A Versatile eIF3d in Translational Control of Stress Adaptation.

Lamper et al. (2020) reported that eIF3d-mediated cap-dependent translation is subject to regulation by phosphorylation during chronic glucose deprivation, providing a mechanism underlying selective translation of stress genes essential for cell survival.

Systemic inflammatory markers in ageing, Alzheimer's disease and other dementias.

Systemic inflammation with alterations in inflammatory markers is involved in aging and Alzheimer's disease. However, few studies have investigated the longitudinal trajectories of systemic inflammatory markers during aging and Alzheimer's disease, and specific markers contributing to Alzheimer's disease remain undetermined. In this study, a longitudinal cohort (cohort 1: n = 290; controls, 136; preclinical Alzheimer's disease, 154) and a cross-sectional cohort (cohort 2: n = 351; controls, 62; Alzheimer's disease, 63; vascular dementia, 58; Parkinson's disease dementia, 56; behavioural variant frontotemporal dementia, 57; dementia with Lewy bodies, 55) were included. Plasma levels of inflammatory markers were measured every 2 years during a 10-year follow-up in the longitudinal cohort and once in the cross-sectional cohort. The study demonstrated that the inflammatory markers significantly altered during both aging and the development of Alzheimer's disease. However, only complement C3, interleukin-1ß, and interleukin-6 exhibited significant changes in participants with preclinical Alzheimer's disease, and their longitudinal changes were significantly associated with the development of Alzheimer's disease compared to controls over the 10-year follow-up. In the cross-sectional cohort, complement C3 demonstrates specificity to Alzheimer's disease, while interleukin-1ß and interleukin-6 were also altered in other dementias. The study provides a new perspective on the involvement of inflammatory markers in the aging process and the development of Alzheimer's disease, implying that regulating inflammation may have a pivotal role in promoting successful aging and in the prevention and treatment of Alzheimer's disease.

Delivering synaptic protein mRNAs via extracellular vesicles ameliorates cognitive impairment in a mouse model of Alzheimer's disease.

BACKGROUND: Synaptic dysfunction with reduced synaptic protein levels is a core feature of Alzheimer's disease (AD). Synaptic proteins play a central role in memory processing, learning, and AD pathogenesis. Evidence suggests that synaptic proteins in plasma neuronal-derived extracellular vesicles (EVs) are reduced in patients with AD. However, it remains unclear whether levels of synaptic proteins in EVs are associated with hippocampal atrophy of AD and whether upregulating the expression of these synaptic proteins has a beneficial effect on AD. METHODS: In this study, we included 57 patients with AD and 56 healthy controls. We evaluated their brain atrophy through magnetic resonance imaging using the medial temporal lobe atrophy score. We measured the levels of four synaptic proteins, including synaptosome-associated protein 25 (SNAP25), growth-associated protein 43 (GAP43), neurogranin, and synaptotagmin 1 in both plasma neuronal-derived EVs and cerebrospinal fluid (CSF). We further examined the association of synaptic protein levels with brain atrophy. We also evaluated the levels of these synaptic proteins in the brains of 5×FAD mice. Then, we loaded rabies virus glycoprotein-engineered EVs with messenger RNAs (mRNAs) encoding GAP43 and SNAP25 and administered these EVs to 5×FAD mice. After treatment, synaptic proteins, dendritic density, and cognitive function were evaluated. RESULTS: The results showed that GAP43, SNAP25, neurogranin, and synaptotagmin 1 were decreased in neuronal-derived EVs but increased in CSF in patients with AD, and the changes corresponded to the severity of brain atrophy. GAP43 and SNAP25 were decreased in the brains of 5×FAD mice. The engineered EVs efficiently and stably delivered these synaptic proteins to the brain, where synaptic protein levels were markedly upregulated. Upregulation of synaptic protein expression could ameliorate cognitive impairment in AD by promoting dendritic density. This marks the first successful delivery of synaptic protein mRNAs via EVs in AD mice, yielding remarkable therapeutic effects. CONCLUSIONS: Synaptic proteins are closely related to AD processes. Delivery of synaptic protein mRNAs via EVs stands as a promising effective precision treatment strategy for AD, which significantly advances the current understanding of therapeutic approaches for the disease.

