Does diabetes protect or provoke Alzheimer's disease? Insights into the pathobiology and future treatment of Alzheimer's disease

Caffeic Acid Phenethyl Ester Effects: In Silico Study of its Osteoimmunological Mechanisms

Background:

Biological system complexity impedes the drug target identification by biological experiments. Thus drugs, rather than acting on target site only, can interact with the entire biological system. Study of this phenomenon, known as network pharmacology, provides grounds for biological target identification of new drugs or acts as a foundation for the discovery of new targets of present drugs. No publication is available on the interaction network of CAPE.

Aim:

This study was aimed at the investigation of the candidate targets and possible interactions of caffeic acid phenethyl ester (CAPE) involved in its osteoimmunological effects.

Methods:

This study encompasses the investigation of candidate targets and possible interactions of CAPE by analyzing through PASS Prediction and constructing a biological network of CAPE.

Results:

In response to input (CAPE), PASS Prediction generated a network of 1723 targets. While selecting the probability to be active (Pa) value greater than 0.7 brought forth only 27 targets for CAPE. Most of these targets predicted the therapeutic role of CAPE as an osteoimmunological agent. Apart from this, this network pharmacology also identified 10 potential anti-cancer targets for CAPE, out of which 7 targets have been used efficiently in developing potent osteoimmunological drugs.

Conclusion:

This study provides scientific prediction of the mechanisms involved in osteoimmunological effects of CAPE, presenting its promising use in the development of a natural therapeutic agent for the pharmaceutical industry. CAPE targets identified by web-based online databases and network pharmacology need additional in silico assessment such as docking and MD simulation studies and experimental verification to authenticate these results.

Palm Fruit Bioactives augment expression of Tyrosine Hydroxylase in the Nile Grass Rat basal ganglia and alter the colonic microbiome

Tyrosine hydroxylase (TH) catalyzes the hydroxylation of L-tyrosine to L-DOPA. This is the rate-limiting step in the biosynthesis of the catecholamines - dopamine (DA), norepinephrine (NE), and epinephrine (EP). Catecholamines (CA) play a key role as neurotransmitters and hormones. Aberrant levels of CA are associated with multiple medical conditions, including Parkinson's disease. Palm Fruit Bioactives (PFB) significantly increased the levels of tyrosine hydroxylase in the brain of the Nile Grass rat (NGR), a novel and potentially significant finding, unique to PFB among known botanical sources. Increases were most pronounced in the basal ganglia, including the caudate-putamen, striatum and substantia nigra. The NGR represents an animal model of diet-induced Type 2 Diabetes Mellitus (T2DM), exhibiting hyperglycemia, hyperinsulinemia, and insulin resistance associated with hyperphagia and accelerated postweaning weight gain induced by a high-carbohydrate diet (hiCHO). The PFB-induced increase of TH in the basal ganglia of the NGR was documented by immuno-histochemical staining (IHC). This increase in TH occurred equally in both diabetes-susceptible and diabetes-resistant NGR fed a hiCHO. PFB also stimulated growth of the colon microbiota evidenced by an increase in cecal weight and altered microbiome.  The metabolites of colon microbiota, e.g. short-chain fatty acids, may influence the brain and behavior significantly.

Iron Deposition Leads to Hyperphosphorylation of Tau and Disruption of Insulin Signaling

Iron deposition in the brain is an early issue in Alzheimer's disease (AD). However, the pathogenesis of iron-induced pathological changes in AD remains elusive. Insulin resistance in brains is an essential feature of AD. Previous studies determined that insulin resistance is involved in the development of pathologies in AD. Tau pathology is one of most important hallmarks in AD and is associated with the impairment of cognition and clinical grades of the disease. In the present study, we observed that ferrous (Fe²⁺) chloride led to aberrant phosphorylation of tau, and decreased tyrosine phosphorylation levels of insulin receptor β (IRβ), insulin signal substrate 1 (IRS-1) and phosphoinositide 3-kinase p85α (PI3K p85α), in primary cultured neurons. In the in vivo studies using mice with supplemented dietary iron, learning and memory was impaired. As well, hyperphosphorylation of tau and disrupted insulin signaling in the brain was induced in iron-overloaded mice. Furthermore, in our in vitro work we identified the activation of insulin signaling following exogenous supplementation of insulin. This was further attenuated by iron-induced hyperphosphorylation of tau in primary neurons. Together, these data suggest that dysfunctional insulin signaling participates in iron-induced abnormal phosphorylation of tau in AD. Our study highlights the promising role of insulin signaling in pathological lesions induced by iron overloading.

