Alzheimer's disease is type 3 diabetes-evidence reviewed

Hyperinsulinemia and Insulin Resistance: Scope of the Problem

No abstract available.

Dysfunctional organization of default mode network before memory impairments in type 2 diabetes

AIMS

Episodic memory depends on the maintenance of an intact default mode network (DMN), and is one of the earliest cognitive domains to become impaired in type 2 diabetes mellitus (T2DM). Therefore, exploring the alterations in task-related DMN deactivation and functional connectivity that affect episodic memory in T2DM will help to enhance our understanding of the allocation patterns underlying memory function in T2DM.

METHODS

The current study assessed changes in DMN activation and architecture during the encoding of a functional magnetic resonance imaging task in 39 patients with T2DM and 41 healthy controls which were recruited from local communities in Beijing, China.

RESULTS

We found that patients with T2DM and intact episodic memory performance exhibited reduced deactivation in the right precuneus and the middle temporal gyrus during the episodic memory task. Furthermore, an anterior-posterior disconnection phenotype and altered topological configuration of the DMN were observed in patients with T2DM using graph-theoretical approaches. Correlation analysis showed that altered deactivation during the episodic memory task was closely related to connectivity dysfunction and topological properties in the DMN.

CONCLUSIONS

Our findings demonstrate that the maintenance of memory in patients with T2DM involves reduced deactivation and impaired anterior-posterior connections in the DMN during encoding.

Long-term exposition to a high fat diet favors the appearance of β-amyloid depositions in the brain of C57BL/6J mice. A potential model of sporadic Alzheimer's disease

AIMS

The sporadic and late-onset form of Alzheimer's disease (AD) constitutes the most common form of dementia. This non-familiar form could be a consequence of metabolic syndrome, characterized by obesity and the development of a brain-specific insulin resistance known as type III diabetes. This work demonstrates the development of a significant AD-like neuropathology due to these metabolic alterations.

METHODS

C57BL/6J mice strain were divided into two groups, one fed with a diet rich in palmitic acid (high-fat diet, HFD) since their weaning until 16 months of age, and another group used as a control with a regular diet. The analyses were carried out in the dentate gyrus area of the hippocampus using a Thioflavin-S stain and immunofluorescence assays.

RESULTS

The most significant finding of the present research was that HFD induced the deposition of the βA peptide. Moreover, the diet also caused alterations in different cell processes, such as increased inflammatory reactions that lead to a decrease in the neuronal precursor cells. In addition, the results show that there were also dysregulations in normal autophagy and apoptosis, mechanisms related to βA formation.

CONCLUSIONS

The present findings confirm that HFD favors the formation of βA depositions in the brain, a key feature of AD, supporting the metabolic hypothesis of sporadic AD.

High glucose upregulates BACE1-mediated Aβ production through ROS-dependent HIF-1α and LXRα/ABCA1-regulated lipid raft reorganization in SK-N-MC cells

There is an accumulation of evidence indicating that the risk of Alzheimer’s disease is associated with diabetes mellitus, an indicator of high glucose concentrations in blood plasma. This study investigated the effect of high glucose on BACE1 expression and amyloidogenesis in vivo, and we present details of the mechanism associated with those effects. Our results, using ZLC and ZDF rat models, showed that ZDF rats have high levels of amyloid-beta (Aβ), phosphorylated tau, BACE1, and APP-C99. In vitro result with mouse hippocampal neuron and SK-N-MC, high glucose stimulated Aβ secretion and apoptosis in a dose-dependent manner. In addition, high glucose increased BACE1 and APP-C99 expressions, which were reversed by a reactive oxygen species (ROS) scavenger. Indeed, high glucose increased intracellular ROS levels and HIF-1α expression, associated with regulation of BACE1 and Liver X Receptor α (LXRα). In addition, high glucose induced ATP-binding cassette transporter A1 (ABCA1) down-regulation, was associated with LXR-induced lipid raft reorganization and BACE1 localization on the lipid raft. Furthermore, silencing of BACE1 expression was shown to regulate Aβ secretion and apoptosis of SK-N-MC. In conclusion, high glucose upregulates BACE1 expression and activity through HIF-1α and LXRα/ABCA1-regulated lipid raft reorganization, leading to Aβ production and apoptosis of SK-N-MC.

Tobacco Smoke Exposure Impairs Brain Insulin/IGF Signaling: Potential Co-Factor Role in Neurodegeneration

BACKGROUND

Human studies suggest tobacco smoking is a risk factor for cognitive impairment and neurodegeneration, including Alzheimer's disease (AD). However, experimental data linking tobacco smoke exposures to underlying mediators of neurodegeneration, including impairments in brain insulin and insulin-like growth factor (IGF) signaling in AD are lacking.

OBJECTIVE

This study tests the hypothesis that cigarette smoke (CS) exposures can impair brain insulin/IGF signaling and alter expression of AD-associated proteins.

METHODS

Adult male A/J mice were exposed to air for 8 weeks (A8), CS for 4 or 8 weeks (CS4, CS8), or CS8 followed by 2 weeks recovery (CS8+R). Gene expression was measured by qRT-PCR analysis and proteins were measured by multiplex bead-based or direct binding duplex ELISAs.

RESULTS

CS exposure effects on insulin/IGF and insulin receptor substrate (IRS) proteins and phosphorylated proteins were striking compared with the mRNA. The main consequences of CS4 or CS8 exposures were to significantly reduce insulin R, IGF-1R, IRS-1, and tyrosine phosphorylated insulin R and IGF-1R proteins. Paradoxically, these effects were even greater in the CS8+R group. In addition, relative levels of S312-IRS-1, which inhibits downstream signaling, were increased in the CS4, CS8, and CS8+R groups. Correspondingly, CS and CS8+R exposures inhibited expression of proteins and phosphoproteins required for signaling through Akt, PRAS40, and/or p70S6K, increased AβPP-Aβ, and reduced ASPH protein, which is a target of insulin/IGF-1 signaling.

CONCLUSION

Secondhand CS exposures caused molecular and biochemical abnormalities in brain that overlap with the findings in AD, and many of these effects were sustained or worsened despite short-term CS withdrawal.

