MicroRNA predicts cognitive performance in healthy older adults

Blood-based microRNAs as the potential biomarkers for Alzheimer's disease: evidence from a systematic review

Alzheimer's disease (AD) is a neurodegenerative disorder that progresses over time and is identified by the development of neurofibrillary tangles and amyloid deposits in the brain. Mounting evidence has revealed that microRNAs (miRNAs) are significantly involved in AD progression, and may be used as promising biomarkers for diagnosis and prognosis. Nevertheless, the existing body of data regarding dysregulated circulating miRNAs in AD and their therapeutic applications are characterized by a lack of consistency. A comprehensive search was performed across various databases (PubMed, EMBASE, Web of Science, Scopus, Google Scholar, Cochrane, and ProQuest), starting from its inception and ending in January 2023. The criteria for inclusion consisted of original research studies written in English, which utilized Real-Time PCR to analyze miRNA expression in the blood, serum, or plasma of AD patients and healthy controls. The extracted data included the miRNA(s) investigated, dysregulation status, study type, human sample(s), and major findings. The search produced 608 records, which after careful examination, resulted in 48 suitable articles for data extraction. The research revealed a wide range of sample types used, with whole blood (39.59%) and serum (27.09%, including serum-exosome at 4.17%) emerging as the most prominent. The compiled dataset featured 4001 AD patients and 3886 healthy controls, revealing intricate regulatory patterns among 83 up-regulated (35.78%), 66 down-regulated (28.44%), and 83 not significantly altered (35.78%) miRNAs. Our results demonstrated that specific circulating miRNAs are consistently dysregulated in AD and could serve as non-intrusive biomarkers for the identification, prognosis, and prediction of cognitive decline. Further large-scale prospective studies are required to validate their clinical applications.

MicroRNA Profiles in Hematopoietic Stem Cell Transplant Recipients

Background: Hematopoietic Stem Cell Transplant (HCT) is a potentially curative treatment for hematologic malignancies, including multiple myeloma. Biomarker investigation can guide identification of HCT recipients at-risk for poor outcomes. MicroRNAs (miRNAs) are a class of non-coding RNAs involved in the modulation and regulation of pathological processes and are emerging as prognostic and predictive biomarkers for multiple health conditions. This pilot study aimed to examine miRNA profiles associated with HCT-related risk factors and outcomes in patients undergoing autologous HCT. Methods: Patients eligible for autologous HCT were recruited and blood samples and HCT-related variables were collected. Differential expression analysis of miRNA was conducted on 24 patient samples to compare changes in miRNA profile in HCT eligible patients before and after transplant. Results: Unsupervised clustering of differentially expressed (p < .05) miRNAs pre- and post- HCT identified clusters of up- and down-regulated miRNAs. Four miRNAs (miR-125a-5p, miR-99b-5p, miR-382-5p, miR-145-5p) involved in hematopoiesis (differentiation of progenitor cells, granulocyte function, thrombopoiesis, and tumor suppression) were significantly downregulated post-HCT. Correlation analyses identified select miRNAs associated with risk factors (such as frailty, fatigue, cognitive decline) and quality of life pre- and post-HCT. Select miRNAs were correlated with platelet engraftment. Conclusion: Future studies should examine miRNA signatures in larger cohorts in association with HCT outcomes; and expand investigations in patients receiving allogeneic transplants. This will lead to identification of biomarkers for risk stratification of HCT recipients.

Circulating microRNA miR-425-5p Associated with Brain White Matter Lesions and Inflammatory Processes

White matter lesions (WML) emerge as a consequence of vascular injuries in the brain. While they are commonly observed in aging, associations have been established with neurodegenerative and neurological disorders such as dementia or stroke. Despite substantial research efforts, biological mechanisms are incomplete and biomarkers indicating WMLs are lacking. Utilizing data from the population-based Study of Health in Pomerania (SHIP), our objective was to identify plasma-circulating micro-RNAs (miRNAs) associated with WMLs, thus providing a foundation for a comprehensive biological model and further research. In linear regression models, direct association and moderating factors were analyzed. In 648 individuals, we identified hsa-miR-425-5p as directly associated with WMLs. In subsequent analyses, hsa-miR-425-5p was found to regulate various genes associated with WMLs with particular emphasis on the SH3PXD2A gene. Furthermore, miR-425-5p was found to be involved in immunological processes. In addition, noteworthy miRNAs associated with WMLs were identified, primarily moderated by the factors of sex or smoking status. All identified miRNAs exhibited a strong over-representation in neurodegenerative and neurological diseases. We introduced hsa-miR-425-5p as a promising candidate in WML research probably involved in immunological processes. Mir-425-5p holds the potential as a biomarker of WMLs, shedding light on potential mechanisms and pathways in vascular dementia.