The Research on the Relationship of RAGE, LRP-1, and Aβ Accumulation in the Hippocampus, Prefrontal Lobe, and Amygdala of STZ-Induced Diabetic Rats

Diabetes mellitus (DM) has been regarded as an important risk factor for Alzheimer's disease (AD), and diabetic patients and animals have shown cognitive dysfunction. More research has shown that the amyloid-β (Aβ), which is a hallmark of AD, was found deposited in the hippocampus of diabetic rats. This Aβ accumulation is regulated by the receptor for advanced glycation end products (RAGE) and low-density lipoprotein receptor-related protein (LRP-1). However, the expression of RAGE and LRP-1 in diabetic rats is not very clear. In the present study, we used streptozotocin (STZ)-induced diabetic rats to investigate whether the expression of RAGE and LRP-1 is related to Aβ_1-42 deposition at the hippocampus, prefrontal lobe, and amygdala in DM. We found that diabetic rats had longer escape latency and less frequency of entrance into the target zone than that of the control group (P < 0.05) in the Morris water maze (MWM) test. The Aβ_1-42 expression in the hippocampus and prefrontal lobe significantly increased in the DM group compared to the control group (P < 0.05). RAGE increased (P < 0.05), while LRP-1 decreased (P < 0.05) in the hippocampus tissue and prefrontal lobe tissue of DM rats. The Aβ_1-42 deposition was correlated with RAGE positively (P < 0.05), but with LRP-1 negatively (P < 0.05). Further, the expression levels of Aβ_1-42, RAGE, and LRP-1 were not changed in the amygdala between the diabetic rats and the control group. These findings indicated that upregulating RAGE and/or downregulating LRP-1 at the hippocampus and the prefrontal lobe contributed to the Aβ_1-42 accumulation and then further promoted the cognitive impairment of diabetic rats.

Diabetes, Hemoglobin A1C, and Regional Alzheimer Disease and Infarct Pathology

We examined the relationship of diabetes and hemoglobin A1C (A1C) to 2 common causes of dementia. The study included 1228 subjects who underwent annual clinical evaluations and a brain autopsy at death, as part of a Rush longitudinal cohort study of aging. A total of 433 subjects had A1C data available. Neuropathologic evaluations documented the size and location of infarcts. Modified silver stain-based Alzheimer disease (AD) measures included global and regional scores. We used regression analyses to examine associations of diabetes and A1C with overall and regional neuropathology. Diabetes [odds ratio (OR)=0.94; 95% confidence interval (CI), 0.73-1.20) and A1C (OR=0.83; 95% CI, 0.62-1.10) were not associated with global AD pathology across the brain, nor with overall or individual measures of neuropathology in mesial temporal or neocortical regions separately (all P>0.05). Diabetes was associated with a higher odds of any infarct (OR=1.43; 95% CI, 1.07-1.90), and particularly with gross (OR=1.53; 95% CI, 1.14-2.06) but not microinfarcts (P=0.06), and subcortical (OR=1.79; 95% CI, 1.34-2.39) but not cortical infarcts (P=0.83). In summary, we found no relationship of diabetes or A1C with global or regional AD pathology, including in the mesial temporal lobe. Diabetes is associated with gross subcortical infarcts. Our results suggest that the diabetes-dementia link is based on subcortical vascular pathology and not on regional AD pathology.

High dietary advanced glycation end products are associated with poorer spatial learning and accelerated Aβ deposition in an Alzheimer mouse model

There is growing evidence of the involvement of advanced glycation end products (AGEs) in the pathogenesis of neurodegenerative processes including Alzheimer's disease (AD) and their function as a seed for the aggregation of Aβ, a hallmark feature of AD. AGEs are formed endogenously and exogenously during heating and irradiation of foods. We here examined the effect of a diet high in AGEs in the context of an irradiated diet on memory, insoluble Aβ₄₂, AGEs levels in hippocampus, on expression of the receptor for AGEs (RAGE), and on oxidative stress in the vasculature. We found that AD‐like model mice on high‐AGE diet due to irradiation had significantly poorer memory, higher hippocampal levels of insoluble Aβ₄₂ and AGEs as well as higher levels of oxidative stress on vascular walls, compared to littermates fed an isocaloric diet. These differences were not due to weight gain. The data were further supported by the overexpression of RAGE, which binds to Aβ₄₂ and regulates its transport across the blood–brain barrier, suggesting a mediating pathway. Because exposure to AGEs can be diminished, these insights provide an important simple noninvasive potential therapeutic strategy for alleviating a major lifestyle‐linked disease epidemic.

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.

