Rapid, scalable assay of amylin-ß amyloid co-aggregation in brain tissue and blood.

Islet amyloid polypeptide (amylin) secreted from the pancreas crosses from the blood to the brain parenchyma and forms cerebral mixed amylin-ß amyloid (Aß) plaques in persons with Alzheimer's disease (AD). Cerebral amylin-Aß plaques are found in both sporadic and early-onset familial AD; however, the role of amylin-Aß co-aggregation in potential mechanisms underlying this association remains unknown, in part due to lack of assays for detection of these complexes. Here, we report the development of an ELISA to detect amylin-Aß hetero-oligomers in brain tissue and blood. The amylin-Aß ELISA relies on a monoclonal anti-Aß mid-domain antibody (detection) and a polyclonal anti-amylin antibody (capture) designed to recognize an epitope that is distinct from the high affinity amylin-Aß binding sites. The utility of this assay is supported by the analysis of molecular amylin-Aß codeposition in postmortem brain tissue obtained from persons with and without AD pathology. By using transgenic AD-model rats, we show that this new assay can detect circulating amylin-Aß hetero-oligomers in the blood and is sensitive to their dissociation to monomers. This is important because therapeutic strategies to block amylin-Aß co-aggregation could reduce or delay the development and progression of AD.

Skin capillary amylin deposition resembles brain amylin vasculopathy in rats.

BACKGROUND AND PURPOSE: Human amylin is a 37 amino-acid pancreatic peptide that forms neuro-toxic aggregates that deposit in the endothelium of brain capillaries of patients with diabetes, potentially contributing to cerebral small vessel ischemic injury. Pathogenic amylin also deposits in the capillary endothelium in other organs, including the skin. The aim of this study was to test the hypothesis that skin capillary amylin deposition correlates with cerebral small vessel amylin deposition, potentially providing a clinically useful marker of cerebral amylin deposition. METHODS: Immunohistochemistry (IHC) was performed for human amylin and collagen IV in brain and skin sections of rats (age 15-16 months) with pancreatic overexpression of amyloidogenic human amylin polypeptide (HIP rats), and control rats (Wild type; WT; rats that express non-amyloidogenic rat amylin) using antibodies binding amylin (n = 5 male and 5 female rats for each group) and antibodies binding Hypoxia inducing factor (HIF)-1α and HIF-2α (n = 3 for each group). The reactive amylin-aldehyde 4-hydroxynonenal (4-HNE) adduct was measured in skin homogenates. (n = 4 for each group) RESULTS: Brain capillaries isolated from HIP rats had higher amylin content compared to WT rats using Western blot with anti-amylin antibody (p = 0.0010). The HIF-1α and HIF-2α immunoreactivity signals in skin from HIP and WT rats were similar (p = 0.2 for HIF-1 α, and p = 0.75 for HIF-2α). Amylin-4HNE adduct formation was higher in HIP rats compared to WT rats (p = 0.0014). There was phenotypic similarity between brain and skin capillary amylin based on co-staining for human amylin and collagen IV in both HIP and WT rats. CONCLUSION: Skin and brain capillary amylin deposition are similar providing evidence that a skin biopsy might be providing a potential biomarker for diabetes-associated intracranial vasculopathy.

Pulmonary function parameters and its determinants among cement factory workers in Chhattisgarh: A cross-sectional study.

BACKGROUND: Cement in one hand is the most used substance for construction all over the world but on the other hand prolonged exposure from cement dust particles along with smoking, long working duration in dusty environments and increasing age impairs pulmonary functions. OBJECTIVES: The study aimed to determine the effect of cement dust on the pulmonary functions of cement factory workers. METHODS: It was a cross-sectional observational study conducted from October 2019 to February 2020 among 360 workers of cement factories of Chhattisgarh state selected by systematic random sampling who were interviewed. Spirometry was done and their forced vital capacity, forced expiratory volume in one second, Forced expiratory flow, peak expiratory flow rate, and lung age were determined with a flow-sensing spirometer. Data were collected, entered in MS Excel spreadsheet, and analyzed using SPSS software (version 20.0) for Chi-square test, linear regression, and general linear model. RESULTS: One-third of the study subjects had pulmonary dysfunction, out of which 10% and 30% were having severe and moderate dysfunction, respectively. Significant higher Odds for developing impaired pulmonary functions were seen among >40 years of age (adjusted odds ratio [AOR] =1.88 [1.13, 3.12]), more than 10 years of service (AOR = 4.69 [2.32, 9.53]) and smokers (AOR = 4.45 [2.53, 7.83]). CONCLUSION: Working in dusty environment along with other factors in cement factories significantly decrease lung parameters. Exposure with dust is strong predictor for chronic respiratory symptoms.

