Amylin receptor: a common pathophysiological target in Alzheimer's disease and diabetes mellitus

Structural Analysis of Amylin and Amyloid β Peptide Signaling in Alzheimer's Disease

Amylin and amyloid β belong to the same protein family and activate the same receptors. Amyloid β levels are elevated in Alzheimer's disease. Recent studies have demonstrated that amylin-based peptides can reduce the symptoms of Alzheimer's disease in animal models. Replica exchange molecular dynamics simulation machine learning, as well as other computational analyses, were applied to improve the understanding of the amino acid residues in these amylin-based peptides. Comparisons were made between amylin, amylin-based peptides, and amyloid β. These studies converged on amylin residues 10Q, 28S, 29S, 30T, 31N, 32V, 33G, 34S, and 35N (residues 10 and 28-35) being ranked highest, meaning that they were the most likely to be involved in activating the same targets as amyloid β. Surprisingly, the amyloid β signaling domain most closely matched amylin residues 29-35 in the simulated structures. These findings suggest important residues that are structurally similar between amylin and amyloid β and are thus implicated in the activation of the amylin receptor.

Updates in pharmacotherapy of obesity

Obesity is now recognized as a chronic, progressive condition requiring early intervention and long-term management to achieve health benefits and improve metabolic risk factors. The main objective of obesity pharmacotherapy is weight loss and weight loss maintenance. There is increasing acceptance of anti-obesity medications as an adjunct to lifestyle modifications and/or surgery. In recent years there has been an evolution in management approach and pharmacologic options for treatment. As a result, there is increased focus on the efficacy and safety of these agents. We provide a historical perspective, review of recent studies on anti-obesity medication outcomes showing efficacy, potential side effects and promising therapies in development.

Investigating CR1 as an indicated Gene for mild cognitive impairment in type 2 diabetes mellitus

OBJECTIVE

Type 2 diabetes mellitus (T2DM) has beenis known as an important risk factor for cognitive impairment. Meanwhile, the liver plays a central role in the development of T2DM and insulin resistance. The present study attempted to identify and validate marker genes for mild cognitive impairment (MCI) in patients with T2DM.

METHODS

In this study, insulin resistance-related differentially expressed genes were identified from the liver tissues of individuals with T2DM and those with normal glucose tolerance using the Gene Expression Omnibus database and MCI-associated genes were identified using the GeneCards database. Next, enrichment analysis was performed with overlapping T2DM and MCI genes, followed by the identification of specific genes using the LASSO logistic regression and SVM-RFE algorithms. An important experiment involved the implementation of clinical and in vitro validation using real-time quantitative polymerase chain reaction (RT-qPCR). Finally, multiple linear regression, binary logistic regression, and receiver operating characteristic curve analyses were performed to investigate the relationship between the key gene and cognitive function in these patients.

RESULT

The present study identified 40 overlapping genes between MCI and T2DM, with subsequent enrichment analysis revealing their significant association with the roles of neuronal and glial projections. The marker gene complement receptor 1(CR1) was identified for both diseases using two regression algorithms. Based on RT-qPCR validation in 65 T2DM patients with MCI (MCI group) and 65 T2DM patients without MCI (NC group), a significant upregulation of CR1 mRNA in peripheral blood mononuclear cells was observed in the MCI group (P < 0.001). Furthermore, the CR1 gene level was significantly negatively associated with MoCA and MMSE scores, which reflect the overall cognitive function, and positively correlated with TMTB scores, which indicate the executive function. Finally, elevated CR1 mRNA levels were identified as an independent risk factor for MCI (OR = 1.481, P < 0.001).

CONCLUSION

These findings suggest that CR1 is an important predictor of MCI in patients with T2DM. Thus, CR1 has potential clinical significance, which may offer new ideas and directions for the management and treatment of T2DM. The identification and clinical validation of dysregulated marker genes in both T2DM and MCI can offer valuable insights into the intrinsic association between these two conditions. The current study insights may inspire the development of novel strategies for addressing the complicated issues related to cognitive impairment associated with diabetes.

