A TrkB and TrkC partial agonist restores deficits in synaptic function and promotes activity-dependent synaptic and microglial transcriptomic changes in a late-stage Alzheimer's mouse model.

INTRODUCTION: Tropomyosin related kinase B (TrkB) and C (TrkC) receptor signaling promotes synaptic plasticity and interacts with pathways affected by amyloid beta (Aß) toxicity. Upregulating TrkB/C signaling could reduce Alzheimer's disease (AD)-related degenerative signaling, memory loss, and synaptic dysfunction. METHODS: PTX-BD10-2 (BD10-2), a small molecule TrkB/C receptor partial agonist, was orally administered to aged London/Swedish-APP mutant mice (APPL/S) and wild-type controls. Effects on memory and hippocampal long-term potentiation (LTP) were assessed using electrophysiology, behavioral studies, immunoblotting, immunofluorescence staining, and RNA sequencing. RESULTS: In APPL/S mice, BD10-2 treatment improved memory and LTP deficits. This was accompanied by normalized phosphorylation of protein kinase B (Akt), calcium-calmodulin-dependent kinase II (CaMKII), and AMPA-type glutamate receptors containing the subunit GluA1; enhanced activity-dependent recruitment of synaptic proteins; and increased excitatory synapse number. BD10-2 also had potentially favorable effects on LTP-dependent complement pathway and synaptic gene transcription. DISCUSSION: BD10-2 prevented APPL/S/Aß-associated memory and LTP deficits, reduced abnormalities in synapse-related signaling and activity-dependent transcription of synaptic genes, and bolstered transcriptional changes associated with microglial immune response. HIGHLIGHTS: Small molecule modulation of tropomyosin related kinase B (TrkB) and C (TrkC) restores long-term potentiation (LTP) and behavior in an Alzheimer's disease (AD) model. Modulation of TrkB and TrkC regulates synaptic activity-dependent transcription. TrkB and TrkC receptors are candidate targets for translational therapeutics. Electrophysiology combined with transcriptomics elucidates synaptic restoration. LTP identifies neuron and microglia AD-relevant human-mouse co-expression modules.

A TrkB and TrkC partial agonist restores deficits in synaptic function and promotes activity-dependent synaptic and microglial transcriptomic changes in a late-stage Alzheimer's mouse model.

Introduction: TrkB and TrkC receptor signaling promotes synaptic plasticity and interacts with pathways affected by amyloid-ß (Aß)-toxicity. Upregulating TrkB/C signaling could reduce Alzheimer's disease (AD)-related degenerative signaling, memory loss, and synaptic dysfunction. Methods: PTX-BD10-2 (BD10-2), a small molecule TrkB/C receptor partial agonist, was orally administered to aged London/Swedish-APP mutant mice (APP L/S ) and wild-type controls (WT). Effects on memory and hippocampal long-term potentiation (LTP) were assessed using electrophysiology, behavioral studies, immunoblotting, immunofluorescence staining, and RNA-sequencing. Results: Memory and LTP deficits in APP L/S mice were attenuated by treatment with BD10-2. BD10-2 prevented aberrant AKT, CaMKII, and GLUA1 phosphorylation, and enhanced activity-dependent recruitment of synaptic proteins. BD10-2 also had potentially favorable effects on LTP-dependent complement pathway and synaptic gene transcription. Conclusions: BD10-2 prevented APP L/S /Aß-associated memory and LTP deficits, reduced abnormalities in synapse-related signaling and activity-dependent transcription of synaptic genes, and bolstered transcriptional changes associated with microglial immune response.

Myeloid deficiency of the intrinsic clock protein BMAL1 accelerates cognitive aging by disrupting microglial synaptic pruning.

