Swedish Alzheimer's disease variant perturbs activity of retrograde molecular motors and causes widespread derangement of axonal transport pathways.

Experimental studies in flies, mice, and humans suggest a significant role of impaired axonal transport in the pathogenesis of Alzheimer's disease (AD). The mechanisms underlying these impairments in axonal transport, however, remain poorly understood. Here we report that the Swedish familial AD mutation causes a standstill of the amyloid precursor protein (APP) in the axons at the expense of its reduced anterograde transport. The standstill reflects the perturbed directionality of the axonal transport of APP, which spends significantly more time traveling in the retrograde direction. This ineffective movement is accompanied by an enhanced association of dynactin-1 with APP, which suggests that reduced anterograde transport of APP is the result of enhanced activation of the retrograde molecular motor dynein by dynactin-1. The impact of the Swedish mutation on axonal transport is not limited to the APP vesicles since it also reverses the directionality of a subset of early endosomes, which become enlarged and aberrantly accumulate in distal locations. In addition, it also reduces the trafficking of lysosomes due to their less effective retrograde movement. Altogether, our experiments suggest a pivotal involvement of retrograde molecular motors and transport in the mechanisms underlying impaired axonal transport in AD and reveal significantly more widespread derangement of axonal transport pathways in the pathogenesis of AD.

Plectin plays a role in the migration and volume regulation of astrocytes: a potential biomarker of glioblastoma.

BACKGROUND: The expression of aquaporin 4 (AQP4) and intermediate filament (IF) proteins is altered in malignant glioblastoma (GBM), yet the expression of the major IF-based cytolinker, plectin (PLEC), and its contribution to GBM migration and invasiveness, are unknown. Here, we assessed the contribution of plectin in affecting the distribution of plasmalemmal AQP4 aggregates, migratory properties, and regulation of cell volume in astrocytes. METHODS: In human GBM, the expression of glial fibrillary acidic protein (GFAP), AQP4 and PLEC transcripts was analyzed using publicly available datasets, and the colocalization of PLEC with AQP4 and with GFAP was determined by immunohistochemistry. We performed experiments on wild-type and plectin-deficient primary and immortalized mouse astrocytes, human astrocytes and permanent cell lines (U-251 MG and T98G) derived from a human malignant GBM. The expression of plectin isoforms in mouse astrocytes was assessed by quantitative real-time PCR. Transfection, immunolabeling and confocal microscopy were used to assess plectin-induced alterations in the distribution of the cytoskeleton, the influence of plectin and its isoforms on the abundance and size of plasmalemmal AQP4 aggregates, and the presence of plectin at the plasma membrane. The release of plectin from cells was measured by ELISA. The migration and dynamics of cell volume regulation of immortalized astrocytes were assessed by the wound-healing assay and calcein labeling, respectively. RESULTS: A positive correlation was found between plectin and AQP4 at the level of gene expression and protein localization in tumorous brain samples. Deficiency of plectin led to a decrease in the abundance and size of plasmalemmal AQP4 aggregates and altered distribution and bundling of the cytoskeleton. Astrocytes predominantly expressed P1c, P1e, and P1g plectin isoforms. The predominant plectin isoform associated with plasmalemmal AQP4 aggregates was P1c, which also affected the mobility of astrocytes most prominently. In the absence of plectin, the collective migration of astrocytes was impaired and the dynamics of cytoplasmic volume changes in peripheral cell regions decreased. Plectin's abundance on the plasma membrane surface and its release from cells were increased in the GBM cell lines. CONCLUSIONS: Plectin affects cellular properties that contribute to the pathology of GBM. The observed increase in both cell surface and released plectin levels represents a potential biomarker and therapeutic target in the diagnostics and treatment of GBMs.

Association of Bipolar Disorder With Major Adverse Cardiovascular Events: A Population-Based Historical Cohort Study.

