The link between cognition and somatic conditions related to insulin resistance in the UK Biobank study cohort: a systematic review.

Clinical and genomic studies have shown an overlap between neuropsychiatric disorders and insulin resistance (IR)-related somatic conditions, including obesity, type 2 diabetes, and cardiovascular diseases. Impaired cognition is often observed among neuropsychiatric disorders, where multiple cognitive domains may be affected. In this review, we aimed to summarise previous evidence on the relationship between IR-related diseases/traits and cognitive performance in the large UK Biobank study cohort. Electronic searches were conducted on PubMed, Scopus, and Web of Science until April 2022. Eighteen articles met the inclusion criteria and were qualitatively reviewed. Overall, there is substantial evidence for an association between IR-related cardio-metabolic diseases/traits and worse performance on various cognitive domains, which is largely independent of possible confoundings. The most consistent findings referred to IR-related associations with poorer verbal and numerical reasoning ability, as well as slower processing speed. The observed associations might be mediated by alterations in immune-inflammation, brain integrity/connectivity, and/or comorbid somatic or psychiatric diseases/traits. Our findings provide impetus for further research into the underlying neurobiology and possible new therapeutic targets.

Temporally ordered associations between type 2 diabetes and brain disorders - a Danish register-based cohort study.

BACKGROUND: Type 2 diabetes mellitus (T2DM) is linked with several neurodegenerative and psychiatric disorders, either as a comorbid condition or as a risk factor. We aimed to expand the evidence by examining associations with a broad range of brain disorders (psychiatric and neurological disorders, excluding late-onset neurodegenerative disorders), while also accounting for the temporal order of T2DM and these brain disorders. METHODS: In a population-based cohort-study of 1,883,198 Danish citizens, born 1955-1984 and followed until end of 2016, we estimated associations between T2DM and 16 brain disorders first diagnosed between childhood and mid-adulthood. We calculated odds ratios (OR) and hazard ratios (HR) with 95% confidence intervals (CI) in temporally ordered analyses (brain disorder diagnosis after T2DM and vice versa), adjusted for sex, age, follow-up, birth year, and parental factors. RESULTS: A total of 67,660 (3.6%) of the study population were identified as T2DM cases after age 30 and by a mean age of 45 years (SD of 8 years). T2DM was associated with most psychiatric disorders. Strongest associations were seen with other (i.e. non-anorectic) eating disorders (OR [95% CI]: 2.64 [2.36-2.94]) and schizophrenia spectrum disorder (2.73 [2.63-2.84]). Among neurological disorders especially inflammatory brain diseases (1.73 [1.57-1.91]) and epilepsy (1.67 [1.60-1.75]) were associated with T2DM. Most associations remained in both directions in the temporally ordered analyses. For most psychiatric disorders, associations were strongest in females. CONCLUSIONS: T2DM was associated with several psychiatric and neurological disorders, and most associations were consistently found for both temporal order of disorders. This suggests a shared etiology of T2DM and those brain disorders. This study can form the starting point for studies directed at further elucidating potential causal links between disorders and shared biological mechanisms.

Transdiagnostic Perspective of Impulsivity and Compulsivity in Obesity: From Cognitive Profile to Self-Reported Dimensions in Clinical Samples with and without Diabetes.

Impulsive and compulsive behaviors have both been observed in individuals with obesity. The co-occurrence of obesity and type 2 diabetes (T2D) is more strongly associated with impulsivity, although there are no conclusive results yet. A multidimensional assessment of impulsivity and compulsivity was conducted in individuals with obesity in the absence or presence of T2D, compared with healthy, normal-weight individuals, with highly impulsive patients (gambling disorders), and with highly compulsive patients (anorexia nervosa). Decision making and novelty seeking were used to measure impulsivity, and cognitive flexibility and harm avoidance were used for compulsivity. For impulsivity, patients with obesity and T2D showed poorer decision-making ability compared with healthy individuals. For compulsivity, individuals with only obesity presented less cognitive flexibility and high harm avoidance; these dimensions were not associated with obesity with T2D. This study contributes to the knowledge of the mechanisms associated with diabetes and its association with impulsive-compulsive behaviors, confirming the hypothesis that patients with obesity and T2D would be characterized by higher levels of impulsivity.

Mismatch negativity as EEG biomarker supporting CNS drug development: a transnosographic and translational study.

