Amylin alters human brain pericyte viability and NG2 expression

Pericytes in Alzheimer's disease: Key players and therapeutic targets

Alzheimer's disease (AD) is a devastating neurodegenerative disorder that leads to progressive cognitive decline and neuropathological changes. Pericytes, which are vessel mural cells on the basement membrane of capillaries, play a crucial role in regulating cerebrovascular functions and maintaining neurovascular unit integrity. Emerging research substantiates the involvement of pericytes in AD. This review provides a comprehensive overview of pericytes, including their structure, origin, and markers and various functions within the central nervous system. Emphatically, the review explores the intricate mechanisms through which pericytes contribute to AD, including their interactions with amyloid beta and apolipoprotein E, as well as various signaling pathways. The review also highlights potential for targeted pericyte therapy for AD, with a focus on stem cell therapy and drug treatments. Future research directions include the classification of pericyte subtypes, studies related to aging, and the role of pericytes in exosome-related mechanisms in AD pathology. In conclusion, this review consolidates current knowledge on the pivotal roles of pericytes in AD and their potential as therapeutic targets, providing valuable insights for future research and clinical interventions aimed at addressing the impact of AD on patients' lives.

Association between vascular aging and cognitive function in Chinese adults

BACKGROUND

Vascular health has been associated with cognition but related evidence is limited in Chinese. The objective of this study was to examine the association of vascular aging assessed by arterial stiffness and blood pressure with cognitive function in an unselected Chinese population.

METHODS

In the Tianning Cohort (N = 5158), indicators of arterial stiffness and blood pressure including carotid-femoral pulse wave velocity (cfPWV), ankle-brachial index (ABI), pulse pressure (PP), systolic blood pressure (SBP), and diastolic blood pressure (DBP) were measured. Cognitive function was assessed using the Mini Mental State Examination (MMSE) questionnaire. We applied Poisson regression and logistic regression to examine the associations of vascular aging and blood pressure with cognitive function.

RESULTS

76 (1.47%) participants had impaired cognitive function diagnosed by a MMSE score of less than 24 points. Participants with a higher level of PP were more likely to have a decreased score of MMSE (β=-0.0121, P < 0.001 for log-transformed pulse pressure) and a higher risk of having impaired cognitive function (OR = 5.95, 95%CI: 2.02-17.79, P < 0.001 for log-transformed PP). Per standard deviation increment in SBP was significantly associated with lower MMSE score (β=-0.0020, P < 0.001) and impaired cognitive function (OR = 1.69, 95%CI: 1.38-2.06, P < 0.001). No significant associations were found regarding other parameters.

CONCLUSIONS

Blood pressure and hypertension were associated with cognitive function in Chinese adults. PP may be a potential predictor for impaired cognitive function.

Effect of spermidine on long non-coding RNAs MALAT1 in a rotenone induced-rat model of Parkinson's disease

BACKGROUND

Spermidine is a natural biologically active substance that has widespread influences on the body.

OBJECTIVE

This study aims to enhance our understanding of the potential effect of spermidine on long non-coding RNA MALAT1 and explore the underlying mechanism in the rotenone-induced rat model of Parkinson's disease.

METHODS

Rats were sacrificed after locomotor behavioral testing. Striatal tissues were used to assess the expression of MALAT1, oxidative stress markers, and autophagy markers.

RESULTS

Our study found that treatment with spermidine for 2 weeks during the induction of the model significantly improved behavioral assessment, dopamine levels, and attenuated the histopathological changes that occurred in PD in comparison to the non-treated group.

CONCLUSION

Our preliminary study supports the protective effect of spermidine on the activation of autophagy and its antioxidant properties. Part of the antioxidant activity is due to the inhibition of MALAT1. However, MALAT1 does not correlate with the spermidine-induced autophagy pathway.

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.

Neuroinflammation induced by amyloid-forming pancreatic amylin: Rationale for a mechanistic hypothesis

Amylin is a systemic neuroendocrine hormone co-expressed and co-secreted with insulin by pancreatic β-cells. In persons with thype-2 diabetes, amylin forms pancreatic amyloid triggering inflammasome and interleukin-1β signaling and inducing β-cell apoptosis. Here, we summarize recent progress in understanding the potential link between amyloid-forming pancreatic amylin and Alzheimer's disease (AD). Clinical data describing amylin pathology in AD alongside mechanistic studies in animals are reviewed. Data from multiple research teams indicate higher amylin concentrations are associated with increased frequency of cognitive impairment and amylin co-aggregates with β-amyloid in AD-type dementia. Evidence from rodent models further suggests cerebrovascular amylin accumulation as a causative factor underlying neurological deficits. Analysis of relevant literature suggests that modulating the amylin-interleukin-1β pathway may provide an approach for counteracting neuroinflammation in AD.

Type-2 Diabetes, Pancreatic Amylin, and Neuronal Metabolic Remodeling in Alzheimer's Disease

Type-2 diabetes raises the risk for Alzheimer's disease (AD)-type dementia and the conversion from mild cognitive impairment to dementia, yet mechanisms connecting type-2 diabetes to AD remain largely unknown. Amylin, a pancreatic β-cell hormone co-secreted with insulin, participates in the central regulation of satiation, but also forms pancreatic amyloid in persons with type-2 diabetes and synergistically interacts with brain amyloid β (Aβ) pathology, in both sporadic and familial Alzheimer's disease (AD). Growing evidence from studies of tumor growth, together with early observations in skeletal muscle, indicates amylin as a potential trigger of cellular metabolic reprogramming. Because the blood, cerebrospinal fluid, and brain parenchyma in humans with AD have increased concentrations of amylin, amylin-mediated pathological processes in the brain may involve neuronal metabolic remodeling. This review summarizes recent progress in understanding the link between prediabetic hypersecretion of amylin and risk of neuronal metabolic remodeling and AD and suggests nutritional and medical effects of food constituents that might prevent and/or ameliorate amylin-mediated neuronal metabolic remodeling.

