Perivascular phosphorylated TDP-43 inclusions are associated with Alzheimer's disease pathology and loss of CD146 and Aquaporin-4.

The majority of patients with Alzheimer's disease (AD) exhibit aggregates of Trans-active response DNA binding protein 43 (TDP-43) in their hippocampus, which is associated with a more aggressive disease progression. The TDP-43 inclusions are commonly found in neurons, but also in astrocytes. The impact of the inclusions in astrocytes is less known. In the current study, we investigate the presence of phosphorylated TDP-43 (pTDP-43) inclusions in astrocytic endfeet and their potential association with blood-brain barrier (BBB) damage, glymphatic system dysfunction, and AD pathology. By staining postmortem hippocampal sections from AD patients and non-demented controls against TDP-43 and pTDP-43 together with the astrocytic markers glial fibrillary acidic protein (GFAP), astrocytic endfeet marker Aquaporin-4 (AQP4), and markers for BBB alterations (CD146) and leakiness (Immunoglobulin A), we demonstrate a close association between perivascular pTDP-43 or TDP-43 inclusions and GFAP or AQP4. These perivascular inclusions were more prominent in AD and correlated with the disease severity and loss of CD146 and AQP4. The findings indicate a relationship between pTDP-43 accumulation in astrocytic endfeet and BBB and glymphatic system dysfunction, which may contribute to the downstream pathological events seen in AD patients and the aggressive disease progression.

Okinawa-Based Nordic Diet Decreases Plasma Glial Fibrillary Acidic Protein Levels in Type 2 Diabetes Patients.

Elevated levels of glial fibrillary acidic protein (GFAP) in plasma reflect neuroinflammation and are linked to cognitive decline. Preclinical studies show that dietary change can attenuate astrocyte reactivity and neuroinflammation. In the current study, we investigate if the Okinawa-based Nordic (O-BN) diet alters plasma GFAP levels in patients with Type 2 Diabetes (T2D), a metabolic disorder associated with cognitive disturbances and an increased risk of dementia. Plasma GFAP levels were measured in T2D patients (n = 30) at baseline, after 3 months of the diet, and after a subsequent 4 months of unrestricted diets. The GFAP levels decreased significantly after 3 months of the diet (p = 0.048) but reverted to baseline levels after 4 months of unrestricted diets. At baseline, the GFAP levels correlated significantly with levels of the neurodegeneration marker neurofilament light polypeptide (r = 0.400*) and, after correcting for age, sex, and body mass index, with proinflammatory plasma cytokines (ranging from r = 0.440* to r = 0.530**) and the metabolic hormone islet amyloid polypeptide (r = 0.478*). We found no correlation with psychological well-being. These results suggest that the O-BN diet reduces neuroinflammation in T2D patients and may thus be an important preventive measure for managing T2D and reducing the risk of neurodegenerative disorders.

Proteomic changes in Alzheimer's disease associated with progressive Aß plaque and tau tangle pathologies.

Proteomics can shed light on the dynamic and multifaceted alterations in neurodegenerative disorders like Alzheimer's disease (AD). Combining radioligands measuring ß-amyloid (Aß) plaques and tau tangles with cerebrospinal fluid proteomics, we uncover molecular events mirroring different stages of AD pathology in living humans. We found 127 differentially abundant proteins (DAPs) across the AD spectrum. The strongest Aß-related proteins were mainly expressed in glial cells and included SMOC1 and ITGAM. A dozen proteins linked to ATP metabolism and preferentially expressed in neurons were independently associated with tau tangle load and tau accumulation. Only 20% of the DAPs were also altered in other neurodegenerative diseases, underscoring AD's distinct proteome. Two co-expression modules related, respectively, to protein metabolism and microglial immune response encompassed most DAPs, with opposing, staggered trajectories along the AD continuum. We unveil protein signatures associated with Aß and tau proteinopathy in vivo, offering insights into complex neural responses and potential biomarkers and therapeutics targeting different disease stages.

Okinawa-Based Nordic Diet Decreases Plasma Levels of IAPP and IgA against IAPP Oligomers in Type 2 Diabetes Patients.

