Nirmal Verma

Intraneuronal Amylin Deposition, Peroxidative Membrane Injury and Increased IL-1β Synthesis in Brains of Alzheimer’s Disease Patients with Type-2 Diabetes and in Diabetic HIP Rats

Amylin is a hormone synthesized and co-secreted with insulin by pancreatic β-cells that crosses the blood-brain barrier and regulates satiety. Amylin from humans (but not rodents) has an increased propensity to aggregate into pancreatic islet amyloid deposits that contribute to β-cell mass depletion and development of type-2 diabetes by inducing oxidative stress and inflammation. Recent studies demonstrated that aggregated amylin also accumulates in brains of Alzheimers disease (AD) patients, preponderantly those with type-2 diabetes. Here, we report that, in addition to amylin plaques and mixed amylin-Aβ deposits, brains of diabetic patients with AD show amylin immunoreactive deposits inside the neurons. Neuronal amylin formed adducts with 4-hydroxynonenal (4-HNE), a marker of peroxidative membrane injury, and increased synthesis of the proinflammatory cytokine interleukin (IL)-1β. These pathological changes were mirrored in rats expressing human amylin in pancreatic islets (HIP rats) and mice intravenously injected with aggregated human amylin, but not in hyperglycemic rats secreting wild-type non-amyloidogenic rat amylin. In cultured primary hippocampal rat neurons, aggregated amylin increased IL-1β synthesis via membrane destabilization and subsequent generation of 4-HNE. These effects were blocked by membrane stabilizers and lipid peroxidation inhibitors. Thus, elevated circulating levels of aggregated amylin negatively affect the neurons causing peroxidative membrane injury and aberrant inflammatory responses independent of other confounding factors of diabetes. The present results are consistent with the pathological role of aggregated amylin in the pancreas, demonstrate a novel contributing mechanism to neurodegeneration, and suggest a direct, potentially treatable link of type-2 diabetes with AD.

Brain microvascular injury and white matter disease provoked by diabetes-associated hyperamylinemia

The brain blood vessels of patients with type 2 diabetes and dementia have deposition of amylin, an amyloidogenic hormone cosecreted with insulin. It is not known whether vascular amylin deposition is a consequence or a trigger of vascular injury. We tested the hypothesis that the vascular amylin deposits cause endothelial dysfunction and microvascular injury and are modulated by amylin transport in the brain via plasma apolipoproteins.

Hyperamylinemia Increases IL-1β Synthesis in the Heart via Peroxidative Sarcolemmal Injury.

Hypersecretion of amylin is common in individuals with prediabetes, causes amylin deposition and proteotoxicity in pancreatic islets, and contributes to the development of type 2 diabetes. Recent studies also identified amylin deposits in failing hearts from patients with obesity or type 2 diabetes and demonstrated that hyperamylinemia accelerates the development of heart dysfunction in rats expressing human amylin in pancreatic β-cells (HIP rats). To further determine the impact of hyperamylinemia on cardiac myocytes, we investigated human myocardium, compared diabetic HIP rats with diabetic rats expressing endogenous (nonamyloidogenic) rat amylin, studied normal mice injected with aggregated human amylin, and developed in vitro cell models. We found that amylin deposition negatively affects cardiac myocytes by inducing sarcolemmal injury, generating reactive aldehydes, forming amylin-based adducts with reactive aldehydes, and increasing synthesis of the proinflammatory cytokine interleukin-1β (IL-1β) independently of hyperglycemia. These results are consistent with the pathological role of amylin deposition in the pancreas, uncover a novel contributing mechanism to cardiac myocyte injury in type 2 diabetes, and suggest a potentially treatable link of type 2 diabetes with diabetic heart disease. Although further studies are necessary, these data also suggest that IL-1β might function as a sensor of myocyte amylin uptake and a potential mediator of myocyte injury.

The Mitochondrial Peptidase Pitrilysin Degrades Islet Amyloid Polypeptide in Beta-Cells

Amyloid formation and mitochondrial dysfunction are characteristics of type 2 diabetes. The major peptide constituent of the amyloid deposits in type 2 diabetes is islet amyloid polypeptide (IAPP). In this study, we found that pitrilysin, a zinc metallopeptidase of the inverzincin family, degrades monomeric, but not oligomeric, islet amyloid polypeptide in vitro. In insulinoma cells when pitrilysin expression was decreased to 5% of normal levels, there was a 60% increase in islet amyloid polypeptide-induced apoptosis. In contrast, overexpression of pitrilysin protects insulinoma cells from human islet amyloid polypeptide-induced apoptosis. Since pitrilysin is a mitochondrial protein, we used immunofluorescence staining of pancreases from human IAPP transgenic mice and Western blot analysis of IAPP in isolated mitochondria from insulinoma cells to provide evidence for a putative intramitochondrial pool of IAPP. These results suggest that pitrilysin regulates islet amyloid polypeptide in beta cells and suggest the presence of an intramitochondrial pool of islet amyloid polypeptide involved in beta-cell apoptosis.