Role of insulin resistance in Alzheimer's disease

A critical role of insulin resistance (IR) in Alzheimer's disease (AD) includes beta-amyloid (Aβ) production and accumulation, the formation of neurofibrillary tangles (NFTs), failure of synaptic transmission and neuronal degeneration. Aβ is sequentially cleavaged from APP by two proteolytic enzymes: β-secretase and γ-secretase. IR could regulate Aβ production via enhancing β- and γ-secretase activity. Meanwhile, IR induces oxidative stress and inflammation in the brain which contributes to Aβ and tau pathology. Aβ accumulation can enhance IR through Aβ-mediated inflammation and oxidative stress. IR is a possible linking between amyloid plaques and NFTs pathology via oxidative stress and neuroinflammation. Additionally, IR could disrupt acetylcholine activity, and accelerate axon degeneration and failures in axonal transport, and lead to cognitive impairment in AD. Preclinical and clinical studies have supported that insulin could be useful in the treatment of AD. Thus, an effective measure to inhibit IR may be a novel drug target in AD.

Real-time effects of insulin-induced hypoglycaemia on hippocampal glucose and oxygen

The hippocampus plays a vital role in learning and memory and is susceptible to damage following hypoglycaemic shock. The effect of an acute administration of insulin on hippocampal function has been described in terms of behavioural deficits but its effect on hippocampal oxygen and glucose is unclear. Glucose oxidase biosensors (detecting glucose) and carbon paste electrodes (detecting oxygen) were implanted into the hippocampus of Sprague Dawley rats. Animals were allowed to recover and real-time recordings were made in order to determine the effects of fasting, insulin administration (15 U/kg; i.p.) and reintroduction of food on hippocampal oxygen and glucose. Fasting caused a significant decrease in hippocampal glucose over the course of 24h. Insulin administration produced a significant decrease in hippocampal glucose along with a significant increase in hippocampal oxygen. Finally, the reintroduction of food resulted in glucose levels significantly increasing along with a transient but significant increase in oxygen levels. The findings presented here suggest that even a single acute period of hypoglycaemia may substantially disrupt hippocampal oxygen and glucose and therefore affect hippocampal function.

Abdominal Obesity Associated with Elevated Serum Butyrylcholinesterase Activity, Insulin Resistance and Reduced High Density Lipoprotein-Cholesterol Levels

Abdominal obesity (AO) has a strong correlation with cardiovascular disease and has been linked to Alzheimer's disease and type 2 diabetes. We investigated the association between AO and elevated serum butyrylcholinesterase (BChE) activity, insulin resistance and the serum lipid profile, including triglyceride (TG), HDL-cholesterol (HDL-C) and LDL-cholesterol (LDL-C) levels in AO and non-AO women subjects. A total of 500 AO subjects (age 49.1 ± 10.5 years), and 142 non-AO women subjects (age 49.9 ± 11.9 years) were enrolled for the general biochemistry tests, serum BChE, fasting insulin and homeostasis model assessment of insulin resistance (HOMA-IR). Body mass index, waist circumference, Blood pressure (BP), plasma glucose (Glu), triglyceride (TG), BChE, insulin, HOMA-IR were significantly higher and HDL-C levels were significantly lower in AO subjects (p < 0.05). Waist circumference was significantly correlated with BP, Glu, TG, BChE, insulin and HOMA-IR in AO subjects. Multiple logistic regression demonstrated that AO was associated with elevated BChE, HOMA-IR, hypertension and reduced HDL-C after adjusting for these variables. AO is associated with elevated BChE, insulin resistance, HT and reduced HDL-C. These may predict the development of type 2 diabetes mellitus and may be associated with cognitive disorder in the future, both are mediated through insulin resistance.

Young-onset dementia

Young-onset dementia is a neurologic syndrome that affects behavior and cognition of patients younger than 65 years of age. Although frequently misdiagnosed, a systematic approach, reliant upon attainment of a detailed medical history, a collateral history, neuropsychological testing, laboratory studies, and neuroimaging, may facilitate earlier and more accurate diagnosis with subsequent intervention. The differential diagnosis of young-onset dementia is extensive and includes early-onset forms of adult neurodegenerative conditions including Alzheimer's disease, vascular dementia, frontotemporal dementia, Lewy body dementias, Huntington's disease, and prion disease. Late-onset forms of childhood neurodegenerative conditions may also present as young-onset dementia and include mitochondrial disorders, lysosomal storage disorders, and leukodystrophies. Potentially reversible etiologies including inflammatory disorders, infectious diseases, toxic/metabolic abnormalities, transient epileptic amnesia, obstructive sleep apnea, and normal pressure hydrocephalus also represent important differential diagnostic considerations in young-onset dementia. This review will present etiologies, diagnostic strategies, and options for management of young-onset dementia with comprehensive summary tables for clinical reference.

