Cerebrospinal fluid neuropeptides in Alzheimer's disease and vascular dementia

Single-cell sequencing of entorhinal cortex reveals widespread disruption of neuropeptide networks in Alzheimer's disease

INTRODUCTION

Abnormalities of neuropeptides (NPs) that play important roles in modulating neuronal activities are commonly observed in Alzheimer's disease (AD). We hypothesize that NP network disruption is widespread in AD brains.

METHODS

Single-cell transcriptomic data from the entorhinal cortex (EC) were used to investigate the NP network disruption in AD. Bulk RNA-sequencing data generated from the temporal cortex by independent groups and machine learning were employed to identify key NPs involved in AD. The relationship between aging and AD-associated NP (ADNP) expression was studied using GTEx data.

RESULTS

The proportion of cells expressing NPs but not their receptors decreased significantly in AD. Neurons expressing higher level and greater diversity of NPs were disproportionately absent in AD. Increased age coincides with decreased ADNP expression in the hippocampus.

DISCUSSION

NP network disruption is widespread in AD EC. Neurons expressing more NPs may be selectively vulnerable to AD. Decreased expression of NPs participates in early AD pathogenesis. We predict that the NP network can be harnessed for treatment and/or early diagnosis of AD.

Myelin in Alzheimer's disease: culprit or bystander?

Alzheimer's disease (AD) is a neurodegenerative disorder with neuronal and synaptic losses due to the accumulation of toxic amyloid β (Αβ) peptide oligomers, plaques, and tangles containing tau (tubulin-associated unit) protein. While familial AD is caused by specific mutations, the sporadic disease is more common and appears to result from a complex chronic brain neuroinflammation with mitochondriopathies, inducing free radicals' accumulation. In aged brain, mutations in DNA and several unfolded proteins participate in a chronic amyloidosis response with a toxic effect on myelin sheath and axons, leading to cognitive deficits and dementia. Αβ peptides are the most frequent form of toxic amyloid oligomers. Accumulations of misfolded proteins during several years alters different metabolic mechanisms, induce chronic inflammatory and immune responses with toxic consequences on neuronal cells. Myelin composition and architecture may appear to be an early target for the toxic activity of Aβ peptides and others hydrophobic misfolded proteins. In this work, we describe the possible role of early myelin alterations in the genesis of neuronal alterations and the onset of symptomatology. We propose that some pathophysiological and clinical forms of the disease may arise from structural and metabolic disorders in the processes of myelination/demyelination of brain regions where the accumulation of non-functional toxic proteins is important. In these forms, the primacy of the deleterious role of amyloid peptides would be a matter of questioning and the initiating role of neuropathology would be primarily the fact of dysmyelination.

Identification of Molecular Signatures and Candidate Drugs in Vascular Dementia by Bioinformatics Analyses

Vascular dementia (VaD) is considered to be the second most common form of dementia after Alzheimer’s disease, and no specific drugs have been approved for VaD treatment. We aimed to identify shared transcriptomic signatures between the frontal cortex and temporal cortex in VaD by bioinformatics analyses. Gene ontology and pathway enrichment analyses, protein–protein interaction (PPI) and hub gene identification, hub gene–transcription factor interaction, hub gene–microRNA interaction, and hub gene–drug interaction analyses were performed. We identified 159 overlapping differentially expressed genes (DEGs) between the frontal cortex and temporal cortex that were enriched mainly in inflammation and innate immunity, synapse pruning, regeneration, positive regulation of angiogenesis, response to nutrient levels, and positive regulation of the digestive system process. We identified 10 hub genes in the PPI network (GNG13, CD163, C1QA, TLR2, SST, C1QB, ITGB2, CCR5, CRH, and TAC1), four central regulatory transcription factors (FOXC1, CREB1, GATA2, and HINFP), and four microRNAs (miR-27a-3p, miR-146a-5p, miR-335-5p, and miR-129-2-3p). Hub gene–drug interaction analysis found four drugs (maraviroc, cenicriviroc, PF-04634817, and efalizumab) that could be potential drugs for VaD treatment. Together, our results may contribute to understanding the underlying mechanisms in VaD and provide potential targets and drugs for therapeutic intervention.

