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Interest in inosine
SHEFFIELD, U.K.—Researchers at the University of Sheffield in the United Kingdom have employed a new metabolic phenotyping technology developed by California-based Biolog Inc. to identify critical metabolic differences in patients affected by amyotrophic lateral sclerosis (ALS). Dr. Scott Allen, a fellow at Sheffield University’s Institute for Translational Neuroscience (SITraN), and his team had been exploring the idea of how ALS might affect metabolic flexibility in known central nervous system (CNS) models when he attended a lecture about Biolog’s cell analysis technology. Intrigued by the possibilities, he applied for and received funding to purchase to purchase the Biolog OmniLog instrument, a state-of-the-art metabolic assay system using MitoPlates.
In a scientific first, Allen, joined by Dr. Laura Ferraiuolo and Prof. Dame Pamela Shaw, reprogrammed patient skin cells to become brain cells known as astrocytes, and then monitored their behavior to identify novel pathways of metabolic dysfunction. The Biolog OmniLog looks for and finds differences astrocyte-metabolism in ALS patients. Astrocytes create the brain environment, build up the micro-architecture of the brain parenchyma, maintain brain homeostasis, store and distribute energy substrates, control the development of neural cells, synaptogenesis and synaptic maintenance, and provide for brain defense.
ALS is a progressive neurodegenerative disease that affects nerve cells in the brain and the spinal cord, named from the Greek that roughly translates to “No muscle nourishment.” When a muscle has no nourishment, it atrophies or wastes away. Healthy motor neurons reach from the brain to the spinal cord and from the spinal cord to the muscles throughout the body, but as they degenerate, the ability of the brain to initiate and control muscle movement is lost, particularly in the motor neurons that provide voluntary movements and muscle control.
By comparing the energy metabolism of cells taken from ALS versus normal controls, the team found that the ALS cells were losing an enzyme called adenosine deaminase, which negatively impacted their ability to convert adenosine into energy. The concern is that a toxic buildup of adenosine leads to a subsequent loss of inosine, a metabolic intermediate that also protects neuronal cells. As further confirmation, Allen fed the ALS astrocytes inosine, and found that energy production increased and the patient’s astrocytes became more supportive towards motor neurons, helping them live longer.
“We are really excited about this set of results, as no one has implicated adenosine deaminase in ALS before,” commented Allen. “Our results indicate that the higher the level of adenosine deaminase, the greater the protection against adenosine mediated toxicity, and the greater support towards motor neurons when given inosine. Although we are at an early stage, I think approaches aimed at increasing adenosine deaminase levels, combined with inosine supplementation, has the potential to slow down disease progression in ALS patients and improve the quality of life. Altering the level of adenosine deaminase by gene therapy has previously been shown to be beneficial and safe in patients suffering from severe combined immunodeficiency disease. Further, inosine is a safe and readily available nutritional supplement which has been successfully tested in Parkinson’s disease patients. However, further testing in the laboratory will need to be performed.”
“There are two distinct levels of energy metabolism in eukaryotic cells,” according to Dr. Barry Bochner, CEO and chief scientific officer at Biolog. “The cytoplasm is where the glycolytic pathway takes place, and the mitochondria is where the TCA cycle and electron transport chain take place. [Biolog’s] MitoPlates measure more than 50 parameters of mitochondrial function, [which] allows scientists to examine both the live cell metabolism and mitochondrial metabolism. This cannot be done by mass spec because when cells are extracted for mass spec analysis, the external and internal membranes of the cell are dissolved and the metabolism of all compartments are mixed together.”
The Sheffield team is eager to continue exploring whether levels of the ADA enzyme are protective in ALS patients, and will be using gene therapy to increase ADA levels in astrocyte ALS models to assess the downstream consequences.
“Our long-term aims are to take this into preclinical ALS models as a way to slow down disease progression,” asserts Allen. “We now believe the provision of inosine could be helpful in ALS with adenosine deaminase deficiency, so the next step is to ask: does increasing astrocyte ADA levels by gene therapy in vitro increase bioenergetic capacity and make astrocytes more supportive to neurons and how? If so, we will look to understand the mechanisms involved and then look to test in preclinical models of ALS the idea of ADA modulation in combination with inosine supplementation, all with the long-term goal of human translation.”
The results of the Sheffield tests are also exciting to Biolog. Bochner pointed out that this is the second validation the technology for gaining biochemical insight into a human disorder, following a successful detection of defective tryptophan metabolism in patients with autism. Neuroscience has been the most promising application for the OmniLog instrument, with the next likely targets being Parkinson’s disease and Alzheimer’s disease, but there are many possibilities on the horizon.
According to Bochner, “The Biolog cell analysis technology was developed with the intent of providing scientists with a new approach for comparing normal versus disease cells to look for differences that could underlie the deficiencies. Credit goes to Dr. Allen and his colleagues for being one of the first to set up an excellent cell model and then employ the Biolog technology strategically. But certainly this applies just as much to cancer, aging, obesity and diabetes, immune cell activation, and cardiac and kidney ischemia. Our cell analysis technology can also determine metabolic and other phenotypic changes induced by mutations, making it an ideal companion technology to CRISPR genetics."