Diabetic microcirculatory disturbances and pathologic erythropoiesis are provoked by deposition of amyloid-forming amylin in red blood cells and capillaries.

In the setting of type-2 diabetes, there are declines of structural stability and functionality of blood capillaries and red blood cells (RBCs), increasing the risk for microcirculatory disturbances. Correcting hyperglycemia is not entirely effective at reestablishing normal cellular metabolism and function. Therefore, identification of pathological changes occurring before the development of overt hyperglycemia may lead to novel therapeutic targets for reducing the risk of microvascular dysfunction. Here we determine whether RBC-capillary interactions are altered by prediabetic hypersecretion of amylin, an amyloid forming hormone co-synthesized with insulin, and is reversed by endothelial cell-secreted epoxyeicosatrienoic acids. In patients, we found amylin deposition in RBCs in association with type-2 diabetes, heart failure, cancer and stroke. Amylin-coated RBCs have altered shape and reduced functional (non-glycated) hemoglobin. Amylin-coated RBCs administered intravenously in control rats upregulated erythropoietin and renal arginase expression and activity. We also found that diabetic rats expressing amyloid-forming human amylin in the pancreas (the HIP rat model) have increased tissue levels of hypoxia-inducible transcription factors, compared to diabetic rats that express non-amyloid forming rat amylin (the UCD rat model). Upregulation of erythropoietin correlated with lower hematocrit in the HIP model indicating pathologic erythropoiesis. In the HIP model, pharmacological upregulation of endogenous epoxyeicosatrienoic acids protected the renal microvasculature against amylin deposition and also reduced renal accumulation of HIFs. Thus, prediabetes induces dysregulation of amylin homeostasis and promotes amylin deposition in RBCs and the microvasculature altering RBC-capillary interaction leading to activation of hypoxia signaling pathways and pathologic erythropoiesis. Hence, dysregulation of amylin homeostasis could be a therapeutic target for ameliorating diabetic vascular complications.

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

Amylin is a pancreatic ß-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.

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

OBJECTIVE: 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. METHODS: Rats overexpressing amyloidogenic (human) amylin in the pancreas (HIP rats) and amylin knockout (AKO) rats intravenously infused with aggregated amylin were used for in vivo phenotyping. We also carried out biochemical analyses of human brain tissues and studied the effects of the aggregated amylin on endothelial cells ex vivo. RESULTS: Amylin deposition in brain blood vessels is associated with vessel wall disruption and abnormal surrounding neuropil in patients with type 2 diabetes and dementia, in HIP rats, and in AKO rats infused with aggregated amylin. HIP rats have brain microhemorrhages, white matter injury, and neurologic deficits. Vascular amylin deposition provokes loss of endothelial cell coverage and tight junctions. Intravenous infusion in AKO rats of human amylin, or combined human amylin and apolipoprotein E4, showed that amylin binds to plasma apolipoproteins. The intravenous infusion of apolipoprotein E4 exacerbated the brain accumulation of aggregated amylin and vascular pathology in HIP rats. INTERPRETATION: These data identify vascular amylin deposition as a trigger of brain endothelial dysfunction that is modulated by plasma apolipoproteins and represents a potential therapeutic target in diabetes-associated dementia and stroke. Ann Neurol 2017;82:208-222.

Effect of salicin on gut inflammation and on selected groups of gut microbiota in dextran sodium sulfate induced mouse model of colitis.