Non-Coding RNA in Microglia Activation and Neuroinflammation in Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by complex pathophysiological features. Amyloid plaques resulting from extracellular amyloid deposition and neurofibrillary tangles formed by intracellular hyperphosphorylated tau accumulation serve as primary neuropathological criteria for AD diagnosis. The activation of microglia has been closely associated with these pathological manifestations. Non-coding RNA (ncRNA), a versatile molecule involved in various cellular functions such as genetic information storage and transport, as well as catalysis of biochemical reactions, plays a crucial role in microglial activation. This review aims to investigate the regulatory role of ncRNAs in protein expression by directly targeting genes, proteins, and interactions. Furthermore, it explores the ability of ncRNAs to modulate inflammatory pathways, influence the expression of inflammatory factors, and regulate microglia activation, all of which contribute to neuroinflammation and AD. However, there are still significant controversies surrounding microglial activation and polarization. The categorization into M1 and M2 phenotypes may oversimplify the intricate and multifaceted regulatory processes in microglial response to neuroinflammation. Limited research has been conducted on the role of ncRNAs in regulating microglial activation and inducing distinct polarization states in the context of neuroinflammation. Moreover, the regulatory mechanisms through which ncRNAs govern microglial function continue to be refined. The current understanding of ncRNA regulatory pathways involved in microglial activation remains incomplete and may be influenced by spatial, temporal, and tissue-specific factors. Therefore, further in-depth investigations are warranted. In conclusion, there are ongoing debates and uncertainties regarding the activation and polarization of microglial cells, particularly concerning the categorization into M1 and M2 phenotypes. The study of ncRNA regulation in microglial activation and polarization, as well as its mechanisms, is still in its early stages and requires further investigation. However, this review offers new insights and opportunities for therapeutic approaches in AD. The development of ncRNA-based drugs may hold promise as a new direction in AD treatment.

Serum microRNA-501-3p is a potential diagnostic tool for detecting mild cognitive impairment: Ehime genome study

Tight junction disruption and dysfunction are involved in the progression of blood-brain barrier (BBB) breakdown. Recent investigations have revealed BBB disruption in patients with vascular cognitive decline. Our previous studies showed that miR-501-3p negatively regulates cerebral endothelial tight junction protein-1, resulting in the disruption of the BBB, and playing an important role in the development of vascular cognitive impairment. BBB breakdown in white matter lesions is often seen in the patients with vascular mild cognitive impairment (MCI). We therefore hypothesize that most early-phase MCI patients may demonstrate elevated expression of miR-501-3p and sought to investigate whether serum exosome miR-501-3p levels could be a clinical indicator for detecting mild cognitive impairment. One hundred and seventy-eight subjects (aged 73 [68-75] years, 53% male) were recruited for this study. The Japanese version of the Montreal Cognitive Assessment (MoCA-J) was used for detecting MCI. Serum exosome miR-501-3p expression levels were measured by qPCR methods. Patients were divided into two groups depending on whether their miR-501-3p ∆Ct values were above ("High"; n = 74) or below ("Low"; n = 104) cutoff levels determined by ROC curve. MCI was detected significantly more often in the miR-501-3p-High group (vs. -Low group, 63.5% vs. 47.1%, respectively; p < 0.05). Multivariate logistic regression analysis showed a significant association between MCI status and High miR-501-3p (odds ratio 2.662; p < 0.01), improved vs. known risk factors. In non-diabetic patients, High miR-501-3p was positively associated with MCI status (odds ratio 3.633; p < 0.01) and also positively associated with MCI status in those with atherosclerosis (odds ratio 3.219; p < 0.01). The present study demonstrates that elevated expression of blood exosomal miR-501-3p can indicate the presence of MCI in human patients. Early detection of vascular injuries may allow a reduction in progressive dementia through the management of vascular risk factors.