Pancreas-derived islet amyloid polypeptide (IAPP) aggregates and deposits in the pancreas and periphery of Type 2 Diabetes (T2D) patients, contributing to diabetic complications. The excess IAPP can be removed by autoantibodies, and increased levels of immunoglobulin (Ig) G against IAPP have been reported in T2D patients. However, whether other Ig classes are also affected and if the levels can be managed is less known. This pre-post study examines IgA levels against IAPP oligomers (IAPPO-IgA) in T2D patients and assesses the impact of the Okinawa-based Nordic (O-BN) diet-a low-carbohydrate, high-fiber diet-on these levels after following the diet for 3 months. IAPP, IAPPO-IgA, and total IgA levels were measured in plasma and fecal samples from n = 30 T2D patients collected at baseline, after 3 months of diet, and after additional 4 months of unrestricted diets (a clinical follow-up). The IAPP and IAPPO-IgA levels were significantly lower after 3 months, with the latter also being significantly reduced at the clinical follow-up. The reduction in plasma IAPP and IAPPO-IgA levels correlated with reductions in plasma levels of metabolic and inflammatory markers. Hence, following the O-BN diet for at least 3 months is sufficient to reduce circulating IAPP and IAPPO-IgA levels, which may be principal in managing T2D.

The Relationship between p-tau217, p-tau231, and p-tau205 in the Human Brain Is Affected by the Cellular Environment and Alzheimer's Disease Pathology.

The levels of p-tau217 and p-tau231 in cerebrospinal fluid (CSF) are associated with early amyloid beta (Aß) changes in the brain, while the CSF levels of p-tau205 are foremost related to tau pathology in the later stages of the disease. To investigate if the three p-tau variants are found to the same degree in different tau structures and if their co-localization is affected by the diagnosis and presence of Aß plaques, we immunostained sections of the entorhinal cortex (EC) and inferior temporal gyrus (ITG) from non-demented controls (NC), patients with Alzheimer's disease (AD), and primary age-related tauopathy (PART) against p-tau217, p-tau231, and p-tau205 together with Methoxi-X04. An analysis using confocal microscopy showed that the co-localization variable, the Pearson correlation coefficient (PCC), was significantly higher between p-tau231 and p-tau205 in neurofibrillary tangles compared to neuropil threads and dystrophic neurites in plaques. The PCC value between all three p-tau variants in the neuropil threads was significantly lower in the ECs of patients with AD compared to the NC and in the ITGs of patients with AD, with a high Aß load compared to PART. The lowered value was associated with proportionally higher amounts of non-colocalized p-tau231 and p-tau217 compared to p-tau205, and the PCC values were negatively correlated with Aß and the tangle loads in patients with AD, but positively correlated with tangles in PART. These results suggest that the proportion of and co-localization between p-tau217, p-tau231, and p-tau205 are dependent on cellular localization and are altered in response to AD pathology in a spatial-temporal manner.

The fluorescent ligand bTVBT2 reveals increased p-tau uptake by retinal microglia in Alzheimer's disease patients and AppNL-F/NL-F mice.

BACKGROUND: Amyloid beta (Aß) deposits and hyperphosphorylated tau (p-tau) accumulation have been identified in the retina of Alzheimer's disease (AD) patients and transgenic AD mice. Previous studies have shown that retinal microglia engulf Aß, but this property decreases in AD patients. Whether retinal microglia also take up p-tau and if this event is affected in AD is yet not described. In the current study, we use the p-tau-specific thiophene-based ligand bTVBT2 to investigate the relationship between disease progression and p-tau uptake by microglia in the retina of AD patients and AppNL-F/NL-F knock-in mice, an AD mouse model known to demonstrate extracellular Aß plaques and dystrophic neurites in the brain from 6 months of age. METHODS: Evaluation of bTVBT2 specificity and its presence within microglia was assessed by immunofluorescent staining of hippocampal sections and flat-mount retina samples from non-demented controls, AD patients, 3-, 9-, and 12-month-old AppNL-F/NL-F knock-in mice and 12- and 18-month-old wild type (WT) mice. We used ImageJ to analyze the amount of bTVBT2 inside Iba1-positive microglia. Co-localization between the ligand and p-tau variant Ser396/Ser404 (PHF-1), Aß, phosphorylated TAR DNA binding protein 43 (pTDP-43), and islet amyloid polypeptide (IAPP) in the brain and retina was analyzed using confocal imaging. RESULTS: Confocal imaging analysis showed that bTVBT2 binds to PHF-1- and AT8-positive aggregates inside retinal microglia, and not to Aß, pTDP-43, or IAPP. The density of bTVBT2-positive microglia was higher in cases with a high Aß load compared to those with a low Aß load. This density correlated with the neurofibrillary tangle load in the brain, but not with retinal levels of high molecular weight (aggregated) Aß40 or Aß42. Analysis of AppNL-F/NL-F knock-in mouse retina further showed that 50% of microglia in 3-month-old AppNL-F/NL-F knock-in mice contained bTVBT2. The percentage significantly increased in 9- and 12-month-old mice. CONCLUSION: Our study suggests that the microglial capability to uptake p-tau in the retina persists and intensifies with AD progression. These results also highlight bTVBT2 as a ligand of interest in future monitoring of retinal AD pathology.