Aging is associated with loss of circadian immune responses and circadian gene transcription in peripheral macrophages. Microglia, the resident macrophages of the brain, also show diurnal rhythmicity in regulating local immune responses and synaptic remodeling. To investigate the interaction between aging and microglial circadian rhythmicity, we examined mice deficient in the core clock transcription factor, BMAL1. Aging Cd11bcre;Bmallox/lox mice demonstrated accelerated cognitive decline in association with suppressed hippocampal long-term potentiation and increases in immature dendritic spines. C1q deposition at synapses and synaptic engulfment were significantly decreased in aging Bmal1-deficient microglia, suggesting that BMAL1 plays a role in regulating synaptic pruning in aging. In addition to accelerated age-associated hippocampal deficits, Cd11bcre;Bmallox/lox mice also showed deficits in the sleep-wake cycle with increased wakefulness across light and dark phases. These results highlight an essential role of microglial BMAL1 in maintenance of synapse homeostasis in the aging brain.

Restoring metabolism of myeloid cells reverses cognitive decline in ageing.

Ageing is characterized by the development of persistent pro-inflammatory responses that contribute to atherosclerosis, metabolic syndrome, cancer and frailty1-3. The ageing brain is also vulnerable to inflammation, as demonstrated by the high prevalence of age-associated cognitive decline and Alzheimer's disease4-6. Systemically, circulating pro-inflammatory factors can promote cognitive decline7,8, and in the brain, microglia lose the ability to clear misfolded proteins that are associated with neurodegeneration9,10. However, the underlying mechanisms that initiate and sustain maladaptive inflammation with ageing are not well defined. Here we show that in ageing mice myeloid cell bioenergetics are suppressed in response to increased signalling by the lipid messenger prostaglandin E2 (PGE2), a major modulator of inflammation11. In ageing macrophages and microglia, PGE2 signalling through its EP2 receptor promotes the sequestration of glucose into glycogen, reducing glucose flux and mitochondrial respiration. This energy-deficient state, which drives maladaptive pro-inflammatory responses, is further augmented by a dependence of aged myeloid cells on glucose as a principal fuel source. In aged mice, inhibition of myeloid EP2 signalling rejuvenates cellular bioenergetics, systemic and brain inflammatory states, hippocampal synaptic plasticity and spatial memory. Moreover, blockade of peripheral myeloid EP2 signalling is sufficient to restore cognition in aged mice. Our study suggests that cognitive ageing is not a static or irrevocable condition but can be reversed by reprogramming myeloid glucose metabolism to restore youthful immune functions.

The two faces of synaptic failure in AppNL-G-F knock-in mice.

BACKGROUND: Intensive basic and preclinical research into Alzheimer's disease (AD) has yielded important new findings, but they could not yet been translated into effective therapies. One of the reasons is the lack of animal models that sufficiently reproduce the complexity of human AD and the response of human brain circuits to novel treatment approaches. As a step in overcoming these limitations, new App knock-in models have been developed that avoid transgenic APP overexpression and its associated side effects. These mice are proposed to serve as valuable models to examine Aß-related pathology in "preclinical AD." METHODS: Since AD as the most common form of dementia progresses into synaptic failure as a major cause of cognitive deficits, the detailed characterization of synaptic dysfunction in these new models is essential. Here, we addressed this by extracellular and whole-cell patch-clamp recordings in AppNL-G-F mice compared to AppNL animals which served as controls. RESULTS: We found a beginning synaptic impairment (LTP deficit) at 3-4 months in the prefrontal cortex of AppNL-G-F mice that is further aggravated and extended to the hippocampus at 6-8 months. Measurements of miniature EPSCs and IPSCs point to a marked increase in excitatory and inhibitory presynaptic activity, the latter accompanied by a moderate increase in postsynaptic inhibitory function. CONCLUSIONS: Our data reveal a marked impairment of primarily postsynaptic processes at the level of synaptic plasticity but the dominance of a presumably compensatory presynaptic upregulation at the level of elementary miniature synaptic function.

A Fortified Food Can Be Replaced by Micronutrient Supplements for Distribution in a Mexican Social Protection Program Based on Results of a Cluster-Randomized Trial and Costing Analysis.

