Cerebrospinal fluid epinephrine in Alzheimer's disease and normal aging

Chromogranin A (CgA) Deficiency Attenuates Tauopathy by Altering Epinephrine-Alpha-Adrenergic Receptor Signaling

Our previous studies have indicated that insulin resistance, hyperglycemia, and hypertension in aged wild-type (WT) mice can be reversed in mice lacking chromogranin-A (CgA-KO mice). These health conditions are associated with a higher risk of Alzheimer's disease (AD). CgA, a neuroendocrine secretory protein has been detected in protein aggregates in the brains of AD patients. Here, we determined the role of CgA in tauopathies, including AD (secondary tauopathy) and corticobasal degeneration (CBD, primary tauopathy). We found elevated levels of CgA in both AD and CBD brains, which were positively correlated with increased phosphorylated tau in the frontal cortex. Furthermore, CgA ablation in a human P301S tau (hTau) transgenic mice (CgA-KO/hTau) exhibited reduced tau aggregation, resistance to tau spreading, and an extended lifespan, coupled with improved cognitive function. Transcriptomic analysis of mice cortices highlighted altered levels of alpha-adrenergic receptors (Adra) in hTau mice compared to WT mice, akin to AD patients. Since CgA regulates the release of the Adra ligands epinephrine (EPI) and norepinephrine (NE), we determined their levels and found elevated EPI levels in the cortices of hTau mice, AD and CBD patients. CgA-KO/hTau mice exhibited reversal of EPI levels in the cortex and the expression of several affected genes, including Adra1 and 2, nearly returning them to WT levels. Treatment of hippocampal slice cultures with EPI or an Adra1 agonist intensified, while an Adra1 antagonist inhibited, tau hyperphosphorylation and aggregation. These findings reveal a critical role of CgA in regulation of tau pathogenesis via the EPI-Adra signaling axis.

Thiazole-Based Silver Ion Sensor for Sequential Colorimetric Visualization of Epinephrine in the Brain Tissues of an Alzheimer's Disease Model of Mouse

A thiazole-based probe, N'-((2-aminothiazol-5-yl)methylene)benzohydrazide (TBH), has been efficiently synthesized and characterized for the selective and sensitive detection of the neurotransmitter epinephrine (EP). The sensing strategy is based on the use of TBH for sequential colorimetric sensing of Ag+ and EP via in situ formation of Ag nanoparticles (Ag NPs) from the TBH-Ag+ complex. The generated Ag NPs lead to a bathochromic shift in absorption maximum and a change in color of the solution from light brown to reddish brown. TBH-Ag+ shows remarkable selectivity toward EP versus other drugs, common cations, anions, and some biomolecules. Moreover, TBH-Ag+ has a low detection limit for EP at 1.2 nM. The coordination of TBH-Ag+ has been proposed based on Job's plot, Fourier transform infrared spectroscopy (FT-IR), high-resolution mass spectrometry (HRMS), 1H NMR titration, X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray analysis (EDAX), and density functional theory (DFT) studies. The composition and morphology of the generated Ag NPs have been analyzed by XPS, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and dynamic light scattering (DLS). The proposed sensing mechanism for EP has been supported by XPS of Ag after the reaction. Further, the sensitivity of TBH-Ag+ toward EP in brain tissues of an Alzheimer's disease model of mouse has been evaluated. A thorough comparison was done for evaluation of the proposed method.

Salivary 3-methoxy-4-hydroxyphenylglycol and MRI-based volume change of the precuneus in community-dwelling elderly people

BACKGROUND

The noradrenergic systems in the brain maintain cognitive functions including attention/concentration and establishment of long-term memory. In addition, hypofunction of noradrenergic systems is supposed to be involved in the pathophysiology of Alzheimer's disease. In this study, we tried to examine the possible associations of concentrations of basal salivary 3-methoxy-4-hydroxyphenylglycol (sMHPG), a major metabolite of noradrenaline, and brain volume changes during 4 years in elderly people living in a rural community.