Insulin signalling in Alzheimer's disease and diabetes: from epidemiology to molecular links

As populations across the world both age and become more obese, the numbers of individuals with Alzheimer's disease and diabetes are increasing; posing enormous challenges for society and consequently becoming priorities for governments and global organizations. These issues, an ageing population at risk of neurodegenerative diseases such as Alzheimer's disease and an increasingly obese population at risk of metabolic alterations such as type 2 diabetes, are usually considered as independent conditions, but increasing evidence from both epidemiological and molecular studies link these disorders. The aim of this review was to highlight these multifactorial links. We will discuss the impact of direct links between insulin and IGF-1 signalling and the Alzheimer's disease-associated pathological events as well as the impact of other processes such as inflammation, oxidative stress and mitochondrial dysfunction either common to both conditions or perhaps responsible for a mechanistic link between metabolic and neurodegenerative disease. An understanding of such associations might be of importance not only in the understanding of disease mechanisms but also in the search for novel therapeutic options.

Resting-state functional MR imaging shed insights into the brain of diabetes

Diabetes mellitus is a common metabolic disease which is associated with increasing risk for multiple cognitive declines. Alterations in brain functional connectivity are believed to be the mechanisms underlying the cognitive function impairments. During the past decade, resting-state functional magnetic resonance imaging (rs-fMRI) has been developed as a major tool to study brain functional connectivity in vivo. This paper briefly reviews the diabetes-associated cognitive impairment, analysis algorithms and clinical applications of rs-fMRI. We also provide future perspectives of rs-fMRI in diabetes.

Effect of glycation inhibitors on aging and age-related diseases

Vast evidence supports the view that glycation of proteins is one of the main factors contributing to aging and is an important element of etiopathology of age-related diseases, especially type 2 diabetes mellitus, cataract and neurodegenerative diseases. Counteracting glycation can therefore be a means of increasing both the lifespan and healthspan. In this review, accumulation of glycation products during aging is presented, pathophysiological effects of glycation are discussed and ways of attenuation of the effects of glycation are described, concentrating on prevention of glycation. The effects of glycation and glycation inhibitors on the course of selected age-related diseases, such as Alzheimer's disease, Parkinson's disease and cataract are also reviewed.

Epigenomic and metabolic responses of hypothalamic POMC neurons to gestational nicotine exposure in adult offspring

Background

Epidemiological and animal studies have reported that prenatal nicotine exposure (PNE) leads to obesity and type-2 diabetes in offspring. Central leptin-melanocortin signaling via hypothalamic arcuate proopiomelanocortin (POMC) neurons is crucial for the regulation of energy and glucose balance. Furthermore, hypothalamic POMC neurons were recently found to mediate the anorectic effects of nicotine through activation of acetylcholine receptors. Here, we hypothesized that PNE impairs leptin-melanocortinergic regulation of energy balance in first-generation offspring by altering expression of long non-coding RNAs (lncRNAs) putatively regulating development and/or function of hypothalamic POMC neurons.

Methods

C57BL/6J females were exposed ad libitum to nicotine through drinking water and crossed with C57BL/6J males. Nicotine exposure was sustained during pregnancy and discontinued at parturition. Offspring development was monitored from birth into adulthood. From the age of 8 weeks, central leptin-melanocortin signaling, diabetes, and obesity susceptibility were assessed in male offspring fed a low-fat or high-fat diet for 16 weeks. Nicotine-exposed and non-exposed C57BL/6J females were also crossed with C57BL/6J males expressing the enhanced green fluorescent protein specifically in POMC neurons. Transgenic male offspring were subjected to laser microdissections and RNA sequencing (RNA-seq) analysis of POMC neurons for determination of nicotine-induced gene expression changes and regulatory lncRNA/protein-coding gene interactions.

Results

Contrary to expectation based on previous studies, PNE did not impair but rather enhanced leptin-melanocortinergic regulation of energy and glucose balance via POMC neurons in offspring. RNA-seq of laser microdissected POMC neurons revealed only one consistent change, upregulation of Gm15851, a lncRNA of yet unidentified function, in nicotine-exposed offspring. RNA-seq further suggested 82 cis-regulatory lncRNA/protein-coding gene interactions, 19 of which involved coding genes regulating neural development and/or function, and revealed expression of several previously unidentified metabolic, neuroendocrine, and neurodevelopment pathways in POMC neurons.

Conclusions

PNE does not result in obesity and type 2 diabetes but instead enhances leptin-melanocortinergic feeding and body weight regulation via POMC neurons in adult offspring. PNE leads to selective upregulation of Gm15851, a lncRNA, in adult offspring POMC neurons. POMC neurons express several lncRNAs and pathways possibly regulating POMC neuronal development and/or function.

Electronic supplementary material

The online version of this article (doi:10.1186/s13073-016-0348-2) contains supplementary material, which is available to authorized users.

Effects of Diabetes Mellitus on Cognitive Decline in Patients with Alzheimer Disease: A Systematic Review

Basic and clinical research support a link between diabetes mellitus and Alzheimer disease (AD). However, the relationship with AD progression is unclear. This review focuses on the association between diabetes and cognitive decline in patients with AD. The literature published through May 2015 was searched in 3 databases: PubMed, Embase and Cochrane. Studies evaluating the effects of diabetes on patients with AD or cognitive decline were included, and extracted data were analyzed. A total of 10 articles met the inclusion criteria for review. The results of these studies were inconsistent in terms of the association between diabetes and cognitive decline. Only 2 studies demonstrated that the presence of diabetes was independently related to the progression of cognitive decline in the patients with AD, and 3 studies suggested that histories of diabetes were not correlated with the changes in cognitive function in patients with AD. Half of the included studies even indicated that histories of diabetes were associated with lesser declines in cognitive function in patients with AD. Current evidence indicates that the link between diabetes and cognitive decline in patients with AD is uncertain. Further clinical studies are needed, with larger samples, long-term follow up and an extended battery of cognitive assessments.

Concurrence of High Fat Diet and APOE Gene Induces Allele Specific Metabolic and Mental Stress Changes in a Mouse Model of Alzheimer's Disease

Aging is the main risk factor for neurodegenerative diseases, including Alzheimer's disease (AD). However, evidence indicates that the pathological process begins long before actual cognitive or pathological symptoms are apparent. The long asymptomatic phase and complex integration between genetic, environmental and metabolic factors make it one of the most challenging diseases to understand and cure. In the present study, we asked whether an environmental factor such as high-fat (HF) diet would synergize with a genetic factor to affect the metabolic and cognitive state in the Apolipoprotein E (ApoE4) mouse model of AD. Our data suggest that a HF diet induces diabetes mellitus (DM)-like metabolism in ApoE4 mice, as well as changes in β-site amyloid precursor protein-cleaving enzyme 1 (BACE1) protein levels between the two ApoE strains. Furthermore, HF diet induces anxiety in this AD mouse model. Our results suggest that young ApoE4 carriers are prone to psychological stress and metabolic abnormalities related to AD, which can easily be triggered via HF nutrition.

