patterns
Specificity for mitochondrial disorders: Symmetric involvement of deep gray structures in absence of hypoxia
Hyperintensity: T2 & FLAIR images
Hypointensity: T1
Other: Delayed myelination
Bilateral signal intensities in putamen, globus pallidus, & caudate: Leigh's
Posterior cerebral hemisphere
Stroke-like lesions: MELAS
Other: Alpers
Basal ganglia calcifications: Kearns-Sayre; MELAS
White matter
Diffuse signal change in central subcortical white matter (U-fibers): Kearns-Sayre
Leukoencephalopathy with spared corpus callosum: MNGIE
Diffuse white matter changes: Some electron transport chain disorders (I-IV)
Macrocystic lesions: Complex I disorders
Biochemistry analysis
Muscle preferable to cultured fibroblasts
Fresh or Frozen muscle may be used
Combined partial defects of respiratory enzymes containing mtDNA-encoded subunits: Suggests mtDNA mutations
Can be normal in mitochondrial disorders: Especially with multiple mtDNA deletion syndromes
Molecular genetics: Mutation screening
Positive result: Confirms diagnosis
Screen for most common mutations associated with syndrome
e.g. MELAS A3243G then T3271C
Blood DNA: Adequate for
Point mutations in tRNA genes: MELAS; MERRF
Some mutations in structural genes: NARP; Lebers
Single large mtDNA deletions with systemic disorders: Kearns-Sayre; Pearson
Muscle DNA: Required for
Multiple deletions
Single mtDNA deletions in PEO & other localized disorders
MELAS point mutation in oligo- or asymptomatic relatives
Some point mutations in structural genes
Treatment
Aerobic training
Exercise tolerance: Increased
Serum lactate: Reduced
MITOCHONDRIAL DISORDERS: CLINICAL SYNDROMES
Adult onset
Alexander disease: GFAP; NDUFV1
Alpers
Alzheimer/Parkinsonism
Amino Acid disorders: Nuclear mutations
Anemia
Ataxias
Barth: Tafazzins; Xp28
Blindness
Gyrate atrophy
Optic atrophy ✤
LHON
Wolfram: WFS1; WFS2
Visual loss: SFXN4
Cardiomyopathy ✤
Carnitine disorders
Cartilage-Hair hypoplasia: RMRP; 9p21
CNS
Infantile & Childhood onset
✤
Syndromes
Congenital MD: CHKB; 2q13
Cramps
Deafness
✤ Point mutations
Maternal (mtDNA):
Amino-glycoside induced: 12s rRNA
Syndromic (HAM; MELAS; MERRF): tRNA
Non-syndromic: 12s rRNA
Nuclear mutations
✤
DIDMOAD: WFS1; 4p16
Deafness-Dystonia: DDP protein; Xq22
Diabetes
Dystonia
✤
Encephalopathies
Fatigue & Exercise intolerance
Friedreich ataxia: Frataxin; 9q13
Functional defects
Gastrointestinal ✤
HAM: mtDNA tRNA Ser
Hepatic
Occipital horn syndrome: ATPase 7a; Xq12
Huntington's chorea
Ophthalmoplegia, External (PEO)
Hypoglycemia
Dominant: Multiple mtDNA deletions
Infantile CNS: mtDNA & Nuclear mutations
Maternal: mtDNA point mutations
Inflammatory myopathies
Recessive: mtDNA deplete; Mpl mtDNA del
Sporadic: Single mtDNA deletion
IM-VAMP
Mitochondrial antibodies
? Immune (HyperThyroid)
Kearns-Sayre: Single mtDNA deletion
Pancreas
Paraganglioma
Leber's optic (LHON): mtDNA, MTND
Parkinson's
Leigh's syndrome: mtDNA & Nuclear muts
Pearson's: mtDNA deletion
Leukodystrophy
Lipomatosis: mtRNA Lys & Nuclear
Rhabdomyolysis: mtDNA
Longevity
SANDO
Maple syrup urine disease
Selenium deficiency
MEGDEL: SERAC1; 6q25
✤Skeletal & Hair
Spastic paraparesis
MELAS: mtRNA Leu + other
Spinal muscular atrophy
Menkes: ATPase 7a; Xq12
MERRF: mtRNA Lys & Ser
SCO2: 22q13
MILS
TK2: 16q22
✤
MLASA
Stuve-Wiedemann syndrome: 1p34
PUS1; 12q24
Sudden infant death: MTTL1; MTND1; HADHB
YARS2; 12p11
Systemic disorders
Toxic
MNGIE: Thymidine phosphorylase; 22q13
✤ Arsenic trioxide
Myalgias
Myoglobinuria
AZT (Zidovudine)
Myopathy syndromes
Copper
Infantile myopathies
Germanium
Fatal: mtDNA depletion
✤ Trichloroethylene
"Later-onset": mtDNA depletion
Valproate: Precipitates
Inflammatory myopathy