OBJECTIVE AND DESIGN: This study was undertaken to evaluate the anti-inflammatory effect of the pure compound salicin on dextran sulfate sodium (DSS)-induced colitis in a mouse model and to quantify the major gut bacteria during the treatment. MATERIAL OR SUBJECTS: Experimental colitis was induced in Swiss albino mice by dissolving 2 % DSS in their drinking water for 7 days. Five mice were used in each group. TREATMENT: Salicin (100 and 200 mg per body weight) was administered daily through oral gavage for 7 days. METHODS: Disease activity index (DAI), colon length, myeloperoxidase (MPO) assay, pro-inflammatory cytokine expression, histological changes and absolute number of gut microbiota were measured after treatment. Student's t test was applied for statistical analysis. RESULTS: Salicin significantly attenuated DSS-induced DAI scores, shortening of colon length and tissue MPO activity. Salicin administration also effectively and dose-dependently prevented pro-inflammatory cytokine expression in DSS-induced colitis mice. Histological examination indicated that salicin suppressed edema, mucosal damage and the loss of crypts induced by DSS. Oral administration of salicin in DSS-treated mice prevented loss of gut microbiota during the short period of treatment. CONCLUSIONS: Salicin has an anti-inflammatory effect, and it may have therapeutic value in ameliorating inflammation during colitis.

TLR4 D299G polymorphism modulates cytokine expression in ulcerative colitis.

BACKGROUND: Toll-like receptor 4 (TLR4) is a key cell surface receptor which recognizes lipopolysaccharide that leads to activation of innate immune system. Association of single nucleotide polymorphisms (SNPs) in TLR4 gene with the inflammatory bowel disease is influenced by ethnicity of the study population. GOAL: To study association of SNPs in TLR4 gene in inflammatory bowel disease patients and to explore the influence of these SNPs on the level of mRNA expression of targeted cytokines in the ulcerative colitis (UC) biopsies. METHODS: Two polymorphisms of TLR4 (D299G, T399I) gene were genotyped by PCR-RFLP in 199 UC, 46 Crohn's disease (CD) patients, and 201 healthy controls. Expression of inflammatory cytokines was measured by RT-PCR in UC biopsies. Genotypes and allele frequencies were calculated by the Pearson χ test, Fisher exact test, Student t test, and ANOVA. RESULTS: TLR4 variant D299G showed significant association, with UC (P=0.009) and CD (P=0.039). T399I showed significant association with UC (P=0.006) but not with CD patients. Transcription of TLR4 (P=0.0006), tumor necrosis factor-α (P=0.0009), interferon-γ (P=0.028), interleukin (IL)-17 (P=0.01), IL-23 (P=0.0034), and IL-10 (P=0.018) were found to be significantly elevated in UC patients as compared to controls. Among UC patients, AG genotype of D299G was associated with decreased mRNA level of TLR4 (P=0.0069), tumor necrosis factor-α (P=0.018), IL-17 (P=0.017), and IL-23 (P=0.011) as compared to AA genotype patients. In GG genotype interferon-γ expression (P=0.014) was significantly decreased as compared to AA genotype. CONCLUSION: Polymorphisms in TLR4 gene were significantly associated with inflammatory bowel disease in North Indian population and they contribute in modulating transcription of inflammatory cytokines during UC leading to aberrant immune response.

Profiling of ABC transporters during active ulcerative colitis and in vitro effect of inflammatory modulators.