The lack of translation from basic research into new medicines is a major challenge in CNS drug development. The need to use novel approaches relying on (i) patient clustering based on neurobiology irrespective to symptomatology and (ii) quantitative biomarkers focusing on evolutionarily preserved neurobiological systems allowing back-translation from clinical to nonclinical research has been highlighted. Here we sought to evaluate the mismatch negativity (MMN) response in schizophrenic (SZ) patients, Alzheimer's disease (AD) patients, and age-matched healthy controls. To evaluate back-translation of the MMN response, we developed EEG-based procedures allowing the measurement of MMN-like responses in a rat model of schizophrenia and a mouse model of AD. Our results indicate a significant MMN attenuation in SZ but not in AD patients. Consistently with the clinical findings, we observed a significant attenuation of deviance detection (~104.7%) in rats subchronically exposed to phencyclidine, while no change was observed in APP/PS1 transgenic mice when compared to wild type. This study provides new insight into the cross-disease evaluation of the MMN response. Our findings suggest further investigations to support the identification of neurobehavioral subtypes that may help patients clustering for precision medicine intervention. Furthermore, we provide evidence that MMN could be used as a quantitative/objective efficacy biomarker during both preclinical and clinical stages of SZ drug development.

Optimizing Behavioral Paradigms to Facilitate Development of New Treatments for Anhedonia and Reward Processing Deficits in Schizophrenia and Major Depressive Disorder: Study Protocol.

Background: Behavioral tasks focusing on different subdomains of reward processing may provide more objective and quantifiable measures of anhedonia and impaired motivation compared with clinical scales. Typically, single tasks are used in relatively small studies to compare cases and controls in one indication, but they are rarely included in larger multisite trials. This is due to limited systematic standardization as well as the challenges of deployment in international studies and stringent adherence to the high regulatory requirements for data integrity. The Reward Task Optimization Consortium (RTOC) was formed to facilitate operational implementation of reward processing tasks, making them suitable for use in future large-scale, international, multisite drug development studies across multiple indications. The RTOC clinical study aims to conduct initial optimization of a set of tasks in patients with major depressive disorder (MDD) or schizophrenia (SZ). Methods: We will conduct a multicenter study across four EU countries. Participants (MDD = 37, SZ = 37, with ≤80 age- and gender-matched healthy volunteers) will attend a study visit comprising screening, self-report and clinically rated assessments of anhedonia and symptom severity, and three reward processing tasks; specifically, the Grip Strength Effort task, the Doors task, and the Reinforcement Learning Working Memory task. The Grip Strength Effort and Doors tasks include simultaneous electroencephalography/event-related potential recordings. Outcomes will be compared using a two-way group design of MDD and SZ with matched controls, respectively. Further analyses will include anhedonia assessment scores as covariates. Planned analyses will assess whether our findings replicate previously published data, and multisite deployment will be evaluated through assessments of quality and conduct. A subset of participants will complete a second visit, to assess test-retest reliability of the task battery. Discussion: This study will evaluate the operational deployment of three reward processing tasks to the regulatory standards required for use in drug development trials. We will explore the potential of these tasks to differentiate patients from controls and to provide a quantitative marker of anhedonia and/or impaired motivation, establishing their usefulness as endpoints in multisite clinical trials. This study should demonstrate where multifaceted reward deficits are similar or divergent across patient populations. Registration: ClinicalTrials.gov (NCT04024371).

Relating constructs of attention and working memory to social withdrawal in Alzheimer's disease and schizophrenia: issues regarding paradigm selection.

Central nervous system diseases are not currently diagnosed based on knowledge of biological mechanisms underlying their symptoms. Greater understanding may be offered through an agnostic approach to traditional disease categories, where learning more about shared biological mechanisms across conditions could potentially reclassify sub-groups of patients to allow realisation of more effective treatments. This review represents the output of the collaborative group "PRISM", tasked with considering assay choices for assessment of attention and working memory in a transdiagnostic cohort of Alzheimer's disease and schizophrenia patients exhibiting symptomatic spectra of social withdrawal. A multidimensional analysis of this nature has not been previously attempted. Nominated assays (continuous performance test III, attention network test, digit symbol substitution, N-back, complex span, spatial navigation in a virtual environment) reflected a necessary compromise between the need for broad assessment of the neuropsychological constructs in question with several pragmatic criteria: patient burden, compatibility with neurophysiologic measures and availability of preclinical homologues.

A perspective on the contribution of animal models to the pharmacological treatment of posttraumatic stress disorder.

OBJECTIVES: Posttraumatic stress disorder (PTSD) is a prevalent, chronic, disabling disorder that may develop following exposure to a traumatic event. This review summarizes currently used animal models of PTSD and their potential role in the development of better therapeutics. Heterogeneity is one of the main characteristics of PTSD with the consequence that many pharmacological approaches are used to relieve symptoms of PTSD. To address the translational properties of the animal models, we discuss the types of stressors used, the rodent correlates of human PTSD (DSM-5) symptoms, and the efficacy of approved, recommended and off-label drugs used to treat PTSD in 'PTSD-animals'. CONCLUSIONS: Currently available animal models reproduce most PTSD symptoms and are validated by existing therapeutics. However, novel therapeutics are needed for this disorder as not one drug alleviates all symptoms and many have side effects that lead to non-compliance among PTSD patients. The true translational power of animal models of PTSD will only be demonstrated when new therapeutics acting through novel mechanisms become available for clinical practice.