OBJECTIVE: This study aimed to assess the association of bipolar disorder (BD) with risk of major adverse cardiac events (MACEs) after adjusting for established cardiovascular disease (CVD) risk factors. METHODS: We conducted a population-based historical cohort study using the Rochester Epidemiology Project. Patients older than 30 years with a clinical encounter from 1998 to 2000 with no prior MACE, atrial fibrillation, or heart failure were followed up through March 1, 2016. BD diagnosis was validated by chart review. Cox proportional hazards regression models were adjusted for established CVD risk factors, alcohol use disorder, other substance use disorders (SUDs), and major depressive disorder (MDD). RESULTS: The cohort included 288 individuals with BD (0.81%) and 35,326 individuals without BD as the reference group (Ref). Median (interquartile range) follow-up was 16.5 (14.6-17.5) years. A total of 5636 MACE events occurred (BD, 59; Ref, 5577). Survival analysis showed an association between BD and MACE (median event-free-survival rates: BD, 0.80; Ref, 0.86; log-rank p = .018). Multivariate regression adjusting for age and sex also yielded an association between BD and MACE (hazard ratio [HR] = 1.93; 95% confidence interval [CI] = 1.43-2.52; p < .001). The association remained significant after further adjusting for smoking, diabetes mellitus, hypertension, high-density lipoprotein cholesterol, and body mass index (HR = 1.66; 95% CI = 1.17-2.28; p = .006), and for alcohol use disorder, SUD, and MDD (HR = 1.56; 95% CI = 1.09-2.14; p = .010). CONCLUSIONS: In this study, BD was associated with an increased risk of MACE, which persisted after adjusting for established CVD risk factors, SUDs, and MDD. These results suggest that BD is an independent risk factor for major clinical cardiac disease outcomes.

The Prevalence of Dysglycemia-Based Chronic Disease in a European Population - a New Paradigm to Address Diabetes Burden: A Kardiovize Study.

OBJECTIVE: To determine the prevalence rate and associated risk factors for each stage of the Dysglycemia-Based Chronic Disease (DBCD) model, which 4 distinct stages and prompts early prevention to avert Diabetes and cardiometabolic complications. METHODS: Subjects between 25 and 64 years old from a random population-based sample were evaluated in Czechia from 2013 to 2014 using a cross-sectional design. DBCD stages were: stage 1 "insulin resistance" (inferred risk from abdominal obesity or a family history of diabetes); stage 2 "prediabetes"(fasting glucose between 5.6 and 6.9 mmol/L); stage 3 "type 2 diabetes (T2D)" (self-report of T2D or fasting glucose ≥7 mmol/L); and stage 4 "vascular complications" (T2D with cardiovascular disease). RESULTS: A total of 2147 subjects were included (57.8% women) with a median age of 48 years. The prevalence of each DBCD stage were as follows: 54.2% (stage 1); 10.3% (stage 2), 3.7% (stage 3); and 1.2% (stage 4). Stages 2 to 4 were more frequent in men and stage 1 in women (P < .001). Using binary logistic regression analysis adjusting by age/sex, all DBCD stages were strongly associated with abnormal adiposity, hypertension, dyslipidemia, and smoking status. Subjects with lower educational levels and lower income were more likely to present DBCD. CONCLUSION: Using the new DBCD framework and available metrics, 69.4% of the population had DBCD, identifying far more people at risk than a simple prevalence rate for T2D (9.2% in Czechia, 2013-2014). All stages were associated with traditional cardiometabolic risk factors, implicating common pathophysiologic mechanisms and a potential for early preventive care. The social determinants of health were related with all DBCD stages in alarming proportions and will need to be further studied.

Associations between high triglycerides and arterial stiffness in a population-based sample: Kardiovize Brno 2030 study.

BACKGROUND: The term arterial stiffness (ArSt) describes structural changes in arterial wall related to the loss of elasticity and is known as an independent predictor of cardiovascular diseases (CVD). The evidence relating to ArSt and triglycerides (TG) shows contradictory results. This paper means to survey the association between high TG and ArSt, utilizing the cardio-ankle vascular index (CAVI). METHODS: Subjects aged between 25 and 64 years from a random population-based sample were evaluated between 2013 and 2016. Data from questionnaires, blood pressure, anthropometric measures, and blood samples were collected and analyzed. CAVI was measured using VaSera VS-1500 N devise. Subjects with a history of CVD or chronic renal disease were excluded. RESULTS: One thousand nine hundred thirty-four participants, 44.7% of males, were included. The median age was 48 (Interquartile Range [IQR] 19) years, TG levels were 1.05 (0.793) mmol/L, and CAVI 7.24 (1.43) points. Prevalence of high CAVI was 10.0% (14.5% in males and 6.4% in females; P <  0.001) and prevalence of hypertriglyceridemia was 20.2% (29.2% in males and 13% in females, P <  0.001). The correlation between TG and CAVI was 0.136 (P <  0.001). High CAVI values were more prevalent among participants with metabolic syndrome (MetS), high blood pressure, dysglycemia, abdominal obesity, high LDL-cholesterol (LDL-c), and high total cholesterol. Using binary regression analysis, high TG were associated with high CAVI, even after adjustment for other MetS components, age, gender, smoking status, LDL-c, and statin treatment (ß = 0.474, OR = 1.607, 95% CI = 1.063-2.429, P = 0.024). CONCLUSION: TG levels were correlated with ArSt, measured as CAVI. High TG was associated with high CAVI independent of multiple cardiometabolic risk factors. Awareness of the risks and targeted treatment of hypertriglyceridemia could further benefit in reducing the prevalence of CVD and events.

