Precursor Protein mRNA Research Articles

Mitochondrial Dysregulation in Skeletal Muscle from Patients Diagnosed with Alzheimer’s Disease and Sporadic Inclusion Body Myositis

Mitochondrial dysfunction is implicated in Alzheimer’s disease (AD) and disruption of mitochondrial dynamic pathways has been documented in brains from patients diagnosed with AD; although it is unclear whether other tissues are also affected. Much less is known about the mitochondria in patients diagnosed with sporadic Inclusion Body Myositis (sIBM). The current study examined mitochondrial biology in skeletal muscle from AD and sIBM patients compared to healthy, elderly individuals. Skeletal muscle samples were obtained from the National Disease Research Interchange and mRNA, protein content, and enzyme activity was used to assess mitochondrial parameters. Patients diagnosed with AD or sIBM demonstrated reduced mitofusin 2 and optic atrophy protein 1 protein. AD patients also displayed increased mRNA of superoxide dismutase 2, catalase, and uncoupling protein 3. Amyloid b precursor protein mRNA was higher in sIBM patients only compared to both AD patients and elderly individuals. Both total and phosphorylated AMPK protein content, an upstream regulator of mitochondrial dynamics and biogenesis, were also reduced in sIBM patients. The current study demonstrates a disruption in signaling pathways regulating mitochondrial dynamics in both AD and sIBM patients, although the underlying causes may differ.

Excessive hydrogen peroxide enhances the attachment of amyloid β1–42 in the lens epithelium of UPL rats, a hereditary model for cataracts

Several studies have reported that hydrogen peroxide (H2O2) is related to the toxicity of amyloid β (Aβ), and that the accumulation of Aβ in the lenses of humans causes lens opacification. In this study, we investigate the accumulation of Aβ1–42 in the lenses of UPL rats, which then leads to lens opacification. In addition, we demonstrate the effect of disulfiram eye drops (DSF), a potent radical scavenger, on Aβ1–42 accumulation in the lenses of UPL rats. The H2O2 levels in 46- to 60-day-old UPL rat lenses are significantly higher than in normal rats, and the Aβ1–42 levels in 53- and 60-day-old UPL rats are also increased only in lens epithelium containing capsules (capsule-epithelium), not in the lens cortex and nucleus. However, no increases in amyloid precursor protein (APP), β- or γ-secretase mRNA were observed in lenses of the corresponding ages. It has been thought that Aβ1–42 that accumulates in the lenses of UPL rats is actually produced in another tissue containing neuronal cells, such as brain or retina. Aβ1–42 levels in the brain and retina rise with aging, and the levels of APP, β- and γ-secretase mRNA in the retinas of 53-day-old UPL rats with opaque lenses are significantly higher than in 25-day-old UPL rats with transparent lenses. In contrast to the results in retinas, the levels of APP, β- and γ-secretase mRNA in the brains of 25- and 53-day-old UPL rats are similar. On the other hand, in an in vitro study, Aβ1–42 attachment in the lens capsule-epithelium of UPL rats was found to increase in H2O2. In addition, in an in vivo study, the inhibition of H2O2 by DSF was found to attenuate the increase in Aβ1–42 in the lens capsule-epithelium of 60-day-old UPL rats. Taken together, we hypothesize that excessive H2O2 in the lens enhances the attachment of Aβ1–42 in the lens capsule-epithelium of UPL rats, and that the instillation of DSF has the ability to attenuate the attachment of Aβ1–42 by inhibiting H2O2 production in lens. These findings provide significant information that can be used to design further studies aimed at developing anti-cataract drugs.