Liver failure in Alpers
Seizures in MELAS
Inclusion body myositis: Mpl mtDNA delete
mtDNA depletion: "Later-onset"
✤Wilson's disease: ATPase 7B; 13q14
PM + COX- muscle fibers: Mpl mtDNA delete
LGMD 1H
NARP/MILS: mtATP6
Neoplasms
Neuropathy
Motor ± Episodic weakness: mtATP6 or 8
Síndromes clínicos
CPEO
MELAS
MERFF
SANDO
MIRAS
KEARNS SAYRE
LHON
NARP
MNGIE
LEIGH
ALPERS
http://neuromuscular.wustl.edu/mitosyn.html#clinicalsyndromes
DIDMOAD
Página 16 de 132
PEO
C10orf2 (Tinkle)
Dominante
✤
✤
tRNALeu
Maternal
Deleción única
Esporádica
POLG
Recesiva
Aislada
Como un síntoma más en un cuadro multisistémico:
Afectación bulbar
Miopatía
Ataxia
Retinitis pigmentosa
Miopatía
Lipomas
Mutación A8344G
tRNALys
m.5688T>C
Miopatía
Epilepsia
mioclónica
Mutación
tRNA Asn
70-74%
88-85%
59-67%
Mutación
TK2
Miopatía
Debilidad facial
Disfagia
VMNI
dT + ATP
PEO tardía
Caterina Garone et al
Bypass therapy for Tk2 deficiency
were observed in the treated
+
function
in mutants
29-day-old
d motor
types (Tk2
) and
dCMP/dTMP
+400dCMP/dTMP
, and
wild-type Tk2
mice
ain in Tk2
(Sup-
e distance traveled, horizontal and
ing time (Fig 1C–E). Relative to
tor function !/!200dCMP/dTMP
in 29-day-old
-matched
Tk2
and
TMP
, and
wild-type
Tk2 mice
howed
decreases
in gross
muscle
ance
horizontal
r that traveled,
were independent
of theand
treatime weight
(Fig 1C–E).
Relative
to
Research
Article
ody
(Supplementary
Fig
S1).
!/!200dCMP/dTMP
myopathy
hed
Tk2 or mitochondrial abnorand
Biochemical
studies
demond1A–D).
decreases
in gross
muscle
RC activities
and of
protein
levels
were
independent
the treat-
dTTP
miopatía
Bypass therapy for Tk2 deficiency
k2!/!400dCMP/dTMP) appeared normal
n decelerated and mild head tremor
400dCMP/dTMP
Tk2!/! mice had
a mean lifespan
) appeared
normal of
!/!200dCMP/dTMP
D),
whereas
Tk2head
elerated
and mild
tremor
!
P=
0.0028;
7; Gehan–Breslow–
mice
had na =mean
lifespan of
0dCMP/dTMP
lived !/!200dCMP/dTMP
to 44.3 " 9.1 days
whereas
Tk2
eslow–Wilcoxon test) (Fig 1B). The
0028; n = 7; Gehan–Breslow–
in
postmortem histological studies of
dTMP
lived to 44.3
" No
9.1 adverse
days
k2!/!200dCMP/dTMP
mice.
–Wilcoxon
(Figin1B).
The
ncies, were test)
observed
the treated
tmortem
histological
studies
of
us
wild types
(Tk2+) and
mutants
00dCMP/dTMP
+400dCMP/dTMP
ight gain in Tk2
(Supmice.
No adverse
dTMP + ADP
dCMP
Depleción
Deleciones múltiples
Encefalomiopatía infantil
TK2
Caterina Garone et al
Histological and histochemical CNS studies confirmed dCMP/
dTMP efficacy
Histological and histochemical CNS studies confirmed dCMP/
Efficacy
of treatment in central nervous system (CNS) was demondTMP
efficacy
strated in histological studies that showed dramatic reductions in
the numbers of vacuoles in neurons of the spinal cord and cerebellar
Efficacy of treatment in central nervous
system (CNS) was demonand brain stem nuclei of 13-day-old Tk2!/!200dCMP/dTMP mice relastrated in histological studies !/!
that showed dramatic reductions in
tive to untreated 13-day-old Tk2 mice (Fig 2A and B). Furtherthe
numbers
of vacuoles
in neurons
of the IV)
spinal
cord and cerebellar
more,
cytochrome
c oxidase
(COX, complex
histochemistry
of
and
brain stem
nuclei
of 13-day-old
Tk2!/!200dCMP/dTMP
mice relacerebellum
revealed
reduced
overall COX
activity in 13-day-old
!/!
tive
to untreated
13-day-old
mice (Fig
2A and
B).and
Furtheruntreated
Tk2!/!mice
(Fig 3A) Tk2
with normal
activities
in 1329-day-old
Tk2!/!200dCMP/dTMP
(Fig 3C complex
and E) relative
to Tk2+
more,
cytochrome
c oxidase (COX,
IV) histochemistry
of
animals (Figrevealed
3B, D andreduced
F). No cell-specific
immunohistochemical
cerebellum
overall COX
activity in 13-day-old
differencesTk2
in !/!
