The brain contains more cholesterol than any other organ in the body, has to produce its own cholesterol and won't function normally if it doesn't churn out enough. Defects in cholesterol metabolism have been linked with Alzheimer's disease and other neurodegenerative conditions. Now researchers at Joslin Diabetes Center have discovered that diabetes can affect how much cholesterol the brain can make.
Scientists in the laboratory of C. Ronald Kahn, M.D., head of Joslin's Integrative Physiology and Metabolism research section, found that brain cholesterol synthesis, the only source of cholesterol for the brain, drops in several mouse models of diabetes. Their work was reported online in the journal Cell Metabolism on November 30.
"Since cholesterol is required by neurons to form synapses (connections) with other cells, this decrease in cholesterol could affect how nerves function for appetite regulation, behavior, memory and even pain and motor activity," says Dr. Kahn, who is also Mary K. Iacocca Professor of Medicine at Harvard Medical School. "Thus, this has broad implications for people with diabetes." Other investigations have gathered strong evidence that people with diabetes may display varying types of alterations in brain function or ways of responding to stress, he points out.
"It is well known that insulin and diabetes play an important role in regulating cholesterol synthesis in the liver, where most of the cholesterol circulating in blood comes from," Dr. Kahn adds. "But nobody had ever suspected that insulin and diabetes would play an important role in cholesterol synthesis in the brain."
In addition to its potential role in Alzheimer's disease and other forms of neurological dysfunction, the newly discovered mechanism may play a role in diabetic neuropathy, which remains a large challenge for therapy.
People with diabetes are also known to be more prone to depression, memory loss and eating disorders than people without diabetes, and imaging studies have shown that people with diabetes have altered brain function compared to those without.
Additionally, the finding raises a question about potential interactions between anti-cholesterol drugs and diabetes.
In the Joslin study, scientists first examined gene expression in the hypothalamus of a mouse model of insulin-deficient (type 1) diabetes. They found decreased expression for almost all of the genes of cholesterol synthesis, including a gene called SREBP-2, which acts as a master regulator for cholesterol production. Similar findings were present in the cerebral cortex and other regions of the brain in these animals and also found in several other mouse models of diabetes. In the insulin-deficient animals, this phenomenon was associated with decreased cholesterol synthesis. Treatment of the mice with insulin, either by normal injection or injection into the fluid surrounding the brain, reversed the process.
"Our studies showed that these effects occurred in both the neurons and supporting 'glial' cells that help provide some nutrients to the neurons," says Kahn. "Ultimately this affects the amount of cholesterol that can get into the membranes of the neuron, which form the synapses and the synaptic vesicles—the small structures that contain neurotransmitters."
Additionally, the Joslin work showed a connection between the decrease in brain cholesterol synthesis and appetite. When the scientists took normal mice and temporarily reduced cholesterol creation in the hypothalamus with a technique known as RNA interference, the animals started eating more and gained significant weight. Previous studies by other labs have demonstrated that diabetes may affect brain hormones involved in appetite regulation.
Ryo Suzuki, Ph.D., a postdoctoral researcher in the Kahn lab, is first author on the paper. Other Joslin contributors include Kevin Lee and Enxuan Jing. Other co-authors include Sudha B. Biddinger of Children's Hospital Boston, Jeffrey G. McDonald of the University of Texas Southwestern Medical Center, and Thomas J. Montine and Suzanne Craft of the University of Washington in Seattle. The work was supported by the National Institutes for Health, the Iacocca Foundation and the Manpei Suzuki Diabetes Foundation.
About Joslin Diabetes Center
Joslin Diabetes Center is the world's preeminent diabetes research and clinical care organization. Joslin is dedicated to ensuring that people with diabetes live long, healthy lives and offers real hope and progress toward diabetes prevention and a cure. Founded in 1898 by Elliott P. Joslin, M.D., Joslin is an independent, nonprofit institution affiliated with Harvard Medical School. For more information about Joslin, visit www.joslin.org. Keep up with Joslin research and clinical news at Inside Joslin at www.joslin.org/news/inside_joslin.html, friend Joslin on Facebook at www.facebook.com/joslindiabetes and follow on Twitter at www.twitter.com/JoslinDiabetes.
Eric Bender | EurekAlert!
Could this protein protect people against coronary artery disease?
17.11.2017 | University of North Carolina Health Care
Microbial resident enables beetles to feed on a leafy diet
17.11.2017 | Max-Planck-Institut für chemische Ökologie
The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.
Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...
Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.
That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...
Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.
During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....
The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.
Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...
Pillared graphene would transfer heat better if the theoretical material had a few asymmetric junctions that caused wrinkles, according to Rice University...
15.11.2017 | Event News
15.11.2017 | Event News
30.10.2017 | Event News
17.11.2017 | Physics and Astronomy
17.11.2017 | Health and Medicine
17.11.2017 | Studies and Analyses