Glyceraldehyde metabolism in mouse brain and the entry of blood-borne glyceraldehyde into the brain.

D-Glyceraldehyde, a reactive aldehyde metabolite of fructose and glucose, is neurotoxic in vitro by forming advanced glycation end products (AGEs) with neuronal proteins. In Alzheimer's disease brains, glyceraldehyde-containing AGEs have been detected intracellularly and in extracellular plaques. However, little information exists on how the brain handles D-glyceraldehyde metabolically or if glyceraldehyde crosses the blood-brain barrier from the circulation into the brain. We injected [U-13C]-D-glyceraldehyde intravenously into awake mice and analyzed extracts of serum and brain by 13C nuclear magnetic resonance spectroscopy. 13C-Labeling of brain lactate and glutamate indicated passage of D-glyceraldehyde from blood to brain and glycolytic and oxidative D-glyceraldehyde metabolism in brain cells. 13C-Labeling of serum glucose and lactate through hepatic metabolism of [U-13C]-D-glyceraldehyde could not explain the formation of 13C-labeled lactate and glutamate in the brain. Cerebral glyceraldehyde dehydrogenase and reductase activities, leading to the formation of D-glycerate and glycerol, respectively, were 0.27-0.28 nmol/mg/min; triokinase, which phosphorylates D-glyceraldehyde to D-glyceraldehyde-3-phosphate, has been demonstrated previously at low levels. Thus, D-glyceraldehyde metabolism toward glycolysis could proceed both through D-glycerate, glycerol, and D-glyceraldehyde-3-phosphate. The aldehyde group of D-glyceraldehyde was overwhelmingly hydrated into a diol in aqueous solution, but the diol dehydration rate greatly exceeded glyceraldehyde metabolism and did not restrict it. We conclude that (1) D-glyceraldehyde crosses the blood-brain barrier, and so blood-borne glyceraldehyde could contribute to AGE formation in the brain, (2) glyceraldehyde is taken up and metabolized by brain cells. Metabolism thus constitutes a detoxification mechanism for this reactive aldehyde, a mechanism that may be compromised in disease states.

Cognitive and everyday functioning after bacterial brain abscess: a prospective study of functional recovery from 8 weeks to 1 year post-treatment.

OBJECTIVE: A bacterial brain abscess may damage surrounding brain tissue by mass effect, inflammatory processes, and bacterial toxins. The aim of this study was to examine cognitive and functional outcomes at 8 weeks and 1 year following acute treatment. METHODS: Prospective study of 20 patients with bacterial brain abscess (aged 17-73 years; 45% females) with neuropsychological assessment at 8 weeks and 1 year post-treatment. Behavior Rating Inventory of Executive Function-Adult Version (BRIEF-A) and Patient Competence Rating Scale (PCRS) were used to assess everyday functioning and administered to patients and informants. RESULTS: Cognitive impairment was found in 30% of patients at 8 weeks and 22% at 1 year. Significant improvements were seen on tests of perceptual reasoning, attention, verbal fluency, and motor abilities (p < 0.05). At 1 year, 45% had returned to full-time employment. Nevertheless, patients and their informants obtained scores within the normal range on measures of everyday functioning (PCRS and BRIEF-A) at 8 weeks and 1 year. No significant improvements on these measures emerged over time. CONCLUSION: Residual long-term cognitive impairment and diminished work ability affected 22% and 45% of patients one year after BA. Persistent cognitive impairment emphasizes the importance of prompt acute treatment and cognitive rehabilitation.

Bacterial Brain Abscesses Expand Despite Effective Antibiotic Treatment: A Process Powered by Osmosis Due to Neutrophil Cell Death.

