Differential effects of amyloid-beta 1–40 and 1–42 fibrils on 5-HT 1A serotonin receptors in rat brain

Accelerating protein aggregation and amyloid fibrillation for rapid inhibitor screening

The accumulation and deposition of amyloid fibrils, also known as amyloidosis, in tissues and organs of patients has been found to be linked to numerous devastating neurodegenerative diseases. The aggregation of proteins to form amyloid fibrils, however, is a slow pathogenic process, and is a major issue for the evaluation of the effectiveness of inhibitors in new drug discovery and screening. Here, we used microdroplet reaction technology to accelerate the amyloid fibrillation process, monitored the process to shed light on the fundamental mechanism of amyloid self-assembly, and demonstrated the value of the technology in the rapid screening of potential inhibitor drugs. Proteins in microdroplets accelerated to form fibrils in milliseconds, enabling an entire cycle of inhibitor screening for Aβ40 within 3 minutes. The technology would be of broad interest to drug discovery and therapeutic design to develop treatments for diseases associated with protein aggregation and fibrillation.

Serotonergic and Adrenergic Neuroreceptor Manipulation Ameliorates Core Symptoms of ADHD through Modulating Dopaminergic Receptors in Spontaneously Hypertensive Rats

The core symptoms of attention deficit hyperactivity disorder (ADHD) are due to the hypofunction of the brain's adrenergic (NE) and dopamine (DA) systems. Drugs that enhance DA and NE neurotransmission in the brain by blocking their transporters or receptors are the current therapeutic strategies. Of late, the emerging results point out the serotonergic (5-HT) system, which indirectly modulates the DA activity in reducing the core symptoms of ADHD. On this basis, second-generation antipsychotics, which utilize 5-HT receptors, were prescribed to children with ADHD. However, it is not clear how serotonergic receptors modulate the DA activity to minimize the symptoms of ADHD. The present study investigates the efficacy of serotonergic and alpha-2 adrenergic receptor manipulation in tackling the core symptoms of ADHD and how it affects the DA neuroreceptors in the brain regions involved in ADHD. Fifteen-day-old male spontaneously hypertensive rats (SHRs) received 5-HT1A agonist (ipsapirone) or 5-HT2A antagonist (MDL 100907) (i.p.) or alpha-2 agonist (GFC) from postnatal days 15 to 42 along with age-matched Wistar Kyoto rats (WKY) (n = 8 in each group). ADHD-like behaviors were assessed using a battery of behavioral tests during postnatal days 44 to 65. After the behavioral tests, rat brains were processed to estimate the density of 5-HT1A, 5-HT2A, DA-D1, and DA-D2 neuroreceptors in the prefrontal cortex, the striatum, and the substantia nigra. All three neuroreceptor manipulations were able to minimize the core symptoms of ADHD in SHRs. The positive effect was mainly associated with the upregulation of 5-HT2A receptors in all three areas investigated, while 5-HT1A was in the prefrontal cortex and the substantia nigra. Further, the DA-D1 receptor expression was downregulated by all three neuroreceptor manipulations except for alpha-2 adrenergic receptor agonists in the striatum and 5-HT2A antagonists in the substantia nigra. The DA-D2 expression was upregulated in the striatum while downregulated in the prefrontal cortex and the substantia nigra. In this animal model study, the 5-HT1A agonist or 5-HT2A antagonist monotherapies were able to curtail the ADHD symptoms by differential expression of DA receptors in different regions of the brain.