METHODS

The survey was conducted twice in Kurokawa-cho, Imari, Saga Prefecture, Japan, among people aged 65 years and older. We collected data from 226 residents. Measurements of sMHPG and brain MRIs were collected at Time 1 (2005-2007). Follow-up brain MRIs were taken at Time 2 (2009-2011). A total of 70 participants (18 men, mean age 71.9 ± 4.8 years; 52 women, mean age 72.0 ± 4.3 years) completed this survey. Concentrations of sMHPG at baseline were divided into two groups using the mean value (12.83 ng/ml). We compared the brain volumes between groups with higher and lower sMHPG concentrations over time using voxel-based morphometry implemented with statistical parametric mapping.

RESULTS

In participants with higher sMHPG concentrations at baseline, brain volumes including right precuneus were significantly larger 4 years after baseline than those with lower sMHPG concentrations at baseline. No interaction between sMHPG concentration and MRI acquisition interval was found.

CONCLUSION

Our results suggest that higher sMHPG concentrations in elderly people might be associated with maintenance of brain volume, especially in brain regions closely related to cognitive function.

New Trends in Fluorescent Nanomaterials-Based Bio/Chemical Sensors for Neurohormones Detection-A Review

The study of neurotransmitters and stress hormones allows the determination of indicators of the current stress load in the body. These species also create a proper strategy of stress protection. Nowadays, stress is a general factor that affects the population, and it may cause a wide range of serious disorders. Abnormalities in the level of neurohormones, caused by chronic psychological stress, can occur in, for instance, corporate employees, health care workers, shift workers, policemen, or firefighters. Here we present a new nanomaterials-based sensors technology development for the determination of neurohormones. We focus on fluorescent sensors/biosensors that utilize nanomaterials, such as quantum dots or carbon nanomaterials. Nanomaterials, owing to their diversity in size and shape, have been attracting increasing attention in sensing or bioimaging. They possess unique properties, such as fluorescent, electronic, or photoluminescent features. In this Review, we summarize new trends in adopting nanomaterials for applications in fluorescent sensors for neurohormone monitoring.

Cerebrospinal fluid catecholamines in Alzheimer's disease patients with and without biological disease

Noradrenergic and dopaminergic neurons are involved in cognitive functions, relate to behavioral and psychological symptoms in dementia and are affected in Alzheimer's disease (AD). Amyloid plaques (A), neurofibrillary tangles (T) and neurodegeneration (N) hallmarks the AD neuropathology. Today, the AT(N) pathophysiology can be assessed through biomarkers. Previous studies report cerebrospinal fluid (CSF) catecholamine concentrations in AD patients without biomarker refinement. We explored if CSF catecholamines relate to AD clinical presentation or neuropathology as reflected by CSF biomarkers. CSF catecholamines were analyzed in AD patients at the mild cognitive impairment (MCI; n = 54) or dementia stage (n = 240) and in cognitively unimpaired (n = 113). CSF biomarkers determined AT status and indicated synaptic damage (neurogranin). The AD patients (n = 294) had higher CSF noradrenaline and adrenaline concentrations, but lower dopamine concentrations compared to the cognitively unimpaired (n = 113). AD patients in the MCI and dementia stage of the disease had similar CSF catecholamine concentrations. In the CSF neurogranin positively associated with noradrenaline and adrenaline but not with dopamine. Adjusted regression analyses including AT status, CSF neurogranin, age, gender, and APOEε4 status verified the findings. In restricted analyses comparing A+T+ patients to A-T- cognitively unimpaired, the findings for CSF adrenaline remained significant (p < 0.001) but not for CSF noradrenaline (p = 0.07) and CSF dopamine (p = 0.33). There were no differences between A+T+ and A-T- cognitively unimpaired. Thus, we find alterations in CSF catecholamines in symptomatic AD and the CSF adrenergic transmitters to increase simultaneously with synaptic damage as indexed by CSF neurogranin.

