University of Cincinnati researchers hypothesize that low levels of amyloid-beta protein, not amyloid plaques, are to blame
New research from the University of Cincinnati (UC) and Karolinska Institute in Sweden challenges the prevailing theory about the causes of Alzheimer’s disease, suggesting the possibility of new avenues for the development of effective clinical laboratory assays, as well as effective therapies for treating patients diagnosed with Alzheimer’s.
Scientists have long theorized that the disease is caused by a buildup of amyloid plaques in the brain. These plaques are hardened forms of the amyloid-beta protein, according to a UC news story.
“The paradox is that so many of us accrue plaques in our brains as we age, and yet so few of us with plaques go on to develop dementia,” said Alberto Espay, MD, one of the lead researchers of the study, in another UC news story. Espay is Professor of Neurology at the UC College of Medicine and Director and Endowed Chair of the Gardner Center for Parkinson’s Disease and Movement Disorders.
“Yet the plaques remain the center of our attention as it relates to biomarker development and therapeutic strategies,” he added.
“It’s only too logical, if you are detached from the biases that we’ve created for too long, that a neurodegenerative process is caused by something we lose, amyloid-beta, rather than something we gain, amyloid plaques,” said Alberto Espay, MD (above), in a University of Cincinnati news story. “Degeneration is a process of loss, and what we lose turns out to be much more important.” The UC study could lead to new clinical laboratory diagnostics, as well as treatments for Alzheimer’s and Parkinson’s diseases. (Photo copyright: University of Cincinnati.)
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High Levels of Aβ42 Associated with Lower Dementia Risk
In their retrospective longitudinal study, the UC researchers looked at clinical assessments of individuals participating in the Dominantly Inherited Alzheimer Network (DIAN) cohort study. DIAN is an ongoing effort, sponsored by the Washington University School of Medicine in St. Louis, to identify biomarkers associated with Alzheimer’s among people who carry Alzheimer’s mutations.
The researchers found that study participants with high levels of a soluble amyloid-beta protein, Aβ42, were less likely to develop dementia than those with lower levels of the protein, regardless of the levels of amyloid plaques in their brains or the amount of tau protein—either as phosphorylated tau (p-tau) or total tau (t-tau)—in their cerebral spinal fluid. P-tau and t-tau are proteins that form “tau tangles” in the brain that are also associated with Alzheimer’s.
One limitation of the study was that the researchers were unable to include Aβ40, another amyloid-beta protein, in their analysis. But they noted that this “did not limit the testing of our hypothesis since Aβ40 exhibits lower fibrillogenicity and lesser depletion than Aβ42, and is therefore less relevant to the process of protein aggregation than Aβ42.” Fibrillogenicity, in this context, refers to the process by which the amyloid-beta protein hardens into plaque.
While the presence of plaques may be correlated with Alzheimer’s, “Espay and his colleagues hypothesized that plaques are simply a consequence of the levels of soluble amyloid-beta in the brain decreasing,” UC news stated. “These levels decrease because the normal protein, under situations of biological, metabolic, or infectious stress, transform into the abnormal amyloid plaques.”
The UC News story also noted that many attempts to develop therapeutics for Alzheimer’s have focused on reducing amyloid plaques, but “in some clinical trials that reduced the levels of soluble amyloid-beta, patients showed worsening in clinical outcomes.”
New Therapeutics for Multiple Neurodegenerative Diseases
Eisai, a Japanese pharmaceutical company, recently announced phase three clinical trial results of lecanemab, an experimental drug jointly developed by Eisai and Biogen, claiming that the experimental Alzheimer’s drug modestly reduced cognitive decline in early-stage patients, according to NBC News.
Espay noted that lecanemab “does something that most other anti-amyloid treatments don’t do in addition to reducing amyloid: it increases the levels of the soluble amyloid-beta.” That may slow the process of soluble proteins hardening into plaques.
Beyond their findings about Alzheimer’s, the researchers believe similar mechanisms could be at work in other neurodegenerative diseases such as Parkinson’s disease, where the soluble alpha-synuclein protein also hardens into deposits.
“We’re advocating that what may be more meaningful across all degenerative diseases is the loss of normal proteins rather than the measurable fraction of abnormal proteins,” Espay said. “The net effect is a loss not a gain of proteins as the brain continues to shrink as these diseases progress.”
Espay foresees two approaches to treating these diseases: Rescue medicine, perhaps based on increasing levels of important proteins, and precision medicine, which “entails going deeper to understand what is causing levels of soluble amyloid-beta to decrease in the first place, whether it is a virus, a toxin, a nanoparticle, or a biological or genetic process,” according to UC News. “If the root cause is addressed, the levels of the protein wouldn’t need to be boosted because there would be no transformation from soluble, normal proteins to amyloid plaques.”