BACKGROUND AND AIM: Inflammatory bowel disease is characterized by chronic inflammation of the gastro intestinal tract that manifests as ulcerative colitis and Crohn's disease. Comparative expression profiles of selected ABC transporter genes during active ulcerative colitis and intestinal tuberculosis were studied, and we also investigated the effect of inflammatory modulators on the expression of the transporters in HT-29 cells. METHODS: Using the GEO database, we selected ABC transporter genes that are differentially regulated during active UC and validated the altered expression in biopsies samples by RT-PCR. We also analyzed the effect of inflammatory modulators like TNF-α, lipopolysaccharides (LPS) and drugs (5-ASA, prednisolone and hydrocortisone) on the expression of ABCA1, ABCB8, ABCF2 and ABCC4 using HT-29 cells. RESULTS: We observed significant up-regulation of ABCA1 and ABCA3 while ABCF2, ABCC6, ABCB8 and ABCC4 were down-regulated during UC. ABCC4 was up-regulated in ITB but down-regulated in UC, whereas others showed similar patterns both in UC and ITB. Upon stimulation of HT29 cells by TNF-α, up-regulation of ABCA1, ABCB8, ABCF2 and ABCC4 was seen, and further using inhibitors we found that it was mediated through reactive oxygen species or NF-kB or both. LPS caused a dose dependent and significant down-regulation of ABCB8, ABCF2 and ABCC4 without any effect on ABCA1. The cells treated with drugs 5-ASA, prednisolone and hydrocortisone, exhibited up-regulation of transporters only at a higher dose. CONCLUSION: Altered expression of the above transporters may be associated with the disease. The study also hints at possible mechanisms of differential expression.

The association between renal accumulation of pancreatic amyloid-forming amylin and renal hypoxia.

Chronic kidney disease (CKD) is increasing worldwide and is associated with diabetic states (obesity, prediabetes and type-2 diabetes mellitus). The kidney is intrinsically susceptible to low oxygen (hypoxia) and renal hypoxia plays a vital role in the progression of CKD. Recent studies suggest an association between CKD and renal deposition of amyloid-forming amylin secreted from the pancreas. Renal accumulation of amyloid-forming amylin is associated with hypertension, mitochondrial dysfunction, increased production of reactive oxygen species (ROS) and activation of hypoxia signaling in the kidney. In this review we will discuss potential associations between renal amylin amyloid accumulation, hypertension, and mechanism of hypoxia-induced kidney dysfunction, including activation of hypoxia-inducible factors (HIFs) and mitochondrial dysfunction.

A Community-Based Cross-Sectional Study on the Epidemiology of Injuries in Raipur City, Chhattisgarh.

BACKGROUND: Globally, injuries are a major public health concern. An injury is a physical damage that results when the human body is suddenly or briefly subjected to intolerable levels of energy. OBJECTIVES: The objectives of this study are to describe the nature and mechanism of injuries and their association with age and gender and to assess the health-seeking behavior and cost incurred due to mortality and morbidity related to injuries. METHODS AND MATERIALS: A cross-sectional study focused on the community was conducted in 10 chosen wards of Raipur City. The sample size was 310 injured individuals. The recall period was for a full year. Information was gathered by using a questionnaire that had been pretested. The results were given as percentages, and the association was determined using the chi-square test and Fischer's exact test. RESULTS: The majority (30.1%) of the study subjects suffered from cut/bite/open wound injuries, followed by fractures (17.3%). The leading type of injury was caused by falls (38.8%) and road traffic injuries (34.9%), followed by burns (7.1%) and dog bites (5.4%). Ninety percent of the study subjects had taken medical care. Half of them (51.3%) visited a private hospital, and 23.1% did not visit any hospital for treatment. Fifty percent of the study subjects or their family had expenses less than Indian National Rupee (INR) 500. A significant association was found between age and fracture and the sprain type of injury. The burn type of injury was more among females, which is significantly associated. A significant association was found between age and injury caused by a dog bite, fall, and traffic. The association between gender and injury caused by traffic, burn, and fall was significant. CONCLUSIONS: Focusing on reducing injury-related morbidity may be crucial in injury prevention techniques including behavioral changes, health education, and the urgent need for the proper implementation and oversight of a road safety act.

Assessment of Prevalence of Hypertension and its Risk Factors among Adult Tribal Population Residing in Lohandiguda Block of Bastar District of Chhattisgarh.