Differential pulse voltammetry and chronoamperometry as analytical tools for epinephrine detection using a tyrosinase-based electrochemical biosensor

The main goal of the presented study was to design a biosensor-based system for epinephrine (EP) detection using a poly-thiophene derivative and tyrosinase as a biorecognition element. We compared two different electroanalytical techniques to select the most prominent technique for analyzing the neurotransmitter. The prepared biosensor system exhibited good parameters; the differential pulse (DPV) technique presented a wide linear range (1–20 μM and 30–200 μM), with a low detection limit (0.18 nM and 1.03 nM). In the case of chronoamperometry (CA), a high signal-to-noise ratio and lower reproducibility were observed, causing a less broad linear range (10–200 μM) and a higher detection limit (125 nM). Therefore, the DPV technique was used for the calculation of sensitivity (0.0011 μA mM⁻¹ cm⁻²), stability (49 days), and total surface coverage (4.18 × 10⁻¹² mol cm⁻²). The biosensor also showed very high selectivity in the presence of common interfering species (i.e. ascorbic acid, uric acid, norepinephrine, dopamine) and was successfully applied for EP determination in a pharmaceutical sample.

GCE/poly-4,4′-bBT/tyrosinase biosensor for epinephrine was constructed. Comparison of differential pulse voltammetry (DPV) and chronoamperometry was performed. DPV showed more reproducible results giving high selectivity, sensitivity, stability.

Catecholamines in Alzheimer's Disease: A Systematic Review and Meta-Analysis

Background and Purpose: Previous studies found inconsistent results regarding the relationship between Alzheimer's disease (AD) and catecholamines, such as dopamine (DA), norepinephrine (NE), and epinephrine (EPI). Therefore, the purpose of this study was to perform a systematic review and meta-analysis to evaluate the results of previous studies on this relationship.

Method: Literature retrieval of eligible studies was performed in four databases (Web of Science, PubMed, Embase, and PsycARTICLES). Standardized mean differences (SMDs) were calculated to assess differences in catecholamine concentrations between the AD groups and controls.

Results: Thirteen studies met the eligibility criteria. Compared with the controls, significant lower concentrations of NE (SMD = −1.10, 95% CI: −2.01 to −0.18, p = 0.019) and DA (SMD = −1.12, 95% CI: −1.88 to −0.37, p = 0.003) were observed in patients with AD. No difference was found in the concentrations of EPI between the two groups (SMD = −0.74, 95% CI: −1.85 to 0.37, p = 0.189).

Conclusion: Overall, these findings are in line with the hypothesis that reduced NE and DA may be an important indicator for AD (Registration number CRD42018112816).

A Fluorescent Biosensors for Detection Vital Body Fluids' Agents

The clinical applications of sensing tools (i.e., biosensors) for the monitoring of physiologically important analytes are very common. Nowadays, the biosensors are being increasingly used to detect physiologically important analytes in real biological samples (i.e., blood, plasma, urine, and saliva). This review focuses on biosensors that can be applied to continuous, time-resolved measurements with fluorescence. The material presents the fluorescent biosensors for the detection of neurotransmitters, hormones, and other human metabolites as glucose, lactate or uric acid. The construction of microfluidic devices based on fluorescence uses a variety of materials, fluorescent dyes, types of detectors, excitation sources, optical filters, and geometrical systems. Due to their small size, these devices can perform a full analysis. Microfluidics-based technologies have shown promising applications in several of the main laboratory techniques, including blood chemistries, immunoassays, nucleic-acid amplification tests. Of the all technologies that are used to manufacture microfluidic systems, the LTCC technique seems to be an interesting alternative. It allows easy integration of electronic and microfluidic components on a single ceramic substrate. Moreover, the LTCC material is biologically and chemically inert, and is resistant to high temperature and pressure. The combination of all these features makes the LTCC technology particularly useful for implementation of fluorescence-based detection in the ceramic microfluidic systems.

The neurochemistry of agitation in Alzheimer's disease: a systematic review

OBJECTIVE

To provide an up-to-date systematic review of the characteristics, methodology and findings of studies that have investigated the neurochemistry of agitation in Alzheimer's disease (AD).

