Tarantula treatment: Medicine's next big thing?
BACKGROUND: Duchenne muscular dystrophy (DMD) is a vicious form of muscular dystrophy that occurs mostly in boys. It is caused by an alteration in a gene, called the DMD gene that can be inherited, but it also can occur in people who do not have a known family history of the condition. The condition causes progressive loss of muscles function and weakness that begins in the lower limbs. Boys with DMD do not make the dystrophin protein in their muscles. It affects approximately one in 3500 boys worldwide. (Source: www.genome.gov)
SYMPTOMS: When a child has DMD, symptoms normally appear before six years old and may appear as early as infancy. The first noticeable symptom is in motor milestones. For example, sitting and standing independently will be more of a challenge. The average age of walking in boys with DMD is 18 months. DMD attacks the leg and pelvic muscles, resulting in a waddle and difficulty climbing stairs. Calf muscles usually enlarge and the muscle tissue eventually is replaced with connective tissue and fat. When the leg muscles contract, the muscles become unusable because the muscle fibers are shortened and fibrosis occurs in connective tissue. Symptoms are usually prevalent in boys ages one to six. There is a steady decline in muscle strength from age’s six to eleven. By age ten, patients may need braces to walk and in a wheelchair by 12. Few individuals with DMD live beyond 30. Cardiomyopathy and breathing complications are common causes of death for DMD patients. (Source: www.genome.gov)
TREATMENTS: Treatment is aimed at the symptoms of DMD. Assistive devices for respiratory complications can be needed at night. Aggressive management of dilated cardiomyopathy with anti-congestive medications are used with cardiac transplantation in more severe cases. Prednisone (a steroid shown to prolong the ability to walk by two to five years) is used to improve the function and strength of patients with DMD, but it can cause high blood pressure, weight gain, delayed growth, and behavior changes. Deflazacort is a synthetic version of prednisone used in Europe and is believed to have fewer side effects. Cyclosporine is another medication used in children, but is controversial because of cyclosporine-induced myopathy. Several therapies are under investigation, including PTC124, pentoxifylline, coenzyme Q10, glutamine, and oxandrolone. (Source: www.genome.gov)
NEW TECHNOLOGY: Another new therapy for DMD that’s under clinical trials was discovered in the venom of a spider, the Chilean rose tarantula found in South America. The spider’s venom was originally used to study the effect it had on important cellular structures (called mechanosensitive ion channels). These channels are small tunnels connecting the inside of a cell to the outside world. Normally the tunnels are closed, but when a cell is contorted or stretched the tunnels open and let calcium and other substances into the cell. This is similar to what happens in DMD. The defective genes are missing proteins that help muscles keep their shape. The cells then buckle, making the ion channels to open and calcium floods in, resulting in the body digesting muscles from the inside out. Researchers believe that if the channels could be closed then symptoms could be suppressed. This is where the spider comes in. A protein in the venom of the Chilean rose tarantula was discovered to keep the ion channels closed. Now researchers are testing the protein therapy in dystrophic mice. Earlier experiments show no toxic reactions while on the drug for 40 days. (Source: www.buffalo.edu)
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