Synergistic, long-term effects of glutamate dehydrogenase 1 deficiency and mild stress on cognitive function and mPFC gene and miRNA expression

Glutamate abnormalities in the medial prefrontal cortex (mPFC) are associated with cognitive deficits. We previously showed that homozygous deletion of CNS glutamate dehydrogenase 1 (Glud1), a metabolic enzyme critical for glutamate metabolism, leads to schizophrenia-like behavioral abnormalities and increased mPFC glutamate; mice heterozygous for CNS Glud1 deletion (C-Glud1^+/- mice) showed no cognitive or molecular abnormalities. Here, we examined the protracted behavioral and molecular effects of mild injection stress on C-Glud1^+/- mice. We found spatial and reversal learning deficits, as well as large-scale mPFC transcriptional changes in pathways associated with glutamate and GABA signaling, in stress-exposed C-Glud1^+/- mice, but not in their stress-naïve or C-Glud1^+/+ littermates. These effects were observed several weeks following stress exposure, and the expression levels of specific glutamatergic and GABAergic genes differentiated between high and low reversal learning performance. An increase in miR203-5p expression immediately following stress may provide a translational regulatory mechanism to account for the delayed effect of stress exposure on cognitive function. Our findings show that chronic glutamate abnormalities interact with acute stress to induce cognitive deficits, and resonate with gene x environment theories of schizophrenia. Stress-exposed C-Glud1^+/- mice may model a schizophrenia high-risk population, which is uniquely sensitive to stress-related 'trigger' events.

Role of MicroRNA-502-3p in Human Diseases

MicroRNAs (miRNAs) are non-coding RNAs that play a major role in gene regulation in several diseases. MicroRNA-502-3p (MiR-502-3p) has been previously characterized in a variety of human diseases such as osteoporosis, diabetes, tuberculosis, cancers, and neurological disorders. Our studies recently explored the new role of miR-502-3p in regulating synapse function in Alzheimer’s disease (AD). AD is the most common cause of dementia in elderly individuals. Synapse is the initial target that is hit during AD progression. The most common causes of synapse dysfunction in AD are amyloid beta, hyperphosphorylated tau, and microglia activation. MiR-502-3p was found to be localized and overexpressed in the AD synapses. Overexpression of miR-502-3p was correlated with AD severity in terms of Braak stages. Studies have shown that miR-502-3p modulates the glutaminergic and GABAergic synapse function in AD. The current study’s emphasis is to discuss the in-depth roles of miR-502-3p in human diseases and AD and the future possibilities concerning miR-502-3p as a therapeutic for AD treatment.

Infant Saliva Levels of microRNA miR-151a-3p Are Associated with Risk for Neurodevelopmental Delay

Prompt recognition of neurodevelopmental delay is critical for optimizing developmental trajectories. Currently, this is achieved with caregiver questionnaires whose sensitivity and specificity can be limited by socioeconomic and cultural factors. This prospective study of 121 term infants tested the hypothesis that microRNA measurement could aid early recognition of infants at risk for neurodevelopmental delay. Levels of four salivary microRNAs implicated in childhood autism (miR-125a-5p, miR-148a-5p, miR-151a-3p, miR-28-3p) were measured at 6 months of age, and compared between infants who displayed risk for neurodevelopmental delay at 18 months (n = 20) and peers with typical development (n = 101), based on clinical evaluation aided by the Survey of Wellbeing in Young Children (SWYC). Accuracy of microRNAs for predicting neurodevelopmental concerns at 18 months was compared to the clinical standard (9-month SWYC). Infants with neurodevelopmental concerns at 18 months displayed higher levels of miR-125a-5p (d = 0.30, p = 0.018, adj p = 0.049), miR-151a-3p (d = 0.30, p = 0.017, adj p = 0.048), and miR-28-3p (d = 0.31, p = 0.014, adj p = 0.048). Levels of miR-151a-3p were associated with an 18-month SWYC score (R = -0.19, p = 0.021) and probability of neurodevelopmental delay at 18 months (OR = 1.91, 95% CI, 1.14-3.19). Salivary levels of miR-151a-3p enhanced predictive accuracy for future neurodevelopmental delay (p = 0.010, X² = 6.71, AUC = 0.71) compared to the 9-month SWYC score alone (OR = 0.56, 95% CI, 0.20-1.58, AUC = 0.567). This pilot study provides evidence that miR-151a-3p may aid the identification of infants at risk for neurodevelopmental delay. External validation of these findings is necessary.

