Tuesday, 3 April 2012

Gene Chip Helps Heart Disease Prevention

According to the Australian Institute of Health and Welfare, almost 700,000 Australians in 2007 suffered from coronary heart disease. Given the growing prevalence of obesity in this nation, it is considered a leading health risk, claiming the lives of 50,000 Australians in 2008; more than any other disease. (Australian Institure of Health and Welfare, 2011) Clearly, this is a condition common throughout the entire nation and until recently there has been no viable treatment pertaining to the field of genetics. However, the results of a study conducted by the Children’s Hospital of Philadelphia using the gene chip, may prove to be a new and successful treatment of coronary heart disease. (Rattue, 2012)
The human genome contains approximately 30,000 to 40,000 different genes, as such, the gene chip or microarray, is one of the most powerful technologies to emerge from modern genome studies. Historically, biologists were restricted to analyzing genes one at a time, but the microarray allows thousands of genes to be studied simultaneously. No larger than a postage stamp, gene chips (shown below) are comprised of thousands of nucleotide sequences attached to the chip in a grid formation. The attached sequences act as probes and are able to detect whether or not a test sample contains a particular gene. (Savada, 2008) This exciting, new technology was very recently applied to the search for suitable treatments of Coronary Heart Disease.



Heart disease is a condition caused by the accumulation of fat, cholesterol, calcium and other substances in the coronary arteries. Figure 2 (above) illustrates this situation where the artery’s cross-sectional area is reduced, causing an abnormal blood flow. If left untreated, the artery will inflame further until completely blocked, cutting off the supply of oxygen-rich blood to the heart. (National Heart Lung and Blood Institute, 2011) For a long time it has been common knowledge that inflammation and the buildup of fats and cholesterol causes heart disease, however the inflammatory agent causing the disease has remained unidentified; until now.

Brendan Keating Ph.D., co-author and researcher in the Center for Applied Genomics at The Children’s Hospital of Philadelphia is responsible for designing a gene chip which contains DNA markers for 2,000 gene variants associated with inflammation and heart disease. The study, according to Keating, “Provides robust evidence,” that the signaling protein interlukin-6 receptor (IL6R), “is implicated in coronary heart disease.” The team of researchers focused on single nucleotide polymorphisms (SNPs), variations in a DNA sequence where a single nucleotide differs between paired chromosomes in an individual. Specifically, Keating searched for variations in the IL6R gene that codes for the IL6R protein. When Keating’s gene chip was brought into contact with test samples of DNA from study participants, it detected specific gene variants that are capable of affecting risks of cardiovascular disease among the study participants. (Rattue, 2012)

The researchers in this study discovered that a particular single nucleotide polymorphism, the gene variant rs8192284, changed numerous biological markers that indicate the gene variant is associated with anti-inflammation. After examining data from patients with coronary heart disease and the control group, researchers discovered that individuals who possessed this particular gene variant were less likely to develop heart disease. This is because rs8192284 counteracts the signaling protein IL6R that causes inflammation, thereby serving as an anti-inflammatory. (Rattue, 2012)
Quite simply, the results of this study illustrate that other ILR6 blocking substances that mimic the effect of the discovered gene variant can be used as a substitute. One such substance, called tocilizumab, already exists however this drug is currently approved for the treatment of rheumatoid arthritis. (Ogbru, 2010) Keating was correct to suggest that the, “next step will be for cardiology researchers to design and carry out clinical trials,” to determine whether tocilizumab or other anti-inflammatory drugs will successfully prevent heart disease so that individuals worldwide who suffer from this degenerative condition may entertain the prospects of an improved quality of life. (Rattue, 2012)

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