Type 2 diabetes mellitus as a risk factor for dementia in a Mexican population

INTRODUCTION

Type 2 diabetes mellitus (T2DM) and dementia increase with age. Different studies have explored their association, but the possible relationship between them is still unclear.

METHODS

This is an analysis of the 10/66 Dementia Research Group (DRG) Mexico database; the sample comprised 1193 subjects ≥65 years old followed-up for three years. We calculated the incidence of dementia in subjects with diabetes using three models of analysis.

RESULTS

T2DM patients have nearly twice the risk of developing dementia (RR 1.9; 95% CI 1.3-2.6) after three years of follow-up. The incidence of dementia is higher in subjects with undiagnosed diabetes. Higher serum glucose levels have a stronger association with dementia.

CONCLUSIONS

It is important to implement early evaluation and monitoring cognitive performance in elders with diabetes to identify minor cognitive impairment and undertake timely interventions to prevent or delay the onset of dementia.

Is Alzheimer's disease a Type 3 Diabetes? A critical appraisal

Recently researchers proposed the term 'Type-3-Diabetes' for Alzheimer's disease (ad) because of the shared molecular and cellular features among Type-1-Diabetes, Type-2-Diabetes and insulin resistance associated with memory deficits and cognitive decline in elderly individuals. Recent clinical and basic studies on patients with diabetes and AD revealed previously unreported cellular and pathological among diabetes, insulin resistance and AD. These studies are also strengthened by various basic biological studies that decipher the effects of insulin in the pathology of AD through cellular and molecular mechanisms. For instance, insulin is involved in the activation of glycogen synthase kinase 3β, which in turn causes phosphorylation of tau, which involved in the formation of neurofibrillary tangles. Interestingly, insulin also plays a crucial role in the formation amyloid plaques. In this review, we discussed significant shared mechanisms between AD and diabetes and we also provided therapeutic avenues for 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.

Interacting with the Human Insulin Receptor

Insulin is an essential regulator of glucose homeostasis. In this issue of Structure, Croll et al. (2016) reports a significantly improved model of the Fab-complexed IR ectodomain refined against a dataset extending to 3.3 Å.

Key Targets for Multi-Target Ligands Designed to Combat Neurodegeneration

HIGHLIGHTS Compounds that interact with multiple targets but minimally with the cytochrome P450 system (CYP) address the many factors leading to neurodegeneration.Acetyl- and Butyryl-cholineEsterases (AChE, BChE) and Monoamine Oxidases A/B (MAO A, MAO B) are targets for Multi-Target Designed Ligands (MTDL).ASS234 is an irreversible inhibitor of MAO A >MAO B and has micromolar potency against the cholinesterases.ASS234 is a poor CYP substrate in human liver, yielding the depropargylated metabolite.SMe1EC2, a stobadine derivative, showed high radical scavenging property, in vitro and in vivo giving protection in head trauma and diabetic damage of endothelium.Control of mitochondrial function and morphology by manipulating fission and fusion is emerging as a target area for therapeutic strategies to decrease the pathological outcome of neurodegenerative diseases. Growing evidence supports the view that neurodegenerative diseases have multiple and common mechanisms in their aetiologies. These multifactorial aspects have changed the broadly common assumption that selective drugs are superior to "dirty drugs" for use in therapy. This drives the research in studies of novel compounds that might have multiple action mechanisms. In neurodegeneration, loss of neuronal signaling is a major cause of the symptoms, so preservation of neurotransmitters by inhibiting the breakdown enzymes is a first approach. Acetylcholinesterase (AChE) inhibitors are the drugs preferentially used in AD and that one of these, rivastigmine, is licensed also for PD. Several studies have shown that monoamine oxidase (MAO) B, located mainly in glial cells, increases with age and is elevated in Alzheimer (AD) and Parkinson's Disease's (PD). Deprenyl, a MAO B inhibitor, significantly delays the initiation of levodopa treatment in PD patients. These indications underline that AChE and MAO are considered a necessary part of multi-target designed ligands (MTDL). However, both of these targets are simply symptomatic treatment so if new drugs are to prevent degeneration rather than compensate for loss of neurotransmitters, then oxidative stress and mitochondrial events must also be targeted. MAO inhibitors can protect neurons from apoptosis by mechanisms unrelated to enzyme inhibition. Understanding the involvement of MAO and other proteins in the induction and regulation of the apoptosis in mitochondria will aid progress toward strategies to prevent the loss of neurons. In general, the oxidative stress observed both in PD and AD indicate that antioxidant properties are a desirable part of MTDL molecules. After two or more properties are incorporated into one molecule, the passage from a lead compound to a therapeutic tool is strictly linked to its pharmacokinetic and toxicity. In this context the interaction of any new molecules with cytochrome P450 and other xenobiotic metabolic processes is a crucial point. The present review covers the biochemistry of enzymes targeted in the design of drugs against neurodegeneration and the cytochrome P450-dependent metabolism of MTDLs.

Short-Term High-Fat Diet (HFD) Induced Anxiety-Like Behaviors and Cognitive Impairment Are Improved with Treatment by Glyburide

Obesity-associated comorbidities such as cognitive impairment and anxiety are increasing public health burdens that have gained prevalence in children. To better understand the impact of childhood obesity on brain function, mice were fed with a high-fat diet (HFD) from weaning for 1, 3 or 6 weeks. When compared to low-fat diet (LFD)-fed mice (LFD-mice), HFD-fed mice (HFD-mice) had impaired novel object recognition (NOR) after 1 week. After 3 weeks, HFD-mice had impaired NOR and object location recognition (OLR). Additionally, these mice displayed anxiety-like behavior by measure of both the open-field and elevated zero maze (EZM) testing. At 6 weeks, HFD-mice were comparable to LFD-mice in NOR, open-field and EZM performance but they remained impaired during OLR testing. Glyburide, a second-generation sulfonylurea for the treatment of type 2 diabetes, was chosen as a countermeasure based on previous data exhibiting its potential as an anxiolytic. Interestingly, a single dose of glyburide corrected deficiencies in NOR and mitigated anxiety-like behaviors in mice fed with HFD-diet for 3-weeks. Taken together these results indicate that a HFD negatively impacts a subset of hippocampal-independent behaviors relatively rapidly, but such behaviors normalize with age. In contrast, impairment of hippocampal-sensitive memory takes longer to develop but persists. Since single-dose glyburide restores brain function in 3-week-old HFD-mice, drugs that block ATP-sensitive K(+) (KATP) channels may be of clinical relevance in the treatment of obesity-associated childhood cognitive issues and psychopathologies.