MicroRNA-140-5p inhibitor attenuates memory impairment induced by amyloid-ß oligomer in vivo possibly through Pin1 regulation

AIMS

The peptidyl-prolyl cis/trans isomerase, Pin1, has a protective role in age-related neurodegeneration by targeting different phosphorylation sites of tau and the key proteins required to produce Amyloid-β, which are the well-known molecular signatures of Alzheimer's disease (AD) neuropathology. The direct interaction of miR-140-5p with Pin1 mRNA and its inhibitory role in protein translation has been identified. The main purpose of this study was to investigate the role of miRNA-140-5p inhibition in promoting Pin1 expression and the therapeutic potential of the AntimiR-140-5p in the Aß oligomer (AßO)-induced AD rat model.

METHODS

Spatial learning and memory were assessed in the Morris water maze. RT-PCR, western blot, and histological assays were performed on hippocampal samples at various time points after treatments. miRNA-140-5p inhibition enhanced Pin1 and ADAM10 mRNA expressions but has little effect on Pin1 protein level.

RESULTS

The miRNA-140-5p inhibitor markedly ameliorated spatial learning and memory deficits induced by AßO, and concomitantly suppressed the mRNA expression of inflammatory mediators TNFα and IL-1β, and phosphorylation of tau at three key sites (thr231, ser396, and ser404) as well as increased phosphorylated Ser473-Akt.

CONCLUSION

According to our results, Antimir-140-mediated improvement of AβO-induced neuronal injury and memory impairment in rats may provide an appropriate rationale for evaluating miR-140-5p inhibitors as a promising agent for the treatment of AD.

miR-140-5p and miR-140-3p: Key Actors in Aging-Related Diseases?

microRNAs (miRNAs) are small single strand non-coding RNAs and powerful gene expression regulators. They mainly bind to the 3′UTR sequence of targeted mRNA, leading to their degradation or translation inhibition. miR-140 gene encodes the pre-miR-140 that generates the two mature miRNAs miR-140-5p and miR-140-3p. miR-140-5p/-3p have been associated with the development and progression of cancers, but also non-neoplastic diseases. In aging-related diseases, miR-140-5p and miR-140-3p expressions are modulated. The seric levels of these two miRNAs are used as circulating biomarkers and may represent predictive tools. They are also considered key actors in the pathophysiology of aging-related diseases. miR-140-5p/-3p repress targets regulating cell proliferation, apoptosis, senescence, and inflammation. This work focuses on the roles of miR-140-3p and miR-140-5p in aging-related diseases, details their regulation (i.e., by long non-coding RNA), and reviews the molecular targets of theses miRNAs involved in aging pathophysiology.

Precision machine learning to understand micro-RNA regulation in neurodegenerative diseases

Micro-RNAs (miRNAs) are short (∼21 nt) non-coding RNAs that regulate gene expression through the degradation or translational repression of mRNAs. Accumulating evidence points to a role of miRNA regulation in the pathogenesis of a wide range of neurodegenerative (ND) diseases such as, for example, Alzheimer’s disease, Parkinson’s disease, amyotrophic lateral sclerosis and Huntington disease (HD). Several systems level studies aimed to explore the role of miRNA regulation in NDs, but these studies remain challenging. Part of the problem may be related to the lack of sufficiently rich or homogeneous data, such as time series or cell-type-specific data obtained in model systems or human biosamples, to account for context dependency. Part of the problem may also be related to the methodological challenges associated with the accurate system-level modeling of miRNA and mRNA data. Here, we critically review the main families of machine learning methods used to analyze expression data, highlighting the added value of using shape-analysis concepts as a solution for precisely modeling highly dimensional miRNA and mRNA data such as the ones obtained in the study of the HD process, and elaborating on the potential of these concepts and methods for modeling complex omics data.