Ameliorative and Neuroprotective Effect of Core-Shell Type Se@Au Conjugated Hesperidin Nanoparticles in Diabetes-Induced Cognitive Impairment

Diabetes mellitus is the most chronic metabolic ailment characterized by insulin deficiency leading to aberrant cognitive dysfunction in later stages. Hesperidin is a bioflavonoid, having different pharmacological activities, but its poor water solubility and short plasma half-life restrict its applications in the clinical field. So, the hesperidin was conjugated with gold, selenium, and core-shell bimetallic nanoparticles of gold and selenium. Different spectroscopic methods characterized the synthesized monometallic and bimetallic nanoparticles. The rats were injected with streptozotocin to induce cognitive dysfunction, followed by administering HSP, HSP-Au NPs, HSP-Se NPs, and Se@Au-HSP NPs daily for 21 days. Then, the neurobehavioral studies, oxidative stress parameters, AChE and nitrite levels, the content of amyloid-β42, and inflammatory mediators were accessed to evaluate the effect of the nanoparticles against the STZ rat model. The results showed a significant increase in oxidative stress, AChE activity, amyloid-β42, nitrite levels, and neuroinflammation by upregulating the inflammatory cytokines in the streptozotocin-administered rat brain. The HSP, HSP-Au NPs, HSP-Se NPs, and Se@Au-HSP NPs effectively reversed all these effects of streptozotocin. However, the bimetallic nanoparticle Se@Au-HSP NPs revealed better neuroprotective action than HSP-Au NPs and HSP-Se NPs. Hesperidin-conjugated bimetallic nanoparticles improved learning and memory in the STZ rat model and may be an alternative approach for neurodegenerative diseases, including Alzheimer's disease.

Serotonin Receptors as a Potential Target in the Treatment of Alzheimer's Disease

Alzheimer's disease (AD) is the most common cause of dementia worldwide that has an increasing impact on aging societies. Besides its critical role in the control of various physiological functions and behavior, brain serotonin (5-HT) system is involved in the regulation of migration, proliferation, differentiation, maturation, and programmed death of neurons. At the same time, a growing body of evidence indicates the involvement of 5-HT neurotransmission in the formation of insoluble aggregates of β-amyloid and tau protein, the main histopathological signs of AD. The review describes the role of various 5-HT receptors and intracellular signaling cascades induced by them in the pathological processes leading to the development of AD, first of all, in protein aggregation. Changes in the functioning of certain types of 5-HT receptors or associated intracellular signaling mediators prevent accumulation of β-amyloid plaques and tau protein neurofibrillary tangles. Based on the experimental data, it can be suggested that the use of 5-HT receptors as new drug targets will not only improve cognitive performance in AD, but will be also important in treating the causes of AD-related dementia.

In vivo targeting and multimodal imaging of cerebral amyloid-β aggregates using hybrid GdF3 nanoparticles

Aim: To propose a new multimodal imaging agent targeting amyloid-β (Aβ) plaques in Alzheimer's disease. Materials & methods: A new generation of hybrid contrast agents, based on gadolinium fluoride nanoparticles grafted with a pentameric luminescent-conjugated polythiophene, was designed, extensively characterized and evaluated in animal models of Alzheimer's disease through MRI, two-photon microscopy and synchrotron x-ray phase-contrast imaging. Results & conclusion: Two different grafting densities of luminescent-conjugated polythiophene were achieved while preserving colloidal stability and fluorescent properties, and without affecting biodistribution. In vivo brain uptake was dependent on the blood-brain barrier status. Nevertheless, multimodal imaging showed successful Aβ targeting in both transgenic mice and Aβ fibril-injected rats.

Understanding How Physical Exercise Improves Alzheimer’s Disease: Cholinergic and Monoaminergic Systems

