House CallApr/May 2011 Issue

Research Roundup: Dirty Air, Working on Wheat, Asthma and More!

The latest medical news for people with allergies and food sensitivities

Dirty Air

Reports that air pollution may contribute to the earlier onset of type 1 diabetes led researchers at Northern Ontario School of Medicine to look into the possible link. The Canadian team studied the effects of two sources of particulate air pollution—urban air and diesel exhaust—in mice susceptible to type 1 diabetes, an autoimmune condition.

They found urban air exposure resulted in a trend toward earlier development of type 1 diabetes, as well as higher titers of insulin autoantibodies. Surprisingly, effects weren’t seen with diesel exhaust. Researchers suspected differences in the metal content between urban air and diesel exhaust may help explain their findings. To examine their theory, the team looked at a marker of metal toxicity, metallothionein, and found cells exposed to urban air expressed more metallothionein than those exposed to diesel exhaust.

“Our results suggest that air pollution exposure may be a factor in autoimmune disease development, although the type of pollution may be an important factor,” says lead investigator, Stacey Ritz PhD. This is an area that has not been well studied, she adds, and results are preliminary. The research team plans to try to replicate the findings and study the underlying mechanisms. The work was presented at the 2010 International Meeting of the American Thoracic Society.

In separate research published in Environmental Health Perspectives, a team at the Zilkha Neurogenetic Institute at the University of Southern California, linked autism to living within 300 meters (328 yards) of a freeway at the time of birth. Proximity to the freeway, which served as a marker for exposure to traffic-related air pollution, was associated with nearly twice the risk for autism. Living near other major roads was not associated with autism. Larger traffic volume and concentrations of pollutants observed near freeways may help account for the difference, researchers say.

Toxicological studies have suggested a possible role for air pollution in disrupting brain development and function during critical time points in gestation and early life. However, this study, which looked at more than 300 preschool-age children with autism and 250 control subjects living in California, is the first to show an association of autism with residential traffic proximity.

Little is known about the potential environmental contributors to autism but based on these preliminary findings, researchers say more studies are warranted.

Working on Wheat

Researchers are gaining ground on making wheat flour safe for celiacs. In a study published in Clinical Gastroenterology and Hepatology, a team at the University of Naples recently looked at the safety of a daily dose of hydrolyzed wheat flour in a small sample of individuals with celiac disease. Hydrolyzing generally refers to the breaking down of substances like proteins via a chemical process. Here wheat flour was fermented with sourdough lactobacilli and fungal proteases to decrease the concentration of gluten. Five adults with celiac disease then ate 200 grams of the fully hydrolyzed wheat in baked goods for 60 days. The participants reported no symptoms, had no increase in blood markers for celiac disease and no change in their small intestinal mucosa. The residual gluten concentration in the fully hydrolyzed baked goods was 8 parts per million (ppm); levels less than 20 ppm are generally considered safe for celiacs. “Not yet as good as conventional flour, the final baked goods were very palatable,” says lead investigator Luigi Greco, MD, PhD. Future studies involving more patients for longer time periods are planned.

In other research, a team from the University of Palermo recently studied a special line of wheat deficient in gliadin, the component of wheat toxic to celiacs. Using biopsy tissue samples from 19 celiacs on a gluten-free diet, researchers found that the height of intestinal cells, called enterocytes, didn’t appear to take a hit when exposed to the wheat. The findings suggest that manipulating the gliadin composition in wheat can affect the celiac response to wheat gluten. However, the tissue samples released more anti-tissue transglutaminase and other markers of immunologic reactivity than samples not exposed to the wheat. The study appeared in Digestive and Liver Diseases.

Bitter Taste of Asthma

A team from the University of Maryland School of Medicine recently stumbled upon a taste receptor that may lead to a treatment breakthrough for asthma suffers. The researchers were doing unrelated work on lung tissue when they came across the taste receptor—located in the lung.

Similar to a taste bud on the tongue, this lung-based taste receptor seems to respond to bitter substances, signaling constricted muscles in the lungs to relax and open in a matter of seconds. In laboratory studies, quinine and chloroquine, which are very bitter, as well as saccharin, which has a bitter aftertaste, opened airways more extensively than any known medication for asthma. In fact, the muscle relaxed so significantly that researchers initially worried the effect was due to damage to the muscle. This appears not to be the case.

Subsequent studies in a mouse model of asthma demonstrated that an aerosolized form of bitter compounds relaxed airways, pointing to the possibility of an effective new asthma treatment.

“New drugs to treat asthma, emphysema or chronic bronchitis are needed,” said lead investigator Stephen B. Liggett, MD, in a press release. “This could replace or enhance what is now in use and represents a completely new approach.”

Liggett cautions that eating bitter-tasting foods or compounds would not help in the treatment of asthma, explaining that therapeutic concentrations are unlikely to be achieved by mouth.

It’s unclear why humans have receptors in the lungs that respond to bitter substances. One theory is that taste receptors may play a disease-fighting role. Bitter secretions released by bacteria during respiratory infections like pneumonia may, in turn, help keep airways open, making it easier to cough and clear the lungs.

Researchers are now studying more than 10,000 bitter compounds to determine which may work best at opening airways. The research was published online in Nature Medicine.

Medical writer Christine Boyd lives in Baltimore.

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