Background: Hypertension is known as the silent killer. It comprehends the top rank in non-infectious disease amongst adults; accountable for the deaths every year across the world. It is essential to consider the individual impact of risk factors and their impact on hypertension. This study thus elicited the socio-demographic characteristics, the prevalence of hypertension and associated risk factors, and its impact on adults with hypertension. To estimate the hypertension prevalence and its associated risk factors among adult tribal populations aged 25-60 years residing in Lohandiguda block of Bastar district of Chhattisgarh. Material and Methods: A community-based cross-sectional analytical study was used and the setting was done at the field practice area under the three primary health centers of Lohandiguda block, Bastar district of Chhattisgarh. It was carried out among 330 adult tribes residing for ≥1 year in the present locality. Data was collected by door-to-door visits through pre-designed, pretested, semi-structured questionnaire via face-to-face interview method and anthropometric measurement was done by using standard guidelines. The sampling method was multistage sampling. IBM SPSS STATISTICS-20.0 (IBM Corp., Armonk, NY, USA) software. Results: The overall prevalence of pre-hypertension and hypertension among tribal subjects was 34.9% and 47.3%, respectively. Of total hypertensive 27.3% were having stage-1 hypertension, 13.9% were having stage-2 hypertension and 6.0% were already diagnosed cases. Risk factors found in multivariate analysis are occupation (unemployed 0.012), frequency of smokeless tobacco used per day (0.,017) and central obesity (0.000). Conclusions: As hypertension is a multi-factorial disease the study found strong predictors like occupation, frequency of smokeless tobacco per day and having central obesity with significant difference.

Aß efflux impairment and inflammation linked to cerebrovascular accumulation of amyloid-forming amylin secreted from pancreas.

Impairment of vascular pathways of cerebral ß-amyloid (Aß) elimination contributes to Alzheimer disease (AD). Vascular damage is commonly associated with diabetes. Here we show in human tissues and AD-model rats that bloodborne islet amyloid polypeptide (amylin) secreted from the pancreas perturbs cerebral Aß clearance. Blood amylin concentrations are higher in AD than in cognitively unaffected persons. Amyloid-forming amylin accumulates in circulating monocytes and co-deposits with Aß within the brain microvasculature, possibly involving inflammation. In rats, pancreatic expression of amyloid-forming human amylin indeed induces cerebrovascular inflammation and amylin-Aß co-deposits. LRP1-mediated Aß transport across the blood-brain barrier and Aß clearance through interstitial fluid drainage along vascular walls are impaired, as indicated by Aß deposition in perivascular spaces. At the molecular level, cerebrovascular amylin deposits alter immune and hypoxia-related brain gene expression. These converging data from humans and laboratory animals suggest that altering bloodborne amylin could potentially reduce cerebrovascular amylin deposits and Aß pathology.

The Outcome of Pregnancy Among Tobacco Users in Tertiary Care Hospital of Chhattisgarh Province of India.

BACKGROUND: Tobacco use is responsible for numerous adverse pregnancy outcomes for females and their infants. The aim of this study was to explore the adverse outcome of tobacco use among pregnant females. METHOD:  A cross-sectional study was conducted on 1250 females in the third trimester of pregnancy from April to June 2022, which were exposed to tobacco use in the form of gudaku, tobacco chewing, gutka, or smoking. Complications and outcomes during and after pregnancy were recorded based on self-administered questionnaires. Statistical analysis was performed using the Statistical Package for Social Sciences (SPSS) (IBM SPSS Statistics, Armonk, NY) software version 20.0 for categorical data, frequencies (n) and percentages (%) were calculated, and the chi-square test was used for determining intergroup differences. RESULTS:  Out of 1250 females, tobacco exposure was present among 429 (34.3%), and 821 (65.7%) had no tobacco exposure. Of 429, 36.10% of females complained about complications such as abortion (1.60%), antepartum hemorrhage (0.90%), congenital anomaly (0.20%), infertility (1.20%), intrauterine fetal death (IUFD) (0.50%), intrauterine growth restriction (IUGR) (0.90%), oligohydramnios (OLIGO) (3.30%), preterm labor (18.40%), premature rupture of membrane (6.30%), and anemia (2.80%), which were slightly higher than the females with no tobacco exposure. In tobacco users, obstructive complications were found to be significant with a p value of 0.0036. CONCLUSION: Our study concluded that tobacco use could have an adverse effect on their fetus and infants, as well as the pregnant females themselves. Policymakers need to ensure effective strategies that pregnant females, their partners, and close relatives need to have enough knowledge to avoid potential risks.

