Tag: Alzheimer’s disease

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The Role of R-loops in Neuronal Aging

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In a new editorial, researcher Hana Hall discusses the role of R-loops in neuronal aging and neurodegeneration. 

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R-loops are structures that form when the nascent RNA hybridizes with the template DNA strand, displacing the non-template strand. In other words, R-loops are like temporary tangles in our DNA where a new RNA molecule forms by copying one of the DNA strands and pushes aside the other DNA strand. Nascent RNA refers to the newly synthesized RNA molecule that is produced during the process of transcription. In addition to transcription, R-loops are involved in various biological processes, such as splicing, DNA repair and chromatin remodeling. However, when R-loop homeostasis is disrupted, they can also cause transcriptional impairment, genome instability and cellular dysfunction.

“R-loops have been shown and studied in a wide range of organisms and while they have important regulatory roles, persistent R-loops can be detrimental to cell function and survival, having been closely linked to both gene expression dysregulation and increased genome instability.”

In a new editorial paper, researcher Hana Hall from the Purdue Institute for Integrative Neuroscience at Purdue University discusses the role of R-loops in neuronal aging and neurodegeneration. On September 13, 2023, her editorial was published in Aging’s Volume 15, Issue 17, and entitled, “R-loops in neuronal aging.” Hall summarizes her recent study and the current knowledge on how R-loop levels change during aging, how they affect gene expression and neuronal function, and how they are regulated by different factors.

“In our recent study, we demonstrated that R-loops accumulate in fly PR [photoreceptor] neurons by middle age and significantly increase into late-life stages [5].”

The Editorial

According to Hall, R-loop levels increase with age in different organisms and tissues, including neurons. This could be due to several reasons, such as reduced expression or activity of R-loop resolving enzymes (e.g., Top3β, RNase H1), increased transcriptional activity or stress, or impaired DNA repair mechanisms. Hall also highlighted that R-loop accumulation is associated with decreased expression of long and highly expressed genes, which are enriched for neuronal functions. This could lead to impaired neuronal activity and communication, as well as increased vulnerability to neurodegenerative diseases.

“Our study provides first evidence of R-loop accumulation in aging neurons and a contributing role in loss of neuronal function during aging.”

Hall further discussed how R-loop homeostasis is modulated by various factors, such as chromatin structure, epigenetic modifications, RNA-binding proteins, and non-coding RNAs. She also mentioned some potential therapeutic strategies to restore R-loop balance in aging neurons, such as overexpressing or delivering R-loop resolving enzymes, modulating chromatin accessibility or targeting specific R-loop forming genes.

Conclusions

Hall concluded that R-loops are important players in neuronal aging and neurodegeneration, and that more studies are needed to understand their molecular mechanisms and functional consequences. She also suggested that R-loop mapping could be used as a biomarker to monitor neuronal health and disease progression. This editorial provides a comprehensive overview of the current knowledge of R-loops in neuronal aging, and highlights the challenges and opportunities for future research. 

“Undoubtedly, R-loops are at the crossroads of several hallmarks of aging, namely transcriptional stress, genome instability, and chronic immune response. Targeting R-loop levels thus may help restore these pathways to a normal/healthy state and slow down or prevent the onset of age-dependent neurodegenerative diseases.”

Click here to read the full editorial published in Aging.

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Aging is an open-access, traditional, peer-reviewed journal that has published high-impact papers in all fields of aging research since 2009. All papers are available to readers (at no cost and free of subscription barriers) in bi-monthly issues at Aging-US.com.

Click here to subscribe to Aging publication updates.

For media inquiries, please contact media@impactjournals.com.

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Exploring the Impact of Cognitive Reserve on Cognitive Resilience

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In a new editorial, researchers discuss their recent study investigating the effect that cognitive reserve has on brain integrity and cognitive resilience.

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Why do some individuals maintain cognitive abilities throughout their lifespan and others do not? The better question may be: How can certain individuals preserve their cognitive abilities and delay the onset of dementia despite the presence of significant neuropathologies that would otherwise suggest cognitive decline? This question remains unanswered.

“What contributes to this ‘resilience’ [3], that is why some successfully cope with progressive neuropathology while others cannot tolerate the same level of neurodegeneration, is not fully understood.”

This unanswered question has driven researchers to consider the idea of “cognitive reserve.” The rather new concept of cognitive reserve suggests that certain factors, such as engaging in education, mental stimulation and challenging activities, can create a buffer against cognitive decline and delay the onset of cognitive impairment or dementia. Researchers continue to study cognitive reserve to better understand its mechanisms and potential implications for maintaining brain health and designing effective interventions.

In a new editorial paper, researchers Monica E. Nelson, Ross Andel and Jakub Hort from the University of South Florida’s​​ School of Aging Studies discussed the outcomes, lessons and future implications of their previous 2022 study. The team examined the influence of cognitive reserve proxies on the relationship between brain integrity and cognition. On July 14, 2023, their editorial was published in Aging’s Volume 15, Issue 13, entitled, “Cognitive reserve, neuropathology, and progression towards Alzheimer’s disease.”

Cognitive Reserve’s Effect on Brain Integrity and Cognitive Performance

In their 2022 study, a total 570 older adult participants were assessed from the Czech Brain Aging Study (a longitudinal cohort study from two memory clinics in the Czech Republic). Most of the participants (n = 457) were without dementia (including those with subjective cognitive decline and amnestic mild cognitive impairment) and the remaining participants were with dementia syndrome (n = 113). The researchers examined the influence of education and occupational position (cognitive reserve proxies) on the relationship between the participants’ hippocampal or total gray matter volume and cognitive performance. Measurements included brain volume, executive control, language, memory, attention/working memory, and visuospatial skills.

“[…] we assessed the inter-link between cognitive reserve, neuropathology, and cognitive functioning among participants with subjective cognitive decline, mild cognitive impairment, and dementia.”

The team found that the association between brain volume and cognitive performance varies based on cognitive reserve. Findings showed that a higher education and occupational position magnified the associations between brain volume and cognitive performance in participants without dementia. In participants with dementia, higher education decreased the associations between brain volume and visuospatial skills. Overall, the results showed that cognitive reserve affects the relationship between brain volume and cognitive performance, with greater cognitive reserve related to a stronger link before dementia diagnosis and a weaker link after.

