nutritional factors and epigenetics in brain development and autism · 2020. 6. 15. · autism: •...
TRANSCRIPT
Nutritional Factors and Epigenetics in
Brain Development and Autism
Richard Deth, PhD
College of Pharmacy
Nova Southeastern University
FINANCIAL DISCLOSURE:
1. Member of the scientific advisory board of Immunotec Inc.
2. Research grant support from A2 Milk Corporation
3. Focus for Health advisory board member
AUTISM:
• Complex neurodevelopmental
disorder usually appearing at
1-3 yrs of age.
• Deficits in social interaction
and communication
• Repetitive stereotyped
behavior and abnormal
preoccupations
• Complex etiology involving a
combination of environmental
risk factors and genetic
predisposition
The prevalence of autism in the US has
increased >100-fold in the last 50 years
This large increase is not explained by genetic factors,
but implies a role for environmental factors
OUTLINE:
1. Development of the Brain, the Mind and Neural Networks
2. Redox/Methylation Metabolism and Autism
3. DNA Methylation and Epigenetic Regulation of Gene Expression
4. Metabolic roles of Folate, Vit B12, Vit B6, cysteine and lithium
5. D4 Dopamine Receptors and Attention
6. Default mode network dysfunction in autism
Development of the Brain,
the Mind and Neural Networks
Normal Development of the Brain
Development of the Mind
Higher level cognitive abilities (e.g. language and
social skills) require connected networks of neurons
Individual experience programs your brain
to be a personalized version of the worldwide web
Starting at birth, specialized network-forming neurons
(PVIs) migrate from stem cell incubator regions into the
cortex and hippocampus
The networked brain
HOW DO NETWORKS FORM?
Parvalbumin-expressing
interneurons (PVIs)
WERNICKE’SAREA
SPEECH
When neuronal networks fire at the same frequency,
they work together and their information combines
ON
OFF
BROCA’SAREA
Broca’s
areaWernicke’s
area
Visual Information
Auditory Information
COMPLEXPERCEPTIONS
Dopamine promotes attention by increasing
the frequency of network firing
ON
OFF
DOPAMINE
50 Hz (gamma)
ATTENDED
INFORMATION
PVI NEURONSD4R
5 Hz
Csibra et al. Science 290 1582-1585 (2000)
Increased gamma frequency activity in response to a
visual task at eight months of age vs. six months
ON
OFF
DOPAMINE
50 Hz (gamma)
ATTENDED
INFORMATION
PVI NEURONSD4R
5 Hz
↑ Energy Demand
↑ ATP Production
↑ Oxidative Metabolism↑ Reactive Oxygen Species
High Antioxidant Demand
High firing rates create high antioxidant demand
Glutathione: GSH
The primary antioxidant in cells
GLYCINEGLUTAMATE
CYSTEINE
Reducing Thiol
Environmental toxins cause their effects
by depleting cellular antioxidant levels
GSH Synthesis and Methylation Metabolic Pathways
MethionineSynthase
HCY
MET
SAH
SAM
>200Methylation
Reactions
ATP PP+Pi
Adenosine
MethylTHF
THF
Cystathionine
Cysteine
GSH
γ-Glutamylcysteine
D4HCY
D4SAM
D4SAH
D4MET
ATPPP+Pi
MethylTHF
THF
PhospholipidMethylation
Adenosine
Dopamine
Cysteine
( - )
EAAT3
AstrocytesCysteinylglycine GSH
GSSG
REDOX
SENSITIVE
ACTIVITY NEURON
D4 Dopamine Receptor
PL Methylation Cycle
Methionine
Methylation
Cycle
GSH Synthesis
Neurotrophic
Growth Factors (+)
REDOX: - The balance between reduced vs. oxidized states
- The balance between antioxidant supply and demande.g. the antioxidant glutathione (GSH)
GSH (reduced form)GSSG (oxidized form)
METHYLATION:- Addition of a carbon atom (CH3- methyl group)
e.g. DNA methylation
- S-Adenosylmethionine (SAM) is the universal donorSAM (methyl donorSAH (methylation inhibitor)
REDOXSTATUS
METHYLATIONSTATUS
Restriction of transsulfuration makes growth factors more crucial
as a source of cysteine to make the antioxidant glutathione
MethionineSynthase
HCY
MET
SAH
SAM
>200Methylation
Reactions
ATP PP+Pi
Adenosine
MethylTHF
THF
Cystathionine
Cysteine
