The Causes of Autism

Who are the lovely authors, what’s the full title of the study, what journal was it published in, and when was the study published?

Authors

Mohammad H. Rahbar, Maureen Samms-Vaughan, Sepideh Saroukhani, Jan Bressler, Manouchehr Hessabi, Megan L. Grove, Sydonnie Shakspeare-Pellington , Katherine A. Loveland, Compton Beecher, and Wayne McLaughlin.

Title

Associations of Metabolic Genes (GSTT1, GSTP1, GSTM1) and Blood Mercury Concentrations Differ in Jamaican Children with and without Autism Spectrum Disorder.

Journal

International Journal of Environmental Research and Public Health, 2021 Feb; 18(4): 1377.

What is the study about?

This research aims to shed light on the potential environmental factors and genetic associations with autism in Jamaican children. The study explores the effects of exposure to heavy metals, including mercury, and the influence of three GST genes (GSTP1, GSTT1, and GSTM1) on autism. The study also aims to analyze the differences in socio-demographic characteristics and food consumption patterns between ASD cases and TD control groups. By examining these factors, this study provides valuable insights into the potential causes of autism and can help guide future research and interventions.

Is there any background research that led to this study?

This study builds on previous research examining a potential link between exposure to mercury and autism spectrum disorder (ASD). Prior studies have measured mercury levels in hair, urine, red blood cells, whole blood, and baby teeth. A meta-analysis found that while individuals with ASD had significantly higher mercury concentrations in whole blood and red blood cells compared to TD controls, the mercury level in hair was significantly lower in ASD cases than TD controls.

However, few studies had data on food consumption, including fish and seafood, and only three studies controlled for the confounding effects of food consumption and sociodemographic characteristics. These studies consistently reported no significant difference in blood mercury concentrations between ASD cases and TD controls after controlling for these factors.

What were the methods?

In this study, researchers collected whole blood samples (4-5 mL) from 266 Jamaican children with autism spectrum disorder (ASD) and their 1:1 age (±6 months) and sex-matched typically developing (TD) controls to measure exposure to heavy metals, including mercury (Hg), and determine GST gene genotypes. Using conditional logistic regression (CLR) models, they compared the distributions of socio-demographic characteristics and food consumption between the ASD and TD groups. We also used CLRs to investigate possible associations between various exposure variables, including GST genotypes (GSTP1, GSTT1, and GSTM1), and ASD status.

How were mercury levels assessed?

In this study, researchers measured mercury (Hg) levels in the blood samples of Jamaican children with autism and their matched TD controls. The samples were analyzed for Hg concentrations by the Trace Metals Lab at the Michigan Department of Health and Human Services (MDHHS) using a PerkinElmer Elan DRC II inductively coupled plasma mass spectrometer. The MDHHS utilized a Quality Control (QC) program that included bovine blood spiked with known quantities of mercury to ensure accuracy. Different limits of detection (LoD) were reported for Hg in phases 1 & 2 of the ERAJ study.

How as the genetic analysis done?

The genetic analysis involved amplifying regions of the GSTM1 and GSTT1 genes in two independent TaqMan Copy Number Assay reactions, as well as assessing the GSTP1 Ile105Val polymorphism (rs1695) using the TaqMan Drug Metabolism SNP genotyping assay C_3217198_20. Univariable General Linear Models (GLMs) were used to investigate the potential role of the three GST genes, ASD status, sociodemographic characteristics, and food consumption in determining the levels of mercury (Hg) in the blood. The blood samples were analyzed using a PerkinElmer Elan DRC II inductively coupled plasma mass spectrometer at the Trace Metals Lab of the Michigan Department of Health and Human Services (MDHHS) in Lansing, Michigan, USA. The MDHHS QC program used bovine blood spiked with known quantities of mercury to control for mercury levels in the blood samples. Additionally, multivariable GLMs were used to assess two-way interactions between genotypes of the three GST genes in relation to blood Hg concentrations.

What were the findings?

In the study, researchers found that children with autism and the GSTP1 Ile105Val genotype Ile/Ile had significantly higher levels of blood mercury compared to those with the Ile/Val genotype. This was after accounting for factors such as the interaction between GSTT1 and GSTP1, socioeconomic status, and consumption of leafy vegetables, fried plantain, and canned fish (sardine or mackerel fish).

Researchers also found that the geometric mean blood mercury concentration in TD control children with the Ile/Val genotype was significantly higher than those with the Ile/Ile genotype or the Val/Val genotype.

What were the conclusions from the study?

The study’s findings suggest that the GSTP1 gene may play a role in detoxifying mercury in the blood and interact with autism status.

However, the study does not imply that mercury exposure causes autism.

Instead, it suggests that certain subsets of children with autism and specific genotypes may be more vulnerable to neurodevelopmental impairment from exposure to mercury. Overall, the study highlights the importance of understanding the role of genetic and environmental factors in neurodevelopmental disorders like autism.

What were the limitations of the study?

This study has some limitations, including the absence of data on the frequency of fish and seafood consumption, and the potential confounding impact of dietary practices, such as fish intake, as well as other sources of Hg exposure and sociodemographic characteristics, on the connection between Hg concentrations in various tissues and ASD.

What should future research look into after these findings?

Future research should aim to replicate the results of this study in other populations and further investigate the interactive association between GSTP1 and ASD status in relation to blood Hg concentrations. Additionally, there is a need for further research to explore the role of dietary and environmental factors in moderating exposure to Hg in Jamaican children, especially among those who are more vulnerable to the adverse outcomes of Hg exposures due to their genetic variants.

Can I read the full study somewhere?

Of course. Right herrrrrr.