BACKGROUND AND OBJECTIVES: A bacterial brain abscess is an emergency and should be drained of pus within 24 hours of diagnosis, as recently recommended. In this cross-sectional study, we investigated whether delaying pus drainage entails brain abscess expansion and what the underlying mechanism might be. METHODS: Repeated brain MRI of 47 patients who did not undergo immediate pus drainage, pus osmolarity measurements, immunocytochemistry, proteomics, and 18F-fluorodeoxyglucose positron emission tomography. RESULTS: Time from first to last MRI before neurosurgery was 1 to 14 days. Abscesses expanded in all but 2 patients: The median average increase was 23% per day (range 0%-176%). Abscesses expanded during antibiotic therapy and even if the pus did not contain viable bacteria. In a separate patient cohort, we found that brain abscess pus tended to be hyperosmolar (median value 360 mOsm; range 266-497; n = 14; normal cerebrospinal fluid osmolarity is ∼290 mOsm). Hyperosmolarity would draw water into the abscess cavity, causing abscess expansion in a ballooning manner through increased pressure in the abscess cavity. A mechanism likely underlying pus hyperosmolarity was the recruitment of neutrophils to the abscess cavity with ensuing neutrophil cell death and decomposition of neutrophil proteins and other macromolecules to osmolytes: Pus analysis showed the presence of neutrophil proteins (protein-arginine deiminases, citrullinated histone, myeloperoxidase, elastase, cathelicidin). Previous studies have shown very high levels of osmolytes (ammonia, amino acids) in brain abscess pus. 18F-fluorodeoxyglucose positron emission tomography showed focal neocortical hypometabolism 1 to 8 years after brain abscess, indicating long-lasting damage to brain tissue. CONCLUSION: Brain abscesses expand despite effective antibiotic treatment. Furthermore, brain abscesses cause lasting damage to surrounding brain tissue. These findings support drainage of brain abscesses within 24 hours of diagnosis.

Heart rate monitoring to detect acute pain in non-verbal patients: a study protocol for a randomized controlled clinical trial.

BACKGROUND: Autism entails reduced communicative abilities. Approximately 30% of individuals with autism have intellectual disability (ID). Some people with autism and ID are virtually non-communicative and unable to notify their caregivers when they are in pain. In a pilot study, we showed that heart rate (HR) monitoring may identify painful situations in this patient group, as HR increases in acutely painful situations. OBJECTIVES: This study aims to generate knowledge to reduce the number of painful episodes in non-communicative patients' everyday lives. We will 1) assess the effectiveness of HR as a tool for identifying potentially painful care procedures, 2) test the effect of HR-informed changes in potentially painful care procedures on biomarkers of pain, and 3) assess how six weeks of communication through HR affects the quality of communication between patient and caregiver. METHODS: We will recruit 38 non-communicative patients with autism and ID residing in care homes. ASSESSMENTS: HR is measured continuously to identify acutely painful situations. HR variability and pain-related cytokines (MCP-1, IL-1RA, IL-8, TGFß1, and IL-17) are collected as measures of long-term pain. Caregivers will be asked to what degree they observe pain in their patients and how well they believe they understand their patient's expressions of emotion and pain. Pre-intervention: HR is measured 8 h/day over 2 weeks to identify potentially painful situations across four settings: physiotherapy, cast use, lifting, and personal hygiene. INTERVENTION: Changes in procedures for identified painful situations are in the form of changes in 1) physiotherapy techniques, 2) preparations for putting on casts, 3) lifting techniques or 4) personal hygiene procedures. DESIGN: Nineteen patients will start intervention in week 3 while 19 patients will continue data collection for another 2 weeks before procedure changes are introduced. This is done to distinguish between specific effects of changes in procedures and non-specific effects, such as caregivers increased attention. DISCUSSION: This study will advance the field of wearable physiological sensor use in patient care. TRIAL REGISTRATION: Registered prospectively at ClinicalTrials.gov (NCT05738278).

The spectrum of pyridoxine dependent epilepsy across the age span: A nationwide retrospective observational study.