METHODS

Electronic databases were searched for published peer-reviewed articles which provided data on any neurotransmitter system in relation to agitation in AD. Screening of titles and abstracts and data extraction from full texts were conducted in duplicate.

RESULTS

Forty-five studies were included. Monoamines (serotonin, dopamine and noradrenaline) were most commonly investigated. A variety of methods were used to investigate the neurochemistry underlying agitation in AD and, although there were several conflicting findings, there was evidence of serotonergic deficit, relatively preserved dopaminergic function and compensatory overactivity of postsynaptic noradrenergic neurons in agitation in AD.

CONCLUSIONS

Disruption of the dynamic balance between multiple neurotransmitter systems could impair functional neural networks involved in affective regulation and executive function. Differences in study design and methodology may have contributed to conflicting findings. Future studies that overcome these limitations (e.g. using standardized criteria to define agitation) and employ neuroimaging methods such as MRI/PET to investigate specific neural networks are needed to clarify the role of neurotransmitter alterations in these patients.

Associations between CSF cortisol and CSF norepinephrine in cognitively normal controls and patients with amnestic MCI and AD dementia

OBJECTIVE

This study evaluated the effects of Alzheimer disease (AD) on the relationship between the brain noradrenergic system and hypothalamic pituitary adrenocortical axis (HPA). Specifically, relationships between cerebrospinal fluid (CSF) norepinephrine (NE) and CSF cortisol were examined in cognitively normal participants and participants with AD dementia and amnestic mild cognitive impairment (aMCI). We hypothesized that there would a positive association between these 2 measures in cognitively normal controls and that this association would be altered in AD.

METHODS

Four hundred twenty-one CSF samples were assayed for NE and cortisol in controls (n = 305), participants with aMCI (n = 22), and AD dementia (n = 94). Linear regression was used to examine the association between CSF cortisol and NE, adjusting for age, sex, education, and body mass index.

RESULTS

Contrary to our hypothesis, CSF cortisol and NE levels were not significantly associated in controls. However, higher cortisol levels were associated with higher NE levels in AD and aMCI participants. Regression coefficients ± standard errors for the change in cortisol per 100-pg/mL increase in NE are as follows: controls 0.0 ± 0.2, P = 1.0; MCI, 1.4 ± 0.7, P = .14; and AD 1.1 ± 0.4, P = .032. Analysis with MCI and AD participants combined strengthened statistical significance (1.2 ± 0.3, P = .007).

CONCLUSIONS

Enhanced responsiveness of the HPA axis to noradrenergic stimulatory regulation in AD and disruption of the blood brain barrier may contribute to these findings. Because brainstem noradrenergic stimulatory regulation of the HPA axis is substantially increased by both acute and chronic stress, these findings are also consistent with AD participants experiencing higher levels of acute and chronic stress.

Rapid Eye Movement Sleep Deprivation Induces Neuronal Apoptosis by Noradrenaline Acting on Alpha1 Adrenoceptor and by Triggering Mitochondrial Intrinsic Pathway

Many neurodegenerative disorders are associated with rapid eye movement sleep (REMS) loss; however, the mechanism was unknown. As REMS loss elevates noradrenaline (NA) level in the brain as well as induces neuronal apoptosis and degeneration, in this study, we have delineated the intracellular molecular pathway involved in REMS deprivation (REMSD)-associated NA-induced neuronal apoptosis. Rats were REMS deprived for 6 days by the classical flower pot method; suitable controls were conducted and the effects on apoptosis markers evaluated. Further, the role of NA was studied by one, intraperitoneal (i.p.) injection of NA-ergic alpha1 adrenoceptor antagonist prazosin (PRZ) and two, by downregulation of NA synthesis in locus coeruleus (LC) neurons by local microinjection of tyrosine hydroxylase siRNA (TH-siRNA). Immunoblot estimates showed that the expressions of proapoptotic proteins viz. Bcl2-associated death promoter protein, apoptotic protease activating factor-1 (Apaf-1), cytochrome c, caspase9, caspase3 were elevated in the REMS-deprived rat brains, while caspase8 level remained unaffected; PRZ treatment did not allow elevation of these proapoptotic factors. Further, REMSD increased cytochrome c expression, which was prevented if the NA synthesis from the LC neurons was blocked by microinjection of TH-siRNA in vivo into the LC during REMSD in freely moving normal rats. Mitochondrial damage was re-confirmed by transmission electron microscopy, which showed distinctly swollen mitochondria with disintegrated cristae, chromosomal condensation, and clumping along the nuclear membrane, and all these changes were prevented in PRZ-treated rats. Combining findings of this study along with earlier reports, we propose that upon REMSD NA level increases in the brain as the LC, NA-ergic REM-OFF neurons do not cease firing and TH is upregulated in those neurons. This elevated NA acting on alpha1 adrenoceptors damages mitochondria causing release of cytochrome c to activate intrinsic pathway for inducing neuronal apoptosis in REMS-deprived rat brain.