Identification of miRNA and Their Regulatory Effects Induced by Total Flavonoids From Dracocephalum moldavica in the Treatment of Vascular Dementia

Vascular dementia (VaD) is a general term used to describe difficulties in memory, reasoning, judgment, and planning caused by a reduced blood flow to the brain and consequent brain damage, in which microRNAs (miRNAs) are involved. Dracocephalum moldavica L. (D. moldavica) is traditionally used in the treatment of cardiovascular diseases as well as VaD, but the biomolecular mechanisms underlying its therapeutic effect are obscure. In the present study, the molecular mechanisms involved in the treatment of VaD by the total flavonoids from Dracocephalum moldavica L. (TFDM) were explored by the identification of miRNA profiling using bioinformatics analysis and experimental verification. A total of 2,562 differentially expressed miRNAs (DEMs) and 3,522 differentially expressed genes (DEGs) were obtained from the GSE120584 and GSE122063 datasets, in which the gene functional enrichment and protein-protein interaction network of 93 core targets, originated from the intersection of the top DEM target genes and DEGs, were established for VaD gene profiling. One hundred and eighty-five targets interacting with 42 flavonoids in the TFDM were included in a compound-target network, subsequently found that they overlapped with potential targets for VaD. These 43 targets could be considered in the treatment of VaD by TFDM, and included CaMKII, MAPK, MAPT, PI3K, and KDR, closely associated with the vascular protective effect of TFDM, as well as anti-oxidative, anti-inflammatory, and anti-apoptotic properties. The subsequent analysis of the compound-target gene-miRNA network indicated that eight miRNAs that mediated 43 targets had a close interaction with TFDM, suggesting that the neuroprotective effects were principally due to kaempferol, apigenin, luteolin, and quercetin, which were mostly associated with the miR-3184-3p/ESR1, miR-6762-3p/CDK1, miR-6777-3p/ESRRA, and other related axes. Furthermore, the in vitro oxygen-glucose deprivation (OGD) model demonstrated that the dysregulation of miR-3184-3p and miR-6875-5p found by qRT-PCR was consistent with the changes in the bioinformatics analysis. TFDM and its active compounds involving tilianin, luteolin, and apigenin showed significant effects on the upregulation of miR-3184-3p and downregulation of miR-6875-5p in OGD-injured cells, in line with the improved cell viability. In conclusion, our findings revealed the underlying miRNA-target gene network and potential targets of TFDM in the treatment of VaD.

Somatostatin and Neuropeptide Y in Cerebrospinal Fluid: Correlations With Amyloid Peptides Aβ1-42 and Tau Proteins in Elderly Patients With Mild Cognitive Impairment

A combination of low cerebrospinal fluid (CSF) Amyloid β_1–42 (Aβ_1–42) and high Total-Tau (T-Tau) and Phosphorylated-Tau (P-Tau) occurs at a prodromal stage of Alzheimer’s disease (AD) and recent findings suggest that network abnormalities and interneurons dysfunction contribute to cognitive deficits. Somatostatin (SOM) and Neuropeptide Y (NPY) are two neuropeptides which are expressed in GABAergic interneurons with different fates in AD the former only being markedly affected. The aim of this study was to analyze CSF SOM, NPY and CSF Aβ_1–42; T-Tau, P-Tau relationships in 43 elderly mild cognitively impairment (MCI) participants from the Biomarker of AmyLoïd pepTide and AlZheimer’s disease Risk (BALTAZAR) cohort. In these samples, CSF SOM and CSF Aβ_1–42 on the one hand, and CSF NPY and CSF T-Tau and P-Tau on the other hand are positively correlated. CSF SOM and NPY concentrations should be further investigated to determine if they can stand for early AD biomarkers.

Clinical Trial Registration: www.ClinicalTrials.gov, identifier #NCT01315639.