COXmice
protein
(Fig 3Gactivities
and H) while
untreated
(Figwere
3A) detected
with normal
in 13- and
severe reduction
in complex I was identified
by immunostaining
of Tk2+
29-day-old
Tk2!/!200dCMP/dTMP
(Fig
3C
and
E)
relative to
cerebellum of 29-day-old Tk2!/!200dCMP/dTMP (Fig 3I and J).
animals (Fig 3B, D and F). No cell-specific immunohistochemical
differences in COX protein were detected (Fig 3G and H) while
Treatment crosses biological barriers
severe reduction in complex I was identified by immunostaining of
cerebellum
29-day-old
Tk2!/!200dCMP/dTMP
(Fig barriers,
3I and J).we
To confirmofthat
the treatment
crosses biological
assessed dNTP levels in isolated mitochondria. In 13-day-old
!/!
mice
relative to
Tk2+ littermates, isolated brain
untreated Tk2
Treatment
crosses
biological
barriers
mitochondria showed decreased levels of dTTP (0.67 " 0.1 pmol/
mg-protein
versus
1.0), while
isolated biological
liver
mitochondria
To
confirm
that 2.52
the "treatment
crosses
barriers, we
Deoxypyrimidine
monophosphate
bypass
therapy
revealed dNTP
reduced levels
dCTP in
levels
(1.07 "
0.8 versus 2.9
1.0)
assessed
isolated
mitochondria.
In" 13-day-old
eight (Supplementary Fig S1).
for thymidineuntreated
kinase
2 deficiency
Tk2!/! mice relative to Tk2+ littermates, isolated brain
pathy or mitochondrial abnor-
1,2
1,3
mitochondria
showedEmmanuele
decreased
levels
of 4dTTP
(0.67 1"
0.1 pmol/
. Biochemical studies
demonCaterina Garone
, Beatriz
Garcia-Diaz1, Valentina
, Luis
C Lopez
, Saba Tadesse
, Hasan
B
1
1,*
, Catarina M Quinzii
& Michio
Hirano
Akman1, Kurenai
versus
2.52 "
1.0),
while isolated liver mitochondria
activities and Oprotein
levels Tanji5mg-protein
revealed reduced dCTP levels (1.07 " 0.8 versus 2.9 " 1.0)
Abstract
Autosomal recessive mutations in the thymidine kinase 2 gene
(TK2) cause mitochondrial DNA depletion, multiple deletions, or
both due to loss of TK2 enzyme activity and ensuing unbalanced
deoxynucleotide triphosphate (dNTP) pools. To bypass Tk2 deficiency, we administered deoxycytidine and deoxythymidine monophosphates (dCMP+dTMP) to the Tk2 H126N (Tk2!/!) knock-in
mouse model from postnatal day 4, when mutant mice are phenotypically normal, but biochemically affected. Assessment of
13-day-old Tk2!/! mice treated with dCMP+dTMP 200 mg/kg/day
each (Tk2!/!200dCMP/dTMP) demonstrated that in mutant animals,
the compounds raise dTTP concentrations, increase levels of
mtDNA, ameliorate defects of mitochondrial respiratory chain
enzymes, and significantly prolong their lifespan (34 days with
treatment versus 13 days untreated). A second trial Eof
dCMP+dTMP each at 400 mg/kg/day showed even greater phenotypic and biochemical improvements. In conclusion, dCMP/dTMP
supplementation is the first effective pharmacologic treatment for
Tk2 deficiency.
B
D
Keywords deoxycytidine monophosphate; deoxythymidine monophosphate;
encephalomyopathy; therapy; thymidine kinase
Subject Categories Genetics, Gene Therapy & Genetic Disease; Metabolism
Autosomal recessive TK2 mutations cause severe mtDNA depletion
and devastating neuromuscular diseases in infants and children, as
well as mtDNA multiple deletions and progressive external
ophthalmoplegia in adults (Saada et al, 2001; Tyynismaa et al,
2012).
To elucidate the molecular pathogenesis of TK2 deficiency, we
generated a homozygous Tk2 H126N knock-in mutant (Tk2!/!)
mouse that manifests a phenotype strikingly similar to the human
infantile encephalomyopathy (Akman et al, 2008). Between postnatal day 10 and 13, Tk2!/! mice rapidly develop fatal encephalomyopathy beginning with decreased ambulation, unstable gait, coarse
tremor, and growth retardation that rapidly progress to early death
at age 14–16 days (Dorado et al, 2011). A similar phenotype was
observed in the Tk2 knockout mouse (Zhou et al, 2008).
In the Tk2!/! mice, loss of Tk2 activity caused dNTP pool imbalances with low dTTP levels in brain and decreased dTTP and dCTP
in liver, which, in turn, produce mtDNA depletion and defects of
mitochondrial respiratory chain (RC) complexes I, III, IV, and V
containing mtDNA-encoded subunits, most prominently in the brain
and spinal cord (Dorado et al, 2011).
Based on the understanding of the pathogenesis of Tk2 deficiency, we have assessed a rationale therapeutic strategy to
bypass the enzymatic defect with oral dCMP and dTMP supplementation.
