Team:UIUC Illinois/Project/Background Info


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Cardiovascular Disease
Cardiovascular disease (CVD), also known as heart disease, has been the leading cause of death in the United States for over twenty years and is becoming a severe global health issue. Cardiovascular disease 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 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. 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
Current approaches in treating CVD are invasive and come with long recovery times, therefore it would be ideal to start from prevention. The best way to avoid microbiota-dependent atherosclerosis is through diet control and also exercise. However, self-control alone is not the most effective method for promoting public health. Specific to microbiota dependent atherosclerosis, researchers have reported that multiple bacterial strains in gut have different capacity in metabolizing L-carnitine and produce TMA, therefore it is difficult to target and eliminate them. So current suggestion is to inhibit the activity of gut flora by ingesting antibiotic cocktail. However, this method is far from satisfying. Because antibiotic pressure might lead to a selection of "super bacteria", which has multiple resistance to antibiotics and might do harm to our body and can't be killed. Also, the activity of gut flora is considered beneficial to host in various aspects, therefore it is crucial to keep a balance of the bacteria composition.

Chassis: Escherichia coli Nissle 1917
Safety is always a major concern when we talk about bacteria based treatment, so we have chosen to work with Escherichia coli strain Nissle 1917 as the platform for creating a safe probiotic. Claimed by manufacturer of its commercial form "Mutaflor", Nissle 1917 is "one of the best-examined and therapeutically relevant bacterial strains worldwide". E. coli Nissle 1917 has been widely tested for more than 80 years, mostly as a drug deliver system. The strain has T7 RNA Polymerase, which can transcribe DNA downstream of a T7 promoter.

Our Solution: Cardiobiotics
Based on the finding that chronic ingestion of carnitine-riched food will cause the composition change in gut flora, specifically induced the thrive of L-carnitine loving bacteria, the UIUC-Illinois iGEM Team developed a better strategy to construct a probiotic that will out-compete the current gut flora for L-carnitine. With our genetic parts, our genetically modified Nissle 1917, named as Cardiobiotics, presents a never-before-seen application of synthetic biology to the field of cardiovascular health. This summer, Cardiobiotics was tested effectively uptake L-carnitine and diverted to the pathway leads to 3-dehydrocarnine.

For references please see attributions.