Dynamic eIF3a O-GlcNAcylation controls translation reinitiation during nutrient stress.

In eukaryotic cells, many messenger RNAs (mRNAs) possess upstream open reading frames (uORFs) in addition to the main coding region. After uORF translation, the ribosome could either recycle at the stop codon or resume scanning for downstream start codons in a process known as reinitiation. Accumulating evidence suggests that some initiation factors, including eukaryotic initiation factor 3 (eIF3), linger on the early elongating ribosome, forming an eIF3-80S complex. Very little is known about how eIF3 is carried along with the 80S during elongation and whether the eIF3-80S association is subject to regulation. Here, we report that eIF3a undergoes dynamic O-linked N-acetylglucosamine (O-GlcNAc) modification in response to nutrient starvation. Stress-induced de-O-GlcNAcylation promotes eIF3 retention on the elongating ribosome and facilitates activating transcription factor 4 (ATF4) reinitiation. Eliminating the modification site from eIF3a via CRISPR genome editing induces ATF4 reinitiation even under the nutrient-rich condition. Our findings illustrate a mechanism in balancing ribosome recycling and reinitiation, thereby linking the nutrient stress response and translational reprogramming.

Risk factors for diaphragmatic injury in subxiphoid video-assisted thoracoscopic surgery.

BACKGROUND: Subxiphoid video-assisted thoracoscopic surgery (VATS) is considered a safe and feasible operation for anterior mediastinal mass resection. However, diaphragmatic injury, presented as tearing or puncturing, may occur during subxiphoid VATS despite of low incidence. This study aims to explore risk factors for diaphragmatic injury in subxiphoid VATS, as well as strategies to reduce occurrence of the injury. METHODS: We retrospectively reviewed clinical records of 44 consecutive adult patients who underwent subxiphoid VATS. These patients were divided into two groups: diaphragmatic injury group and non-injury group. Perioperative outcomes and anatomic features derived from 3D CT reconstructions were compared between the two groups. RESULTS: Significant differences were observed in operation time (223.25 ± 92.57 vs. 136.28 ± 53.05, P = 0.006), xiphoid length (6.47 ± 0.85 vs. 4.79 ± 1.04, P = 0.001) and length of the xiphoid below the attachment point on the diaphragm (24.86 ± 12.02 vs. 14.61 ± 9.25, P = 0.029). Odds ratio for the length of the xiphoid below the attachment point on the diaphragm was 1.09 (1.001-1.186), P = 0.048 by binary logistic regression analysis. CONCLUSIONS: We identified the length of the xiphoid below the attachment point on the diaphragm as an independent risk factor for diaphragm injury during subxiphoid VATS. Prior to subxiphoid VATS, a 3D chest CT reconstruction is recommended to assess the patients' anatomic variations within the xiphoid process. For patients with longer xiphoid process, a higher incision at the middle and upper part of the xiphoid process, and partial xiphoid process resection or xiphoidectomy is preferred.

Exome sequencing revealed PDE11A as a novel candidate gene for early-onset Alzheimer's disease.

To identify novel risk genes and better understand the molecular pathway underlying Alzheimer's disease (AD), whole-exome sequencing was performed in 215 early-onset AD (EOAD) patients and 255 unrelated healthy controls of Han Chinese ethnicity. Subsequent validation, computational annotation and in vitro functional studies were performed to evaluate the role of candidate variants in EOAD. We identified two rare missense variants in the phosphodiesterase 11A (PDE11A) gene in individuals with EOAD. Both variants are located in evolutionarily highly conserved amino acids, are predicted to alter the protein conformation and are classified as pathogenic. Furthermore, we found significantly decreased protein levels of PDE11A in brain samples of AD patients. Expression of PDE11A variants and knockdown experiments with specific short hairpin RNA (shRNA) for PDE11A both resulted in an increase of AD-associated Tau hyperphosphorylation at multiple epitopes in vitro. PDE11A variants or PDE11A shRNA also caused increased cyclic adenosine monophosphate (cAMP) levels, protein kinase A (PKA) activation and cAMP response element-binding protein phosphorylation. In addition, pretreatment with a PKA inhibitor (H89) suppressed PDE11A variant-induced Tau phosphorylation formation. This study offers insight into the involvement of Tau phosphorylation via the cAMP/PKA pathway in EOAD pathogenesis and provides a potential new target for intervention.