Synaptic plasticity modulation by circulating peptides and metaplasticity: Involvement in Alzheimer's disease

Synaptic plasticity is a cellular process involved in learning and memory whose alteration in its two main forms (Long Term Depression (LTD) and Long Term Potentiation (LTP)), is observed in most brain pathologies, including neurodegenerative disorders such as Alzheimer's disease (AD). In humans, AD is associated at the cellular level with neuropathological lesions composed of extracellular deposits of β-amyloid (Aβ) protein aggregates and intracellular neurofibrillary tangles, cellular loss, neuroinflammation and a general brain homeostasis dysregulation. Thus, a dramatic synaptic environment perturbation is observed in AD patients, involving changes in brain neuropeptides, cytokines, growth factors or chemokines concentration and diffusion. Studies performed in animal models demonstrate that these circulating peptides strongly affect synaptic functions and in particular synaptic plasticity. Besides this neuromodulatory action of circulating peptides, other synaptic plasticity regulation mechanisms such as metaplasticity are altered in AD animal models. Here, we will review new insights into the study of synaptic plasticity regulatory/modulatory mechanisms which could influence the process of synaptic plasticity in the context of AD with a particular attention to the role of metaplasticity and peptide dependent neuromodulation.

Neuropeptide Y (NPY) as a therapeutic target for neurodegenerative diseases

Neuropeptide Y (NPY) and NPY receptors are widely expressed in the mammalian central nervous system. Studies in both humans and rodent models revealed that brain NPY levels are altered in some neurodegenerative disorders, such as Alzheimer's disease, Parkinson's disease, Huntington's disease and Machado-Joseph disease. In this review, we will focus on the roles of NPY in the pathological mechanisms of these disorders, highlighting NPY as a neuroprotective agent, as a neural stem cell proliferative agent, as an agent that increases trophic support, as a stimulator of autophagy and as an inhibitor of excitotoxicity and neuroinflammation. Moreover, the effect of NPY in some clinical manifestations commonly observed in Alzheimer's disease, Parkinson's disease, Huntington's disease and Machado-Joseph disease, such as depressive symptoms and body weight loss, are also discussed. In conclusion, this review highlights NPY system as a potential therapeutic target in neurodegenerative diseases.

Effects of insulin and octreotide on memory and growth hormone in Alzheimer's disease

Both insulin alone and the somatostatin analogue octreotide alone facilitate memory in patients with Alzheimer's disease (AD). Since octreotide inhibits endogenous insulin secretion, the cognitive effects of insulin and octreotide may not be independent. This study tested the individual and interactive effects of insulin and octreotide on memory and plasma growth hormone (GH) levels in older adults. Participants were 16 memory-impaired (AD = 7, amnestic mild cognitive impairment = 9; apolipoprotein E [APOE] epsilon4- [no epsilon4 alleles] = 9, epsilon4+ [1-2 epsilon4 alleles] = 7), and 19 cognitively-intact older adults (APOE epsilon4- = 17, epsilon4+ = 1). On separate days, fasting participants received counterbalanced infusions of: 1) insulin (1 mU.kg(-1).min(-1)) and dextrose to maintain euglycemia; 2) octreotide (150 microg/h); 3) insulin, dextrose, and octreotide; or 4) saline. Story recall was the principal endpoint. Insulin alone facilitated delayed recall for epsilon4- patients, relative to epsilon4+ patients (P = 0.0012). Furthermore, epsilon4- patients with higher Mattis Dementia Rating Scale (DRS) scores had greater octreotide-induced memory facilitation (P = 0.0298). For healthy adults, octreotide facilitated memory (P = 0.0122). Unexpectedly, hyperinsulinemia with euglycemia increased GH levels in healthy controls (P = 0.0299). Thus, insulin and octreotide appear to regulate memory in older adults. APOE epsilon4 genotype modulates responses to insulin and octreotide. Finally, insulin may regulate GH levels during euglycemia.