DOI 10.15252/emmm.201404092 | Received 20 March 2014 | Revised 22 May
D
E
2014 | Accepted 26 May 2014
Results
dCMP/dTMP delays disease onset, prevents neuromuscular
manifestations, and prolongs lifespan of Tk2-deficient mice
Introduction
Encoded by the nuclear DNA gene TK2, thymidine kinase 2 (TK2) is
a mitochondrial matrix protein that phosphorylates thymidine and
pyrimidine nucleosides to generate deoxythymidine
monophosphate (dTMP) and deoxycytidine monophosphate (dCMP),
onwhich,
body inweight
(A) and
survival
(B) of mutant triphosphates
mice (n = 7
turn, are
converted
to deoxynucleotide
<(dNTPs)
0.005; Gehan-Breslow-Wilcoxon
test). (mtDNA) synthesis.
required for mitochondrial DNA
n clinical phenotype.deoxycytidine
Oral treatment with dCMP+dTMP 200 mg/kg/day each in milk
(Tk2!/!200dCMP/dTMP) beginning at postnatal day 4 delayed disease
onset to 20–25 days (Supplementary Video S1), when the mutant
mice developed a mild
tremor and stopped
gaining weight. In the
!/!
versus
Tk2!/!200dCMP/dTMP
,
forfourth
eachweek,
group)(Tk2
they manifested
weakness
and reduced movements.
In
contrast, Tk2!/! mice treated from day 4 with dCMP+dTMP
ATAXIA
s of the dCMP/dTMP
/!400dCMP/dTMP, P
reated mice showing no difference in average distance traveled (C), ambulatory and resting times (D), and horizontal (XY axes) and
) over 10 min in 29-day-old mutant and control mice treated with 200 mg/kg/day or 400 mg/kg/day of dCMP/dTMP (n = 5) (Data
1 Department of Neurology,
Columbia University Medical Center,
New York, NY, USA
istical analysis were performed
on Tk2!/!200dCMP/dTMP
versus Tk2+200dCMP/dTMP
and Tk2!/!400dCMP/dTMP versus Tk2+400dCMP/dTMP).
2 Human Genetics Joint PhD Program, University of Bologna and Turin, Turin, Italy
!
al phenotype.
3 Pediatric Clinic, University of Genoa, IRCCS G. Gaslini Institute, Genoa, Italy
4 Instituto de Biotecnología, Centro de Investigación Biomédica, Universidad de Granada, Parque Tecnológico de Ciencias de la Salud, Armilla, Spain
5 Department of Pathology and Cell Biology, Columbia University Medical Center, New York, NY, USA
*Corresponding author. Tel: +1 212 305 1048; Fax: +1 212 305 3986; E-mail: [email protected]
ª 2014 The Authors
ª 2014 The Authors. Published under the terms of the CC BY 4.0 license
EMBO Molecular Medicine
1
dCMP/dTMP on body weight (A) and survival (B) of mutant mice (n = 7 for each group)(Tk2!/! versus Tk2!/!200dCMP/dTMP,
dCMP/dTMP, P < 0.005; Gehan-Breslow-Wilcoxon test).
mice showing no difference in average distance traveled (C), ambulatory and resting times (D), and horizontal (XY axes) and
0 min in 29-day-old mutant and control mice treated with 200 mg/kg/day or 400 mg/kg/day of dCMP/dTMP (n = 5) (Data
nalysis were performed on Tk2!/!200dCMP/dTMP versus Tk2+200dCMP/dTMP and Tk2!/!400dCMP/dTMP versus Tk2+400dCMP/dTMP).
Ataxia sensitiva
Neuropatía óptica bilateral
Hipoacusia
OPA1
dominante
Ataxia sensitiva
ª 2014 The Authors
Oftalmoparesia
Disartria
POLG
recesivo
DIAGNÓSTICO
- Clínico, de sospecha
- Apoyado por pruebas complementarias
(hallazgos morfológicos y bioquímicos de
la biopsia muscular)
- Molecular
01
APROXIMACIÓN DIAGNÓSTICA
✤
✤
✤
Sospecha clínica:
✤
Síntomas
✤
Tipo de herencia
Test de Laboratorio
✤
CK
✤
Ácido láctico
✤
Nuevos biomarcadores FGF21
Caracterización del fenotipo
✤
EMG
✤
Neuroimagen
Biopsia de músculo
(gold standard, sobre todo para mutaciones primarias del ADNmt)
La presencia de fibras rojo rotas no es ni necesaria ni
patognomónica en el diagnóstico de las EM
✤
Presentes en adultos sanos a partir de los 50 años
✤
Hallazgo habitual en otros trastornos:
Miositis por cuerpos de inclusión
Distrofia oculofaríngea
Otros
Actividad enzimática de los complejos de la CR
✤
Normal
✤
Déficit único
✤
Déficit múltiple
✤
Déficit II+III
Subunidad estrutural complejos de CR
Proteína de ensamblaje de un
complejo específico