Aberrant palmitoylation caused by a ZDHHC21 mutation contributes to pathophysiology of Alzheimer's disease.

BACKGROUND: The identification of pathogenic mutations in Alzheimer's disease (AD) causal genes led to a better understanding of the pathobiology of AD. Familial Alzheimer's disease (FAD) is known to be associated with mutations in the APP, PSEN1, and PSEN2 genes involved in Aß production; however, these genetic defects occur in only about 10-20% of FAD cases, and more genes and new mechanism causing FAD remain largely obscure. METHODS: We performed exome sequencing on family members with a FAD pedigree and identified gene variant ZDHHC21 p.T209S. A ZDHHC21T209S/T209S knock-in mouse model was then generated using CRISPR/Cas9. The Morris water navigation task was then used to examine spatial learning and memory. The involvement of aberrant palmitoylation of FYN tyrosine kinase and APP in AD pathology was evaluated using biochemical methods and immunostaining. Aß and tau pathophysiology was evaluated using ELISA, biochemical methods, and immunostaining. Field recordings of synaptic long-term potentiation were obtained to examine synaptic plasticity. The density of synapses and dendritic branches was quantified using electron microscopy and Golgi staining. RESULTS: We identified a variant (c.999A > T, p.T209S) of ZDHHC21 gene in a Han Chinese family. The proband presented marked cognitive impairment at 55 years of age (Mini-Mental State Examination score = 5, Clinical Dementia Rating = 3). Considerable Aß retention was observed in the bilateral frontal, parietal, and lateral temporal cortices. The novel heterozygous missense mutation (p.T209S) was detected in all family members with AD and was not present in those unaffected, indicating cosegregation. ZDHHC21T209S/T209S mice exhibited cognitive impairment and synaptic dysfunction, suggesting the strong pathogenicity of the mutation. The ZDHHC21 p.T209S mutation significantly enhanced FYN palmitoylation, causing overactivation of NMDAR2B, inducing increased neuronal sensitivity to excitotoxicity leading to further synaptic dysfunction and neuronal loss. The palmitoylation of APP was also increased in ZDHHC21T209S/T209S mice, possibly contributing to Aß production. Palmitoyltransferase inhibitors reversed synaptic function impairment. CONCLUSIONS: ZDHHC21 p.T209S is a novel, candidate causal gene mutation in a Chinese FAD pedigree. Our discoveries strongly suggest that aberrant protein palmitoylation mediated by ZDHHC21 mutations is a new pathogenic mechanism of AD, warranting further investigations for the development of therapeutic interventions.

Therapeutic mRNA Engineering from Head to Tail.