Calcitonin gene-related peptide (CGRP) levels during glyceryl trinitrate (GTN)-induced headache in healthy volunteers

The role of nitric oxide (NO) in migraine has been studied in the experimental glyceryl trinitrate (GTN)-infusion headache model. We hypothesized that GTN-induced headache may activate the trigeminovascular system and be associated with increased levels of sensory neuropeptides, including calcitonin gene-related peptide (CGRP). CGRP, vasoactive intestinal peptide (VIP), neuropeptide Y (NPY) and somatostatin plasma levels were measured before and after placebo/sumatriptan injection and during GTN-induced headache. Following a double-blind randomized cross-over design, 10 healthy volunteers received subcutaneous sumatriptan 6 mg or placebo. This was succeeded by 20 min of GTN (0.12 µg kg−1 min−1) infusion. At baseline no subject reported headache (using verbal rating scale from 0 to 10) and the jugular CGRP-like immunoreactivity (-LI) level was 18.6 ± 2.5 pmol/l. After a 20-min intravenous infusion of GTN 0.12 µg kg−1 min−1, median peak headache intensity was 4 (range 2–6) ( P < 0.05), while jugular CGRP-LI levels were unchanged (19.0 ± 2.8 pmol/l; P > 0.05). There were no changes in VIP-, NPY- or somatostatin-LI. In conclusion, the NO donor GTN appears not to induce headache via immediate CGRP release.

Plasma levels of neuropeptides in Alzheimer's disease

BACKGROUND

In the central nervous system, several neuropeptides are believed to be involved in the pathophysiology of Alzheimer's disease (AD). Indeed, previous studies have documented that glucagon-like peptide 1 (GLP-1) possesses neurotropic properties and can reduce amyloid-beta peptide levels in the brain in vivo. Moreover, the concentrations of neuropeptide Y (NPY) seem to be altered in the cerebrospinal fluid of patients with AD and in subjects with major depression. Finally, among the modifications induced by aging, a dysregulation of the ghrelin-growth hormone (GH) system has been reported.

METHODS

We investigated the plasma concentrations of these neuropeptides in 14 subjects with AD. Data obtained from these patients were compared with data from an age- and weight-matched healthy group.

RESULTS

No significant differences were found between the two groups in relation to plasma levels of GLP-1, NPY, ghrelin and GH. Peripheral NPY concentrations were positively correlated with ghrelin levels in both groups, and with plasma GLP-1 concentration only in controls.

CONCLUSION

On the basis of our results, peripheral levels of these neuropeptides seem not to serve as biochemical markers of AD.

Neurotransmitter depletion may be a cause of dementia pathology rather than an effect

BACKGROUND

There is widespread loss of acetylcholine and other neurotransmitters in Alzheimer's disease and vascular dementia. It has generally been assumed that death of neurons causes neurotransmitter loss, but alternatively neurotransmitter depletion itself may at least contribute to neurodegeneration.

PRESENTATION OF THE HYPOTHESIS

Transgenic mice and pigs with inducible 50% depletion of acetylcholine, dopamine, norepinephrine, serotonin, gamma-aminobutyric acid (GABA) and corticotrophin releasing factor will reproduce Alzheimer's disease or vascular dementia neuropathology, and pharmacologically restoring neurotransmitters will attenuate neuronal injury.

TESTING THE HYPOTHESIS

Through nuclear transfer cloning, transgenic mice and pigs would be created with transgenes on one X chromosome, so that transgenes would only be expressed in half of all cells in female animals. Transgenes would encode tetracycline-inducible short hairpin RNA (shRNA) designed to form small interfering RNA (siRNA) to knock down neurotransmitter biosynthesis in late adulthood. Transgene expressing neurons could be readily identified in tissue sections with fluorescent reporter genes. Cholinesterase inhibitors, antidepressants, benzodiazepines and CRF would then be administered in an attempt to rescue degenerating neurons.

IMPLICATIONS OF THE HYPOTHESIS

The mice and pigs could serve as an important new model for the pathogenesis of dementia, especially if pharmacologically restoring neurotransmitters rescues degenerating neurons. The animals may also be useful for as models for other disorders such as multi-system atrophy, Parkinson's disease, and depression.