Future Directions 

In their subsequent editorial, the researchers were forthcoming about limitations of this study and addressed key opportunities for future studies. Limitations were identified as the use of a relatively homogeneous sample population, the absence of the use of biomarkers in diagnosis and the cross sectional design. Cross-sectional studies may not fully capture disease-related changes in neuropathology and could present a distorted view of the linkages between cognitive reserve, neuropathology and cognitive outcomes. The authors advocate for conducting longitudinal studies to track how cognitive reserve operates in individuals as they progress from normal to dementia. 

Additionally, the team wrote that future studies would be improved by investigating a range of Alzheimer’s disease biomarkers, such as beta-amyloid and tau, individually and together, to understand how they influence the associations between cognitive reserve, brain health and cognition. Different biomarkers may lead to varied results in how cognitive reserve moderates these associations. And finally, future studies should also assess older adults across the cognitive spectrum to determine when cognitive reserve is protective against brain health decline and neuropathology, and when its effectiveness diminishes. Some researchers have suggested a U-shaped relationship to explain mixed findings in different studies.

“Even though our study represents one of the first to come from Eastern Europe [4], future work should be conducted in additional populations, representing geographic, racial, and socioeconomic diversity.”

Implications

The potential impact of this research may be important, as it could lead to the development of effective interventions and strategies to preserve cognitive abilities and delay the onset of dementia. By gaining a deeper understanding of cognitive reserve and its mechanisms, we can take steps to promote brain health throughout life, potentially reducing the burden of dementia on individuals, communities and society overall.

As research continues in this field, it is clear that cognitive reserve holds great promise for unlocking the secrets of cognitive resilience and paving the way for healthier aging and improved quality of life for older adults. By addressing the limitations of current studies and exploring new avenues of investigation, we move closer to finding answers to the vital question of how some individuals maintain their cognitive abilities despite the presence of significant neuropathologies, while others do not.

“By assessing cognitive reserve in distinct populations, a more complete understanding of how cognitive reserve relates to neuropathology and cognition and whether these associations may be affected by distinct macro-level contextual differences among populations can be established. Disentangling these complex relationships may provide a critical step in reducing the impact of dementia on society.”

Click here to read the full editorial published by Aging.

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Aging is an open-access, peer-reviewed journal that has been publishing high-impact papers in all fields of aging research since 2009. These papers are available to readers (at no cost and free of subscription barriers) in bi-monthly issues at Aging-US.com.

Click here to subscribe to Aging publication updates.

For media inquiries, please contact media@impactjournals.com.

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Can a Leaky Gut Lead to Alzheimer’s Disease?

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In a new editorial, researchers explore how a leaky gut can lead to Alzheimer’s disease using the Seed and Soil Model of Neurocognitive Disorders to explain.

New research continues to illuminate the far-reaching implications of the gut microbiome and its crucial role in our overall health. The term “gut dysbiosis” refers to an imbalance of healthy and unhealthy microbes in the gastrointestinal tract. Repercussions of gut dysbiosis are not only limited to innocuous discomfort—it can lead to immune dysregulation and trigger a cascade of various disease states. 

In a new editorial paper, researchers Chun-Che Hung, Kristi M. Crowe-White and Ian M. McDonough from Chang Gung University and The University of Alabama discuss the relationship between gut dysbiosis and neurocognitive disorders such as Alzheimer’s disease (AD). Their editorial was published in Aging’s Volume 15, Issue 12, on June 19, 2023, entitled, “A seed and soil model of gut dysbiosis in Alzheimer’s disease.”

“[…] recent research has demonstrated a crucial role of gut microbiota in the etiopathogenesis of AD [Alzheimer’s disease] that offers a new window into possible origins and consequences of AD through interactions between gut microbiota and the central nervous system, known as the ‘microbiota-gutbrain axis’ [1].”

The Seed and Soil Model of Neurocognitive Disorders

The “Seed and Soil Model” in biology was first used in an attempt to describe why some individuals who are predisposed to developing neurocognitive disorders do not ever develop them. As the researchers wrote in their editorial, the “seeds” in this analogy represent genetic predispositions or a family history of a particular disease state. The “soil” represents the external environment that either enables or disables the expression of these seeds. This external environment can be influenced by behavioral and/or lifestyle factors. Although this model did not originally include the microbiota-gut-brain axis, the authors of this editorial are now applying it.

Interestingly, the researchers here have related the “leaky gut” phenomenon of gut dysbiosis to Alzheimer’s disease (AD). A leaky gut, plainly described as increased intestinal permeability, is a condition where the lining of the intestine becomes more porous. This allows larger molecules and toxins to pass through into the bloodstream—opening the door to potential inflammation and various health problems. 

Metabolites involved with gut leakiness have previously been linked to increased permeability of the blood-brain barrier (BBB). The opening of the BBB allows bacterial endotoxins to travel from the gut to the brain environment. This can increase inflammation within the system. The authors propose that gut leakiness, through the Seed and Soil Model, may explain why some people predisposed to AD realize the disease, while those without gut dysbiosis may not.

“According to the Seed and Soil Model of Neurocognitive Disorders, this translocation would create a toxic microenvironment in the brain vulnerable to pathogenesis, especially for those with a genetic predisposition to AD.”

Conclusion

“According to the Seed and Soil Model of Neurocognitive Disorders, environmental and behavioral patterns can influence the balance of neuroprotection vs. toxicity of the brain’s micro-environment.”

In sum, emerging research continues to shed light on the significance of the gut microbiome and its connection to our overall health. The editorial by Hung, Crowe-White and McDonough explores the relationship between gut dysbiosis and neurocognitive disorders, particularly Alzheimer’s disease, through the lens of the Seed and Soil Model of Neurocognitive Disorders. By considering the impact of leaky gut and the translocation of bacterial endotoxins on the brain, the authors propose that gut dysbiosis may contribute to the pathogenesis of AD, particularly in individuals with a genetic predisposition. This perspective opens new avenues for understanding the complex interactions within the microbiota-gut-brain axis and provides insights into ways to potentially stave off cognitive decline with diet and lifestyle interventions.

