By DongYoung Yoon
Alzheimer’s disease, also known as AD, is the “6th leading cause of death in United States” (alz.org). The years between 2000 and 2010, the number of deaths caused by Alzheimer’s increased by 68% (alz.org). In the year 2013, the number of Americans with Alzheimer’s disease is estimated to be 5.2 million. It was and still is recognized as a fatal disease and the urgent need of better treatments for the Alzheimer’s was growing every day until recently. A discovery of new potential treatment was made, in January 2012, to alleviate Alzheimer’s disease: the insulin. The word “untreatable” is no longer associated with Alzheimer’s disease.
There are several risk factors for AD: age, family history, and genetics (alz.org). Age is the “greatest known risk factor for Alzheimer” (alz.org). Individuals age 65 or older are at high risk of AD, and the percentage of risk doubles every 5 years. Therefore, an individual who is 85 or older has a 50 percent of risk (alz.org). Since AD is due to aging brain that cannot continue the active neuron transmission, the risk dramatically increases in old ages. Another factor is family history, and most people with parents, siblings, or children with Alzheimer’s are very likely to develop AD (alz.org). Family history could be categorized by environment and genes. People who are genetically related to Alzheimer’s patients are most at risk but, people who are environmentally related to Alzheimer’s patients are also at risk (alz.org). The reason for that could be the stress and cognition. Since their minds are always alert and stressed, there is a possibility that they could be suddenly attacked by the distortion of brain functions which could lead to Alzheimer’s or other neurological diseases.
However, what exactly is an Alzheimer’s disease? The Alzheimer’s Association defines the Alzheimer’s disease as “a type of dementia that causes problems with memory, thinking and behavior” (alz.org). The brain is also part of the body; therefore, it ages as people get older. Some people experience “slowed thinking and problems with remembering things” more frequently than others (alz.org). Though, that does not mean that they have Alzheimer’s; it is not as simple as many people think. This disease is a much more severe and terrifying. Alzheimer’s is caused by the failure of brain cells. The common symptoms are “difficulty remembering newly learned information, serious memory loss, confusion and changes in the way the mind works” (alz.org). Usually, Alzheimer’s begins by affecting the ability of the learning system in the brain. Therefore, a person might have difficulty learning new things. Then Alzheimer’s develops throughout the brain causing “disorientation, mood and behavior changes, confusion about events, time and places, unfounded suspicions about family and friends, memory loss, difficulty speaking, swallowing and walking” (alz.org). The area in the brain called, hippocampus that controls the memory is most affected by the Alzheimer’s disease. This memory loss is very different from any other amnesia because Alzheimer’s causes constant and degenerative memory loss. The most frightening thing about Alzheimer’s disease is that these symptoms develop very slowly and for most people, by the time they realize that they have Alzheimer’s; it is too late for them to get treatments. Alzheimer’s is not just a neurological disease, but also a life and family destructor by hurting the caregivers of the patient. For many years, no medicine has developed to cure Alzheimer’s; the best thing that treatments can do is slowing down the process as possible. Therefore, the finding of insulin as a possibility for Alzheimer’s treatment is like a light shining over a long darkness.
Although, why is it has to be the insulin? Two brilliant researchers, Hölscher and Li, have found astonishing connections between diabetes and Alzheimer’s disease. According to their article, “Neurobiology of Aging,” there was a recent discovery that “type 2 diabetes was identified as a risk factor for Alzheimer’s disease.” Studies found that there are correlations between type II diabetes and the development of AD. The examination is done to patients in Mayo Clinic, and showed “a clear correlation between AD and type II diabetes; 85% of AD patients had diabetes” (Hölscher, and Li 1495-1496). This correlation is both statically and scientifically correct because, many researchers have found more functions of insulin. In addition to its main role in regulating blood sugar level, insulin has the ability to “stimulate the growth of cells, induce dendritic sprouting, neuronal stem cell activation, and exert neuroprotective effects” (Hölscher, and Li 1495-1496). It also has numbers of important effects on the brain, such as promoting cell repair, encouraging cell genesis and, protecting the brain from beta-amyloid, deposits of fragmented protein that cause brain plaques by building up between nerve cells (CNN Health).