Synthetic messenger RNA (mRNA), once delivered into cells, can be readily translated into proteins by ribosomes, which do not distinguish exogenous mRNAs from endogenous transcripts. Until recently, the intrinsic instability and immunostimulatory property of exogenous RNAs largely hindered the therapeutic application of synthetic mRNAs. Thanks to major technological innovations, such as introduction of chemically modified nucleosides, synthetic mRNAs have become programmable therapeutic reagents. Compared to DNA or protein-based therapeutic reagents, synthetic mRNAs bear several advantages: flexible design, easy optimization, low-cost preparation, and scalable synthesis. Therapeutic mRNAs are commonly designed to encode specific antigens to elicit organismal immune response to pathogens like viruses, express functional proteins to replace defective ones inside cells, or introduce novel enzymes to achieve unique functions like genome editing. Recent years have witnessed stunning progress on the development of mRNA vaccines against SARS-Cov2. This success is built upon our fundamental understanding of mRNA metabolism and translational control, a knowledge accumulated during the past several decades. Given the astronomical number of sequence combinations of four nucleotides, sequence-dependent control of mRNA translation remains incompletely understood. Rational design of synthetic mRNAs with robust translation and optimal stability remains challenging. Massively paralleled reporter assay (MPRA) has been proven to be powerful in identifying sequence elements in controlling mRNA translatability and stability. Indeed, a completely randomized sequence in 5' untranslated region (5'UTR) drives a wide range of translational outputs. In this Account, we will discuss general principles of mRNA translation in eukaryotic cells and elucidate the role of coding and noncoding regions in the translational regulation. From the therapeutic perspective, we will highlight the unique features of 5' cap, 5'UTR, coding region (CDS), stop codon, 3'UTR, and poly(A) tail. By focusing on the design strategies in mRNA engineering, we hope this Account will contribute to the rational design of synthetic mRNAs with broad therapeutic potential.

Prediction of Alzheimer's disease using multi-variants from a Chinese genome-wide association study.

Previous genome-wide association studies have identified dozens of susceptibility loci for sporadic Alzheimer's disease, but few of these loci have been validated in longitudinal cohorts. Establishing predictive models of Alzheimer's disease based on these novel variants is clinically important for verifying whether they have pathological functions and provide a useful tool for screening of disease risk. In the current study, we performed a two-stage genome-wide association study of 3913 patients with Alzheimer's disease and 7593 controls and identified four novel variants (rs3777215, rs6859823, rs234434, and rs2255835; Pcombined = 3.07 × 10-19, 2.49 × 10-23, 1.35 × 10-67, and 4.81 × 10-9, respectively) as well as nine variants in the apolipoprotein E region with genome-wide significance (P < 5.0 × 10-8). Literature mining suggested that these novel single nucleotide polymorphisms are related to amyloid precursor protein transport and metabolism, antioxidation, and neurogenesis. Based on their possible roles in the development of Alzheimer's disease, we used different combinations of these variants and the apolipoprotein E status and successively built 11 predictive models. The predictive models include relatively few single nucleotide polymorphisms useful for clinical practice, in which the maximum number was 13 and the minimum was only four. These predictive models were all significant and their peak of area under the curve reached 0.73 both in the first and second stages. Finally, these models were validated using a separate longitudinal cohort of 5474 individuals. The results showed that individuals carrying risk variants included in the models had a shorter latency and higher incidence of Alzheimer's disease, suggesting that our models can predict Alzheimer's disease onset in a population with genetic susceptibility. The effectiveness of the models for predicting Alzheimer's disease onset confirmed the contributions of these identified variants to disease pathogenesis. In conclusion, this is the first study to validate genome-wide association study-based predictive models for evaluating the risk of Alzheimer's disease onset in a large Chinese population. The clinical application of these models will be beneficial for individuals harbouring these risk variants, and particularly for young individuals seeking genetic consultation.

A metabolite panel that differentiates Alzheimer's disease from other dementia types.

INTRODUCTION: Alzheimer's disease (AD) is associated with altered metabolites. This study aimed to determine the validity of using circulating metabolites to differentiate AD from other dementias. METHODS: Blood metabolites were measured in three data sets. Data set 1 (controls, 27; AD, 28) was used for analyzing differential metabolites. Data set 2 (controls, 93; AD, 92) was used to establish a diagnostic AD model with use of a metabolite panel. The model was applied to Data set 3 (controls, 76; AD, 76; other dementias, 205) to verify its capacity for differentiating AD from other dementias. RESULTS: Data set 1 revealed 7 upregulated and 77 downregulated metabolites. In Data set 2, a panel of 11 metabolites was included in a model that could distinguish AD from controls. In Data set 3, this panel was used to successfully differentiate AD from other dementias. DISCUSSION: This study revealed an AD-specific panel of 11 metabolites that may be used for AD diagnosis.

Prediction of P-tau/Aß42 in the cerebrospinal fluid with blood microRNAs in Alzheimer's disease.

