Mitochondrial Autism-A Unique Subpopulation and Piece of the Puzzle?

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Mitochondrial Autism— A Unique Subpopulation and Piece of the Puzzle?
Presented 5/25/2008 By Jon S. Poling MD PhD Clinical Assistant Professor, Department of Neurology, Medical College of Georgia Partner, Athens Neurological Associates
“The Low Hanging Fruit” for Diagnosis and Treatment
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Mitochondrial Dysfunction Immune dysfunction/ inflammatory biomarkers
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Guiding Principles of New Paradigm
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Autism is a behavioral syndrome, not a medical diagnosis, with multiple etiologies. The prevalence of Autism is increasing—which autism(s)? The rise in Autism cases is due to a complex interaction between genetics and environment. Autism is a systemic disorder with primary neurological manifestations. Based on biological markers, subpopulations must be distinguished to guide proper basic science, epidemiology, diagnosis, treatment, and prevention. Epidemiology and Genetics have to date failed Autism because the clinicians have not properly defined the endophenotypes/subpopulations
The Mighty Mitochondria
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1000 proteins located in the mitochondria, 13 are encoded by the mitochondrial DNA (mtDNA), while the remainder are nuclear-encoded (on the chromosomes) and imported into mitochondria. 75% sporadic occurence
Mitochondrial disease
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Young field, 1988 DC Wallace, Leber’s Extremely complex genetics and clinical phenotypes mtDNA and nuclear DNA Not just powerhouse—programmed (apoptotic) cell death Genotypes known now to have multiple phenotypes
http://neuromuscular.wustl.edu/pathol/diagrams/mito.htm http://www.umdf.org/ http://www.clevelandclinic.org/health/health-info/docs/1600/167
Autism & Mitochondrial Dysfunction A New Medical Finding?
New Or Redux?
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Dr. Mary Coleman, Georgetown U 1985 4 of 80 (5%) of patients with lactic acidemia 1 of 4 pts with regression Propose primary defect in carbohydrate metabolism, pyruvate dehydrogenase Speculate that Ketogenic diet may be helpful
Autism & Mitochondrial Dysfunction A rare and unique situation?
Mitochondrial Dysfunction emerging as most common medical condition associated with autism.
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Of 159 autism patients in one autism clinic, 38% had non-specific biochemical abnormalities. Poling et al. Developmental regression and mitochondrial dysfunction in a child with autism. J Child Neurol, 2006. 21(2): p. 170-2. 7.2% of patients with Autism could be classified as having a ‘definite’ mitochondrial respiratory chain disorder and 20% had elevated serum lactic acid Oliveira, G., et al., Mitochondrial dysfunction in autism spectrum disorders: a population-based study. Dev Med Child Neurol, 2005. 47(3): p. 185-9. 2nd study 4%; Oliveira, G., et al., Epidemiology of autism spectrum disorder in Portugal: prevalence, clinical characterization, and medical conditions. Dev Med Child Neurol, 2007. 49(10): p. 726-33.
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Mitochondrial Dysfunction emerging as most common medical condition associated with autism.
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36% of 100 autism patients have total carnitine levels 1SD below mean control, pattern suggestive mild mitochondrial dysfunction. Filipek, P.A., et al., Relative carnitine deficiency in autism. J Autism Dev Disord, 2004. 34(6): p. 615-23. 65% of autism pts referred for mitochondrial evaluation to specialty clinic positive for OxPhos disorder on muscle biopsy. Shoffner, J., L.C. Hyams, and G.N. Langley, Oxidative Phosphorylation (OXPHOS) Defects in Children with Autistic Spectrum Disorders, in AAN. 2008: Chicago.
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Autistic Spectrum Cases--AST vs. Age
60 50
AST (IU/L)
40 30 20 10 0 0 10 20 30
AST declines by 3.2 IU/L/10years
JS Poling Johns Hopkins Neurology Grand Rounds 6/21/2001 Metabolic Disturbances in Autistic Children: The KKI Experience from 1995-
Years
JS Poling Johns Hopkins Neurology Grand Rounds 6/21/2001 Metabolic Disturbances in Autistic Children: The KKI Experience from 19952001
Autistic Spectrum--CPK
300 250 200
IU/L
150 100 50 0 0
7 of 14 elevated 50%
CK
Mean 168 N=14
5 Age (years) 10 15 20
Autistic Spectrum—Lactate
5 4
Mmol/L
3 2 1 0 0 5 10 15 Age (years) 20 6 of 15 elevated
(40%)
Lactate
In the prelim evaluation of Dr. Kelley’s data 12/36 (25%) of autistic children have elevated alanine/lysine
Mitochondria Corner Piece of the Puzzle??
Can Autism Be A Mitochondrial Disease? Clinical Convergent Evidence 1
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3+ systems involved, fluctuating symptoms, intolerance to fasting/dietary changes Nervous system, muscle, gut, immune system involvement—most energy dependent tissues Response to carbohydrate exclusive diets (GCFC, ketogenic, specific carbohydrate) High heritability by family history with near failure of classic Mendelian genetics to explain Spectrum of severity
Can Autism Be A Mitochondrial Disease? Biochemical Convergent Evidence environmental precipitants may 2 Proposed
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selectively injury metabolically susceptible individuals. Data analogous to Parkinson’s disease research. Environmental/Epigenetic toxins act via mitochondrial mechanism Other non-mitochondrial genetic lesions which increase oxidative stress increase ASD risk
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GSTP1*A haplotype Williams, T.A., et al., Risk of autistic disorder in affected offspring of mothers with a glutathione S-transferase P1 haplotype. Arch Pediatr Adolesc Med, 2007. 161(4): p. 356-61. James, S.J., et al., Metabolic endophenotype and related genotypes are associated with oxidative stress in children with autism. Am J Med Genet B Neuropsychiatr Genet, 2006. 141(8): p. 947-56.