“Here, we extend the model to better understand how the microbiota-gut-brain axis may play a causal role in the development of AD. However, more research is needed to test additional hypotheses of the model.”

Click here to read the full research paper published by Aging.

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Aging is an open-access, peer-reviewed journal that has been publishing high-impact papers in all fields of aging research since 2009. These papers are available to readers (at no cost and free of subscription barriers) in bi-monthly issues at Aging-US.com.

Click here to subscribe to Aging publication updates.

For media inquiries, please contact media@impactjournals.com.

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Brain Aging Insights from Individuals Without Neurodegeneration

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The Trending With Impact series highlights Aging publications (listed by MEDLINE/PubMed as “Aging (Albany NY)” and “Aging-US” by Web of Science) that attract higher visibility among readers around the world online, in the news and on social media—beyond normal readership levels. Look for future science news about the latest trending publications here, and at Aging-US.com.

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A healthy brain continuously produces new proteins to support synaptic plasticity, maintain neuronal health, facilitate signaling pathways, produce neurotransmitters, enable neuroplasticity and adaptation, and meet its metabolic demands. These processes are essential for normal brain function, learning, memory, and overall cognitive abilities. Researchers believe that the dysregulation of proteins is at the core of brain aging. However, the exact recipe for protein dysregulation that leads to accelerated brain aging and neurodegenerative disorders has yet to be brought to light. 

Previous brain proteostasis (referring to the maintenance of protein homeostasis in brain cells) studies in individuals with Alzheimer’s disease (AD) pathology and age-related neuropathological changes have shown protein dysregulation leading to a buildup of amyloid plaques and neurofibrillary tangles. While these studies have greatly enhanced our knowledge of brain aging, gaps in our understanding remain. What proteomic characteristics do healthy brain aging individuals—without neurodegenerative disorders—have in common?

“To our knowledge, whole phosphoproteomes centered on the human brain aging without AD pathology are unavailable.”

In a new study, researchers Pol Andrés-Benito, Ignacio Íñigo-Marco, Marta Brullas, Margarita Carmona, José Antonio del Rio, Joaquín Fernández-Irigoyen, Enrique Santamaría, Mónica Povedano, and Isidro Ferrer from Bellvitge Institute for Biomedical Research, Universidad Pública de Navarra, Barcelona Institute for Science and Technology, and University of Barcelona aimed to shed light on the mechanisms underlying brain aging in the absence of AD pathology and age-related neuropathological changes. Their research paper was published on May 13, 2023, in Aging’s Volume 15, Issue 9, and entitled, “Proteostatic modulation in brain aging without associated Alzheimer’s disease-and age-related neuropathological changes.”

The Study

The production of new proteins is crucial for maintaining protein homeostasis in the brain. A post-translational modification used to maintain this homeostasis is protein phosphorylation. In this study, the researchers conducted proteomic and phosphoproteomic analyses of frontal cortex samples from the donor brains of deceased individuals between the ages of 30 and 85. These individuals had passed away due to non-neurological complications and were reported to have had full cognitive function. Individuals were divided into four groups: young group one (30–44), middle-aged group two (45-52), early-elderly group three (64–70), and late-elderly group four (75–85).

“​​We chose the FC [frontal cortex] because of its role in cognition and emotion and the abundant molecular information that permits comparison with other studies.”

Conventional label-free- and SWATH- (sequential window acquisition of all theoretical fragment ion spectra) mass spectrometry were used to assess the (phospho)proteomes of the frontal cortices from individuals in all four age groups. Immunohistochemistry and/or western blotting was/were also used to validate a subgroup of proteins. The researchers categorized deregulated proteins and phosphoproteins into eight clusters based on their age-dependent expression similarity (see paper for clusters). Interestingly, protein and phosphoprotein levels of the larger hierarchical clusters were stable until the age of 70 years. After 70, the late-elderly group showed significant decreased or increased expression of protein clusters one and seven, and major phosphorylation modifications occurred in clusters four and eight.

Results

The team then used multi-comparative analyses to categorize altered proteins and phosphoproteins as neuronal, astroglial, oligodendroglial, microglial, and endothelial. They observed a similar pattern among proteomic and phosphoproteomic alterations: major changes were related to neuronal cell populations across all four groups—and these changes were more pronounced with age. Cytoskeletal and membrane proteins accounted for the largest number of differentially-expressed proteins and phosphoproteins.

“Furthermore, main alterations in the proteome are associated with proteins specific to neuronal populations, rather than those found in other cell types in the brain.”

Their findings also revealed a decline in the expression of P20S α + β with aging, while the expression of P19S and immunoproteasome subunits LMP2 and LMP7 remained preserved. Notably, the expression levels of an autophagy component, ATG5, remained unchanged with age. Some mitochondrial membrane proteins showed altered levels at advanced ages, but key markers of mitochondrial function were preserved. These findings suggest a potential preservation of these pathways in advanced aging, contrasting with observations in neurodegenerative disorders. Additionally, reduced levels of GSK3α/β were observed, and the researchers point out that this decrease in GSK3α/β with age may be understood as protective against different age-related brain diseases.

Summary & Conclusion

“Therefore, our results fill the gap between brain ageing without ADNC [AD neuropathological changes], and cases with early and advanced stages of AD pathology.”

The researchers are forthcoming about limitations of this study. Given it is rare for old-aged individuals not to have neurological deficits, AD or other neuropathological changes, their main limitation was that each of the four groups included merely four individuals. Despite limitations, these findings contribute to our understanding of brain aging in the absence of AD pathology and age-related neuropathological changes. 

The study revealed that major changes in protein expression were primarily associated with neuronal cell populations and became more pronounced with age. The preservation of specific protein pathways, proteasome components, autophagy-related components, and mitochondrial markers in advanced aging individuals without neurodegenerative disorders suggests the presence of resilience mechanisms that protect against protein dysregulation and neurodegeneration. Overall, this research provides valuable insights into the proteomic characteristics of healthy brain aging and highlights potential targets for therapeutic interventions aimed at promoting healthy brain aging and preventing age-related neurodegenerative diseases. Further studies are necessary to elucidate the specific mechanisms underlying these proteomic alterations and their functional implications in brain aging.