P4‐225: Therapeutic action of translation blockers on expression of the amyloid precursor protein as a central ferroxidase

It is possible to repress amyloid precursor protein (APP) mRNA translation as both an anti-amyloid pharmacotherapy for Alzheimer's disease (AD) and also to tone oxidative ferroxidase activity from APP over-expression.This therapeutic model is consistent with cases where AD pathology is the genetic consequence of duplications of the APP gene. Our pharmacological goal is to reduce APP expression. The antioxidant N-acetyl cysteine selectively reduced APP translation in neural cells while maintaining compensatory APLP-1 /-2 levels, then this drug also limited Aβ production in vivo.Secondly, posiphen is the + enantiomer of the well-tested anti-cholinesterase phenserine, which entered phase II clinical trials for its capacity to limit amyloid in AD subjects via its action as an APP 5'UTR translation blocker. We screened two molecular compound libraries at Harvard and Columbia Universities. From our screens, thirteen top leads shared chemical features pertinent to potently blocking APP 5'UTR directed translation (1nM). Most of our lead APP translation blockers were found to be highly potent intercalators of the RNA stem loop folded from APP 5'untranslated region. All were planar and had either a benzimidazole, benzothiazole or benzoxazole ring in its backbone. Top APP 5'UTR inhibitors were 50-fold more potent blockers of Aβ precursor translation than NAC or posiphen. The most active lead was the ninth compound in the series, APP blocker-9 (“JTR-009”). Critically, JTR-009 effectively reduced APP levels in primary mouse E-18 cortical neurons at single nanomolar concentrations similar to serum concentrations of effective clinical drugs. JTR-009 was anti-amyloid and our calcein assays demonstrated it adjusted cellular iron content to promote cellular viability. Our top APP translation blocker, JTR-009, is a planar tricyclic benzimidazole that intercalates selectively into the single 146 base APP 5'UTR specific RNA stem loop. Confirming specificity and potency, we are checking how JTR-009 blocks ribosome scanning of the APP 5'UTR to impede translation (Aβ output) while not interacting with the 5'UTRs of APP-like protein (APLP-1/-2) mRNAs. This APP translation blocker adjusted the intrinsic levels of APP with its concomitant ferroxidase activity and iron export properties, thus to optimally promote neural cell viability.

Effects of Nerve Growth Factor and Nitric Oxide Synthase Inhibitors on Amyloid Precursor Protein mRNA Levels and Protein Stability

We determined previously that nitric oxide (NO) modulates the nerve growth factor (NGF)-mediated increases in amyloid precursor protein (APP) levels in PC12 cells. To elucidate potential mechanisms, the effects of NGF and NO synthase (NOS) inhibitors on APP mRNA levels and protein stability were evaluated. Surprisingly, treatment of PC12 cells with NGF resulted in decreased levels of APP695 and APP751/770 mRNA. Therefore, the effect of NGF on APP protein stability was examined using the translation inhibitor, cycloheximide. Under these conditions, NGF did not alter the rate of APP degradation, suggesting that NGF may be enhancing the translation rate of APP. Since NOS inhibitors attenuate the NGF-mediated increase in APP levels, their effect on APP mRNA levels and protein stability was also assessed. S-methylisothiourea (S-MIU), selective for inducible NOS, decreased both APP695 and APP751/770 mRNA levels while the non-selective NOS inhibitor, Nω-nitro-L-arginine methylester (L-NAME) had no effect. In both control and NGF-treated PC12 cells, S-MIU increased the half-life of APP, with the greatest effect observed with the APP695 isoform. Based on these data we propose that in PC12 cells, NGF increases APP levels through enhanced translation rate and that NO, which modulates the NGF-induced increase in APP protein, also regulates APP mRNA levels and could play a role in APP processing.

Compound Danshen tablets downregulate amyloid protein precursor mRNA expression in a transgenic cell model of Alzheimer's disease: Effects and a comparison with donepezil.

After gene mutation, the pcDNA3.1/APP595/596 plasmid was transfected into HEK293 cells to establish a cell model of Alzheimer's disease. The cell model was treated with donepezil or compound Danshen tablets after culture for 72 hours. Reverse transcription-PCR showed that the mRNA expression of amyloid protein precursor decreased in all groups following culture for 24 hours, and that there was no significant difference in the amount of decrease between donepezil and compound Danshen tablets. Our results suggest that compound Danshen tablets can reduce expression of the mRNA for amyloid protein precursor in a transgenic cell model of Alzheimer's disease, with similar effects to donepezil.