BACKGROUND: The most common biomarkers of Alzheimer's disease (AD) are amyloid ß (Aß) and tau, detected in cerebrospinal fluid (CSF) or with positron emission tomography imaging. However, these procedures are invasive and expensive, which hamper their availability to the general population. Here, we report a panel of microRNAs (miRNAs) in serum that can predict P-tau/Aß42 in CSF and readily differentiate AD from other dementias, including vascular dementia (VaD), Parkinson disease dementia (PDD), behavioral variant frontotemporal dementia (bvFTD), and dementia with Lewy body (DLB). METHODS: RNA samples were extracted from the participant's blood. P-tau/Aß42 of CSF was examined for diagnostic purposes. A pilot study (controls, 21; AD, 23), followed by second (controls, 216; AD, 190) and third groups (controls, 153; AD, 151), is used to establish and verify a predictive model of P-tau/Aß42 in CSF. The test is then applied to a fourth group of patients with different dementias (controls, 139; AD,155; amnestic mild cognitive impairment [aMCI], 55; VaD, 51; PDD, 53; bvFTD, 53; DLB, 52) to assess its diagnostic capacity. RESULTS: In the pilot study, 29 upregulated and 31 downregulated miRNAs in the AD group were found. In Dataset 2, these miRNAs were then included as independent variables in the linear regression model. A seven-microRNA panel (miR-139-3p, miR-143-3p, miR-146a-5p, miR-485-5p, miR-10a-5P, miR-26b-5p, and miR-451a-5p) accurately predicted values of P-tau/Aß42 of CSF. In Datasets 3 and 4, by applying the predicted P-tau/Aß42, the predictive model successfully differentiates AD from controls and VaD, PDD, bvFTD, and DLB. CONCLUSIONS: This study suggests that the panel of microRNAs is a promising substitute for traditional measurement of P-tau/Aß42 in CSF as an effective biomarker of AD.

Cognitive profiles in adult-onset neuronal intranuclear inclusion disease: a case series from the memory clinic.

OBJECTIVE: This study aimed to analyze the characteristics of cognitive impairment in adult-onset neuronal intranuclear inclusion disease (NIID). METHODS: Seven patients with adult-onset NIID were collected consecutively from the memory clinic of Xuanwu hospital from February to December 2019. These cases were diagnosed with skin biopsy triggered by DWI high-intensity signals in corticomedullary junction on brain MRI. We used a battery of neuropsychological scales to detect the patient's performance in each cognitive domain, and made a detailed analysis on the characteristics of cognitive impairment. RESULTS: All seven cases had cognitive impairment, and four of them had met the criteria for dementia. The scores of Montreal Cognitive Assessment and Frontal Assessment Battery were abnormal in all patients. The executive dysfunction was confirmed by the abnormal scores of Trail Making Test (5/7, 71%) and Clock Drawing Test (4/7, 57%). Bad performance in Auditory Verbal Learning Test (6/7, 86%) demonstrated that the memory was also a very commonly impaired cognitive domain. The low score on the animal fluency (4/7, 57%), Boston Naming Test (3/7, 43%), and Pentagon and Cube Copying Test (4/7, 57%) indicated that the language and visuospatial skills were also impaired. Fazekas scores were significantly correlated to the global cognition, executive and language functions (r = 0.788-0.906, P < 0.05). CONCLUSIONS: There is obvious impairment in multiple cognitive domains in adult-onset NIID, and both the executive dysfunction and memory deficit are very common. Leukoencephalopathy may be the main course of cognitive impairment in adult-onset NIID.

Blood neuro-exosomal synaptic proteins predict Alzheimer's disease at the asymptomatic stage.