Physical activity and brain function in older adults at increased risk for Alzheimer's disease

Leisure-time physical activity (PA) and exercise training are known to help maintain cognitive function in healthy older adults. However, relatively little is known about the effects of PA on cognitive function or brain function in those at increased risk for Alzheimer's disease through the presence of the apolipoproteinE epsilon4 (APOE-ε4) allele, diagnosis of mild cognitive impairment (MCI), or the presence of metabolic disease. Here, we examine the question of whether PA and exercise interventions may differentially impact cognitive trajectory, clinical outcomes, and brain structure and function among individuals at the greatest risk for AD. The literature suggests that the protective effects of PA on risk for future dementia appear to be larger in those at increased genetic risk for AD. Exercise training is also effective at helping to promote stable cognitive function in MCI patients, and greater cardiorespiratory fitness is associated with greater brain volume in early-stage AD patients. In APOE-ε4 allele carriers compared to non-carriers, greater levels of PA may be more effective in reducing amyloid burden and are associated with greater activation of semantic memory-related neural circuits. A greater research emphasis should be placed on randomized clinical trials for exercise, with clinical, behavioral, and neuroimaging outcomes in people at increased risk for AD.

Consequences of Aberrant Insulin Regulation in the Brain: Can Treating Diabetes be Effective for Alzheimer's Disease

There is an urgent need for new ways to treat Alzheimer’s disease (AD), the most common cause of dementia in the elderly. Current therapies are modestly effective at treating the symptoms, and do not significantly alter the course of the disease. Over the years, a range of epidemiological and experimental studies have demonstrated interactions between diabetes mellitus and AD. As both diseases are leading causes of morbidity and mortality in the elderly and are frequent co-morbid conditions, it has raised the possibility that treating diabetes might be effective in slowing AD. This is currently being attempted with drugs such as the insulin sensitizer rosiglitazone. These two diseases share many clinical and biochemical features, such as elevated oxidative stress, vascular dysfunction, amyloidogenesis and impaired glucose metabolism suggesting common pathogenic mechanisms. The main thrust of this review will be to explore the evidence from a pathological point of view to determine whether diabetes can cause or exacerbate AD. This was supported by a number of animal models of AD that have been shown to have enhanced pathology when diabetic conditions were induced. The one drawback in linking diabetes and insulin to AD has been the postmortem studies of diabetic brains demonstrating that AD pathology was not increased; in fact decreased pathology has often been reported. In addition, diabetes induces its own distinct features of neuropathology different from AD. There are common pathological features to be considered including vascular abnormalities, a major feature arising from diabetes; there is increasing evidence that vascular abnormalities can contribute to AD. The most important common mechanism between insulin-resistant (type II) diabetes and AD could be impaired insulin signaling; a form of toxic amyloid can damage neuronal insulin receptors and affect insulin signaling and cell survival. It has even been suggested that AD could be considered as “type 3 diabetes” since insulin can be produced in brain. Another common feature of diabetes and AD are increased advanced glycation endproduct-modified proteins are found in diabetes and in the AD brain; the receptor for advanced glycation endproducts plays a prominent role in both diseases. In addition, a major role for insulin degrading enzyme in the degradation of Aβ peptide has been identified. Although clinical trials of certain types of diabetic medications for treatment of AD have been conducted, further understanding the common pathological processes of diabetes and AD are needed to determine whether these diseases share common therapeutic targets.

[Changes in cognitive function in patients with diabetes mellitus]

Patients with diabetes are approximately 1.5 times more likely to experience cognitive decline than individuals without diabetes mellitus. Most of the data suggest that patients with diabetes have reduced performance in numerous domains of cognitive function. In patients with type 1 diabetes, specific and global deficits involving speed of psychomotor efficiency, information processing, mental flexibility, attention, and visual perception seem to be present, while in patients with type 2 diabetes an increase in memory deficits, a reduction in psychomotor speed, and reduced frontal lobe (executive) functions have been found. The complex pathophysiology of changes in the central nervous system in diabetes has not yet been fully elucidated. It is important to consider the patient's age at the onset of diabetes, the glycemic control status, and the presence of diabetic complications. Neurological consequences of diabetes appear parallel to those observed in the aging brain. Neuroimaging studies highlight several structural cerebral changes, cortical and subcortical atrophy, beside increased leukoaraiosis that occurs in association with diabetes. There is supporting evidence from many hypotheses to explain the pathophysiology of cognitive decline associated with diabetes. The main hypotheses pointing to the potential, implied mechanisms involve hyperglycemia, hypoglycemia, microvascular disease, insulin resistance, hyperinsulinism, hyperphosphorylation of tau protein, and amyloid-β deposition.