Obesity and neurodegeneration: effect of a Mediterranean dietary pattern

Obesity is a serious global health problem and is associated with a variety of chronic diseases. Increasing evidence suggests that obesity increases the risk of Alzheimer's disease. Several studies have shown that a Mediterranean diet is effective in reducing weight and epidemiological data suggest that such a diet is associated with lower risk of neurodegenerative disorders, including Alzheimer's disease. Therefore, we examined the relationship between obesity and neurodegeneration and the possible effects of Mediterranean diet on both in adult obese rats. Obese rats showed significant dyslipidaemia, insulin resistance, down-regulation of adiponectin mRNA expression in adipose tissue, up-regulation of brain amyloid precursor protein, apolipoprotein E and caspase-3 mRNA expression and a marked increase in brain oxidative stress. Treatment with Mediterranean diet induced significant weight loss and improvement in these various markers. The present study suggests that Mediterranean diet is a viable nutritional intervention in obesity and, more importantly, in the prevention and treatment of Alzheimer's disease.

Amyloid Precursor Protein (APP) mRNA Level is Higher in the Old Mouse Cerebral Cortex and is Regulated by Sex Steroids

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by the accumulation of amyloid beta peptides, which are produced by the proteolytic cleavage of amyloid precursor protein (APP). As the incidence of AD is higher in females and sex steroids are implicated in this disease, we have examined the effect of sex steroids (testosterone and 17β-estradiol) on the expression of APP mRNA and protein in the cerebral cortex of adult and old mice of both sexes. Northern blot analysis detected APP mRNA as a single 3.5-kb band and its level is increased in old as compared to adult. Following gonadectomy, its level was upregulated in female mice but downregulated in male mice. Supplementation with testosterone or estradiol decreased its levels in female mice of both ages. Testosterone supplementation increased the mRNA levels in both adult and old male mice. Estrogen supplementation decreased its level in adult but increased in old male mice. Western blot analysis detected APP specific bands ranging from 95 to 125 kD. The level of 95 kDa band representing APP695 protein showed difference in levels with age or hormone treatment. These results provide evidence for increase in APP mRNA level in the cerebral cortex of old mice and its regulation by sex steroids during aging.

Biochemical effect of a ketogenic diet on the brains of obese adult rats

Excess weight, particularly abdominal obesity, can cause or exacerbate cardiovascular and metabolic disease. Obesity is also a proven risk factor for Alzheimer’s disease (AD). Various studies have demonstrated the beneficial effects of a ketogenic diet (KD) in weight reduction and in modifying the disease activity of neurodegenerative disorders, including AD. Therefore, in this study we examined the metabolic and neurodegenerative changes associated with obesity and the possible neuroprotective effects of a KD in obese adult rats. Compared with obese rats fed a control diet, obese rats fed a KD showed significant weight loss, improvement in lipid profiles and insulin resistance, and upregulation of adiponectin mRNA expression in adipose tissue. In addition, the KD triggered significant downregulation of brain amyloid protein precursor, apolipoprotein E and caspase-3 mRNA expression, and improvement of brain oxidative stress responses. These findings suggest that a KD has anti-obesity and neuroprotective effects.

Iron regulatory protein 2 is involved in brain copper homeostasis

Trace metal homeostasis is tightly controlled in the brain, as even a slight dysregulation may severely impact normal brain function. This is especially apparent in Alzheimer’s disease, where brain homeostasis of trace metals such as copper and iron is dysregulated. As it is known that iron and copper metabolism are linked, we wanted to investigate if a common mechanism could explain the increase in iron and decrease in copper seen in Alzheimer’s disease brain. Amyloid precursor protein has been implicated in copper efflux from the brain. Furthermore, it was shown that iron regulatory proteins, which regulate iron homeostasis, can block amyloid precursor protein mRNA translation. In a correlative study we have therefore compared brain regional copper levels and AβPP expression in mice with a targeted deletion of iron regulatory protein 2 (IRP2−/−). Compared with controls, six week old IRP2−/− mice had significantly less brain copper in the parietal cortex, hippocampus, ventral striatum, thalamus, hypothalamus and whole brain, while amyloid precursor protein was significantly upregulated in the hippocampus (p<0.05) and showed a trend toward upregulation in the thalamus (p<0.1). This is the first study to demonstrate that iron regulatory proteins affect brain copper levels, which has significant implications for neurodegenerative diseases.

