Study Reveals Link Between Starch Digestion Gene and Intestinal Bacteria

A newly discovered relationship between genetic variation and the gut microbiome could help nutritionists customize their recommendations.

People with a large number of copies of a gene called AMY1, which expresses a salivary enzyme for starch decomposition, were strongly correlated to a certain profile of intestinal and oral bacteria, according to a new study by Cornell University.

A family of bacteria called Ruminococcaceae proliferates in the intestines when more of this salivary enzyme – called amylase – is available. Bacteria are known to break down resistant starch so that it can be digested, which human amylases can not do. The degradation of these difficult-to-digest starches offers nutritional benefits.

In the prehistoric era and afterwards, people with more copies of this gene could have benefited when calories were scarce, for example during cold seasons and famines.

"This will likely bring an extra supply of starch," said Angela Poole, assistant professor in the Division of Nutritional Sciences and senior author of a study published April 10 in the journal Cell Host & Microbe.

Ruth Ley, director of the Max Planck Institute for Developmental Biology in Germany and previously Cornell's Department of Molecular Biology and Genetics, is the lead author of the study.

The findings suggest the need for personalized nutrition, said Poole, in which health care professionals could take into account the number of copies of the patient's AMY1 gene when providing dietary advice. Other researchers have linked the gene to the glucose response to meals, insulin resistance, and body mass index.

In addition, higher copy numbers of the AMY1 gene were also correlated with higher levels of Porphyromonas, a mouth-associated bacterium associated with gum disease periodontitis, although additional studies are needed to distinguish the cause. or coincidence.

In this study, Poole and his colleagues examined existing data on genetic and stool samples from a British population close to 1,000 people. They were looking for evidence of the possible influence of the copy number of the AMY1 gene on the microbiome; they examined the results of a subset of 100 people from the British population, 50 with a projected high copy number (5% higher) and 50 with a low copy number (5% lower).

"High [AMY1 gene] number of copies correlated with a certain pattern of intestinal bacteria, "said Poole.

Poole then determined the number of AMY1 copies in more than 100 people in Ithaca, New York. She found a distribution between two and 30 copies. The team also collected stool data and identified bacteria associated with high and low copy numbers of the AMY1 gene.

Twenty-five of these study participants were then put on a standard diet for two weeks. "I wanted to make sure they were eating the same thing and that they were eating starch," Poole said. The team then collected saliva and stool samples and found that in the intestine the results matched those in the UK population study.