BACKGROUND: Pyridoxine-dependent epilepsy (PDE) is a rare seizure disorder usually presenting with neonatal seizures. Most cases are caused by biallelic pathogenic ALDH7A1variants. While anti-seizure medications are ineffective, pyridoxine provides seizure control, and dietary interventions may be of benefit. As the natural history beyond adolescence is insufficiently explored, our study aimed to assess the spectrum of PDE at various ages in Norway. METHODS: Patients were ascertained by contacting all Norwegian paediatric, neurological, and neurohabilitation departments and relevant professional societies. Medical records were collected and reviewed. RESULTS: We identified 15 patients treated for PDE; 13 had ALDH7A1 variants (PDE-ALDH7A1), one had PNPO deficiency, and in one, aetiology remained obscure. Of those with PDE-ALDH7A1, 12 were alive at time of study; five were > 18 years old and six were < 4 years. Median age was 10 years (range 2 months-53 years). Estimated minimum prevalence was 6.3/million among children and 1.2/million among adults. Ten had seizure onset on the first day of life. Perinatal complications and neuroradiological abnormalities suggested additional seizure aetiologies in several patients. Pyridoxine had immediate effect in six, while six had delayed (>1 h) or uncertain effect. Median delay from first seizure to continuous treatment was 11 days (range 0-42). Nine experienced breakthrough seizures with intercurrent disease or due to pyridoxine discontinuation. Cognitive outcomes ranged from normal to severe intellectual disability. The condition appeared to remain stable in adult life. SIGNIFICANCE: We found a much higher prevalence of PDE-ALDH7A1 in children relative to adults, suggesting previous underdiagnosis and early mortality. Perinatal complications are common and can delay diagnosis and initiation of pyridoxine treatment. Lifelong and continuous treatment with pyridoxine is imperative. Due to better diagnostics and survival, the number of adult patients is expected to rise.

Cerebrospinal fluid quinolinic acid is strongly associated with delirium and mortality in hip-fracture patients.

BACKGROUNDThe kynurenine pathway (KP) has been identified as a potential mediator linking acute illness to cognitive dysfunction by generating neuroactive metabolites in response to inflammation. Delirium (acute confusion) is a common complication of acute illness and is associated with increased risk of dementia and mortality. However, the molecular mechanisms underlying delirium, particularly in relation to the KP, remain elusive.METHODSWe undertook a multicenter observational study with 586 hospitalized patients (248 with delirium) and investigated associations between delirium and KP metabolites measured in cerebrospinal fluid (CSF) and serum by targeted metabolomics. We also explored associations between KP metabolites and markers of neuronal damage and 1-year mortality.RESULTSIn delirium, we found concentrations of the neurotoxic metabolite quinolinic acid in CSF (CSF-QA) (OR 2.26 [1.78, 2.87], P < 0.001) to be increased and also found increases in several other KP metabolites in serum and CSF. In addition, CSF-QA was associated with the neuronal damage marker neurofilament light chain (NfL) (ß 0.43, P < 0.001) and was a strong predictor of 1-year mortality (HR 4.35 [2.93, 6.45] for CSF-QA ≥ 100 nmol/L, P < 0.001). The associations between CSF-QA and delirium, neuronal damage, and mortality remained highly significant following adjustment for confounders and multiple comparisons.CONCLUSIONOur data identified how systemic inflammation, neurotoxicity, and delirium are strongly linked via the KP and should inform future delirium prevention and treatment clinical trials that target enzymes of the KP.FUNDINGNorwegian Health Association and South-Eastern Norway Regional Health Authorities.

People with intellectual disabilities and harmful sexual behaviour: Professionals' views on the barriers to prevent harm.

BACKGROUND: People with intellectual disabilities can be exposed to sexual abuse and they can display harmful sexual behaviour. This study aimed to identify barriers to preventing harmful sexual behaviour in people with intellectual disabilities within the support sector and the justice system. METHOD: We conducted focus group interviews with 20 participants from hospital-based habilitation centres, community residences, schools and the criminal justice system. RESULTS: The interviews identified a lack of education and guidelines for stakeholders or carers on regulating the sexual behaviour of people with intellectual disabilities. The criminal justice system faces challenges related to prioritising, understanding and communicating. People with intellectual disabilities may lack an understanding of the concepts of sexual consent and acceptable sexual behaviour. CONCLUSION: There is a need to improve knowledge about intellectual disability and how to prevent harmful sexual behaviour for professional caregivers in the support sector and the criminal justice system.

