Relative abundance of short chain and polyunsaturated fatty acids in propionic acid-induced autistic features in rat pups as potential markers in autism

Background: Fatty acids are essential dietary nutrients, and one of their important roles is providing polyunsaturated fatty acids (PUFAs) for the growth and function of nervous tissue. Short chain fatty acids (SCFAs) are a group of compounds derived from the host microbiome that were recently linked to effects on the gut, the brain, and behavior. They are therefore linked to neurodevelopmental disorders such as autism. Reduced levels of PUFAs are associated with impairments in cognitive and behavioral performance, which are particularly important during brain development. Recent studies suggest that omega -3 fatty acids such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are involved in neurogenesis, neurotransmission, and protection from oxidative stress. Omega-3 PUFAs mediate some of these effects by antagonizing Omega-6 PUFA (arachidonic acid, AA)-induced proinflammatory prostaglandin E-2 (PGE(2)) formation. Methods: In this work, the absolute and relative concentrations of propionic (PPA), butyric and acetic acids, as well as PUFAs and their precursors (alpha-Linolenic and linoleic), were measured in the brain tissue of PPA-neurointoxicated rat pups (receiving 250 mg PPA/Kg body weight for 3 consecutive days) as a rodent model with persistent autistic features compared with healthy controls. Results: The data revealed remarkably lower levels of omega6/omega3, alpha-Linolenic/Linoleic, alpha-Linolenic/EPA, alpha-Linolenic/DHA, EPA/DHA, and AA/Linoleic acid ratios in PPA-intoxicated rats. The role of these impaired ratios is discussed in relation to the activity of desaturases and elongases, which are the two enzymatic groups involved in the synthesis of PUFAs from their precursors. The relationship between the abnormal relative concentrations of the studied fatty acids and oxidative stress, neurotransmission, and neuroinflammation is also discussed in detail. Conclusions: This study demonstrates that fatty acid ratios are useful for understanding the mechanism of PPA neurotoxicity in a rodent model of autism. Therefore, it is possible to use these ratios for predictions in patients with this disorder.