BACKGROUND: Despite positive nutrition impacts, the prevalence of malnutrition among beneficiaries of Mexico's conditional cash transfer (CCT) program remains high. Greater nutrition impact may have been constrained by the type of nutritional supplements provided. OBJECTIVE: The objective of this study was to inform a potential modification to the supplements distributed to pregnant and lactating women and children. METHODS: Impact was assessed using 2 cluster-randomized trials (pregnant women, children) run simultaneously. Communities (n = 54) were randomly assigned to the fortified foods provided by the program (Nutrivida women, Nutrisano children) or alternatives: tablets (women), syrup (children), or micronutrient powders for women (MNP-W) and children (MNP-C). Each supplement for women/children contained the same micronutrients based on the formulations of Nutrivida and Nutrisano, respectively. Pregnant women (aged >18 y) were recruited before 25 weeks of gestation and followed to 3 mo postpartum. Children aged 6-12 mo were recruited and followed to age 24 mo. Primary outcomes were anemia for women and length growth for children. Statistical analyses appropriate for cluster-randomized designs were used, and structural equation modeling to estimate dose-response effects. Supplement costs per beneficiary (daily dose for 18 mo) were estimated for production and distribution. RESULTS: There was no significant difference in change of anemia prevalence between supplement groups in women, or in length growth between groups in children. One daily dose of any supplement was associated with 0.8 cm greater length growth. From baseline to age 24 mo, the prevalence of anemia in the Nutrisano, syrup, and MNP-C groups decreased by 36.7, 40.8, and 37.9 percentage points, respectively (within-group, P < 0.05; between groups, P > 0.05). Costs per beneficiary ranged from $12.1 (MNP-C) to $94.8 (Nutrivida). CONCLUSIONS: The CCT program could distribute alternative supplements at lower cost per beneficiary without compromising potential for impact. Acceptance among beneficiaries should also be considered in choice of alternatives. This trial was registered at www.clinicaltrials.gov as NCT00531674.

An Iterative Process for Training Design and Implementation Increased Health Workers' Knowledge for Taking Nutrition Behavior Change to Scale.

BACKGROUND: The shortage of skilled, motivated, and well-supported health workers is a major barrier to scaling up nutrition interventions and services. OBJECTIVE: The objective of this study is to describe the process for developing and implementing a training of health personnel for the delivery of the Integrated Strategy for Attention to Nutrition (EsIAN), an evidence-based strategy for promoting infant and young child feeding through primary health care in Mexico. The specific objective is to provide a case study and highlight challenges, as well as elements to successfully mitigate these, and discuss potential applications of findings beyond the Mexican context. METHODS: The design and implementation of training followed a 5-phase process: situation analysis, formative research, large-scale feasibility study, redesign and scale up, and evaluation. We conducted document reviews, surveys, and focus groups during the first phases to inform and refine the training, as well as a pre- and posttraining telephone survey to evaluate change in knowledge. RESULTS: The initial phases of the design provided a clear understanding of the opportunities and challenges for promoting infant and young child feeding, as well as health workers' routines and practices, which informed training design. The feasibility study allowed tailoring and refinement of training. The vertical coherence and coordination between the federal and state levels during redesign and scale up facilitated compliance with training timeline and process. Evaluation results showed significant improvement in knowledge posttraining of up to 19 percentage points. CONCLUSIONS: The EsIAN training component for health providers was developed using a systematic approach to consolidate and generate relevant evidence, following an iterative process to test, learn, and improve both design and implementation. This process allowed for flexibility to take advantage of new opportunities and respond to findings from iterations. Garnering and ensuring political support allowed for continuity and sustainability of actions.

Employment Condition Modifies the Using Patterns of Screening Mammography in Workers Insured by the Mexican Government: A Case-Control Study.