INTRODUCTION: Exosomes are an emerging candidate for biomarkers of Alzheimer's disease (AD). This study investigated whether exosomal synaptic proteins can predict AD at the asymptomatic stage. METHODS: We conducted a two-stage-sectional study (discovery stage: AD, 28; amnestic mild cognitive impairment [aMCI], 25; controls, 29; validation stage: AD, 73; aMCI, 71; controls, 72), a study including preclinical AD (160) and controls (160), and a confirmation study in familial AD (mutation carriers: 59; non-mutation carriers: 62). RESULTS: The concentrations of growth associated protein 43 (GAP43), neurogranin, synaptosome associated protein 25 (SNAP25), and synaptotagmin 1 were lower in AD than in controls (P < .001). Exosomal biomarker levels were correlated with those in cerebrospinal fluid (R2  = 0.54-0.70). The combination of exosomal biomarkers detected AD 5 to 7 years before cognitive impairment (area under the curve = 0.87-0.89). DISCUSSION: This study revealed that exosomal GAP43, neurogranin, SNAP25, and synaptotagmin 1 act as effective biomarkers for prediction of AD 5 to 7 years before cognitive impairment.

PSEN1, PSEN2, and APP mutations in 404 Chinese pedigrees with familial Alzheimer's disease.

INTRODUCTION: The PSENs/APP mutation distribution in Chinese patients with familial Alzheimer's disease (FAD) remains unclear. We aimed to analyze the genetic features of Chinese FAD pedigrees with and without PSENs/APP mutations. METHODS: In total, 1330 patients with Alzheimer's disease (AD) or mild cognitive impairment in 404 pedigrees were enrolled from the Chinese Familial Alzheimer's Disease Network. PSENs/APP mutations and APOE frequencies were determined. RESULTS: In total, 13.12% of pedigrees carried PSENs/APP missense mutations, 3.71% carried PSENs/APP synonymous/untranslated region variants, and 83.17% did not carry PSENs/APP mutations. Eleven missense mutations were first identified. In patients without PSENs/APP mutations, 44.31% carried one APOEε4 allele, and 14.85% two APOEε4 alleles. DISCUSSION: The new PSENs/APP mutations indicate heterogeneity in AD pathogenesis between Chinese and other ethnic groups. The low mutation rate suggests the involvement of other genes/factors in Chinese FAD. APOEε4 might be a major gene for some FAD without PSENs/APP mutations.

The APOE ε4 exerts differential effects on familial and other subtypes of Alzheimer's disease.

INTRODUCTION: The genetic risk effects of apolipoprotein E (APOE) on familial Alzheimer's disease (FAD) with or without gene mutations, sporadic AD (SAD), and normal controls (NC) remain unclear in the Chinese population. METHODS: In total, 15 119 subjects, including 311 FAD patients without PSEN1, PSEN2, APP, TREM2, and SORL1 pathogenic mutations (FAD [unknown]); 126 FAD patients with PSENs/APP mutations (FAD [PSENs/APP]); 7234 SAD patients; and 7448 NC were enrolled. The risk effects of APOE ε4 were analyzed across groups. RESULTS: The prevalence of the APOE ε4 genotype in FAD (unknown), FAD (PSENs/APP), SAD, and NC groups was 56.27%, 26.19%, 36.23%, and 19.54%, respectively. Further, the APOE ε4 positive genotype had predictive power for FAD (unknown) risk (odds ratio: 4.51, 95% confidence interval: 3.57-5.45, P < .001). DISCUSSION: APOE ε4 positive genotype may cause familial aggregation, and the investigation of multiple interventions targeting APOE pathological function to reduce the risk for this disease warrants attention.

Heat stress induces distinct responses in porcine cumulus cells and oocytes associated with disrupted gap junction and trans-zonal projection colocalization.

