Bacterial Fats and not Just Dietary Fats Cause Heart Disease

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Highlights:

• Bacteroidetes, a type of bacteria found in the oral cavity and gastrointestinal tract synthesize lipids which have a different chemical structure and composition.
• The difference in the weight and chemical structure of the lipids in humans and the bacteria causes heart disease.
• The lipids which are released in the blood can easily pass through cell membranes.
• Immune cells detect the lipids from the bacteria as foreign bodies and trigger inflammation.

Fats that cause heart disease are not just from the diet. New evidence suggests that the bacteria in the mouth can also produce fats which can cause heart disease. For a long time, doctors assumed that the lipids which accumulate in the arteries which cause heart attack came from cholesterol-rich food. The sources of the fat, such as eggs, butter, fatty fish, and meat, don’t always develop heart disease. The reason behind it might be the new research finding.

Heart attacks result from a slow process of atherosclerosis which involves the hardening and clogging of the arteries with fatty substances called lipids. Immune cells that spot the lipids stick to the walls of blood vessels, scavenge lipids, and multiply. The walls of the blood vessel inflame and thicken due to the change in the smooth muscle cells lining them. The inflammation causes swelling and dividing to create plaques, clogs, and warty growths called atheromas.

The research team analyzed the atheromas from patients and found lipids with a chemical signature which are not present in animals. The lipids were from a specific family of bacteria.

Frank Nichols, a University of Connecticut (UConn) Health periodontist said, "I always call them greasy bugs because they make so much lipid. They are constantly shedding tiny blebs of lipids. Looks like bunches of grapes, on a bacterial scale.”

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Bacteroidetes That Make Fats Cause Heart Disease

Bacteroidetes are bacteria that make distinctive fats with unusual fatty acids with branched chains and odd numbers of carbons. Mammals, including humans don’t make either branched chain fatty acids or fatty acids with odd numbers of carbons.

Xudong Yao, a UConn associate professor of chemistry analyzed the lipid samples from the patients and said that the chemical differences between bacterial and human lipids result in subtle weight differences between the molecules.

"We used these weight differences and modern mass spectrometers to selectively measure the quantity of the bacterial lipids in human samples to link the lipids to atherosclerosis," he says. "Establishment of such a link is a first step to mark the lipids as indicators for early disease diagnosis."

The marked chemical differences between the human body’s native lipids and the Bacteroidetes lipids may be the reason they cause disease, suggests Nichols. The immune cells that initially stick to the blood vessel walls, initiating atherosclerosis recognize them as foreign and they initiate inflammation.

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Lipids From Bacteroidetes Can Initiate Inflammation

The research team also showed that despite being non-native lipids, the lipids of the bacteria could be broken down by an enzyme in the body. This can process lipids into a starting material to make inflammation-enhancing molecules.
So the Bacteroidetes lipids have a double effect on the blood vessels:

• First, the immune system sees them as a signal of bacterial invasion
• Second, the enzymes break them down and enhance the inflammation even more

Usually Bacteroidetes bacteria harbor in the mouth and does not infect the blood vessels. No matter where they are located, the lipids they produce pass easily through cell walls and into the bloodstream.

Further Research To Spot Lipid Accumulation

The next step in the research is to localize exactly where the bacterial lipids are accumulating. If the Bacteroidetes-specific lipids are accumulating within the atheroma, but not in the normal artery wall, it would be convincing evidence that these lipids are specifically associated with atheroma formation, and therefore contribute to heart disease.

Previous Evidence on Oral Health and Heart Diseases

• Streptococcus gordonii is an oral bacterium that can cause a fatal heart condition called infective endocarditis. By adhesive interactions, the bacteria colonize and trigger the disease.
• Researchers believe that the inflammatory damage in atherosclerosis is caused by infections from various sources including the bacteria from gum infections.
• The association between cardiovascular disease and periodontal disease was assessed with the help of a national survey. It was found that those with periodontitis had a 25% increased risk of coronary heart disease.
• People with evidence of oral infection were 30% more likely to present with myocardial infarction than people having no dental problem.
• The presence of bacteria in the gums and the mouth can affect the heart in various ways and can cause heart disease. Simple hygiene practices can help reduce infection and the incidence of heart diseases.

References:

1. Reza Nemati, Christopher Dietz, Emily J. Anstadt, Jorge Cervantes, Yaling Liu, Floyd E. Dewhirst, Robert B. Clark, Sydney Finegold, James J. Gallagher, Michael B. Smith, Xudong Yao, and Frank C. Nichols. ‘Deposition and hydrolysis of serine dipeptide lipids of Bacteroidetes bacteria in human arteries: relationship to atherosclerosis’. Journal of Lipid research (2017). http://dx.doi.org/10.1194/jlr.M077792
2. Shaneen J. Leishman, Hong Lien Do, and Pauline J. Ford. Cardiovascular disease and the role of oral bacteria. J Oral Microbiol. (2010). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3084572/

Source-Medindia