Clinical Laboratory Impact
What does this mean for clinical laboratories engaged in treatment of both Alzheimer’s and Parkinson’s patients? A new understanding of the disease would create “the opportunity to identify new biomarkers and create new clinical laboratory tests that may help diagnose Alzheimer’s earlier in the disease progression, along with tests that help with the patient’s prognosis and monitoring his or her progression,” said Robert Michel, Editor-in-Chief of Dark Daily and its sister publication The Dark Report.
Given the incidence of Alzheimer’s disease in the population, any clinical laboratory test cleared by the FDA would be a frequently-ordered assay, Michel noted. It also would create the opportunity for pathologists and clinical laboratories to provide valuable interpretation about the test results to the ordering physicians.
Technologies developed by Pääbo to sequence Neanderthal DNA are being widely used in many clinical laboratory settings, including to study infectious disease outbreaks
Pääbo is considered to be the founder of paleogenetics. This field of science studies the past through examination of preserved genetic material found in remains of ancient organisms. It was his development of pioneering technologies that allowed for the genomic sequencing of Neanderthal DNA.
“[Pääbo’s] work has revolutionized our understanding of the evolutionary history of modern humans,” said German electrochemist Martin Stratmann, PhD, President of the Max Planck Society for the Advancement of Science (MPG), in a press release. “Svante Pääbo, for example, demonstrated that Neanderthals and other extinct hominids made a significant contribution to the ancestry of modern humans.”
“The thing that’s amazing to me is that you now have some ability to go back in time and actually follow genetic history and genetic changes over time,” Svante Pääbo, PhD (above), director of the Max Planck Institute for Evolutionary Anthropology, stated in a news conference, Reuters reported. “It’s a possibility to begin to actually look on evolution in real time, if you like.” Development of modern clinical laboratory techniques for identifying and tracking disease outbreaks have already evolved due to these findings. (Photo copyright: Max Planck Institute for Evolutionary Anthropology.)
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Comparing Neanderthal DNA to That of Modern Humans
Back in the mid-1990s, Pääbo and a team of researchers decoded relatively short fragments of mitochondrial DNA of a Neanderthal male. They discovered through their analysis that the DNA from the Neanderthal varied considerably from the genome of contemporary humans. This validated the belief that modern humans are not direct descendants of the Neanderthals.
Pääbo’s research team found nearly all (99.9%) of the Neanderthal DNA they studied to be heavily colonized by bacteria and fungi. That required them to create solutions for assembling the short components of mitochondrial DNA like a huge puzzle.
To accomplish this, the team had to:
Work under clean room conditions to prevent the accidental introduction of their own DNA into their experiments.
Establish more efficient extraction methods to enhance the output of Neanderthal DNA.
Generate complex computer programs that could compare the ancient DNA fragments with reference genomes of both humans and chimpanzees.
“Neanderthals are the closest relatives of humans today” said Pääbo in the press release. “Comparisons of their genomes with those of modern humans and with those of apes enable us to determine when genetic changes occurred in our ancestors. In the future, it could also be clarified why modern humans eventually developed a complex culture and technology that enabled them to colonize almost the entire world.”
Pääbo’s team succeeded in reconstructing their first version of the Neanderthal genome in 2010. Their comparisons between the genomes of Neanderthal and modern humans proved that the two groups had produced common offspring about 50,000 years ago and that this genetic contribution did influence human evolution.
The genome of modern non-African people still contains about 2% Neanderthal DNA.
“We have found around 30,000 positions in which the genomes of almost all modern humans differ from those of Neanderthals and great apes,” Pääbo added. “They answer what makes anatomically modern humans ‘modern’ in the genetic sense as well. Some of these genetic changes may be the key to understanding what distinguishes the cognitive abilities of today’s humans from those of now extinct hominids.”
Those with Neanderthal DNA More Susceptible to Severe COVID-19 Infection
Pääbo’s research also found that Neanderthal DNA may have affected the immune systems of modern people. During the COVID-19 pandemic, his work verified that individuals who carry a gene variant inherited from Neanderthals are more prone to severe forms of the illness than those who do not have that gene variant.
“We can make an average gauge of the number of the extra deaths we have had in the pandemic due to the contribution from the Neanderthals,” Pääbo said in a 2022 lecture, Reuters reported. “It is quite substantial, it’s more than one million extra individuals who have died due to this Neanderthal variant that they carry.”
