![]() Indeed, a recent pyrosequencing analysis showed that gram-negative bacteria, Desulfovibrio and Bacteroides vulgatus, were detected at higher levels in autistic children. The down-regulated synthesis of glutathione may increase the vulnerability of children to ASD and other neurologic disorders, such as Friedreich’s Ataxia. A test in rats showed that prenatal LPS exposure decreased levels of glutathione, which is an important antioxidant involved in heavy metal detoxification in the brain. LPS-induced inflammation in the brain increases permeability of the blood-brain barrier and facilitates an accumulation of high levels of mercury in cerebrum, which may aggravate ASD symptoms. Many pathogenic gram-negative bacteria contain lipopolysaccharide (LPS) in their cell walls, which can cause damage in various tissues including the brain. Potential involvement of gut microbes in ASD etiology has been speculated for more than a decade. In addition, considering the potential interactions between intestinal microbes and the central nervous system, abnormal intestinal flora may be associated not only with GI problems but also with ASD-related behavioral symptoms. Several studies have reported an increased administration of oral antibiotics to autistic children during the first 3 years of life –, which may destabilize microbial community by eliminating beneficial bacteria and helping pathogenic bacteria colonize the intestinal walls. Up to 10 14 bacteria in human intestine balance the immune system, help digestion, produce vitamins, and promote GI motility. A large fraction of autistic children suffer from gastrointestinal (GI) problems, and a strong positive correlation was observed between GI problems and ASD severity. One potentially important environmental factor is abnormal intestinal flora. ![]() ASD patients and their families face difficulties in treatment due to a highly diverse etiology of ASD in which genetic and environmental factors are equally important, as implied by a large twin concordance study. There is a world-wide increase in the diagnosis of ASD, which has reached an epidemic level. Taken together, autism and accompanying GI symptoms were characterized by distinct and less diverse gut microbial compositions with lower levels of Prevotella, Coprococcus, and unclassified Veillonellaceae.Īutism Spectrum Disorders (ASD) are complex neurobiological disorders whose chief manifestations are qualitative impairment in social interaction and communication and restricted, repetitive, and stereotyped patterns of behavior, interests, and activities. ![]() However, multivariate analyses showed that autism-related changes in both overall diversity and individual genus abundances were correlated with the presence of autistic symptoms but not with their diet patterns. These are intriguingly versatile carbohydrate-degrading and/or fermenting bacteria, suggesting a potential influence of unusual diet patterns observed in autistic children. Further, rigorous statistical tests with multiple testing corrections showed significantly lower abundances of the genera Prevotella, Coprococcus, and unclassified Veillonellaceae in autistic samples. Unexpectedly, the presence of autistic symptoms, rather than the severity of GI symptoms, was associated with less diverse gut microbiomes. By pyrosequencing the V2/V3 regions in bacterial 16S rDNA from fecal DNA samples, we compared gut microbiomes of GI symptom-free neurotypical children with those of autistic children mostly presenting GI symptoms. We recruited 20 neurotypical and 20 autistic children accompanied by a survey of both autistic severity and GI symptoms. Therefore, here we aimed to define systemic changes in gut microbiome associated with autism and autism-related GI problems. However, microbiome-level studies on autism are limited and mostly focused on pathogenic bacteria. Increasing evidence from recent high-throughput sequencing analyses indicates that disturbances in composition and diversity of gut microbiome are associated with various disease conditions. ![]() High proportions of autistic children suffer from gastrointestinal (GI) disorders, implying a link between autism and abnormalities in gut microbial functions.
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