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Autism Research and Treatment
Volume 2013, Article ID 963697, 8 pages
http://dx.doi.org/10.1155/2013/963697
Review Article

Early Infant Exposure to Excess Multivitamin: A Risk Factor for Autism?

1Institute of Basic Medical Sciences, Medical College, Dalian University, Dalian 116622, China
2Section of Cell Signaling, Okazaki Institute for Integrative Bioscience, National Institutes of Natural Sciences, Okazaki 444-8787, Japan
3Department of Physiology, Institute of Basic Medical Sciences, China Medical University, Shenyang 110001, China
4Department of Neurology, Affiliated Zhongshan Hospital of Dalian University, Dalian 116001, China

Received 13 November 2012; Accepted 12 February 2013

Academic Editor: Herbert Roeyers

Copyright © 2013 Shi-Sheng Zhou et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Autism, a neurodevelopmental disorder that affects boys more than girls, is often associated with altered levels of monoamines (serotonin and catecholamines), especially elevated serotonin levels. The monoamines act as both neurotransmitters and signaling molecules in the gastrointestinal and immune systems. The evidence related to monoamine metabolism may be summarized as follows: (i) monoamine neurotransmitters are enzymatically degraded/inactivated by three mechanisms: oxidative deamination, methylation, and sulfation. The latter two are limited by the supply of methyl groups and sulfate, respectively. (ii) A decrease in methylation- and sulfation-mediated monoamine inactivation can be compensated by an increase in the oxidative deamination catalyzed by monoamine oxidase, an X-linked enzyme exhibiting higher activity in females than in males. (iii) Vitamins can, on one hand, facilitate the synthesis of monoamine neurotransmitters and, on the other hand, inhibit their inactivation by competing for methylation and sulfation. Therefore, we postulate that excess multivitamin feeding in early infancy, which has become very popular over the past few decades, may be a potential risk factor for disturbed monoamine metabolism. In this paper, we will focus on the relationship between excess multivitamin exposure and the inactivation/degradation of monoamine neurotransmitters and its possible role in the development of autism.