Alzheimer’s disease (AD) is an age-related neurodegenerative disorder, characterized by the accumulation of proteinaceous aggregates and neurofibrillary lesions composed of β-amyloid (Aβ) peptide and hyperphosphorylated microtubule-associated protein tau, respectively. It has long been known that dysregulation of cholinergic and monoaminergic (i.e., dopaminergic, serotoninergic, and noradrenergic) systems is involved in the pathogenesis of AD. Abnormalities in neuronal activity, neurotransmitter signaling input, and receptor function exaggerate Aβ deposition and tau hyperphosphorylation. Maintenance of normal neurotransmission is essential to halt AD progression. Most neurotransmitters and neurotransmitter-related drugs modulate the pathology of AD and improve cognitive function through G protein-coupled receptors (GPCRs). Exercise therapies provide an important alternative or adjunctive intervention for AD. Cumulative evidence indicates that exercise can prevent multiple pathological features found in AD and improve cognitive function through delaying the degeneration of cholinergic and monoaminergic neurons; increasing levels of acetylcholine, norepinephrine, serotonin, and dopamine; and modulating the activity of certain neurotransmitter-related GPCRs. Emerging insights into the mechanistic links among exercise, the neurotransmitter system, and AD highlight the potential of this intervention as a therapeutic approach for AD.

Sustained Hippocampal Neural Plasticity Questions the Reproducibility of an Amyloid-β-Induced Alzheimer's Disease Model

BACKGROUND

The use of Alzheimer's disease (AD) models obtained by intracerebral infusion of amyloid-β (Aβ) has been increasingly reported in recent years. Nonetheless, these models may present important challenges.

OBJECTIVE

We have focused on canonical mechanisms of hippocampal-related neural plasticity to characterize a rat model obtained by an intracerebroventricular (icv) injection of soluble amyloid-β42 (Aβ42).

METHODS

Animal behavior was evaluated in the elevated plus maze, Y-Maze spontaneous or forced alternation, Morris water maze, and open field, starting 2 weeks post-Aβ42 infusion. Hippocampal neurogenesis was assessed 3 weeks after Aβ42 injection. Aβ deposition, tropomyosin receptor kinase B levels, and neuroinflammation were appraised at 3 and 14 days post-Aβ42 administration.

RESULTS

We found that immature neuronal dendritic morphology was abnormally enhanced, but proliferation and neuronal differentiation in the dentate gyrus was conserved one month after Aβ42 injection. Surprisingly, animal behavior did not reveal changes in cognitive performance nor in locomotor and anxious-related activity. Brain-derived neurotrophic factor related-signaling was also unchanged at 3 and 14 days post-Aβ icv injection. Likewise, astrocytic and microglial markers of neuroinflammation in the hippocampus were unaltered in these time points.

CONCLUSION

Taken together, our data emphasize a high variability and lack of behavioral reproducibility associated with these Aβ injection-based models, as well as the need for its further optimization, aiming at addressing the gap between preclinical AD models and the human disorder.

Translating biased agonists from molecules to medications: Serotonin 5-HT1A receptor functional selectivity for CNS disorders

Biased agonism (or "functional selectivity") at G-protein-coupled receptors has attracted rapidly increasing interest as a means to improve discovery of more efficacious and safer pharmacotherapeutics. However, most studies are limited to in vitro tests of cellular signaling and few biased agonists have progressed to in vivo testing. As concerns 5-HT_1A receptors, which exert a major control of serotonergic signaling in diverse CNS regions, study of biased agonism has previously been limited by the poor target selectivity and/or partial agonism of classically available ligands. However, a new generation of highly selective, efficacious and druggable agonists has advanced the study of biased agonism at this receptor and created new therapeutic opportunities. These novel agonists show differential properties for G-protein signaling, cellular signaling (particularly pERK), electrophysiological effects, neurotransmitter release, neuroimaging by PET and pharmacoMRI, and behavioral tests of mood, motor activity and side effects. Overall, NLX-101 (a.k.a. F15599) exhibits preferential activation of cortical and brain stem 5-HT_1A receptors, whereas NLX-112 (a.k.a. befiradol or F13640) shows prominent activation of 5-HT_1A autoreceptors in Raphe nuclei and in regions associated with motor control. Accordingly, NLX-101 is potently active in rodent models of depression and respiratory control, whereas NLX-112 shows promising activity in models of Parkinson's disease across several species - rat, marmoset and macaque. Moreover, NLX-112 has also been labeled with ¹⁸F to produce the first agonist PET radiopharmaceutical (known as [¹⁸F]-F13640) for investigation of the active state of 5-HT_1A receptors in rodent, primate and human. The structure-functional activity relationships of biased agonists have been investigated by receptor modeling and novel compounds have been identified which exhibit increased affinity at 5-HT_1A receptors and new profiles of cellular signaling bias, notably for β-arrestin recruitment versus pERK. Taken together, the data suggest that 5-HT_1A receptor biased agonists constitute potentially superior pharmacological agents for treatment of CNS disorders involving serotonergic mechanisms.