Exercise for the diabetic brain: how physical training may help prevent dementia and Alzheimer's disease in T2DM patients

Epidemiological studies indicate that patients with type 2 diabetes mellitus (T2DM) are at increased risk of developing dementia/Alzheimer's disease (AD). This review, which is based on recent studies, presents a molecular framework that links the two diseases and explains how physical training could help counteract neurodegeneration in T2DM patients. Inflammatory, oxidative, and metabolic changes in T2DM patients cause cerebrovascular complications and can lead to blood-brain-barrier (BBB) breakdown. Peripherally increased pro-inflammatory molecules can then pass the BBB more easily and activate stress-activated pathways, thereby promoting key pathological features of dementia/AD such as brain insulin resistance, mitochondrial dysfunction, and accumulation of neurotoxic beta-amyloid (Aβ) oligomers, leading to synaptic loss, neuronal dysfunction, and cell death. Ceramides can also pass the BBB, induce pro-inflammatory reactions, and disturb brain insulin signaling. In a vicious circle, oxidative stress and the pro-inflammatory environment intensify, leading to further cognitive decline. Low testosterone levels might be a common risk factor in T2DM and AD. Regular physical exercise reinforces antioxidative capacity, reduces oxidative stress, and has anti-inflammatory effects. It improves endothelial function and might increase brain capillarization. Physical training can further counteract dyslipidemia and reduce increased ceramide levels. It might also improve Aβ clearance by up-regulating Aβ transporters and, in some cases, increase basal testosterone levels. In addition, regular physical activity can induce neurogenesis. Physical training should therefore be emphasized as a part of prevention programs developed for diabetic patients to minimize the risk of the onset of neurodegenerative diseases among this specific patient group.

Insulin in the nervous system and the mind: Functions in metabolism, memory, and mood

BACKGROUND

Insulin, a pleotrophic hormone, has diverse effects in the body. Recent work has highlighted the important role of insulin's action in the nervous system on glucose and energy homeostasis, memory, and mood.

SCOPE OF REVIEW

Here we review experimental and clinical work that has broadened the understanding of insulin's diverse functions in the central and peripheral nervous systems, including glucose and body weight homeostasis, memory and mood, with particular emphasis on intranasal insulin.

MAJOR CONCLUSIONS

Implications for the treatment of obesity, type 2 diabetes, dementia, and mood disorders are discussed in the context of brain insulin action. Intranasal insulin may have potential in the treatment of central nervous system-related metabolic disorders.

Metformin Prevents Nigrostriatal Dopamine Degeneration Independent of AMPK Activation in Dopamine Neurons

Metformin is a widely prescribed drug used to treat type-2 diabetes, although recent studies show it has wide ranging effects to treat other diseases. Animal and retrospective human studies indicate that Metformin treatment is neuroprotective in Parkinson's Disease (PD), although the neuroprotective mechanism is unknown, numerous studies suggest the beneficial effects on glucose homeostasis may be through AMPK activation. In this study we tested whether or not AMPK activation in dopamine neurons was required for the neuroprotective effects of Metformin in PD. We generated transgenic mice in which AMPK activity in dopamine neurons was ablated by removing AMPK beta 1 and beta 2 subunits from dopamine transporter expressing neurons. These AMPK WT and KO mice were then chronically exposed to Metformin in the drinking water then exposed to MPTP, the mouse model of PD. Chronic Metformin treatment significantly attenuated the MPTP-induced loss of Tyrosine Hydroxylase (TH) neuronal number and volume and TH protein concentration in the nigrostriatal pathway. Additionally, Metformin treatment prevented the MPTP-induced elevation of the DOPAC:DA ratio regardless of genotype. Metformin also prevented MPTP induced gliosis in the Substantia Nigra. These neuroprotective actions were independent of genotype and occurred in both AMPK WT and AMPK KO mice. Overall, our studies suggest that Metformin's neuroprotective effects are not due to AMPK activation in dopaminergic neurons and that more research is required to determine how metformin acts to restrict the development of PD.

Unified theory of Alzheimer's disease (UTAD): implications for prevention and curative therapy

The aim of this review is to propose a Unified Theory of Alzheimer's disease (UTAD) that integrates all key behavioural, genetic and environmental risk factors in a causal chain of etiological and pathogenetic events. It is based on three concepts that emanate from human's evolutionary history: (1) The grandmother-hypothesis (GMH), which explains human longevity due to an evolutionary advantage in reproduction by trans-generational transfer of acquired knowledge. Consequently it is argued that mental health at old-age must be the default pathway of humans' genetic program and not development of AD. (2) Therefore, mechanism like neuronal rejuvenation (NRJ) and adult hippocampal neurogenesis (AHN) that still function efficiently even at old age provide the required lifelong ability to memorize personal experiences important for survival. Cumulative evidence from a multitude of experimental and epidemiological studies indicate that behavioural and environmental risk factors, which impair productive AHN, result in reduced episodic memory performance and in reduced psychological resilience. This leads to avoidance of novelty, dysregulation of the hypothalamic-pituitary-adrenal (HPA)-axis and cortisol hypersecretion, which drives key pathogenic mechanisms of AD like the accumulation and oligomerization of synaptotoxic amyloid beta, chronic neuroinflammation and neuronal insulin resistance. (3) By applying to AHN the law of the minimum (LOM), which defines the basic requirements of biological growth processes, the UTAD explains why and how different lifestyle deficiencies initiate the AD process by impairing AHN and causing dysregulation of the HPA-axis, and how environmental and genetic risk factors such as toxins or ApoE4, respectively, turn into disease accelerators under these unnatural conditions. Consequently, the UTAD provides a rational strategy for the prevention of mental decline and a system-biological approach for the causal treatment of AD, which might even be curative if the systemic intervention is initiated early enough in the disease process. Hence an individualized system-biological treatment of patients with early AD is proposed as a test for the validity of UTAD and outlined in this review.