Genes ADNmt que controlan síntesis de
proteínas (ARNt, ARNr, macrodeleción)
ADNn que controla mantenimiento
Deficit de CoQ10
Diagnóstico molecular
Oxidative
phosphorylation
biogenesis
and regulation
AAA
Membrane dynamics
and composition
Oxidative phosphorylation
subunits
V
IV
III
I
II
dN
dNMP
dNDP
dNTP
AAA
mtDNA maintenance
and expression
Nucleotide
transport
and synthesis
mtDNA
Blázquez et al.(2016) eLS (Wiley)
Molecular genetics of OXPHOS disorders
mtDNA DELETIONS
NUCLEARGENE
mtDNAMANTEINANCE
•
• )
- )
•
( , - Mul$ple
mtDNAdele$ons
SPORADIC
mtDNALESION
• •
•
• (
-
-
SinglemtDNAdele$on
mtDNA
16,6Kb
ΔmtDNA
Southern-BlotmtDNADIGprobes
Genes“Mito”-Nucleares(nDNA):
Genesnuclearesjueganunimportantepapel
enlasenfermedadesOXPHOS:
§ 75%pacientesinfantiles
§ 30%pacientesadultos
-- OXPHOS
NUCLEAR GENES
OXPHOSbiogenesis/regulation
Assembly factors
SURF1,BCS1L,SDHAF1,ACAD9,
TMEM70,TACO1
Lipid metabolism:
AGK,TAZ
Phospholipid remodeling:
SERAC1
Disulfide relay system:
GFER
Mitochondrial homeostasis
FBXL4,CLPB
Fe-Scluster assembly/homeostasis
ISCU,BOLA3,NFU1,GLRX5,LYRM4
Mitochondrial protein import
TIMM8A,DNAJC19,SPG7
Apoptosis:
AIF1,APOPT1,FASTKD2
CoQ10biogenesis
COQ2,COQ6,PDSS2,ADCK4,COQ4,
COQ9, PDSS2,CABC1
Mitochondrial chaperones
HSPD1,CLPB,AFGL32,SPG7
mtDNA maintenance/stability
mtDNA replication
POLG,C10orf2,POLG2,RNASEH1
dNTP synthesis/salvage
DGUOK,TK2,RRM2B,TYMP
Mitochondrial fission/fusion
OPA1,MFN2,FBXL4
dN
dNMP
dNDP
dNTP
OXPHOSstructural subunits
Complex I
NDUFV1,NDUFB3,NDUFS4
Complex II
SDHA,SDHB
Complex III
UQCRB,CYC1,UQCRQ
Complex IV
COX6B1,COX7B,COX4L2
Complex V
ATP5A1,ATP5E
mRNA
rRNA
mtDNA
tRNA
OXPHOSprotein synthesis
Translation andrelease factors
TUFM,TSFM,C12orf65,GFM1
mt-tRNA modifying proteins
MTO1,GTPBP3,PUS1,TRIT1,MTFMT
mRNA processing enzymes
LRPPRC,ELAC2,PNPT1,HSD17B10
Blázquez et al.(2016) eLS (Wiley)
Molecular genetics of OXPHOS disorders
mt-aminoacyl tRNA synthetases
AARS2,DARS2,RARS2,EARS2,
YARS2,HARS2,LARS2,
Mitoribosomal proteins
MRPS16,MRPS22,MRPL3,
MRPL12,MRPL44
Genes implicados en defectos de la cadena respiratoria agrupados por vías
metabólicas
REVIEW INSIGHT
Table 1 | Products of genes that are known to be mutated in respiratory chain disorders grouped by pathway
Oxidative phosphorylation subunits
mtDNA maintenance and expression
Oxidative phosphorylation biogenesis and Nucleotide
regulation
transport and
synthesis
Membrane
dynamics and
composition
TWINKLE, MTFMT, GFM1, LRPPRC,
MPV17, MRPS16, MRPS22, POLG,
POLG2, TRMU, TSFM, TUFM,
C12orf65, MTPAP, MRPL3, SARS2,
YARS2, HARS2, MARS2, AARS2,
RARS2, EARS2, DARS2, TACO1,
MTO1, RMND1, PNPT1, PUS1
Complex I: NDUFAF1, NDUFAF2,
NDUFAF3, NDUFAF4, NDUFAF5,
NDUFAF6, ACAD9, FOXRED1,
NUBPL
Complex II: SDHAF1, SDHAF2
Complex III: BCS1L, HCCS, TTC19
Complex IV: COX10, COX15,
ETHE1, FASTKD2, SCO1, SCO2,
SURF1, COX14, COA5
Complex V: ATPAF2, TMEM70
Fe–S: ABCB7, FXN, ISCU, NFU1,
BOLA3, GLRX5
Other: DNAJC19, GFER, HSPD1,
SPG7, TIMM8A, AIFM1, AFG3L2
ADCK3, AGK,
COQ2, COQ6,
COQ9, DRP1,
MFN2, OPA1,
PDSS1,
PDSS2, TAZ,
SERAC1
Nuclear encoded
Complex I: NDUFA1, NDUFA2, NDUFA9,
NDUFA10, NDUFA11, NDUFA12, NDUFB3,
NDUFB9, NDUFS1, NDUFS2, NDUFS3,
NDUFS4, NDUFS6, NDUFS7, NDUFS8, NDUFV1,
NDUFV2
Complex II: SDHA, SDHB, SDHC, SDHD
Complex III: UQCRB, UQCRQ
Complex IV: COX4I2, COX6B1
Complex V: ATP5E
mtDNA encoded
Complex I: ND1, ND2, ND3, ND4, ND4L, ND5,
ND6
Complex III: CYTB
Complex IV: COX1, COX2
Complex V: ATP6, ATP8
12S rRNA, tRNATyr, tRNATrp,
tRNAVal, tRNAThr, tRNASer1,
tRNASer2, tRNAArg, tRNAGln,
tRNAPro, tRNAAsn, tRNAMet,
tRNALeu1, tRNALeu2, tRNALys,
tRNAIle, tRNAHis, tRNAGly, tRNAPhe,
tRNAGlu, tRNAAsp, tRNACys, tRNAAla
DGUOK,
RRM2B,
SLC25A3,
ANT1, SUCLA2,
SUCLG1, TK2,
TYMP
List of gene products was generated through synthesis of existing compilations of genes known to be mutated in respiratory-chain disease47,48, as well as review of the literature.
