When former public affairs officer, Linda, started experiencing heart palpitations and feeling unusually tired, she was confused. She led a healthy lifestyle, maintaining a nutritious diet and a regular workout schedule. She mistakenly took the heart palpitations as a sign to exercise more, but her symptoms became intolerable as she began to experience near-fainting episodes. Her doctor advised her to get her heart tested.
Linda’s doctor administered an echocardiogram to see how well her heart was functioning. The test measures the ejection fraction (EF), which ultimately accounts for the percentage of blood pumped out of the patient’s heart, with every beat. This simple test has a patient lie on an examination table as the doctor holds a transducer- (an instrument that looks similar to a computer mouse) to the patient’s chest. The transducer sends sound waves to the heart; these waves bounce off the heart and are collected and processed by a computer (Mayo Clinic, 2011).
When Linda finally got her test results back, she was alarmed to find her EF was 25%. An EF of less than 40% means the heart might have a weakened muscle, making it unable to pump enough blood to satisfy the body’s demands (“Linda’s Story,” 2010). A healthy heart’s EF lies between 55- 70%. Linda’s doctor decided to take a chest x-ray and it showed that her heart was enlarged; she needed immediate medical attention.
Linda’s doctor concluded that she had dilated cardiomyopathy. According to the Cleveland Clinic, this disease affects about four per 10,000 people in the United States every year (Cleveland Clinic, 2000). Only an estimated 50% of patients with dilated cardiomyopathy live longer than five years after their diagnosis. Shocked and terrified for her life and her family’s well being, Linda frantically did some research on the disease to answer her questions.
“What exactly is dilated cardiomyopathy?” she wondered.
She discovered that it is a disease that affects heart muscles. It mostly targets the left ventricle, which is the heart’s main pumping chamber. The affected ventricle becomes enlarged and can no longer pump blood to the rest of the body as well as it should. This can lead to complications including heart failure, cardiac arrest, and pulmonary edema. (Mayo Clinic Staff, 2011).
Scientists have found the Meleagris gallopavo, more commonly known as the turkey, to be an accurate model in mimicking the changes of a failing human heart because dilated cardiomyopathy affects turkeys’ and humans’ hearts in similar ways.
Humans and turkeys have similar function and structure to their hearts. The right ventricle moves blood through the lungs and back to the heart, while the left ventricle pumps blood to the rest of the body. In both organisms, the left ventricle is thicker because it has to pump the blood to the aorta, which, in turn, pumps blood to the rest of the body. (“The Turkey Anatomy Lesson,” 2012). Turkeys and humans share many of the same natural chemicals, such as tryptophan and auriculin. Tryptophan is an amino acid that is essential to the human diet in regulating appetite and sleep and can elevate one’s mood. Auriculin is a hormone released in the atriums of the heart when the body experiences an abnormal increase in blood pressure. This hormone is released during heart failure in both humans and turkeys. Auriculin keeps the left ventricle from failing for as long as possible. (Brandt et al., 1993).
Turkeys and humans both have calcium metabolisms. Calcium metabolism, or Ca+2 metabolism, maintains the body’s calcium levels (Genao et al., 1996). Calcium is used as a second messenger for hormones, such as auriculin, during heart failure. This means that if the hormone does not do its job, calcium will tell it to “go to work.” Also, calcium ions in the body bind to troponin complex, which is a protein that can be found in cardiac and skeletal muscles. Troponin plays a role in muscle and heart contraction in both humans ad turkeys. When the calcium ion binds to the troponin, the heart can contract and pump blood through it out to the body (Farah & Reinach, 1995). With turkey and human heart failures sharing so many characteristics, using turkeys as a model for studying dilated cardiomyopathy may lead to ground breaking discoveries.
Currently, the most common treatments for dilated cardiomyopathy are prescription drugs. Some patients are given Angiotensin converting enzyme inhibitors to help the heart’s pumping abilities. Others are given diuretics, or water treatments that make the patient urinate more frequently, to keep the fluid from collecting in the body. They especially remove fluid in the lungs, making it easier for the patient to breathe (Mayo Clinic Staff, 2012). Now, with turkeys as an animal model, many more advancements can be made. Since about five percent of the turkey population has dilated cardiomyopathy (Genao et al., 1996) it would be easier to find a large enough sample for multiple tests and trials to be done to develop therapies and other treatments for the disease.
At Wayne State University, Dr. J.P. Jin, professor of physiology, made a groundbreaking discovery in 2010. When he experimented on turkeys with cardiomyopathy he found that when a mutation in troponin I was countered with a mutated form of troponin T (two types of troponin complex proteins) the negative effects of each mutation would cancel each other out. This actually restored the effected turkey’s heart back to its normal condition (“Dr. Jin,” 2010). Virginia Tech. University is currently researching turkeys and cardiomyopathy. They are focusing their research on the biochemical and genomic studies of dilated cardiomyopathy in turkeys. The possibilities are endless; turkeys are giving cardiomyopathy patients, like Linda, another thing to be thankful for.
- Every four in 10,000 people in the United States have dilated cardiomyopathy, a disease that causes the left ventricle of the heart to become enlarged
- Turkey hearts can serve as a model for the human heart as it undergoes heart failure and cardiomyopathy because their hearts are very similar
- Dr. Jin at Wayne State University discovered from the turkey model that by countering a mutated form of cardiac muscle protein with another form of mutated protein, a heart’s normal condition can be restored
- Turkeys can be used as model organisms to develop new treatments for dilated cardiomyopathy
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