Our ancestry determines our genetic makeup.

That includes everything from the color of our hair to the size of our feet to what types of diseases we are likely to develop.

With that knowledge doctors are likely to prescribe preventive measures or medication to ward off the chance of developing conditions such as high blood pressure or arteriosclerosis.

But a study released today sheds new light on the role that genes play in determining our susceptibility to illnesses, as well as the potential to fundamentally alter how we treat inherited diseases.

The report, published in the Cell & Host’s special issue, “Genetics and Epigenetics of Host-Microbe Interactions,” suggests that it’s not just the genes themselves that determine what diseases we contract but also how these genes regulate the gut bacteria that have connections to specific diseases.

“We set out to find out about human genes that are implicated in the regulation of the gut microbiome, and we found some that are,” Ruth Ley, Ph.D., an associate professor in the Department of Microbiology at Cornell University and the study’s senior author, said in a press release. “These microorganisms are environmentally acquired, but the genome also plays a part, by determining which microorganisms are more dominant than others.”

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A Study of Twins

Ley, who is also the director of the Department of Microbiome Science at the Max Plank Institute for Developmental Biology in Tubingen, Germany, and her team of researchers examined the gut microbiomes of more than 1,000 sets of twins who were part of the TwinsUK Study.

That research project analyzed the genomes of both fraternal and identical twins in order to ferret out a multitude of diseases and conditions.

The human microbiome is defined as all the microorganisms in our bodies. It consists of bacteria, viruses, and other microscopic organisms.

These microbes help us maintain good health through digestion and absorption. They also help to ward off disease.

A good example is Bifidobacterium, which the authors point to in their study. It’s associated with the digestion of lactose (milk sugar) in the large intestines.

But the amount of that bacterium in the human gut inverts with a person’s ability to digest dairy. In other words, high levels of Bifidobacterium mean a person can’t easily digest lactose, a condition known as lactose intolerance. Low levels means a person can digest dairy just fine.

However, the research models indicate that the LCT gene, which makes the enzyme lactase that causes the breakdown of lactose in the small intestines, may ultimately regulate the level of Bifidobacterium found in a person’s digestive track.

“People who can digest lactose express that lactase gene in the small intestines,” Emily Davenport, a postdoctoral fellow in the Department of Molecular Biology and Genetics at Cornell University and one of the study’s authors, told Healthline. “If we can’t break down the lactose it passes through to the large intestines and that’s where Bifidobacterium lives and they break it down.”

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Calming the Immune System

In addition to Bifidobacterium’s important probiotic properties, it has also shown to carry anti-inflammatory properties as well, according to Dr. Jonathan Braun, Ph.D., of UCLA Pathology and Laboratory Medicine, who spoke to Healthline about the study.

That means it can aid in the treatment of autoimmune diseases such as diabetes, multiple sclerosis, and colitis.

“Bifidobacterium, that one microorganism will quiet down your immune system,” he said.

It’s this network of other disorders connected to Bifidobacterium that makes the study truly intriguing, Braun added.

The implications of the research may ultimately lead to new treatments for autoimmune disorders, plus a host of other diseases that we inherit from our families.

Davenport said further research would eventually lead to personalized medicine. If people know they are predisposed to a certain disease such as pulmonary disease, it will be known that diet and exercise may not be enough and medication that can target a specific bacteria tied to the disease will come into play.

“It’s about understanding what is genetic and what is environmental that [will be] important for treatment,” she said.

Braun added that researchers would also have to pin down the “Rosetta Stone” of bacteria that are linked to our genes. Once that happens he expects to see doctors prescribing antibiotics to help fight certain diseases.

“I think in a few years we will see the first efforts,” Braun said.

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