Amylin, Another Important Neuroendocrine Hormone for the Treatment of Diabesity

Diabetes mellitus is a devastating chronic metabolic disease. Since the majority of type 2 diabetes mellitus patients are overweight or obese, a novel term-diabesity-has emerged. The gut-brain axis plays a critical function in maintaining glucose and energy homeostasis and involves a variety of peptides. Amylin is a neuroendocrine anorexigenic polypeptide hormone, which is co-secreted with insulin from β-cells of the pancreas in response to food consumption. Aside from its effect on glucose homeostasis, amylin inhibits homeostatic and hedonic feeding, induces satiety, and decreases body weight. In this narrative review, we summarized the current evidence and ongoing studies on the mechanism of action, clinical pharmacology, and applications of amylin and its analogs, pramlintide and cagrilintide, in the field of diabetology, endocrinology, and metabolism disorders, such as obesity.

Amylin receptor agonism enhances the effects of liraglutide in protecting against the acute metabolic side effects of olanzapine

Olanzapine is a second-generation antipsychotic (AP) used in the management of schizophrenia. Although effective at reducing psychoses, APs cause rapid hyperglycemia, insulin resistance, and dyslipidemia, an effect mediated in part by glucagon. We tested if amylin, a hormone that reduces glucagon, or the amylin receptor agonist pramlintide would protect against acute olanzapine-induced impairments in glucose and lipid homeostasis alone or in combination with other glucose-lowering agents such as liraglutide. We demonstrated that pramlintide lowered olanzapine-induced increases in glucagon:insulin ratio with a trend to protect against excursions in blood glucose. There was an additive effect of pramlintide and liraglutide in protecting against olanzapine-induced hyperglycemia, which was mirrored by reductions in glucagon and attenuated markers of dyslipidemia. Our findings provide evidence that pramlintide, although moderately protective against some aspects of olanzapine-induced metabolic dysfunction, can be used to enhance the protective effects of other interventions against acute olanzapine-induced metabolic dysfunction.

Novel Amylin Analogues Reduce Amyloid-β Cross-Seeding Aggregation and Neurotoxicity

BACKGROUND

Type 2 diabetes related human islet amyloid polypeptide (hIAPP) plays a dual role in Alzheimer's disease (AD). hIAPP has neuroprotective effects in AD mouse models whereas, high hIAPP concentrations can promote co-aggregation with amyloid-β (Aβ) to promote neurodegeneration. In fact, both low and high plasma hIAPP concentration has been associated with AD. Therefore, non-aggregating hIAPP analogues have garnered interest as a treatment for AD. The aromatic amino acids F23 and I26 in hIAPP have been identified as the key residues involved in self-aggregation and Aβ cross-seeding.

OBJECTIVE

Three novel IAPP analogues with single and double alanine mutations (A1 = F23, A2 = I26, and A3 = F23 + I26) were assessed for their ability to aggregate, modulate Aβ oligomer formation, and alter neurotoxicity.

METHODS

A range of biophysical methods including Thioflavin-T, gel electrophoresis, photo-crosslinking, circular dichroism combined with cell viability assays were utilized to assess protein aggregation and toxicity.

RESULTS

All IAPP analogues showed significantly less self-aggregation than hIAPP. Co-aggregated Aβ 42-A2 and A3 also showed reduced aggregation compared to Aβ 42-hIAPP mixtures. Self- and co-oligomerized A1, A2, and A3 exhibited random coil conformations with reduced beta sheet content compared to hIAPP and Aβ 42-hIAPP aggregates. A1 was toxic at high concentrations compared to A2 and A3. However, co-aggregated Aβ 42-A1, A2, or A3 showed reduced neurotoxicity compared to Aβ 42, hIAPP, and Aβ 42-hIAPP aggregates.

CONCLUSION

These findings confirm that hIAPP analogues with non-aromatic residues at positions 23 and 26 have reduced self-aggregation and the ability to neutralize Aβ 42 toxicity. This warrants further characterization of their protective effects in pre-clinical AD models.

Role of Receptors in Relation to Plaques and Tangles in Alzheimer's Disease Pathology

Despite the identification of Aβ plaques and NFTs as biomarkers for Alzheimer’s disease (AD) pathology, therapeutic interventions remain elusive, with neither an absolute prophylactic nor a curative medication available to impede the progression of AD presently available. Current approaches focus on symptomatic treatments to maintain AD patients’ mental stability and behavioral symptoms by decreasing neuronal degeneration; however, the complexity of AD pathology requires a wide range of therapeutic approaches for both preventive and curative treatments. In this regard, this review summarizes the role of receptors as a potential target for treating AD and focuses on the path of major receptors which are responsible for AD progression. This review gives an overall idea centering on major receptors, their agonist and antagonist and future prospects of viral mimicry in AD pathology. This article aims to provide researchers and developers a comprehensive idea about the different receptors involved in AD pathogenesis that may lead to finding a new therapeutic strategy to treat AD.