Improvement of attention deficit/hyperactivity disorder (ADHD) in three adult men during testosterone treatment: a case series.

BACKGROUND: Attention deficit/hyperactivity disorder (ADHD) entails inattention, impulsivity, and restlessness at a disabling level. The pharmacological treatment of ADHD rests on the use of centrally acting stimulants, such as methylphenidate and D-amphetamine. In some patients, these drugs cause side effects that preclude their use. CASE PRESENTATION: We present three adult male, Caucasian, ADHD patients (24, 37, and 43 years old) whose ADHD symptoms improved during treatment with testosterone. The first patient experienced loss of libido during treatment with methylphenidate; for this, he was offered a trial of testosterone. Unexpectedly, his ADHD symptoms improved with testosterone treatment, and this effect continued with testosterone as monotherapy. The two other patients, who also had side effects from centrally acting stimulants, received testosterone monotherapy with similar results. The effect has now continued for 4.5-5 years at the same doses: 10-60 mg testosterone/day, administered as a skin gel. Prior to testosterone treatment, the patients had serum levels of testosterone in the low-normal range: 12-16 nmol/L (age-specific reference range: 10.4-32.6 nmol/L). The testosterone/sex hormone-binding globulin ratio was low in two patients (0.32 and 0.34; age-specific reference range: 0.38-1.1), suggesting low free serum levels of testosterone. Serum testosterone levels and testosterone/sex hormone-binding globulin ratios increased with testosterone treatment in all patients, but remained within reference values. CONCLUSION: These cases suggest that a moderately reduced serum level of free testosterone may contribute to the ADHD symptoms of some adult male ADHD patients, and that testosterone treatment may be of value for these patients.

Pro-inflammatory cytokines in cystic glioblastoma: A quantitative study with a comparison with bacterial brain abscesses. With an MRI investigation of displacement and destruction of the brain tissue surrounding a glioblastoma.

Cystic glioblastomas are aggressive primary brain tumors that may both destroy and displace the surrounding brain tissue as they grow. The mechanisms underlying these tumors' destructive effect could include exposure of brain tissue to tumor-derived cytokines, but quantitative cytokine data are lacking. Here, we provide quantitative data on leukocyte markers and cytokines in the cyst fluid from 21 cystic glioblastomas, which we compare to values in 13 brain abscess pus samples. The concentration of macrophage/microglia markers sCD163 and MCP-1 was higher in glioblastoma cyst fluid than in brain abscess pus; lymphocyte marker sCD25 was similar in cyst fluid and pus, whereas neutrophil marker myeloperoxidase was higher in pus. Median cytokine levels in glioblastoma cyst fluid were high (pg/mL): TNF-α: 32, IL-6: 1064, IL-8: 23585, tissue factor: 28, the chemokine CXCL1: 639. These values were not significantly different from values in pus, pointing to a highly pro-inflammatory glioblastoma environment. In contrast, levels of IFN-γ, IL-1ß, IL-2, IL-4, IL-10, IL-12, and IL-13 were higher in pus than in glioblastoma cyst fluid. Based on the quantitative data, we show for the first time that the concentrations of cytokines in glioblastoma cyst fluid correlate with blood leukocyte levels, suggesting an important interaction between glioblastomas and the circulation. Preoperative MRI of the cystic glioblastomas confirmed both destruction and displacement of brain tissue, but none of the cytokine levels correlated with degree of brain tissue displacement or peri-tumoral edema, as could be assessed by MRI. We conclude that cystic glioblastomas are highly pro-inflammatory environments that interact with the circulation and that they both displace and destroy brain tissue. These observations point to the need for neuroprotective strategies in glioblastoma therapy, which could include an anti-inflammatory approach.

ADHD symptoms and use of anabolic androgenic steroids among male weightlifters.

