By Dr. Senay Simsek, Bert L. D’Appolonia Cereal Science and Technology of Wheat Endowed Associate Professor, North Dakota State University, Fargo, ND
With the global demand for wheat remaining quite strong, there is a continual need to develop new varieties that have resistance to the latest disease threats, as well as improved yield, agronomic and end-use qualities. The varieties available today are improved over historic varieties, yet their basic genetic structure is essentially unchanged. In the Northern U.S. Plains during the past century, there have been many improved wheat cultivars, including many public varieties developed by breeders at North Dakota State University (NDSU).
Those of us involved in wheat research, production and processing fully accept that flour from HRS and other wheat classes as well as semolina is healthy and very nutritious for the vast majority of people. However, this has not prevented opposing points of view, and serious attacks against food products that contain gluten.
Celiac disease is a real and serious autoimmune condition that has gained a lot of attention in the past few years. Reputable medical organizations have determined that celiac disease is prevalent in about 1 of every 100 people worldwide. However, the over-simplified explanation that “gluten causes celiac disease” has likely hurt the reputation of wheat and wheat foods. There is a subtle but significant difference that demonstrates gluten alone does not cause celiac disease and, as our study showed, that new wheat varieties are not responsible for increased cases of celiac.
The gluten in wheat, which is essential for the elastic texture of dough, is composed of two separate proteins: glutenin and gliadin. Glutenin and gliadin are divided into distinct compounds, which in turn are made up of specific peptides (compounds of two or more amino acids in a chain).
A genetic predisposition to celiac must exist in individuals before the presence of certain gliadin and glutenin peptides may trigger an immune response that results in damage to the lining of the small intestine. These peptides are therefore considered “immunogenic.” Previous studies have found that α-gliadin proteins in wheat have a high number of immunogenic peptides.
In many ways, simply blaming gluten for celiac has helped spark quite a bit of unwanted attention from bloggers, authors, doctors and others making claims that modern breeding practices have changed wheat protein chemistry. This has resulted in a higher concentration of immunogenic peptides in modern wheat in comparison to historical wheat varieties, and that this is a contributing factor towards increased incidence of celiac disease.
To test this hypothesis, we studied the protein chemistry of 30 HRS wheat cultivars released in North Dakota in the last century. The presence of celiac disease-initiating-peptides was determined using untargeted mass spectrometry, and the amount of these peptides was quantified using a targeted mass spectrometric approach. We collaborated with Dr. Steven Meinhardt from the NDSU Plant Pathology Department and graduate student Maneka Malalgoda worked with us as part of her master’s thesis project. This project was funded by growers through checkoff funds from the North Dakota Wheat Commission.
In the qualitative analysis, we determined the presence of 15 immunogenic peptides. We found that the presence of these peptides is not related to the release year of cultivars and that these peptides appear randomly. In our quantitative analysis, we specifically tracked two prominent immunogenic peptides, PFPQPQLPY (DQ-α-I/ glia-α9) and RPQQPYPQ (glia-α20), and total α-gliadin. The results supported our previous findings. That is, the amount of the peptides varied randomly across the years that were analyzed, and there is no correlation between release year and the number of immunogenic peptides or total α-gliadin.
Thus, overall, our results demonstrate that modern HRS wheat is not higher in terms of celiac disease immunogenicity in comparison to historical HRS varieties.
Our team plans to submit the complete study report to a peer reviewed journal in the future.
Editor’s Note: Capital Press has reported that a researcher is working with the Kansas Wheat Commission at the Heartland Plant Innovations Center in Manhattan, KS, toward a “celiac-safe” wheat. In theory, celiac-safe wheat would still contain the gluten proteins necessary for making bread, but would have none of the immunogenic peptides which trigger an immune response in people with the genetic predisposition for celiac disease, said Chris Miller, director of wheat quality research for Heartland Plant Innovations.
“I think the problem of celiac disease is so big that it won’t be solved by a single group of researchers,” Miller said. “If we can identify the underlying cause of celiac reactivity in the process, and we have the means to reduce it, we should be working towards those types of goals.”