Plasma IAPP-Autoantibody Levels in Alzheimer's Disease Patients Are Affected by APOE4 Status.

Pancreas-derived islet amyloid polypeptide (IAPP) crosses the blood-brain barrier and co-deposits with amyloid beta (Aß) in brains of type 2 diabetes (T2D) and Alzheimer's disease (AD) patients. Depositions might be related to the circulating IAPP levels, but it warrants further investigation. Autoantibodies recognizing toxic IAPP oligomers (IAPPO) but not monomers (IAPPM) or fibrils have been found in T2D, but studies on AD are lacking. In this study, we have analyzed plasma from two cohorts and found that levels of neither immunoglobulin (Ig) M, nor IgG or IgA against IAPPM or IAPPO were altered in AD patients compared with controls. However, our results show significantly lower IAPPO-IgA levels in apolipoprotein E (APOE) 4 carriers compared with non-carriers in an allele dose-dependent manner, and the decrease is linked to the AD pathology. Furthermore, plasma IAPP-Ig levels, especially IAPP-IgA, correlated with cognitive decline, C-reactive protein, cerebrospinal fluid Aß and tau, neurofibrillary tangles, and brain IAPP exclusively in APOE4 non-carriers. We speculate that the reduction in IAPPO-IgA levels may be caused by increased plasma IAPPO levels or masked epitopes in APOE4 carriers and propose that IgA and APOE4 status play a specific role in clearance of circulatory IAPPO, which may influence the amount of IAPP deposition in the AD brain.

Contraction of human brain vascular pericytes in response to islet amyloid polypeptide is reversed by pramlintide.

The islet amyloid polypeptide (IAPP), a pancreas-produced peptide, has beneficial functions in its monomeric form. However, IAPP aggregates, related to type 2 diabetes mellitus (T2DM), are toxic not only for the pancreas, but also for the brain. In the latter, IAPP is often found in vessels, where it is highly toxic for pericytes, mural cells that have contractile properties and regulate capillary blood flow. In the current study, we use a microvasculature model, where human brain vascular pericytes (HBVP) are co-cultured together with human cerebral microvascular endothelial cells, to demonstrate that IAPP oligomers (oIAPP) alter the morphology and contractility of HBVP. Contraction and relaxation of HBVP was verified using the vasoconstrictor sphingosine-1-phosphate (S1P) and vasodilator Y27632, where the former increased, and the latter decreased, the number of HBVP with round morphology. Increased number of round HBVP was also seen after oIAPP stimulation, and the effect was reverted by the IAPP analogue pramlintide, Y27632, and the myosin inhibitor blebbistatin. Inhibition of the IAPP receptor with the antagonist AC187 only reverted IAPP effects partially. Finally, we demonstrate by immunostaining of human brain tissue against laminin that individuals with high amount of brain IAPP levels show significantly lower capillary diameter and altered mural cell morphology compared to individuals with low brain IAPP levels. These results indicate that HBVP, in an in vitro model of microvasculature, respond morphologically to vasoconstrictors, dilators, and myosin inhibitors. They also suggest that oIAPP induces contraction of these mural cells and that pramlintide can reverse such contraction.

Increased plasma and brain immunoglobulin A in Alzheimer's disease is lost in apolipoprotein E ε4 carriers.