found to be widespread folate deficiency combined with methanol however, the success rate is projected to be much lower in milder
toxicity from homemade rum55. Formate, a by-product of metha- cases of disease, or those with adult onset.
nol metabolism, accumulates in the setting of folate deficiency and
How can we explain these unsolved cases? Most exome studies of
causes inhibition of complex IV.
singleton cases have been powered to identify recessive mutations in
Certain medications have long been known to have toxic effects on mitochondrial proteins. It is possible that these unsolved cases are a
mitochondrial function. Owing to the bacterial origins of the mito- result of dominant-acting, subtle recessive or regulatory mutations
chondrial ribosome, mtDNA translation can be adversely affected by with incomplete penetrance, all of which are difficult to identify
antibiotics such as aminoglycosides, which can cause sensorineural over the background of polymorphisms. Alternatively, these cases
deafness when administered at high doses. Individuals with certain could be due to mutations in regions of DNA that are not targeted
mtDNA mutations in the 12S ribosomal rRNA — estimated to have a for sequencing. Some cases could also have purely environmental
population prevalence of 0.19% — are predisposed to deafness from causes, as with the Cuban blindness epidemic. A tantalizing posREVIEW INSIGHT
aminoglycosides, and can experience hearing loss even with short sibility is that a subset of these unsolved cases is due to complex
exposure to the recommended doses 56,57. The viral origins of the genetic inheritance, as a result of interactions between gene varia
b
mitochondrial DNA polymerase make it susceptible to nucleoside ants that each have weak or synergistic effects, known as synergistic
63
Stroke, ataxia, epilepsy, encephalopathy
analogue antivirals (including fialuridine). This class of drugs is used heterozygosity
. Targeted exome sequencing studies have reported
and migraines
commonly for HIV, and can cause side effects such as lactic acidosis that healthy controls will typically carry a burden of about 15–20
58
Optic neuropathy,
Deafness
through mtDNA depletion .
heterozygous, loss-of-function
protein alleles within their mitoretinopathy
and external
chondrial proteomes62. This high burden of deleterious alleles is
Microorganisms are an emerging class of environmental modifi-opthalmoplegia
ers, ranging from gut microbiota to viruses. Gut bacteria are drivers probably toleratedCardiomyopathy
because of the robustness of mitochondrial netand conduction
of disease progression in ethylmalonic encephalopathy. The causal Liverworks.
However, defects
it is possible that mutations that affect multiple
failure
CPK
in themellitus
same or parallel pathways,
may conspire
gene, ETHE1, encodes an enzyme that detoxifies sulphur compounds, genes, operating Diabetes
Ácido that
láctico
which are released by gut microbiota, and its loss results in H2S Anaemia
to yield pathology.
Notably,
there is suggestive evidence
supRenal
failure
Intestinal pseudoaccumulation, with subsequent inhibition of complex IV and shortports synergistic interactions between mtDNA and
nuclear DNA
FGF21
obstruction
chain acyl-CoA dehydrogenase. Treatment with metronidazole (anand diarrhoea
variants64. Defining the genetic architecture of the large number of
Muscle weakness,
antibiotic that reduces gut microbial content) and N-acetylcysteine unsolved sporadicexercise
casesintolerance,
of mitochondrial disease represents the next
cramps, atrophy,
hypotonia
(which promotes glutathione-mediated detoxification of H2S) results Peripheral
major challenge ofandmitochondrial
genetics.
in clinical improvement59. Although a role for viral infections in the neuropathy
Biopsia
course of mitochondrial disorders has not been identified, experi- Mitochondrial
ripplesmúsculo
and responses
60
MELAS,
MERFF,
mental
studies indicate
that some viruses, such as HIV , can modu- Despite remarkable
progress
in defining the genes and environmenCadena
respiratoria
CPEO
late complex
tal triggers that underlie mitochondrial disease,
their pathogenesis
NARP,I activity.