Decreased cerebrospinal fluid neuropeptide Y (NPY) in patients with treatment refractory unipolar major depression: preliminary evidence for association with preproNPY gene polymorphism

Extensive animal studies suggest neuropeptide Y (NPY) to be involved in coping with a wide range of stressors, and that impaired central NPY signalling could be involved in the pathophysiology of anxiety and depression. Human studies of central NPY levels in depression have, however, been inconclusive. Here, we examined levels of NPY-like immunoreactivity (NPY-LI) in the cerebrospinal fluid (CSF) of medication-free subjects with treatment refractory unipolar depression. Patients were admitted to a research inpatient unit, examined under standardized conditions, and compared with a sample of volunteers in whom psychiatric morbidity was excluded. A robust suppression of NPY levels in patient CSF was found, while other putative CSF markers (monoamine metabolites, somatostatin) did not differ between the groups. We then explored whether this finding might be related to a recently described T1128C coding polymorphism which results in a Leu7-> Pro7 substitution of the signal peptide, and a previously not described T -399C polymorphism in the promoter region of the preproNPY gene. Preliminary evidence was found for an association of both markers with a diagnosis of depression, indicating the possibility of an underlying haplotype influencing the vulnerability for developing depressive illness. Our present findings are in line with an extensive animal literature, and further support the notion that impaired NPY function could contribute to depressive illness.

CSF galanin and cognition after shunt surgery in normal pressure hydrocephalus

BACKGROUND

"Normal" pressure hydrocephalus (NPH) is associated with injury to neurotransmitter and neuropeptide systems that recovers after surgery. This could be linked to changes in galanin, a neuropeptide with inhibitory effects on basal forebrain cognitive function.

OBJECTIVE

To examine changes in CSF galanin concentrations in patients with normal pressure hydrocephalus undergoing shunt surgery, and to investigate the relation between these changes and cognitive functioning.

METHODS

Eight patients underwent surgery for idiopathic normal pressure hydrocephalus. Lumbar CSF galanin determinations, cognitive status, and clinical status were quantified before operation and six months after. Cognition was assessed by an extensive battery of tests measuring attention, memory, speed of mental processing, visuospatial function, and frontal lobe function.

RESULTS

CSF galanin concentration decreased after surgery. This reduction correlated with improved clinical and cognitive functioning, specifically with attention and visuomotor speed, visuoconstructive and frontal functioning, and clinical status according to the NPH scale, including the sphincter and cognitive components.

CONCLUSIONS

The cognitive and clinical improvement after shunt implantation correlated with CSF galanin levels, suggesting that the distribution or function of this agent involves cerebral structures that have some potential for recovery. In this study, galanin was related to several cognitive functions that may be associated with the fronto-subcortical deficits underlying cognitive dysfunction in normal pressure hydrocephalus.

Opioid-induced proliferation through the MAPK pathway in cultures of adult hippocampal progenitors

Administration of opioid agonists or antagonists has been reported to regulate proliferation or survival of neural progenitors in vivo. Here we report that beta-endorphin and selective mu-opioid receptor (MOR) and delta-opioid receptor (DOR) agonists stimulate proliferation of isolated rat adult hippocampal progenitors (AHPs). The AHPs were found to express DORs and MORs, but not kappa-opioid receptors. Incubation with beta-endorphin for 48 h increased the number of AHPs found in mitosis, the total DNA content, and the expression of proliferating cell nuclear antigen. This proliferative effect from beta-endorphin on AHPs was antagonized by naloxone. The beta-endorphin-induced proliferation was mediated through phosphorylation of extracellular signal-regulated kinases 1 and 2 and dependent on phosphatidylinositol 3-kinase and both intra- and extracellular calcium. These data suggest a role for the opioid system in the regulation of proliferation in progenitors from the adult hippocampus.

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.