Alogliptin reversed hippocampal insulin resistance in an amyloid-beta fibrils induced animal model of Alzheimer's disease

The complications of Alzheimer's disease (AD) have made the development of its treatment a challenging task. Several studies have indicated the disruption of insulin receptor substrate-1 (IRS-1) signaling during the development and progression of AD. The role of a dipeptidyl peptidase-4 (DPP-4) inhibitor on hippocampal IRS-1 signaling has not been investigated before. In this study, we evaluated the efficacy of alogliptin (DPP-4 inhibitor) on hippocampal insulin resistance and associated AD complications. In the present study, amyloid-β (1-42) fibrils were produced and administered intrahippocampally for inducing AD in Wistar rats. After 7 days of surgery, rats were treated with 10 and 20 mg/kg of alogliptin for 28 days. Morris water maze (MWM) test was performed in the last week of our experimental study. Post 24 h of final treatment, rats were euthanized and hippocampi were separated for biochemical and histopathological investigations. In-silico analysis revealed that alogliptin has a good binding affinity with Aβ and beta-secretase-1 (BACE-1). Alogliptin significantly restored cognitive functions in Aβ (1-42) fibrils injected rats during the MWM test. Alogliptin also significantly attenuated insulin level, IRS-1pS307 expression, Aβ (1-42) level, GSK-3β activity, TNF-α level and oxidative stress in the hippocampus. The histopathological analysis supported alogliptin mediated neuroprotective and anti-amyloidogenic effect. Immunohistochemical analysis also revealed a reduction in IRS-1pS307 expression after alogliptin treatment. The in-silico, behavioral, biochemical and histopathological analysis supports the protective effect of alogliptin against hippocampal insulin resistance and AD.

Potentiation of NMDA-Mediated Responses by Amyloid-β Peptide 1-40 in Rat Sympathetic Preganglionic Neurons

The abnormal accumulation of amyloid-β peptides (Aβ) is one of the main characteristics of Alzheimer's disease (AD). Cerebro- and cardiovascular diseases may be the risk factors for developing AD. The effect of Aβ on central sympathetic control of cardiovascular function remains unclear. The present study examines the acute effects of Aβ oligomers on the function of NMDA receptors, a subtype of ionotropic glutamate receptors, in rat sympathetic preganglionic neurons (SPNs). In the in vitro electrophysiological study, Aβ1-40 but not Aβ1-42 applied by superfusion for 5 min significantly potentiated NMDA-induced depolarizations in SPNs of neonatal rat spinal cord slice preparation. Application of Aβ1-40 had little effects on AMPA-induced depolarizations or GABA-induced hyperpolarizations. Treatment with a selective protein kinase C (PKC) inhibitor applied together with Aβ1-40 blocked the augmentation by Aβ1-40 of NMDA-induced depolarizations. Western blot analysis showed an increase in the levels of phosphoserine 896, selectively regulated by PKC, without significant changes in phosphoserine 897 on GluN1 subunits in lateral horn areas of spinal cord slices following treatment with Aβ1-40. In the in vivo study, intrathecal injection of Aβ1-40 (0.2 nmol) potentiated the pressor effects induced by NMDA (2 nmol) injected intrathecally in urethane-anesthetized rats. These results suggest that different fragments of Aβ may have differential effects on the NMDA receptor function and the selective augmentation of NMDA receptor function by Aβ1-40 may involve PKC-dependent mechanisms in sympathetic preganglionic neurons.

