Plausible etiology of brain dysconnectivity in autism – Review and prospectus

Role of Oligodendrocytes and Myelin in the Pathophysiology of Autism Spectrum Disorder

Autism Spectrum Disorder (ASD) is an early neurodevelopmental disorder that involves deficits in interpersonal communication, social interaction, and repetitive behaviors. Although ASD pathophysiology is still uncertain, alterations in the abnormal development of the frontal lobe, limbic areas, and putamen generate an imbalance between inhibition and excitation of neuronal activity. Interestingly, recent findings suggest that a disruption in neuronal connectivity is associated with neural alterations in white matter production and myelination in diverse brain regions of patients with ASD. This review is aimed to summarize the most recent evidence that supports the notion that abnormalities in the oligodendrocyte generation and axonal myelination in specific brain regions are involved in the pathophysiology of ASD. Fundamental molecular mediators of these pathological processes are also examined. Determining the role of alterations in oligodendrogenesis and myelination is a fundamental step to understand the pathophysiology of ASD and identify possible therapeutic targets.

The putative etiology and prevention of autism

Since the initial psychological report by Leo Kanner in 1943, relatively little formal biochemical/neurological research on the cause of autism, other than peripheral searches for genomic mutations, had been carried until the end of the 20th century. As a result of studies on twin sets and the conclusion that autism was largely a hereditary defect, numerous investigations have sought various genetic faults in particular. However, such studies were able to reveal a plausible etiology for this malady in only a small percentage of instances. Key bio-molecular characteristics of this syndrome have been uncovered when the potential roles of the glia were studied in depth. Findings related to biochemical deficiencies appearing early in the newborn, such as depressed IGF-1 (insulin-like growth factor #1) in neurogenesis/myelination, are becoming emphasized in many laboratories. Progress leading to timely diagnoses and subsequent prevention of central nervous system dysconnectivity now seems plausible. The tendency for an infant to develop autism may currently be determinable and preventable before irreversible psychosocial disturbances become established. These discussions about glial function will be inter-spersed with comments about their apparent relevance to autism. The concluding portion of this presentation will be a detailed review and summation of this diagnosis and prevention proposition.

COVID-19 and autism

The current pandemic of Covid-19 has created a paradigm for possibly gaining greater insight in two conditions:1)

Inflammatory maladies in pregnancy, and.

2)

The biology of IGF-1 in autism.

Studies since the beginning of this century have supported the view that IGF-1 deficiency in the neonate defines the basis of autism. As a result, it appears that interleukin-6 in corona virus-based infections causes reduced defenses because of suppressed IGF-1, especially in older patients. This may also portend an increase of autism in the offspring of gravidas currently affected severely by Covid-19.

The role of oligopeptides in preventing autism

Previous reports in this series point to insufficient insulin-like growth factor-1 (IGF1) in the newborn as the key to brain dysconnectivity characteristic of autism. Such a deficiency should be detectable in the baby's blood at or soon after birth. Breast-feeding exclusively for the first year of postpartum life or supplementation with oral agents to raise the serum IGF1 level, such a cyclo-glycylproline, could be helpful for this purpose.

Molecular biology of autism's etiology - An alternative mechanism

Autism is a neuropathologic condition believed to be the consequence of cerebral dysconnectivity. Hypomyelination of axons in brain nerve pathways parallels behavioral abnormalities characteristic of autism. The present discussion will examine the functional association of insulin-like growth factor-1 (IGF1) to neo-neuron myelination, especially in autistic children. These structural defects apparently correlate with a reduced level of circulating IGF. In addition, the potential connection of single nucleotide polymorphism to the etiology of autism is considered. Pharmaceutical and nutritional supplements that may enhance IGF1 to reduce the incidence of autism are proposed.

Prenatal identification of autism propensity

The innovative method described involves antepartum testing to determine if the fetus has the potential of later developing autism. A technique is detailed which allows examining the maternal blood for SNPs (single-nucleotide polymorphisms) known to be associated with IGF1/IRS1 cellular pathway malfunction potentially leading to brain dysconnectivity in neonates. Results can then be corroborated with umbilical cord sampling at birth by the Autism Index test. [The discussion presented here is the follow-up to the recent prior report: Steinman, G. IGF - Autism prevention/amelioration, Medical Hypotheses 2019;122:45-47].