Molecular mechanisms linking type 2 diabetes mellitus and late-onset Alzheimer's disease: A systematic review and qualitative meta-analysis

Research evidence indicating common metabolic mechanisms through which type 2 diabetes mellitus (T2DM) increases risk of late-onset Alzheimer's dementia (LOAD) has accumulated over recent decades. The aim of this systematic review is to provide a comprehensive review of common mechanisms, which have hitherto been discussed in separate perspectives, and to assemble and evaluate candidate loci and epigenetic modifications contributing to polygenic risk linkages between T2DM and LOAD. For the systematic review on pathophysiological mechanisms, both human and animal studies up to December 2023 are included. For the qualitative meta-analysis of genomic bases, human association studies were examined; for epigenetic mechanisms, data from human studies and animal models were accepted. Papers describing pathophysiological studies were identified in databases, and further literature gathered from cited work. For genomic and epigenomic studies, literature mining was conducted by formalised search codes using Boolean operators in search engines, and augmented by GeneRif citations in Entrez Gene, and other sources (WikiGenes, etc.). For the systematic review of pathophysiological mechanisms, 923 publications were evaluated, and 138 gene loci extracted for testing candidate risk linkages. 3 57 publications were evaluated for genomic association and descriptions of epigenomic modifications. Overall accumulated results highlight insulin signalling, inflammation and inflammasome pathways, proteolysis, gluconeogenesis and glycolysis, glycosylation, lipoprotein metabolism and oxidation, cell cycle regulation or survival, autophagic-lysosomal pathways, and energy. Documented findings suggest interplay between brain insulin resistance, neuroinflammation, insult compensatory mechanisms, and peripheral metabolic dysregulation in T2DM and LOAD linkage. The results allow for more streamlined longitudinal studies of T2DM-LOAD risk linkages.

The Contribution of Type 2 Diabetes to Parkinson's Disease Aetiology

Type 2 diabetes (T2D) and Parkinson's disease (PD) are chronic disorders that have a significant health impact on a global scale. Epidemiological, preclinical, and clinical research underpins the assumption that insulin resistance and chronic inflammation contribute to the overlapping aetiologies of T2D and PD. This narrative review summarises the recent evidence on the contribution of T2D to the initiation and progression of PD brain pathology. It also briefly discusses the rationale and potential of alternative pharmacological interventions for PD treatment.

Role of autophagy in angiogenic potential of vascular pericytes

The vasculature system is composed of a multiplicity of juxtaposed cells to generate a functional biological barrier between the blood and tissues. On the luminal surface of blood vessels, endothelial cells (ECs) are in close contact with circulating cells while supporting basal lamina and pericytes wrap the abluminal surface. Thus, the reciprocal interaction of pericytes with ECs is a vital element in the physiological activity of the vascular system. Several reports have indicated that the occurrence of pericyte dysfunction under ischemic and degenerative conditions results in varied micro and macro-vascular complications. Emerging evidence points to the fact that autophagy, a conserved self-digestive cell machinery, can regulate the activity of several cells like pericytes in response to various stresses and pathological conditions. Here, we aim to highlight the role of autophagic response in pericyte activity and angiogenesis potential following different pathological conditions.

Construction and Identification of a Breast Bioreactor for Human-Derived Hypoglycemic Protein Amylin

The mammary gland of mammals can generate numerous bioactive proteins. To express the human amylin protein in the mammary glands of domestic animals, we engineered a transgenic mammary gland bioreactor. For this study, we produced transgenic mice through prokaryotic microinjection. RT-PCR, qPCR, and Western blotting confirmed the presence of transgenes in the mice. The ELISA assay indicated an amylin yield of approximately 1.44 μg/mL in the mice milk. Further research revealed that consuming milk containing amylin resulted in a slight, but insignificant enhancement in food consumption, blood sugar equilibrium, and glucose tolerance. The influence of amylin-fortified milk on the abundance of fecal strains in mice was examined, and a significant difference in the quantity of strains needed for fatty acid synthesis and metabolism was discovered. The amylin protein gathered from humans is safe to consume, as no harmful effects were detected in the mice. Our study examined the production of human amylin using a new safety strategy that could potentially alleviate diabetic symptoms in the future through oral administration of milk containing amylin.

A pancreatic player in dementia: pathological role for islet amyloid polypeptide accumulation in the brain

Type 2 diabetes mellitus patients have a markedly higher risk of developing dementia. While multiple factors contribute to this predisposition, one of these involves the increased secretion of amylin, or islet amyloid polypeptide, that accompanies the pathophysiology of type 2 diabetes mellitus. Islet amyloid polypeptide accumulation has undoubtedly been implicated in various forms of dementia, including Alzheimer's disease and vascular dementia, but the exact mechanisms underlying islet amyloid polypeptide's causative role in dementia are unclear. In this review, we have summarized the literature supporting the various mechanisms by which islet amyloid polypeptide accumulation may cause neuronal damage, ultimately leading to the clinical symptoms of dementia. We discuss the evidence for islet amyloid polypeptide deposition in the brain, islet amyloid polypeptide interaction with other amyloids implicated in neurodegeneration, neuroinflammation caused by islet amyloid polypeptide deposition, vascular damage induced by islet amyloid polypeptide accumulation, and islet amyloid polypeptide-induced cytotoxicity. There are very few therapies approved for the treatment of dementia, and of these, clinical responses have been controversial at best. Therefore, investigating new, targetable pathways is vital for identifying novel therapeutic strategies for treating dementia. As such, we conclude this review by discussing islet amyloid polypeptide accumulation as a potential therapeutic target not only in treating type 2 diabetes mellitus but as a future target in treating or even preventing dementia associated with type 2 diabetes mellitus.

Bloodborne Pancreatic Amylin, A Therapeutic Target for Alzheimer's Disease

Alzheimer Disease (AD) pathology has been linked to brain accumulation of β amyloid (Aβ) and neurofibrillary tau tangles. An intriguing question is whether targeting therapeutically factors independent of Aβ and tau pathologies could delay or even stop neurodegeneration. Amylin, a pancreatic hormone co-secreted with insulin, is believed to play a role in the central regulation of satiation and was shown to form pancreatic amyloid in persons with type-2 diabetes mellitus. Accumulating evidence demonstrates that amyloid-forming amylin secreted from the pancreas synergistically aggregates with vascular and parenchymal Aβ in the brain, in both sporadic and early-onset familial AD. Pancreatic expression of amyloid-forming human amylin in AD-model rats accelerates AD-like pathology, whereas genetically suppressed amylin secretion protects against AD effects. Thus, current data suggest a role of pancreatic amyloid-forming amylin in modifying AD; further research is required to test whether lowering circulating amylin levels early during AD pathogenesis may curb cognitive decline.