Effects of Gentiana delavayi Flower Extract on APP Processing in APP/PS1 CHO Cells

ETHNOPHARMACOLOGICAL RELEVANCE

Gentiana delavayi Franch. (Gentianaceae) as an ethnomedicinal plant contains a variety of effective active ingredients and exhibits diverse pharmacological actions, such as hepatoprotective, anti-inflammatory and central nervous system effects. In this study we investigated the influence of G. delavayi flower extract on amyloid precursor protein (APP) processing at molecular and cellular levels. APP/PS1 Chinese hamster ovary (CHO) cells were treated with chloroform extract of G. delavayi flower in different concentrations for 24 h. Concentrations of amyloid β (Aβ) 40 and Aβ42 in the cell supernatant and activity of β-site amyloid precursor protein cleaving enzyme 1 (BACE1), BACE2, and cathepsin D were determined. The expression of APP and neprilysin (NEP) within the cell were further determined. Compared with the control group, the levels of Aβ40 and Aβ42 declined notably and the activity of BACE1 was inhibited significantly in the APP/PS1 CHO cells after treatment with the chloroform extract of G. delavayi flower. Although the activities of BACE2 and cathepsin D were not changed, the expression of Aβ degrading enzyme NEP increased remarkably. Our experiments have clearly showed that the chloroform extract of G. delavayi flower inhibits the generation of β-amyloid by specifically inhibiting β-secretase and increases the expression of NEP which fastens the degradation of Aβ, exhibiting the effect of decreasing Aβ accumulation in APP/PS1 CHO cells. These results suggest that the active components from the chloroform extract of G. delavayi flower have a further prospect to be developed as potential anti-Aβ drug.

Learning from amyloid trials in Alzheimer's disease. A virtual patient analysis using a quantitative systems pharmacology approach

BACKGROUND

Many trials of amyloid-modulating agents fail to improve cognitive outcome in Alzheimer's disease despite substantial reduction of amyloid β levels.

METHODS

We applied a mechanism-based Quantitative Systems Pharmacology model exploring the pharmacodynamic interactions of apolipoprotein E (APOE), Catechol -O -methyl Transferase (COMTVal158Met), and 5-HT transporter (5-HTTLPR) rs25531 genotypes and aducanumab.

RESULTS

The model predicts large clinical variability. Anticipated placebo differences on Alzheimer's Disease Assessment Scale (ADAS)-COG in the aducanumab ENGAGE and EMERGE ranged from 0.77 worsening to 1.56 points improvement, depending on the genotype-comedication combination. 5-HTTLPR L/L subjects are found to be the most resilient. Virtual patient simulations suggest improvements over placebo between 4% and 20% at the 10 mg/kg dose, depending on the imbalance of the 5-HTTLPR genotype and exposure. In the Phase II PRIME trial, maximal anticipated placebo difference at 10 mg/kg ranges from 0.3 worsening to 5.3 points improvement.

DISCUSSION

These virtual patient simulations, once validated against clinical data, could lead to better informed future clinical trial designs.

The apparent mechanical effect of isolated amyloid-β and α-synuclein aggregates revealed by multi-frequency MRE

Several biological processes are involved in dementia, and fibrillar aggregation of misshaped endogenous proteins appears to be an early hallmark of neurodegenerative disease. A recently developed means of studying neurodegenerative diseases is magnetic resonance elastography (MRE), an imaging technique investigating the mechanical properties of tissues. Although mechanical changes associated with these diseases have been detected, the specific signal of fibrils has not yet been isolated in clinical or preclinical studies. The current study aims to exploit the fractal-like properties of fibrils to separate them from nonaggregated proteins using a multi-frequency MRE power law exponent in a phantom study. Two types of fibril, α-synuclein (α-Syn) and amyloid-β (Aβ), and a nonaggregated protein, bovine serum albumin, used as control, were incorporated in a dedicated nondispersive agarose phantom. Elastography was performed at multiple frequencies between 400 and 1200 Hz. After 3D-direct inversion, storage modulus (G'), phase angle (ϕ), wave speed and the power law exponent (y) were computed. No significant changes in G' and ϕ were detected. Both α-Syn and Aβ inclusions showed significantly higher y values than control inclusions (P = 0.005) but did not differ between each other. The current phantom study highlighted a specific biomechanical effect of α-Syn and Aβ aggregates, which was better captured with the power law exponent derived from multi-frequency MRE than with single frequency-derived parameters.