Cumulus cells (CCs), the granulosa cells surrounding the oocytes, play critical roles in oocytes maturation through intercellular communication by extending trans-zonal projections (TZPs) to contact oocytes via gap junctions (GJs). The adverse effect of heat stress (HS) on oocyte maturation has been well documented, whereas the HS responses of CCs and the oocytes in association with GJ/TZP colocalization remain unclear. In this study, porcine cumulus-oocyte complexes (COCs) were subjected to HS at 41.5°C for 24 hr during in vitro maturation. Cumulus expansion was impaired and oocyte quality was reduced with lower survival rate, polar body extrusion rate, and early embryo developmental potentials. CCs and oocytes isolated from COCs demonstrated distinct responses to HS. The messenger RNA abundance of heat shock protein-related genes and mitochondrial DNA-encoded genes, together with ATP content, were significantly increased in CCs, yet decreased in oocytes, despite activation of caspase 3 detected in both CCs and oocytes. Similar changes were observed when denuded oocytes and isolated CCs subjected to HS separately, except mitochondria reactive oxygen species (mROS). In heat-stressed COCs, mROS was significantly increased only in oocytes. However, when isolated CCs and denuded oocytes were heat-stressed separately, mROS was significantly increased only in CCs. Moreover, F-actin, a TZP marker, and its colocalization with a GJ protein connexin-45, were significantly reduced in heat-exposed COCs. These results indicate that HS induces distinct responses in porcine CCs and oocytes in association with disrupted GJ and TZP colocalization.

Two novel presenilin-1 mutations (I249L and P433S) in early onset Chinese Alzheimer's pedigrees and their functional characterization.

Clinical case study and functional characterization of the disease-associated presenilin-1 (PSEN1) mutations may help reveal the roles of PSEN1 in the pathogenesis of Alzheimer's disease (AD). By mutation screening of PSEN1, presenilin-2, and amyloid precursor protein genes in two Chinese Alzheimer's pedigrees, we identified two novel PSEN1 mutations, I249L and P433S. The two probands presented with progressive memory decline and subsequent psychiatric symptoms, with the age of onset at 54 and 34 years old, respectively. The effects of these two mutations on presenilin-1 endoproteolysis and ß-amyloid (Aß) production were examined in SH-SY5Y neuroblastoma cells infected with lentiviruses expressing presenilin-1 wild type (WT), I249L and P433S mutants. Both mutants showed increased Aß42 levels and Aß42/Aß40 ratios. However, the I249L did not affect presenilin-1 endoproteolysis or Aß43 production, whereas the P433S mutant inhibited presenilin-1 endoproteolysis and enhanced Aß43 production. Our findings suggest that both I249L and P433S are pathogenic for early onset of AD by increasing Aß42 production and Aß42/Aß40 ratios. Furthermore, P433S may contribute to the very early onset of AD by inhibiting PS1 endoproteolysis and enhancing the production of longer Aß peptide Aß43.

Homocysteine impairs porcine oocyte quality via deregulation of one-carbon metabolism and hypermethylation of mitochondrial DNA†.

Homocysteine (Hcy) is an intermediate in the one-carbon metabolism that donates methyl groups for methylation processes involved in epigenetic gene regulation. Although poor oocyte quality in polycystic ovarian syndrome (PCOS) patients is associated with elevated Hcy concentration in serum and follicular fluid, whether Hcy directly affects oocyte quality and its mechanisms are poorly understood. Here we show that Hcy treatment impaired oocyte quality and developmental competence, indicated by significantly reduced survival rate, polar body extrusion rate, and cleavage rate. Hcy treatment resulted in mitochondrial dysfunction, with increased production of mitochondrial ROS, reduced mtDNA copy number, and the expression of 7 out of 13 mtDNA-encoded genes and 2 ribosome RNA genes, 12S rRNA and 16S rRNA. Upon Hcy treatment, the expression of one-carbon metabolic enzymes and DNMT1 was enhanced. Interestingly, DNA methyltransferase inhibitor 5'AZA rescued Hcy-induced mitochondrial dysfunction, impaired oocyte quality and developmental competence. Concurrently, expression of one-carbon metabolic enzymes and methylation status of mtDNA coding sequences were also normalized, at least partially, by 5'AZA treatment. Our findings not only extend the understanding about how Hcy induces poor oocyte quality, but also contribute to a novel angle of identifying targets for enhancing the quality of oocyte from PCOS patients.

Exosomes derived from high-glucose-stimulated Schwann cells promote development of diabetic peripheral neuropathy.

