The current study demonstrated significantly high levels of AMA-M2 in autistic subjects when compared with healthy controls. Further large-scale studies are required to dissect any pathogenic role of these antibodies in the development of autism.
Diseases of the mitochondria that appear to cause the most damage are ones affecting cells of the brain, heart, liver, skeletal muscles, kidney and the endocrine and respiratory systems.
Higher oxidative stress in cells of children with autism was evidenced by higher rates of mitochondrial reactive oxygen species production (1.6-fold), higher mitochondrial DNA copy number per cell (1.5-fold), and increased deletions. Mitochondrial dysfunction in children with autism was accompanied by a lower (26% of TD children) oxidative burst by PMA-stimulated reduced nicotinamide-adenine dinucleotide phosphate (NADPH) oxidase and by a lower gene expression (45% of TD children's mean values) of the nuclear factor erythroid 2–related factor 2 transcription factor involved in the antioxidant response. Given that the majority of granulocytes of children with autism exhibited defects in oxidative phosphorylation, immune response, and antioxidant defense, our results support the concept that immunity and response to oxidative stress may be regulated by basic mitochondrial functions as part of an integrated metabolic network.
Perhaps it’s presumptive of me to say this – but of course there are links between mitochondrial dysfunction and autism! Autism is a multi-symptom chronic disease that primarily affects the brain. All mitochondrial dysfunction related diseases are chronic multi-symptom illnesses, and brain cells are dense with mitochondria, so mitochondrial dysfunction should be at the top of the list of possible causes. Apparently, though, it is not.
This study suggests that a significant subgroup of AD children may have alterations in mitochondrial function which could render them more vulnerable to a pro-oxidant microenvironment derived from intrinsic and extrinsic sources of ROS such as immune activation and pro-oxidant environmental toxicants. These findings are consistent with the notion that AD is caused by a combination of genetic and environmental factors.
In vivo brain findings provide evidence for a possible neurobiological subtype of mitochondrial dysfunction in ASD.
The ratios of mtDNA of three mitochondrial genes ND1, ND4 and Cyt B (that encode for subunits of complexes I and III) to nuclear DNA were significantly increased in autism, suggesting a higher mtDNA copy number in autism. Compared with the 95% CI of the control group, 44% of autistic children showed higher copy numbers of all three mitochondrial genes examined. Furthermore, ND4 and Cyt B deletions were observed in 44% and 33% of autistic children, respectively. This study indicates that autism is associated with mitochondrial dysfunction in the brain.
The etiology of this developmental disorder is poorly understood, and no biomarkers have been identified. Identification of novel biochemical markers related to autism would be advantageous for earlier clinical diagnosis and intervention. Studies suggest that oxidative stress-induced mechanisms and reduced antioxidant defense, mitochondrial dysfunction, and impaired energy metabolism (NAD(+), NADH, ATP, pyruvate, and lactate), are major causes of ASD. This review provides renewed insight regarding current autism research related to oxidative stress, mitochondrial dysfunction, and altered tryptophan metabolism in ASD.
It is a multifactorial disorder resulting from interactions between genetic, environmental and immunological factors. Excitotoxicity and oxidative stress are potential mechanisms, which are likely to serve as a converging point to these risk factors. Substantial evidence suggests that excitotoxicity, oxidative stress and impaired mitochondrial function are the leading cause of neuronal dysfunction in autistic patients. Glutamate is the primary excitatory neurotransmitter produced in the CNS, and overactivity of glutamate and its receptors leads to excitotoxicity. The over excitatory action of glutamate, and the glutamatergic receptors NMDA and AMPA, leads to activation of enzymes that damage cellular structure, membrane permeability and electrochemical gradients. The role of excitotoxicity and the mechanism behind its action in autistic subjects is delineated in this review.