Metabolic and Non-Cognitive Manifestations of Alzheimer's Disease: The Hypothalamus as Both Culprit and Target of Pathology

Alzheimer's disease (AD) is increasingly recognized as a complex neurodegenerative disease beginning decades prior to the cognitive decline. While cognitive deficits remain the cardinal manifestation of AD, metabolic and non-cognitive abnormalities, such as alterations in body weight and neuroendocrine functions, are also present, often preceding the cognitive decline. Furthermore, hypothalamic dysfunction can also be a driver of AD pathology. Here we offer a brief appraisal of hypothalamic dysfunction in AD and provide insight into an underappreciated dual role of the hypothalamus as both a culprit and target of AD pathology, as well as into new opportunities for therapeutic interventions and biomarker development.

Endproducts and receptor of advanced glycation and lipoxidation (AGE, ALE, RAGE) and chronic diseases – a food perspective

Background: Chronic diseases as well as complications to acute and chronic disease are repeatedly associated with accumulation in the body of glycated and lipoxidated proteins and peptides. These molecules are strongly associated with activation of a specific receptor called RAGE and a long-lasting exaggerated level of inflammation in the body. Methods: PubMed reports in excess of 5000 papers plus about 14000 articles about the related HbA1c, most of them published in the last five years. Most of available abstracts have been read and circa 800 full papers studied in detail. Results: RAGE, a member of the immunoglobulin superfamily of cell surface molecules and receptor for advanced glycation endproducts, functions as a master switch, induces sustained activation of NF-κB, suppresses a series of endogenous autoregulatory functions and converts long-lasting pro-inflammatory signals into sustained cellular dysfunction and disease. Its activation is associated with high levels of dysfunctioning proteins in body fluids and tissues, and strongly associated with a series of diseases from allergy and Alzheimer to rheumatoid arthritis and urogenital disorders. Heat-treatment, irradiation and ionisation of foods increase the content in foods of AGE/ALE. Conclusions: Some processed foods are much like tobacco smoking great contributors to accumulation of glycated and lipoxidated molecules in the tissues. Change of life style: avoidance of foods rich in deranged proteins and peptides and increased consumption of antioxidants, especially polyphenols counteracts such a development.

Alois Alzheimer revisited: differences in origin of the disease carrying his name

Based on the means of his time, Alois Alzheimer supposed that the disease, later carrying his name, is a disease of older age, and that the pathomorphological structures he described are due to disturbances in brain metabolism. In this contribution, it is discussed which cellular metabolic abnormalities may be representative for age-related sporadic Alzheimer disease (SAD) the predominant form of SAD in contrast to the very rare hereditary early-onset form. In focus are disturbances in glucose/energy metabolism which involve the deficits in acetylcholine, cholesterol and UDP-N-acetylglucosamine beside ATP. Another leading abnormality is the defect in cell membrane composition. The interrelation between abnormal glucose/energy metabolism and membrane defect may be assumed to form the basis for the induction of both the perturbed metabolism of the amyloid precursor protein leading to increased formation of beta-amyloid and hyperphosphorylation of tau-protein destroying cell structures. Alois Alzheimer may have been so prescient to assume most of this 100 years ago.