Differential effects of interleukin-1&amp;beta; and S100B on amyloid precursor protein in rat retinal neurons

Interleukin-1beta (IL-1beta) and S100B calcium binding protein B (S100B) have been implicated in the pathogenesis of Alzheimer's disease. Both are present in and around senile plaques and have been shown to increase levels of amyloid precursor protein (APP) mRNA in vitro. However, it is not known how either of these substances affects APP in vivo. We have studied the effects of IL-1beta and S100B on the expression and processing of APP using a retinal-vitreal model. We have also investigated the effect of amyloid beta peptide (Abeta) on APP in the same system and the regulation of S100B production by Abeta and IL-1beta from retinal glial cells. Retinal ganglion cells constitutively express APP. However, after intravitreal injection of IL-1beta or Abeta there was a marked reduction in APP levels as detected by Western blotting and IL-1beta produced a decrease in APP immunoreactivity (IR). Nissl staining showed that the integrity of the injected retinas was unchanged after injection. Two days after S100B injection, there was a small reduction in APP-IR but this was accompanied by the appearance of some intensely stained large ganglion cells and there was some up-regulation in APP holoprotein levels on Western blot. Seven days post-S100B injection, these large, highly stained cells had increased in number throughout the retina. Injection of Abeta and IL-1beta also caused an increase in S100B production within the retinal Müller glial cells. These results support the hypothesis that S100B (a glial-derived neurotrophic factor) and IL-1beta (a pro-inflammatory cytokine) can modulate the expression and processing of APP in vivo and so may contribute to the progression of Alzheimer's disease.

Iron and the translation of the amyloid precursor protein (APP) and ferritin mRNAs: riboregulation against neural oxidative damage in Alzheimer's disease

The essential metals iron, zinc and copper deposit near the Abeta (amyloid beta-peptide) plaques in the brain cortex of AD (Alzheimer's disease) patients. Plaque-associated iron and zinc are in neurotoxic excess at 1 mM concentrations. APP (amyloid precursor protein) is a single transmembrane metalloprotein cleaved to generate the 40-42-amino-acid Abetas, which exhibit metal-catalysed neurotoxicity. In health, ubiquitous APP is cleaved in a non-amyloidogenic pathway within its Abeta domain to release the neuroprotective APP ectodomain, APP(s). To adapt and counteract metal-catalysed oxidative stress, as during reperfusion from stroke, iron and cytokines induce the translation of both APP and ferritin (an iron storage protein) by similar mechanisms. We reported that APP was regulated at the translational level by active IL (interleukin)-1 (IL-1-responsive acute box) and IRE (iron-responsive element) RNA stem-loops in the 5' untranslated region of APP mRNA. The APP IRE is homologous with the canonical IRE RNA stem-loop that binds the iron regulatory proteins (IRP1 and IRP2) to control intracellular iron homoeostasis by modulating ferritin mRNA translation and transferrin receptor mRNA stability. The APP IRE interacts with IRP1 (cytoplasmic cis-aconitase), whereas the canonical H-ferritin IRE RNA stem-loop binds to IRP2 in neural cell lines, and in human brain cortex tissue and in human blood lysates. The same constellation of RNA-binding proteins [IRP1/IRP2/poly(C) binding protein] control ferritin and APP translation with implications for the biology of metals in AD.

