Brain energy failure in dementia syndromes: Opportunities and challenges for glucagon-like peptide-1 receptor agonists.

Medications for type 2 diabetes (T2DM) offer a promising path for discovery and development of effective interventions for dementia syndromes. A common feature of dementia syndromes is an energy failure due to reduced energy supply to neurons and is associated with synaptic loss and results in cognitive decline and behavioral changes. Among diabetes medications, glucagon-like peptide-1 (GLP-1) receptor agonists (RAs) promote protective effects on vascular, microglial, and neuronal functions. In this review, we present evidence from animal models, imaging studies, and clinical trials that support developing GLP-1 RAs for dementia syndromes. The review examines how changes in brain energy metabolism differ in conditions of insulin resistance and T2DM from dementia and underscores the challenges that arise from the heterogeneity of dementia syndromes. The development of GLP-1 RAs as dementia therapies requires a deeper understanding of the regional changes in brain energy homeostasis guided by novel imaging biomarkers.

Mutations in the BLOC-1 subunits dysbindin and muted generate divergent and dosage-dependent phenotypes.

Post-mortem analysis has revealed reduced levels of the protein dysbindin in the brains of those suffering from the neurodevelopmental disorder schizophrenia. Consequently, mechanisms controlling the cellular levels of dysbindin and its interacting partners may participate in neurodevelopmental processes impaired in that disorder. To address this question, we studied loss of function mutations in the genes encoding dysbindin and its interacting BLOC-1 subunits. We focused on BLOC-1 mutants affecting synapse composition and function in addition to their established systemic pigmentation, hematological, and lung phenotypes. We tested phenotypic homogeneity and gene dosage effects in the mouse null alleles muted (Bloc1s5(mu/mu)) and dysbindin (Bloc1s8(sdy/sdy)). Transcripts of NMDA receptor subunits and GABAergic interneuron markers, as well as expression of BLOC-1 subunit gene products, were affected differently in the brains of Bloc1s5(mu/mu) and Bloc1s8(sdy/sdy) mice. Unlike Bloc1s8(sdy/sdy), elimination of one or two copies of Bloc1s5 generated indistinguishable pallidin transcript phenotypes. We conclude that monogenic mutations abrogating the expression of a protein complex subunit differentially affect the expression of other complex transcripts and polypeptides as well as their downstream effectors. We propose that the genetic disruption of different subunits of protein complexes and combinations thereof diversifies phenotypic presentation of pathway deficiencies, contributing to the wide phenotypic spectrum and complexity of neurodevelopmental disorders.

Dysbindin-1 loss compromises NMDAR-dependent synaptic plasticity and contextual fear conditioning.

Genetic variants in DTNBP1 encoding the protein dysbindin-1 have often been associated with schizophrenia and with the cognitive deficits prominent in that disorder. Because impaired function of the hippocampus is thought to play a role in these memory deficits and because NMDAR-dependent synaptic plasticity in this region is a proposed biological substrate for some hippocampal-dependent memory functions in schizophrenia, we hypothesized that reduced dysbindin-1 expression would lead to impairments in NMDAR-dependent synaptic plasticity and in contextual fear conditioning. Acute slices from male mice carrying 0, 1, or 2 null mutant alleles of the Dtnbp1 gene were prepared, and field recordings from the CA1 striatum radiatum were obtained before and after tetanization of Schaffer collaterals of CA3 pyramidal cells. Mice homozygous for the null mutation in Dtnbp1 exhibited significantly reduced NMDAR-dependent synaptic potentiation compared to wild type mice, an effect that could be rescued by bath application of the NMDA receptor coagonist glycine (10 µM). Behavioral testing in adult mice revealed deficits in hippocampal memory processes. Homozygous null mice exhibited lower conditional freezing, without a change in the response to shock itself, indicative of a learning and memory deficit. Taken together, these results indicate that a loss of dysbindin-1 impairs hippocampal plasticity which may, in part, explain the role dysbindin-1 plays in the cognitive impairments of schizophrenia.

Mechanical ventilation triggers hippocampal apoptosis by vagal and dopaminergic pathways.