Implication of Gut Microbiome in Brain Chemistry and Behavior

Human microbiome colonization starts during the birth and keeps modulating and establishing itself till adult stage. Advances in research techniques have shown evidences displaying the role of microbiome in brain and behavior development in addition to its involvement in immune, metabolic and physiologic function. Dysbiosis of gut microbiome disturbing the homeostasis with host leads to various diseases. Absence of microbiome in mouse affects the stimulation of nerves with simultaneous changes in behavior and brain chemistry. The perturbed microbiota during neonatal life leads to behavioral shifts which may persist even in adulthood. Short chain fatty acid (SCFA) released after microbial fermentation of undigested food components are able to regulate microglia homeostasis which serve as macrophages of the central nervous system (CNS) and are critical in CNS diseases. Impaired microglia signaling is implicated in neurodevelopmental, neurodegenerative disorders and aging. The administration of antimicrobial agents in mice has revealed altered anxiolytic behavior and correspondingly the brain chemistry, i.e., changes in brain derived neurotrophic factor (BDNF) level. The administration of combinations of probiotic bacteria affect brain function including anxiety, mood, and memory indicating their potential use in therapeutic approach depending upon their strain specific effect. Thus these accumulating reports indicate relevance of gut microbiome in brain chemistry and physiology consequently in brain related disorders.

AMYLIN DYSHOMEOSTASIS: A NON-AD PROCESS CONTRIBUTING TO AN AD PHENOTYPE

patients was 85.4%. In model 2, AD patients and FTD patients were classified with 90.2% accuracy. The accuracies in discriminating between FTD subtypes were 85.0%, 89.9%, 92.8% in model 3 to 5, respectively. Patterns of discriminative cortical regions were consistent with previous observations in some degree, although significantly influenced by the combination of groups compared. SvPPA group showed significant discriminative value in left temporal region whereas characteristic change in bilateral frontal region was observed in bvFTD group. When compared with svPPA group, nfvPPA group showed significant difference especially in bilateral temporal pole. By contrast, when compared with bvFTD group, discriminative regions of nfvPPA group mainly distributed over left frontal cortex. Conclusions:Our method therefore demonstrated high classification performance in distinguishing FTD subtypes from AD and normal controls, and also in further distinguishing FTD subtypes from each other, supporting the discriminative power of our method in diagnosis.

Amylin and diabetic cardiomyopathy – amylin-induced sarcolemmal Ca2 + leak is independent of diabetic remodeling of myocardium

Amylin is a pancreatic β-cell hormone co-secreted with insulin, plays a role in normal glucose homeostasis, and forms amyloid in the pancreatic islets of individuals with type-2 diabetes. Aggregated amylin is also found in blood and extra-pancreatic tissues, including myocardium. Myocardial amylin accumulation is associated with myocyte Ca2+ dysregulation in diabetic rats expressing human amylin. Whether deposition of amylin in the heart is a consequence of or a contributor to diabetic cardiomyopathy remains unknown. We used amylin knockout (AKO) mice intravenously infused with either human amylin (i.e, the aggregated form) or non-amyloidogenic (i.e., monomeric) rodent amylin to test the hypothesis that aggregated amylin accumulates in the heart in the absence of diabetes. AKO mice infused with human amylin, but not rodent amylin, showed amylin deposits in the myocardium. Cardiac amylin level was larger in males compared to females. Sarcolemmal Ca2+ leak and Ca2+ transients were increased in myocytes isolated from males infused with human amylin while no significant changes occurred in either females injected with human amylin or in rat amylin-infused mice. In isolated cardiac myocytes, the amylin receptor antagonist AC-187 did not effectively block the interaction of amylin with the sarcolemma. In conclusion, circulating aggregated amylin accumulates preferentially in male vs. female hearts and its effects on myocyte Ca2+ cycling do not require diabetic remodeling of the myocardium. This article is part of a Special issue entitled Cardiac adaptations to obesity, diabetes and insulin resistance, edited by Professors Jan F.C. Glatz, Jason R.B. Dyck and Christine Des Rosiers.