BACKGROUND: Alzheimer's disease (AD) is foremost characterized by ß-amyloid (Aß)-extracellular plaques, tau-intraneuronal fibrillary tangles (NFT), and neuroinflammation, but over the last years it has become evident that peripheral inflammation might also contribute to the disease. AD patients often demonstrate increased levels of circulating proinflammatory mediators and altered antibody levels in the blood. In our study, we investigated the plasma Immunoglobulin A (IgA) levels in association with apolipoprotein E (APOE) ε4 status and Aß pathology. METHODS: IgA levels in antemortem-collected (cohort I) and postmortem-collected (cohort II) plasma samples from AD patients (n = 30 in cohort I and n = 16 in cohort II) and non-demented age-matched controls (NC) (n = 42 in cohort I and n = 7 in cohort II) were measured using ELISA. Hippocampal sections from cohort II were immunostained against IgA, and the IgA area fraction as well as the number of IgA positive (IgA+) cells in the cornu ammonis region were analysed using ImageJ. The relationship between plasma IgA levels and cognition, C-reactive protein (CRP), and cerebrospinal fluid (CSF) AD biomarkers in cohort I as well as neuropathology, IgA+ cell number, and IgA area fraction in cohort II was analysed before and after grouping the cohorts into APOEε4 carriers and APOEε4 non-carriers. RESULTS: Plasma IgA levels were higher in AD patients compared to NC in both cohorts. Also, AD patients demonstrated higher IgA area fraction and IgA+ cell number compared to NC. When APOEε4 status was considered, higher plasma IgA levels in AD patients were only seen in APOEε4 non-carriers. Finally, plasma IgA levels, exclusively in APOEε4 non-carriers, were associated with cognition, CRP, and CSF Aß levels in cohort I as well as with IgA area fraction, IgA+ cell number, and Aß, Lewy body, and NFT neuropathology in cohort II. CONCLUSIONS: Our study suggests that AD pathology and cognitive decline are associated with increased plasma IgA levels in an APOE allele-dependent manner, where the associations are lost in APOEε4 carriers.

Galectin-3 is elevated in CSF and is associated with Aß deposits and tau aggregates in brain tissue in Alzheimer's disease.

Galectin-3 (Gal-3) is a beta-galactosidase binding protein involved in microglial activation in the central nervous system (CNS). We previously demonstrated the crucial deleterious role of Gal-3 in microglial activation in Alzheimer's disease (AD). Under AD conditions, Gal-3 is primarily expressed by microglial cells clustered around Aß plaques in both human and mouse brain, and knocking out Gal-3 reduces AD pathology in AD-model mice. To further unravel the importance of Gal-3-associated inflammation in AD, we aimed to investigate the Gal-3 inflammatory response in the AD continuum. First, we measured Gal-3 levels in neocortical and hippocampal tissue from early-onset AD patients, including genetic and sporadic cases. We found that Gal-3 levels were significantly higher in both cortex and hippocampus in AD subjects. Immunohistochemistry revealed that Gal-3+ microglial cells were associated with amyloid plaques of a larger size and more irregular shape and with neurons containing tau-inclusions. We then analyzed the levels of Gal-3 in cerebrospinal fluid (CSF) from AD patients (n = 119) compared to control individuals (n = 36). CSF Gal-3 levels were elevated in AD patients compared to controls and more strongly correlated with tau (p-Tau181 and t-tau) and synaptic markers (GAP-43 and neurogranin) than with amyloid-ß. Lastly, principal component analysis (PCA) of AD biomarkers revealed that CSF Gal-3 clustered and associated with other CSF neuroinflammatory markers, including sTREM-2, GFAP, and YKL-40. This neuroinflammatory component was more highly expressed in the CSF from amyloid-ß positive (A+), CSF p-Tau181 positive (T+), and biomarker neurodegeneration positive/negative (N+/-) (A + T + N+/-) groups compared to the A + T-N- group. Overall, Gal-3 stands out as a key pathological biomarker of AD pathology that is measurable in CSF and, therefore, a potential target for disease-modifying therapies involving the neuroinflammatory response.

Cellular localization of p-tau217 in brain and its association with p-tau217 plasma levels.