Schwann cells actively interact with axons of dorsal root ganglia (DRG) neurons. Exosomes mediate intercellular communication by transferring their biomaterials, including microRNAs (miRs) into recipient cells. We hypothesized that exosomes derived from Schwann cells stimulated by high glucose (HG) exosomes accelerate development of diabetic peripheral neuropathy and that exosomal cargo miRs contribute to this process. We found that HG exosomes contained high levels of miR-28, -31a, and -130a compared to exosomes derived from non-HG-stimulated Schwann cells. In vitro, treatment of distal axons with HG exosomes resulted in reduction of axonal growth, which was associated with elevation of miR-28, -31a, and -130a and reduction of their target proteins of DNA methyltransferase-3α, NUMB (an endocytic adaptor protein), synaptosome associated protein 25, and growth-associated protein-43 in axons. In vivo, administration of HG exosomes to sciatic nerves of diabetic db/db mice at 7 wk of age promoted occurrence of peripheral neuropathy characterized by impairment of nerve conduction velocity and induction of mechanic and thermal hypoesthesia, which was associated with substantial decreases in intraepidermal nerve fibers. Our findings demonstrate a functional role of exosomes derived from HG-stimulated Schwann cells in mediating development of diabetic peripheral neuropathy.-Jia, L., Chopp, M., Wang, L., Lu, X., Szalad, A., Zhang, Z. G. Exosomes derived from high-glucose-stimulated Schwann cells promote development of diabetic peripheral neuropathy.

Altered microbiomes distinguish Alzheimer's disease from amnestic mild cognitive impairment and health in a Chinese cohort.

OBJECTIVE: (Background): Alzheimer's disease (AD), clinically characterized by the progressive neurodegenerative condition and cognitive impairment, is one of the main causes of disability in elder people worldwide. Recently, several animal studies indicated that the 'gut-brain' axis might contribute to the amyloid deposition of AD. However, data about gut dysbiosis in human AD remains scarce in the literature, especially including the whole process of AD. In this prospective and cross-sectional study, we aimed at identifying differences in microbiome between patients with AD (Pre-onset stage amnestic mild cognitive impairment, aMCI; and AD) and the normal cognition healthy controls (HC). Additionally, the potential association between IM and clinical characteristics of AD was evaluated. METHODS: A total of 97 subjects (33 AD, 32 aMCI, and 32 HC) were recruited in the study. The composition of gut bacterial communities was determined by 16S ribosomal RNA Miseq sequencing. In addition, Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) was used to predict function shift of intestinal microbiota. The Mini-Mental State Examination (MMSE), Montreal Cognitive Assessment (MoCA) or Clinical Dementia Rating (CDR) scores were used to evaluate the severity of cognitive impairment in patients. RESULTS: The fecal microbial diversity was decreased in AD patients compared with aMCI patients and HC. And the microbial composition was distinct among aMCI, AD and healthy control groups. Among bacterial taxa, the proportion of phylum Firmicutes was significantly reduced (P = 0.008), whereas Proteobacteria (P = 0.024) was highly enriched in the AD compared with HC. In addition, similar alterations were observed at the order, class and family levels of these two phyla. And Gammaproteobacteria, Enterobacteriales and Enterobacteriaceae showed a progressive enriched prevalence from HC to aMCI and AD patients. Further, a significant correlation was observed between the clinical severity scores of AD patients and the abundance of altered microbiomes. Moreover, the KEGG results showed the increased modules related to glycan biosynthesis and metabolism in AD and aMCI patients and decreased pathways related to immune system in AD patients. Importantly, the discriminating models based on predominant microbiota could effectively distinguish aMCI and AD from HC (AUC = 0.890, 0.940, respectively), and also AD from aMCI (AUC = 0.925). Notably, the models based on the abundance of family Enterobacteriaceae could distinguish AD from both aMCI (AUC = 0.688) and HC (AUC = 0.698). CONCLUSIONS: Distinct microbial communities, especially enriched Enterobacteriaceae, were associated with patients with AD when compared with predementia stage aMCI and healthy subjects. These novel findings will give new clues to understand the disease and provide new therapeutic target for intervention or a marker for this disease.