Study Explains Link Between Blood Sugar and Alzheimer’s

Scientists have known there is a link between high blood sugar and Alzheimer’s disease—now thanks to a new study published in the journal Scientific Reports, they’re one step closer to learning why this connection exists.

Abnormally high blood sugar levels, or hyperglycemia, occur in diabetes and obesity. People with diabetes are more likely to develop Alzheimer’s disease compared to healthy individuals, but until this new study researchers weren’t sure exactly why. Scientists already knew that glucose and its break-down products can damage proteins in cells through a reaction called glycation, but the specific molecular link between this process and Alzheimer’s was not understood.

Glycation occurs when a sugar molecule binds to a protein or fat molecule. When this happens it leads to a reaction that produces damaging molecules known as advanced glycation end products—AGEs for short.

Glycation causes proteins in the body to stiffen, leading to everything from wrinkled skin to cataracts to hardening of the arteries.

In the current study, conducted by scientists from the University of Bath, researchers tested brain samples from people with and without Alzheimer’s. Using a sensitive technique to detect glycation, the scientists found that in the early stages of Alzheimer’s, glycation harms an important enzyme called MIF (macrophage migration inhibitory factor), which is involved with inflammation response to the early stages of Alzheimer’s.

MIF plays a role in the response of brain cells called glia to the accumulation of abnormal proteins in the brain during Alzheimer’s disease. This study indicates that by blocking MIF activity, glycation could be the “tipping point” in disease progression. As Alzheimer’s disease becomes worse, glycation of these enzymes increases.

“We’ve shown that this enzyme is already modified by glucose in the brains of individuals at the early stages of Alzheimer’s disease,” said Professor Jean van den Elsen, from the University of Bath Department of Biology and Biochemistry. “We are now investigating if we can detect similar changes in blood. Normally MIF would be part of the immune response to the build-up of abnormal proteins in the brain, and we think that because sugar damage reduces some MIF functions and completely inhibits others that this could be a tipping point that allows Alzheimer’s to develop.”

Dr. Rob Williams, also from the Department of Biology and Biochemistry, added: “Knowing this will be vital to developing a chronology of how Alzheimer’s progresses and we hope will help us identify those at risk of Alzheimer’s and lead to new treatments or ways to prevent the disease.”

Worldwide, about 50 million people have Alzheimer’s disease. This number is expected to rise to more than 125 million by 2050. Globally, the social cost of Alzheimer’s amounts to the hundreds of billions of dollars because patients not only require both medical and social care because of the cognitive impairment associated with the disease.

“Excess sugar is well known to be bad for us when it comes to diabetes and obesity,” said Dr. Omar Kassaar, from the University of Bath, “but this potential link with Alzheimer’s disease is yet another reason that we should be controlling our sugar intake in our diets.

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