Team:UIUC Illinois/Project/Background Info

Cardiovascular Disease
Many heart illnesses are deemed cardiovascular disease. Cardiovascular disease, also known as heart disease, is the medical term used to describe a slew of heart-related health problems, including myocardial infarctions, heart failure, and stroke. A major source of these problems is the onset of atherosclerosis, a condition characterized by the buildup of plaque in one’s arteries. There are a variety of causes of atherosclerosis, but our project addresses the proatherogenic substance trimethylamine-n-oxide, a metabolite of certain chemicals often found in red meat and energy drinks.


Intestinal Microbiota Promotes Atherosclerosis
Meat consumption correlates to high risk of cardiovascular disease (CVD), mostly because the high level of fats and cholesterol in diet may promote atherosclerosis. Recent research concluded that those two factors may not be sufficient in establishing the link between meat consumption and CVD risk. Researchers in Cleveland Clinic found that intestinal microbiota (gut bacteria) metabolize dietary L-carnitine into trimethylamine (TMA), which is further converted to trimethylamine-N-oxide (TMAO) and accelerates atherosclerosis in mice.

L-carnitine, a quaternary ammonium compound, plays an essential role in the generation of energy in cells due to its function in transporting fatty acids from the cytosol into the mitochondria. For this reason it is sometimes sold in the form of "food supplements" and is marketed as a "natural" health product. However, for normal healthy adults, the cells of the human body produce sufficient amounts of L-carnitine as needed. Recent research in mice with intact intestinal microbiota suggested long-term carnitine consumption "reduced in-vivo reverse cholesterol transport." They also analyzed 2,595 cases of patients who were undergoing cardiac evaluation, and found out a increased rate of cardiac events among those patients with high plasma L-carnitine levels and high TMAO levels.


Current Solutions
The best way to avoid TMAO-induced atherosclerosis is to exercise moderation when consuming red meat and energy drinks. However, self-control alone is not the most effective method for promoting public health. There are no treatments to directly reverse the buildup of plaque once it has embedded itself in the walls of the arteries. In severe cases, bypass surgeries and stents are used to redirect and manage blood flow through the body. These procedures are rather invasive and come with long recovery times. The University of Illinois (UIUC) iGEM Team sought a better method for people to be able to eat the food they love while maintaining a healthier heart.


Gut Bacteria Ecology and Intervention
Most current treatments of atherosclerosis are not preventative. Our team looked to provide one such preventative treatment by halting the production of TMAO. Thousands of gut bacteria reside within the human digestive tract, and some L-carnitine loving bacteria found in the flora are responsible for converting L-carnitine into TMA.

Our strategy for combating the production of TMA is to make a probiotic that will out-compete the current gut flora for L-carnitine. This probiotic will then process the L-carnitine into a much less harmful product.


Genetically Modified Nissle 1917
Safety is always a major concern when introducing foreign organisms into the body, so we have chosen to work with escherichia coli strain Nissle 1917 as the platform for creating a safe probiotic. The Nissle strain is deemed safe for human consumption and probiotic use by the United States Food and Drug Administration.

E. coli has a natural L-carnitine uptake system, but to out-compete the preexisting gut bacteria, we decided to genetically modify our strain. The genes CaiX and CbcVW were selected to be implemented into our bacteria from pseudomonas aeruginosa, a bacterium with unique adaptations for L-carnitine uptake and processing.

Additionally, in order to break down the L-carnitine, we introduced the CDH gene from p. aeruginosa into our Nissle cells. This gene encodes for L-carnitine dehydrogenase, a protein that metabolizes L-carnitine along a safer alternative pathway.


Our Solution: Cardiobiotics
With our genetic parts, our Cardiobiotics present a never-before-seen application of synthetic biology to the field of cardiovascular health. Our engineered bacteria can uptake L-carnitine and divert it along pathway toward the end product of glycine-betaine, a much less harmful product than TMAO.