December 15, 2014
A novel blood test offers hope for diagnosing Alzheimer’s at its earliest stages, up to 10 years before symptoms like memory loss and confusion take hold. The test needs additional study but, if proven effective, could be useful for identifying those with Alzheimer’s at a stage when drugs and other therapies are potentially most effective.
In a preliminary study, the test effectively distinguished those with Alzheimer’s from their healthy peers and was more accurate than other blood tests currently under investigation. The new test was studied in 174 seniors, 70 of whom had Alzheimer’s disease. More extensive testing in larger numbers of people will be needed to confirm the results.
The test measures insulin resistance, or abnormalities in the hormone insulin, in the brain. Insulin is critical for the body’s ability to process glucose, or blood sugar, which supplies energy to muscles and cells throughout the body, including in the brain. Insulin resistance and impaired glucose metabolism are a hallmark of diabetes, a disease that is also known to raise the risk for dementia.
“This study shows that insulin resistance is a major central nervous system metabolic abnormality in Alzheimer’s disease,” said Dr. Ed Goetzl, the senior author of the study. “As insulin resistance is a known condition in type 2 diabetes mellitus and is treatable with several classes of existing drugs, these treatments may be useful as part of a multi-agent program for Alzheimer’s disease.”
For the study, published in The FASEB Journal, The Journal of the Federation of American Societies for Experimental Biology, researchers studied what are known as exosomes, or tiny membrane-encased bubbles of chemicals that are released from cells into blood, urine or other fluids. In this case, researchers looked at exosomes that are shed from brain cells into the blood.
The researchers compared markers of insulin resistance in the exosomes of the 70 patients with Alzheimer’s to those from 84 healthy men and women of a similar age, as well as 20 people who had diabetes. The test was able to distinguish all of the patients with Alzheimer’s disease, and almost all of the patients with diabetes.
The researchers also found that the more advanced the Alzheimer’s, the greater the evidence of insulin resistance in the brain.
If confirmed, the test could be used to diagnose Alzheimer’s at a very early stage, when drugs may be most effective. Insulin changes in the brain could also be used to test whether new drugs are effective in reducing progression of disease. Current therapies for Alzheimer’s do little to stop the downward spiral of disease, and new treatments are urgently needed.
Source: Dimitrios Kapogiannis, Adam Boxer, Janice B. Schwartz, et al: “Dysfunctionally phosphorylated type 1 insulin receptor substrate in neural-derived blood exosomes of preclinical Alzheimer’s disease.” The FASEB Journal – The Journal of the Federation of American Societies for Experimental Biology. FASEB J fj.14-262048; published ahead of print October 23, 2014, doi:10.1096/fj.14-262048