Brain anatomy and development in autism: review of structural MRI studies

Autism is a neurodevelopmental disorder that severely disrupts social and cognitive functions. MRI is the method of choice for in vivo and non-invasively investigating human brain morphology in children and adolescents. The authors reviewed structural MRI studies that investigated structural brain anatomy and development in autistic patients. All original MRI research papers involving autistic patients, published from 1966 to May 2003, were reviewed in order to elucidate brain anatomy and development of autism and rated for completeness using a 12-item check-list. Increased total brain, parieto-temporal lobe, and cerebellar hemisphere volumes were the most replicated abnormalities in autism. Interestingly, recent findings suggested that the size of amygdala, hippocampus, and corpus callosum may also be abnormal. It is conceivable that abnormalities in neural network involving fronto-temporo-parietal cortex, limbic system, and cerebellum may underlie the pathophysiology of autism, and that such changes could result from abnormal brain development during early life. Nonetheless, available MRI studies were often conflicting and could have been limited by methodological issues. Future MRI investigations should include well-characterized groups of autistic and matched healthy individuals, while taking into consideration confounding factors such as IQ, and socioeconomic status

Increased serum levels of high mobility group box 1 protein in patients with autistic disorder

High mobility group box 1 (HMGB1) is a highly conserved, ubiquitous protein that functions as an activator for inducing the immune response and can be released from neurons after glutamate excitotoxicity. The objective of the present study was to measure serum levels of HMGB1 in patients with autistic disorder and to study their relationship with clinical characteristics. We enrolled 22 adult patients with autistic disorder (mean age: 28.1 ± 7.7 years) and 28 age- and gender-matched healthy controls (mean age: 28.7 ± 8.1 years). Serum levels of HMGB1 were measured by enzyme-linked immunosorbent assay (ELISA). Compared with healthy subjects, serum levels of HMGB1 were significantly higher in patients with autistic disorder (10.8 ± 2.6 ng/mL versus 5.6 ± 2.5 ng/mL, respectively, P < 0.001). After adjustment for potential confounders, serum HMGB1 levels were independently associated with their domain A scores in the Autism Diagnostic Interview-Revised, which reflects their impairments in social interaction. These results suggest that HMGB1 levels may be affected in autistic disorder. Increased HMGB1 may be a biological correlate of the impaired reciprocal social interactions in this neurodevelopmental disorder

Alterations of circulating endogenous secretory RAGE and S100A9 levels indicating dysfunction of the AGE-RAGE axis in autism

An excess accumulation of advanced glycation end products (AGEs) has been reported in autism brains. Through their interaction with their putative receptor RAGE, AGEs can promote neuroinflammation, oxidative stress and neuronal degeneration. To shed more light on the possible alterations of the AGEs-RAGE axis in autism, hereto we measured plasma levels of endogenous secretory RAGE (esRAGE) and its proinflammatory ligand S100A9 in 18 young adults with autistic spectrum disorder (ASD) and 18 age- and gender-matched healthy comparison subjects. The Childhood Autism Rating Scale (CARS) was used to assess the severity of autistic symptoms. Significantly reduced levels of esRAGE (P = 0.0023) and elevated concentrations of S100A9 (P = 0.0012) were found in ASD patients as compared to controls. In autistic patients, there was a statistically significant positive correlation between CARS scores and S100A9 levels (r = 0.49, P = 0.035), but no significant correlation was seen between esRAGE and S100A9 values (r = -0.23, P = 0.34). Our results of a significantly reduced peripheral level of esRAGE coupled with elevated S100A9 point to a subtle but definite dysfunction of the AGEs/RAGE axis in autism that could play a role in the pathophysiology of this disorder