Human ApoE Isoforms Differentially Modulate Glucose and Amyloid Metabolic Pathways in Female Brain: Evidence of the Mechanism of Neuroprotection by ApoE2 and Implications for Alzheimer's Disease Prevention and Early Intervention

Three major genetic isoforms of apolipoprotein E (ApoE), ApoE2, ApoE3, and ApoE4, exist in humans and lead to differences in susceptibility to Alzheimer's disease (AD). This study investigated the impact of human ApoE isoforms on brain metabolic pathways involved in glucose utilization and amyloid-β (Aβ) degradation, two major areas that are significantly perturbed in preclinical AD. Hippocampal RNA samples from middle-aged female mice with targeted human ApoE2, ApoE3, and ApoE4 gene replacement were comparatively analyzed with a qRT-PCR custom array for the expression of 85 genes involved in insulin/insulin-like growth factor (Igf) signaling. Consistent with its protective role against AD, ApoE2 brain exhibited the most metabolically robust profile among the three ApoE genotypes. When compared to ApoE2 brain, both ApoE3 and ApoE4 brains exhibited markedly reduced levels of Igf1, insulin receptor substrates (Irs), and facilitated glucose transporter 4 (Glut4), indicating reduced glucose uptake. Additionally, ApoE4 brain exhibited significantly decreased Pparg and insulin-degrading enzyme (Ide), indicating further compromised glucose metabolism and Aβ dysregulation associated with ApoE4. Protein analysis showed significantly decreased Igf1, Irs, and Glut4 in ApoE3 brain, and Igf1, Irs, Glut4, Pparg, and Ide in ApoE4 brain compared to ApoE2 brain. These data provide the first documented evidence that human ApoE isoforms differentially affect brain insulin/Igf signaling and downstream glucose and amyloid metabolic pathways, illustrating a potential mechanism for their differential risk in AD. A therapeutic strategy that enhances brain insulin/Igf1 signaling activity to a more robust ApoE2-like phenotype favoring both energy production and amyloid homeostasis holds promise for AD prevention and early intervention.

Decreased Serum IGF-1/IGFBP-3 Molar Ratio is Associated with Executive Function Behaviors in Type 2 Diabetic Patients with Mild Cognitive Impairment

BACKGROUND

Insulin-like growth factor (IGF)-1, through insulin/IGF-1 signaling pathway, is involved in the pathogenesis of type 2 diabetes mellitus (T2DM) and Alzheimer's disease.

OBJECTIVE

This study aimed to assess the association of serum IGF-1 and IGF binding protein (IGFBP)-3 levels with cognition status and to determine whether IGF-1 rs972936 polymorphism is associated with T2DM with mild cognitive impairment (MCI).

METHODS

A total of 150 T2DM patients, 75 satisfying the MCI diagnostic criteria and 75 exhibiting healthy cognition, were enrolled in this study. The cognitive function of the subjects was extensively assessed. Serum IGF-1 and IGFBP-3 levels were measured through enzyme-linked immunosorbent assay; IGF-1/IGFBP-3 molar ratio was calculated. Single nucleotide polymorphisms of the IGF-1-(rs972936) gene were analyzed.

RESULTS

Serum IGF-1/IGFBP-3 molar ratio in MCI patients was significantly lower than that in the control group (p = 0.003). Significant negative correlations were found between IGF-1/IGFBP-3 molar ratio and Trail Making Test A and B (TMT-A and TMT-B) scores (p = 0.003; p <  0.001, respectively), which indicated executive function. Further multiple step-wise regression analysis revealed that the TMT-A or TMT-B score was significantly associated only with serum IGF-1/IGFBP-3 molar ratio (p = 0.016; p <  0.001, respectively). No significant difference was found in the genotype or allele distribution of IGF-1 rs972936 polymorphism between MCI and control groups.

CONCLUSIONS

A low serum IGF-1/IGFBP-3 molar ratio is associated with the pathogenesis of MCI, particularly executive function in T2DM populations. Further investigation with a large population size should be conducted to confirm this observed association.

Early role of vascular dysregulation on late-onset Alzheimer's disease based on multifactorial data-driven analysis

Multifactorial mechanisms underlying late-onset Alzheimer's disease (LOAD) are poorly characterized from an integrative perspective. Here spatiotemporal alterations in brain amyloid-β deposition, metabolism, vascular, functional activity at rest, structural properties, cognitive integrity and peripheral proteins levels are characterized in relation to LOAD progression. We analyse over 7,700 brain images and tens of plasma and cerebrospinal fluid biomarkers from the Alzheimer's Disease Neuroimaging Initiative (ADNI). Through a multifactorial data-driven analysis, we obtain dynamic LOAD-abnormality indices for all biomarkers, and a tentative temporal ordering of disease progression. Imaging results suggest that intra-brain vascular dysregulation is an early pathological event during disease development. Cognitive decline is noticeable from initial LOAD stages, suggesting early memory deficit associated with the primary disease factors. High abnormality levels are also observed for specific proteins associated with the vascular system's integrity. Although still subjected to the sensitivity of the algorithms and biomarkers employed, our results might contribute to the development of preventive therapeutic interventions.

Targeting Alzheimer's Disease Neuro-Metabolic Dysfunction with a Small Molecule Nuclear Receptor Agonist (T3D-959) Reverses Disease Pathologies

Background

Alzheimer’s disease (AD) could be regarded as a brain form of diabetes since insulin resistance and deficiency develop early and progress with severity of neurodegeneration. Preserving insulin’s actions in the brain restores function and reduces neurodegeneration. T3D-959 is a dual nuclear receptor agonist currently in a Phase 2a trial in mild-to-moderate AD patients (ClinicalTrials.gov identifier NCT02560753). Herein, we show that T3D-959 improves motor function and reverses neurodegeneration in a sporadic model of AD.

Methods

Long Evans rats were administered intracerebral (i.c.) streptozotocin (STZ) or normal saline (control) and dosed orally with T3D-959 (1.0 mg/kg/day) or saline for 21 or 28 days. Rotarod tests evaluated motor function. Histopathology with image analysis was used to assess neurodegeneration.

Results

T3D-959 significantly improved motor performance, and preserved both cortical and normalized white matter structure in i.c STZ-treated rats. T3D-959 treatments were effective when dosed therapeutically, whether initiated 1 day or 7 days after i.c. STZ.

Conclusion

T3D-959’s targeting neuro-metabolic dysfunctions via agonism of PPAR delta and PPAR gamma nuclear receptors provides potential disease modification in AD.

Alzheimer's disease: Is this a brain specific diabetic condition?

Alzheimer's disease (AD) and type 2 diabetes (T2DM) are the two major health issues affecting millions of elderly people worldwide, with major impacts in the patient's daily life. Numerous studies have demonstrated that patients with diabetes have an increased risk of developing AD compared with healthy individuals. The principal biological mechanisms that associate with the progression of diabetes and AD are not completely understood. Impaired insulin signaling, uncontrolled glucose metabolism, oxidative stress, abnormal protein processing, and the stimulation of inflammatory pathways are common features to both AD and T2DM. In recent years brain specific abnormalities in insulin and insulin like growth factor (IGF) signaling considered as a major trigger involved in the etiopathogenesis of AD, showing T2DM like milieu. This review summarizes the pathways that might link diabetes and AD and the effect of diminished insulin.