Increase in epinephrine excretion is associated with cognitive decline in elderly men: MacArthur studies of successful aging

BACKGROUND

High stress hormone levels are associated with increased risk of cognitive decline in elderly individuals. However, the effect of late-life changes in stress hormone levels on cognitive decline risk has not been examined. Our objective was to investigate whether increase over time in urinary epinephrine excretion in older adults was associated with subsequent cognitive decline.

METHODS

Measurements were made on 154 high-functioning men and women, 70-79 years of age, in 1988, 1991, and 1995. Twelve-hour overnight urinary excretion of epinephrine (normalized by creatinine excretion to adjust for body size) was recorded in 1988 and 1991. Cognitive functioning was assessed in 1991 and 1995 by summary scores based on standard tests of language, memory, abstraction, spatial recognition, and spatial construction.

RESULTS

Compared to individuals whose epinephrine excretion decreased between 1988 and 1991, the individuals whose epinephrine excretion increased over the same period had greater subsequent declines in summary cognitive scores between 1991 and 1995. After adjusting for baseline epinephrine, baseline cognitive function, and relevant covariates, and stratifying by gender, increases in urine epinephrine were positively associated with cognitive decline only in men.

CONCLUSIONS

We conclude that increase in urinary excretion of epinephrine predicts subsequent cognitive decline in older men.

Glucose metabolism and insulin receptor signal transduction in Alzheimer disease

Nosologically, Alzheimer disease is not a single disorder in spite of a common clinical phenotype. Etiologically, two different types or even more exist. (1) In a minority of about 5% or less of all cases, Alzheimer disease is due to mutations of three genes, resulting in the permanent generation of betaA4. (2) The great majority (95% or more) of cases of Alzheimer disease are sporadic in origin, with old age as main risk factor, supporting the view that susceptibility genes and aging contribute to age-related sporadic Alzheimer disease. However, disturbances in the neuronal insulin signal transduction pathway may be of central pathophysiological significance. In early-onset familial Alzheimer disease, the inhibition of neuronal insulin receptor function may be due to competitive binding of amyloid beta (Abeta) to the insulin receptor. In late-onset sporadic Alzheimer disease, the neuronal insulin receptor may be desensitized by inhibition of receptor function at different sites by noradrenaline and/or cortisol, the levels of which both increase with increasing age. The consequences of the inhibition of neuronal insulin signal transduction may be largely identical to those of disturbances of oxidative energy metabolism and related metabolism, and of hyperphosphorylation of tau-protein. As far as the metabolism of amyloid precursor protein (APP) in late-onset sporadic Alzheimer disease is concerned, neuronal insulin receptor dysfunction may result in the intracellular accumulation of Abeta and in subsequent cellular damage. In this context, the desensitization of the neuronal insulin receptor in late-onset sporadic Alzheimer disease is different from that occurring in normal aging and early-onset familial Alzheimer disease. In late-onset sporadic Alzheimer disease changes in the brain are similar to those caused by non-insulin-dependent diabetes mellitus.

Causes and consequences of disturbances of cerebral glucose metabolism in sporadic Alzheimer disease: therapeutic implications

Alzheimer disease is not a single disorder. Etiologically, two different types or even diseases exist: inheritance in 5% to 10% of all Alzheimer cases versus 90% to 95% AD cases whith sporadic origin (SAD). Different susceptibility genes along with adult lifestyle risk-factors- in the case of SAD the risk factor aging- may be assumed to cause the latter disorder. There is evidence that a disturbance in the insulin signal transduction pathway may be a central and early pathophysiologic event in SAD. Both, hypercortisolemia and increased adrenergic activity, in both old age and SAD may render the function of the neuronal insulin receptor vulnerable resulting in a diminished production of ATP. The reduced availability of ATP may damage the function of the endoplasmic reticulum/Golgi apparatus/trans Golgi network generating misfolded and malfolded proteins retained in the cell. In SAD, amyloid precursor protein is found to accumulate intracellularly thus not representing the cause but a driving force in the pathogenesis of SAD. Additionally, both disturbed insulin signaling and reduced ATP forward the hyperphosphorylation of tau protein. Thus, abnormalities in oxidative brain metabolism lead to the formation of two main morphologic hallmarks of SAD: senile plaques and neurofibrillary tangles. Therefore, the therapeutic goal in SAD should be the improvement of the neuronal energy state. Findings from both basic and clinical studies showed that Ginkgo biloba extract (EGb 761) may be appropiate to approach that goal.

