Diabetes and brain damage: The wireless connection!
May 25, 2018
When citing the dangers of Type 2 diabetes, doctors usually focus on associated, life-threatening conditions such as heart disease and risk of stroke along with micro vascular complications such as retinopathy, nephropathy and neuropathy. Research is beginning to show, however, that diabetes can damage the brain directly—filling in the details of a picture in which insulin resistance, memory loss, and even Alzheimer’s disease are ominously intertwined. While the deleterious effects of diabetes mellitus on the retinal, renal, cardiovascular, and peripheral nervous systems are widely acknowledged, less attention has been given to the effect of diabetes on cognitive function. Both Type 1 and Type 2 diabetes mellitus have been associated with reduced performance on numerous domains of cognitive function.
Life expectancy is increasing, that’s good news. The downside to this trend is that more and more people will develop diseases such as diabetes or Alzheimer’s and some may even be unfortunate to be a state of ‘buy one – get one’ fate (diabetes and Alzheimer’s). In fact, epidemiologic studies have shown having Type-2 diabetes increases the risk of developing Alzheimer’s disease by 65% and that 80% of Alzheimer patients have problems of glycemic control.
Meals, insulin and brain function: Within minutes of a meal, insulin is sent to the brain to help neurons absorb and use glucose. Smaller increases in insulin also occur throughout the day, likely in response to neural signals. In the brain, insulin has a number of roles to play. It promotes glucose uptake in the neurons of the hippocampal formation and the frontal lobes, areas that are involved in memory. Insulin also strengthens the synaptic connections between brain cells, helping to form new memories. In addition, insulin regulates the neurotransmitter acetylcholine, which plays an important role in learning and memory. Finally, insulin is involved in blood vessel formation and function.
Brain insulin resistance: Insulin and related growth proteins in the brain are vital for cell survival, and both glucose and insulin appear to regulate many brain functions, including learning and memory. Dysfunction of these chemicals contributes to cognitive deficits. Chronic episodes of high or low levels of blood glucose may directly affect insulin’s actions in the brain or damage brain cells, leading to cognitive impairments. New evidence shows that the insulin-insensitive state found in our liver, fat and muscle cells/tissues corresponds with insulin sensitivity in our central nervous system, as well (insulin resistance at the level of brain). This impacts the areas of the brain responsible for cognition, memory and learning. Diabetes may be wreaking havoc especially in the hippocampus. The hypothalamus—a brain region that regulates metabolic processes and activities like hunger, thirst, and body temperature—also appears to be involved, especially areas that respond to low blood sugar and regulate energy balance, body weight, and the sensitivity of the liver and muscles to insulin. Insulin is involved in long-term potentiation, a process of memory formation at the cell level; it also regulates several of the chemical messengers involved in memory, such as acetylcholine. At low doses, insulin helps to contain inflammation and, at high doses, stimulates it. Increased insulin concentrations also appear to boost levels of beta-amyloid – a protein involved in the formation of senile plaques that can lead to Alzheimer’s disease. Because inflammation, reduced acetylcholine, and toxic accumulations of beta-amyloid protein are hallmarks of Alzheimer’s disease, insulin insensitivity is one route through which this disease may develop.
Those suffering from Type 2 diabetes and insulin resistance also run a heavy risk of developing impaired memory cognition and increased risk for dementia or memory loss and developing Alzheimer’s disease. Insulin regulates the brain’s supply of dopamine which is a neurotransmitter which helps in attention, reward and motor activity and any disruption or abnormality in insulin’s action can lead to brain disorders and cognitive imbalances in mood and disorders like depression, Parkinson’s disease, schizophrenia, Huntington’s disease and attention-deficit hyperactivity disorder. In the West, cognitive decline is considered very serious because you could forget passwords, secret codes, locker numbers and bank PINs!
Two-way scientific and treatment benefits: There is mounting evidence that scientists from the metabolic and central nervous system (CNS) fields must unite and look at neurodegenerative processes from a different angle, taking into account the evidence generated whilst studying metabolic diseases. Conversely, knowledge generated in CNS labs could contribute to innovative ways to prevent and treat metabolic diseases. Here are some questions that scientific brains and hands together address: a) How do metabolic states affect brain function? b) How can CNS targets expressed in the periphery regulate metabolism? and c) How can anti-diabetic compounds contribute to preventing and treating neurodegenerative diseases?
An ‘executive’ could lose executive function: Since diabetes impairs planning, coordinating, sequencing, and monitoring of cognitive operations, collectively known as ‘executive function’, the so-called ‘business executive’ being a diabetic could end up with loss of executive function. Therefore, it’s important to prevent cognitive decline. Evidence from neurocognitive testing suggests that cognitive dysfunction should be listed as one of the many complications of diabetes. Recently, it is also emphasized that clinicians should consider cognitive function in assessing and guiding their patients regarding safe diabetes self-management regardless of their glycemic targets. If someone asks what’s special about Diabetes Speciality Centres – the answer is this –holistic treatment beyond just glucose control – where the doctor treats physical, metabolic, mental, psychosocial and behavioral aspects of the patient.
There is good news though! Prevention and even reversal of diabetes and obesity related cognitive impairment and depressive mood can be brought about by lifestyle modification. Again and again, scientific research and the medical community emphasize the same slogan: ‘prevent and control diabetes with appropriate lifestyle modification and live a healthy life’, the same wine (message) in a new bottle (evidence). The ‘voice’ should now reach beyond ears – right up to the brain for better cognitive function and best quality of life.