Protective Effects of 5-HT1A Receptor Inhibition and 5-HT2A Receptor Stimulation Against Streptozotocin-Induced Apoptosis in the Hippocampus

INTRODUCTION

Intracerebroventricular administration of streptozotocin (icv-STZ) induced apoptosis changes in neurons similar to Alzheimer's disease. The serotonergic system via its receptor involved in survival of neurons. The present study examined the ability of selective 5-HT1A receptor antagonist (NAD-299) and 5-HT2A receptor agonist (TCB-2) to attenuate the apoptosis caused by the icv-STZ in the rat.

METHODS

The icv-STZ (3 mg/kg, 10 μL, twice) induced neuronal loss in the hippocampus of adult male rats. Animals were divided into naive control, sham-operated, STZ+saline (1 μL, icv), STZ+NAD-299 (5 μg/μL, icv), STZ+TCB-2 (5 μg/μL, icv), and STZ+NAD-299+TCB-2 (5 μg/μL of any agent, icv) groups. Following the 35 days' treatment period, neuronal apoptosis was detected using the Tunnel. Cells with morphological features of apoptotic cell were contended by microscopy.

RESULTS

TCB-2 and NAD-299 administration decreased number of apoptotic neurons in the treatment group compared with the STZ group. Combined treatment of STZ rat with NAD+TCB more decreased number of apoptotic cells in compare to TCB-2 or NAD-299 treated STZ groups.

CONCLUSION

Treatment with 5-HT1A receptor antagonist or 5-HT2A receptor agonist diminished apoptosis. The beneficial effect of 5HT1A receptor inhibition was potentiated with activation of 5-HT2A receptor in prevention of apoptosis in hippocampus.

Impact of amyloid-beta changes on cognitive outcomes in Alzheimer's disease: analysis of clinical trials using a quantitative systems pharmacology model

BACKGROUND

Despite a tremendous amount of information on the role of amyloid in Alzheimer's disease (AD), almost all clinical trials testing this hypothesis have failed to generate clinically relevant cognitive effects.

METHODS

We present an advanced mechanism-based and biophysically realistic quantitative systems pharmacology computer model of an Alzheimer-type neuronal cortical network that has been calibrated with Alzheimer Disease Assessment Scale, cognitive subscale (ADAS-Cog) readouts from historical clinical trials and simulated the differential impact of amyloid-beta (Aβ40 and Aβ42) oligomers on glutamate and nicotinic neurotransmission.

RESULTS

Preclinical data suggest a beneficial effect of shorter Aβ forms within a limited dose range. Such a beneficial effect of Aβ40 on glutamate neurotransmission in human patients is absolutely necessary to reproduce clinical data on the ADAS-Cog in minimal cognitive impairment (MCI) patients with and without amyloid load, the effect of APOE genotype effect on the slope of the cognitive trajectory over time in placebo AD patients and higher sensitivity to cholinergic manipulation with scopolamine associated with higher Aβ in MCI subjects. We further derive a relationship between units of Aβ load in our model and the standard uptake value ratio from amyloid imaging. When introducing the documented clinical pharmacodynamic effects on Aβ levels for various amyloid-related clinical interventions in patients with low Aβ baseline, the platform predicts an overall significant worsening for passive vaccination with solanezumab, beta-secretase inhibitor verubecestat and gamma-secretase inhibitor semagacestat. In contrast, all three interventions improved cognition in subjects with moderate to high baseline Aβ levels, with verubecestat anticipated to have the greatest effect (around ADAS-Cog value 1.5 points), solanezumab the lowest (0.8 ADAS-Cog value points) and semagacestat in between. This could explain the success of many amyloid interventions in transgene animals with an artificial high level of Aβ, but not in AD patients with a large variability of amyloid loads.