Loss of schizophrenia-related miR-501-3p in mice impairs sociability and memory by enhancing mGluR5-mediated glutamatergic transmission

Schizophrenia is a polygenetic disease, the heterogeneity of which is likely complicated by epigenetic modifications yet to be elucidated. Here, we performed transcriptomic analysis of peripheral blood RNA from monozygotic twins discordant for schizophrenia and identified a schizophrenia-associated down-regulated microRNA, miR-501-3p. We showed that the loss of miR-501-3p in germline knockout (KO) male mice resulted in dendritic structure defects, glutamatergic transmission enhancement, and sociability, memory, and sensorimotor gating disruptions, which were attenuated when miR-501 expression was conditionally restored in the nervous system. Combining the results of proteomic analyses with the known genes linked to schizophrenia revealed that metabotropic glutamate receptor 5 (mGluR5) was one of the miR-501-3p targets and was elevated in vivo upon loss of miR-501. Treatment with the mGluR5 negative allosteric modulator 3-2((-methyl-4-thiazolyl) ethynyl) pyridine or the N-methyl-d-aspartate receptor antagonist 2-amino-5-phosphonopentanoic acid ameliorated the deficits observed in Mir501-KO mice. The epigenetic and pathophysiological mechanism that links miR-501-3p to the modulation of glutamatergic transmission provides etiological implications for schizophrenia.

Genome-wide profiling of circulatory microRNAs associated with cognition and dementia

INTRODUCTION

MicroRNAs (miRNAs) are post-transcriptional regulators of gene expression. Their role in the pathophysiology of dementia and potential as biomarkers remains undetermined.

METHODS

We conducted a single- (one-by-one) and multi-marker (joint) analysis to identify well-expressed circulating miRNAs in plasma (total = 591) associated with general cognition and incident dementia, for 1615 participants of the population-based Rotterdam Study.

RESULTS

During single-marker analysis, 47 miRNAs were nominally (P ≤ .05) associated with cognition and 18 miRNAs were nominally associated with incident dementia, after adjustment for potential confounders. Three miRNAs were common between cognition and dementia (miR-4539, miR-372-3p, and miR-566), with multi-marker analysis revealing another common miRNA (miR-7106-5p). In silico analysis of these four common miRNAs led to several putative target genes expressed in the brain, highlighting the mitogen-activated protein kinase signaling pathway.

DISCUSSION

We provide population-based evidence on the relationship between circulatory miRNAs with cognition and dementia, including four common miRNAs that may elucidate downstream mechanisms.

HIGHLIGHTS

MicroRNAs (miRNAs) are involved in the (dys)function of the central nervous system. Four circulating miRNAs in plasma are associated with cognition and incident dementia. Several predicted target genes of these four miRNAs are expressed in the brain. These four miRNAs may be linked to pathways underlying dementia. Although miRNAs are promising biomarkers, experimental validation remains essential.

Biomarkers of Frailty: miRNAs as Common Signatures of Impairment in Cognitive and Physical Domains

The past years have seen an increasing concern about frailty, owing to the growing number of elderly people and the major impact of this syndrome on health and social care. The identification of frail people passes through the use of different tests and biomarkers, whose concerted analysis helps to stratify the populations of patients according to their risk profile. However, their efficiency in prognosis and their capability to reflect the multisystemic impairment of frailty is discussed. Recent works propose the use of miRNAs as biological hallmarks of physiological impairment in different organismal districts. Changes in miRNAs expression have been described in biological processes associated with phenotypic outcomes of frailty, opening intriguing possibilities for their use as biomarkers of fragility. Here, with the aim of finding reliable biomarkers of frailty, while considering its complex nature, we revised the current literature on the field, for uncovering miRNAs shared across physical and cognitive frailty domains. By applying in silico analyses, we retrieved the top-ranked shared miRNAs and their targets, finally prioritizing the most significant ones. From this analysis, ten miRNAs emerged which converge into two main biological processes: inflammation and energy homeostasis. Such markers, if validated, may offer promising capabilities for early diagnosis of frailty in the elderly population.

Trehalose Attenuates Learning and Memory Impairments in Aged Rats via Overexpression of miR-181c

MicroRNAs have been recognized as important regulators of the aging process. Trehalose, a natural disaccharide, displays protective effects against neuronal impairment through several mechanisms. However, little is known about the interactive effects of aging and trehalose on behavioral function and underlying miRNA expression patterns in the hippocampus of young and old rats. Male Wistar rats were divided into four groups. Two groups of aged (24 months) and young (4 months) rats were administered 2% trehalose solution for 30 days. Two other groups of aged and young rats received regular tap water. At the end of treatment, rats were assessed for cognitive behavior using the Morris water maze test. The expression level of miR-181c and mir-34c was also measured by qRT-PCR. We found that trehalose treatment reduced learning and memory impairment in old rats compared to control old animals (p < 0.05). In contrast, cognitive performance was not significantly improved in trehalose-treated young rats in comparison with young controls (p > 0.05). We also showed that the expression level of miR-181c was significantly increased in trehalose-treated rats (p < 0.01). However, analysis of miR-34c expression level indicated no significant difference between trehalose-treated old rats and non-treated old animals (p > 0.05). Our results indicated that trehalose treatment improved learning and memory function in aged rats by targeting miR-181c. Therefore, trehalose administration may provide a therapeutic strategy to ameliorate age-associated cognitive impairment.