The Fight Against Obesity Escalates: New Drugs on the Horizon and Metabolic Implications

PURPOSE OF REVIEW

There is currently a steep rise in the global prevalence of obesity. Pharmaceutical therapy is a valuable component of conservative obesity therapy. Herein, medications currently in the phase of preclinical or clinical testing are reviewed, along with an overview of the mechanisms that regulate energy intake and expenditure. In addition, the current and potential future directions of obesity drug therapy are discussed.

RECENT FINDINGS

Although the current arsenal of obesity pharmacotherapy is limited, a considerable number of agents that exert their actions through a variety of pharmacodynamic targets and mechanisms are in the pipeline. This expansion shapes a potential near future of obesity conservative management, characterized by tailored combined therapeutic regimens, targeting not only weight loss but also improved overall health outcomes. The progress regarding the elucidation of the mechanisms which regulate the bodily energy equilibrium has led to medications which mimic hormonal adaptations that follow bariatric surgery, in the quest for a "Medical bypass." These, combined with agents which could increase energy expenditure, point to a brilliant future in the conservative treatment of obesity.

Amylin and pramlintide modulate γ-secretase level and APP processing in lipid rafts

A major characteristic of Alzheimer's disease (AD) is the accumulation of misfolded amyloid-β (Aβ) peptide. Several studies linked AD with type 2 diabetes due to similarities between Aβ and human amylin. This study investigates the effect of amylin and pramlintide on Aβ pathogenesis and the predisposing molecular mechanism(s) behind the observed effects in TgSwDI mouse, a cerebral amyloid angiopathy (CAA) and AD model. Our findings showed that thirty days of intraperitoneal injection with amylin or pramlintide increased Aβ burden in mice brains. Mechanistic studies revealed both peptides altered the amyloidogenic pathway and increased Aβ production by modulating amyloid precursor protein (APP) and γ-secretase levels in lipid rafts. In addition, both peptides increased levels of B4GALNT1 enzyme and GM1 ganglioside, and only pramlintide increased the level of GM2 ganglioside. Increased levels of GM1 and GM2 gangliosides play an important role in regulating amyloidogenic pathway proteins in lipid rafts. Increased brain Aβ burden by amylin and pramlintide was associated with synaptic loss, apoptosis, and microglia activation. In conclusion, our findings showed amylin or pramlintide increase Aβ levels and related pathology in TgSwDI mice brains, and suggest that increased amylin levels or the therapeutic use of pramlintide could increase the risk of AD.

Neuroprotective Effects of Amylin Analogues on Alzheimer's Disease Pathogenesis and Cognition

Type II diabetes (T2D) has been identified as a major risk factor for the development of Alzheimer's disease (AD). Interestingly, both AD and T2D have similar characteristics including amyloid peptide aggregation, decreased metabolism, and increased oxidative stress and inflammation. Despite their prevalence, therapies for these diseases are limited. To date, most therapies for AD have targeted amyloid-β or tau. Unfortunately, most of these clinical trials have been largely unsuccessful, creating a crucial need for novel therapies. A number of studies have shown that metabolic hormone therapies are effective at ameliorating high blood glucose levels in diabetics as well as improving cognitive function in AD and mild cognitive impairment patients. Pramlintide, a synthetic analogue of the pancreatic hormone amylin, has been developed and used for years now as a treatment for both type I diabetes and T2D due to the loss of β-islet cells responsible for producing amylin. Importantly, recent data demonstrates its potential therapeutic role for AD as well. This review aims at addressing parallels between T2D and AD at a pathological and functional level, focusing on amylin signaling as a key, overlapping mediator in both diseases. The potential therapeutic use of this hormone to treat AD will also be explored from a mechanistic viewpoint.