Use of anabolic androgenic steroids (AAS) is associated with adverse health effects. The factors that predispose to AAS use among athletes are poorly understood, but attention deficit/hyperactivity disorder (ADHD), which is known to occur among athletes more often than in the general population, is associated with risk behaviors, including substance abuse. We aimed to see if AAS use in male weightlifters was associated with ADHD symptoms, and test the link between ADHD symptoms and cognitive performance. Hundred and forty male weightlifters, 72 AAS users and 68 weightlifting controls (WLC), completed the Achenbach system of empirically based assessment (ASEBA) for ADHD symptoms and underwent cognitive examination. Self-reported ADHD symptom scores were significantly higher among AAS users compared to WLC, and scores in the range indicating clinically important ADHD was significantly more common in the AAS-using group. Age of onset of AAS use correlated inversely with ADHD scale score (r = - 0.35; p = 0.003). ADHD score correlated inversely with cognitive scores for working memory (r = - 0.25, p < 0.001), processing speed (r = - 0.24, p < 0.001), verbal learning and memory (r = - 0.19, p = 0.03), and problem solving (r = - 0.20, p = 0.02). AAS use among weightlifters is associated with ADHD symptoms and corresponding lower cognitive performance. Recognising a relationship between ADHD symptoms and AAS use may guide drug prevention strategies in sports.

Glioblastoma microenvironment contains multiple hormonal and non-hormonal growth-stimulating factors.

BACKGROUND: The growth of malignant tumors is influenced by their microenvironment. Glioblastoma, an aggressive primary brain tumor, may have cysts containing fluid that represents the tumor microenvironment. The aim of this study was to investigate whether the cyst fluid of cystic glioblastomas contains growth-stimulating factors. Identification of such growth factors may pave the way for the development of targeted anti-glioblastoma therapies. METHODS: We performed hormone analysis of cyst fluid from 25 cystic glioblastomas and proteomics analysis of cyst fluid from another 12 cystic glioblastomas. RESULTS: Glioblastoma cyst fluid contained hormones within wide concentration ranges: Insulin-like growth factor 1 (0-13.7 nmol/L), insulin (1.4-133 pmol/L), erythropoietin (4.7-402 IU/L), growth hormone (0-0.93 µg/L), testosterone (0.2-10.1 nmol/L), estradiol (0-1.0 nmol/L), triiodothyronine (1.0-11.5). Tumor volume correlated with cyst fluid concentrations of growth hormone and testosterone. Survival correlated inversely with cyst fluid concentration of erythropoietin. Several hormones were present at concentrations that have been shown to stimulate glioblastoma growth in vitro. Concentrations of erythropoietin and estradiol (in men) were higher in cyst fluid than in serum, suggesting formation by tumor or brain tissue. Quantitatively, glioblastoma cyst fluid was dominated by serum proteins, illustrating blood-brain barrier leakage. Proteomics identified several proteins that stimulate tumor cell proliferation and invasiveness, others that inhibit apoptosis or mediate adaption to hypoxia and some that induce neovascularization or blood-brain barrier leakage. CONCLUSION: The microenvironment of glioblastomas is rich in growth-stimulating factors that may originate from the circulation, the tumor, or the brain. The wide variation in cyst fluid hormone concentrations may differentially influence tumor growth.

Cerebrospinal fluid catecholamines in delirium and dementia.

Dopamine and noradrenaline are functionally connected to delirium and have been targets for pharmacological interventions but the biochemical evidence to support this notion is limited. To study the CSF levels of dopamine, noradrenaline and the third catecholamine adrenaline in delirium and dementia, these were quantified in three patient cohorts: (i) cognitively normal elderly patients (n = 122); (ii) hip fracture patients with or without delirium and dementia (n = 118); and (iii) patients with delirium precipitated by another medical condition (medical delirium, n = 26). Delirium was assessed by the Confusion Assessment Method. The hip fracture cohort had higher CSF levels of noradrenaline and adrenaline than the two other cohorts (both P < 0.001). Within the hip fracture cohort those with delirium (n = 65) had lower CSF adrenaline and dopamine levels than those without delirium (n = 52, P = 0.03, P = 0.002). Similarly, the medical delirium patients had lower CSF dopamine levels than the cognitively normal elderly (P < 0.001). Age did not correlate with the CSF catecholamine levels. These findings with lower CSF dopamine levels in hip fracture- and medical delirium patients challenge the theory of dopamine excess in delirium and question use of antipsychotics in delirium. The use of alpha-2 agonists with the potential to reduce noradrenaline release needs further examination.