Processing of neuropeptide Y, galanin, and somatostatin in the cerebrospinal fluid of patients with Alzheimer's disease and frontotemporal dementia

Alzheimer's disease (AD) and frontotemporal dementia (FTD) are two prevalent neurodegenerative disorders for which the causes are unknown, except in rare familial cases. Several changes in neuropeptide levels as measured by radioimmunoassay (RIA) have been observed in these illnesses. Somatostatin (SOM) levels in cerebrospinal fluid (CSF) are consistently decreased in AD and FTD. Neuropeptide Y (NPY) levels are decreased in AD, but normal in FTD. Galanin (GAL) levels increase with the duration of illness in AD patients. The majority of studies of neuropeptides in CSF have not been verified by HPLC. The observed decrease in a neuropeptide level as measured by RIA may therefore reflect an altered synthesis or extracellular processing, resulting in neuropeptide fragments that may or may not be detected by RIA. Matrix-assisted laser desorption time-of-flight mass spectrometry (MALDI-MS) has been shown to be a powerful technique in the analysis of biological materials without any pre-treatment, by detecting peptides and proteins at a specific mass-to-charge (m/z) ratio. We studied the processing of the neuropeptides NPY, NPY, SOM and GAL in the cerebrospinal fluid of patients with AD (n = 3), FTD (n = 3) and controls (n = 2) using MALDI-MS. We found that considerable inter-individual variability exists in the rate of neuropeptide metabolism in CSF, as well as the number of peptide fragments formed. Certain patients showed differences in the processing of specific neuropeptides, relative to other patients and controls. This analysis of the metabolic processing of neuropeptides in CSF yielded a large amount of data for each individual studied. Further studies are required to determine the changes in neuropeptide processing that can be associated with AD and FTD. With further investigations using MALDI-MS analysis, it may be possible to identify a neuropeptide fragment or processing enzyme that can be correlated to these disease states.

Neuropeptide Y, peptide YY and aluminum in Alzheimer's disease: is there an etiological relationship?

Neuropeptide Y (NPY) and peptide YY (PYY) are members of the pancreatic polypeptide family which have a high degree of primary and tertiary structural homology. They function as neurotransmitters and humoral agents in central nervous system and gastrointestinal function. During the last two decades, NPY body fluid concentrations and NPY/PYY brain receptor numbers have been demonstrated to be altered during the course of Alzheimer's disease. Recent research has shown that both NPY and PYY may be involved in aluminum metabolism in animal models. A brief discussion of the structure, biological activity and possible involvement of these peptides in aluminum metabolism and Alzheimer's disease is contained herein.

Shunt related changes in somatostatin, neuropeptide Y, and corticotropin releasing factor concentrations in patients with normal pressure hydrocephalus

OBJECTIVES

Recent data indicate that alterations in brain neuropeptides may play a pathogenic role in dementia. Neuropeptide Y (NPY), somastostatin (SOM), and corticotropin releasing factor (CRF) are neuropeptides involved in cognitive performance. Decreased SOM and NPY concentrations have been found in patients with normal pressure hydrocephalus and are probably the result of neuronal dysfunction, which could potentially be restored by shunting. The effects of shunt surgery on preoperative SOM, NPY, and CRF concentrations were studied. Any improvements in neuropeptide concentrations that could lead to clinically significant neuropsychological and functional changes were also investigated.

METHODS

A prospective study was performed in 14 patients with normal pressure hydrocephalus syndrome with a duration of symptoms between 3 months and 12 years. Diagnosis was based on intracranial pressure (ICP) monitoring and CSF dynamics. Concentrations of SOM, NPY, and CRF in lumbar CSF were determined before shunting and again 6-9 months after surgery. A battery of neuropsychological tests and several rating functional scales were also given to patients before and after shunting.

RESULTS

After shunting, SOM and CRF concentrations were significantly increased in all patients. Concentrations of NPY were increased in 12 of the 14 patients studied. The clinical condition of 13 of the 14 patients was significantly improved 6 months after surgery. This improvement was more pronounced in gait disturbances and sphincter dysfunction than in cognitive impairment. No significant differences in any of the neuropsychological tests were seen for the group of patients as a whole despite the increased neuropeptide concentrations.