Novel role of cholesterol sulfate in gene regulation during skin development

Cholesterol sulfate (CS) is prominent in the epidermis where it accumulates during skin development. Cholesterol sulfotransferase (SULT2B1b), which produces CS localizes to the granular layer of the epidermis coinciding with the highest CS content. Localization of SULT2B1b is similar to that of the barrier protein filaggrin, a late marker of keratinocyte differentiation. CS, based on crystallographic data, binds with high affinity to the retinoic acid receptor‐related orphan receptor alpha (RORα) moreover, binding translates into increased transcriptional activity. Using normal human epidermal keratinocytes (NHEK) in primary culture, CS stimulates profilaggrin (filaggrin precursor protein) mRNA expression in a dose‐dependent manner, and hypothesized that CS by binding to the nuclear receptor RORα stimulates profilaggrin gene transcription. This hypothesis was tested by knockdown experiments directed against mRNAs for RORα and SULT2B1b using NHEK during calcium‐induced differentiation. Concomitant with siRNA‐induced reduction in either RORα or SULT2B1b expression, a decrease in profilaggrin mRNA expression of up to 80% was observed. Furthermore, during RORα knockdown CS was unable to stimulate profilaggrin mRNA expression. These studies suggest that CS regulates the gene for profilaggrin via its ability to interact with the nuclear receptor RORα, an action reminiscent of a typical hormone.

Construction of SH-EP1-alpha4beta2-hAPP695 cell line and effects of nicotinic agonists on beta-amyloid in the cells.

(1) Nicotinic acetylcholine receptors in central nervous system are thought to be new targets for Alzheimer's disease. However, the most involved nicotinic receptor subtype in Alzheimer's disease is unclear. alpha4beta2 receptor is the most widely spread subtype in brain, involving in several important aspects of cognitive and other functions. We constructed cell line by transfecting human amyloid precursor protein (695) gene into SH-EP1 cells which have been transfected with human nicotinic receptor alpha4 subunit and beta2 subunit gene, to observe effects of alpha4beta2 receptors activation on beta-amyloid, expecting to provide a new cell line for drug screening and research purpose. (2) Liposome transfection was used to express human amyloid precursor protein (695) gene in SH-EP1-alpha4beta2 cells. Function of the transfected alpha4beta2 receptors was tested by patch clamp. Effects of nicotine and epibatidine (selective alpha4beta2 nicotinic receptor agonist) on beta-amyloid were detected by Western blot and ELISA. Effects of nicotine and epibatidine on amyloid precursor protein (695) mRNA level were measured using real-time PCR. (3) Human amyloid precursor protein (695) gene was stably expressed in SH-EP1-alpha4beta2 cells; Nicotine (1 muM) and epibatidine (0.1 muM) decreased intracellular and secreted beta-amyloid in the cells; and activation of alpha4beta2 receptors did not affect amyloid precursor protein (695) mRNA level. (4) These results suggest that the constructed cell line, expressing both amyloid precursor protein (695) gene and human nicotinic receptor alpha4 subunit and beta2 subunit gene, might be useful for screening specific nicotinic receptor agonists against Alzheimer's disease. Alteration of Abeta level induced by activation of alpha4beta2 nAChR in our study might occur at a post-translational level.

Nanoparticles: A Step Forward for Iron Chelation in the Brain

Evaluation of: Liu G, Men P, Harris PL et al.: Nanoparticle iron chelators: a new therapeutic approach in Alzheimer disease and other neurologic disorders associated with trace metal imbalance. Neurosci. Lett. 406, 189–193 (2006). Current therapies for Alzheimer’s disease (AD) are, at best, symptomatic. Cholinesterase inhibitors and memantine are intended for the treatment of cognitive symptoms, but offer only partial benefit without any disease-modifying activity. The involvement of iron in AD includes its deposition in the affected areas, the ability to promote oxidative stress and amyloid β-peptide aggregation and formation as a consequence of iron-dependent translation of amyloid precursor protein mRNA via the amyloid precursor protein 5´ untranslated region. These findings have led to a new therapeutic approach for AD, involving iron-chelating compounds with limited neurotoxicity and, more recently, their encapsulation in the form of nanoparticles to facilitate blood–brain-barrier penetration.