BACKGROUND: Our main aim was to investigate whether the employment condition modifies the use patterns of the screening mammography in workers insured by the Mexican government (Instituto de Seguridad y Servicios Sociales de los Trabajadores del Estado, ISSSTE; medical facilities of the Mexican government). METHODS: A case-control study age-matched was done in women insured by the Mexican government, aged 40-69 years, attending a general hospital (ISSSTE). All subjects were submitted to an interview and anthropometric data registry. In the interview were obtained: demographic data, of schooling, breast cancer family history, and reproductive history; besides, mammography history during the past 2 years and place of performance (in or outside of the ISSSTE). Finally, it was evaluated whether the mammography use in the ISSSTE was related to their employment condition: Active workers (cases) vs. dependents or retired workers (controls). RESULTS: The sample was of 252 women: 126 cases and 126 controls. Cases obtained less mammograms in the ISSSTE (P = 0.03, odds ratio = 0.54, 95% confidence interval, CI 0.30-0.96), than their dependents or the retired workers. Furthermore, cases with high education (university or higher) also obtained fewer mammograms in the ISSSTE (P = 0.03, odds ratio = 0.26, 95% CI 0.05-0.93). CONCLUSIONS: Women active workers with higher education are obtaining less screening mammograms in the ISSSTE than their dependents or the retired workers.

Subtle behavioral changes and increased prefrontal-hippocampal network synchronicity in APPNL-G-F mice before prominent plaque deposition.

Amyloid-ß (Aß) peptides occur in the brains of patients with Alzheimer's disease (AD), but their role in functional impairment is still debated. High levels of APP and APP fragments in mice that overexpress APP might confound their use in preclinical research. We examined the occurrence of behavioral, cognitive and neuroimaging changes in APPNL-G-F knock-in mice that display Aß42 amyloidosis in the absence of APP overexpression. Female APPNL-G-F mice (carrying Swedish, Iberian and Arctic APP mutations) were compared to APPNL mice (APP Swedish) at 3, 7 and 10 months. Mice were subjected to a test battery that referred to clinical AD symptoms, comprising cage activity, open field, elevated plus maze, social preference and novelty test, and spatial learning, reversal learning and spatial reference memory performance. Our assessment confirmed that behavior at these early ages was largely unaffected in these mice in accordance with previous reports, with some subtle behavioral changes, mainly in social and anxiety-related test performance. Resting-state functional MRI (rsfMRI) assessed connectivity between hippocampal and prefrontal regions with an established role in flexibility, learning and memory. Increased prefrontal-hippocampal network synchronicity was found in 3-month-old APPNL-G-F mice. These functional changes occurred before prominent amyloid plaque deposition.

Spatial reversal learning defect coincides with hypersynchronous telencephalic BOLD functional connectivity in APPNL-F/NL-F knock-in mice.

Amyloid pathology occurs early in Alzheimer's disease (AD), and has therefore been the focus of numerous studies. Transgenic mouse models have been instrumental to study amyloidosis, but observations might have been confounded by APP-overexpression artifacts. The current study investigated early functional defects in an APP knock-in mouse model, which allows assessing the effects of pathological amyloid-beta (Aß) without interference of APP-artifacts. Female APPNL/NL knock-in mice of 3 and 7 months old were compared to age-matched APPNL-F/NL-F mice with increased Aß42/40 ratio and initial Aß-plaque deposition around 6 months of age. Spatial learning was examined using a Morris water maze protocol consisting of acquisition and reversal trials interleaved with reference memory tests. Functional connectivity (FC) of brain networks was assessed using resting-state functional MRI (rsfMRI). The Morris water maze data revealed that 3 months old APPNL-F/NL-F mice were unable to reach the same reference memory proficiency as APPNL/NL mice after reversal training. This cognitive defect in 3-month-old APPNL-F/NL-F mice coincided with hypersynchronous FC of the hippocampal, cingulate, caudate-putamen, and default-mode-like networks. The occurrence of these defects in APPNL-F/NL-F mice demonstrates that cognitive flexibility and synchronicity of telencephalic activity are specifically altered by early Aß pathology without changes in APP neurochemistry.

Quinolinic acid injection in mouse medial prefrontal cortex affects reversal learning abilities, cortical connectivity and hippocampal synaptic plasticity.