Amyloid Pan-inhibitors: One Family of Compounds To Cope with All Conformational Diseases

Amyloids are ubiquitous protein aggregates sharing common internal structural features; they are present in all organisms, from prokaryotes to eukaryotes, where they play physiological or pathological roles. Importantly, amyloids, which are generated by aggregation of a range of distinct proteins, could be a key factor in a number of major human disorders, the so-called conformational diseases. Because all amyloids exhibit similar cross-β motifs, one may envisage that molecules capable of blocking the formation of β-sheet structures could abolish aggregation of all amyloid proteins, albeit with different efficacies. Herein, two different β-sheet blockers were tested against a selection of amyloidogenic proteins, encompassing all the major types of amyloid-based disorders. Analysis of their blocking efficiency, using a simple but contrasted cell-based screening procedure, unequivocally confirms that they indeed behave as aggregation pan-inhibitors. The significant inhibitory effects observed for these compounds against all tested amyloidogenic proteins could spur a broader biological evaluation of other known and new amyloid aggregation inhibitors to further determine the potential use of this class of compounds for the universal treatment of conformational diseases.

Amylin Signaling in Diabetes and Alzheimer's Disease: Therapy or Pathology?

Growing evidence highlights the intimate relationship between type II diabetes (T2D) and Alzheimer's disease (AD). Importantly, these two diseases share a number of pathological similarities, including amyloid accumulation, oxidative stress, inflammation, and cell death. To date, drug therapies for AD and T2D are lacking and there is a crucial need for the discovery and development of novel therapeutics for these diseases. A number of human and rodent studies have given evidence that metabolic hormone supplementation is highly valuable for improving cognitive function and overall metabolic health in both T2D and AD. The pancreatic hormone amylin has arisen as a crucial component of the disease etiology of both T2D and AD, though the exact role that amylin plays in these diseases is not yet well understood. Here, we critically review the current literature that utilizes human amylin or its synthetic analogue, pramlintide, as well as amylin receptor antagonists for the treatment of AD.

IAPP/amylin and β-cell failure: implication of the risk factors of type 2 diabetes

In type 2 diabetes (T2D), the most significant pathological change in pancreatic islets is amyloid deposits, of which a major component is islet amyloid polypeptide (IAPP), also called amylin. IAPP is expressed in β-cells and co-secreted with insulin. Together with the inhibitory effects of synthetic human IAPP (hIAPP) on insulin secretion, our studies, using hIAPP transgenic mice, in which glucose-stimulated insulin secretion was moderately reduced without amyloid deposit, and hIAPP gene-transfected β-cell lines, in which insulin secretion was markedly impaired without amyloid, predicted that soluble hIAPP-related molecules would exert cytotoxicity on β-cells. Human IAPP is one of the most aggregation-prone peptides that interact with cell membranes. While it is widely reported that soluble hIAPP oligomers promote cytotoxicity, this is still a hypothesis since the mechanisms are not yet fully defined. Several hIAPP transgenic mouse models did not develop diabetes; however, in models with backgrounds characterized for diabetic phenotypes, β-cell function and glucose tolerance did worsen, compared to those in non-transgenic models with similar backgrounds. Together with these findings, many studies on metabolic and molecular disorders induced by risk factors of T2D suggest that in T2D subjects, toxic IAPP oligomers accumulate in β-cells, impair their function, and reduce mass through disruption of cell membranes, resulting in β-cell failure. IAPP might be central to β-cell failure in T2D. Anti-amyloid aggregation therapeutics will be developed to create treatments with more durable and beneficial effects on β-cell function.

Amylin Receptor: A Potential Therapeutic Target for Alzheimer's Disease

Alzheimer'sdisease (AD) is a progressive neurodegenerative disorder, characterized by senile plaques constituting extracellular deposits of β-amyloid (Aβ) fibrils. Since Aβ accumulation in the brain is considered an early event preceding, by decades, cognitive dysfunction, disease-modifying treatments are aimed at facilitating clearance of this protein from the brain or ameliorating its toxic effects. Recent studies have identified the amylin receptor as a capable mediator of the deleterious actions of Aβ and furthermore, administration of amylin receptor-based peptides has been shown to improve spatial memory and learning in transgenic mouse models of AD. Here, by discussing available evidence, we posit that the amylin receptor could be considered a potential therapeutic target for AD, and present the rationale for using amylin receptor antagonists to treat this debilitating condition.

Islet amyloid polypeptide: Another key molecule in Alzheimer's pathogenesis?

Recent epidemiological evidence reveals that patients suffering from type 2 diabetes mellitus (T2DM) often experience a significant decline in cognitive function, and approximately 70% of those cases eventually develop Alzheimer's disease (AD). Although several pathological processes are shared by AD and T2DM, the exact molecular mechanisms connecting these two diseases are poorly understood. Aggregation of human islet amyloid polypeptide (hIAPP), the pathological hallmark of T2DM, has also been detected in brain tissue and is associated with cognitive decline and AD development. In addition, hIAPP and amyloid β protein (Aβ) share many biophysical and physiological properties as well as exert similar cytotoxic mechanisms. Therefore, it is important to examine the possible role of hIAPP in the pathogenesis of AD. In this article, we introduce the basics on this amyloidogenic protein. More importantly, we discuss the potential mechanisms of hIAPP-induced AD development, which will be beneficial for proposing novel and feasible strategies to optimize AD prevention and/or treatment in diabetics.

