new alteration in the brain of people with Alzheimer's discovered

September 18, 2020

Despite the important advances in research in recent years, the etiopathogenesis of Alzheimer's disease is still not fully clarified. One of the key questions is to decipher why the production of beta amyloid, the protein that produces the toxic effect and triggers the pathology, increases in the brain of people with Alzheimer's.

The research has focused on the different fragments of the Amyloid Precursor Protein (APP) until now, but the results have been inconclusive, "because this protein is processed so quickly that its levels in the cerebrospinal fluid or in the plasma do not reflect what is really happening in the brain," explains Dr. Javier Sáez-Valero, head of the group on "Altered Molecular Mechanisms in Alzheimer's Disease and other Dementias" at the UMH-CSIC Neuroscience Institute in Alicante.

Dr. Sáez-Valero's laboratory has carried out a novel approach that shows great promise: "We have discovered that the glycosylation of the amyloid precursor in the brain of Alzheimer's patients is altered. And, therefore, this protein is probably being processed in a different way. We believe that this different way of processing leads to more beta-amyloid, and to the triggering of the pathology".

Glycosylation consists of adding carbohydrates to a protein. This process determines the destiny of the proteins to which a sugar chain (glycoproteins) has been added, which will be secreted or will form part of the cellular surface, as in the case of the Amyloid Precursor Protein (APP). The alteration of this glycosylation process is related with the origin of various pathologies.

In the specific case of Alzheimer's, the results of the study led by Sáez Valero suggest that the altered glycosylation could determine that the APP is processed by the amyloidogenic (pathological) pathway, giving rise to the production of the beta-amyloid, a small protein with a tendency to cluster forming the amyloid plaques characteristic of Alzheimer's disease.

"The fact that the glycosylation of the amyloid precursor is altered indicates that this amyloid precursor may be located into areas of the cell membrane that are different from the usual, interacting with other proteins and therefore probably being processed in a pathological way," clarifies this expert in Alzheimer's disease.

With this new finding of Dr. Saez-Valero's group, published in Alzheimer's Research & Therapy, "analyzing the glycosylation of beta-amyloid fragments opens the possibility of finding a good biomarker for diagnosis in the short term. And in the longer term to intervene therapeutically".

Previously, amyloid fragments of APP had been studied in the cerebrospinal fluid for these purposes, "but the results did not indicate that it could be a good diagnostic marker. However, in view of our new results, we propose to repeat the studies carried out to date not only by looking at the different types of fragments of the beta-amyloid protein, but also at its glycosylation," highlights Sáez-Valero.

The presence of the beta-amyloid protein in the cerebrospinal fluid does not provide much information at present either, "since in the brain this small protein forms amyloid plaques, thus, the paradox is that in the cerebrospinal fluid there are lower levels than would be expected," explains Sáez-Valero.

The other option is to study the long fragments of the APP, "but they are processed so quickly that they do not really reflect anything pathological. However, looking at the glycosylation we have seen that, although the total levels are not altered, there is an indication that the protein is synthesized differently and therefore can be processed in a different way, giving rise to the toxic cascade that triggers Alzheimer's disease," this expert points out.

This work has been carried out on post-mortem brain samples and on cell cultures. The next step will be to analyze the glycosylation of the app fragments in the cerebrospinal fluid. "Right now we have a new tool that can be used in the short term for biochemical diagnosis of Alzheimer's patients in the laboratory," concludes Dr. Sáez-Valero.
-end-


Spanish National Research Council (CSIC)

Related Brain Articles from Brightsurf:

Glioblastoma nanomedicine crosses into brain in mice, eradicates recurring brain cancer
A new synthetic protein nanoparticle capable of slipping past the nearly impermeable blood-brain barrier in mice could deliver cancer-killing drugs directly to malignant brain tumors, new research from the University of Michigan shows.

Children with asymptomatic brain bleeds as newborns show normal brain development at age 2
A study by UNC researchers finds that neurodevelopmental scores and gray matter volumes at age two years did not differ between children who had MRI-confirmed asymptomatic subdural hemorrhages when they were neonates, compared to children with no history of subdural hemorrhage.

New model of human brain 'conversations' could inform research on brain disease, cognition
A team of Indiana University neuroscientists has built a new model of human brain networks that sheds light on how the brain functions.

Human brain size gene triggers bigger brain in monkeys
Dresden and Japanese researchers show that a human-specific gene causes a larger neocortex in the common marmoset, a non-human primate.

Unique insight into development of the human brain: Model of the early embryonic brain
Stem cell researchers from the University of Copenhagen have designed a model of an early embryonic brain.

An optical brain-to-brain interface supports information exchange for locomotion control
Chinese researchers established an optical BtBI that supports rapid information transmission for precise locomotion control, thus providing a proof-of-principle demonstration of fast BtBI for real-time behavioral control.

Transplanting human nerve cells into a mouse brain reveals how they wire into brain circuits
A team of researchers led by Pierre Vanderhaeghen and Vincent Bonin (VIB-KU Leuven, Université libre de Bruxelles and NERF) showed how human nerve cells can develop at their own pace, and form highly precise connections with the surrounding mouse brain cells.

Brain scans reveal how the human brain compensates when one hemisphere is removed
Researchers studying six adults who had one of their brain hemispheres removed during childhood to reduce epileptic seizures found that the remaining half of the brain formed unusually strong connections between different functional brain networks, which potentially help the body to function as if the brain were intact.

Alcohol byproduct contributes to brain chemistry changes in specific brain regions
Study of mouse models provides clear implications for new targets to treat alcohol use disorder and fetal alcohol syndrome.

Scientists predict the areas of the brain to stimulate transitions between different brain states
Using a computer model of the brain, Gustavo Deco, director of the Center for Brain and Cognition, and Josephine Cruzat, a member of his team, together with a group of international collaborators, have developed an innovative method published in Proceedings of the National Academy of Sciences on Sept.

Read More: Brain News and Brain Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.