RATIONALE: Critically ill patients frequently develop neuropsychological disturbances including acute delirium or memory impairment. The need for mechanical ventilation is a risk factor for these adverse events, but a mechanism that links lung stretch and brain injury has not been identified. OBJECTIVES: To identify the mechanisms that lead to brain dysfunction during mechanical ventilation. METHODS: Brains from mechanically ventilated mice were harvested, and signals of apoptosis and alterations in the Akt survival pathway were studied. These measurements were repeated in vagotomized or haloperidol-treated mice, and in animals intracerebroventricularly injected with selective dopamine-receptor blockers. Hippocampal slices were cultured and treated with micromolar concentrations of dopamine, with or without dopamine receptor blockers. Last, levels of dysbindin, a regulator of the membrane availability of dopamine receptors, were assessed in the experimental model and in brain samples from ventilated patients. MEASUREMENTS AND MAIN RESULTS: Mechanical ventilation triggers hippocampal apoptosis as a result of type 2 dopamine receptor activation in response to vagal signaling. Activation of these receptors blocks the Akt/GSK3ß prosurvival pathway and activates the apoptotic cascade, as demonstrated in vivo and in vitro. Vagotomy, systemic haloperidol, or intracerebroventricular raclopride (a type 2 dopamine receptor blocker) ameliorated this effect. Moreover, ventilation induced a concomitant change in the expression of dysbindin-1C. These results were confirmed in brain samples from ventilated patients. CONCLUSIONS: These results prove the existence of a pathogenic mechanism of lung stretch-induced hippocampal apoptosis that could explain the neurological changes in ventilated patients and may help to identify novel therapeutic approaches.

Dysbindin-1 mutant mice implicate reduced fast-phasic inhibition as a final common disease mechanism in schizophrenia.

DTNBP1 (dystrobrevin binding protein 1) is a leading candidate susceptibility gene in schizophrenia and is associated with working memory capacity in normal subjects. In schizophrenia, the encoded protein dystrobrevin-binding protein 1 (dysbindin-1) is often reduced in excitatory cortical limbic synapses. We found that reduced dysbindin-1 in mice yielded deficits in auditory-evoked response adaptation, prepulse inhibition of startle, and evoked γ-activity, similar to patterns in schizophrenia. In contrast to the role of dysbindin-1 in glutamatergic transmission, γ-band abnormalities in schizophrenia are most often attributed to disrupted inhibition and reductions in parvalbumin-positive interneuron (PV cell) activity. To determine the mechanism underlying electrophysiological deficits related to reduced dysbindin-1 and the potential role of PV cells, we examined PV cell immunoreactivity and measured changes in net circuit activity using voltage-sensitive dye imaging. The dominant circuit impact of reduced dysbindin-1 was impaired inhibition, and PV cell immunoreactivity was reduced. Thus, this model provides a link between a validated candidate gene and an auditory endophenotypes. Furthermore, these data implicate reduced fast-phasic inhibition as a common underlying mechanism of schizophrenia-associated intermediate phenotypes.

The nature, significance, and glucagon-like peptide-1 analog treatment of brain insulin resistance in Alzheimer's disease.

Alzheimer's disease (AD) is an age-related neurodegenerative disease leading over the course of decades to the most common form of dementia. Many of its pathologic features and cognitive deficits may be due in part to brain insulin resistance recently demonstrated in the insulin receptor→insulin receptor substrate-1 (IRS-1) signaling pathway. The proximal cause of such resistance in AD dementia and amnestic mild cognitive impairment (aMCI) appears to be serine inhibition of IRS-1, a phenomenon likely due to microglial release of inflammatory cytokines triggered by oligomeric Aß. Studies on animal models of AD and on human brain tissue from MCI cases at high risk of AD dementia have shown that brain insulin resistance and many other pathologic features and symptoms of AD may be greatly reduced or even reversed by treatment with FDA-approved glucagon-like peptide-1 (GLP-1) analogs such as liraglutide (Victoza). These findings call attention to the need for further basic, translational, and clinical studies on GLP-1 analogs as promising AD therapeutics.

Altered neuregulin 1-erbB4 signaling contributes to NMDA receptor hypofunction in schizophrenia.