Pääbo’s research team continues to develop new methods for reconstructing DNA fragments that are even more biodegraded, and which present in smaller amounts. Their ultimate goal is to investigate even older DNA and genetic material that is scarce due to climate conditions.
The DNA technologies pioneered by Pääbo to sequence Neanderthal DNA are being used widely in many clinical laboratory and research settings today. They include forensic science and the ability to collect DNA from human remains hundreds of years old to identify infectious disease outbreaks and study how today’s human genome has adopted new mutations.
Teams from multiple Swedish organizations are investigating the relationship of protein-coding genes to antibodies
Scientists in Sweden are discovering new ways to map the expression of genes in cells, tissues, and organs within the human body thanks to advances in molecular profiling. Their study has successfully combined the analysis of single-cell transcriptomics with spatial antibody-based protein profiling to produce a high-resolution, single-cell mapping of human tissues.
The data links protein-coding genes to antibodies, which could help researchers develop clinical laboratory tests that use specific antibodies to identify and target infectious disease. Might this also lead to a new menu of serology tests that could be used by medical laboratories?
This research is another example of how various databases of genetic and proteomic information—different “omics”—are being combined to produce new understanding of human biology and physiology.
In a Human Protein Atlas (HPA) project press release, Director of the HPA consortium and Professor of Microbiology at Royal Institute of Technology in Stockholm, Mathias Uhlén, PhD, said, “The [Science Advances] paper describes an important addition to the Human Protein Atlas (HPA) which has become one of the world’s most visited biological databases, harboring millions of web pages with information about all the human protein coding genes.”
“We are excited that the new open-access Single Cell Type section constitutes a unique resource for studying the cell type specificity and exact spatial localization of all our proteins”, said Cecilia Lindskog, PhD (above), Head of the HPA Tissue Atlas and Associate Professor, Experimental Pathology, Uppsala University, in the Protein Atlas press release. Medical laboratories may soon have new serology tests to perform that were developed based on HPA data. (Photo copyright: Human Uterus Cell Atlas.)
Distinct Expression Clusters Consistent to Similar Cell Types
To perform their research, the scientists mapped the gene expression profile of all protein-coding genes across different cell types. Their analysis showed that there are distinct expression clusters which are consistent to cell types sharing similar functions within the same organs and between organs of the human body.
The scientists examined data from non-diseased human tissues and organs using three main criteria:
Publicly available raw data from human tissues containing good technical quality with at least 4,000 cells analyzed and at least 20 million read counts by the sequencing for each tissue.
High correlation between pseudo-bulk transcriptomics profile from the scRNA-Seq data and bulk RNA-Seq generated as part of the Human Protein Atlas (HPA).
High correlation between the cluster-specific expression and the expected expression pattern of an extensive selection of marker genes representing well-known tissue- and cell type-specific markers, including both markers from the original publications and additional markers used in pathology diagnostics.
According to the HPA press release, “across all analyzed cell types, almost 14,000 genes showed an elevated expression in particular cell types, out of which approximately 2,000 genes were found to be specific for only one of the cell types.”
The press release also states, “cell types in testis showed the highest numbers of cell type elevated genes, followed by ciliated cells. Interestingly, only 11% of the genes were detected in all analyzed cell types suggesting that the number of essential genes (‘house-keeping’) are surprisingly few.”
Omics-based Biomarkers for Accurate Diagnosis of Disease
The Human Protein Atlas is the largest and most comprehensive database for spatial distribution of proteins in human tissues and cells. It provides a valuable tool for researchers who study and analyze protein localization and expression in human tissues and cells.
Ongoing improvements in gene sequencing technologies are making research of genes more accurate, faster, and more economical. Advances in gene sequencing also could help medical professionals discover more personalized care for patients leading to improved outcomes. A key goal of precision medicine.
One of the conclusions to be drawn from this work is that clinical laboratories and anatomic pathology groups will need to be able to handle immense amounts of data, while at the same time having the capabilities to analyze that data and identify useful patterns that can help diagnose patients earlier and more accurately.
The study ‘shows that measurement using a urine test provides improved accuracy relative to other measurement methods, for example certain kinds of blood tests,’ a KI news release states
Researchers at the Karolinska Institute (KI) in Sweden have developed a non-invasive urine-based test that can identify what type of asthma a patient has and its severity. If developed into a clinical laboratory diagnostic, such a test also could give clinicians a better idea of what treatment is more likely to be effective—a core goal of precision medicine.
Another benefit of this methodology is that it is a non-invasive test. Should further studies conclude that this urine-based test produces accurate results acceptable for clinical settings, medical laboratories would certainly be interested in offering this assay, particularly for use in pediatric patients who are uncomfortable with the venipunctures needed to collect blood specimens. Also, given the incidence of asthma in the United States, there is the potential for a urine-based asthma test to generate a substantial number of test requests.