Gestational diabetes triggers postpartum cardiac hypertrophy via activation of calcineurin/NFAT signaling.

Population-based studies identified an association between a prior pregnancy complicated by gestational diabetes mellitus (GDM) and cardiac hypertrophy and dysfunction later in life. It is however unclear whether GDM initiates this phenotype and what are the underlying mechanisms. We addressed these questions by using female rats that express human amylin (HIP rats) as a GDM model and their wild-type (WT) littermates as the normal pregnancy model. Pregnant and two months postpartum HIP females had increased left-ventricular mass and wall thickness compared to non-pregnant HIP females, which indicates the presence of concentric hypertrophy. These parameters were unchanged in WT females during both pregnancy and postpartum periods. Hypertrophic Ca2+-dependent calcineurin/NFAT signaling was stimulated two months after giving birth in HIP females but not in the WT. In contrast, the CaMKII/HDAC hypertrophy pathway was active immediately after giving birth and returned to the baseline by two months postpartum in both WT and HIP females. Myocytes from two months postpartum HIP females exhibited slower Ca2+ transient relaxation and higher diastolic Ca2+ levels, which may explain calcineurin activation. No such effects occurred in the WT. These results suggest that a GDM-complicated pregnancy accelerates the development of pathological cardiac remodeling likely through activation of calcineurin/NFAT signaling.

The association of circulating amylin with ß-amyloid in familial Alzheimer's disease.

INTRODUCTION: This study assessed the hypothesis that circulating human amylin (amyloid-forming) cross-seeds with amyloid beta (Aß) in early Alzheimer's disease (AD). METHODS: Evidence of amylin-AD pathology interaction was tested in brains of 31 familial AD mutation carriers and 20 cognitively unaffected individuals, in cerebrospinal fluid (CSF) (98 diseased and 117 control samples) and in genetic databases. For functional testing, we genetically manipulated amylin secretion in APP/PS1 and non-APP/PS1 rats. RESULTS: Amylin-Aß cross-seeding was identified in AD brains. High CSF amylin levels were associated with decreased CSF Aß42 concentrations. AD risk and amylin gene are not correlated. Suppressed amylin secretion protected APP/PS1 rats against AD-associated effects. In contrast, hypersecretion or intravenous injection of human amylin in APP/PS1 rats exacerbated AD-like pathology through disruption of CSF-brain Aß exchange and amylin-Aß cross-seeding. DISCUSSION: These findings strengthened the hypothesis of circulating amylin-AD interaction and suggest that modulation of blood amylin levels may alter Aß-related pathology/symptoms.

Contributing Factors to Diabetic Brain Injury and Cognitive Decline.

The link of diabetes with co-occurring disorders in the brain involves complex and multifactorial pathways. Genetically engineered rodents that express familial Alzheimer's disease-associated mutant forms of amyloid precursor protein and presenilin 1 (PSEN1) genes provided invaluable insights into the mechanisms and consequences of amyloid deposition in the brain. Adding diabetes factors (obesity, insulin impairment) to these animal models to predict success in translation to clinic have proven useful at some extent only. Here, we focus on contributing factors to diabetic brain injury with the aim of identifying appropriate animal models that can be used to mechanistically dissect the pathophysiology of diabetes-associated cognitive dysfunction and how diabetes medications may influence the development and progression of cognitive decline in humans with diabetes.

Intraneuronal Amylin Deposition, Peroxidative Membrane Injury and Increased IL-1ß 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 ß-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 ß-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 Alzheimer's disease (AD) patients, preponderantly those with type-2 diabetes. Here, we report that, in addition to amylin plaques and mixed amylin-Aß 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)-1ß. 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-1ß 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.

Hyperamylinemia Increases IL-1ß 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 ß-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-1ß (IL-1ß) 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-1ß might function as a sensor of myocyte amylin uptake and a potential mediator of myocyte injury.