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.

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 (Aβ) 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 (IAPP_O) but not monomers (IAPP_M) 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 IAPP_M or IAPP_O were altered in AD patients compared with controls. However, our results show significantly lower IAPP_O-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 Aβ and tau, neurofibrillary tangles, and brain IAPP exclusively in APOE4 non-carriers. We speculate that the reduction in IAPP_O-IgA levels may be caused by increased plasma IAPP_O levels or masked epitopes in APOE4 carriers and propose that IgA and APOE4 status play a specific role in clearance of circulatory IAPP_O, which may influence the amount of IAPP deposition in the AD brain.

Type 2 Diabetes and Parkinson's Disease: A Focused Review of Current Concepts

Highly reproducible epidemiological evidence shows that type 2 diabetes (T2D) increases the risk and rate of progression of Parkinson's disease (PD), and crucially, the repurposing of certain antidiabetic medications for the treatment of PD has shown early promise in clinical trials, suggesting that the effects of T2D on PD pathogenesis may be modifiable. The high prevalence of T2D means that a significant proportion of patients with PD may benefit from personalized antidiabetic treatment approaches that also confer neuroprotective benefits. Therefore, there is an immediate need to better understand the mechanistic relation between these conditions and the specific molecular pathways affected by T2D in the brain. Although there is considerable evidence that processes such as insulin signaling, mitochondrial function, autophagy, and inflammation are involved in the pathogenesis of both PD and T2D, the primary aim of this review is to highlight the evidence showing that T2D-associated dysregulation of these pathways occurs not only in the periphery but also in the brain and how this may facilitate neurodegeneration in PD. We also discuss the challenges involved in disentangling the complex relationship between T2D, insulin resistance, and PD, as well as important questions for further research. © 2022 International Parkinson and Movement Disorder Society.

The microglia-blood vessel interactions in the developing brain

Microglia are the immune cells in the central nervous system (CNS). Once microglial progenitors are generated in the yolk sac, these cells enter the CNS and colonize its structures by migrating and proliferating during development. Although the microglial population in the CNS is still low in this stage compared to adults, these cells can associate with many surrounding cells, such as neural lineage cells and vascular-structure-composing cells, by extending their filopodia and with their broad migration capacity. Previous studies revealed multifaceted microglial actions on neural lineage cells, such as regulating the differentiation of neural progenitors and modulating neuronal positioning. Notably, microglia not only act on neural lineage cells but also interact with blood vessels, for example, by supporting vascular formation and integrity. On the other hand, blood vessels contribute to microglial colonization into the CNS and their migration at local tissues. Importantly, pericytes, the cells that encompass vascular endothelial cells, have been suggested to play a profound role in microglial function. This review summarizes recent advances in the understanding of the interaction of microglia and blood vessels, especially focusing on the significance of this interaction in CNS development, and discusses how microglial and blood vessel dysfunction leads to developmental disorders.

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

Impairment of vascular pathways of cerebral β-amyloid (Aβ) 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 Aβ clearance. Blood amylin concentrations are higher in AD than in cognitively unaffected persons. Amyloid-forming amylin accumulates in circulating monocytes and co-deposits with Aβ within the brain microvasculature, possibly involving inflammation. In rats, pancreatic expression of amyloid-forming human amylin indeed induces cerebrovascular inflammation and amylin-Aβ co-deposits. LRP1-mediated Aβ transport across the blood-brain barrier and Aβ clearance through interstitial fluid drainage along vascular walls are impaired, as indicated by Aβ 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 Aβ pathology.

Pericytes take up and degrade α-synuclein but succumb to apoptosis under cellular stress

Parkinson's disease (PD) is characterised by the progressive loss of midbrain dopaminergic neurons and the presence of aggregated α-synuclein (α-syn). Pericytes and microglia, two non-neuronal cells contain α-syn in the human brain, however, their role in disease processes is poorly understood. Pericytes, found surrounding the capillaries in the brain are important for maintaining the blood-brain barrier, controlling blood flow and mediating inflammation. In this study, primary human brain pericytes and microglia were exposed to two different α-synuclein aggregates. Inflammatory responses were assessed using immunocytochemistry, cytometric bead arrays and proteome profiler cytokine array kits. Fixed flow cytometry was used to investigate the uptake and subsequent degradation of α-syn in pericytes. We found that the two α-syn aggregates are devoid of inflammatory and cytotoxic actions on human brain derived pericytes and microglia. Although α-syn did not induce an inflammatory response, pericytes efficiently take up and degrade α-syn through the lysosomal pathway but not the ubiquitin-proteasome system. Furthermore, when pericytes were exposed the ubiquitin proteasome inhibitor-MG132 and α-syn aggregates, there was profound cytotoxicity through the production of reactive oxygen species resulting in apoptosis. These results suggest that the observed accumulation of α-syn in pericytes in human PD brains likely plays a role in PD pathogenesis, perhaps by causing cerebrovascular instability, under conditions of cellular stress.

Central Nervous System Pericytes Contribute to Health and Disease

Successful neuroprotection is only possible with contemporary microvascular protection. The prevention of disease-induced vascular modifications that accelerate brain damage remains largely elusive. An improved understanding of pericyte (PC) signalling could provide important insight into the function of the neurovascular unit (NVU), and into the injury-provoked responses that modify cell–cell interactions and crosstalk. Due to sharing the same basement membrane with endothelial cells, PCs have a crucial role in the control of endothelial, astrocyte, and oligodendrocyte precursor functions and hence blood–brain barrier stability. Both cerebrovascular and neurodegenerative diseases impair oxygen delivery and functionally impair the NVU. In this review, the role of PCs in central nervous system health and disease is discussed, considering their origin, multipotency, functions and also dysfunction, focusing on new possible avenues to modulate neuroprotection. Dysfunctional PC signalling could also be considered as a potential biomarker of NVU pathology, allowing us to individualize therapeutic interventions, monitor responses, or predict outcomes.