Recent molecular genetics studies implicate neuregulin 1 (NRG1) and its receptor erbB in the pathophysiology of schizophrenia. Among NRG1 receptors, erbB4 is of particular interest because of its crucial roles in neurodevelopment and in the modulation of N-methyl-D-aspartate (NMDA) receptor signaling. Here, using a new postmortem tissue-stimulation approach, we show a marked increase in NRG1-induced activation of erbB4 in the prefrontal cortex in schizophrenia. Levels of NRG1 and erbB4, however, did not differ between schizophrenia and control groups. To evaluate possible causes for this hyperactivation of erbB4 signaling, we examined the association of erbB4 with PSD-95 (postsynaptic density protein of 95 kDa), as this association has been shown to facilitate activation of erbB4. Schizophrenia subjects showed substantial increases in erbB4-PSD-95 interactions. We found that NRG1 stimulation suppresses NMDA receptor activation in the human prefrontal cortex, as previously reported in the rodent cortex. NRG1-induced suppression of NMDA receptor activation was more pronounced in schizophrenia subjects than in controls, consistent with enhanced NRG1-erbB4 signaling seen in this illness. Therefore, these findings suggest that enhanced NRG1 signaling may contribute to NMDA hypofunction in schizophrenia.

Brain uptake pharmacokinetics of albiglutide, dulaglutide, tirzepatide, and DA5-CH in the search for new treatments of Alzheimer's and Parkinson's diseases.

BACKGROUND: A number of peptide incretin receptor agonists (IRAs) show promise as therapeutics for Alzheimer's disease (AD) and Parkinson's disease (PD). Transport across the blood-brain barrier (BBB) is one way for IRAs to act directly within the brain. To determine which IRAs are high priority candidates for treating these disorders, we have studied their brain uptake pharmacokinetics. METHODS: We quantitatively measure the ability of four IRAs to cross the BBB. We injected adult male CD-1 mice intravenously with 125I- or 14C-labeled albiglutide, dulaglutide, DA5-CH, or tirzepatide and used multiple-time regression analyses to measure brain kinetics up to 1 hour. For those IRAs failing to enter the brain 1 h after intravenous injection, we also investigated their ability to enter over a longer time frame (i.e., 6 h). RESULTS: Albiglutide and dulaglutide had the fastest brain uptake rates within 1 hour. DA5-CH appears to enter the brain rapidly, reaching equilibrium quickly. Tirzepatide does not appear to cross the BBB within 1 h after iv injection but like albumin, did so slowly over 6 h, presumably via the extracellular pathways. CONCLUSIONS: We find that IRAs can cross the BBB by two separate processes; one that is fast and one that is slow. Three of the four IRAs investigated here have fast rates of transport and should be taken into consideration for testing as AD and PD therapeutics as they would have the ability to act quickly and directly on the brain as a whole.

Akt1 deficiency in schizophrenia and impairment of hippocampal plasticity and function.

Genetic studies have associated deficient function of the serine/threonine kinase Akt1 with schizophrenia. This disorder is associated with developmental, structural, and functional abnormalities of the hippocampus that could be traced to abnormal Akt1 function. To establish a closer connection between Akt1 and hippocampal function, mice with a selective deletion of Akt1 (Akt1(-/-) mice) were examined for physiological and behavioral outcomes dependent on the hippocampus and associated with schizophrenia. Genetic deletion of Akt1 was associated with both impaired proliferative capacity of adult-born hippocampal progenitors and hippocampal long-term potentiation, indicating deficient functions of this brain region associated with neuroplasticity. Moreover, Akt1(-/-) mice demonstrated impairments in contextual fear conditioning and recall of spatial learning, behaviors known to selectively involve the hippocampus. Akt1(-/-) mice also showed reduced prepulse inhibition of the acoustic startle response, a sensorimotor gating response that is perturbed in schizophrenia. Postmortem tissue samples from patients with schizophrenia showed significant reductions of phosphorylated Akt levels in hilar neurons of the dentate gyrus, the neurogenic zone of the hippocampus. Taken together, these results implicate the Akt1 isoform in regulating hippocampal neuroplasticity and cognition and in contributing to the etiology of schizophrenia.

Dysbindin-1 in dorsolateral prefrontal cortex of schizophrenia cases is reduced in an isoform-specific manner unrelated to dysbindin-1 mRNA expression.