In vivo pharmacological profile of S 38093, a novel histamine H3 receptor inverse agonist.

S 38093, a novel histamine H3 receptor inverse agonist, was tested in a series of neurochemical and behavioral paradigms designed to evaluate its procognitive and arousal properties. In intracerebral microdialysis studies performed in rats, S 38093 dose-dependently increased histamine extracellular levels in the prefrontal cortex and facilitated cholinergic transmission in the prefrontal cortex and hippocampus of rats after acute and chronic administration (10mg/kg i.p.). Acute oral administration of S 38093 at 0.1mg/kg significantly improved spatial working memory in rats in the Morris water maze test. The compound also displayed cognition enhancing properties in the two-trial object recognition task in rats, in a natural forgetting paradigm at 0.3 and 1mg/kg p.o. and in a scopolamine-induced memory deficit situation at 3mg/kg p.o. The property of S 38093 to promote episodic memory was confirmed in a social recognition test in rats at 0.3 and 1mg/kg i.p. Arousal properties of S 38093 were assessed in freely moving rats by using electroencephalographic recordings: at 3 and 10mg/kg i.p., S 38093 significantly reduced slow wave sleep delta power and induced at the highest dose a delay in sleep latency. S 38093 at 10mg/kg p.o. also decreased the barbital-induced sleeping time in rats. Taken together these data indicate that S 38093, a novel H3 inverse agonist, displays cognition enhancing at low doses and arousal properties at higher doses in rodents.

Memory facilitating effects of agomelatine in the novel object recognition memory paradigm in the rat.

The aim of the present study was to evaluate the effects of agomelatine, an antidepressant with melatonergic agonist and 5-HT(2C) antagonist properties, in the rat novel object recognition (NOR) task, a model of short-term episodic memory. To assess the potential involvement of its chronobiotic activity, single intraperitoneal administration of agomelatine and NOR testing were performed either in the evening or in the morning. In both conditions, using a 24h retention interval, vehicle-treated rats did not discriminate between the novel and the familiar object (recognition index was not different from chance performance) while object memory performance of rats treated with agomelatine either in the evening (10 and 40mg/kg) or in the morning (2.5, 10, and 40mg/kg) was significantly improved. Moreover, the selective 5-HT(2C) antagonist SB 242,084 (0.63, 2.5, and 10mg/kg) and melatonin (2.5, 10, and 40mg/kg) displayed also memory facilitating effects in both administration conditions. Finally, thioperamide used as positive reference compound to validate the experimental conditions, demonstrated a memory facilitating effect. In conclusion, agomelatine was shown to possess memory facilitating effects in the rat NOR task and both melatonergic agonist and 5-HT(2C) antagonist properties could be involved in these effects.

Translocator protein (18 kD) as target for anxiolytics without benzodiazepine-like side effects.

Most antianxiety drugs (anxiolytics) work by modulating neurotransmitters in the brain. Benzodiazepines are fast and effective anxiolytic drugs; however, their long-term use is limited by the development of tolerance and withdrawal symptoms. Ligands of the translocator protein [18 kilodaltons (kD)] may promote the synthesis of endogenous neurosteroids, which also exert anxiolytic effects in animal models. Here, we found that the translocator protein (18 kD) ligand XBD173 enhanced gamma-aminobutyric acid-mediated neurotransmission and counteracted induced panic attacks in rodents in the absence of sedation and tolerance development. XBD173 also exerted antipanic activity in humans and, in contrast to benzodiazepines, did not cause sedation or withdrawal symptoms. Thus, translocator protein (18 kD) ligands are promising candidates for fast-acting anxiolytic drugs with less severe side effects than benzodiazepines.

Antidepressant-like effects of agomelatine (S 20098) in the learned helplessness model.

To confirm the antidepressant-like activity of agomelatine (S 20098), a melatonin agonist and 5-hydroxytryptamine2C antagonist, already reported in the chronic mild stress and forced swimming tests, the effects of agomelatine were investigated in the learned helplessness test and compared with those of imipramine, melatonin and a selective 5-hydroxytryptamine2C antagonist, SB-242 084. Agomelatine was administered for 5 days either once a day or twice a day, and the effects of pretreatment by a melatonin receptor antagonist, S 22153 (20 mg/kg/day), were studied. A deficit in avoidance learning was observed in helpless control animals. Agomelatine (10 mg/kg/day) administered once a day significantly reduced this deficit with an effect similar to that of imipramine. Effects of agomelatine were abolished by S 22153 pretreatment. Melatonin or SB-242 084 did not reduce the deficit of helpless control animals. These results confirm the antidepressant-like activity of agomelatine and suggest a role of melatonin receptors in its mechanism of action.