Blood-Based Biomarkers for Alzheimer's Disease Diagnosis and Progression: An Overview

Alzheimer's Disease (AD) is a progressive neurodegenerative disease characterized by amyloid-β (Aβ) plaque deposition and neurofibrillary tangle accumulation in the brain. Although several studies have been conducted to unravel the complex and interconnected pathophysiology of AD, clinical trial failure rates have been high, and no disease-modifying therapies are presently available. Fluid biomarker discovery for AD is a rapidly expanding field of research aimed at anticipating disease diagnosis and following disease progression over time. Currently, Aβ1-42, phosphorylated tau, and total tau levels in the cerebrospinal fluid are the best-studied fluid biomarkers for AD, but the need for novel, cheap, less-invasive, easily detectable, and more-accessible markers has recently led to the search for new blood-based molecules. However, despite considerable research activity, a comprehensive and up-to-date overview of the main blood-based biomarker candidates is still lacking. In this narrative review, we discuss the role of proteins, lipids, metabolites, oxidative-stress-related molecules, and cytokines as possible disease biomarkers. Furthermore, we highlight the potential of the emerging miRNAs and long non-coding RNAs (lncRNAs) as diagnostic tools, and we briefly present the role of vitamins and gut-microbiome-related molecules as novel candidates for AD detection and monitoring, thus offering new insights into the diagnosis and progression of this devastating disease.

Exosomes in Age-Related Cognitive Decline: Mechanistic Insights and Improving Outcomes

Aging is the most prominent risk factor for cognitive decline, yet behavioral symptomology and underlying neurobiology can vary between individuals. Certain individuals exhibit significant age-related cognitive impairments, while others maintain intact cognitive functioning with only minimal decline. Recent developments in genomic, proteomic, and functional imaging approaches have provided insights into the molecular and cellular substrates of cognitive decline in age-related neuropathologies. Despite the emergence of novel tools, accurately and reliably predicting longitudinal cognitive trajectories and improving functional outcomes for the elderly remains a major challenge. One promising approach has been the use of exosomes, a subgroup of extracellular vesicles that regulate intercellular communication and are easily accessible compared to other approaches. In the current review, we highlight recent findings which illustrate how the analysis of exosomes can improve our understanding of the underlying neurobiological mechanisms that contribute to cognitive variation in aging. Specifically, we focus on exosome-mediated regulation of miRNAs, neuroinflammation, and aggregate-prone proteins. In addition, we discuss how exosomes might be used to enhance individual patient outcomes by serving as reliable biomarkers of cognitive decline and as nanocarriers to deliver therapeutic agents to the brain in neurodegenerative conditions.

Exosomes and their Cargo as a New Avenue for Brain and Treatment of CNS-Related Diseases

Extracellular Vesicles (EVs), which belong to nanoscale vesicles, including microvesicles (MVs) and exosomes, are now considered a new important tool for intercellular neuronal communication in the Central Nervous System (CNS) under physiological and pathological conditions. EVs are shed into blood, peripheral body fluids and cerebrospinal fluid (CSF) by a large variety of cells.

EVs can act locally on neighboring and distant cells. EVs represent the fingerprints of the originating cells and can carry a variety of molecular constituents of their cell of origin, including protein, lipids, DNA and microRNAs (miRNAs).

The most studied EVs are the exosomes because they are ubiquitous and have the capacity to transfer cell-derived components and bioactive molecules to target cells. In this minireview, we focused on cell-cell communication in CNS mediated by exosomes and their important cargo as an innovative way to treat or follow up with CNS diseases.