Brain Microvascular Pericytes—More than Bystanders in Breast Cancer Brain Metastasis

Brain tissue contains the highest number of perivascular pericytes compared to other organs. Pericytes are known to regulate brain perfusion and to play an important role within the neurovascular unit (NVU). The high phenotypic and functional plasticity of pericytes make this cell type a prime candidate to aid physiological adaptations but also propose pericytes as important modulators in diverse pathologies in the brain. This review highlights known phenotypes of pericytes in the brain, discusses the diverse markers for brain pericytes, and reviews current in vitro and in vivo experimental models to study pericyte function. Our current knowledge of pericyte phenotypes as it relates to metastatic growth patterns in breast cancer brain metastasis is presented as an example for the crosstalk between pericytes, endothelial cells, and metastatic cells. Future challenges lie in establishing methods for real-time monitoring of pericyte crosstalk to understand causal events in the brain metastatic process.

The Effect of Type-2 Diabetes on Cognitive Status and the Role of Anti-diabetes Medications

Type-2 diabetes mellitus prevalence is constantly increasing; this is explained by the increase of its risk factors and the amelioration of its management. Therefore, people are living longer with diabetes mellitus, which, in turn, has revealed new complications of the disease. Dementia is represented mainly by Alzheimer's disease and is an interesting topic of study. Accordingly, statistics have shown that dementia incidence is doubled in diabetic patients. The establishment of a relation between type-2 diabetes mellitus was studied on several levels in both humans and animal subjects. First, insulin receptors were found in the brain, especially the hippocampus, and insulin transport to the brain is mainly accomplished through the blood-brain barrier. Secondly, several studies showed that insulin affects multiple neurotransmitters in favor of promoting memory and cognition status. Thirdly, multiple pathological studies showed that insulin and Alzheimer's disease share many common lesions in the brain, such as beta-amyloid plaques, amylin-Aβ plaques, hyper-phosphorylated tau protein, and brain atrophy, especially in the hippocampus. After recognizing the positive effect of insulin on cognitive status, and the harmful effect of insulin resistance on cognitive status, multiple studies were focused on the role of anti-diabetes medications in fighting dementia. Consequently, these studies showed a positive impact of oral anti-diabetes medication, as well as insulin in limiting the progression of dementia and promoting cognitive status. Moreover, their effects were also noticed on limiting the pathological lesions of Alzheimer's disease. Accordingly, we can consider type-2 diabetes mellitus as a risk factor for dementia and Alzheimer's disease. Therefore, this can be used on the pharmaceutical level by the promising implication of antidiabetics as a treatment of dementia and Alzheimer's disease or at least to limit its progression. However, multiple clinical studies should be dedicated to proving the true benefits of anti-diabetes medications in treating dementia before they can be used in reality.

Neuroprotective effects of methylcobalamin in cerebral ischemia/reperfusion injury through activation of the ERK1/2 signaling pathway

Despite advances in the understanding of the pathophysiology of ischemic stroke, therapeutic options remain limited. Methylcobalamin is an endogenous vitamin B12 that exhibits anti-inflammatory and antiapoptotic activities in a variety of diseases. In this study, we aimed to explore the neuroprotective effects and mechanism of action of methylcobalamin on cerebral ischemic injury in vitro and in vivo. The oxygen and glucose deprivation/reperfusion model and middle cerebral artery occlusion model were used to simulate cerebral ischemic injury in vitro and in vivo. Cell viability, inflammatory factors, cell apoptosis, and protein expression levels were determined. Further, autophagy flux and the cerebral infarction volume were measured. The modified neurological severity score, Longa score, Rotarod assay, and foot-fault test were used to evaluate behavioral changes and neurological deficits in rats. In vitro, methylcobalamin significantly increased cell viability, decreased lactate dehydrogenase release, attenuated inflammatory cytokine expression, reduced the apoptotic proportion, and enhanced autophagy flux after OGD treatment. In addition, Bcl-2 and Beclin1 expression levels and the LC3 II/I ratio were increased, whereas levels of Bax and cleaved caspase-3 were decreased. In vivo, methylcobalamin significantly reduced the cerebral infarction volume and neurological deficits in the rats. Furthermore, methylcobalamin activated the ERK1/2 pathway, whereas ERK1/2 inhibitors diminished its effects in the in vitro and in vivo models. In conclusion, methylcobalamin may exert a neuroprotective effect on cerebral ischemia and is a promising drug candidate for developing novel neuroprotective therapies.

Biological and small molecule strategies in migraine therapy with relation to the calcitonin gene-related peptide family of peptides

Migraine is one of the most common of neurological disorders with a global prevalence of up to 15%. One in five migraineurs have frequent episodic or chronic migraine requiring prophylactic treatment. In recent years, specific pharmacological treatments targeting calcitonin gene-related peptide (CGRP) signalling molecules have provided safe and effective treatments, monoclonal antibodies for prophylaxis and gepants for acute therapy. Albeit beneficial, it is important to understand the molecular mechanisms of these new drugs to better understand migraine pathophysiology and improve therapy. Here, we describe current views on the role of the CGRP family of peptides - CGRP, calcitonin, adrenomedullin, amylin - and their receptors in the trigeminovascular system. All these molecules are present within the trigeminovascular system but differ in expression and localization. It is likely that they have different roles, which can be utilized in providing additional drug targets.

Amylin Dyshomeostasis Hypothesis: Small Vessel-Type Ischemic Stroke in the Setting of Type-2 Diabetes

Recent histological analyses of human brains show that small vessel-type injuries in the setting of type-2 diabetes colocalize with deposits of amylin, an amyloid-forming hormone secreted by the pancreas. Amylin inclusions are also identified in circulating red blood cells in people with type-2 diabetes and stroke or cardiovascular disease. In laboratory models of type-2 diabetes, accumulation of aggregated amylin in blood and the cerebral microvasculature induces brain microhemorrhages and reduces cerebral blood flow leading to white matter ischemia and neurological deficits. At the cellular level, aggregated amylin causes cell membrane lipid peroxidation injury, downregulation of tight junction proteins, and activation of proinflammatory signaling pathways which, in turn, induces macrophage activation and macrophage infiltration in vascular areas positive for amylin deposition. We review each step of this cascade based on experimental and clinical evidence and propose the hypothesis that systemic amylin dyshomeostasis may underlie the disparity between glycemic control and stroke risk and may be a therapeutic target to reduce the risk of small vessel ischemic stroke in patients with type-2 diabetes.