Trace amounts of copper induce neurotoxicity in the cholesterol-fed mice through apoptosis

Evidence has been gathered to suggest that trace amounts of copper induce neurotoxicity by interaction with elevated cholesterol in diet. Copper treatment alone showed no significant learning and memory impairments in behavioral tasks. However, copper-induced neurotoxicity was significantly increased in mice given elevated-cholesterol diet. Trace amounts of copper decreased the activity of SOD and increased the level of malondialdehyde (MDA) in the brain of cholesterol-fed mouse. Copper also caused an increase in amyloid precursor protein (APP) mRNA level and the activation of caspase-3 in the brain of cholesterol-fed mice. The apoptosis-induced nuclear DNA fragmentation was detected in the brain of those mice by terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick-end-labeling staining. These findings suggest that trace amounts of copper induce neurotoxicity in cholesterol-fed mice through apoptosis caused by oxidative stress.

A High-Throughput Drug Screen Targeted to the 5′Untranslated Region of Alzheimer Amyloid Precursor Protein mRNA

The authors employed a novel approach to identify therapeutics effective in Alzheimer disease (AD). The 5'untranslated region (5'UTR) of the mRNA of AD amyloid precursor protein (APP) is a significant regulator of the levels of the APP holoprotein and amyloid beta (Abeta) peptide in the central nervous system. The authors generated stable neuroblastoma SH-SY5Y transfectants that express luciferase under the translational control of the 146-nucleotide APP mRNA 5'UTR and green fluorescent protein (GFP) driven by a viral internal ribosomal entry site. Using a high-throughput screen (HTS), they screened for the effect of 110,000 compounds obtained from the library of the Laboratory for Drug Discovery on Neurodegeneration (LDDN) on the APP mRNA 5'UTR-controlled translation of the luciferase reporter. This screening yielded several nontoxic specific inhibitors of APP mRNA 5'UTR-driven luciferase that had no effect on the GFP expression in the stable SH-SY5Y transfectants. Moreover, these compounds either did not inhibit or inhibited to a much lower extent the expression of the luciferase reporter regulated by a prion protein (PrP) mRNA 5'UTR, used as an alternative mRNA structure to counterscreen APP mRNA 5'UTR in stably transfected SH-SY5Y cell lines. The hits obtained from this robust, specific, and highly quantitative HTS will be characterized to identify agents that may be developed into useful future therapeutic agents to limit APP translation and Abeta production for AD.

Decoy mRNAs reduce β-amyloid precursor protein mRNA in neuronal cells

Overproduction of amyloid precursor protein (APP) and β-amyloid likely contribute to neurodegeneration in Alzheimer's disease (AD). In an effort to understand neuronal APP gene regulation, we identified a 52 base element (52sce) immediately downstream from the stop codon that stabilizes APP mRNA. Deletion of this domain drastically destabilized APP mRNAs and reduced APP synthesis in vitro. Chimeric globin-APP mRNAs containing the globin coding sequence fused to the entire APP 3′-UTR, showed regulation similar to full-length APP mRNA. A variety of cytoplasmic lysates contain 52sce RNA binding activity, suggesting cis– trans interactions regulate the element's functionality. Finally, the overexpression of chimeric mRNAs, containing the GFP coding sequence and APP 3′-UTR, dramatically reduced endogenous APP steady-state levels in SH-SY5Y neuroblastoma cells and suggests a novel approach to reduce the amyloid burden in AD patients.

