Understanding mitochondrial disease

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When the freezers in his research lab were failing, Dr. Adeel Safdar took to sleeping on the floor of the research lab to safeguard the precious samples that are at the core of his research into the biochemistry of mitochondrial disease. The term mitochondrial disease covers a multitude of heterogeneous diseases that are linked clinically and biochemically. There is primary genetic disease and also secondary mitochondrial disease where there is evidence of mitochondrial dysfunction. These include but are not limited to neurodegenerative, later-onset diseases such as ALS, Alzheimer’s and Parkinson’s disease and even Type 2 diabetes, cancer and heart disease.

Presenting symptoms of mitochondrial disease vary widely and may include developmental delays, migraines, seizures, strokes, intermittent weakness, neuropathic pain, gastrointestinal problems, muscle pain, cardiomyopathy, visual or hearing loss, diabetes, fatigue or unexplained vomiting. When three or more organ systems are involved you should think mitochondrial disease.

To say Dr. Safdar is passionate about his work is an understatement but he is only one part of an equally committed multi-disciplinary team at the Corkins/Lammert Family Clinic for Mitochondrial Medicine and Research at Children’s Hospital in Hamilton Ontario. What makes this clinic unique is the research team is also the clinical team therein enabling the patient to be at the centre of every point of care and at the bench when research discoveries are being made.

MORE: UNRAVELLING THE MYSTERY OF LYME DISEASE: WHY CANADA NEEDS TO DO MORE

Under the watchful eye of Clinical and Research Director Mark Tarnopolsky MD, PhD, FABEM, FRCPC, Professor and Division Head of Neuromuscular and Neurometabolic Disorders in the Department of Pediatrics at McMaster University, the team sees thousands of patients a year from across Canada and around the world.

Delores Reid is the person who keeps the clinic humming while Linda Brandt R.N. is the first point of contact with patients as well as overseeing the Inherited Metabolic Diseases (IMD) Program for her Ontario patients. The program covers the full cost of certain outpatient drugs, supplements and specialty foods used to treat metabolic disorders including mitochondrial disease. The “mito cocktail” is a prescribed concoction of antioxidants including beta carotene and vitamins C and E that have been shown to have an oxidative protective effect in neurodegenerative disease. Other therapies believed to improve mitochondrial function include creatine, coenzyme Q10 and idebenone.

When the expertise of a genetic counsellor is required, Lauren Brady is called in to action. She too is involved in research with her particular interest being in the use of new genetic testing technology to identify the primary causes of an individual’s previously undiagnosed neuromuscular or mitochondrial disease. The advent of new genetic tests such as whole exome sequencing has greatly improved the opportunity for a cost-effective way of identifying genetic mutations associated with mitochondrial disease.

Both Kristin Frescura and Erin Hatcher are the clinic’s exercise testing technicians. Kristin’s research focus is on how regular exercise can improve the quality of life of those suffering from mitochondrial disease and slow the progression of the disease. She is currently working on the NAMDC (North American Mitochondrial Disease Consortium) Study that includes a patient registry and biorepository. Erin, on the other hand, coordinates the clinic’s clinical research activities and is working on several studies, including antioxidant therapies for Friedreich’s Ataxia, exercise as a countermeasure for ageing, and sialic acid therapies for patients with Hereditary Inclusion Body Myopathy.

According to Erin “We’ve lost some very beloved patients, and through the sadness has come great motivation to work towards the best treatments possible.” Today young patients who visit the clinic are treated to Tucker’s Toy Box which is a labour of love for Erin and a lasting tribute to a very special patient Tucker Patterson who succumbed to mitochondrial disease in 2010.

 

Dispelling myths about mitochondrial disease

MYTH

Mitochondrial disease is a childhood disease.

 

FACT – Although mitochondrial disorders are commonly seen in infants and children, they can occur at any age.

 

MYTH

An individual with mitochondrial disease has mental retardation, growth problems, and/or seizures.

 

FACT – Only some individuals have these developmental problems. Patients’ symptoms can range from extremely mild to severe, involve one or more body systems, and can emerge at any age. The brain, muscles, heart, liver, nerves, eyes, ears and kidneys are the organs and tissues most affected. Most patients’ symptoms fluctuate over the course of their disease at times experiencing no or few symptoms while at other times experiencing many and/or severe symptoms. Even family members with the same disorder can experience vastly different symptoms.

 

MYTH – Mitochondrial diseases are inherited only from your mother.

FACT – Not true. There are several ways mitochondrial diseases can be inherited. Under normal circumstances, a person’s ‘blueprint’ — the DNA in our genes that makes each of us unique, comes from both our mother and our father. In mitochondrial diseases, these genes have mutated. People with mitochondrial disease receive mutated genes from each parent or a mutated gene from only one parent.

Another way a mitochondrial disease can be inherited is, in fact, only from the mother. In this type, there is a mutation in the mitochondrial DNA – DNA that exists only in the mitochondria. Only mitochondrial disorders caused by mutations in the mitochondrial DNA are exclusively inherited from mothers.

 

MYTH – If parents don’t have any symptoms of a mitochondrial disease, there’s no chance that their children can have a mitochondrial disease.

FACT – Parents can be ‘genetic carriers’ of a mitochondrial disease. This means that each parent has inherited a defective gene but do not show symptoms of the disease. However, ‘carriers’ are able to pass the defective gene onto their children.

 

MYTH – Since mitochondrial disease is incurable, no treatments can be given to these patients.

FACT – Even though these disorders are chronic and incurable, treatments are available. Early treatment of symptoms can reduce symptoms or slow progression of the disease. Certain supplements may improve mitochondrial disease-related symptoms.

 

MYTH – A muscle biopsy is the “gold standard” for diagnosis of mitochondrial disease.

FACT – Although the muscle biopsy is a powerful diagnostic tool, it is not the only option. A biopsy examination includes microscopic evaluation, enzyme testing, and genetic testing. In some patients, the diagnosis can be made based on clinical symptoms and a positive blood test (identifying a genetic mutation) or a combination of clinical findings and other non-invasive testing. In either case, a muscle biopsy is not necessary. Finally, since biopsy results usually do not alter the long-term outcome or treatment considerations, some specialists and patients choose to treat without the need for a muscle biopsy.

 

MYTH – Over-the-counter nutritional supplements offer the only protection for our mitochondria.

FACT – Beside nutrient support, there is exciting early evidence that exercise may have a role in repairing malfunctioning mitochondria. The potential to re­store or preserve mitochondrial health holds great promise for treating mitochondrial disease in the future.

 

 

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