CONCLUSIONS

If these predictions are confirmed in post-hoc analyses of failed clinical amyloid-modulating trials, one should question the rationale behind testing these interventions in early and prodromal subjects with low or zero amyloid load.

Intermittent fasting protects against the deterioration of cognitive function, energy metabolism and dyslipidemia in Alzheimer's disease-induced estrogen deficient rats

Intermittent fasting may be an effective intervention to protect against age-related metabolic disturbances, although it is still controversial. Here, we investigated the effect of intermittent fasting on the deterioration of the metabolism and cognitive functions in rats with estrogen deficiency and its mechanism was also explored. Ovariectomized rats were infused with β-amyloid (25-35; Alzheimer's disease) or β-amyloid (35-25, Non-Alzheimer's disease; normal cognitive function) into the hippocampus. Each group was randomly divided into two sub-groups: one with intermittent fasting and the other fed ad libitum: Alzheimer's disease-ad libitum, Alzheimer's disease-intermittent fasting, Non-Alzheimer's disease-ad libitum, and Non-Alzheimer's disease-intermittent fasting. Rats in the intermittent fasting groups had a restriction of food consumption to a 3-h period every day. Each group included 10 rats and all rats fed a high-fat diet for four weeks. Interestingly, Alzheimer's disease increased tail skin temperature more than Non-Alzheimer's disease and intermittent fasting prevented the increase. Alzheimer's disease reduced bone mineral density in the spine and femur compared to the Non-Alzheimer's disease, whereas bone mineral density in the hip and leg was reduced by intermittent fasting. Fat mass only in the abdomen was decreased by intermittent fasting. Intermittent fasting decreased food intake without changing energy expenditure. Alzheimer's disease increased glucose oxidation, whereas intermittent fasting elevated fat oxidation as a fuel source. Alzheimer's disease and intermittent fasting deteriorated insulin resistance in the fasting state but intermittent fasting decreased serum glucose levels after oral glucose challenge by increasing insulin secretion. Alzheimer's disease deteriorated short and spatial memory function compared to the Non-Alzheimer's disease, whereas intermittent fasting prevented memory loss in comparison to ad libitum. Unexpectedly, cortisol levels were increased by Alzheimer's disease but decreased by intermittent fasting. Intermittent fasting improved dyslipidemia and liver damage index compared to ad libitum. Alzheimer's disease lowered low-density lipoprotein cholesterol and serum triglyceride levels compared to Non-Alzheimer's disease. In conclusion, Alzheimer's disease impaired not only cognitive function but also disturbed energy, glucose, lipid, and bone metabolism in ovariectomized rats. Intermittent fasting protected against the deterioration of these metabolic parameters, but it exacerbated bone mineral density loss and insulin resistance at fasting in Alzheimer's disease-induced estrogen-deficient rats. Impact statement Intermittent fasting was evaluated for its effects on cognitive function and metabolic disturbances in a rat model of menopause and Alzheimer's disease. Intermittent fasting decreased skin temperature and fat mass, and improved glucose tolerance with decreasing food intake. Intermittent fasting also prevented memory loss: short-term and special memory loss. Therefore, intermittent fasting may prevent some of the metabolic pathologies associated with menopause and protect against age-related memory decline.

