Are memory loss and mood disorders actually diabetes of the brain?

An excerpt from Feed Your Brain Lose Your Belly.

by Larry McCleary, MD

As diseases, memory loss and mood disorders appear to have very little in common. But could memory loss (even severe memory loss such as that which occurs in Alzheimer’s disease) and mood illnesses such as depression and bipolar disorder, actually be treated much the same as diabetes?

Recent thought provoking research findings suggest that this might be the case. They provide a common link suggesting that insulin plays a central role in each of these conditions and that addressing related metabolic imbalances in the brain could revolutionize future medical treatments for all of them.

The most common dementing disorder is Alzheimer’s disease, which currently affects 5 million Americans and accounts for well over $100 Billion in direct health care costs. Even though it was first identified over 100 years ago, there is still no effective treatment today. It doubles in prevalence every five years after age 65, and 50% of individuals who reach their 85th birthday are afflicted.

Mood disorders – a major cause of disability and one of the primary factors in missed days from work – are essentially no more responsive to modern drug intervention than they were in the 1950s.

However, if recent scientific findings are confirmed, this is about to change dramatically. Suzanne Craft and her associates in Seattle, Washington and Roger McIntyre and his group in Toronto have literally treated patients with both conditions as if their brains had diabetes. They provided insulin (the same hormone injected by diabetics to control blood sugar levels) that was delivered through a nasal inhaler several times a day.

Doctors who treat patients with diabetes – a condition that is defined by specific insulin problems – have also noted a much higher incidence of memory, thinking and mood disorders in their patients. Since there are insulin abnormalities in the bodies of diabetics and other overweight and obese subjects who experience a much higher incidence of these specific brain problems, it would be no surprise if the same were true in the brain.

The same insulin processing problems seen in the brains of those suffering from AD and an array of mood disorders are also noted in patients who are overweight or diabetic. What is particularly striking is that identical insulin problems have been identified in the brains of subjects with Alzheimer’s disease, depression and bipolar disorder who are otherwise healthy and fit! That could be the common chemical malfunction that unites these disparate diseases and might provide a vital clue for a host of future therapies based on a novel new mechanism of disease.

Currently, treatments are based on postulated malfunctions in various brain-signaling pathways (acetylcholine in Alzheimer’s disease and serotonin or norepinephrine in depressive disorders). New therapeutic options may now be visualized that are designed to enhance brain metabolism and optimize insulin function in the brain – foreshadowing a new frontier in how we think about brain disorders.

Glucose, the primary sugar in our blood, is what becomes problematic when diabetes develops. However, without glucose life as we know it would not exist. In overweight diabetics glucose loses its ability to enter and be processed properly by cells throughout the body. A similar disturbance occurs in the brains of patients with Alzheimer’s disease and is associated with changes that can be detected on sensitive brain scans decades before symptoms such as memory loss are observed.

The existence and distribution of these characteristic findings are so typical that they can be used to predict subsequent deterioration. Neuroscientists have even referred to this inability of the brain to use glucose as brain starvation. Since insulin delivered through nasal inhalers easily passes into the brain without entering the bloodstream, it doesn’t create havoc with blood sugar control. Once within the brain it is able to correct many of the associated insulin-signaling abnormalities and improve symptoms such as memory loss, concentration, focus and depression.

These results have not been overlooked by drug companies. Numerous studies using current diabetes medications as therapeutic modalities for an array of brain disorders are already in progress. Many new drug candidates designed to enhance the effect of insulin in the brain are also in the pipeline.

From a purely research and educational perspective, these observations have stimulated numerous investigations designed to evaluate the expanding role insulin plays in brain development, cognitive function, brain aging and recovery from central nervous system insults such as head trauma, stroke and cancer.

It appears that the future is now when it comes to the interaction between insulin and the brain. Insulin is no longer considered to be merely the hormone that controls blood sugar. It is now known to be intimately involved in heart disease, hypertension, cholesterol metabolism and inflammation throughout the body. Its role in brain health is just starting to be appreciated. When we better understand the diverse effects it has throughout the brain and body, we will have more effective treatments for many of the health scourges that plague us today. Insulin pathways have also been demonstrated to play central roles in the aging process – another potential field of scientific investigation.

From a more personal perspective, the proper regulation of insulin is directly under our control each time we make a lifestyle choice, whether it be what to eat, how much to eat, whether or not to smoke or to exercise, to avoid unremitting stress or to burn the candle at both ends. These decisions have a greater impact on avoiding insulin problems than the most potent drugs available. We must merely take the time to control the factors that are most easily influenced – those we make each and every day – to keep our brains and bodies healthy.

Larry McCleary is the retired Acting Chief of Neurosurgery at Denver’s Children’s Hospital, and author of Feed Your Brain Lose Your Belly.  He can be reached at his self-titled site, Dr. McCleary.

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