Influence of age and sex on microRNA response and recovery in the hippocampus following sepsis

Sepsis, defined as a dysregulated host immune response to infection, is a common and dangerous clinical syndrome. The excessive host inflammatory response can induce immediate and persistent cognitive decline, which can be worse in older individuals. Sex-specific differences in the outcome of infectious diseases and sepsis appear to favor females. We employed a murine model to examine the influence of age and sex on the brain's microRNA (miR) response following sepsis. Young and old mice of both sexes underwent cecal ligation and puncture (CLP) with daily restraint stress. Expression of hippocampal miR was examined in age- and sex-matched controls at 1 and 4 days post-CLP. Few miR were modified in a similar manner across age or sex and these few miR were generally associated with neuroprotection against inflammation. Similar to previous work examining transcription, young females exhibited a better recovery of the miR profile from day 1 to day 4, relative to young males and old females. For young males and all female groups, the initial response mainly involved a decrease in miR expression. In contrast, old males exhibited only upregulated miR on day 1 and day 4 and many of the miR upregulated on day 1 and day 4 were linked to neurodegeneration, increased neuroinflammation, and cognitive impairment. The results emphasize age and sex differences in epigenetic mechanisms that likely contribute to susceptibility or resilience to cognitive impairment due to sepsis.

The Potential Role of miRNAs in Cognitive Frailty

Frailty is an aging related condition, which has been defined as a state of enhanced vulnerability to stressors, leading to a limited capacity to meet homeostatic demands. Cognitive impairment is also frequent in older people, often accompanying frailty. Age is the main independent risk factor for both frailty and cognitive impairment, and compelling evidence suggests that similar age-associated mechanisms could underlie both clinical conditions. Accordingly, it has been suggested that frailty and cognitive impairment share common pathways, and some authors proposed "cognitive frailty" as a single complex phenotype. Nevertheless, so far, no clear common underlying pathways have been discovered for both conditions. microRNAs (miRNAs) have emerged as key fine-tuning regulators in most physiological processes, as well as pathological conditions. Importantly, miRNAs have been proposed as both peripheral biomarkers and potential molecular factors involved in physiological and pathological aging. In this review, we discuss the evidence linking changes of selected miRNAs expression with frailty and cognitive impairment. Overall, miR-92a-5p and miR-532-5p, as well as other miRNAs implicated in pathological aging, should be investigated as potential biomarkers (and putative molecular effectors) of cognitive frailty.

Potential Roles of miRNA-1245a Regulatory Networks in Sarcopenia

Objective

Sarcopenia is a universal problem in elderly individuals. The molecular regulatory mechanisms in sarcopenia are not well understood. In the present study, we explored a possible molecular mechanism involved in the pathogenesis of sarcopenia.

Methods

Differentially expressed genes (DEGs) were identified using the Gene Expression Omnibus (GEO) database. Signaling pathways related to these DEGs were identified by gene set enrichment analysis (GSEA). Pearson correlation was calculated for all the pairwise comparisons of gene expression values between coding genes and DEGs. Interactions between the proteins encoded by the DEGs were identified using the STRING database. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) biological pathway analyses were performed to predict the functions of the DEGs.

Results

Three differentially expressed miRNAs and 5 differentially expressed mRNAs were identified in association with DEGs. We found that miRNA-1245a expression in patients with sarcopenia was higher than that in healthy controls. The GSEA showed that many pathways, such as the JAK-STAT signaling pathway and pathways related to glioma, gap junctions, and regulation of the actin cytoskeleton, were enriched in the high-miRNA-1245a-expression group. A total of 127 miRNA-1245a-related mRNAs were identified. The GO and KEGG analyses revealed that miRNA-1245a had a strong effect on a number of fundamental biological processes, such as kinase activity, that are related to the development of sarcopenia.

Conclusion

Our analyses indicate that miRNA-1245a may be a potential key molecule in the diagnosis and treatment of sarcopenia, which provides a basis for the research of miRNA in sarcopenia.

Exercise as a model to identify microRNAs linked to human cognition: a role for microRNA-409 and microRNA-501

MicroRNAs have been linked to synaptic plasticity and memory function and are emerging as potential biomarkers and therapeutic targets for cognitive diseases. Most of these data stem from the analysis of model systems or postmortem tissue from patients which mainly represents an advanced stage of pathology. Due to the in-accessibility of human brain tissue upon experimental manipulation, it is still challenging to identify microRNAs relevant to human cognition, which is however a key step for future translational studies. Here, we employ exercise as an experimental model for memory enhancement in healthy humans with the aim to identify microRNAs linked to memory function. By analyzing the circulating smallRNAome we find a cluster of 18 microRNAs that are highly correlated to cognition. MicroRNA-409-5p and microRNA-501-3p were the most significantly regulated candidates. Functional analysis revealed that the two microRNAs are important for neuronal integrity, synaptic plasticity, and morphology. In conclusion, we provide a novel approach to identify microRNAs linked to human memory function.