Amylin antibodies frequently display cross-reactivity with CGRP: characterization of eight amylin antibodies

Amylin is a 37-amino acid endocrine hormone secreted from the pancreas in response to nutrient intake, acting centrally to promote meal-ending satiation. With many studies linking amylin action to the nervous system, determining the distribution or expression of amylin in the nervous system is critical. However, amylin shares sequence identity and structural homology to the related neuropeptide calcitonin gene-related peptide (CGRP). This creates challenges in identifying selective amylin antibodies that do not cross-react with CGRP, especially in neural tissues, where CGRP is densely packed into secretory vesicles. Here, we characterized eight amylin antibodies to determine their ability to detect amylin and cross-react with rat or human αCGRP, using immunoblots and preabsorption controls in rat pancreas. We observed that amylin antibodies frequently cross-reacted with αCGRP and are therefore not suitable for use in tissues that highly express CGRP. Earlier work using these antibodies should be revisited in light of our findings.

Temporal dynamics of cells expressing NG2 and platelet-derived growth factor receptor-β in the fibrotic scar formation after 3-nitropropionic acid-induced acute brain injury

Neuron-glia antigen 2 (NG2) proteoglycan and platelet-derived growth factor receptor beta (PDGFR-β) are widely used markers of pericytes, which are considered cells that form fibrotic scars in response to central nervous system insults. However, the exact phenotypes of NG2- and PDGFR-β-expressing cells, as well as the origin of the fibrotic scar after central nervous system insults, are still elusive. In the present study, we directly examined the identities and distributions of NG2- and PDGFR-β-positive cells in the control and lesioned striatum injured by the mitochondrial toxin 3-nitropropionic acid. Immunoelectron microscopy and correlative light and electron microscopy clearly distinguished NG2 and PDGFR-β expression in the vasculature during the post-injury period. Vascular smooth muscle cells and pericytes expressed NG2, which was prominently increased after the injury. NG2 expression was restricted to these vascular mural cells until 14 days post-lesion. By contrast, PDGFR-β-positive cells were perivascular fibroblasts located abluminal to smooth muscle cells or pericytes. These PDGFR-β-expressing cells formed extravascular networks associated with collagen fibrils at 14 days post-lesion. We also found that in the injured striatal parenchyma, PDGFR-β could be used as a complementary marker of resting and reactive NG2 glia because activated microglia/macrophages shared only the NG2 expression with NG2 glia in the lesioned striatum. These data indicate that NG2 and PDGFR-β label different vascular mural and parenchymal cells in the healthy and injured brain, suggesting that fibrotic scar-forming cells most likely originate in PDGFR-β-positive perivascular fibroblasts rather than in NG2-positive pericytes.

Traditional Chinese Medicine Shenmayizhi Decoction Ameliorates Memory and Cognitive Impairment Induced by Multiple Cerebral Infarctions

This study aimed to illustrate the mechanism by which Shenmayizhi decoction (SMYZD) improves the learning memory of rats with vascular cognitive impairment (VCI). Fifty male and female Wistar rats of specific pathogen-free grade (SPF grade) were used to establish the model by the administration of a microsphere embolization. This was accomplished by injecting sterile, standardized, mass-produced microspheres of uniform particle size (100–200 µm in diameter) in a sodium alginate microsphere vascular embolic agent suspension to induce VCI. The VCI model was successfully established in 40 rats, including both male and female rats, and the rats were randomly divided into 4 groups of 10 rats each. The model group was administered an equal volume of distilled water. The donepezil group was administered 0.45 mg/kg/d donepezil, which is equivalent to the clinical dosage. The SMYZ-H group was administered 11.88 g/kg/d SMYZ, which is 4 times higher than the clinically equivalent dosage. The SMYZ-L group was administered 2.97 g/kg/d SMYZ, which is the clinically equivalent dosage. A sham-operated group was used as the control group and administered an equal volume of distilled water. The rats in the 4 groups were treated by gavage with equal volumes of liquid and the indicated concentration of drug diluted in distilled water for 8 consecutive weeks. Two months later, the Morris water maze (MWM) was used to evaluate the spatial memory of all the rats. Ultrastructural and ultrapathological changes in the capillaries of the cerebral cortex were observed by transmission electron microscopy. Furthermore, Western blot and RT-PCR analyses were used to assess the levels of platelet-derived growth factor receptor-β (PDGFR-β), neuron-glial antigen 2 (NG2), vascular endothelial growth factor A (VEGF-A), and angiopoietin 1 (Ang1) in the cerebral cortex of the rats. The results showed that SMYZD at concentrations of 11.88 g/kg/d and 2.97 g/kg/d (SMYZ-H and SMYZ-L) significantly shortened the escape latency (EL). In addition, SMYZ-H significantly prolonged the distance traveled and the time spent in the original platform quadrant by the rats with VCI. SMYZ-H significantly increased the NG2 and Ang1 protein expression levels and increased the PDGFR-β and Ang1 mRNA levels. These results demonstrated that Shenmayizhi decoction can improve the memory abilities of rats with VCI induced by multiple cerebral infarctions by preventing pericyte degeneration.

Neural crest cell-derived pericytes act as pro-angiogenic cells in human neocortex development and gliomas

Central nervous system diseases involving the parenchymal microvessels are frequently associated with a ‘microvasculopathy’, which includes different levels of neurovascular unit (NVU) dysfunction, including blood–brain barrier alterations. To contribute to the understanding of NVU responses to pathological noxae, we have focused on one of its cellular components, the microvascular pericytes, highlighting unique features of brain pericytes with the aid of the analyses carried out during vascularization of human developing neocortex and in human gliomas. Thanks to their position, centred within the endothelial/glial partition of the vessel basal lamina and therefore inserted between endothelial cells and the perivascular and vessel-associated components (astrocytes, oligodendrocyte precursor cells (OPCs)/NG2-glia, microglia, macrophages, nerve terminals), pericytes fulfil a central role within the microvessel NVU. Indeed, at this critical site, pericytes have a number of direct and extracellular matrix molecule- and soluble factor-mediated functions, displaying marked phenotypical and functional heterogeneity and carrying out multitasking services. This pericytes heterogeneity is primarily linked to their position in specific tissue and organ microenvironments and, most importantly, to their ontogeny. During ontogenesis, pericyte subtypes belong to two main embryonic germ layers, mesoderm and (neuro)ectoderm, and are therefore expected to be found in organs ontogenetically different, nonetheless, pericytes of different origin may converge and colonize neighbouring areas of the same organ/apparatus. Here, we provide a brief overview of the unusual roles played by forebrain pericytes in the processes of angiogenesis and barriergenesis by virtue of their origin from midbrain neural crest stem cells. A better knowledge of the ontogenetic subpopulations may support the understanding of specific interactions and mechanisms involved in pericyte function/dysfunction, including normal and pathological angiogenesis, thereby offering an alternative perspective on cell subtype-specific therapeutic approaches.