Aβ-Induced Insulin Resistance and the Effects of Insulin on the Cholesterol Synthesis Pathway and Aβ Secretion in Neural Cells

Alzheimer's disease (AD) is characterized by amyloid-β (Aβ) toxicity, tau pathology, insulin resistance, neuroinflammation, and dysregulation of cholesterol homeostasis, all of which play roles in neurodegeneration. Insulin has polytrophic effects on neurons and may be at the center of these pathophysiological changes. In this study, we investigated possible relationships among insulin signaling and cholesterol biosynthesis, along with the effects of Aβ42 on these pathways in vitro. We found that neuroblastoma 2a (N2a) cells transfected with the human gene encoding amyloid-β protein precursor (AβPP) (N2a-AβPP) produced Aβ and exhibited insulin resistance by reduced p-Akt and a suppressed cholesterol-synthesis pathway following insulin treatment, and by increased phosphorylation of insulin receptor subunit-1 at serine 612 (p-IRS-S612) as compared to parental N2a cells. Treatment of human neuroblastoma SH-SY5Y cells with Aβ42 also increased p-IRS-S612, suggesting that Aβ42 is responsible for insulin resistance. The insulin resistance was alleviated when N2a-AβPP cells were treated with higher insulin concentrations. Insulin increased Aβ release from N2a-AβPP cells, by which it may promote Aβ clearance. Insulin increased cholesterol-synthesis gene expression in SH-SY5Y and N2a cells, including 24-dehydrocholesterol reductase (DHCR24) and 3-hydroxy-3-methyl-glutaryl-CoA reductase (HMGCR) through sterol-regulatory element-binding protein-2 (SREBP2). While Aβ42-treated SH-SY5Y cells exhibited increased HMGCR expression and c-Jun phosphorylation as pro-inflammatory responses, they also showed down-regulation of neuro-protective/anti-inflammatory DHCR24. These results suggest that Aβ42 may cause insulin resistance, activate JNK for c-Jun phosphorylation, and lead to dysregulation of cholesterol homeostasis, and that enhancing insulin signaling may relieve the insulin-resistant phenotype and the dysregulated cholesterol-synthesis pathway to promote Aβ release for clearance from neural cells.

Aggregates-Based Boronlectins with Pyrene as Fluorophore: Multichannel Discriminative Sensing of Monosaccharides and Their Applications

Four-channel fluorescence assay toward six monosaccharides was achieved by employing two novel pyrene-functionalized boronlectins with flexible diboronic acid as receptors. The effects of pH values and aging time on the sensor properties were thoroughly evaluated by UV-vis, fluorescence spectroscopy and dynamic light scattering. We find that the fluorescence relative ratios were highly correlated with analyte concentrations at μM level. The flexibility of the receptors was perceived as an indispensable factor to produce diverse fluorescence signals toward different monosaccharides. Most importantly, integration of four fluorescence channels derived from the two sensors enables an excellent discrimination for all tested monosaccharides at a certain concentration or a concentration range via linear discriminant analysis (LDA). It is proposed that the multiple flexible linkers in the boronlectins could increase their self-adaptive capacity for different analytes, and facilitate the formation of stable boronlectin-sugar aggregate assemblies. In addition, practical sensing of glucose in the simulative blood and urine was illustrated to be feasible in the presence of interferences at physiological concentrations.

A multipronged, nutritional-based strategy for managing Alzheimer's disease

A nutritional-based strategy has been proposed in order to improve cognitive performance of Alzheimer's disease (AD) patients. The strategy requires daily dietary supplementation with magnesium (Mg), folic acid, and vitamins B6 and B12, daily consumption of silicic acid-rich mineral water in order to lower the body burden of Al, and several plasma exchange procedures in order to replace Aβ-bound albumin with fresh albumin. Evidence suggests that the deteriorating cognitive performance associated with AD may be improved by supplementation with either Mg alone or with the combination of the above three B vitamins (B vitamin combo), or by drinking silicic acid-rich mineral water, or by undergoing plasma exchange. However, for the following reasons the combination of all four therapeutic approaches may have a synergistic effect on improving cognitive performance of AD patients.

Oxytocin Protects against Stress-Induced Cell Death in Murine Pancreatic β-Cells

Oxytocin (Oxt) is a key neuropeptide that regulates maternal behaviors as well as social behaviors in mammals. Interestingly, recent studies have shown that the impairment of Oxt signaling is associated with the disturbance of metabolic homeostasis, resulting in obesity and diabetes. However, the molecular mechanism by which Oxt signaling controls metabolic responses is largely unknown. Here, we report that Oxt signaling attenuates the death of pancreatic beta cells in islets exposed to cytotoxic stresses. The protective effect of Oxt was diminished in islets isolated from oxytocin receptor knockout (Oxtr^−/−) mice. Oxtr^−/− mice developed normally, but exhibited impaired insulin secretion and showed glucose intolerance under a high-fat diet. Mechanistically, the deficiency of Oxtr impaired MAPK/ERK-CREB signaling, which exaggerated the endoplasmic reticulum stress response and ultimately increased the death of beta cells in pancreatic islets under stressed conditions. These results reveal that Oxt protects pancreatic beta cells against death caused by metabolic stress, and Oxt signaling may be a potential therapeutic target.

The Association Between Diabetes and Dementia Among Elderly Individuals: A Nationwide Inpatient Sample Analysis

BACKGROUND/AIM

To date, few studies have cross-examined the relationship between diabetes mellitus (DM) and dementia nationally. There is also a lack of evidence regarding dementia subtypes and how this relationship changes among older individuals. The objective was to better delineate this relationship and influence of multiple comorbidities using a nationwide sample.

METHODS

Data were obtained from the Nationwide Inpatient Sample 1998 to 2011 using appropriate International Classification of Diseases, Ninth Version codes. Descriptive and bivariate analysis was performed. Multivariate nominal logistic regression models adjusted for age, sex, race, and comorbidities explored the independent relationship between Alzheimer dementia (AD), non-Alzheimer dementia (VaD), and diabetes.