“The present observations identify proteostatic changes, including different changes in the phosphoproteome in the human FC in brain aging in the rare subpopulation of old-aged individuals without neurological deficits, and not having ADNC and other neuropathological change in any region of the telencephalon.”

Click here to read the full research paper published by Aging.

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Aging is an open-access, peer-reviewed journal that has been publishing high-impact papers in all fields of aging research since 2009. These papers are available to readers (at no cost and free of subscription barriers) in bi-monthly issues at Aging-US.com.

Click here to subscribe to Aging publication updates.

For media inquiries, please contact media@impactjournals.com.

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The Brain Age Gap

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The Trending With Impact series highlights Aging publications (listed by MEDLINE/PubMed as “Aging (Albany NY)” and “Aging-US” by Web of Science) that attract higher visibility among readers around the world online, in the news and on social media—beyond normal readership levels. Look for future science news about the latest trending publications here, and at Aging-US.com.

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Aging is a risk factor for many diseases, including Alzheimer’s disease (AD). While scientists have made some progress in understanding the physiology of aging and its relationship to AD and related disorders, our understanding remains incomplete (to say the least). It is possible that civilization is currently in the midst of an artificial intelligence (AI) and machine learning (ML) “boom.” Researchers are now using AI and ML technologies to elevate our comprehension of aging and aging-related diseases.

“Artificial intelligence (AI) and machine learning (ML) technologies can help us better understand these diseases and aging itself by using biological data from the brain or other sources to create a mapping between age and biological data.”

In a new editorial paper, researchers Jeyeon Lee, Leland R. Barnard and David T. Jones from the Mayo Clinic in Rochester, Minnesota, discuss a recent study they conducted and explore the potential of AI to revolutionize the field of geriatrics. Their editorial was published in Aging’s Volume 15, Issue 8, on April 3, 2023, entitled, “Artificial intelligence and the aging mind.”

Their Study

In a recent 2022 study, Lee, Barnard, Jones, and the rest of their team developed convolutional neural network-based brain age prediction models using a large collection of data from brain magnetic resonance imaging (MRI) and brain fluorodeoxyglucose positron-emission tomography (FDG-PET) in people aged from 26 to 98 years old. In a sample of cognitively normal individuals, the AI models showed accurate brain age estimation of which a mean absolute error (MAE; unit, years) was 3.08±0.14 for the FDG-based model and 3.49±0.16 for the MRI-based model. 

The team found that higher brain age gaps (the difference between biological age and chronological age) were estimated in cohorts with neurodegenerative disorders—including mild cognitive impairment (MCI), AD, frontotemporal dementia (FTD), and dementia with Lewy bodies (DLB)—than normal controls. The brain age gap was strongly associated with pathologic tau protein levels and cognitive test scores. This gap also showed longitudinal predictive ability for cognitive decline in AD-related disorders.

“Interestingly, the brain imaging patterns generating brain age gaps in AD showed higher similarity with normal aging than other neurodegenerative syndromes implying that AD might be more like an accelerated representation of biological aging than others.”

Summary & Conclusions

The study conducted by Lee, Barnard, Jones, and their team using neural network-based brain age prediction models has shown promising results in accurately estimating brain age and identifying differences between normal aging and neurodegenerative disorders. However, the authors of this editorial note that variations in data make creating a uniform language used to compare and contrast large sums of data very difficult.

“Although more research and optimization are needed to determine its clinical usefulness, the study of brain age has great potential as a tool for understanding brain aging and age-related diseases.”

In conclusion, aging is a complex process that increases the risk of Alzheimer’s disease and various diseases. Recent advancements in artificial intelligence and machine learning technologies offer new opportunities to better understand the underlying mechanisms of aging and aging-related disorders. This research opens up exciting possibilities for the future of geriatric care and improving the lives of aging populations. As technology continues to advance, it is likely that we will gain further insights into aging through the brain age gap, ultimately leading to better prevention, diagnosis and treatment options.

“The fact that the brain age gap is a comprehensive and intuitive measure of disease severity using biological data that is already being acquired in clinical practice, makes it an attractive biomarker for further development for clinical use [8].”

Click here to read the full editorial paper published by Aging.

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Aging is an open-access, peer-reviewed journal that has been publishing high-impact papers in all fields of aging research since 2009. These papers are available to readers (at no cost and free of subscription barriers) in bi-monthly issues at Aging-US.com.

Click here to subscribe to Aging publication updates.

For media inquiries, please contact media@impactjournals.com.

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Fruit Flies Shed New Light on Memory and Aging

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In a recent study, researchers from Western University and Indiana University investigated the connection between aging, memory and lactate metabolism in flies.

Fruit Flies Shed New Light on Memory and Aging
Male common fruit fly (Drosophila Melanogaster) doing what fruit flies do best – enjoing its fruit (apple)

The Trending With Impact series highlights Aging publications (listed by MEDLINE/PubMed as “Aging (Albany NY)” and “Aging-US” by Web of Science) that attract higher visibility among readers around the world online, in the news and on social media—beyond normal readership levels. Look for future science news about the latest trending publications here, and at Aging-US.com.

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The brain is a complex organ responsible for many critical functions, including the formation and retrieval of our memories. As we age, the brain undergoes changes that can affect cognitive abilities, including our memory. Understanding the mechanisms that underlie these changes is critical for developing therapies for age-related cognitive decline. 

“Over the last two decades there has been growing recognition that lactate, the end product of glycolysis, serves many functions, including acting as a source of energy, a signaling molecule, and even as an epigenetic regulator.”

Lactate & LDH

Lactate is a molecule that is produced during the metabolism of glucose in the body. It is a byproduct of anaerobic metabolism, which occurs when there is insufficient oxygen supply to meet the energy demands of the body. Lactate can be used as an energy source by some cells, such as the heart and skeletal muscles, and it can also be transported to the liver where it can be converted back into glucose.

