Incretin mimetics as pharmacological tools to elucidate and as a new drug strategy to treat traumatic brain injury

Abstract

Traumatic brain injury (TBI), either as an isolated injury or in conjunction with other injuries, is an increasingly common occurring event. An estimated 1.7 million injuries occur within the US each year and 10 million people are affected annually worldwide. Indeed, some one-third (30.5%) of all injury-related deaths in the U.S. are associated with TBI, which will soon outstrip many common diseases as the major cause of death and disability. Associated with a high morbidity and mortality, and no specific therapeutic treatment, TBI has become a pressing public health and medical problem. The highest incidence of TBI occurs among young adults (15 to 24 years age) as well as in the elderly (75 years and older) who are particularly vulnerable as injury, often associated with falls, carries an increased mortality and worse functional outcome following lower initial injury severity. Added to this, a new and growing form of TBI, blast injury, associated with the detonation of improvised explosive devices in the war theaters of Iraq and Afghanistan, are inflicting a wave of unique casualties of immediate impact to both military personnel and civilians, for which long-term consequences remain unknown and may potentially be catastrophic. The neuropathology underpinning head injury is becoming increasingly better understood. Depending on severity, TBI induces immediate neuropathological effects that for the mildest form may be transient but with increasing severity cause cumulative neural damage and degeneration. Even with mild TBI, which represents the majority of cases, a broad spectrum of neurological deficits, including cognitive impairments, can manifest that may significantly influence quality of life. In addition, TBI can act as a conduit to longer-term neurodegenerative disorders. Prior studies of glucagon-like peptide-1 (GLP-1) and long-acting GLP-1 receptor agonists have demonstrated neurotrophic/neuroprotective activities across a broad spectrum of cellular and animal models of chronic neurodegenerative (Alzheimer's and Parkinson's diseases) and acute cerebrovascular (stroke) disorders. In line with the commonality in mechanisms underpinning these disorders as well as TBI, the current article reviews this literature and recent studies assessing GLP-1 receptor agonists as a potential treatment strategy for mild to moderate TBI.