Recent studies highlight phosphorylated tau (p-tau) at threonine tau 217 (p-tau217) as a new promising plasma biomarker for pathological changes implicated in Alzheimer's disease (AD), but the specific brain pathological events related to the alteration in p-tau217 plasma levels are still largely unknown. Using immunostaining techniques of postmortem AD brain tissue, we show that p-tau217 is found in neurofibrillary tangles (NFTs) and neuropil threads that are also positive for p-tau181, 202, 202/205, 231, and 369/404. The p-tau217, but not the other five p-tau variants, was also prominently seen in vesicles structure positive for markers of granulovacuolar degeneration bodies and multi-vesicular bodies. Further, individuals with a high likelihood of AD showed significantly higher p-tau217 area fraction in 4 different brain areas (entorhinal cortex, inferior temporal gyrus, and superior frontal gyrus) compared to those with Primary age related tauopathy or other non-AD tauopathies. The p-tau217 area fraction correlated strongly with total amyloid-beta (Aß) and NFT brain load when the whole group was analyzed. Finally, the mean p-tau217 area fraction correlated significantly with p-tau217 concentrations in antemortem collected plasma specifically in individuals with amyloid plaques and not in those without amyloid plaques. These studies highlight differences in cellular localization of different p-tau variants and suggest that plasma levels of p-tau217 reflect an accumulation of p-tau217 in presence of Aß plaque load.

Neuronal α-amylase is important for neuronal activity and glycogenolysis and reduces in presence of amyloid beta pathology.

Recent studies indicate a crucial role for neuronal glycogen storage and degradation in memory formation. We have previously identified alpha-amylase (α-amylase), a glycogen degradation enzyme, located within synaptic-like structures in CA1 pyramidal neurons and shown that individuals with a high copy number variation of α-amylase perform better on the episodic memory test. We reported that neuronal α-amylase was absent in patients with Alzheimer's disease (AD) and that this loss corresponded to increased AD pathology. In the current study, we verified these findings in a larger patient cohort and determined a similar reduction in α-amylase immunoreactivity in the molecular layer of hippocampus in AD patients. Next, we demonstrated reduced α-amylase concentrations in oligomer amyloid beta 42 (Aß42 ) stimulated SH-SY5Y cells and neurons derived from human-induced pluripotent stem cells (hiPSC) with PSEN1 mutation. Reduction of α-amylase production and activity, induced by siRNA and α-amylase inhibitor Tendamistat, respectively, was further shown to enhance glycogen load in SH-SY5Y cells. Both oligomer Aß42  stimulated SH-SY5Y cells and hiPSC neurons with PSEN1 mutation showed, however, reduced load of glycogen. Finally, we demonstrate the presence of α-amylase within synapses of isolated primary neurons and show that inhibition of α-amylase activity with Tendamistat alters neuronal activity measured by calcium imaging. In view of these findings, we hypothesize that α-amylase has a glycogen degrading function within synapses, potentially important in memory formation. Hence, a loss of α-amylase, which can be induced by Aß pathology, may in part underlie the disrupted memory formation seen in AD patients.

Early life adversity targets the transcriptional signature of hippocampal NG2+ glia and affects voltage gated sodium (Nav) channels properties.

The precise mechanisms underlying the detrimental effects of early life adversity (ELA) on adult mental health remain still elusive. To date, most studies have exclusively targeted neuronal populations and not considered neuron-glia crosstalk as a crucially important element for the integrity of stress-related brain function. Here, we have investigated the impact of ELA, in the form of a limited bedding and nesting material (LBN) paradigm, on a glial subpopulation with unique properties in brain homeostasis, the NG2+ cells. First, we have established a link between maternal behavior, activation of the offspring's stress response and heterogeneity in the outcome to LBN manipulation. We further showed that LBN targets the hippocampal NG2+ transcriptome with glucocorticoids being an important mediator of the LBN-induced molecular changes. LBN altered the NG2+ transcriptome and these transcriptional effects were correlated with glucocorticoids levels. The functional relevance of one LBN-induced candidate gene, Scn7a, could be confirmed by an increase in the density of voltage-gated sodium (Nav) channel activated currents in hippocampal NG2+ cells. Scn7a remained upregulated until adulthood in LBN animals, which displayed impaired cognitive performance. Considering that Nav channels are important for NG2+ cell-to-neuron communication, our findings provide novel insights into the disruption of this process in LBN mice.