The objective of the study, according to the Karolinska Institute researchers, was “To test if urinary eicosanoid metabolites can direct asthma phenotyping.” The team used mass spectrometry to measured certain lipid biomarkers (prostaglandins and leukotrienes), which are known to play a key role in the inflammation that occurs during asthma attacks.
According to a KI news release, “The study is based on data from the U-BIOPRED study (Unbiased BIOmarkers in PREDiction of respiratory disease outcomes), which was designed to investigate severe asthma. The study included 400 participants with severe asthma, which often requires treatment with corticosteroid tablets, nearly 100 individuals with milder forms of asthma, and 100 healthy control participants.”
“We discovered particularly high levels of the metabolites of the mast cell mediator prostaglandin D2 and the eosinophil product leukotriene C4 in asthma patients with what is referred to as Type 2 inflammation. Using our methodology, we were able to measure these metabolites with high accuracy and link their levels to the severity and type of asthma,” said Johan Kolmert, PhD (above), a post-doctoral researcher at the Institute of Environmental Medicine, Karolina Institute, and first author of the study, in the KI news release. If perfected, such accuracy could lead to effective precision medicine clinical laboratory tests. (Photo copyright: Karolinska Institute.)
More Accurate Testing Could Lead to Biomarker-guided Precision Medicine
In the US alone, 25,131,132 people currently suffer from asthma, about five million of which are children under the age of 18, according to 2019 CDC statistics. The World Health Organization (WHO) reports that worldwide, “Asthma affected an estimated 262 million people in 2019 and caused 461,000 deaths.”
People with mild asthma may have good success using steroid inhalers. However, for those with moderate to severe asthma where inhalers are not effective, oral corticosteroids may also be necessary. But corticosteroids have been associated with high blood pressure and diabetes, among other negative side effects.
“To replace corticosteroid tablets, in recent times several biological medicines have been introduced to treat patients with Type 2 inflammation characterized by increased activation of mast cells and eosinophils,” said Sven-Erik Dahlén, Professor at the Institute of Environmental Medicine, Karolinska Institute, in the news release.
Currently, there are no simple tests that show what type of asthma a patient has. Instead, clinicians rely on lung function tests, patient interviews, allergy tests, and blood tests.
Earlier this year, researchers at Brigham and Women’s Hospital and Exosome Diagnostics in Massachusetts investigated a non-invasive, urine-based test for transplant rejection. According to a news release, “Patients can spend up to six years waiting for a kidney transplant. Even when they do receive a transplant, up to 20% of patients will experience rejection.”
“If rejection is not treated, it can lead to scarring and complete kidney failure. Because of these problems, recipients can face life-long challenges,” said Jamil Azzi, MD, Director of the Kidney Transplantation Fellowship Program at Brigham and Women’s Hospital, and Associate Professor of Medicine at Harvard School of Medicine. “Our goal is to develop better tools to monitor patients without performing unnecessary biopsies. We try to detect rejection early, so we can treat it before scarring develops,” he said.
Detecting Bladder Cancer with Urine Testing
Another condition where urine tests are being investigated is bladder cancer. An article in Trends in Urology and Men’s Health states, “Several point-of-care urine tests have been developed to help identify patients who may be at higher risk of bladder cancer.” Those tests could have the potential for use in primary care, which could mean fewer people would need invasive, painful, and risk-carrying cystoscopies.
“New tests to help identify hematuria patients who are at a higher risk of cancer would help to improve the diagnostic pathway, reduce the number diagnosed by emergency presentation, lessen the burden on urology services, and spare those who do not have cancer an invasive and costly examination, such as cystoscopy,” the article’s authors wrote.
These urine-based tests are still under investigation by various research teams and more research is needed before clinical trials can be conducted and the tests can be submitted for regulatory approval. Though still in the early stages of development, urine-based diagnostic testing represents far less invasive, and therefore safer, ways to identify and treat various diseases.
Studies into how the elements in urine might be used as biomarkers for clinical laboratory tests may lead to improved non-invasive precision medicine diagnostics that could save many lives.
About 50% of South Asians and 16% of Europeans carry gene cluster associated with respiratory failure after SARS-CoV-2 infection and hospitalization
Clinical pathology laboratories and medical laboratory scientists may be intrigued to learn that scientists from two research institutes in Germany and Sweden have determined that a strand of DNA associated with a higher risk of severe COVID-19 in humans is similar to the corresponding DNA sequences of a roughly 50,000-year-old Neanderthal from Croatia.