SANDO,
Figure 1 | Phenotypic spectrum of mitochondrial disorders. a, Common
seen on a modified Gomori-trichrome-stained skeletal-muscle section;
clinical manifestations
of mitochondrial
b, Clinicalenigma.
images
anterior
four-chamber
cross-section ofoffer
a heart that shows signs of hypertrophic
remains
almost adisorders.
complete
Many
medical
textbooks
depicting pathology from patients with a variety of mitochondrial disorders.
cardiomyopathy,
including
cardiomegaly and asymmetrical septal
déficit
múltiple
LHON,
Unsolved
cases ofKSS
mitochondrial disease
thedéficit
oversimplified
explanation
that
manifests
in tissues
with
Clockwise from
top
left, 3-Tesla único
fluid-attenuated
inversion-recovery
brain disease
hypertrophy;
plain abdominal
radiograph,
showing massive bowel distention
magnetic resonance imaging demonstrating Leigh syndrome lesions, which
(arrow) in the setting of chronic intestinal pseudo-obstruction without
Over the past 25 years, most of the mitochondrial disease genes have
the
highest
ATP
demand,
or
because
of
oxidative
damage.
Although
are characterized in this image by a hyperintense signal within the caudate and
evidence of mechanical obstruction; and bone-marrow aspirate sample that
Análisis
ADNmt
en tejido
SB/L-PCR
putamen bilaterally
seen onprobably
an axial cut through
the basal ganglia;to disease,
has been stained
for
iron to demonstrate
a ringed sideroblast (arrow) —
been
identified
in familial
forms of disease,
in which it is possible
these(arrows)
factors
contribute
the
picture
is much
herencia
retinal image of theherencia
acute phase of Leber’s hereditary optic
neuropathy,
characterized
by
a
halo
of
iron-laden
mitochondria
around the nucleus of an
herencia
to follow
the segregation
of highly penetrant
causal alleles. In demonstrating
our more
complicated.
that
there
ADNmt
apropiado
(RFLP, SB)
an optic
disc with swollen nerveCellular
fibre layer thatmodels
is associated of disease
erythrocyteindicate
precursor — from
a patient
withis
myopathy, lactic acidosis and
autosómico
with engorged and obscured blood vessels (arrows); ragged red fibre (arrow)
anaemia syndrome.
experience
Massachusetts
capacity for
preservation ofsideroblastic
ATP production
through
materna
autosómica
Estudio at
dirigido
ADNnGeneral Hospital, we have found that a remarkable
65
less than 25% of patients with clinical and biochemical evidence of enhanced glycolysis , and, in animal models of respiratory chain
innovations . The mosaic composition of human mito- only 13 of which are mtDNA-encoded. Although typically depicted
mitochondrial
of an affected first-eukaryotic
or dysfunction,
pathology
can develop
without
a major
increase
in oxi-the respiratory chain is truly
chondria
is evident in the organelle’s
replication
and translation
as a linear
chain operating
in isolation,
negdisease have strong evidence
SB/L-PCR
deleción
machinery,
with the
ribosome66,67
closely
resembling
its bacterial
hub in inhibition
the network of cellular
metabolism that is characterized by
neg recentdeleciones
second-degree relative. Several
studies have applied
exome
dative
damage
. Furthermore,
the facta that
of respirasecuenciación
NGS
counterpartPanel
the DNA
polymerase resembling that of a viral convergence and divergence of pathways, supercomplex formation
61,62
múltiples
ADNmt
sequencing to establish molecular diagnoses
in singleton
cases (bacteriophage)
. tionand
can
be. tolerated,
andtheeven
beneficial
in reversibility.
certain
settings (Box 1),
única
ancestor
As discussed later,
molecular
basis of and
ADNmt
certain mitochondrial
pathologies
clear when theof
ancestry
Almostchain
all of the
cell’s redox
However, the success rate is lower than anticipated. Our experiindicates
that thebecomes
consequences
respiratory
lesions
arereactions
not ultimately feed into the
OXPHOS
of the organelle is taken into account.
respiratory chain (Fig. 2b). Complexes I and II mediate two-electron
ence has
shown that in biochemically proven, severe cases in infants
uniformly
bad,the
and
suggests
the involvement
nonlinear
of
secuenciación
During the
course
of evolution,
organelle
ceded ownership
of cer- transferof
from
NADH and modes
FADH
to the mobile elecADNn:
depleción
/ , respectively,
Panel NGS ADNn defectos tain62pathways to the rest of the cell, but retained and even acquired oth- sitron carrier
coenzyme Q, providing links to the tricarboxylic acid
exome sequencing
ADNmtshould achieve a diagnosis in about half of cases ; pathogenesis and threshold effects.
Sospecha clínica
Descripción del fenotipo
¿Síndrome clínico definido?