RESULTS

21% of the participants were diabetic patients, 3.7% had AD, and 2.2% had VaD. Diabetes prevalence in AD, VaD, and no dementia groups were 20.6%, 24.3%, and 26.2%, respectively. In the unadjusted model, those with DM had lower odds of AD (odds ratio [OR] 0.73; 95% confidence interval [CI] 0.72-0.74) and VaD (OR 0.91, 95% CI 0.89-0.92). Adjusting for age, sex, race, and comorbidities, diabetic patients had significantly higher odds of VaD (OR = 1.10, 95% CI 1.08-1.11) and lower odds of AD (OR 0.87, 95% CI 0.86-0.88). Inclusion of interaction terms (age, race/ethnicity, depression, stroke, and hypertension) made the relationship between diabetes and VaD not significant (OR 1.002, 95% CI 0.97-1.03), but the relationship of DM with AD remained significant (OR 0.57, 95% CI 0.56-0.58; P < .05).

CONCLUSION

Patients with a diagnosis of diabetes mellitus had lower odds of having AD. Age, race/ethnicity, depression, stroke, and hypertension modified the relationship between DM and both VaD and AD. Further exploration of the relationship between DM and AD is warranted.

Magnetic Optical Microarray Imager for Diagnosing Type of Diabetes in Clinical Blood Serum Samples

Due to rapidly rising rates of diabetes and prediabetic conditions worldwide and the associated lethal complications, it is imperative to devise new diagnostic tools that reliably and directly measure insulin levels in clinical samples. Herein, we report a simple and sensitive direct imaging of insulin levels in diabetic patient samples using a surface plasmon resonance microarray imager (SPRi). To enhance sensitivity, we utilized magnetic nanoparticles (MNPs) to capture insulin from serum samples either directly or via a capture antibody immobilized on MNPs. The insulin-captured nanoparticles were allowed to bind surface insulin-antibody for detection from pixel intensity increase using a charge coupled device (CCD) built-in with the SPRi. We have compared the analytical figures-of-merit of the SPRi immunoarray on detecting insulin prepared in various percentages of serum solutions. A four parameter logistic model was used to obtain the best fit of microarray responses with insulin concentration and indicated the cooperative binding of insulin-nanoparticle conjugates to surface antibody in both the buffer insulin and the serum insulin conjugates with MNPs. The cooperativity effect is attributed to the greater association of magnetic nanoparticle-bound insulin molecules with increasing concentration of insulin binding to surface antibody. This is the first report of an SPRi immunoarray to accomplish clinical diagnosis of diabetic and prediabetic conditions based on insulin levels with serum matrix effect analysis and comparison between direct and sandwich insulin assay formats.

Shared links between type 2 diabetes mellitus and Alzheimer's disease: A review

Epidemiological studies have proved that, there are pathophysiological connections between Type 2 Diabetes Mellitus (T2DM) and Alzheimer's disease (AD). Diabetic patients have higher incidences of cognitive impairment and hence they are more at the risk of developing AD. Some of the recent evidences have majorly stated the effects of insulin resistance in the disturbance of various biological processes and signaling pathways. Both hyperglycemia and hypoglycemic conditions contributes in dysfunctioning of cognitive abilities and functions. The present review summarizes the evidences which establish the possible links between the two pathologies on the account of molecular, biochemical and at histopathological level. The information regarding their interactions was collected from different databases and journals. The gathered information will clearly establish the link among the two pathologies and will be helpful in future for the development of drugs for Type 3 Diabetes.

Maternal high-fat feeding leads to alterations of brain glucose metabolism in the offspring: positron emission tomography study in a porcine model

AIMS/HYPOTHESIS

Maternal obesity negatively affects fetal development. Abnormalities in brain glucose metabolism are predictive of metabolic-cognitive disorders.

METHODS

We studied the offspring (aged 0, 1, 6, 12 months) of minipigs fed a normal vs high-fat diet (HFD), by positron emission tomography (PET) to measure brain glucose metabolism, and ex vivo assessments of brain insulin receptors (IRβ) and GLUT4.

RESULTS

At birth, brain glucose metabolism and IRβ were twice as high in the offspring of HFD-fed than control mothers. During infancy and youth, brain glucose uptake, GLUT4 and IRβ increased in the offspring of control mothers and decreased in those of HFD-fed mothers, leading to a 40-85% difference (p < 0.05), and severe glycogen depletion, lasting until adulthood.

CONCLUSIONS/INTERPRETATION

Maternal high-fat feeding leads to brain glucose overexposure during fetal development, followed by long-lasting depression in brain glucose metabolism in minipigs. These features may predispose the offspring to develop metabolic-neurodegenerative diseases.

DNA methylation dynamics in plants and mammals: overview of regulation and dysregulation

DNA methylation is a major epigenetic marking mechanism regulating various biological functions in mammals and plant. The crucial role of DNA methylation has been observed in cellular differentiation, embryogenesis, genomic imprinting and X-chromosome inactivation. Furthermore, DNA methylation takes part in disease susceptibility, responses to environmental stimuli and the biodiversity of natural populations. In plant, different types of environmental stress have demonstrated the ability to alter the archetype of DNA methylation through the genome, change gene expression and confer a mechanism of adaptation. DNA methylation dynamics are regulated by three processes de novo DNA methylation, methylation maintenance and DNA demethylation. These processes have their similarities and differences between mammals and plants. Furthermore, the dysregulation of DNA methylation dynamics represents one of the primary molecular mechanisms of developing diseases in mammals. This review discusses the regulation and dysregulation of DNA methylation in plants and mammals. Copyright © 2016 John Wiley & Sons, Ltd.

Physiological and therapeutic effects of carnosine on cardiometabolic risk and disease

Obesity, type 2 diabetes (T2DM) and cardiovascular disease (CVD) are the most common preventable causes of morbidity and mortality worldwide. They represent major public health threat to our society. Increasing prevalence of obesity and T2DM contributes to escalating morbidity and mortality from CVD and stroke. Carnosine (β-alanyl-L-histidine) is a dipeptide with anti-inflammatory, antioxidant, anti-glycation, anti-ischaemic and chelating roles and is available as an over-the-counter food supplement. Animal evidence suggests that carnosine may offer many promising therapeutic benefits for multiple chronic diseases due to these properties. Carnosine, traditionally used in exercise physiology to increase exercise performance, has potential preventative and therapeutic benefits in obesity, insulin resistance, T2DM and diabetic microvascular and macrovascular complications (CVD and stroke) as well as number of neurological and mental health conditions. However, relatively little evidence is available in humans. Thus, future studies should focus on well-designed clinical trials to confirm or refute a potential role of carnosine in the prevention and treatment of chronic diseases in humans, in addition to advancing knowledge from the basic science and animal studies.