Lactate dehydrogenase (LDH), on the other hand, is an enzyme that catalyzes the conversion of pyruvate to lactate (the reverse reaction of lactate production) and is also involved in other metabolic processes. This enzyme is found in many tissues of the body, including the heart, liver and skeletal muscles, and is released into the bloodstream when tissues are damaged. LDH is often used as a diagnostic marker for various medical conditions, such as heart attacks, liver disease and certain cancers. High levels of LDH in the blood may indicate tissue damage or cell death, while low levels may indicate a deficiency in the enzyme.

The Study

Recently, researchers investigated the role of LDH in memory formation and aging using Drosophila melanogaster (fruit flies) as a model organism. In a new study, researchers Ariel K. Frame, J. Wesley Robinson, Nader H. Mahmoudzadeh, Jason M. Tennessen, Anne F. Simon, and Robert C. Cumming from Western University and Indiana University used genetic manipulation techniques to alter LDH expression in the neurons or glia of fruit flies to investigate its effects on aging and memory. Their research paper was published in Aging’s Volume 15, Issue 4, and entitled, “Aging and memory are altered by genetically manipulating lactate dehydrogenase in the neurons or glia of flies.”

“The astrocyte-neuron lactate shuttle hypothesis posits that glial-generated lactate is transported to neurons to fuel metabolic processes required for long-term memory.”

Lactate shuttling is a process in which lactate is transported from one cell or tissue to another for use as an energy source or as a signaling molecule. Previous research has shown that LDH is expressed in both neurons and glia in the brain, and that it may play a role in regulating synaptic plasticity and memory formation. The authors of the current research paper aimed to test the hypothesis that alterations in LDH expression in the brain may contribute to age-related cognitive decline.

“D. melanogaster serves as a good model for understanding the role of glia-neuron lactate shuttling in central nervous system (CNS) function and cognitive behaviour.”

To test this hypothesis, the researchers genetically manipulated LDH expression in the neurons or glia of fruit flies (dLDH) and assessed the impact on memory formation and aging. Specifically, they used RNA interference (RNAi) to either knock down or overexpress dLDH in either neurons or glia. They then assessed the effects of these manipulations on two different memory tasks at different ages, courtship memory and aversive olfactory memory, and also assessed survival, negative geotaxis, brain neutral lipids (the core component of lipid droplets), and brain metabolites.

Results

Their results showed that dLDH manipulation had differential effects on fruit flies depending on the cell type in which it was altered. In neurons, both upregulation and downregulation of dLDH resulted in memory impairment and decreased survival with age. In contrast, downregulation of dLDH in glial cells caused age-related memory impairment, without altering survival. Upregulating dLDH expression in glial cells lowered survival without disrupting memory. Both neuronal and glial dLDH upregulation increased neutral lipid accumulation.

“We provide evidence that altered lactate metabolism with age affects the tricarboxylic acid (TCA) cycle, 2-hydroxyglutarate (2HG), and neutral lipid accumulation.”

The results of this study may provide new insights into the role of LDH in memory formation and aging in humans. The findings suggest that LDH may be a potential target for developing therapies to combat age-related cognitive decline. Additionally, the study highlights the importance of considering cell-type specificity when investigating the role of genes and enzymes in complex biological processes. A limitation of the study is that it was conducted in fruit flies, which may not fully capture the complexity of memory formation and aging in humans. However, fruit flies have been shown to be a valuable model organism for studying many aspects of brain function, and the findings of this study may provide a foundation for future research in mammals.

“Collectively, our findings indicate that the direct alteration of lactate metabolism in either glia or neurons affects memory and survival but only in an age-dependent manner.”

Conclusion

In conclusion, the study provides new insights into the role of LDH in memory formation and aging. The findings suggest that LDH may play a critical role in regulating energy metabolism in the brain, which in turn affects synaptic plasticity and memory formation. The study also highlights the importance of considering cell-type specificity when investigating the role of genes and enzymes in complex biological processes. Future research in mammals may be needed to further explore the implications of these findings for human health and the potential for developing therapies for age-related cognitive decline. Nonetheless, this study provides an important step forward in understanding the complex interplay between lactate metabolism, memory and aging.

“In this study we demonstrate the importance of maintaining appropriate levels of dLdh in D. melanogaster glia and neurons for maintenance of long-term courtship memory and survival with age (Figure 6). In addition, our results implicate lipid metabolism, 2HG accumulation, and changes in TCA cycle activity as factors underlying the age-related impacts of perturbed dLdh expression, which likely modifies glia-neuron lactate shuttling in the fly brain.”

Click here to read the full research paper published by Aging.

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Aging is an open-access, peer-reviewed journal that has been publishing high-impact papers in all fields of aging research since 2009. These papers are available to readers (at no cost and free of subscription barriers) in bi-monthly issues at Aging-US.com.

For media inquiries, please contact media@impactjournals.com.

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Is Estrogen Dysregulation Behind Alzheimer’s Pathology?

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In a new study, researchers explored Alzheimer’s disease and its potential relationship with the estrogen receptor-α gene (ESR1).

In a new study, researchers explored Alzheimer's disease and its potential relationship with the estrogen receptor-α gene (ESR1).

The Trending With Impact series highlights Aging publications (listed as “Aging (Albany NY)” by Medline/PubMed and “Aging-US” by Web of Science) that attract higher visibility among readers around the world online, in the news, and on social media—beyond normal readership levels. Look for future science news about the latest trending publications here, and at Aging-US.com.

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The United States government currently has a mind-blowing annual budget of $3.5 billion designated for Alzheimer’s disease (AD) and dementia research funding. Therapeutics pushed forward thus far have been largely based on the amyloid-beta (Aβ) cascade hypothesis of AD. Surprisingly, despite decades and billions, these interventions have yielded little to no benefits for AD patients. This lack of efficacy has encouraged some researchers to rethink AD pathology and focus on discovering key triggers and mechanisms of neuroinflammation.

“There has been a lengthy and ongoing scientific debate around the causative factors of AD, and the relative importance of both senile Aβ plaques and tau tangles has been largely informed by postmortem investigations of the AD brain. For several decades, the amyloid hypothesis has dominated the field, which has brought forth many high-profile therapeutic attempts that have produced side effects but no real benefits [5].”