NG2/CSPG4, CD146/MCAM and VAP1/AOC3 are regulated by myocardin-related transcription factors in smooth muscle cells.

The present work addressed the hypothesis that NG2/CSPG4, CD146/MCAM, and VAP1/AOC3 are target genes of myocardin-related transcription factors (MRTFs: myocardin/MYOCD, MRTF-A/MKL1, MRTF-B/MKL2) and serum response factor (SRF). Using a bioinformatics approach, we found that CSPG4, MCAM, and AOC3 correlate with MYOCD, MRTF-A/MKL1, and SRF across human tissues. No other transcription factor correlated as strongly with these transcripts as SRF. Overexpression of MRTFs increased both mRNA and protein levels of CSPG4, MCAM, and AOC3 in cultured human smooth muscle cells (SMCs). Imaging confirmed increased staining for CSPG4, MCAM, and AOC3 in MRTF-A/MKL1-transduced cells. MRTFs exert their effects through SRF, and the MCAM and AOC3 gene loci contained binding sites for SRF. SRF silencing reduced the transcript levels of these genes, and time-courses of induction paralleled the direct target ACTA2. MRTF-A/MKL1 increased the activity of promoter reporters for MCAM and AOC3, and transcriptional activation further depended on the chromatin remodeling enzyme KDM3A. CSPG4, MCAM, and AOC3 responded to the MRTF-SRF inhibitor CCG-1423, to actin dynamics, and to ternary complex factors. Coincidental detection of these proteins should reflect MRTF-SRF activity, and beyond SMCs, we observed co-expression of CD146/MCAM, NG2/CSPG4, and VAP1/AOC3 in pericytes and endothelial cells in the human brain. This work identifies highly responsive vascular target genes of MRTF-SRF signaling that are regulated via a mechanism involving KDM3A.

Hippocampal NG2+ pericytes in chronically stressed rats and depressed patients: a quantitative study.

OBJECTIVE: The suggested link between major depression disorder (MDD) and blood-brain barrier (BBB) alterations supports an impact on the neurovascular unit in this disease condition. Here we investigate how pericytes, a major component in the neurovascular unit, respond to stress, stress hormones, proinflammatory cytokine and depression. METHOD: Hippocampal sections of chronic unpredictable stressed (CMS) rats, MDD patients and respective controls were immuno-stained against NG2, where the number of NG2+ pericytes in the molecular layer was counted. Proliferation of cultured pericytes after treatment with cortisol and IL-1ß was analyzed using radioactive-labeled thymidine. FINDINGS: The number of NG2+ pericytes was significantly higher in CMS animals than controls. Higher number of NG2+ pericytes was also detected in MDD patients, but the increase did not reach significance. IL-1ß, but not cortisol, induced a significant increase in proliferation of cultured pericytes. CONCLUSION: Our results indicate that exposure to stressful conditions affects the hippocampal pericyte population. These findings add to our knowledge about the impact of stress on the neurovascular unit, which might be relevant for understanding the alterations in BBB found in MDD patients.

Alpha-amylase 1A copy number variants and the association with memory performance and Alzheimer's dementia.