Cortical ß-amyloid burden, neuropsychiatric symptoms, and cognitive status: the Mayo Clinic Study of Aging.

Neuropsychiatric symptoms (NPS) are a risk factor for cognitive impairment and are associated with cortical ß-amyloid (Aß) deposition. We conducted a cross-sectional study derived from the ongoing population-based Mayo Clinic Study of Aging to examine the frequency of NPS among cognitively unimpaired (CU) and mild cognitive impairment (MCI) participants who either have normal (A-) or abnormal (A+) Aß deposition. We also investigated whether combined presence of MCI and amyloid positivity (MCI/A+) is associated with greater odds of having NPS as compared to CU/A- (defined as reference group). Participants were 1627 CU and MCI individuals aged ≥ 50 years (54% males; median age 73 years). All participants underwent NPS assessment (Neuropsychiatric Inventory Questionnaire (NPI-Q); Beck Depression Inventory II (BDI-II); Beck Anxiety Inventory (BAI)) and 11C-PiB-PET. Participants with an SUVR > 1.42 were classified as A+. We conducted multivariable logistic regression analyses adjusted for age, sex, education, and APOE ε4 genotype status. The sample included 997 CU/A-, 446 CU/A+, 78 MCI/A-, and 106 MCI/A+ persons. For most NPS, the highest frequency of NPS was found in MCI/A+ and the lowest in CU/A-. The odds ratios of having NPS, depression (BDI ≥ 13), or anxiety (BAI ≥ 8, ≥ 10) were consistently highest for MCI/A+ participants. In conclusion, MCI with Aß burden of the brain is associated with an increased risk of having NPS as compared to MCI without Aß burden. This implies that the underlying Alzheimer's disease biology (i.e., cerebral Aß amyloidosis) may drive both cognitive and psychiatric symptoms.

Examination of potential mechanisms of amyloid-induced defects in neuronal transport.

Microtubule-based neuronal transport pathways are impaired during the progression of Alzheimer's disease and other neurodegenerative conditions. However, mechanisms leading to defects in transport remain to be determined. We quantified morphological changes in neuronal cells following treatment with fibrils and unaggregated peptides of beta-amyloid (Abeta). Abeta fibrils induce axonal and dendritic swellings indicative of impaired transport. In contrast, Abeta peptides induce a necrotic phenotype in both neurons and non-neuronal cells. We tested several popular hypotheses by which aggregated Abeta could disrupt transport. Using fluorescent polystyrene beads, we developed experimental models of physical blockage and localized release of reactive oxygen species (ROS) that reliably induce swellings. Like the beads, Abeta fibrils localize in close proximity to swellings; however, fibril internalization is not required for disrupting transport. ROS and membrane permeability are also unlikely to be responsible for fibril-mediated toxicity. Collectively, our results indicate that multiple initiating factors converge upon pathways of defective transport.

Axonal transport and Alzheimer's disease.

In contrast to most eukaryotic cells, neurons possess long, highly branched processes called axons and dendrites. In large mammals, such as humans, some axons reach lengths of over 1 m. These lengths pose a major challenge to the movement of proteins, vesicles, and organelles between presynaptic sites and cell bodies. To overcome this challenge axons and dendrites rely upon specialized transport machinery consisting of cytoskeletal motor proteins generating directed movements along cytoskeletal tracks. Not only are these transport systems crucial to maintain neuronal viability and differentiation, but considerable experimental evidence suggests that failure of axonal transport may play a role in the development or progression of neurological diseases such as Alzheimer's disease.