Women & Alzheimer’s Disease

Women compose two-thirds of the United States Alzheimer’s population. Is this gender-specific risk a result of living longer or is it due to other causes, perhaps related to hormonal differences or gender-associated differential gene expression? Previous studies have found that estrogen may protect neurons from the damaging effects of amyloid-beta plaques and tau tangles. However, in women, estrogen levels tend to decline with age, which could be one reason why aging women are more susceptible to AD. 

In a new study, researchers Junying Liu, Shouli Yuan, Xinhui Niu, Robbie Kelleher, and Helen Sheridan from Trinity College Dublin, Peking University and Jilin University examined the potential relationship between the estrogen receptor-α gene (ESR1) and neuroinflammation. Their research paper was published on November 1, 2022, in Aging’s Volume 14, Issue 21, and entitled, “ESR1 dysfunction triggers neuroinflammation as a critical upstream causative factor of the Alzheimer’s disease process.”

“AD is characterized by three major questions: Why is age the primary risk factor? Why are women more sensitive to the onset of this form of dementia? And why are neurons in areas of the brain that are essential for memory selectively targeted?”

The Study

Originally, the researchers in this study had been in the process of investigating ESR1-knockdown in breast cancer when they stumbled upon another discovery. (ESR1 is a gene that codes for the estrogen receptor, a protein that helps to regulate cell division and differentiation.) To their surprise, KEGG pathway enrichment analysis showed that ESR1 may also be related to axonal guidance, inflammation-related gene markers and Notch signaling pathways. Upon further validation using a dataset of in vivo AD inflammatory samples, the team found that the ESR1 gene was altered in AD patients and was associated with an increase in pro-inflammatory markers.

“ESR dysfunction likely plays a role in AD pathology – especially in women – although the specific mechanisms remain unclear. In vivo and ex vivo studies demonstrate that neuroinflammatory brain states overlap with ESR signaling pathways and that these two systems interact closely.”

In the current study, the researchers used an animal model to explore the potential role of ESR1 in modulating inflammation-related AD pathology. Using a macrophage cell line, they identified ESR1 as a key modulator of inflammation in the context of AD. They then showed that when the ESR1 gene was absent or mutated, neuroinflammation occurred. This finding offers a potential mechanism for understanding the gender-specific risk of AD in women.

“Our results suggest that ESR1 is modulated by apolipoprotein E (APOE) through CEBPB/ATF4, mir-155-5p, or mir-1-3p. Moreover, sea hare-hydrolysates (SHH), as one of the axonal guidance molecules, could regulate the STAT3/PRDM1/CEBPB pathway and consequently induce cell death through pyroptosis signaling pathways, trigger the secretion of IL1β, leading to neuroinflammation and worsening AD pathogenesis. Molecular docking verification demonstrated that the predicted natural products scoulerine and genistein displayed strong binding affinities for BACE1 and ESR1, respectively. This strategy can be used to design novel, personalized therapeutic approaches to treatment and a first-in-class clinical lead for the personalized treatment of AD.”

Conclusion

The research team concluded that further studies are needed to elucidate the exact mechanisms through which ESR1 modulates inflammation and its role in Alzheimer’s disease. These findings may offer a novel therapeutic direction for treating AD. Therapeutics targeting ESR1 could potentially be used to reduce inflammation in the brain and prevent AD progression. This may be beneficial for both men and women afflicted with this devastating disease.

“Unfortunately, despite enormous efforts, there remains no cure for this terrible illness, and current treatments merely alleviate its devastating symptoms for a short time. This study performed several bioinformatics-based analyses, concluding that ESR1 dysfunction might mediate axonal guidance, induce neuroinflammation or pyroptosis in the brain, and subsequently worsen AD conditions.”

Click here to read the full research paper published by Aging.

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Aging is an open-access journal that publishes research papers bi-monthly in all fields of aging research. These papers are available at no cost to readers on Aging-us.com. Open-access journals have the power to benefit humanity from the inside out by rapidly disseminating information that may be freely shared with researchers, colleagues, family, and friends around the world.

For media inquiries, please contact media@impactjournals.com.

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Can microRNAs in the Bloodstream Signal Cognitive Decline?

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In a cohort of pre-diagnosed, cognitively “normal” men, a recent Aging study compares expression levels of circulating miRNAs and their association with cognitive function and decline.

miRNAs, microRNAs, RNA illustration
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Can factors in our bloodstream tell us about our cognitive abilities or predict cognitive decline later in life? Among individuals with dementias, including Alzheimer’s disease (AD), studies have identified extracellular microRNAs (miRNAs) as potential biomarkers of cognitive impairment. In cognitively normal individuals, however, this association has not yet been fully investigated. 

“Understanding the functions of miRNAs in the earliest stages of cognitive decline will expand our knowledge on the biology of prodromal AD and the roles of circulating miRNAs in neurodegenerative diseases and could result in identification of therapeutic targets to guide drug development [17].”

In a new research paper, published on the cover of Volume 14, Issue 17, of Aging (listed as “Aging (Albany NY)” by Medline/PubMed and “Aging-US” by Web of Science), researchers Nicole Comfort, Haotian Wu, Peter De Hoff, Aishwarya Vuppala, Pantel S. Vokonas, Avron Spiro, Marc Weisskopf, Brent A. Coull, Louise C. Laurent, Andrea A. Baccarelli, and Joel Schwartz from Columbia University Mailman School of Public Health, University of California San Diego, VA Boston Healthcare System, Boston University School of Medicine, and Harvard TH Chan School of Public Health assessed the expression levels of extracellular miRNAs circulating in blood plasma taken from 530 cognitively normal men and investigated the association between these miRNAs and cognitive function. Their secondary goal was to investigate the genes and biological pathways associated with miRNAs linked to cognitive function or decline. The research paper was published on September 6, 2022, and entitled, “Extracellular microRNA and cognitive function in a prospective cohort of older men: The Veterans Affairs Normative Aging Study.”

The NAS Cohort

The Normative Aging Study (NAS) is a large longitudinal study that was established by the United States Department of Veterans Affairs in 1963. Since this study began, researchers have been diligently following-up with a cohort of 2,280 men from Massachusetts, United States. (Most of these men served in World War II and the Korean War.) Participants in NAS have comprehensive baseline examinations every three to five years to record their aging patterns, including global cognitive function assessments using the Mini-Mental State Examination (MMSE). The average age of this veteran cohort is currently 72 years old.