DIABETES-ASSOCIATED AMYLIN DYSHOMEOSTASIS PROVOKES BRAIN WHITE MATTER DISEASE AND BEHAVIOR CHANGES: AN ANIMAL MODEL

Background:The amyloid hypothesis proposes that the amyloid pathology affects a series of downstream AD pathophysiology; changes in the brain metabolism, aggregation of neurofibrillary tangles, dysfunctional network, structural changes, and cognitive decline. This is supported by the typical pattern of amyloid-beta (Ab) deposition that overlaps with the regional hypometabolism based on FDG-PET. Felix et al. have reported abnormal metabolic network in MCI Ab+ individuals compared to Abindividuals. However, the interregional association between Ab and FDG as well as interregional metabolic network (IMN) is still elusive. Here, we used Alzheimer’s disease neuroimaging initiative (ADNI) database and McGill-R-Thy1-APP (Tg) to investigate the difference in IMN between Ab+ and Ab-. Furthermore, we characterized the difference in interregional association between Ab and metabolism (IAMN) between Ab+ and Ab-.Methods:A total of 392 subjects from ADNI cohort (228 CN1⁄4 Ab-, 164 MCI+ 1⁄4 Ab+) was used and 17 (7 WT 1⁄4Ab-, 10 Tg 1⁄4 Ab+) were used for this study. The ROC-based Ab cut-off (1.286) was used to characterize CN-1⁄4 Abor MCI+1⁄4 Ab+ from CN (287) and AD (176). Human IMN was generated based on the 201 nodes in 228 CNand 164 MCI+. Rat IMN was generated based on 61 nodes in 7 WT and 10 Tg. The same regions were used to generate IAMN. Fisher’s Z-transformation is applied to compare the network association between CNand MCI+ as well as WTand Tg. Results:MCI+ showed greater association compared to CNin hippocampus, medial and lateral temporal cortex, superior parietal cortex, and fornix in IMN. Similarly, Tg showed greater association compared to WT in basal temporal cortex, parietotemporal cortex, and hypothalamus in IMN. Furthermore, regional Ab association in lateral frontal cortex, lateral temporal cortex, and PCC/Precuneus in IMN metabolism were greater in MCI+ compared to CN-. Analogous regional Ab associations were greater in Tg compared to WT in IMN. Conclusions: The presence of Ab is associated with greater IMN strength in the regions that are thought to show first amyloid pathology. In addition, Ab deposition in the hub regions of DMN is associated with greater IMN.

INTRANEURONAL AMYLIN DEPOSITION, PEROXIDATIVE MEMBRANE INJURY AND INCREASED IL-1SS SYNTHESIS IN BRAINS OF ALZHEIMER’S DISEASE PATIENTS WITH TYPE-2 DIABETES AND DIABETIC HIP RATS

Background: Alzheimer disease (AD) is characterized by accumulation of amyloid-b plaques from the amyloid precursor protein, neurofibrillary tangles, widespread synaptic loss, inflammation, oxidative damage and neuronal death. Animal models have become an indispensable tool, both to increase the knowledge about the pathology of the disease, as well as, for the discovery of novel pharmaceutical preparations for the treatment of AD. However, there are a lot of examples of pharmaceutical preparations that have been developed for the treatment of AD and the results obtained in preclinical studies, have not been reproduced in the clinical studies. Among the causes of low clinical efficacy of these pharmaceutical preparations, it is the choosing of the suitable animal model during the preclinical phase of research. The objective of this work it’s to propose a strategy to allow us to minimize such difficulty. Methods:We suggest starting with identification of the therapeutic “goal” of the preparation inside the physiology of the AD. Another phase should be to choose the specific groups of patients to evaluate the preparation, and finally to select the appropriate experimental models, or the combination of them. This last step should take into account a logical sequential order of complexity, from in vitro to in vivo experimental models. Results: As an example of application of the proposed strategy, this work includes the selection of animal models to evaluate natural products to revert the insulin resistance and the neuroinflammation. Conclusions:This strategy contributed to increase the quality of preclinical studies.

Clinically relevant animal model to investigate neuropathological response to vascular amylin deposits in diabetes

not available. S3-01-02 IS THERE A NEED FOR LARGER PREVENTION TRIALS? Laura Fratiglioni, Aging Research Center, Karolinska Institutet & Stockholm University, Stockholm, Sweden. Contact e-mail: laura. fratiglioni@ki.se Abstract not available. S3-01-03 EXPERIENTIAL AND PSYCHOSOCIAL RISKnot available. S3-01-03 EXPERIENTIAL AND PSYCHOSOCIAL RISK FACTORS FOR DEMENTIA David A. Bennett, Rush University Medical Center, Chicago, IL, USA. Contact e-mail: David_A_Bennett@rush.edu Abstract not available.not available. S3-01-04 IS IT TIME TO GO BEYOND RANDOMIZED