Emerging applications of metabolomics in drug discovery and precision medicine

Metabolomics is an emerging 'omics' science involving the comprehensive characterization of metabolites and metabolism in biological systems. Recent advances in metabolomics technologies are leading to a growing number of mainstream biomedical applications. In particular, metabolomics is increasingly being used to diagnose disease, understand disease mechanisms, identify novel drug targets, customize drug treatments and monitor therapeutic outcomes. This Review discusses some of the latest technological advances in metabolomics, focusing on the application of metabolomics towards uncovering the underlying causes of complex diseases (such as atherosclerosis, cancer and diabetes), the growing role of metabolomics in drug discovery and its potential effect on precision medicine.

Forxiga (dapagliflozin): Plausible role in the treatment of diabetes-associated neurological disorders

Numerous clinical and epidemiological studies have provided direct evidence to strengthen the link between type 2 diabetes (T2D) and Alzheimer's disease (AD). The possibility that T2D patients might be at increased risk in developing AD has serious societal implications. Sodium glucose co-transporter 2 (SGLT2) is one of the best targets in the treatment of diabetes, whereas acetylcholinesterase (AChE) has long been regarded as a therapeutic target for AD. This study explores the molecular interactions between AChE and SGLT2 with a new US Food and Drug Administration approved antidiabetic drug Forxiga (dapagliflozin) to explore a possible link between the treatments of AD and diabetes. Docking study was performed using "Autodock4.2." Hydrophobic and cation-π interactions play an important role in the correct positioning of dapagliflozin within the catalytic site (CAS) of SGLT2 and AChE enzymes to permit docking. Free energy of binding (ΔG) of "dapagliflozin-SGLT2" and "dapagliflozin-CAS domain of AChE" interactions was found to be -6.25 and -6.28 kcal/mol, respectively. Hence, dapagliflozin might act as a potent dual inhibitor of SGLT2 and AChE. The results described herein may form the basis of future dual therapy against diabetes-associated neurological disorders.

Diabetes is associated with cerebrovascular but not Alzheimer's disease neuropathology

INTRODUCTION

The relationship of diabetes to specific neuropathologic causes of dementia is incompletely understood.

METHODS

We used logistic regression to evaluate the association between diabetes and infarcts, Braak neurofibrillary tangle stage, and neuritic plaque score in 2365 autopsied persons. In a subset of >1300 persons with available cognitive data, we examined the association between diabetes and cognition using Poisson regression.

RESULTS

Diabetes increased odds of brain infarcts (odds ratio [OR] = 1.57, P < .0001), specifically lacunes (OR = 1.71, P < .0001), but not Alzheimer's disease neuropathology. Diabetes plus infarcts was associated with lower cognitive scores at end of life than infarcts or diabetes alone, and diabetes plus high level of Alzheimer's neuropathologic changes was associated with lower mini-mental state examination scores than the pathology alone.

DISCUSSION

This study supports the conclusions that diabetes increases the risk of cerebrovascular but not Alzheimer's disease pathology, and at least some of diabetes' relationship to cognitive impairment may be modified by neuropathology.

Glucose Transporters at the Blood-Brain Barrier: Function, Regulation and Gateways for Drug Delivery

Glucose transporters (GLUTs) at the blood-brain barrier maintain the continuous high glucose and energy demands of the brain. They also act as therapeutic targets and provide routes of entry for drug delivery to the brain and central nervous system for treatment of neurological and neurovascular conditions and brain tumours. This article first describes the distribution, function and regulation of glucose transporters at the blood-brain barrier, the major ones being the sodium-independent facilitative transporters GLUT1 and GLUT3. Other GLUTs and sodium-dependent transporters (SGLTs) have also been identified at lower levels and under various physiological conditions. It then considers the effects on glucose transporter expression and distribution of hypoglycemia and hyperglycemia associated with diabetes and oxygen/glucose deprivation associated with cerebral ischemia. A reduction in glucose transporters at the blood-brain barrier that occurs before the onset of the main pathophysiological changes and symptoms of Alzheimer's disease is a potential causative effect in the vascular hypothesis of the disease. Mutations in glucose transporters, notably those identified in GLUT1 deficiency syndrome, and some recreational drug compounds also alter the expression and/or activity of glucose transporters at the blood-brain barrier. Approaches for drug delivery across the blood-brain barrier include the pro-drug strategy whereby drug molecules are conjugated to glucose transporter substrates or encapsulated in nano-enabled delivery systems (e.g. liposomes, micelles, nanoparticles) that are functionalised to target glucose transporters. Finally, the continuous development of blood-brain barrier in vitro models is important for studying glucose transporter function, effects of disease conditions and interactions with drugs and xenobiotics.

The A-B-C for SORting APP

This Editorial highlights a study by Hermey and colleagues in the current issue of Journal of Neurochemistry. In their study, the authors provide novel insights into single-nucleotide polymorphisms associated with Alzheimer's disease and linked to the SorCS1 gene, toward a better understanding of the interaction of sorting receptor proteins which physically interact with the amyloid-beta protein precursor (APP). SorCS1, sortilin-related VPS10 domain-containing receptor 1; SorLA, sortilin-related Receptor with A-type Repeats. Read the full article 'SorCS1 variants and amyloid precursor protein (APP) are co-transported in neurons but only SorCS1c modulates anterograde APP transport' on page 60.

Lipoic acid improves neuronal insulin signalling and rescues cognitive function regulating VGlut1 expression in high-fat-fed rats: Implications for Alzheimer's disease

The concept of central insulin resistance and dysfunctional insulin signalling in sporadic Alzheimer's disease (AD) is now widely accepted and diabetes is recognized as one of the main risk factors for developing AD. Moreover, some lines of evidence indicated that VGlut1 is impaired in frontal regions of AD patients and this impairment is correlated with the progression of cognitive decline in AD. The present work hypothesizes that ketosis associated to insulin resistance could interfere with the normal activity of VGlut1 and its role in the release of glutamate in the hippocampus, which might ultimately lead to cognitive deficits. High fat diet (HFD) rats showed memory impairments and both peripheral (as shown by increased fasting plasma insulin levels and HOMA index) and hippocampal (as shown by decreased activation of insulin receptor, IRS-1 and pAkt) insulin pathway alterations, accompanied by increased ketone bodies production. All these effects were counteracted by α-lipoic acid (LA) administration. VGlut1 levels were significantly decreased in the hippocampus of HFD rats, and this decrease was reversed by LA. Altogether, the present results suggest that HFD induced alterations in central insulin signalling could switch metabolism to produce ketone bodies, which in turn, in the hippocampus, might lead to a decreased expression of VGlut1, and therefore to a decreased release of glutamate and hence, to the glutamatergic deficit described in AD. The ability of LA treatment to prevent the alterations in insulin signalling in this model of HFD might represent a possible new therapeutic target for the treatment of AD.