GSH
γ-Glutamylcysteine
D4HCY
D4SAM
D4SAH
D4MET
ATPPP+Pi
MethylTHF
THF
PhospholipidMethylation
Adenosine
Dopamine
Cysteine
( - )
EAAT3
AstrocytesCysteinylglycine GSH
GSSG
REDOX
SENSITIVE
ACTIVITY NEURON
GSH Synthesis
Neurotrophic
Growth Factors (+)
TRANSSULFURATION ISPARTIALLY BLOCKED IN NEURONAL CELLS
Certain Nutritional Factors Support Redox/Methylation
MethionineSynthase
HCY
MET
SAH
SAM
>200Methylation
Reactions
ATP PP+Pi
Adenosine
MethylTHF
THF
Cystathionine
Cysteine
GSH
γ-Glutamylcysteine
D4HCY
D4SAM
D4SAH
D4MET
ATPPP+Pi
MethylTHF
THF
PhospholipidMethylation
Adenosine
Dopamine
Cysteine
( - )
EAAT3
AstrocytesCysteinylglycine GSH
GSSG
NEURON
Vit B6
Methyl B12
Blood-Brain
Barrier
Lithium(+)B12
DNA Methylation and
Epigenetic Regulation
of Gene Expression
EPIGENETICS: -Regulation of gene expression by methyl groups on DNA
and histone proteins
-Transmitted across generations
-The primary driving force for development
- Oxidative stress interferes with epigenetic regulation
Methyl Group
Oxidative Stress
Exposure to environmental toxins alters
developmental trajectory by interfering
with epigenetic regulation
Toxic
Exposure
Normal
Developmental
Trajectory
Abnormal
Developmental
Trajectory
Rate of DNA methylation change is
70-fold lower in children 0-10 yrs
than during fetal development.
Rate of change in adults > 10 yrs
is 600-fold lower than during fetal
development.
Brain DNA methylation changes are 600-fold more dynamic
during fetal development, 20-fold higher in children vs. adult
Numata S et al. Am J Hum Genet. 2012 Feb 10;90(2):260-72.
Redox/Methylation Metabolism
and Autism
A number of studies have reported abnormal
DNA methylation in autism and other
neurodevelopmental disorders.
DNA Methylation, Hydroxymethylation and Formylation
in Human Frontal Cortex of Autistic and Schizophrenic subjectsY. Zhang, N. Hodgson, H. Abdolmaleky, R. Deth, M.S. Trivedi,
Department of Pharmaceutical Sciences, Northeastern University, Boston, MA
and Department of Pharmaceutical Sciences, Nova Southeastern University, Fort Lauderdale, FL
CpG methylation of DRD4 gene
ASD and SCZ subjects
Individual CpG methylation in DRD4 gene measured using bisulfite conversion followed by pyrosequencing in postmortem frontal
cortex samples from age matched Controls (N=9) with Autism (N=12); Age matched Controls (N=9) with Schizophrenia (N=9). *indicates a significant difference between groups (* p<0.05). Site-4 was not detected in all samples although we got good signal incontrols.
D4 dopamine receptor gene is hypermethylated
In both autism and schizophrenia
Trivedi et al.
Starting in 2004, >50 studies link ASD to oxidative stress, low levels of the antioxidant glutathione (GSH)
and impaired methylation
38%
28%
36%
2006:
James SJ et al. Am J Med Genet B Neuropsychiatr
Genet. 2006 Dec 5;141B(8):947-56.
2007: A Redox/Methylation Hypothesis of Autism
Deth R et al. Neurotoxicology. 2008 Jan;29(1):190-201.
97% correct
classification
2017: Measuring Redox/Methylation Metabolites
Correctly Identifies Autistic Subjects
Methionine synthase expression
decreases with age
Methionine synthase expression
is decreased in autism
2013: Human brain expression of folate and B12-
dependent methionine synthase decreases
across the lifespan and is 50% lower in ASD
Muratore CR et al. PLoS One. 2013;8(2):e56927
Methionine synthase expression in cortex is lower
in autistic subjects vs. age-matched controls
The ASD decrease is greatest for youngest subjects,
representing an abnormal acceleration of the
usual age-dependent decrease.
This acceleration may represent a lost opportunity
for learning and development.
Brain levels of redox and methylation
metabolites normally change with age, but
change earlier in autistic subjects
Zhang Y, et al. PLoS One. 2016 Jan 22;11(1):e0146797.