The Study

In the present study, blood samples were collected from 530 NAS participants between the years 1996 and 2013—totaling 1,331 in-person visits; equal to 2,471 years of follow-up. Plasma miRNAs were profiled using small RNA sequencing (RNA-seq). Linear regression and linear mixed models were used to assess the expression of 381 miRNAs and their association with current cognitive function and rate of change in cognitive function.

Of the 381 plasma miRNAs detected in at least 70% of the samples collected, two miRNAs were associated with higher baseline MMSE scores. Thirty-three miRNAs were associated with the rate of change in MMSE over time. KEGG enrichment analysis and repeated measures analyses were used to explore potential regulatory targets of the significant plasma miRNAs. The genes targeted by the significant miRNAs were primarily associated with prion diseases, fatty acid biosynthesis, Hippo signaling, ECM-receptor interactions, and TGF-β signaling pathways. 

“Taken together, our results suggest that various plasma extracellular miRNAs are associated with global cognitive function among cognitively ‘normal’ men. If they were to play a causal role in cognitive decline, it would likely be through pathways that regulate synaptic plasticity, cell death, the response to injury, and energy homeostasis. Extracellular miRNAs may also contribute to greater rates of cognitive decline possibly through involvement in the prion-like propagation of AD lesions or in hindering their neuroprotective role of curbing AD-like pathology.”

Conclusion

These findings suggest that plasma miRNA levels are associated both with global cognition and the rate of change in global cognition among cognitively normal older men. The researchers were forthcoming about the limitations of this study, especially in regard to the study population and the MMSE scoring.  Still, this study highlights the potential of miRNAs as biomarkers for cognitive function and decline in older men and underscores the importance of elucidating the mechanisms by which extracellular miRNAs influence cognition.

“Additional research is needed to identify the biological pathways influenced by expression of these extracellular miRNAs, investigate relationships with CNS miRNA expression, and examine the potential impacts of circulating miRNAs on other neurological outcomes.”

Click here to read the full research paper published by Aging.

AGING (AGING-US) VIDEOS: YouTube | LabTube | Aging-US.com

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Aging is an open-access journal that publishes research papers bi-monthly in all fields of aging research. These papers are available at no cost to readers on Aging-us.com. Open-access journals have the power to benefit humanity from the inside out by rapidly disseminating information that may be freely shared with researchers, colleagues, family, and friends around the world.

For media inquiries, please contact media@impactjournals.com.

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Trending With Impact: How Biological Sex Impacts Alzheimer’s Disease

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Men and women are disproportionately impacted by Alzheimer’s disease (AD). Researchers investigated AD mice for potential sex differences in synaptic function.

Figure 1. The diagram shows sex-specific alterations in plasticity and memory and the associated changes in amyloid beta (Aβ) pathology and inflammatory response in APP/PS1 mice.
Figure 1. The diagram shows sex-specific alterations in plasticity and memory and the associated changes in amyloid beta (Aβ) pathology and inflammatory response in APP/PS1 mice.

The Trending With Impact series highlights Aging (Aging-US) publications that attract higher visibility among readers around the world online, in the news, and on social media—beyond normal readership levels. Look for future science news about the latest trending publications here, and at Aging-US.com.

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As the worldwide elderly population continues to expand, the symptoms of dementia, including Alzheimer’s disease (AD), are simultaneously increasing around the globe. Researchers are driven to investigate new ways to detect and treat AD in earlier stages—before symptoms become more difficult or impossible to overturn. An important piece of data to consider is that dementia is more prevalent among women than among men; dementia affects 8.1 % of women and 5.4% of men. Many AD studies have not used gender/sex as a variable to cross-examine their research findings. This information may be a key factor that leads to developing more efficacious strategies for AD detection and treatment in all patients, and especially in women.

“In the long run, the underrepresentation of female biology in biomedical research will hamper the development of effective drugs with negative consequences on women’s health.”

In a recent editorial paper published on March 12, 2022, by Aging (Aging-US) in Volume 14, Issue 5, researchers from the National University of Singapore discussed the importance of understanding sex differences in Alzheimer’s disease. Their trending editorial paper, entitled, “Sex matters in Alzheimer’s disease?“, was based on results from their previous study published in 2021.

Sex-Specific Synaptic Dysfunction

In AD patients, researchers have observed a loss of function in the sites where nerve cells communicate with each other—in the synapses. Synaptic dysfunction is an early event in AD and can be observed years before other symptoms appear. In the research study being discussed in this editorial, the research team examined differences between the synaptic activity of male and female mice with two mutations associated with early-onset Alzheimer’s disease (APP/PS1).

“To characterize molecular changes in the AD brain that is attributed to sex differences, we performed RNA sequencing and immunohistochemistry of the hippo-campus and showed accelerated pathology, stronger immune response and higher microglial activation in AD female mice compared to males [5].”

Their findings revealed a number of differentially expressed genes and plasticity-related genes were sex-regulated. Plasticity-related genes are important for learning, memory and other cognitive abilities. The study also found that female AD mice had an accelerated Alzheimer’s pathology, stronger immune response and higher microglial activation—all of which contribute to dementia symptoms. These results suggested that sex differences in early-stage synaptic function may have important implications for understanding the higher prevalence of Alzheimer’s disease in women, and the related mechanisms may be potential targets for diagnosis and treatment.

Conclusion

In their editorial paper, the authors acknowledge that, although more research needs to be done on this topic, these findings could lead to new strategies for detecting and treating Alzheimer’s disease. The authors conclude by writing that synaptic dysfunction among males and females with Alzheimer’s disease revealed sex-regulated differentially expressed genes and plasticity-related genes as potential targets for early AD intervention. Overall, sex differences should be considered when developing custom-tailored strategies for early AD detection, prevention and treatment.

​​”Our work, along with others in this field, also emphasises the importance of including biological sex as variable in many research settings, particularly studies exploring aging [7] and how they impact different disease states [8].”

