Posts tagged glucose metabolism
Articles and news from the latest research reports.
Combination of Two Imaging Techniques Allows New Insights into Brain Function
The ability to measure brain functions non-invasively is important both
for clinical diagnoses and research in Neurology and Psychology. Two main imaging techniques are used: positron emission tomography (PET), which reveals metabolic processes in the brain; and activity of different brain regions is measured on the basis of the cells’ oxygen consumption by magnetic resonance imaging (MRI). A direct comparison of PET and MRI measurements was previously difficult because each had to be performed in a separate machine.
Researchers from the Werner Siemens Imaging Center at the University of Tübingen under the direction of Professor Bernd J. Pichler in collaboration with the Department of Diagnostic and Interventional Radiology, University Hospital Tübingen, and the Tübingen Max Planck Institute for Intelligent Systems have now successfully combined both methods. The researchers are able to explore functional processes in the brain in detail and can better assess what course of action to take. These results were achieved by the use of a PET insert enabling complementary, simultaneous PET/MRI scans. It was developed and built at the University of Tübingen.
The researchers could identify in certain regions a mismatch between glucose metabolism related brain activation measured with PET and oxygenation related signals, measured with MRI. Furthermore information about functional connectivity in the brain could be derived from MRI and from dynamic PET data. These results help to further decipher the nature of brain function, and are ultimately useful for basic research as well as clinical practice. The study, by lead author Dr. Hans Wehrl of Professor Bernd J. Pichler’s research team is soon to be published in the journal “Nature Medicine”.
In PET imaging the distribution of a weakly radioactive substance is shown in cross sections of the body, enabling doctors to see many different metabolic and physiological functions at work. Functional MRI (fMRI) allows researchers to depict changes in blood oxygenation that are associated with brain function. This measurement of functional active brain regions is also important for the planning of brain surgeries, where particular care must be taken in certain areas. The ability to collect different kinds of data from different scans simultaneously represents a major step forward in the fields using these technologies.
(Source: alphagalileo.org)
In a National Institutes of Health (NIH) funded clinical trial, researchers at Emory have discovered that specific patterns of brain activity may indicate whether a depressed patient will or will not respond to treatment with medication or psychotherapy. The study was published June 12, 2013, in JAMA Psychiatry Online First.
The choice of medication versus psychotherapy is often based on the preference of the patient or clinician, rather than objective factors. On average, only 35-40 percent of patients get well with whatever treatment they start with.
"To be ill with depression any longer than necessary can be perilous," says Helen Mayberg,md principal investigator for the study and professor of psychiatry, neurology and radiology at Emory University School of Medicine. "This is a serious illness and the prolonged suffering resulting from an ineffective treatment can have serious medical, personal and social consequences. Our goal is not just to get patients well, but to get them well as fast as possible, using the treatment that is best for each individual."
Mayberg’s positron emission tomography (PET) studies over the years have given clues about what may be going on in the brain when people are depressed, and how different treatments affect brain activity.
These studies have also suggested that scan patterns prior to treatment might provide important clues as to which treatment to choose. In this study, the investigators used PET scans to measure brain glucose metabolism, an important index of brain functioning to test this hypothesis.
Participants in the trial were randomly assigned to receive a 12-week course of either the SSRI medication escitalopram or cognitive behavior therapy (CBT) after first undergoing a pretreatment PET scan.
The team found that activity in one particular region of the brain, the anterior insula, could discriminate patients who recovered from those who were non-responders to the treatment assigned. Specifically, patients with low activity in the insula showed remission with CBT, but poor response to medication; patients with high activity in the insula did well with medication, and poorly with CBT.
"These data suggest that if you treat based on a patient’s brain type, you increase the chance of getting them into remission," says Mayberg.
Mayberg is quick to add that this approach needs to be replicated before it would be appropriate for routine treatment selection decisions for individual depressed patients. It is, however, a first step to better define different types of depression that can be used to select a specific treatment for a patient.
A treatment stratification approach is done routinely in the management of other medical conditions such as infections, cancer, and heart disease, notes Mayberg. “The study reported here provides important first results towards the development of brain-based treatment algorithms that match a patient to the treatment with the highest likelihood of success, while also avoiding those treatments that will be ineffective.”
Is There a Period of Increased Vulnerability for Repeat Traumatic Brain Injury?
Repeat traumatic brain injury affects a subgroup of the 3.5 million people who suffer head trauma each year. Even a mild repeat TBI that occurs when the brain is still recovering from an initial injury can result in poorer outcomes, especially in children and young adults. A metabolic marker that could serve as the basis for new mild TBI vulnerability guidelines is described in an article in Journal of Neurotrauma, a peer-reviewed journal from Mary Ann Liebert, Inc., publishers. The article is available on the Journal of Neurotrauma website.
In an Editorial, “The Window of Risk in Repeated Head Injury,” accompanying this article, John T. Povlishock, PhD, Editor-in-Chief of Journal of Neurotrauma and Professor, VCU Neuroscience Center, Medical College of Virginia, Richmond, states that recent studies of TBI in animal models have shown that while repeat injury can exacerbate structural, functional, metabolic, and behavioral responses, “these responses only occur when the injury is repeated within a specific time frame post-injury.”
"Specifically, this window of risk is greatest when the interval between injuries is short, hours to days, while any risk for increased damage is obviated when the intervals between injuries are elongated over days to weeks," says Dr. Povlishock. It is not yet clear if these time periods of increased risk are age- or gender-specific or depend on the intensity of the initial injury.
A consistent finding following TBI in both humans and animal models is a decrease in glucose uptake by the brain. Mayumi Prins, Daya Alexander, Christopher Giza, and David Hovda, The UCLA Brain Injury Research Center, Los Angeles, CA, simulated single and repeat (after 1 or 5 days) mild TBI in rats and measured cerebral glucose metabolism. They tested the hypothesis that the rats’ brains would be more vulnerable to the damaging effects of repeat TBI at 1 day post-injury, when glucose metabolism was still decreased, than at 5 days, when it had returned to normal levels.
In the article, “Repeat Mild Traumatic Brain Injury: Mechanisms of Cerebral Vulnerability,” the authors propose that the duration of metabolic slowdown in the brain could serve as a valuable biomarker for how long a child might be at increased risk of repeat TBI.