Estrogen and Alzheimer's disease: the story so far

The ovarian hormone estrogen has long been used to treat the physical symptoms of menopause and to aid in the prevention of osteoporosis in postmenopausal women. Cumulative evidence from basic science and clinical research suggests that estrogen also plays a significant neuromodulatory and neuroprotective role. The numerous estrogenic effects in the brain include the modulation of synaptogenesis, increased cerebral blood flow, mediation of important neurotransmitters and hormones, protection against apoptosis, anti-inflammatory actions, and antioxidant properties. These multiple actions in the central nervous system support estrogen as a potential treatment for the cognitive decline associated with Alzheimer's disease (AD), the most common form of dementia. Evidence from epidemiological studies supports enhanced cognitive function in women with AD taking estrogen replacement therapy (ERT) as well as a reduced risk for developing AD in healthy women receiving ERT. Additional clinical evidence suggests that estrogen may modulate specific cognitive functions such as working memory and verbal learning and memory. However, results from more recent controlled trials have not consistently shown a beneficial effect of estrogen on the cognitive function of women with AD. Future research should focus on examining the influence of multiple potential mediators of ERT including the route of estrogen administration, form of estrogen (conjugated estrogens vs estradiol), duration of treatment, opposed versus unopposed estrogen and the use of estrogen analogues. Further, sensitive neuropsychological measures may provide more detailed information concerning the specific effects of estrogen on cognitive function. These important issues must be addressed in order to establish the role of estrogen for the prevention and treatment of AD in women.

Pathogenic theories and intrathecal analysis of the sporadic form of Alzheimer's disease

Alzheimer's disease (AD) is an age-dependent dementia characterized by progressive loss of cognitive functions and by characteristic pathological changes in the brain: the formation of aggregates extracellularly by beta-amyloid (Abeta) peptide and intracellularly by tau proteins. The disease presents several major diagnostic difficulties: (1) AD develops slowly; (2) analysis of damaged brain tissues is difficult, requiring a biopsy which poses ethical problems; (3) no biochemical markers are available for the diagnosis and monitoring of the disease progression. Since the cerebrospinal fluid (CSF) is in contact with the extracellular space of the brain, many studies have tried to correlate the levels of the intrathecal peptides and amino acids and the development of dementia. The present review analyzes the main results of intrathecal content analyses in light of pathogenic theories proposed to explain the damage associated with AD and observed in the brain of patients by postmortem examination.

Yohimbine: a clinical review

Although yohimbine (YOH) has been available for the treatment of male erectile dysfunction (ED) for longer than Viagra, there is a perception that little is known about the clinical performance of the drug. This review attempts, by comprehensive analysis of the literature, to cover the clinical, pharmacological, and therapeutic profiles of YOH, relevant to its potential utility in the management of patients with ED. Relatively few well-designed studies have been completed. From these, however, it can be concluded that YOH as monotherapy possesses only modest efficacy in ED patients. In acute and chronic (long-term) studies, YOH has been found to be relatively free of side effects over the dose range predicted to be effective in ED. At much higher doses, the most frequently observed effects, consistent with the primary pharmacological action of the drug, are elevation of blood pressure, a slight anxiogenic action, and increased frequency of urination. These side effects are all easily reversible on termination of YOH therapy. There is increasing evidence that the erectogenic action of YOH can be augmented by concomitant administration of agents that augment the release and/or action of nitric oxide in the corpus cavernosum. YOH has yet to be studied in female sexual dysfunction. Overall, the benefit risk profile of YOH would indicate that it has potential, more probably as part of a combination strategy, e.g., with a drug that enhances the nitric oxide pathway, in the treatment of ED.

