Glucose metabolism boosted by whole grain consumption, study finds

09 Oct 2018 --- A high intake of whole grains has been found to increase the levels of betaine compounds in the body which, in turn, is associated with improved glucose metabolism, a University of Eastern Finland study has found. The study sheds light on the cell level effects of a whole grain-rich diet, and thereby help in the development of increasingly healthy food products. 

“Whole grains are one of the healthiest foods there is. For instance, we know that a high intake of whole grains protects against Type 2 diabetes and cardiovascular diseases. Up until now, however, we haven't understood the cellular mechanisms through which a whole grain-rich diet impacts our body,” says Dr. Kati Hanhineva, Principal Investigator of the study at the University of Eastern Finland.

This study may be the first to identify the link between glucose metabolism and increased betaines, Olli Kärkkäinen from the University of Eastern Finland tells NutritionInsight. However, he points out that “we only show a correlation between some of the betainized compounds and glucose metabolism. Further studies are needed to show if this link is causal or mediated by some other still unknown factor.”

Using metabolomics analysis, Dr. Hanhineva's research group investigated the effects of a whole grain-rich diet on the body's metabolites. The effects were studied in mice fed with bran-rich fodder, and in humans following a diet rich in whole grain products over the course of 12 weeks. A whole grain-rich diet increased the levels of betaine compounds in both mice and humans.

“This is the first time many of these betaine compounds were observed in the human body in the first place,” says Dr. Hanhineva.

At the end of the 12-week follow-up, the researchers also observed a correlation between improved glucose metabolism and increased presence of betaine compounds in the body.

“Pipecolic acid betaine, for example, is particularly interesting. Increased levels of pipecolic acid betaine after the consumption of whole grains was, among other things, associated with lower post-meal glucose levels,” she adds.

New compound worked similarly to a heart drug in cell level experiments
One of the betaine compounds discovered by the researchers is 5-aminovaleric acid betaine, 5-AVAB, which seems to cumulate in metabolically active tissues, such as the heart. With this observation in mind, the researchers set out to further test its effects in a cell model.

“We observed that 5-AVAB reduces cardiomyocytes' use of fatty acids as a source of energy by inhibiting the function of a certain cell membrane protein,” says Kärkkäinen.

“This cell-level effect is similar to that of certain drugs used for cardiovascular diseases. However, it is important to keep in mind that we haven't proceeded beyond cell level experiments yet. We need further research in animals and humans to verify that 5-AVAB really can impact the function of our body,” he adds.

However, the discovery of the new compounds associated with whole grains significantly enhances our understanding of why whole grain products are good for our health.

“In the future, we seek to analyze in greater detail the multitude of effects these new compounds can have on the human body. We will also look into how intestinal microbes possibly contribute to the formation of these compounds,” Dr. Hanhineva continues.

How could the food industry use this information?
Speaking to NutritionInsight, Kärkkäinen suggests that the food industry could use these findings to further develop healthful foods. For example, “industry could conduct research on which raw material or food items contain different betaines, and which different types of food increase levels of betainized compounds in the body. For example, which types of whole grains increase different types of betainized compounds more than others.”

“In our study, we show that in mice the rye bran and wheat aleurone do increase different types of betainized compound. Rye bran increased pipecolic acid betaine more, whereas wheat aleurone increased valine betaine more,” he explains.

“Moreover, it is still unknown how food processing (e.g. microbial fermentation) or differences in the microbiota of a person affect the levels of betainized compounds. It seems likely that at least part of the betainized compounds measured in the body are made by microbes, since many of these compounds have previously been described in some microbial species.”

By Laxmi Haigh