Intracerebral injection of the excitotoxic, endogenous tryptophan metabolite, quinolinic acid (QA), constitutes a chemical model of neurodegenerative brain disease. Complementary techniques were combined to examine the consequences of QA injection into medial prefrontal cortex (mPFC) of C57BL6 mice. In accordance with the NMDAR-mediated synapto- and neurotoxic action of QA, we found an initial increase in excitability and an augmentation of hippocampal long-term potentiation, converting within two weeks into a reduction and impairment, respectively, of these processes. QA-induced mPFC excitotoxicity impaired behavioral flexibility in a reversal variant of the hidden-platform Morris water maze (MWM), whereas regular, extended MWM training was unaffected. QA-induced mPFC damage specifically affected the spatial-cognitive strategies that mice use to locate the platform during reversal learning. These behavioral and cognitive defects coincided with changes in cortical functional connectivity (FC) and hippocampal neuroplasticity. FC between various cortical regions was assessed by resting-state fMRI (rsfMRI) methodology, and mice that had received QA injection into mPFC showed increased FC between various cortical regions. mPFC and hippocampus (HC) are anatomically as well as functionally linked as part of a cortical network that controls higher-order cognitive functions. Together, these observations demonstrate the central functional importance of rodent mPFC as well as the validity of QA-induced mPFC damage as a preclinical rodent model of the early stages of neurodegeneration.

Separate Ionotropic and Metabotropic Glutamate Receptor Functions in Depotentiation vs. LTP: A Distinct Role for Group1 mGluR Subtypes and NMDARs.

Depotentiation (DP) is a mechanism by which synapses that have recently undergone long-term potentiation (LTP) can reverse their synaptic strengthening within a short time-window after LTP induction. Group 1 metabotropic glutamate receptors (mGluRs) were shown to be involved in different forms of LTP and long-term depression (LTD), but little is known about their roles in DP. Here, we generated DP by applying low-frequency stimulation (LFS) at 5 Hz after LTP had been induced by a single train of theta-burst-stimulation (TBS). While application of LFS for 2 min (DP2') generated only a short-lasting DP that was independent of the activation of N-methyl-D-aspartate receptors (NMDARs) and group 1 mGluRs, LFS given for 8 min (DP8') induced a robust DP that was maintained for at least 2 h. This strong form of DP was contingent on NMDAR activation. Interestingly, DP8' appears to include a metabotropic NMDAR function because it was blocked by the competitive NMDAR antagonist D-AP5 but not by the use-dependent inhibitor MK-801 or high Mg2+. Furthermore, DP8' was enhanced by application of the mGluR1 antagonist (YM 298198, 1 µM). The mGluR5 antagonist 2-Methyl-6(phenylethynyl) pyridine (MPEP, 40 µM), in contrast, failed to affect it. The induction of LTP, in turn, was NMDAR dependent (as tested with D-AP5), and blocked by MPEP but not by YM 298198. These results indicate a functional dissociation of mGluR1 and mGluR5 in two related and consecutively induced types of NMDAR-dependent synaptic plasticity (LTP → DP) with far-reaching consequences for their role in plasticity and learning under normal and pathological conditions.

Early pathologic amyloid induces hypersynchrony of BOLD resting-state networks in transgenic mice and provides an early therapeutic window before amyloid plaque deposition.

INTRODUCTION: In Alzheimer's disease (AD), pathologic amyloid-beta (Aß) is synaptotoxic and impairs neuronal function at the microscale, influencing brain networks at the macroscale before Aß deposition. The latter can be detected noninvasively, in vivo, using resting-state functional MRI (rsfMRI), a technique used to assess brain functional connectivity (FC). METHODS: RsfMRI was performed longitudinally in TG2576 and PDAPP mice, starting before Aß deposition to determine the earliest FC changes. Additionally, the role of pathologic Aß on early FC alterations was investigated by treating TG2576 mice with the 3D6 anti-Aß-antibody. RESULTS: Both transgenic models showed hypersynchronized FC before Aß deposition and hyposynchronized FC at later stages. Early anti-Aß treatment in TG2576 mice prevented hypersynchronous FC and the associated synaptic impairments and excitatory/inhibitory disbalances. DISCUSSION: Hypersynchrony of FC may be used as a new noninvasive read out of early AD and can be recovered by anti-Aß treatment, encouraging preventive treatment strategies in familial AD.