The researchers concluded that this gene cluster—passed down from Neanderthals to homo sapiens—triples the risk of developing severe COVID-19 respiratory symptoms for some modern day humans.
In a press release, Pääbo said, “It is striking that the genetic heritage from the Neanderthals has such tragic consequences during the current pandemic. Why this is must now be investigated as quickly as possible.”
Might Useful Biomarkers for Clinical Laboratory Tests Be Identified?
Though it is not immediately clear how these findings may alter current approaches to developing treatments and a vaccine for the SARS-CoV-2 coronavirus, it is another example of how increased knowledge of human DNA leads to new understandings about genetic sequences that can spur development of useful biomarkers for clinical laboratory diagnostics tests.
Swedish geneticist Svante Pääbo, PhD (above right), Director of the Max Planck Institute for Evolutionary Anthropology in Germany, is co-author of a recent study that traced a gene cluster linked to a higher risk of severe COVID-19 to 50,000-year-old Neanderthals from Croatia. “It is striking that the genetic heritage from the Neanderthals has such tragic consequences during the current pandemic,” he said. Nevertheless, such discoveries sometimes lead to new biomarkers for clinical laboratory tests and diagnostics. (Photo copyright: Max Planck Institute for Evolutionary Anthropology.)
This latest research reveals that people who inherit a specific six-gene combination on chromosome 3—called a haplotype—are three times more likely to need artificial ventilation if they are infected by the SARS-CoV-2 coronavirus. Yet, the researchers can only speculate as to why the gene cluster confers a higher risk.
“The genes in this region may well have protected the Neanderthals against some other infectious diseases that are not around today. And now, when we are faced with the [SARS-CoV-2] coronavirus, these Neanderthal genes have these tragic consequences,” Pääbo told the Guardian.
According to the study, the gene risk variant is most common in South Asia where about half of the population carries the Neanderthal risk variant. In comparison, one in six Europeans have inherited the gene sequence and the trait is almost nonexistent in Africa and East Asia.
“About 63% of people in Bangladesh have at least one copy of the disease-associated haplotype, and 13% have two copies (one from their mother and one from their father). For them, the Neandertal DNA might be partially responsible for increased mortality from a coronavirus infection. People of Bangladeshi origin living in the United Kingdom, for instance, are twice as likely to die of COVID-19 as the general population,” Science News reported.
Other Research Connecting Genes to Severe COVID-19 Symptoms
The haplotype on chromosome 3 first made headlines in June when the New England Journal of Medicine (NEJM) published the “Genomewide Association Study of Severe COVID-19 with Respiratory Failure,” which analyzed COVID-19 patients in seven hospitals in Italy and Spain. The researchers found an association between the gene cluster on chromosome 3 and severe symptoms of SARS-CoV-2 after infection and hospitalization. The study also pointed to the potential involvement of chromosome 9, which contains the ABO blood-group system gene, indicating that humans with type A blood may have a 45% higher risk of developing severe COVID-19 infections.
However, Mark Maslin, PhD, Professor of Climatology at University College London, cautions against drawing strong conclusions from the initial research tying disease risk to the genetic legacy of Neanderthals, the Guardian reported. He suggested that, while the Neanderthal-derived variant may contribute to COVID-19 risk in certain populations, genes are more likely to be just one of multiple risk factors for COVID-19 that include age, gender, and pre-existing conditions.
“COVID-19 is a complex disease, the severity of which has been linked to age, gender, ethnicity, obesity, health, virus load among other things,” Maslin told the Guardian. “This paper links genes inherited from Neanderthals with a higher risk of COVID-19 hospitalization and severe complications. But as COVID-19 spreads around the world it is clear that lots of different populations are being severely affected, many of which do not have any Neanderthal genes.
“We must avoid simplifying the causes and impact of COVID-19, as ultimately a person’s response to the disease is about contact and then the body’s immunity response, which is influenced by many environmental, health and genetic factors.”
Andre Franke, PhD, Director of the Institute of Clinical Molecular Biology, Kiel University in Germany, agrees with Maslin, the Associated Press reported. In a statement “ahead of the study’s final publication,” he said these latest findings have no immediate impact on the treatment of COVID-19, and he questioned “why that haplotype—unlike most Neanderthal genes—survived until today,” AP reported.
All of this deepens the mystery of the SARS-CoV-2 coronavirus. Genomics research continues to add new insights into what is known about COVID-19 and may ultimately provide answers on why some people contract the disease and remain asymptomatic—or have mild symptoms—while others become seriously ill or die. Understanding why and how certain genes increase the risk of severe COVID-19 could give rise to targeted clinical laboratory tests and therapies to fight the disease.
