Publications and Research

Porphyrins Confirmed as Biomarkers of Mercury Toxicity in Autism

Profiles of porphyrins metabolites have enjoyed a surge in popularity in light of recent endorsement and adoption of the test as the preferred means for heavy metal and in particular, mercury assessment by the popular Walsh Research Institute or as it was previously known, the Pfeiffer Treatment Centre.

The decision as to the best test for assessing heavy metal toxicity such as mercury has traditionally been guided by two schools of thought with respect to autism. The first rests on the hypothesis that autism results in part from increased exposure to mercury at key times in development even providing the individual does not have inherent genetic or biochemical susceptibilities that impair their ability to detoxify mercury. The second school of thought reasons that if a fetus or infant exposed to mercury also had genetic and/or biochemical susceptibilities, which decrease their ability to detoxify mercury, a lesser level of mercury exposure may also lead to problems.

For these reasons, it is thought that hair elemental analysis, which is normally a good tissue for measuring heavy metal toxicity, may not provide a true assessment of heavy metal toxicity, given that a subset of individuals with ASD may not be able to excrete heavy metals efficiently through tissues such as hair. Therefore, a test which looks at the effect of heavy metal exposure on an intracellular pathway such as heme biosynthesis may represent a better alternative.

In keeping with this, researchers from Texas sought to combine markers from the porphyrins pathway with transsulfuration metabolites to examine their relationship with the severity of ASDs. Participants with severe ASDs had significantly increased mercury intoxication-associated urinary porphyrins (pentacarboxyporphyrin, precoproporphyrin, and coproporphyrin) in comparison to participants with mild ASDs, whereas other urinary porphyrins were similar in both groups. Significantly decreased plasma levels of reduced glutathione (GSH), cysteine, and sulfate in conjunction with significantly increased plasma oxidized glutathione (GSSG) were also observed among study participants relative to controls. Mercury intoxication associated urinary porphyrins were significantly correlated with increasing Childhood Autism Rating Scale scores and GSSG levels, whereas other urinary porphyrins did not show these relationships. The findings suggest that mercury intoxication is significantly associated with autistic symptoms, while the transsulfuration abnormalities confirmed that mercury intoxication was associated with increased oxidative stress and decreased detoxification capacity.

The findings of this study are very gratifying for practitioners who have been treating heavy metal toxicity in patients with autism with good clinical outcomes. The study also confirms the usefulness of assessing urinary porphyrins metabolites to provide an objective measure of mercury toxicity in individuals with ASDs.

Reference
Geier DA, et al, Biomarkers of environmental toxicity and susceptibility in autism, J Neurol Sci (2008), doi:10.1016/j. jns.2008.08.021