Clinical application of intrathecal gadobutrol for assessment of cerebrospinal fluid tracer clearance to blood.

BACKGROUNDMethodology for estimation of cerebrospinal fluid (CSF) tracer clearance could have wide clinical application in predicting excretion of intrathecal drugs and metabolic solutes from brain metabolism and for diagnostic workup of CSF disturbances.METHODSThe MRI contrast agent gadobutrol (Gadovist) was used as a CSF tracer and injected into the lumbar CSF. Gadobutrol is contained outside blood vessels of the CNS and is eliminated along extravascular pathways, analogous to many CNS metabolites and intrathecal drugs. Tracer enrichment was verified and assessed in CSF by MRI at the level of the cisterna magna in parallel with obtaining blood samples through 48 hours.RESULTSIn a reference patient cohort (n = 29), both enrichment within CSF and blood coincided in time. Blood concentration profiles of gadobutrol through 48 hours varied between patients diagnosed with CSF leakage (n = 4), idiopathic normal pressure hydrocephalus dementia (n = 7), pineal cysts (n = 8), and idiopathic intracranial hypertension (n = 4).CONCLUSIONAssessment of CSF tracer clearance is clinically feasible and may provide a way to predict extravascular clearance of intrathecal drugs and endogenous metabolites from the CNS. The peak concentration in blood (at about 10 hours) was preceded by far peak tracer enhancement at MRI in extracranial lymphatic structures (at about 24 hours), as shown in previous studies, indicating a major role of the spinal canal in CSF clearance capacity.FUNDINGThe work was supported by the Department of Neurosurgery, Oslo University Hospital; the Norwegian Institute for Air Research; and the University of Oslo.

Increased heart rate functions as a signal of acute distress in non-communicating persons with intellectual disability.

Intellectual disability (ID) affects approximately 1% of the population. Some patients with severe or profound ID are essentially non-communicating and therefore risk experiencing pain and distress without being able to notify their caregivers, which is a major health issue. This real-world proof of concept study aimed to see if heart rate (HR) monitoring could reveal whether non-communicating persons with ID experience acute pain or distress in their daily lives. We monitored HR in 14 non-communicating participants with ID in their daily environment to see if specific situations were associated with increased HR. We defined increased HR as being > 1 standard deviation above the daily mean and lasting > 5 s. In 11 out of 14 participants, increased HR indicated pain or distress in situations that were not previously suspected to be stressful, e.g. passive stretching of spastic limbs or being transported in patient lifts. Increased HR suggesting joy was detected in three participants (during car rides, movies). In some situations that were previously suspected to be stressful, absence of HR increase suggested absence of pain or distress. We conclude that HR monitoring may identify acute pain and distress in non-communicating persons with ID, allowing for improved health care for this patient group.

ß-Amyloid may accumulate in the human brain after focal bacterial infection: An 18 F-flutemetamol positron emission tomography study.