Metabolic syndrome as a risk factor for neurological disorders

The metabolic syndrome is a cluster of common pathologies: abdominal obesity linked to an excess of visceral fat, insulin resistance, dyslipidemia and hypertension. At the molecular level, metabolic syndrome is accompanied not only by dysregulation in the expression of adipokines (cytokines and chemokines), but also by alterations in levels of leptin, a peptide hormone released by white adipose tissue. These changes modulate immune response and inflammation that lead to alterations in the hypothalamic 'bodyweight/appetite/satiety set point,' resulting in the initiation and development of metabolic syndrome. Metabolic syndrome is a risk factor for neurological disorders such as stroke, depression and Alzheimer's disease. The molecular mechanism underlying the mirror relationship between metabolic syndrome and neurological disorders is not fully understood. However, it is becoming increasingly evident that all cellular and biochemical alterations observed in metabolic syndrome like impairment of endothelial cell function, abnormality in essential fatty acid metabolism and alterations in lipid mediators along with abnormal insulin/leptin signaling may represent a pathological bridge between metabolic syndrome and neurological disorders such as stroke, Alzheimer's disease and depression. The purpose of this review is not only to describe the involvement of brain in the pathogenesis of metabolic syndrome, but also to link the pathogenesis of metabolic syndrome with neurochemical changes in stroke, Alzheimer's disease and depression to a wider audience of neuroscientists with the hope that this discussion will initiate more studies on the relationship between metabolic syndrome and neurological disorders.

Targeting amyloid-beta by glucagon-like peptide -1 (GLP-1) in Alzheimer's disease and diabetes

INTRODUCTION

Epidemiological evidence suggests an association between type 2 diabetes (T2DM) and Alzheimer's disease (AD), in that one disease increases the risk of the other. T2DM and AD share several molecular processes which underlie the tissue degeneration in either disease. Disturbances in insulin signaling may be the link between the two conditions. Drugs originally developed for T2DM are currently being considered as possible novel agents in the treatment of AD.

AREAS COVERED

This review discusses the potential role of glucagon-like peptide -1 (GLP-1) treatment in AD. GLP-1 receptors are expressed in areas of the brain important to memory and learning, and GLP-1 has growth-factor-like properties similar to insulin. A key neuropathological feature of AD is the accumulation of amyloid-beta (Aβ). In preclinical studies, GLP-1 and longer lasting analogues have been shown to have both neuroprotective and neurotrophic effects, and to protect synaptic activity in the brain from Aβ toxicity.

EXPERT OPINION

A convincing amount of evidence has shown a beneficial effect of GLP-1 agonist treatment on cognitive function, memory and learning in experimental models of AD. GLP-1 analogues may therefore be the new therapeutic agent of choice for intervention in AD.

Differences in the body composition and biochemistry in women grouped as normal-weight, overweight and obese according to body mass index and their relation with cardiometabolic risk

Morbidity of obesity-related diseases tends to increase due to a rise in the body mass index (BMI). We aimed to investigate how the body composition and biochemical parameters change while BMI increases in adult women were categorized as so: as normal weight, overweight and obese. Our objectives are to study the effects of those changes in the development of metabolic disturbances and to find out which parameters are the most sensitive to predict cardiometabolic risks. Three hundred and twenty two records of adult women (mean age: 38.62±12.71 year) who admitted to our unit concerning about losing or preserving their weights, were analyzed in the study. All patients had undergone anthropometric measurements and body composition analyses as well as some biochemical tests. Body composition analyses were performed by means of the Bioelectrical Impedance Analyzer (BIA). Increase in BMI significantly increased the body fat, blood sugar, insulin, triglyceride and uric acid levels. BMI and circumference of the waist were significantly and negatively correlated with the ratio of body water and lean mass/fat mass. However they were positively correlated with the ratio of fat mass and basal metabolism. Furthermore, it was also found that BMI and circumference of the waist were significantly and positively correlated with level of fasting blood sugar, insulin, triglyceride, homeostasis model assessment insulin resistance (HOMA-IR), uric acid and fibrinogen levels, and negatively correlated with high density lipoprotein (HDL) cholesterol level. In multiple regression analyses, circumference of waist measurements was significantly correlated with insulin, triglyseride and HDL, whereas the correlation between BMI and these parameters was not found significant. Total body fat mass (as %) showed significant correlation only with HDL-C level. It could be said that obesity which is a disorder that causes many health complications and affects the quality of life in the short and long term could be prevented or cured by keeping negative environmental conditions under control. According to our results, visceral adipose tissue (VAT) measurement was thought to be more related for metabolic and cardiovascular disorders rather than BMI. We also propose to test fasting blood glucose, insulin, triglyceride, HDL, fibrinogen, homocystein (HOM) levels along with VAT measurements to predict more truly about not only global cardiometabolic risk but also dementia in later life.