Genome-wide interaction study of brain beta-amyloid burden and cognitive impairment in Alzheimer's disease

The lack of strong association between brain beta-amyloid deposition and cognitive impairment has been a challenge for the Alzheimer's disease (AD) field. Although beta-amyloid is necessary for the pathologic diagnosis of AD, it is not sufficient to make the pathologic diagnosis or cause dementia. We sought to identify the genetic modifiers of the relation between cortical beta-amyloid burden (measured using [18F]Florbetapir-PET) and cognitive dysfunction (measured using ADAS-cog) by conducting a genome-wide interaction study on baseline data from participants in the Alzheimer's Disease Neuroimaging Initiative (ADNI) phases GO/2 (n=678). Near genome-wide significant interaction effect was observed for rs73069071 within the IAPP (amylin) and SLCO1A2 genes (P=6.2 × 10-8). Congruent results were found using data from participants followed up from ADNI-1 (Pone-tailed=0.028, n=165). Meta-analysis across ADNI-GO/2 and ADNI-1 revealed a genome-wide significant interaction effect (P=1.1 × 10-8). Our results were further supported by similar interaction effects on temporal lobe cortical thickness (whole-brain voxelwise analysis: familywise error corrected P=0.013) and longitudinal changes in ADAS-cog score and left middle temporal thickness and amygdalar volume (Pone-tailed=0.026, 0.019 and 0.003, respectively). Using postmortem beta-amyloid immunohistochemistry data from 243 AD participants in the Religious Orders Study and Memory and Aging Project, we also observed similar rs73069071-by-beta-amyloid deposition interaction effect on global cognitive function (Pone-tailed=0.005). Our findings provide insight into the complexity of the relationship between beta-amyloid burden and AD-related cognitive impairment. Although functional studies are required to elucidate the role of rs73069071 in AD pathophysiology, our results support the recently growing evidence on the role of amylin in AD.

Receptor-mediated toxicity of human amylin fragment aggregated by short- and long-term incubations with copper ions

Human amylin (hA1-37) is a polypeptide hormone secreted in conjunction with insulin from the pancreatic β-cells involved in the pathogenesis of type 2 diabetes mellitus (T2DM). The shorter fragment hA17-29 than full-length peptide is capable to form amyloids "in vitro". Here, we monitored the time course of hA17-29 β-amyloid fibril and oligomer formation [without and with copper(II)], cellular toxicity of different amyloid aggregates, and involvement of specific receptors (receptor for advanced glycation end-products, RAGE; low-affinity nerve growth factor receptor, p75-NGFR) in aggregate toxicity. Fibril and oligomer formation of hA17-29 incubated at 37 °C for 0, 48, and 120 h, without or with copper(II), were measured by the thioflavin T fluorescence assay and ELISA, respectively. Toxicity of hA17-29 aggregates and effects of anti-RAGE and anti-p75-NGFR antibodies were evaluated on neuroblastoma SH-SY5Y viability. Fluorescence assay of hA17-29 indicates an initial slow rate of soluble fibril formation (48 h), followed by a slower rate of insoluble aggregate formation (120 h). The highest quantity of oligomers was recorded when hA17-29 was pre-aggregated for 48 h in the presence of copper(II) showing also the maximal cell toxicity (-44% of cell viability, p < 0.01 compared to controls). Anti-RAGE or anti-p75-NGFR antibodies almost abolished cell toxicity of hA17-29 aggregates. These results indicate that copper(II) influences the aggregation process and hA17-29 toxicities are especially attributable to oligomeric aggregates. hA17-29 aggregate toxicity seems to be mediated by RAGE and p75-NGFR receptors which might be potential targets for new drugs in T2DM treatment.

