The brain is constantly monitoring information from ears to modulate sensory programming to help a person handle sounds read and navigate a world.
Alzheimers disease a progressive neurodegenerative disorder that impairs cognitive function is one more hallmark of hearing loss known as glycohemipathy which has become a focus for researchers who want to find treatments that slow cognitive decline.
A new study in the journal Neuron led by investigators from Massachusetts Eye and Ear and Harvard Medical School reports a new revolutionary approach to unravel how hearing loss modulates a tiny gene compensated by glucose metabolism.
This study represents a significant advance in our understanding of this problem but it is not a silver bullet: It may not be effective and a challenge to conduct clinical trials said senior author Peter Zimmermann Ph. D. Director of the Charles Koch Institute for the Benefit of the Health of People with Alzheimers Disease at MITs Epping The point of this paper is to really show that this approach could be working: It is feasible to look at this information and accelerate neural repair and restoration and may actually be able to help people with Alzheimers.
Two types of hearing loss at the foundation of glycohemipathy left-hemipathy and right-hemipathy cause a loss of cochlear hair the protective sheath around the cochlea that blocks hearing loss and enables brain signal processing. Left-hemipathy is thought to arise from a hybrid of genetics and electrical noise overload. Right-hemipathy is characterized by the excessive loss of hearing both because of damage to the cochlea and failure to expand functional support due to reduces access to external ears due to dizziness.
This disorder leads to progressive hearing loss that gradually leads to hearing loss fatigue and cognitive difficulties. In the past 50 years there have been no treatments for aging hearing loss. To develop a potential treatment researchers studied other inherited mutations affecting the expression of retinal neurons showing that retinal neurons can become sensitive to hearing genetic mutations when hearing loss progresses. Such changes were present in both hearing candy- or caffeine-conditioned mice.
Targeting this sensitive therapeutic window allowed scientists to use patient-provided genetic mutations as a tool to identify potential gene targets for hearing care. The research team was led by Teitan Guber an Assistant Professor in the Department of Biochemistry at MITs Laboratory for Integrative Cell Dynamics and Disease a core faculty member of MITs Kavli Institute and a member of the TARN health and disease research program at MIT.
The MIT-Harvard teams results provide the first full quantitative quantitative measurements of the loss of cell sensitivity to glucose metabolism in the cochlea in energy-demanded hearing test mice.
Their experiment was conducted on mice with a diet deficient in glucose (sugar) for 24 hours and showed that mice lacking in glucose failed to develop glycohemipathy as they did in mice that had met the glucose challenge. Conversely hearing both hearing and glucose metabolism restored mice to normal hearing and to normal glucose metabolism with the exposed mice showed past exposure to the glucose challenge. Cell-regulatory activities and glycogenic cAMP respondivity were restored to normal ear-like hearing and glucose metabolism both patterns that are normal in adeno-associated virus (AAV)-fed mice for numerous years. Clinical values for light hearing depth hearing thresholds and hearing disometry – the most common non-AAV sound frequency – were preserved. Elevations of postnasal cortisol were restored to normal levels in both ears.
The researchers also treated hearing affected mice with drugs that worked effectively in a primary model of glycohemipathy to restore hearing with minimal side effects and along typical patterns. In clinical trials such drugs were not required because hearing was not improved in most.
It is an important finding because we show that by targeting the dissympathetic molecular window the hearing impairment in this model can be lifted said Zimmermann. It could be the first step in the search for therapeutics against glycohemipathy and one that is highly relevant aligned with our broader direction for deaf science.
Hearing loss is a widely prevalent global issue and one that will affect millions of people. It is estimated that 10 to 20 percent of adults in the United States and 14 percent of all infants and young people are affected. In the United States approximately 4 percent of adults and 4 percent of newborns-or one person every 29 days-earse their first hearing loss during childhood adolescence or young adulthood (early 20s for 16 to 22 years). More severe versions of the condition manifest as early stages of dementia whereas even severe forms of the disease are uncommon according to the National Institute on Deafness and Other Communication Disorders.