DTNBP1 (dystrobrevin binding protein 1) remains a top candidate gene in schizophrenia. Reduced expression of this gene and of its encoded protein, dysbindin-1, have been reported in the brains of schizophrenia cases. It has not been established, however, if the protein reductions encompass all dysbindin-1 isoforms or if they are associated with decreased DTNBP1 gene expression. Using a matched pairs design in which each of 28 Caucasian schizophrenia cases was matched in age and sex to a normal Caucasian control, Western blotting of whole-tissue lysates of dorsolateral prefrontal cortex (DLPFC) revealed significant reductions in dysbindin-1C (but not in dysbindin-1A or -1B) in schizophrenia (P = 0.022). These reductions occurred without any significant change in levels of the encoding transcript in the same tissue samples and in the absence of the only DTNBP1 risk haplotype for schizophrenia reported in the USA. Indeed, no significant correlations were found between case-control differences in any dysbindin-1 isoform and the case-control differences in its encoding mRNA. Consequently, the mean 60% decrease in dysbindin-1C observed in 71% of our case-control pairs appears to reflect abnormalities in mRNA translation and/or processes promoting dysbindin-1C degradation (e.g. oxidative stress, phosphorylation and/or ubiquitination). Given the predominantly post-synaptic localization of dysbindin-1C and known post-synaptic effects of dysbindin-1 reductions in the rodent equivalent of the DLPFC, the present findings suggest that decreased dysbindin-1C in the DLPFC may contribute to the cognitive deficits of schizophrenia by promoting NMDA receptor hypofunction in fast-spiking interneurons.

EHD1 is a synaptic protein that modulates exocytosis through binding to snapin.

EHD1 is an EH (Eps15 homology) domain-containing protein involved in endosomal recycling. Our yeast two hybrid screening experiments showed that EHD1 interacts with a synaptic protein, snapin, and the present study was carried out to further elucidate the functional significance of this interaction. Immunoreactivity to EHD1 is observed in the cerebral cortex, hippocampus and striatum, in the rat brain. The protein is colocalized with the axon terminal marker synaptophysin in cultured neurons. EHD1 binds to the C terminus of snapin via its C terminus EH domain. It negatively affects the binding of a SNARE complex protein, SNAP-25, to snapin, probably due to the competition for overlapping binding sites on the C terminus of snapin. EHD1 affects the coupling of synaptotagmin-1 to the SNARE complex, and could be a negative regulator of exocytosis. This is supported by electrophysiological findings that PC-12 cells which overexpress EHD1 show reduced depolarization-induced exocytosis compared to controls, but the reduced exocytosis is not observed in cells which overexpress the N terminus of EHD1 that is unable to bind snapin. Together, the above results indicate that EHD1 is a synaptic protein that negatively affects exocytosis through binding to snapin.

Brain uptake pharmacokinetics of incretin receptor agonists showing promise as Alzheimer's and Parkinson's disease therapeutics.

Among the more promising treatments proposed for Alzheimer's disease (AD) and Parkinson's disease (PD) are those reducing brain insulin resistance. The antidiabetics in the class of incretin receptor agonists (IRAs) reduce symptoms and brain pathology in animal models of AD and PD, as well as glucose utilization in AD cases and clinical symptoms in PD cases after their systemic administration. At least 9 different IRAs are showing promise as AD and PD therapeutics, but we still lack quantitative data on their relative ability to cross the blood-brain barrier (BBB) reaching the brain parenchyma. We consequently compared brain uptake pharmacokinetics of intravenous 125I-labeled IRAs in adult CD-1 mice over the course of 60 min. We tested single IRAs (exendin-4, liraglutide, lixisenatide, and semaglutide), which bind receptors for one incretin (glucagon-like peptide-1 [GLP-1]), and dual IRAs, which bind receptors for two incretins (GLP-1 and glucose-dependent insulinotropic polypeptide [GIP]), including unbranched, acylated, PEGylated, or C-terminally modified forms (Finan/Ma Peptides 17, 18, and 20 and Hölscher peptides DA3-CH and DA-JC4). The non-acylated and non-PEGylated IRAs (exendin-4, lixisenatide, Peptide 17, DA3-CH and DA-JC4) had significant rates of blood-to-brain influx (Ki), but the acylated IRAs (liraglutide, semaglutide, and Peptide 18) did not measurably cross the BBB. The brain influx of the non-acylated, non-PEGylated IRAs were not saturable up to 1 µg of these drugs and was most likely mediated by adsorptive transcytosis across brain endothelial cells, as observed for exendin-4. Of the non-acylated, non-PEGylated IRAs tested, exendin-4 and DA-JC4 were best able to cross the BBB based on their rate of brain influx, percentage reaching the brain that accumulated in brain parenchyma, and percentage of the systemic dose taken up per gram of brain tissue. Exendin-4 and DA-JC4 thus merit special attention as IRAs well-suited to enter the central nervous system (CNS), thus reaching areas pathologic in AD and PD.