Butyrylcholinesterase in metabolic syndrome

Butyrylcholinesterase may have a role in a number of metabolic functions and could affect the expression of insulin resistance syndrome. We present our integrated work using clinical, biochemical and bioinformatic approaches to delineate the possible function of this enzyme. Initially, we constructed a phylogenic tree with nucleotides and amino acid sequences and showed the existence of similar sequences in bacteria, plants and in other animals. We also demonstrated a possible pathogenic role for BChE in the common existence of insulin resistance, type 2 diabetes and Alzheimer's disease by in silico method and followed it up with a diabetic mouse study where cognition was slowed along with changes in BChE levels. In the next group of in silico studies, we employed THEMATICS method to identify the amino acids at the active site and later performed docking studies with drugs. THEMATICS predicted two clusters of ionisable amino acid residues that are in proximity: one with two residues and another with 11 showed perturbation in the THEMATICS curves. Using ISIS/Draw 2.5SP4, ARGUSLAB 4.0.1 and HEX 5.1. software. 3-D ligands were docked with BChE motif (from PDB). We did not find any of the ligands studied with significant docking distance, indicating they did not have direct interaction with the active site. Subsequently we performed in silico studies to compare the secondary structure and domain of BChE. Protein-protein interaction showed the following intersections with BChE UBE21, CHAT, APOE, AATF, DF ALDH9A1, PDHX, PONI PSME3 and ATP6VOA2. The integrative physiological roles of proteins with poorly known functions can be approached by generating leads in silico, which can be studied in vivo, setting into movement an iterative process.

Roles of cholesterol and lipids in the etiopathogenesis of Alzheimer's disease

Alzheimer's disease is the principal cause of dementia throughout the world and the fourth cause of death in developed economies.This brain disorder is characterized by the formation of brain protein aggregates, namely, the paired helical filaments and senile plaques. Oxidative stress during life, neuroinflamamtion, and alterations in neuron-glia interaction patterns have been also involved in the etiopathogenesis of this disease. In recent years, cumulative evidence has been gained on the involvement of alteration in neuronal lipoproteins activity, as well as on the role of cholesterol and other lipids in the pathogenesis of this neurodegenerative disorder. In this review, we analyze the links between changes in cholesterol homeostasis, and the changes of lipids of major importance for neuronal activity and Alheimer's disease. The investigation on the fine molecular mechanisms underlying the lipids influence in the etiopathogenesis of Alzheimer's disease may shed light into its treatment and medical management.

Beta amyloid and hyperphosphorylated tau deposits in the pancreas in type 2 diabetes

Strong epidemiologic evidence suggests an association between Alzheimer disease (AD) and type 2 diabetes. To determine if amyloid beta (Abeta) and hyperphosphorylated tau occurs in type 2 diabetes, pancreas tissues from 21 autopsy cases (10 type 2 diabetes and 11 controls) were analyzed. APP and tau mRNAs were identified in human pancreas and in cultured insulinoma beta cells (INS-1) by RT-PCR. Prominent APP and tau bands were detected by Western blotting in pancreatic extracts. Aggregated Abeta, hyperphosphorylated tau, ubiquitin, apolipoprotein E, apolipoprotein(a), IB1/JIP-1 and JNK1 were detected in Langerhans islets in type 2 diabetic patients. Abeta was co-localized with amylin in islet amyloid deposits. In situ beta sheet formation of islet amyloid deposits was shown by infrared microspectroscopy (SIRMS). LPS increased APP in non-neuronal cells as well. We conclude that Abeta deposits and hyperphosphorylated tau are also associated with type 2 diabetes, highlighting common pathogenetic features in neurodegenerative disorders, including AD and type 2 diabetes and suggesting that Abeta deposits and hyperphosphorylated tau may also occur in other organs than the brain.

Risk factors for dementia in the epidemiological study of Munguialde County (Basque Country-Spain)

BACKGROUND

Prevalence of degenerative dementias and dementias associated with cerebrovascular disease is increasing. Dementia is one of the most significant public health problem. In recent years, the role of vascular risk factors (hypertension, diabetes mellitus and hypercholesterolemia) and depression has been evaluated.The incidence of dementia and risk factors has not been fully investigated in Spain. The aim of this study was to identify the risk factors for dementia, Alzheimer's disease (AD) and vascular dementia (VD) in elderly people in Munguialde County (Spain).

METHODS

A two phase, door-to-door populational study was performed. Demographic variables and the presence of vascular risk factors and depression were recorded. The MMSE, the DSM-IV and the conventional criteria for AD and VD were used in the evaluation. The odds ratio for each risk factor was calculated by logistic regression analysis.