Functional predication of differentially expressed circRNAs/lncRNAs in the prefrontal cortex of Nrf2-knockout mice

In the central nervous system, nuclear factor erythroid-2-related factor 2 (Nrf2) protects neurons from oxidant injury, thereby ameliorating neurodegeneration. We explored the key circular RNAs (circRNAs) and long non-coding RNAs (lncRNAs) involved in Nrf2-induced neuroprotection. We used microarrays to examine the circRNAs (DEcircRNAs), lncRNAs (DElncRNAs) and mRNAs (DEmRNAs) differentially expressed between Nrf2 (+/+) and Nrf2 (-/-) mice and identified DEcircRNA/DElncRNA-miRNA-DEmRNA interaction networks. In total, 197 DEcircRNAs, 685 DElncRNAs and 356 DEmRNAs were identified in prefrontal cortical tissues from Nrf2 (-/-) mice. The expression patterns of selected DEcircRNAs (except for mmu_circ_0003404) and DElncRNAs in qRT-PCR analyses were generally consistent with the microarray analysis results. Functional annotation of the DEmRNAs in the DEcircRNA/DElncRNA-miRNA-DEmRNA networks indicated that five non-coding RNAs (mmu_circ_0000233, ENSMUST00000204847, NONMMUT024778, NONMMUT132160 and NONMMUT132168) may contribute to Nrf2 activity, with the help of mmu_circ_0015035 and NONMMUT127961. The results also revealed that four non-coding RNAs (cicRNA.20127, mmu_circ_0012936, ENSMUST00000194077 and NONMMUT109267) may influence glutathione metabolism. Additionally, 44 DEcircRNAs and 7 DElncRNAs were found to possess coding potential. These findings provide clues to the molecular pathways through which Nrf2 protects neurons.

Social Isolation and Enrichment Induce Unique miRNA Signatures in the Prefrontal Cortex and Behavioral Changes in Mice

An extensive body of evidence supports the notion that exposure to an enriched/impoverished environment alters brain functions via epigenetic changes. However, how specific modifications of social environment modulate brain functions remains poorly understood. To address this issue, we investigate the molecular and behavioral consequences of briefly manipulating social settings in young and middle-aged wild-type mice. We observe that, modifications of the social context, only affect the performance in socially related tasks. Social enrichment increases sociability whereas isolation leads to the opposite effect. Our work also pointed out specific miRNA signatures associated to each social environment. These miRNA alterations are reversible and found selectively in the medial prefrontal cortex. Finally, we show that miRNA modifications linked to social enrichment or isolation might target rather different intracellular pathways. Together, these observations suggest that the prefrontal cortex may be a key brain area integrating social information via the modification of precise miRNA networks.

A hypothesis-generating scoping review of miRs identified in both multiple sclerosis and dementia, their protein targets, and miR signaling pathways

Cognitive impairment (CI) is a frequent complication affecting people with multiple sclerosis (MS). The causes of CI in MS are not fully understood. Besides MRI measures, few other biomarkers exist to help us predict the development of CI and understand its biology. MicroRNAs (miRs) are relatively stable, non-coding RNA molecules about 22 nucleotides in length that can serve as biomarkers and possible therapeutic targets in several autoimmune and neurodegenerative diseases, including the dementias. In this review, we identify dysregulated miRs in MS that overlap with dysregulated miRs in cognitive disorders and dementia and explore how these overlapping miRs play a role in CI in MS. MiR-15, miR-21, miR-128, miR-132, miR-138, miR-142, miR-146a, miR-155, miR-181, miR-572, and let-7 are known to contribute to various forms of dementia and show abnormal expression in MS. These overlapping miRs are involved in pathways related to apoptosis, neuroinflammation, glutamate toxicity, astrocyte activation, microglial burst activity, synaptic dysfunction, and remyelination. The mechanisms of action suggest that these miRs may be related to CI in MS. From our review, we also delineated miRs that could be neuroprotective in MS, namely miR-23a, miR-219, miR-214, and miR-22. Further studies can help clarify if these miRs are responsible for CI in MS, leading to potential therapeutic targets.