Brain glucose and energy metabolism abnormalities in sporadic Alzheimer disease. Causes and consequences: an update

It is discussed that Alzheimer disease does not form a nosologic entity. 5 to 10% of all Alzheimer cases are due to inherited abnormalities on chromosomes 1, or 14, or 21, whereas the majority of 90-95% is sporadic in origin. Age-related changes in the composition of membranes and in glucose/energy metabolism along with a sympathetic tone in the brain are assumed to be cellular/molecular risk factors for this disease. In its pathogenesis, the desensitization of the neuronal insulin receptor similar to non-insulin dependent diabetes mellitus may be of pivotal significance. This abnormality along with a reduction in insulin concentration is assumed to induce a cascade-like process of disturbances including decreases in cellular glucose, acetylcholine, cholesterol, and ATP, associated with changes in the metabolism of amino acids and fatty acids. There is evidence that the reductions in the availability of both glucose/energy and insulin contribute to the formation of amyloidogenic derivatives and hyperphosphorylated tau protein. This may indicate that the amyloid cascade hypothesis in not valid for sporadic Alzheimer disease but that the formation of both, amyloidogenic derivatives and hyperphosphorylated tau protein is downstream the origin of this neurodegenerative disease.

Hypothalamic pituitary adrenocortical and sympathetic nervous system responses to the cold pressor test in Alzheimer's disease

BACKGROUND

Increased basal activity of the hypothalamic-pituitary-adrenocortical (HPA) axis has been repeatedly demonstrated in Alzheimer's disease (AD), and some studies suggest increased basal activity of the sympathetic nervous system (SNS) in this disorder; however, the effects of AD on HPA axis or SNS responses to a standardized aversive stressor have not been examined. The neuroendocrine response to aversive stress may be relevant to the pathophysiology of AD.

METHODS

Plasma adrenocorticotropic hormone (ACTH), cortisol, norepinephrine (NE), and epinephrine responses to a 1-min cold pressor test (CPT) were measured in nine medically healthy AD outpatients (age 76 +/- 2 years) and nine age- and gender-matched medically healthy cognitively normal older subjects (age 76 +/- 1 year).

RESULTS

The cortisol response to CPT was increased in the AD group but the ACTH response did not differ between groups. Basal NE concentrations were higher in the AD group. Although NE responses to CPT did not differ between groups, the blood pressure response to CPT was higher in the AD subjects.

CONCLUSIONS

These results suggest increased HPA axis responsiveness to CPT at the level of the adrenal cortex in AD. The results also suggest increased basal sympathoneural activity and increased cardiovascular responsiveness to sympathoneural stimulation in AD under the conditions of this experimental protocol. Increased SNS stimulatory modulation of the adrenal cortex is a possible mechanism contributing to the observed enhanced cortisol response to CPT in these AD subjects.

The role of norepinephrine in the pathophysiology of cognitive disorders: potential applications to the treatment of cognitive dysfunction in schizophrenia and Alzheimer's disease

The role of noradrenergic neurotransmission in normal cognitive functions has been extensively investigated, however, the involvement of noradrenergic functions in the cognitive impairment associated with schizophrenia and Alzheimer's disease has not been as intensively considered. The limited ability of atypical antipsychotics to treat the cognitive impairment of schizophrenia, and cholinomimetics to treat the cognitive impairment of Alzheimer's disease, may be related to the influence of a multiplicity of neurotransmitter abnormalities including noradrenergic dysfunction, which these treatments do not address. The evidence of noradrenergic dysfunction occurring concomitantly with dopamine dysfunction in schizophrenia and acetylcholine dysfunction in Alzheimer's disease supports therapeutic approaches using noradrenergic drugs in combination with neuroleptics and cholinesterase inhibitors, respectively, to enhance the treatment of cognitive impairment. Given the results of animal and human studies, it appears that alpha-2A agonists may be the optimal choice for this purpose.