Neural crest cell-derived pericytes act as pro-angiogenic cells in human neocortex development and gliomas

Central nervous system diseases involving the parenchymal microvessels are frequently associated with a ‘microvasculopathy’, which includes different levels of neurovascular unit (NVU) dysfunction, including blood–brain barrier alterations. To contribute to the understanding of NVU responses to pathological noxae, we have focused on one of its cellular components, the microvascular pericytes, highlighting unique features of brain pericytes with the aid of the analyses carried out during vascularization of human developing neocortex and in human gliomas. Thanks to their position, centred within the endothelial/glial partition of the vessel basal lamina and therefore inserted between endothelial cells and the perivascular and vessel-associated components (astrocytes, oligodendrocyte precursor cells (OPCs)/NG2-glia, microglia, macrophages, nerve terminals), pericytes fulfil a central role within the microvessel NVU. Indeed, at this critical site, pericytes have a number of direct and extracellular matrix molecule- and soluble factor-mediated functions, displaying marked phenotypical and functional heterogeneity and carrying out multitasking services. This pericytes heterogeneity is primarily linked to their position in specific tissue and organ microenvironments and, most importantly, to their ontogeny. During ontogenesis, pericyte subtypes belong to two main embryonic germ layers, mesoderm and (neuro)ectoderm, and are therefore expected to be found in organs ontogenetically different, nonetheless, pericytes of different origin may converge and colonize neighbouring areas of the same organ/apparatus. Here, we provide a brief overview of the unusual roles played by forebrain pericytes in the processes of angiogenesis and barriergenesis by virtue of their origin from midbrain neural crest stem cells. A better knowledge of the ontogenetic subpopulations may support the understanding of specific interactions and mechanisms involved in pericyte function/dysfunction, including normal and pathological angiogenesis, thereby offering an alternative perspective on cell subtype-specific therapeutic approaches.

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.

An updated review of autophagy in ischemic stroke: From mechanisms to therapies

Stroke is a leading cause of mortality and morbidity worldwide. Understanding the underlying mechanisms is important for developing effective therapies for treating stroke. Autophagy is a self-eating cellular catabolic pathway, which plays a crucial homeostatic role in the regulation of cell survival. Increasing evidence shows that autophagy, observed in various cell types, plays a critical role in brain pathology after ischemic stroke. Therefore, the regulation of autophagy can be a potential target for ischemic stroke treatment. In the present review, we summarize the recent progress that research has made regarding autophagy and ischemic stroke, including common signaling pathways, the role of autophagic subtypes (e.g. mitophagy, pexophagy, aggrephagy, endoplasmic reticulum-phagy, and lipophagy) in ischemic stroke, as well as the current methods for autophagy detection and potential therapeutic strategy.

Amylin deposition activates HIF1α and 6-phosphofructo-2-kinase/fructose-2, 6-biphosphatase 3 (PFKFB3) signaling in failing hearts of non-human primates

Hyperamylinemia induces amylin aggregation and toxicity in the pancreas and contributes to the development of type-2 diabetes (T2D). Cardiac amylin deposition in patients with obesity and T2D was found to accelerate heart dysfunction. Non-human primates (NHPs) have similar genetic, metabolic, and cardiovascular processes as humans. However, the underlying mechanisms of cardiac amylin in NHPs, particularly related to the hypoxia inducible factor (HIF)1α and 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 (PFKFB3) signaling pathways, are unknown. Here, we demonstrate that in NHPs, amylin deposition in heart failure (HF) contributes to cardiac dysfunction via activation of HIF1α and PFKFB3 signaling. This was confirmed in two in vitro cardiomyocyte models. Furthermore, alterations of intracellular Ca2+, reactive oxygen species, mitochondrial function, and lactate levels were observed in amylin-treated cells. Our study demonstrates a pathological role for amylin in the activation of HIF1α and PFKFB3 signaling in NHPs with HF, establishing amylin as a promising target for heart disease patients.

Multifaceted roles of pericytes in central nervous system homeostasis and disease

Pericytes, the mural cells surrounding microcirculation, are gaining increasing attention for their roles in health and disease of the central nervous system (CNS). As an essential part of the neurovascular unit (NVU), pericytes are actively engaged in interactions with neighboring cells and work in synergy with them to maintain homeostasis of the CNS, such as maintaining the blood-brain barrier (BBB), regulating cerebral blood flow (CBF) and the glymphatic system as well as mediating immune responses. However, the dysfunction of pericytes may contribute to the progression of various pathologies. In this review, we discuss: (1) origin of pericytes and different pericyte markers; (2) interactions of pericytes with endothelial cells (ECs), astrocytes, microglia, oligodendrocytes, and neurons; (3) physiological roles of pericytes in the CNS; (4) effects of pericytes in different CNS diseases; (5) relationship of pericytes with extracellular vesicles (EVs) and microRNAs (miRs); (6) recent advances in pericytes studies and future perspective.

Proteotoxicity and mitochondrial dynamics in aging diabetic brain

Impaired neuronal proteostasis is a salient feature of both aging and protein misfolding disorders. Amyloidosis, a consequence of this phenomena is observed in the brains of diabetic patients over the chronic time period. These toxic aggregates not only cause age-related decline in proteostasis, but also dwindle its ability to increase or restore the chaperones in response to any stressful condition. Mitochondria acts as the main source of energy regulation and many metabolic disorders such as diabetes have been associated with altered oxidative phosphorylation (OxPhos) and redox imbalance in the mitochondria. The mitochondrial unfolded protein response (UPR^mt) acts as a mediator for maintaining the mitochondrial protein homeostasis and quality control during such conditions. Over a long time period, these responses start shutting off leading to proteotoxic stress in the neurons. This reduces the buffering capacity of protein network signalling during aging, thereby increasing the risk of neurodegeneration in the brain. In this review, we focus on the proteotoxic stress that occurs as an amalgamation of diabetes and aging, as well as the impact of mitochondrial dysfunction on the neuronal survival affecting the diabetic brain and its long term consequences on the memory changes.