CONCLUSIONS

Shunting can restore SOM, NPY, and CRF concentrations even in patients with longstanding normal pressure hydrocephalus. However, despite the biochemical and clinical improvement in some areas such as ambulation and daily life activities, cognitive performance did not significantly improve. The role of neuropeptides in the diagnosis and treatment of patients with normal pressure hydrocephalus syndrome is discussed.

The leucine (7)-to-proline (7) polymorphism in the signal peptide of neuropeptide Y is not associated with Alzheimer's disease or the link apolipoprotein E

Both apolipoprotein E varepsilon4 allele (APOE varepsilon4) and neuropeptide Y (NPY) Pro(7)-variant have been reported to be associated with higher serum levels of total and LDL cholesterol. Since APOE varepsilon4 allele is also a major risk factor for the development of Alzheimer's disease (AD) and the genetic polymorphism of NPY has not previously been studied in dementing disorders, we have examined whether a novel polymorphism in a signal peptide of NPY gene is associated with AD alone or in combination with APOE varepsilon4. A total of 125 sporadic AD cases and 110 control individuals from Finland were genotyped for APOE and NPY genes using the polymerase chain reaction and restriction enzyme analysis. The APOE varepsilon4 allele frequency was significantly increased in the AD group compared with controls as expected. Instead, no significant differences were found between sporadic AD patients and controls either in the NPY genotype or allele frequencies or in combination with the APOE varepsilon4 allele. We conclude that APOE varepsilon4 allele represents a strong predictor of risk for AD.

Essential fatty acids and sleep: mini-review and hypothesis

The neurochemical basis of sleep mechanisms (onset and maintenance) is still controversial although the phenomenon itself is known to be mediated by more than a single molecule. The list of suggested endogenous sleep substances is rather long, and there is no single 'sleep center' identified in the brain. The role of fatty acids, and essential fatty acids in particular, has been ignored in sleep research. This review proposes an integration of the current knowledge about the effects of fatty acids in sleep neurochemistry, wherein fatty acids are seen to exert a direct effect on neuronal membrane structure or indirectly on the dynamics of biochemical compounds (complex lipids, prostaglandins, neurotransmitters, amino acids, interleukins) necessary for the initiation and maintenance of sleep.

Processing of neuropeptide Y and somatostatin in human cerebrospinal fluid as monitored by radioimmunoassay and mass spectrometry

The processing of four neuropeptides, neuropeptide Y (NPY) 1-36, NPY (18-36), somatostatin (SOM) 1-28, and SOM (15-28) was studied in human cerebrospinal fluid (CSF) by using a novel combination of methods that included radioimmunoassay (RIA) and mass spectrometry. Untreated CSF samples were chromatographed using reversed-phase high pressure liquid chromatography (RP-HPLC) followed by NPY-RIA or SOM-RIA. These results were compared with those obtained by incubating CSF with exogenous synthetic peptides and directly detecting peptide fragments by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-MS). Using this combination of methods, we were able to determine the probable identities of peptides/peptide fragments recognized in radioimmunoassays. The most important NPY-immunoreactive components in CSF were found to be NPY (1-36) and NPY (3-36). Metabolic products of SOM (15-28) were found to contribute to SOM-like immunoreactivity (SOM-LI) in CSF, but SOM (1-28) only to a lesser degree. Differences in the rate of neuropeptide processing were observed. These differences depended more on the length of the peptide than its sequence. NPY (18-36) and SOM (15-28) were rapidly and extensively processed, whereas NPV (1-36) and SOM (1-28) were processed much more slowly in CSF. The production of SOM (15-28) from SOM (1-28) by enzymes in CSF was not observed. Also, the presence of a disulfide bond in the somatostatins appeared to stabilize them against enzymatic digestion of the ring structure. The results detailed in this report confirm MALDI-MS important role in studies of neuropeptide processing in CSF.