Caspase-3 is enriched in postsynaptic densities and increased in Alzheimer's disease.

Progressive synaptic degeneration and neuron loss are major structural correlates of cognitive impairment in Alzheimer's disease (AD). The mechanisms by which synaptic degeneration in AD occurs have not been established. The activation of proteins within the caspase family has been implicated in AD-associated neurodegeneration, and synaptically localized caspase activity could play a role in the synaptic degeneration and loss found in AD. We used synaptosomal fractionation with Western blotting and immunohistochemistry to examine the anatomical, subcellular, and subsynaptic expression patterns of caspase 3 in both the anterior cingulate cortex and hippocampus of control and AD patients. In both control and AD cases, there was a selective enrichment of caspase- 3 at synapses, particularly in the postsynaptic density (PSD) fractions. Compared with controls, AD patients exhibited significant increases in synaptic procaspase- 3 and active caspase-3 expression levels that were most evident in the PSD fractions. These data demonstrate for the first time the preferential localization and increase of caspase-3 in the PSD fractions in AD and suggest an important role for caspase 3 in synapse degeneration during disease progression.

Low sociability is associated with reduced size of the corpus callosum in the BALB/cJ inbred mouse strain.

The behavioral manifestations of autism, including reduced sociability (reduced tendency to seek social interaction), may be related to underdevelopment of the corpus callosum (CC). The BALB/cJ inbred mouse strain is a useful model system for testing the relationship between reduced sociability and CC underdevelopment. BALB/cJ mice show low levels of sociability, on average, but substantial intrastrain variability in sociability, as well as striking variability in CC development. This study tested the hypothesis that sociability is positively correlated with CC size within the BALB/cJ inbred strain. 30-day-old BALB/cJ and C57BL/6J mice were tested for sociability towards gonadectomized A/J stimulus mice in a social choice task. The size of the corpus callosum was measured histologically at the midsagittal plane. BALB/cJ mice showed a significant positive correlation between the tendency to sniff the stimulus mouse and size of the CC relative to brain weight. C57BL/6J mice showed consistently high levels of sociability and normal corpus callosum development. These results suggest that abnormal white matter structure is associated with deficits in sociability in BALB/cJ mice. Additional studies are warranted to elucidate the relationship between brain connectivity and sociability in this model system.

Insulin resistance and cognitive test performance in elderly adults: National health and nutrition examination survey (NHANES).

OBJECTIVES: To examine the relationship between homeostatic model of insulin resistance (HOMA-IR) and cognitive test performance among population≥60years in a national database. HYPOTHESIS: Higher insulin resistance is associated with lower cognitive test performance score in the population≥60years. PARTICIPANTS: We analyzed data from the National Health and Nutrition Examination Survey (NHANES) 1999-2000 and 2001-2002. MEASUREMENTS: Cognitive test performance was measured by the Digit Symbol Substitution (DSS) exercise score. The main independent variable was the homeostasis model assessment of insulin resistance (HOMA-IR). We used bivariate analysis and generalized linear model adjusting for age, gender, race, education, body mass index, and systolic and diastolic blood pressures; total cholesterol, low density lipoprotein (LDL), high density lipoprotein (HDL) and triglyceride levels; and physical activity, diabetes mellitus, stroke, and congestive heart failure. STATA 14 was used to analyze the data taking into consideration the design, strata and weight. RESULTS: Of the 1028 participants, 44% were male and 85% were white. The mean age was 70.0±0.28 (SE) years. Their average HOMA-IR was 3.6±0.14 and they had a mean of 49.2±0.8 correct DSS score in the cognitive test. Adjusting for the confounding variables, HOMA-IR was associated with decline in DSS score (B=-0.30, 95% confidence interval=-0.54 and -0.05, p=0.01). The model explained 44% of the variability of the DSS score (R2=0.44). Significant predictors of decline in DSS score were age, gender, race, and education (p=0.01). CONCLUSION: Insulin resistance as measured by HOMA-IR was independently associated with lower cognitive test performance score among elderly participants aged ≥60years. Longitudinal studies are needed to test the mechanism and the causal relationship.

Dysbindin-1 is reduced in intrinsic, glutamatergic terminals of the hippocampal formation in schizophrenia.

Eleven studies now report significant associations between schizophrenia and certain haplotypes of single-nucleotide polymorphisms in the gene encoding dysbindin-1 at 6p22.3. Dysbindin-1 is best known as dystrobrevin-binding protein 1 (DTNBP1) and may thus be associated with the dystrophin glycoprotein complex found at certain postsynaptic sites in the brain. Contrary to expectations, however, we found that when compared to matched, nonpsychiatric controls, 73-93% of cases in two schizophrenia populations displayed presynaptic dysbindin-1 reductions averaging 18-42% (P = 0.027-0.0001) at hippocampal formation sites lacking neuronal dystrobrevin (i.e., beta-dystrobrevin). The reductions, which were not observed in the anterior cingulate of the same schizophrenia cases, occurred specifically in terminal fields of intrinsic, glutamatergic afferents of the subiculum, the hippocampus proper, and especially the inner molecular layer of the dentate gyrus (DGiml). An inversely correlated increase in vesicular glutamate transporter-1 (VGluT-1) occurred in DGiml of the same schizophrenia cases. Those changes occurred without evidence of axon terminal loss or neuroleptic effects on dysbindin-1 or VGluT-1. Our findings indicate that presynaptic dysbindin-1 reductions independent of the dystrophin glycoprotein complex are frequent in schizophrenia and are related to glutamatergic alterations in intrinsic hippocampal formation connections. Such changes may contribute to the cognitive deficits common in schizophrenia.

Neuronal Activity-Induced Sterol Regulatory Element Binding Protein-1 (SREBP1) is Disrupted in Dysbindin-Null Mice-Potential Link to Cognitive Impairment in Schizophrenia.

Schizophrenia is a chronic debilitating neuropsychiatric disorder that affects about 1 % of the population. Dystrobrevin-binding protein 1 (DTNBP1 or dysbindin) is one of the Research Domain Constructs (RDoC) associated with cognition and is significantly reduced in the brain of schizophrenia patients. To further understand the molecular underpinnings of pathogenesis of schizophrenia, we have performed microarray analyses of the hippocampi from dysbindin knockout mice, and found that genes involved in the lipogenic pathway are suppressed. Moreover, we discovered that maturation of a master transcriptional regulator for lipid synthesis, sterol regulatory element binding protein-1 (SREBP1) is induced by neuronal activity, and is required for induction of the immediate early gene ARC (activity-regulated cytoskeleton-associated protein), necessary for synaptic plasticity and memory. We found that nuclear SREBP1 is dramatically reduced in dysbindin-1 knockout mice and postmortem brain tissues from human patients with schizophrenia. Furthermore, activity-dependent maturation of SREBP1 as well as ARC expression were attenuated in dysbindin-1 knockout mice, and these deficits were restored by an atypical antipsychotic drug, clozapine. Together, results indicate an important role of dysbindin-1 in neuronal activity induced SREBP1 and ARC, which could be related to cognitive deficits in schizophrenia.

Novel GLP-1R/GIPR co-agonist "twincretin" is neuroprotective in cell and rodent models of mild traumatic brain injury.

Several single incretin receptor agonists that are approved for the treatment of type 2 diabetes mellitus (T2DM) have been shown to be neuroprotective in cell and animal models of neurodegeneration. Recently, a synthetic dual incretin receptor agonist, nicknamed "twincretin," was shown to improve upon the metabolic benefits of single receptor agonists in mouse and monkey models of T2DM. In the current study, the neuroprotective effects of twincretin are probed in cell and mouse models of mild traumatic brain injury (mTBI), a prevalent cause of neurodegeneration in toddlers, teenagers and the elderly. Twincretin is herein shown to have activity at two different receptors, dose-dependently increase levels of intermediates in the neurotrophic CREB pathway and enhance viability of human neuroblastoma cells exposed to toxic concentrations of glutamate and hydrogen peroxide, insults mimicking the inflammatory conditions in the brain post-mTBI. Additionally, twincretin is shown to improve upon the neurotrophic effects of single incretin receptor agonists in these same cells. Finally, a clinically translatable dose of twincretin, when administered post-mTBI, is shown to fully restore the visual and spatial memory deficits induced by mTBI, as evaluated in a mouse model of weight drop close head injury. These results establish twincretin as a novel neuroprotective agent and suggest that it may improve upon the effects of the single incretin receptor agonists via dual agonism.