Click here to read the full editorial paper published by Aging (Aging-US).

Click here to read Aging’s Special Collection on Alzheimer’s Disease. 

AGING (AGING-US) VIDEOS: YouTube | LabTube | Aging-US.com

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Aging (Aging-US) is an open-access journal that publishes research papers bi-monthly in all fields of aging research. These papers are available at no cost to readers on Aging-us.com. Open-access journals have the power to benefit humanity from the inside out by rapidly disseminating information that may be freely shared with researchers, colleagues, family, and friends around the world.

For media inquiries, please contact media@impactjournals.com.

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Trending With Impact: Cognitive Decline Predicted from Middle-Age

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Researchers investigated epigenetic and brain aging markers in middle-age for their potential to predict cognitive decline.

Trending With Impact: Cognitive Decline Predicted from Middle-Age

The Trending With Impact series highlights Aging (Aging-US) publications that attract higher visibility among readers around the world online, in the news, and on social media—beyond normal readership levels. Look for future science news about the latest trending publications here, and at Aging-US.com.

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Aging seems nearly synonymous with brewing cognitive decline, but does it have to be? There are interventions that may help preserve cognitive function with age, however, the first order of business is identifying early biological aging markers that present before symptoms begin emerging. Mid-life biomarkers that can indicate accelerated aging and predict age-related cognitive decline (including Alzheimer’s disease and dementia) may provide humans with enough time to course-correct and improve our quality of life in old age.

The latest to endeavor in search of these early aging markers are researchers from Northwestern University Feinberg School of Medicine, University of Texas Health Science Center at San Antonio, University of Pennsylvania, Boston University School of Medicine, National Institute on Aging from the National Institutes of Health, University of Minnesota, Columbia University Mailman School of Public Health, Kaiser Permanente Division of Research, University of Texas at Austin, University of California San Francisco, and the San Francisco Veterans Affairs Medical Center. Their new research study was published in Aging (Aging-US) as the cover paper in Volume 14, Issue 4, on February 27, 2022. The paper is entitled, “Mid-life epigenetic age, neuroimaging brain age, and cognitive function: coronary artery risk development in young adults (CARDIA) study.”

The Study

In this study, the researchers looked at the associations between cognitive function, epigenetic age and age acceleration measures (using DNA methylation), and brain imaging data in a biracial cohort involving 1,676 healthy human participants. These participants were derived from the Coronary Artery Risk Development in Young Adults (CARDIA) study. The CARDIA study began in 1985 with the aim of tracking changes in cardiovascular disease risk factors among thousands of young-adult to middle-age participants. The average age of participants in this current study was 40 years old.

Participants were evaluated for cognitive function using three tests: the Rey Auditory Verbal Learning Test (RAVLT), Trail Making Test B-A (TMTB-A) and the Digit Symbol Coding Test (DSCT). The researchers assessed and re-analyzed the cohort twice (up to 15 years apart). Data were generated for two separate sub-studies. The first sub-study looked specifically at DNA methylation (DNAm) data using GrimAge, PhenoAge, Hannum’s DNAm Age, and Horvath’s DNAm Age. The second sub-study collected neuroimaging data from participants using magnetic resonance imaging (MRI) scans.

“While blood-derived epigenetic aging markers have shown predictive value years before age-related diseases occur [21–23], biological aging rates can differ across organ systems, so predictors derived directly from the brain may hold unique information for cognition [24, 25].”

The researchers note that aging-related brain atrophy occurs in a predictable manner across the human lifespan. Therefore, brain atrophy is the measure of brain aging identified by MRI scans in this study. To translate the atrophy of brain structures into a biomarker of aging, the team leveraged machine-learning algorithms to generate a composite age-related morphological index called the Spatial Pattern of Atrophy for Recognition (SPARE) of Brain Age (SPARE-BA).

“The goal of the present study was to quantify the associations of epigenetic age acceleration and SPARE-BA acceleration with subsequent cognitive performance in a biracial cohort (~40% Black participants and ~60% White participants) of middle-aged adults with 5 to 15 years of follow up.”

The Results

Out of the four epigenetic aging markers examined, the researchers found that GrimAA was uniquely capable of closely predicting worse cognitive outcomes in this middle-aged CARDIA population. In the long term, biomarkers of epigenetic aging were more stable predictors of cognitive decline than the brain aging biomarker. However, changes in SPARE-BA and the SPARE-BA acceleration (SPARE-BAA) index showed stronger associations with cognition over time than any of the epigenetic aging markers. The researchers believe this is because the brain age/aging biomarkers may be more temporally dynamic in association with cognitive decline. When the researchers compared each biomarker’s association with cognition, they found that a combined model of GrimAA and SPARE-BAA demonstrated an improved ability to predict lower cognitive performance.

“GrimAA and SPARE-BAA were not correlated with one another, indicating that they capture distinct facets of biological aging.”

Conclusion

The researchers were forthcoming about limitations in this study. The epigenetic and brain imaging markers were mostly derived from different participants within the study, therefore, other unmeasured factors may have contributed to the study results. Baseline cognitive data was not recorded at younger ages and epigenetic markers were collected at different time points than cognitive and neuroimaging outcomes. These differences inhibited cross-sectional analysis of epigenetic and brain aging. In addition, predictions may be better validated with extended follow-up periods. Nonetheless, this research may have identified two profoundly useful indicators of cognitive decline that could be put to use as early as middle-age—a potential “tipping point” in the human lifespan; when interventions may still prevent irreversible cognitive impairment.

“With further validation, epigenetic and brain aging markers may help aid timely identification of individuals at risk for accelerated cognitive decline and promote the development of interventions to preserve optimal functioning across the lifespan.”

Click here to read the full research paper published by Aging (Aging-US).

AGING (AGING-US) VIDEOS: YouTube | LabTube | Aging-US.com

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Aging (Aging-US) is an open-access journal that publishes research papers bi-monthly in all fields of aging research. These papers are available to read at no cost to readers on Aging-us.com. Open-access journals offer information that has the potential to benefit our societies from the inside out and may be shared with friends, neighbors, colleagues, and other researchers, far and wide.

For media inquiries, please contact media@impactjournals.com.

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