BackgroundThere is evidence that impaired metabolism play an important role in the etiology of many neuropsychiatric disorders. Although this has not been investigated to date, several recent studies proposed that nitrogen metabolism-related parameters may have a pathophysiological role in autism.MethodsThe study enrolled 20 Saudi boys with autism aged 4 to 12 years and 20 healthy controls matched for age and gender. Levels of creatine, urea, ammonia, gamma-aminobutyric acid (GABA), glutamate:glutamine (Glu:Gln) ratio, and enzymatic activities of glutamate dehydrogenase, 5'-nucleotidase, and adenosine deaminase (ADA) were determined in plasma samples from both groups.ResultsWe found a significant elevation of creatine, 5'-nucleotidase, GABA, and glutamic acid and a significant decrease in the enzymatic activity of ADA and glutamine level in patients with autism compared with healthy controls. The most significant variation between the two groups was found in the Glu:Gln ratio.ConclusionA raised Glu:Gln ratio together with positive correlations in creatine, GABA, and 5'-nucleotidase levels could contribute to the pathophysiology of autism, and might be useful diagnostic markers. The mechanism through which these parameters might be related to autism is discussed in detail.

Autism spectrum disorders are complex developmental disorders with increasing incidence and poorly understood etiology. Imbalance of amino acids profoundly influences brain function, and is thought to be one of the key players in the pathophysiology of autism. This study aimed to measure the plasma amino acid profiles of 20 Egyptian and 20 Saudi autistic patients in comparison to matching healthy controls to clarify the role of impaired amino acid concentrations in the etiology of autism. Plasma amino acids profiles were measured using high performance liquid chromatography. While plasma levels of glutamic, aspartic, and glycine recorded the most significant percentage elevated amino acids, glutamine, asparagine, arginine, tyrosine and isoleucine recorded the most remarkable percentage decrease in autistic patients from both populations compared to controls. Among the calculated relative values, only acidic/basic, and glutamate/glutamine ratios were significantly higher in autistics compared to controls. Non-essential/essential and glucogenic/ketogenic ratios were unaltered in autistics compared to controls. Increased plasma glutamate/glutamine ratio, together with increased glycine, arginine, aspartate, aspargine levels, and acidic/basic amino acid ratio can serve as a predictive tools for the early detection of autism. These findings suggest that glutamatergic abnormalities in the brain may be associated with the pathobiology of autism.