BACKGROUND: Previous studies have shown that copy number variation (CNV) in the alpha (α)-amylase gene (AMY1A) is associated with body mass index, insulin resistance, and blood glucose levels, factors also shown to increase the risk of Alzheimer's dementia (AD). We have previously demonstrated the presence of α-amylase in healthy neuronal dendritic spines and a reduction of the same in AD patients. In the current study, we investigate the relationship between AMY1A copy number and AD, memory performance, and brain α-amylase activity. METHODS AND MATERIALS: The association between AMY1A copy number and development of AD was analyzed in 5422 individuals (mean age at baseline 57.5 ± 5.9, females 58.2%) from the Malmö diet and cancer study genotyped for AMY1A copy number, whereof 247 where diagnosed with AD during a mean follow-up of 20 years. Associations between AMY1A copy number and cognitive performance where analyzed in 791 individuals (mean age at baseline 54.7 ± 6.3, females 63%), who performed Montreal Cognitive Assessment (MoCA) test. Correlation analysis between α-amylase activity or α-amylase gene expression and AMY1A copy number in post-mortem hippocampal tissue from on demented controls (n = 8) and AD patients (n = 10) was also performed. RESULTS: Individuals with very high ( ≥10) AMY1A copy number had a significantly lower hazard ratio of AD (HR = 0.62, 95% CI 0.41-0.94) and performed significantly better on MoCA delayed word recall test, compared to the reference group with AMY1A copy number 6. A trend to lower hazard ratio of AD was also found among individuals with low AMY1A copy number (1-5) (HR = 0.74, 95% CI 0.53-1.02). A tendency towards a positive correlation between brain α-amylase activity and AMY1A copy number was found, and females showed higher brain α-amylase activity compared to males. CONCLUSION: Our study suggests that the degree of α-amylase activity in the brain is affected by AMY1A copy number and gender, in addition to AD pathology. The study further suggests that very high AMY1A copy number is associated with a decreased hazard ratio of AD and we speculate that this effect is mediated via a beneficial impact of AMY1A copy number on episodic memory performance.

Apolipoprotein E Interferes with IAPP Aggregation and Protects Pericytes from IAPP-Induced Toxicity.

Apolipoprotein E (ApoE) has become a primary focus of research after the discovery of its strong linkage to Alzheimer's disease (AD), where the ApoE4 variant is the highest genetic risk factor for this disease. ApoE is commonly found in amyloid deposits of different origins, and its interaction with amyloid-ß peptide (Aß), the hallmark of AD, is well known. However, studies on the interaction of ApoEs with other amyloid-forming proteins are limited. Islet amyloid polypeptide (IAPP) is an amyloid-forming peptide linked to the development of type-2 diabetes and has also been shown to be involved in AD pathology and vascular dementia. Here we studied the impact of ApoE on IAPP aggregation and IAPP-induced toxicity on blood vessel pericytes. Using both in vitro and cell-based assays, we show that ApoE efficiently inhibits the amyloid formation of IAPP at highly substoichiometric ratios and that it interferes with both nucleation and elongation. We also show that ApoE protects the pericytes against IAPP-induced toxicity, however, the ApoE4 variant displays the weakest protective potential. Taken together, our results suggest that ApoE has a generic amyloid-interfering property and can be protective against amyloid-induced cytotoxicity, but there is a loss of function for the ApoE4 variant.

Levels of Retinal Amyloid-ß Correlate with Levels of Retinal IAPP and Hippocampal Amyloid-ß in Neuropathologically Evaluated Individuals.

BACKGROUND: Previous studies have used immunohistology to demonstrate Alzheimer's disease (AD) characteristic accumulation of amyloid-ß (Aß) in the retina of AD patients, a finding indicating retina examination as a potential diagnostic tool for AD pathology. OBJECTIVE: To further explore this idea by investigating whether levels of Aß42 and Aß40 in retina are associated with corresponding levels in hippocampus, neuropathological assessments, apolipoprotein E (APOE) genotype, and levels of islet amyloid polypeptide (IAPP). METHODS: Levels of high molecular weight (HMW) Aß42, Aß40, and IAPP in ultra-centrifuged homogenates of retina and hippocampus from patients with AD, multiple sclerosis, AD with Lewy bodies, and non-demented controls were analyzed using Mesoscale Discovery electrochemiluminescence technology employing immunoassay and enzyme-linked immunosorbent assay. RESULTS: Higher levels of retinal and hippocampal Aß42-HMW, Aß40-HMW, and IAPP-HMW were found in individuals with high neuropathological scores of Aß plaques and in individuals carrying the APOEɛ4 allele. The retinal levels of Aß42-HMW and Aß40-HMW correlated with corresponding levels in hippocampus as well as with neurofibrillary tangles (NFT) and Aß scores. Retinal IAPP-HMW correlated with retinal levels of Aß42-HMW and with NFT and Aß scores. CONCLUSION: These results show that different isoforms of Aß can be detected in the human retina and moreover support the growing number of studies indicating that AD-related pathological changes occurring in the brain could be reflected in the retina.