Antidepressant properties of rotigotine in experimental models of depression.

Limited clinical data are available on the use of dopamine agonists for the control of motor function and also for the treatment of depression. This study was performed to evaluate the potential effects of the dopamine receptor agonist rotigotine in rat models of anxiety and depression. After repeated administration at doses of 0.05, 0.5, 1, and 5 mg/kg, rotigotine increased spontaneous motor activity at the 5 mg/kg dose after 3-5 days of treatment. At lower doses, the drug had no effect on locomotor activity. After a single administration, rotigotine had no anxiolytic activity in rats during the elevated plus-maze test or the Geller-Seifter conflict test. In the behavioral despair test (also known as the forced swim test), the 5 mg/kg dose of rotigotine enhanced the mobility of rats. Rotigotine (0.5, 1, and 5 mg/kg/day for 5 days) reversed the active avoidance deficit of helpless rats in the learned helplessness test, as shown by a significant decrease in escape failures after 3 to 4 days (0.5 mg/kg/day), 5 days (1 mg/kg/day), and 3 to 5 days (5 mg/kg/day) of treatment. During open-field testing of rats subjected to olfactory bulbectomy and given a 14-day schedule of rotigotine (0.3 mg/kg every 2 days), hyperactivity reversed according to a U-shaped dose-response curve. These results suggest that rotigotine may have antidepressant properties at doses of 1 mg/kg and lower. Potential effects at doses of 5 mg/kg and higher may be masked by an effect of the compound whereby general locomotor activity is enhanced.

Fragile X mental retardation protein is necessary for neurotransmitter-activated protein translation at synapses.

Fragile X mental retardation is caused by absence of the RNA-binding protein fragile X mental retardation protein (FMRP), encoded by the FMR1 gene. There is increasing evidence that FMRP regulates transport and modulates translation of some mRNAs. We studied neurotransmitter-activated synaptic protein synthesis in fmr1-knockout mice. Synaptoneurosomes from knockout mice did not manifest accelerated polyribosome assembly or protein synthesis as it occurs in wild-type mice upon stimulation of group I metabotropic glutamate receptors. Direct activation of protein kinase C did not compensate in the knockout mouse, indicating that the FMRP-dependent step is further along the signaling pathway. Visual cortices of young knockout mice exhibited a lower proportion of dendritic spine synapses containing polyribosomes than did the cortices of wild-type mice, corroborating this finding in vivo. This deficit in rapid neurotransmitter-controlled local translation of specific proteins may contribute to morphological and functional abnormalities observed in patients with fragile X syndrome.

Genetic approach to variability of memory systems: analysis of place vs. response learning and fos-related expression in hippocampal and striatal areas of C57BL/6 and DBA/2 mice.

C57 and DBA mice were trained in a crossed maze to assess possible strain differences in place or response learning as a function of training duration (8 or 17 days) and extramaze cueing conditions. The first condition consisted of a diffuse visually cued environment (rich cueing). The second was the same plus an explicit visual cue marking the direction of the baited arm (rich cueing plus cue). The third was a featureless environment (poor cueing). During training, mice were released from the south arm and rewarded in the east arm. Probe trials on which mice were released from the north arm and allowed to choose either the east (place learning) or the west (response learning) arm were given either on the ninth (PT1) or the eighteenth (PT2) days. Strain x context differences in the activation of the dorsal hippocampus and the dorsolateral striatum were examined by analyzing Fos expression following each probe trial. Results first showed that C57 were essentially place-learners, whereas no learning modality was predominant in DBA, except on the PT2 run with the explicit cue available. Examination of Fos expression in C57 trained under "rich cueing" and "rich cueing plus cue" conditions revealed a strong and parallel increase of immunoreactivity in the hippocampus and dorsolateral striatum following PT1 that decreased under PT2. In that strain, the similar time-course variation of Fos expression in both areas suggests a simultaneous involvement of hippocampal- and striatal-based learning mechanisms, even if those controlled by the hippocampus were prevailing on those controlled by the dorsolateral striatum. In DBA mice, however, the absence of any preferential learning modality was associated with 1) a consistent hippocampal activation persistent across probe trials, and 2) a global superior activation of the dorsolateral striatum. Distinct patterns of Fos expression were therefore associated with every strain-specific learning modality. In each strain, however, each modality was found to be remarkably stable, whatever the training duration and the cueing conditions.