Lipoprotein binding to anionic biopolyelectrolytes and the effect of glucose on nanoplaque formation in arteriosclerosis and Alzheimer's disease

Arteriosclerosis with its clinical sequelae (cardiac infarction, stroke, peripheral arterial occlusive disease) and vascular/Alzheimer dementia not only result in far more than half of all deaths but also represent dramatic economic problems. The reason is, among others, that diabetes mellitus is an independent risk factor for both disorders, and the number of diabetics strongly increases worldwide. More than one-half of infants in the first 6months of life have already small collections of macrophages and macrophages filled with lipid droplets in susceptible segments of the coronary arteries. On the other hand, the authors of the Bogalusa Heart Study found a strong increase in the prevalence of obesity in childhood that is paralleled by an increase in blood pressure, blood lipid concentration, and type 2 diabetes mellitus. Thus, there is a clear linkage between arteriosclerosis/Alzheimer's disease on the one hand and diabetes mellitus on the other hand. Furthermore, it has been demonstrated that distinct apoE isoforms on the blood lipids further both arteriosclerotic and Alzheimer nanoplaque formation and therefore impair flow-mediated vascular reactivity as well. Nanoplaque build-up seems to be the starting point for arteriosclerosis and Alzheimer's disease in their later full clinical manifestation. In earlier work, we could portray the anionic biopolyelectrolytes syndecan/perlecan as blood flow sensors and lipoprotein receptors in cell membrane and vascular matrix. We described extensively molecular composition, conformation, form and function of the macromolecule heparan sulfate proteoglycan (HS-PG). In two supplementary experimental settings (ellipsometry, myography), we utilized isolated HS-PG for in vitro nanoplaque investigations and isolated human coronary artery segments for in vivo tension measurements. With the ellipsometry-based approach, we were successful in establishing a direct connection on a molecular level between diabetes mellitus on the one side and arteriosclerosis/Alzheimer's disease on the other side. Application of glucose at a concentration representative for diabetics and leading to glycation of proteins and lipids, entailed a significant increase in arteriosclerotic and Alzheimer nanoplaque formation. IDLapoE4/E4 was by far superior to IDLapoE3/E3 in plaque build-up, both in diabetic and non-diabetic patients. Recording vascular tension of flow-dependent reactivity in blood substitute solution and under application of different IDLapoE isoforms showed an impaired vasorelaxation for pooled IDL and IDLapoE4/E4, thus confirming the ellipsometric investigations. Incubation in IDLapoE0/E0 (apoE "knockout man"), however, resulted in a massive flow-mediated contraction, also complemented by strongly aggregated nanoplaques. In contrast, HDL was shown to present a powerful protection against nanoplaque formation on principle, both in the in vitro model and the in vivo scenario on the endothelial cell membrane. The competitive interplay with LDL is highlighted through the flow experiment, where flow-mediated, HDL-induced vasodilatation remains untouched by additional incubation with LDL. This is due to the four times higher affinity for the proteoglycan receptor of HDL as compared to LDL. Taken together, the studies demonstrate that while simplistic, the ellipsometry approach and the endothelial-mimicking proteoglycan-modified surfaces provide information on the initial steps of lipoprotein-related plaque formation, which correlates with findings on endothelial cells and blood vessels, and afford insight into the role of lipoprotein deposition and exchange phenomena at the onset of these pathophysiologies.

Common neurodegenerative pathways in obesity, diabetes, and Alzheimer's disease

Cognitive decline in chronic diabetic patients is a less investigated topic. Diabetes and obesity are among the modifiable risk factors for Alzheimer's disease (AD), the most common form of dementia. Studies have identified several overlapping neurodegenerative mechanisms, including oxidative stress, mitochondrial dysfunction, and inflammation that are observed in these disorders. Advanced glycation end products generated by chronic hyperglycemia and their receptor RAGE provide critical links between diabetes and AD. Peripheral inflammation observed in obesity leads to insulin resistance and type 2 diabetes. Although the brain is an immune-privileged organ, cross-talks between peripheral and central inflammation have been reported. Damage to the blood brain barrier (BBB) as seen with aging can lead to infiltration of immune cells into the brain, leading to the exacerbation of central inflammation. Neuroinflammation, which has emerged as an important cause of cognitive dysfunction, could provide a central mechanism for aging-associated ailments. To further add to these injuries, adult neurogenesis that provides neuronal plasticity is also impaired in the diabetic brain. This review discusses these molecular mechanisms that link obesity, diabetes and AD. This article is part of a Special Issue entitled: Oxidative Stress and Mitochondrial Quality in Diabetes/Obesity and Critical Illness Spectrum of Diseases - edited by P. Hemachandra Reddy.