RESULTS

1756 healthy subjects and 175 patients with dementia participated in the study. Of these, 133 had AD, 15 VD and the remainder other dementias. The risk factors for dementia and AD were female sex (OR = 1.67 and 1.97, respectively); age (OR = 1.14 and 1.15); stroke (OR = 7.84 and 3); and depression (OR = 53.08 and 3.19). Stroke was the only risk factor for VD (OR = 119).

CONCLUSION

Greater age, female sex, stroke and depression increase the risk of suffering dementia, AD and VD. The relationship between depression, vascular risk factors and dementia has clear public health implications. Prevention and early treatment of vascular risk factors and depression may have an important impact in lowering the risk of dementia and could modify the natural history of the disease.

Alzheimer's disease and type 2 diabetes mellitus: the cholinesterase connection?

Alzheimer's disease and type 2 diabetes mellitus tend to occur together. We sought to identify protein(s) common to both conditions that could suggest a possible unifying pathogenic role. Using human neuronal butyrylcholinesterase (AAH08396.1) as the reference protein we used BLAST Tool for protein to protein comparison in humans. We found three groups of sequences among a series of 12, with an E-value between 0–12, common to both Alzheimer's disease and diabetes: butyrylcholinesterase precursor K allele (NP_000046.1), acetylcholinesterase isoform E4-E6 precursor (NP_000656.1), and apoptosis-related acetylcholinesterase (1B41|A). Butyrylcholinesterase and acetylcholinesterase related proteins were found common to both Alzheimer's disease and diabetes; they may play an etiological role via influencing insulin resistance and lipid metabolism.

Lutein effect on retina and hippocampus of diabetic mice

Oxidative stress markers and functional tests were studied to confirm early biochemical and functional changes in retina and hippocampus of diabetic mice. The effects of lutein treatment were also tested. Mice were induced diabetic by alloxan injection and divided into subgroups: control, control+lutein, diabetic, diabetic+lutein, diabetic+insulin, and diabetic+insulin+lutein. Treatments started on Day 4 after alloxan injection and animals were sacrificed on Day 14. Malondialdehyde and glutathione concentrations and glutathione peroxidase activity were measured as oxidative stress markers. The following functional tests for retina and hippocampus were performed: electroretinogram and Morris water maze test. NFkappaB activity was also measured. Oxidative stress and NFkappaB activity increase in the retina and hippocampus after 15 days of diabetes. Impairment of the electroretinogram and a correlation between latencies of the water maze test and glycated hemoglobin (HbA1c) levels were observed. Lutein prevented all these changes even under hyperglycemic conditions. Retina appears to be affected earlier than hippocampus by diabetes-induced oxidative stress. Although a proper glycemic control is desirable in preventing the development of diabetic complications, it is not sufficient to prevent them completely. Lutein could be an appropriate coadjuvant treatment for the changes observed in this study.

Concurrent alterations of O-GlcNAcylation and phosphorylation of tau in mouse brains during fasting

Impaired brain glucose uptake/metabolism precedes the symptoms of Alzheimer disease (AD) and is likely to play a role in the development of the disease, but the mechanism by which it contributes to AD is not understood. Because glucose uptake/metabolism regulates protein O-GlcNAcylation, and the latter modulates phosphorylation of tau inversely, we investigated, in fasting Kunming mice, whether impaired brain glucose uptake/metabolism causes abnormal hyperphosphorylation of tau and, consequently, facilitates the neurofibrillary degeneration of AD via down-regulation of tau O-GlcNAcylation. We found that fasting caused decreased tau O-GlcNAcylation and concurrent hyperphosphorylation of tau at most of the phosphorylation sites studied. The hippocampus was found more vulnerable to the tau alterations than the cerebral cortex, which is consistent with the fact that it is the hippocampus that is first affected in AD. Furthermore, hyperphosphorylation of tau induced by fasting was reversible in the brain after re-feeding. These findings provide a novel mechanism explaining how impaired brain glucose uptake/metabolism contributes to AD and suggest that it may be feasible to treat AD by reversing the abnormal hyperphosphorylation of tau at early stages of the disease.