Changes in autism are indicative of a premature
decrease in methylation and increased
transsulfuration pathway activity
MethionineSynthase
HCY
MET
SAH
SAM
>200Methylation
Reactions
ATP PP+Pi
Adenosine
MethylTHF
THF
Cystathionine
Cysteine
GSH
γ-Glutamylcysteine
Cysteine
( - )
( - )
PARTIALLY BLOCKED IN NEURONAL CELLS
EAAT3
HealthyGlial Cells
(Astrocytes)Cysteinylglycine GSH
GSSG GSCbl
MeCbl
SAMOHCbl
TNF-alpha( + )
( - )Inflammation
Vaccination
CBS
CGL
The pro-inflammatory cytokine TNF-alpha decreases
methionine synthase expression, similar to autism brain
Muratore CR et al. PLoS One. 2013;8(2):e56927
Vitamin B12 (Cobalamin) in the Human Frontal Cortex
MethionineSynthase
HCY
MET
SAH
SAM
>150Methylation
Reactons
ATP PP+Pi
Adenosine
MethylTHF
THF
Cystathionine
Cysteine
GSH
γ-Glutamylcysteine
D4HCY
D4SAM
D4SAH
D4MET
ATPPP+Pi
MethylTHF
THF
PhospholipidMethylation
Adenosine
Dopamine
Cysteine
( - )
PI3-kinase
( + )
PARTIALLY BLOCKED IN NEURONAL CELLS
EAAT3
HealthyGlial Cells
(Astrocytes)Cysteinylglycine GSH
GSSG
Growth
Factors
GSCbl
MeCbl(MethylB12)
SAMOHCbl
Vitamin B12 status in postmortem human brain
during aging and autism
Stabler SP N Engl J Med. 2013
Jan 10;368(2):149-60.
Levels of MethylB12 (MeCbl) and total Cbl
decrease with age in frontal cortex and levels are
prematurely decreased in autism
Zhang Y, et al. PLoS One. 2016 Jan 22;11(1):e0146797.
Ave age = 8 yrs
Thus in autism something has accelerated the
normal age-dependent decline in brain MeCbl
D4 Dopamine Receptors
and Attention
CH3
DOPAMINE
DOPAMINE –STIMULATED PHOSPHOLIPID METHYLATION
MethylfolateMethionine
Synthase
Sharma A et al. Mol Psychiatry. 1999 May;4(3):235-46.
Structural features of the dopamine D4 receptor
Seven repeats are
associated with
increased risk of
ADHD
D4 receptors are located in the post-synaptic density (PSD),
where dopamine-stimulated phospholipid methylation (PLM)
can affect neighboring proteins, “tuning” the neural
network firing rate to gamma frequency.
PSD-95
PLM
The number of D4 receptor repeats
affects the availability of phospholipids
for methylation.
DOPAMINE
7-repeats
2 or 4-repeats
Gamma frequency responses are stronger for 7-repeat D4 receptor
or 10-repeat dopamine transporter
Demiralp T et al. Cereb Cortex. 2007 May;17(5):1007-19.
Perineuronal Net
Neuropsin
mNRG-1
NRG-1Ligand
Erb-B4
PI3K
Akt
EAAT3
ApoER2
Cysteine
SelP
Selenoproteins
Parvalbumin-expressingGABAergicInterneuron
Cysteine
GSH GSSG
Dopamine
D4 Receptor
↑ROS
↑ATPDemand
GammaSynchrony
( - )
PLM ?SO3-2
Gamma synchronization during attention involves
redox-sensitive parvalbumin-expressing interneurons
and parvalbumin expression is decreased in autism
Soghomonian JJ et al. Autism Res. 2017 Nov;10(11):1787-1796.
Default mode network
dysfunction in autism
The Default Mode Network is crucial for self-identity,
social interactions, future anticipation and other
domains that are dysfunctional in autism
Synchronized Activity
of Neural Networks
Creates an
Electromagnetic
Field,
Allowing Information
To Freely Interact
Instantaneously
A speculation about
the mind:
Gamma ActivityMIND
FIELD
100-fold lower coherence in ASD
Activity of the Default Mode Network correlates
with social measures in autistic subjects
D4 Receptors
DOPAMINE
↓ Gamma
Synchrony
DNA
Methylation
Phospholipid
Methylation
↓ Attention/Self-identity
∆ Epigenetic
Effects
↓ Learning
Oxidative Stress
Environmental
Factors
AUTISM
Brain Samples:
Autism Tissue Program
Harvard Brain Tissue Resource Center
Tissue Resource Center (Australia)
Stanley Medical Research Foundation
and donor families.
Collaborators:
Antonio Persico
Suzanne De la Monte
Hamid Abdolmaleky
Yahya Al-Farsi
Steve Walker
Bernat Kocsis
Grant Support:
Autism Research Institute
SafeMinds
NIH
National Autism Association
Autism Speaks
A2 Milk Corporation
ACKNOWLEDGMENTS
Current and Former
Grad Students:
Christina Muratore
Nate Hodgson
Alok Sharma
Malav Trivedi
Yiting Zhang
Matt Schrier
Mostafa Waly
TALK ABOUT CURING AUTISM
https://www.facebook.com/tacaflorida
https://tacanow.org/local-chapters/southeast/florida/
For further information from autism moms: