Islamabad - A new study may have found a way to isolate genetics from environmental contributors to the disease, allowing researchers to focus on the link between heavy metal levels and autism risk. The new research was led by Manish Arora, PhD, an environmental scientist and dentist at the Icahn School of Medicine at Mount Sinai in New York City, NY.

For instance, such studies have had to approximate the toxic metal exposure based on the metal concentrations in the bloodstream. However, this estimation was done after the children had already been diagnosed with ASD, rather than before.

Additionally, some of these studies were unable to account for genetic factors that may have influenced the results; generally, separating environmental factors from genetic ones in the development of autism is challenging for researchers.

The method used in this new study, however, manages to bypass many of these limitations. By looking at naturally shed baby teeth, the researchers explain, they have access to information that goes as far back as a baby’s prenatal life. And by studying twins, Prof Arora and colleagues were able to separate genetic influences from environmental ones.

To determine how much metal the babies’ bodies contained before and after birth, the researchers used lasers to analyse the growth rings on the babies’ teeth.

Laser technology allowed the scientists to accurately extract specific layers of dentine, which is the substance that lies beneath the tooth enamel. In much the same way that we can tell the age of a tree by looking at the growth rings in a cross-section of its trunk, the scientists were able to see different developmental stages correspond to different rings by looking at a cross-section of the babies’ teeth.

This correspondence between growth dentine layers, their levels of lead, and the exposure to lead during different developmental stages, has been previously demonstrated by Prof Arora and team in research they carried out previously.

Cindy Lawler, PhD, head of the National Institute of Environmental Health Sciences (NIEHS) Genes, Environment, and Health Branch, explains the importance of using this scientific method for studying autism:

“We think autism begins very early, most likely in the womb, and research suggests that our environment can increase a child’s risk. But by the time children are diagnosed at age 3 or 4, it’s hard to go back and know what the moms were exposed to. With baby teeth, we can actually do that.” The study revealed that children with ASD had much higher levels of lead throughout their development.

The greatest difference between lead levels in children with ASD and children without was noticed during the period after birth.

Zinc levels, on the other hand, displayed a more complex pattern. During the prenatal period, children with ASD had lower levels of zinc, but after birth, these levels increased to higher levels than those found in children without ASD.

Finally, manganese was found to correlate with ASD as well. Children with ASD seemed to have less manganese than children without, both pre- and postnatally.

Overall, the study suggests that either prenatal exposure to heavy metals, or the body’s ability to process them, may influence the chances of developing autism.

“A lot of studies have compared current lead levels in kids that are already diagnosed,” Lawler says. “[But] being able to measure something the children were exposed to long before diagnosis is a major advantage.”

David Balshaw, PhD, head of the NIEHS Exposure, Response, and Technology Branch, also weighs in on the scientific method used for this study, saying, “There is growing excitement about the potential of baby teeth as a rich record of a child’s early life exposure to both helpful and harmful factors in the environment.”

Prof Arora called the method ‘a window into our fetal life’. He and his colleagues’ note, however, that more large-scale studies are needed to replicate and confirm their findings. Meanwhile, researchers are working on ways to allow for earlier diagnosis of gliomas, the most common form of brain cancer. New research looking at the links between brain cancer and the immune system may soon make it possible to detect these cancers much earlier.

Experts say these tumors “result in more years of life lost” than any other tumors. Symptoms associated with glioma vary depending on the position of the tumor, but they often include headache, confusion, memory and balance problems, personality changes, and difficulties with speech. Because the symptoms vary from individual to individual and are similar to those of other conditions, diagnoses of gliomas often come too late. On average, a diagnosis is made around three months after the onset of symptoms. The study focuses on the relationship between chemical signals from the immune system and the development of brain cancer. Judith Schwartzbaum, an associate professor of epidemiology and a member of The Ohio State University’s Comprehensive Cancer Centre, headed up the study.

“It’s important to identify the early stages of tumor development if we hope to intervene more effectively,” said Schwartzbaum. “If you understand those early steps, maybe you can design treatments to block further tumor growth.”

Studies have shown that brain cancer risk is lower in people with higher levels of immunoglobulin E – a protein released by the immune system during an allergic reaction – in the blood.

Because of this link, Schwartzbaum and her team were particularly interested in cytokines, which are immune proteins that communicate with other cells and help to orchestrate the immune response.

Schwartzbaum explains, “There was a clear weakening of those interactions in the group who developed brain cancer, and it’s possible this plays a role in tumor growth and development.”

These changes could be measured five years before the formation of the brain tumor.

The role of cytokines in cancer is, to date, poorly understood.

In some circumstances, they can help to fight tumor growth, but in others cytokines assist the growth of a tumor by suppressing the immune system.

In the current study, the researchers found a number of specific cytokines that appear to play a particularly significant role in the formation of gliomas. These chemicals will be explored in further studies.

Although a routine blood test for brain cancer will not be a practical solution that could be rolled out across the population, the findings are important. Catching tumors earlier in their progression means that treatment is more likely to be successful.

These results might also have a wider-ranging importance, as Schwarzbaum adds, “It’s possible this could also happen with other tumors –this is a general sign of tumor development.”

Further work will be needed to sure up the discoveries, but they mark another interesting milestone in the slow war of attrition against cancer of all types.