Coordination of ER and oxidative stress signaling: the PERK/Nrf2 signaling pathway

In the broadest sense, cellular stress describes conditions wherein cells encounter and react to a 'non-normal' state. Perturbations may originate through both extracellular and intracellular means. Whereas transient levels of stress are expected to occur on a regular basis, a series of checks and balances ensures that cells are well equipped to maintain a homeostatic state. In the case of supra-physiological stress signaling, cellular challenges are more severe, and programmed cell death may be the best option for the organism. The ability of a cell, and by extension, an organism, to adequately manage cellular stress is fundamental--a question of life or death. The endoplasmic reticulum (ER) is exquisitely poised to sense and respond to cellular stresses including those that result from metabolic and/or protein folding imbalances. In response to stress originating from within the ER, the PERK and Ire1 protein kinases, along with other proximal signaling molecules, initiate a program of transcriptional and translational regulation termed the unfolded protein response. A consequence of ER stress is the accumulation of reactive oxygen species that promotes a state of oxidative stress. PERK signaling, via activation of the Nrf2 and ATF4 transcription factors, coordinates the convergence of ER stress with oxidative stress signaling. Here we discuss progress regarding the signaling pathways involved in these cellular stresses and the implications of the intersection between the two signaling pathways.

Insulin-degrading enzyme as a downstream target of insulin receptor signaling cascade: implications for Alzheimer's disease intervention

Insulin-degrading enzyme (IDE) is one of the proteins that has been demonstrated to play a key role in degrading beta-amyloid (Abeta) monomer in vitro and in vivo, raising the possibility of upregulating IDE as an approach to reduce Abeta. Little is known, however, about the cellular and molecular regulation of IDE protein. Because one of the main functions of IDE is to degrade insulin, we hypothesized that there is a negative feedback mechanism whereby stimulation of insulin receptor-mediated signaling upregulates IDE to prevent chronic activation of the pathway. We show that treatment of primary hippocampal neurons with insulin increased IDE protein levels by approximately 25%. Insulin treatment also led to phosphatidylinositol-3 (PI3) kinase activation evidenced by Akt phosphorylation, which was blocked by PI3 kinase inhibitors, wortmannin and LY 294002. Inhibition of PI3 kinase abolished the IDE upregulation by insulin, indicating a cause-effect relationship between insulin signaling and IDE upregulation. Further support for this link was provided by the findings that deficient insulin signaling (decreased PI3 kinase subunit P85) was correlated with reduced IDE in Alzheimer's disease (AD) brains and in Tg2576 Swedish amyloid precursor protein transgenic mice fed a safflower oil-enriched ("Bad") diet used to accelerate pathogenesis. Consistent with IDE function in the degradation of Abeta monomer, the IDE decrease in the Bad diet-fed Tg2576 mice was associated with increased Abeta monomer levels. These in vitro and in vivo analyses validate the use of enhanced CNS insulin signaling as a potential strategy for AD intervention to correct the IDE defects occurring in AD.

Future directions in the treatment of Alzheimer’s disease

Alzheimer's disease (AD) remains the most common of the neurodegenerative disorders. In the elderly, it represents the most frequently occurring form of dementia, especially if considered alongside concomitant cerebrovascular disease. Current treatment involves the use of acetylcholinesterase inhibitors, which have shown symptomatic benefits in the recognised domains of cognition, function and behaviour. While they may have intrinsic disease-modifying activity, this is yet to be proven, and strategies to alter the fundamental neuropathological changes in AD continue to be sought. Much of the evidence suggests that the accumulation of amyloid-beta may play a pivotal role, therefore the bulk of current research is focused on possible intervention along the amyloid pathways. However, the abnormal phosphorylation of tau is also a reasonable target and as the molecular basis of AD is better delineated, more targeted treatment approaches are being proposed. This paper reports on the current data that is setting the future directions for research into AD.

Diabetes and brain aging: epidemiologic evidence

Increasingly, data from epidemiologic studies suggest diabetes is a risk factor in old age for brain aging, including cognitive impairment and dementia. These associations may reflect a direct effect on the brain of hyperglycemia, or the effects of the diabetes-associated comorbidities of hypertension, dyslipidemia, or hyperinsulinemia. Epidemiologic data on diabetes and brain aging are reviewed. A brief overview is also given of the physiologic mechanisms supporting the epidemiologic data.

Integrated treatment approach improves cognitive function in demented and clinically depressed patients

The purpose of this study was to evaluate the efficacy of an integrative treatment approach on cognitive performance. The study sample comprised 35 medically ill patients (20 male, 15 female) with an average age of 71.05, who were diagnosed with mild dementia and depression. These patients were evaluated at baseline and at six, 12, and 24 months of treatment, which included antidepressants (sertraline, citalopram, or venlafaxine XR, alone or in combination with bupropion XR), cholinesterase inhibitors (donepezil, rivastigmine or galantamine), as well as vitamins and supplements (multivitamins, vitamin E, alpha-lipoic acid, omega-3 and coenzyme Q-10). Patients were encouraged to modify their diet and lifestyle and perform mild physical exercises. Results show that the integrative treatment not only protracted cognitive decline for 24 months but even improved cognition, especially memory and frontal lobe functions.