Can Autism Be A Mitochondrial Disease? Divergent Evidence Multiple mitochondrial lesions appear to produce an ASD phenotype
Divergent Evidence
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15q inverted duplication Filipek, P.A., et al., Mitochondrial dysfunction in autistic patients with 15q inverted duplication. Ann Neurol, 2003. 53(6): p. 8014. PRADER WILLI TYPE MUTATION A3243G mtDNA mutation and mtDNA depletion. Pons, R., et al., Mitochondrial DNA abnormalities and autistic spectrum disorders. J Pediatr, 2004. 144(1): p. 81-5. MIDD MELAS MUTATION mitochondrial DNA G8363A transfer RNA(Lys) mutation. Graf, W.D., et al., Autism associated with the mitochondrial DNA G8363A transfer RNA(Lys) mutation. J Child Neurol, 2000. 15(6): p. 357-61. MERRF, LEIGH, CARDIOMYOPATHY, ATAXIA LIPOMA SYNDROME Rett Syndrome MECP2 knockout. Kriaucionis, S., et al., Gene expression analysis exposes mitochondrial abnormalities in a mouse model of Rett syndrome. Mol Cell Biol, 2006. 26(13): p. 5033-42. RETT SYNDROME
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Divergent Evidence
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Filipek, P.A., et al., Relative carnitine deficiency in autism. J Autism Dev Disord, 2004. 34(6): p. 615-23. NONSPECIFIC MITO DYSFUNCTION Poling, J.S., et al., Developmental regression and mitochondrial dysfunction in a child with autism. NONSPECIFIC MITO DYSFUNCTION J Child Neurol, 2006. 21(2): p. 170-2. Tsao, C.Y. and J.R. Mendell, Autistic disorder in 2 children with mitochondrial disorders. J Child Neurol, 2007. 22(9): p. 1121-3. CO Q10 DEFICIENCY AND THE OTHER NONSPECIFIC RC DYSFUNCTION II/III & IV
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Mitochondrial Autism —Immediate Clinical Research Priorities 1
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Sib studies—biomarkers, growth characteristics, phenotypic spectrum Are biochemical markers detectable at birth or shortly thereafter? If yes, what is inheritance pattern—doubt mtDNA? If no, when do biomarkers appear, and what is trigger or developmental biochemical pathway maturation cycle?
Mitochondrial Autism— Immediate Clinical Research Priorities 2
Longitudinal case studies/high risk  Biochemical markers vs. time  Muscle biopsy, skin, leukocytes  Clinical correlations with regressions
Study that should be done STAT
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Proposed selection criteria for Genome wide DNA microarray analysis (NB ‘mito autism’ may not be good enough endophenotype) Family with 2+ offspring on ASD spectrum Biochemical fingerprint markers positive— fasting PAA with inc alanine/lysine, increased fasting lactate, increased AST with nL ALT One pt with regressive autism associated with growth failure. Motor findings also present including hypotonia and weakness
Mitochondrial Autism— Immediate Clinical Research Priorities 3
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Treatment trials—dietary manipulation, immune challenge avoidance, fever treatment, rescue therapy trials Cybrid mitochondrial platelet studies—determines contribution of mtDNA to disorder
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1. Brady, M.T., Immunization recommendations for children with metabolic disorders: more data would help. Pediatrics, 2006. 118(2): p. 810-3. 2. Kingsley, J.D., et al., Immunizations for patients with metabolic disorders. Pediatrics, 2006. 118(2): p. e460-70. 3. Yang, Y., et al., Acute metabolic crisis induced by vaccination in seven Chinese patients. Pediatr Neurol, 2006. 35(2): p. 114-8.
Environmental exposures—pollutants, ecological studies, vaccination history, infection history, nutritional variables Mitochondrial/Metabolic Disorders Vaccination registry to systematically study susceptible subpopulations who may need alternative schedule. There are no safety studies to date on at risk populations.
Mitochondrial Autism— Epidemiology & Population Future Studies
Concession—Dr. Frye
Prior Epidemiology— Evidence of Absence is not Absence of Evidence
Study  Estimated statistical power of the largest population based study by Madsen et al. refuting the association between Autism and vaccines.  The effect size and power are calculated for four different proposed percentages of the Autism population at risk for vaccine associated regressive Autism.  Two difference population prevalences are used: the actual population prevalence of the Danish study and the current estimated population prevalence in the U.S.
Power Analysis
Percent of 1:1273 Prevalence 1:150 Prevalence Autism PopulatioEffect Size Power Effect Size Power n
7 5 3 1
0.0020 0.0014 0.0009 0.0003
24.1% 13.8% 8.4% 5.4%
0.0059 0.0041 0.0025 0.0008
97.9% 77.4% 35.7% 7.7%