The co-occurrence of autism and mt disease is much higher than these figures, suggesting a possible pathogenetic relationship. Such hypothesis was initially suggested by the presence of biochemical markers of abnormal mt metabolic function in patients with ASD, including elevation of lactate, pyruvate, or alanine levels in blood, cerebrospinal fluid, or brain; carnitine level in plasma; and level of organic acids in urine, and by demonstrating impaired mt fatty acid β-oxidation. More recently, mtDNA genetic mutations or deletions or mutations of nuclear genes regulating mt function have been associated with ASD in patients or in neuropathologic studies on the brains of patients with autism. In addition, the presence of dysfunction of the complexes of the mt respiratory chain or electron transport chain, indicating abnormal oxidative phosphorylation, has been reported in patients with ASD and in the autopsy samples of brains. Possible pathogenetic mechanisms linking mt dysfunction and ASD include mt activation of the immune system, abnormal mt Ca(2+) handling, and mt-induced oxidative stress. Genetic and epigenetic regulation of brain development may also be disrupted by mt dysfunction, including mt-induced oxidative stress. The role of the purinergic system linking mt dysfunction and ASD is currently under investigation. In summary, there is genetic and biochemical evidence for a mitochondria (mt) role in the pathogenesis of ASD in a subset of children.
Autism spectrum disorders (ASDs) are caused by both genetic and environmental factors. Mitochondria act to connect genes and environment by regulating gene-encoded metabolic networks according to changes in the chemistry of the cell and its environment. Mitochondrial ATP and other metabolites are mitokines—signaling molecules made in mitochondria—that undergo regulated release from cells to communicate cellular health and danger to neighboring cells via purinergic signaling
This study suggests that different subgroups of children with ASD have different redox abnormalities, which may arise from different sources. A better understanding of the relationship between mitochondrial dysfunction in ASD and oxidative stress, along with other factors that may contribute to oxidative stress, will be critical to understanding how to guide treatment and management of ASD children. This study also suggests that it is important to identify ASD/MD children as they may respond differently to specific treatments because of their specific metabolic profile
Autism spectrum disorder (ASD) has been associated with mitochondiral disease (MD). Interestingly, most individuals with ASD and MD do not have a specific genetic mutation to explain the MD, raising the possibility of that MD may be acquired, at least in a subgroup of children with ASD... These data suggest that there are similar pathological processes between a subset of ASD children and an animal model of ASD with acquired mitochondrial dysfunction. Future studies need to identify additional parallels between the PPA rodent model of ASD and this subset of ASD individuals with this unique pattern of acyl-carnitine abnormalities. A better understanding of this animal model and subset of children with ASD should lead to better insight in mechanisms behind environmentally induced ASD pathophysiology and should provide guidance for developing preventive and symptomatic treatments.
This study demonstrates that multiple biomarkers of mitochondrial dysfunction are elevated in a significant portion of children with autism spectrum disorder and lend support to the notion that disorders of energy production may affect a significant subset of children with autism.
We find that ethylmercury not only inhibits mitochondrial respiration leading to a drop in the steady state membrane potential, but also concurrent with these phenomena increases the formation of superoxide, hydrogen peroxide, and Fenton/Haber-Weiss generated hydroxyl radical
Mitochondria, which are present in every cell of the body except red blood cells, are responsible for creating more than 90% of the energy needed by the body to sustain life and support growth. The failure of mitochondria can cause children to lose motor control, suffer from pain and weakness, have gastro-intestinal problems, swallowing difficulties, heart problems, liver disease, diabetes, developmental delays and other complications.
Reduced mitochondrial enzyme function proved widespread among the autistic children. Eighty percent had lowered activity in NADH oxidase than did controls, while 60 percent, 40 percent and 30 percent had low activity in succinate oxidase, ATPase and cytochrome c oxidase, respectively. The researchers went on to isolate the origins of these defects by assessing the activity of each of the five enzyme complexes involved in mitochondrial respiration. Complex I was the site of the most common deficiency, found in 60 percent of autistic subjects, and occurred five out of six times in combination with Complex V. Other children had problems in Complexes III and IV.
Levels of pyruvate, the raw material mitochondria transform into cellular energy, also were elevated in the blood plasma of autistic children. This suggests the mitochondria of children with autism are unable to process pyruvate fast enough to keep up with the demand for energy, pointing to a novel deficiency at the level of an enzyme named pyruvate dehydrogenase.
These data suggest that further metabolic evaluation is indicated in autistic patients and that defects of oxidative phosphorylation might be prevalent