Brain Microvascular Pericytes in Vascular Cognitive Impairment and Dementia

Pericytes are unique, multi-functional mural cells localized at the abluminal side of the perivascular space in microvessels. Originally discovered in 19th century, pericytes had drawn less attention until decades ago mainly due to lack of specific markers. Recently, however, a growing body of evidence has revealed that pericytes play various important roles: development and maintenance of blood–brain barrier (BBB), regulation of the neurovascular system (e.g., vascular stability, vessel formation, cerebral blood flow, etc.), trafficking of inflammatory cells, clearance of toxic waste products from the brain, and acquisition of stem cell-like properties. In the neurovascular unit, pericytes perform these functions through coordinated crosstalk with neighboring cells including endothelial, glial, and neuronal cells. Dysfunction of pericytes contribute to a wide variety of diseases that lead to cognitive impairments such as cerebral small vessel disease (SVD), acute stroke, Alzheimer’s disease (AD), and other neurological disorders. For instance, in SVDs, pericyte degeneration leads to microvessel instability and demyelination while in stroke, pericyte constriction after ischemia causes a no-reflow phenomenon in brain capillaries. In AD, which shares some common risk factors with vascular dementia, reduction in pericyte coverage and subsequent microvascular impairments are observed in association with white matter attenuation and contribute to impaired cognition. Pericyte loss causes BBB-breakdown, which stagnates amyloid β clearance and the leakage of neurotoxic molecules into the brain parenchyma. In this review, we first summarize the characteristics of brain microvessel pericytes, and their roles in the central nervous system. Then, we focus on how dysfunctional pericytes contribute to the pathogenesis of vascular cognitive impairment including cerebral ‘small vessel’ and ‘large vessel’ diseases, as well as AD. Finally, we discuss therapeutic implications for these disorders by targeting pericytes.

Expression of the CGRP Family of Neuropeptides and their Receptors in the Trigeminal Ganglion

The calcitonin gene-related peptide (CGRP) family of neuropeptides, consists of CGRP, adrenomedullin, amylin, and calcitonin. The receptors consist of either calcitonin receptor-like receptor (CLR) or calcitonin receptor (CTR) which for function needs an accessory protein, receptor activity-modifying proteins (RAMPs). CGRP has a pivotal role in primary headaches but the role of the other members of the CGRP family of peptides in headaches is not known. Here, we describe the expression of these molecules in the trigeminal ganglion (TG) to understand more on their possible role(s). Single or double immunohistochemistry were applied on frozen sections of rat TG using primary antibodies against CGRP, procalcitonin, calcitonin, adrenomedullin, amylin, RAMP1/2/3, CLR, and CTR. In addition, mRNA expression was measured by quantitative qPCR on TGs. CGRP and calcitonin showed rich expression in the cytoplasm of small to medium-sized neurons, and co-localized sometimes. Procalcitonin was observed in the glial cells. Immunoreactive fibers storing both CGRP and calcitonin were also observed. Adrenomedullin immunoreactivity was found in the satellite glial cells and in fibers, probably the myelinating Schwann cells. Amylin was found in the cytoplasm in many TG neurons. Levels of mRNA expression for adrenomedullin, amylin, CLR, RAMP1, RAMP2, RAMP3, and CTR were measured using qPCR. The experiments verified the expression of mRNA in the TG with the exception of CTR, which was above the limit of detection indicating little or no mRNA expression. In addition to the well-known CGRP receptor (CLR/RAMP1) and the receptor for calcitonin—CTR, we propose that other receptors exist in the rat TG: adrenomedullin receptor AM₂ (CLR/RAMP3) in mainly the satellite glial cells, amylin receptors AMY₁ (CTR/RAMP1) in mainly neurons, and AMY₃ (CTR/RAMP3) in the satellite glial cells. It is important to compare peptides and receptors side-by-side in studies to help address questions of actions resulting from cross-reactivity between receptors. Several of the diverse biological actions of the CGRP family of peptides are clinically relevant. Our findings demonstrate the specific ligand and receptor sites in the rat trigeminal ganglion, highlighting recognition mechanisms to facilitate drug development.

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-β peptide (Aβ), 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.

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.

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.

Diabetes-related Amylin Dyshomeostasis: a Contributing Factor to Cerebrovascular Pathology and Dementia

Type 2 diabetes (T2D) increases the risk for cerebrovascular disease (CVD) and dementia. The underlying molecular mechanisms remain elusive, which hampers the development of treatment or/and effective prevention strategies. Recent studies suggest that dyshomeostasis of amylin, a satiety hormone that forms pancreatic amyloid in patients with T2D, promotes accumulation of amylin in cerebral small blood vessels and interaction with Alzheimer's disease (AD) pathology. Overexpression of human amylin in rodents (rodent amylin does not form amyloid) leads to late-life onset T2D and neurologic deficits. In this Review, we discuss clinical evidence of amylin pathology in CVD and AD and identify critical characteristics of animal models that could help to better understand molecular mechanisms underlying the increased risk of CVD and AD in patients with prediabetes or T2D.

The role of pericytes in brain disorders: from the periphery to the brain

It is becoming increasingly apparent that disorders of the brain microvasculature contribute to many neurological disorders. In recent years it has become clear that a major player in these events is the capillary pericyte which, in the brain, is now known to control the blood-brain barrier, regulate blood flow, influence immune cell entry and be crucial for angiogenesis. In this review we consider the under-explored possibility that peripheral diseases which affect the microvasculature, such as hypertension, kidney disease and diabetes, produce central nervous system (CNS) dysfunction by mechanisms affecting capillary pericytes within the CNS. We highlight how cellular messengers produced peripherally can act via signalling pathways within CNS pericytes to reshape blood vessels, restrict blood flow or compromise blood-brain barrier function, thus causing neuronal dysfunction. Increased understanding of how renin-angiotensin, Rho-kinase and PDGFRβ signalling affect CNS pericytes may suggest novel therapeutic approaches to reducing the CNS effects of peripheral disorders.