Frameworking memory and serotonergic markers

The evidence for neural markers and memory is continuously being revised, and as evidence continues to accumulate, herein, we frame earlier and new evidence. Hence, in this work, the aim is to provide an appropriate conceptual framework of serotonergic markers associated with neural activity and memory. Serotonin (5-hydroxytryptamine [5-HT]) has multiple pharmacological tools, well-characterized downstream signaling in mammals’ species, and established 5-HT neural markers showing new insights about memory functions and dysfunctions, including receptors (5-HT1A/1B/1D, 5-HT2A/2B/2C, and 5-HT3-7), transporter (serotonin transporter [SERT]) and volume transmission present in brain areas involved in memory. Bidirectional influence occurs between 5-HT markers and memory/amnesia. A growing number of researchers report that memory, amnesia, or forgetting modifies neural markers. Diverse approaches support the translatability of using neural markers and cerebral functions/dysfunctions, including memory formation and amnesia. At least, 5-HT1A, 5-HT4, 5-HT6, and 5-HT7receptors and SERT seem to be useful neural markers and therapeutic targets. Hence, several mechanisms cooperate to achieve synaptic plasticity or memory, including changes in the expression of neurotransmitter receptors and transporters.

Screening of the TBK1 gene in familial and sporadic amyotrophic lateral sclerosis patients of Chinese origin

TANK-binding kinase 1 (TBK1) has been recently identified as a risk gene of amyotrophic lateral sclerosis (ALS). The aim of this study was to assess the contribution of TBK1 mutations to Chinese ALS patients. We sequenced the coding regions of TBK1 in a cohort of Chinese ALS patients, including 271 sporadic ALS patients and 23 familial ALS patients. Two potentially pathogenic mutations, L62P and I334T, were identified in two independent sporadic ALS patients, accounting for 0.7% of total ALS cases. Both mutations were absent from our 384 healthy controls and public single nucleotide polymorphisms databases. In conclusion, we propose that TBK1 is not a frequent causal gene in Chinese ALS patients.

Agonist and antagonist bind differently to 5-HT1A receptors during Alzheimer's disease: A post-mortem study with PET radiopharmaceuticals

PET imaging studies using 5-HT1A receptor radiotracers show a decreased density of this receptor in hippocampi of patients with Alzheimer's disease (AD) at advanced stages. However, current 5-HT1A receptor radiopharmaceuticals used in neuroimaging are antagonists, thought to bind to 5-HT1A receptors in different functional states (i.e., both the one which displays high affinity for agonists and is thought to mediate receptor activation, as well as the state which has low affinity for agonists). Comparing the PET imaging obtained using an agonist radiotracer, which binds selectively to functional receptors, with the PET imaging obtained using an antagonist radiotracer would therefore provide original information on 5-HT1A receptor impairment during AD. Quantitative autoradiography using [(18)F]F13640 and [(18)F]MPPF, a 5-HT1A agonist and antagonist, respectively, was measured in hippocampi of patients with AD (n = 25, at different Braak stages) and control subjects (n = 9). The neuronal density was measured in the same tissues by NeuN immunohistochemistry. The specific binding of both radiotracers was determined by addition of WAY-100635, a selective 5-HT1A receptor antagonist. The autoradiography distribution of both 5-HT1A PET radiotracers varied across hippocampus regions. The highest binding density was in the pyramidal layer of CA1. Incubation with Gpp(NH)p, a non-hydrolysable analogue of GTP, reduced significantly [(18)F]F13640 binding in hippocampal regions, confirming its preferential interaction with G-coupled receptors, and slightly increased [(18)F]MPPF binding. In the CA1 subfield, [(18)F]F13640 binding was significantly decreased at Braak stages I/II (-19%), Braak stages III/IV (-23%), and Braak stages V/VI (-36%) versus control. In contrast, [(18)F]MPPF binding was statistically reduced only at the most advanced Braak stages V/VI compared to control (-33%). Since [(18)F]F13640 and [(18)F]MPPF can be used in vivo in humans, this neuropharmacological paradigm supports testing the concept of functional imaging using agonist radiopharmaceuticals in future clinical studies.