Bacteroidetes, a type of bacteria found in the oral cavity and gastrointestinal tract synthesize lipids which have a different chemical structure and composition.
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.
‘Lipids from the Bacteroidetes signals bacterial invasion and they can easily pass through cell membranes and accumulate in the atheroma.’
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
Bacteroidetes That Make Fats Cause
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.
Lipids From Bacteroidetes Can
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
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
Further Research To Spot Lipid
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
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.
- 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
- 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/