SI
NO
7
10
11
2
ers. For
example,
ribonucleotide
reductase — which is used for de novo (TCA) cycle. Coenzyme Q can also receive electrons from de novo
CI,
CIII,
CIV, CV
del.
multip.
mantenimiento
synthesis of deoxyribonucleotides — is found only in the cytosol, and pyrimidine
biosynthesis,
fatty-acid and amino-acid oxidation,
deficiency
of this enzyme
causes mtDNA
depletion
. In0other
choline
15 N
O V E syndrome
MBER 2
12 | V
O L 4oxidation
9 1 | N(ultimately
A T no
U R E affecting
| 3 7 9 one-carbon metabolism),
factores
ensamblaje
POLG1,POLG2,OPA1,ANT1,
cases, theLimited.
mitochondria
have retained
a duplicated copy of the cytosolic and glycolysis. Complex III, through its ‘Q-cycle’, is an adaptor that
© 2012 Macmillan Publishers
All rights
reserved
two electrons
reduced coenzyme Q and funnels indipathway, such
as for tetrahydrofolate-dependent one-carbon
metabo- receives
ADNn
Paneles
NGS,from
genes
subunidades
lism . These paralogous one-carbon pathways seem to have adopted vidual electrons to cytochrome c. Complex IV ends the respiratory
C10ORF2,TK2,TYMP,
implicados
síntesis
a different functional importance, and may be particularly relevant
in chain by en
accepting
electronsde
from cytochrome c and using them
disease states such as cancer . Understanding the logic of compartmen- to fully reduce oxygen to water. Reactive oxygen species (ROS) are
RRM2B, DGUOK,
proteínas
mt
talization and paralogous pathways is an ongoing challenge.
potentially toxic by-products
of these reactions — especially at comSUCLG1,SUCLA2, MFN2
plexes I and III — but are buffered by dedicated superoxide disPUS1,EFG1,EFTu,
Respiratory chain and its connections
mutase and catalase,mtARS2,
as well as glutathione, thioredoxin and protein
12
13
14
At the heart of mitochondria is the respiratory chain, the core
machinery for oxidative phosphorylation (Fig. 2b). Classically, the
respiratory chain is defined as four macromolecular complexes
that catalyse electron transfer from reducing equivalents, which are
derived from intermediary metabolism, to molecular oxygen. Free
energy is conserved by coupling electron transport to the formation
of a proton gradient, or proton motive force (PMF), by three of these
complexes (I, III and IV), which is then dissipated by F1F0-ATPase
(complex V) for ATP synthesis. These complexes are associated with
the inner membrane and consist of about 90 protein components,
thiol systems. Interruptions to the respiratory chain can therefore
affect nucleotide pools, TCA-cycle flux, one-carbon metabolism and
ROS signalling to unleash numerous ripples (discussed later).
The PMF is best known for driving ATP synthesis through oxidative phosphorylation, but it is linked to many other processes
(Fig. 2b). The nicotinamide nucleotide transhydrogenase relies on
the PMF to regenerate mitochondrial NADPH, which is required
for ROS homeostasis. Furthermore, the PMF is coupled to solute
and ion transport across the inner membrane, and collapse of the
PMF can halt essential biosynthetic reactions, such as Fe–S cluster
1 5 NOV E M B E R 2 0 1 2 | VO L 4 9 1 | NAT U R E | 3 7 5
© 2012 Macmillan Publishers Limited. All rights reserved
Consideraciones terapéuticas
✤
Cofactores y vitaminas (decorenone, carnicor, riboflavina, ácido fólico, etc)
✤
Tratamientos específicos:
✤
✤
MELAS: L-Arginina
✤
MNGIE: Trasplante de médula ósea
✤
Síndromes de depleción: nucleósidos
Transferencia nuclear para evitar la transmisión de mutaciones en ADNmt
Mensajes finales
1.
Las miopatías metabólicas pueden manifestarse como intolerancia al ejercicio o como debilidad muscular
fija +/- progresiva.
2.
La intolerancia al ejercicio se caracteriza por aparición de mialgias/contracturas/calambres o debilidad
inducida por la actividad física y se acompaña de elevación variable de la CK (diferenciar de astenia). La
enfermedad de McArdle es frecuente con un prevalencia 1:15000
3.
La causa más frecuente de mioglobinuria en el adulto es el déficit de CPT2 (75% p.S113L)
4.
Las enfermedades mitocondriales OXPHOS pueden ser esporádicas, de herencia autosómica (dominante,
recesiva o ligada X), o de herencia materna, dado que pueden se debidas a mutaciones en genes
localizados en dos genomas (el ADNmt y ADNn), >150 genes implicados
5.
La variabilidad clínica es elevada, con cuadros normalmente multisistémicos con afectación de SN y
músculo principalmente, aunque hay fenotipos tejido-específicos (LHON, sordera neurosensorial)
6.
En las EM siempre se debe tratar de alcanzar un diagnóstico molecular tanto para asegurar un consejo
genético adecuado como para ofrecer un tratamiento específico en algunos casos.
Unidad de Neuromuscular
Neurólogos
Laboratorio
Anatomía Patológica
Cristina Domínguez González
Jesús Esteban Pérez
Juan Francisco Gonzalo
Ana Alonso Ortíz
Miguel Ángel Martín Casanueva
Alberto Blázquez Encinar
Alberto García Redondo
Aurelio Hernández Laín
Oscar Toldos
Neuropediatría
Enfermería
Rogelio Simón
Ana Camacho Salas
Noemí Núñez Enamorado
Begoña Lucas Gordillo
Pilar Cordero Vázquez
Neumología
Pedro Benavides Mañas
Javier Sayas Díaz