Clinical Trial: L-arginine Therapy on Endothelium-dependent Vasodilation & Mitochondrial Metabolism in MELAS Syndrome

Study Status: Completed
Recruit Status: Completed
Study Type: Interventional

Official Title: Pilot Study to Investigate the Efficacy of L-arginine Therapy on Endothelium-dependent Vasodilation & Mitochondrial Metabolism in MELAS Syndrome.

Brief Summary: MELAS patients suffer from exercise intolerance, weakness, poor vision or blindness, poor growth, developmental delay, and deafness. They also have unique 'stroke-like' episodes (SLEs) which are not due to blockages of large or medium arteries. These 'strokes' are thought to be due to energy failure of very small brain blood vessels combined with energy failure in the mitochondria (cell battery) of the brain cells, especially in the back region of the brain in the vision centre. This leads to visual loss and paralysis. The overall goal of this study is to better understand the mechanism of these SLEs at the level of the brain cells and small blood vessels.

Detailed Summary: We will study a family of 3 siblings, each with different severities of MELAS, using safe, non-invasive tests. We will determine whether there is a decrease in the ability of small brain blood vessels to increase blood flow by dilating in response to certain stimuli such as increased blood carbon dioxide levels or in response to brain cell activation in the vision centre by visual stimuli. We will use a technique called BOLD-fMRI which can detect changes in brain blood flow. As exercising muscle also depends on increased blood flow and mitochondrial energy, we will study different measures of aerobic energy metabolism in exercising muscle using cycle exercise testing and special phosphorus-magnetic resonance spectroscopy which measures the changes in the major chemicals of muscle energy metabolism. The dietary amino acid L-arginine is known to dilate blood vessels increasing blood flow and to decrease toxic free radicals that are generated by dysfunctional mitochondria. We will determine the effect of a single dose and a 6 week trial of oral L-arginine, on brain blood vessel reactivity, brain cell activation and muscle aerobic function to see how useful this would be in the treatment of these patients and other mitochondrial disorders which present with strokes.
Sponsor: The Hospital for Sick Children

Current Primary Outcome: Muscle function investigation via 31P-Magnetic resonance spectroscopy [ Time Frame: 60 to 105 minutes post dose ]

We will study exercising quadriceps using our MR-compatible up-down ergometer and our well established aerobic exercise protocol at 65 % of maximal voluntary contraction.


Original Primary Outcome: Same as current

Current Secondary Outcome:

  • Total body maximal aerobic capacity [ Time Frame: 60-75 mins post dose ]
    Maximal incremental cycle ergometry is conducted in our CardioRespiratory Exercise Lab at HSC by our established protocols (26). Serum CK and quantitative AA (for arginine, ornithine and citrulline) will be measured pre- and post- exercise as well as eNO in order to correlate aerobic exercise parameters with serum arg and eNO levels..
  • CerebroVascular Reactivity [ Time Frame: 75-105 mins post dose ]
    Functional MRI-Blood oxygen level dependent (BOLD) of brain
  • Exhaled Nitric Oxide (eNO) [ Time Frame: 75 mins pre dose, 75 mins post dose ]
    eNO will be measured using single breath on-line measurements for the assessment of lower airway Nitric Oxide


Original Secondary Outcome: Same as current

Information By: The Hospital for Sick Children

Dates:
Date Received: May 18, 2012
Date Started: May 2012
Date Completion:
Last Updated: December 13, 2013
Last Verified: December 2013