**Author details**

**3.6. N-Acetyl-L-Cysteine and glutathione**

108 Pharmacology and Nutritional Intervention in the Treatment of Disease

sue cysteine levels.

**Abbreviations**

VLCFA, very long chain fatty acids

and the Finnish Brain Research Foundation.

**Acknowledgements**

**4. Summary and conclusion**

to find out the efficiency of new types of interventions.

N-Acetyl-L-Cysteine (NAC) is an antioxidant that helps increase glutathione synthesis which, in turn, helps the body defends against harmful toxins. NAC is the acetyl derivative of L-cysteine. While L-cysteine plays important metabolic roles as a key antioxidant, a gluta‐ thione precursor and a natural source of sulfur for metabolism, it is unstable and can be‐ come degraded during absorption. NAC on the other hand, is more stable than L-cysteine. Taken orally, NAC converts into L-cysteine after being absorbed, and raises blood and tis‐

It is generally accepted that complex diseases such as autism is influenced by genetic altera‐ tions at multiple and variable sites that interact to reach a threshold of toxicity that triggers the disease expression. When expressed chronically even small variations in the gene ex‐ pression and enzyme activity caused by genetic changes and environmental factors could have a significant impact on downstream metabolism leading to development of autism. A metabolic imbalance can promote chronic oxidative stress and impaired methylation capaci‐ ty which results in alterations of normal developmental maturation of neurologic and im‐ munologic systems associated with autism. The production of free radicals is critical in the regulation of many biological functions, cellular damage, and the pathogenesis of disorders affecting central nervous system. Oxidative stress is shown to play a role in many neuro‐ psychiatric disorders, including ASD. Understanding of functional connections of autism-as‐ sociated genes and the impact of environmental risk factors on cellular responses linked to ASD phenotype will allow to distinguish disease-related pathological as well as compensa‐ tory processes and to identify targets for treatment of different features associated with ASD. The human genetic heterogeneity increases the complexity of the effects of environ‐ mental factors. New biomarkers are desired to support clinical trials which are the final way

ASD, autism spectrum disorders; FXS, Fragile X syndrome, GABA, gamma-aminobutyric acid; GSH, gamma-glutamylcysteinylglycine; IL-6, interleukin 6; NAC, N-Acetyl-L-Cysteine; PST, phenol sulfotransferase; ROS, reactive oxygen species; SOD, superoxide dismutases;

We thank for the grants from the Academy of Finland, the Arvo and Lea Ylppö Foundation,

Maija L. Castrén1,2, Tuomas Westermarck3 and Faik Atroshi4

1 Institute of Biomedicine/Physiology, University of Helsinki, Helsinki, Finland

2 Division of Child Neurology, Hospital for Children and Adolescents, Helsinki University Central Hospital, Helsinki, Finland