The other recent findings show that neurodegenerative disorders such as AD might have caused by desensitized insulin receptors leading to weakened signaling of insulin in the brain (Hölscher, and Li 1495-1496). The other way to describe the weakening of insulin signals is insulin resistance, a condition when insulin is not effective in lowering the glucose level. In the structure of the brain, the areas that most directly affected by the insulin resistance in the CNS, central nervous system, are the hippocampus and the HPA axis, which controls the memory and regulates cortisol, respectively (Watson and Craft). The insulin resistance could also affect “other cellular events such as LTP, long-term potentiation which is a long-lasting enhancement in signal transmission between neurons.” (Watson and Craft) In a result, insulin resistance promotes cognitive decline and eventually, a failure.
However, the question is raised frequently by the researchers of “how to provide the insulin in such a way that it improves brain function without disrupting blood sugar levels” (Smith). The main role of insulin is to regulate the blood sugar levels and if the insulin is provided in a way that interrupts its role, there will be a severe problem in result; either the glucose level shoots up or drops dramatically. As a solution, Hölscher and Li and many other researchers recommended a nasal spray. Since the nose is closest to the brain, “applying via the nasal passage where it can enter the brain more directly,” (Hölscher and Li 1495-1496) and the insulin will reach the brain in few minutes (Smith).
A research was done by Christian Benedict, a German researcher, which evidenced the improvement in human memory by intranasal insulin. According to the article, “Intranasal Insulin Improves Memory in Humans: Superiority of Insulin Aspart,” the hippocampus, an area in the brain that functions in memory, forming, organizing, and storing, “display[s] a high density of insulin receptors and this implies that this is the area where main insulin signaling is involved” (Benedict). There have been studies done in both animals and humans that definitively prove this theory. One study was done in rats and after they were trained with a water maze, the amount of insulin receptors increased in the hippocampus. Another study was done in human, and after an injection of insulin, they improved in recalling the previously learned vocabularies. These studies demonstrated the effects of insulin on the improvements of learning and memory. The study with rats was done to observe the amount of insulin is activated after learning and the other study with human was done in order to show that memory is dependent on the amount of insulin; if the amount of insulin increases then the ability to store more vocabulary increases. In conclusion, insulin and the brain are highly related, especially in the areas that involve learning.
Last year, the University Of Washington School Of Medicine formed a research group, led by Dr. Suzanne Craft, to provide evidence for memory improvement in Alzheimer’s patient with insulin nasal spray therapy. The research was done to “104 participants with mild cognitive impairment and mild to moderate Alzheimer’s” (Craft). The treatments were administered through nasal spray and there were no side effects (Craft). Craft reported that, “there are growing evidence of insulin plying vital role in brain function and decrease the level of memory problem.” Moreover, Benedict informed that, “there were recent studies that revealed beneficial effects of acute and long-term intranasal administration of regular human insulin (RH-I) on declarative memory in human.” Thankfully, there has been advancement in the development of insulin as a treatment option for AD. Researchers found that insulin ASP-I, insulin aspart, might be better for declarative memory in human because “amino acid B28 is replaced by aspartic acid which reduces the tendency of the insulin molecule to self-associate; not like regular insulin RH-I” (Benedict). One day, the method of insulin nasal spray will bring an enormous revolution in neurological medicine.
Though, the biggest challenge regarding the insulin treatment is insulin resistance (Simon). It is statically proven that there is a strong correlation between diabetes and Alzheimer’s (Hölscher, and Li 1495-1496). This means that diabetes patients are at higher risk of being diagnosed with Alzheimer’s disease. Both type I and type II diabetes are caused by insulin resistance so, providing insulin in any ways will not work. Therefore, insulin might be a treatment option for Alzheimer’s disease, but it is hard to say, for many researchers, that insulin is a cure for Alzheimer’s; at least not yet. The revolution is not far ahead.
Still Alice by Lisa Genova is about a woman, Alice Howland, with Alzheimer’s disease. In this book, the author brings up an interesting issue relating to today’s society. She says, “Losing her yesterdays, her short-term memory hanging on by a couple of frayed threads, she is living in the moment, living for each day. But she is still Alice” (Genova). For most of people, it is considered as a fatal neurological disease that many people are desperately waiting for the treatments. Hence, Alzheimer’s disease patients are neglected today still and the perceptions towards them should definitely be changed. Aging is a natural process and like Lisa Genova said, AD patients are not dying, though they are living the life with it.
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