Levels of islet amyloid polypeptide in cerebrospinal fluid and plasma from patients with Alzheimer's disease

The biologically active pancreatic hormone peptide islet amyloid polypeptide (IAPP) regulates brain functions such as appetite and cognition. It also plays a role in clearance of amyloid beta (Aβ), a peptide implicated in the dementia disorder Alzheimer’s disease (AD). If IAPP becomes modified, it loses its biological activity and starts to aggregate. Such aggregations have been found in the AD brain and decreased plasma levels of the unmodified IAPP (uIAPP) have been shown in the same patients. In the current study, we analyze levels of uIAPP and total IAPP (unmodified and modified) in cerebrospinal fluid (CSF) to investigate its potential as a biomarker for AD. We found no differences in neither CSF nor plasma levels of uIAPP or total IAPP in AD patients compared to cognitive healthy individuals (NC). The levels of uIAPP in CSF of NC were positively correlated with uIAPP in plasma, Q-albumin and albumin levels in CSF, but negatively correlated with CSF levels of t-tau and p-tau. These findings were not seen in AD patients. Levels of total CSF IAPP correlated positively with total Q-albumin and albumin levels in CSF in both AD and NC. In addition, total plasma IAPP correlated positively with CSF t-tau and p-tau in NC and negatively with CSF Aβ₄₂ in AD patients. To conclude, our studies did not find evidence supporting the use of CSF IAPP as an AD biomarker. However, our findings, indicating a compromised translocation of uIAPP in and out of the brain in AD patients as well as the correlations between total plasma IAPP and AD biomarkers, encourage further research on the role for IAPP in AD.

The Role of Autophagy in Acute Myocardial Infarction

Acute myocardial infarction refers to a sudden death of cardiomyocytes, which leads to a large mortality worldwide. To attenuate acute myocardial infarction, strategies should be made to increase cardiomyocyte survival, improve postinfarcted cardiac function, and reverse the process of cardiac remodeling. Autophagy, a pivotal cellular response, has been widely studied and is known to be involved in various kinds of diseases. In the recent few years, the role of autophagy in diseases has been drawn increasing attention to by researchers. Here in this review, we mainly focus on the discussion of the effect of autophagy on the pathogenesis and progression of acute myocardial infarction under ischemic and ischemia/reperfusion injuries. Furthermore, several popular therapeutic agents and strategies taking advantage of autophagy will be described.

Cognitive decline and dementia in diabetes mellitus: mechanisms and clinical implications

Cognitive dysfunction is increasingly recognized as an important comorbidity of diabetes mellitus. Different stages of diabetes-associated cognitive dysfunction exist, each with different cognitive features, affected age groups and prognoses and probably with different underlying mechanisms. Relatively subtle, slowly progressive cognitive decrements occur in all age groups. More severe stages, particularly mild cognitive impairment and dementia, with progressive deficits, occur primarily in older individuals (>65 years of age). Patients in the latter group are the most relevant for patient management and are the focus of this Review. Here, we review the evolving insights from studies on risk factors, brain imaging and neuropathology, which provide important clues on mechanisms of both the subtle cognitive decrements and the more severe stages of cognitive dysfunction. In the majority of patients, the cognitive phenotype is probably defined by multiple aetiologies. Although both the risk of clinically diagnosed Alzheimer disease and that of vascular dementia is increased in association with diabetes, the cerebral burden of the prototypical pathologies of Alzheimer disease (such as neurofibrillary tangles and neuritic plaques) is not. A major challenge for researchers is to pinpoint from the spectrum of diabetes-related disease processes those that affect the brain and contribute to development of dementia beyond the pathologies of Alzheimer disease. Observations from experimental models can help to meet that challenge, but this requires further improving the synergy between experimental and clinical scientists. The development of targeted treatment and preventive strategies will therefore depend on these translational efforts.

Review: Relationship of type 2 diabetes to human brain pathology

Type 2 diabetes (T2D) and Alzheimer's disease (AD) are both highly prevalent diseases worldwide, and each is associated with high-morbidity and high-mortality. Numerous clinical studies have consistently shown that T2D confers a two-fold increased risk for a dementia, including dementia attributable to AD. Yet, the mechanisms underlying this relationship, especially nonvascular mechanisms, remain debated. Cerebral vascular disease (CVD) is likely to be playing a role. But increased AD neuropathologic changes (ADNC), specifically neuritic amyloid plaques (AP) and neurofibrillary tangles (NFT), are also posited mechanisms. The clinicopathological studies to date demonstrate T2D to be consistently associated with infarcts, particularly subcortical lacunar infarcts, but not ADNC, suggesting the association of T2D with dementia may largely be mediated through CVD. Furthermore, growing interest exists in insulin resistance (IR), particularly IR within the brain itself, which may be an associated but distinct phenomenon from T2D, and possibly itself associated with ADNC. Other mechanisms largely related to protein processing and efflux in the central nervous system with altered function in T2D may also be involved. Such mechanisms include islet amyloid polypeptide (or amylin) deposition, co-localized with beta-amyloid and found in more abundance in the AD temporal cortex, blood-brain barrier breakdown and dysfunction, potentially related to pericyte degeneration, and disturbance of brain lymphatics, both in the glial lymphatic system and the newly discovered discrete central nervous system lymph vessels. Medical research is ongoing to further disentangle the relationship of T2D to dementia in the ageing human brain.

Levels of retinal IAPP are altered in Alzheimer's disease patients and correlate with vascular changes and hippocampal IAPP levels

Islet amyloid polypeptide (IAPP) forms toxic aggregates in the brain of patients with Alzheimer's disease (AD). Whether IAPP also affects the retina in these patients is still unknown. Levels of IAPP in soluble and insoluble homogenate fractions of retina and hippocampus from AD patients and nondemented controls were analyzed using ELISA. Number of pericytes and vessel length were determined by analysis of immunostained retina and hippocampus. Insoluble retinal fractions of AD patients contained lower levels of unmodified IAPP, whereas soluble retinal fractions contained increased levels of the same. Total IAPP levels and pericyte numbers in retina mirrored corresponding variables in the hippocampus. Moreover, levels of total unmodified IAPP correlated negatively with the vessel length both in retina and hippocampus across the group and positively with pericyte numbers in retina in AD patients. Our studies indicate that changes in brain IAPP are reflected by corresponding levels in the retina. Our results also suggest modification of IAPP as an important event implicated in vascular changes associated with AD.