An Overview of Phenserine Tartrate, A Novel Acetylcholinesterase Inhibitor for the Treatment of Alzheimers Disease

Existing cholinesterase (ChE) inhibitor therapies for Alzheimer's disease (AD), while effective in improving cognitive, behavioral and functional impairments, do not alter disease progression. Novel drug design studies have focused on the classical ChE inhibitor, (-)-physostigmine, producing alterations in chemical composition and three-dimensional structure, which may offer an improved therapeutic index. The phenylcarbamate derivative, (-)-phenserine, is a selective, non-competitive inhibitor of acetylcholinesterase (AChE). In vivo, (-)-phenserine produces rapid, potent, and long-lasting AChE inhibition. As a possible result of its preferential brain selectivity, (-)-phenserine is significantly less toxic than (-)-physostigmine. In studies using the Stone maze paradigm, (-)-phenserine has been shown to improve cognitive performance in both young learning-impaired and elderly rats. In addition to reducing inactivation of acetylcholine in the brain, (-)-phenserine appears to have a second mode of action. Reduced secretion of beta-amyloid (Abeta) has been observed in cell lines exposed to (-)-phenserine, occurring through translational regulation of beta-amyloid precursor protein (beta-APP) mRNA via a non-cholinergic mechanism. These in vitro findings appear to translate in vivo into animal models and humans. In a small study of patients with AD, (-)-phenserine treatment tended to reduce beta-APP and Abeta levels in plasma samples. Clinical studies also reveal that (-)-phenserine (5-10 mg b.i.d.) had a favorable safety and pharmacological profile, produced significant improvements in cognitive function and was well tolerated in patients with AD treated for 12 weeks. Further randomized, double-blind, placebo-controlled Phase III studies assessing the efficacy, safety/tolerability and potential disease-modifying effects of (-)-phenserine in patients with AD are currently ongoing.

Impaired insulin and insulin-like growth factor expression and signaling mechanisms in Alzheimer's disease – is this type 3 diabetes?

The neurodegeneration that occurs in sporadic Alzheimer's disease (AD) is consistently associated with a number of characteristic histopathological, molecular, and biochemical abnormalities, including cell loss, abundant neurofibrillary tangles and dystrophic neurites, amyloid-beta deposits, increased activation of pro-death genes and signaling pathways, impaired energy metabolism/mitochondrial function, and evidence of chronic oxidative stress. The general inability to convincingly link these phenomena has resulted in the emergence and propagation of various heavily debated theories that focus on the role of one particular element in the pathogenesis of all other abnormalities. However, the accumulating evidence that reduced glucose utilization and deficient energy metabolism occur early in the course of disease, suggests a role for impaired insulin signaling in the pathogenesis of AD. The present work demonstrates extensive abnormalities in insulin and insulin-like growth factor type I and II (IGF-I and IGF-II) signaling mechanisms in brains with AD, and shows that while each of the corresponding growth factors is normally made in central nervous system (CNS) neurons, the expression levels are markedly reduced in AD. These abnormalities were associated with reduced levels of insulin receptor substrate (IRS) mRNA, tau mRNA, IRS-associated phosphotidylinositol 3-kinase, and phospho-Akt (activated), and increased glycogen synthase kinase-3beta activity and amyloid precursor protein mRNA expression. The strikingly reduced CNS expression of genes encoding insulin, IGF-I, and IGF-II, as well as the insulin and IGF-I receptors, suggests that AD may represent a neuro-endocrine disorder that resembles, yet is distinct from diabetes mellitus. Therefore, we propose the term, "Type 3 Diabetes" to reflect this newly identified pathogenic mechanism of neurodegeneration.

Regional selectivity of amyloid mRNA expression and neurotrophins on repetitive inhibition of oxidative phosphorylation

Previously we showed that repetitive inhibition of oxidative phosphorylation impairs synaptic transmission and induces overexpression of amyloid precursor protein mRNA (APP-mRNA) in the hippocampus (Hellweg et al., 2003). Here we show that APP-mRNA remains alike in murine frontal cortex and cerebellum on repetitive treatment with 3-nitropropionate. However, nerve growth factor and brain-derived neurotrophic factor decreased by 28 to 38% in frontal cortex. Taken together, the pattern of change resembles genetic models of Alzheimer's disease with less susceptibility for overexpression of amyloid mRNA in frontal cortex than in hippocampus and reduced neurotrophin levels in frontal cortex. Given the similarity of this pattern to the one observed in human Alzheimer's disease the present model in future may give further insight into the pathophysiology of sporadic Alzheimer's disease.