BACKGROUND AND PURPOSE: ß-Amyloid formation has been suggested to form part of the brain's response to bacterial infection. This hypothesis has been based on experimental animal studies and autopsy studies in humans. We asked if ß-amyloid accumulates locally around a bacterial brain abscess in living human patients. Furthermore, because brain abscess patients may suffer from chronic cognitive symptoms after abscess treatment, we also asked if a brain abscess precipitates accumulation of ß-amyloid in the neocortex in a manner that could explain abscess-related cognitive complaints. METHODS: In a prospective study, we investigated 17 brain abscess patients (age 24-72 years) with 18 F-flutemetamol positron emission tomography on one occasion 1 to 10 months after brain abscess treatment to visualize ß-amyloid accumulation. RESULTS: 18 F-flutemetamol uptake was reduced in the edematous brain tissue that surrounded the abscess remains. On this background of reduced 18 F-flutemetamol signal, three out of 17 patients showed a distinctly increased 18 F-flutemetamol uptake in the tissue immediately surrounding the abscess remains, suggesting accumulation of ß-amyloid. These three patients underwent 18 F-flutemetamol positron emission tomography significantly earlier after neurosurgical treatment (p = 0.042), and they had larger abscesses (p = 0.027) than the rest of the patients. All 17 patients suffered from mental fatigue or some subjective cognitive symptom, such as attention difficulties or memory problems, but in none of the patients was there an increase in neocortical 18 F-flutemetamol signal. CONCLUSIONS: ß-Amyloid may accumulate locally around the abscess remains in some patients with a brain abscess.

Novel aspects of glutamine synthetase in ammonia homeostasis.

Elevated blood ammonia (hyperammonemia) is believed to be a major contributor to the neurological sequelae following severe liver disease. Ammonia is cleared via two main mechanisms, the urea cycle pathway and the glutamine synthetase reaction. Recent studies of genetically modified animals confirm the importance of the urea cycle, but also suggest that the glutamine synthetase reaction is more important than previously recognized. While the liver clears about two-thirds of the body's ammonia via the combined action of the urea cycle and glutamine synthetase, extrahepatic tissues do not express all the components required for performing a complete urea cycle and therefore depend on the glutamine synthetase reaction for ammonia clearance. The brain is particularly vulnerable to the effects of hyperammonemia, which include impaired extracellular potassium buffering and brain edema. Moreover, the glutamine synthetase reaction is intimately linked to the metabolism of the excitatory and inhibitory neurotransmitters glutamate and gamma aminobutyric acid (GABA), implicating a key role for this enzyme in neurotransmission. This review discusses the emerging roles of glutamine synthetase in brain pathophysiology, particularly aspects related to ammonia homeostasis and hepatic encephalopathy.

Slc38a1 Conveys Astroglia-Derived Glutamine into GABAergic Interneurons for Neurotransmitter GABA Synthesis.

GABA signaling is involved in a wide range of neuronal functions, such as synchronization of action potential firing, synaptic plasticity and neuronal development. Sustained GABA signaling requires efficient mechanisms for the replenishment of the neurotransmitter pool of GABA. The prevailing theory is that exocytotically released GABA may be transported into perisynaptic astroglia and converted to glutamine, which is then shuttled back to the neurons for resynthesis of GABA-i.e., the glutamate/GABA-glutamine (GGG) cycle. However, an unequivocal demonstration of astroglia-to-nerve terminal transport of glutamine and the contribution of astroglia-derived glutamine to neurotransmitter GABA synthesis is lacking. By genetic inactivation of the amino acid transporter Solute carrier 38 member a1 (Slc38a1)-which is enriched on parvalbumin+ GABAergic neurons-and by intraperitoneal injection of radiolabeled acetate (which is metabolized to glutamine in astroglial cells), we show that Slc38a1 mediates import of astroglia-derived glutamine into GABAergic neurons for synthesis of GABA. In brain slices, we demonstrate the role of Slc38a1 for the uptake of glutamine specifically into GABAergic nerve terminals for the synthesis of GABA depending on demand and glutamine supply. Thus, while leaving room for other pathways, our study demonstrates a key role of Slc38a1 for newly formed GABA, in harmony with the existence of a GGG cycle.

Sudden death in epilepsy and ectopic neurohypophysis in Joubert syndrome 23 diagnosed using SNVs/indels and structural variants pipelines on WGS data: a case report.

BACKGROUND: Joubert syndrome (JBTS) is a genetically heterogeneous group of neurodevelopmental syndromes caused by primary cilia dysfunction. Usually the neurological presentation starts with abnormal neonatal breathing followed by muscular hypotonia, psychomotor delay, and cerebellar ataxia. Cerebral MRI shows mid- and hindbrain anomalies including the molar tooth sign. We report a male patient with atypical presentation of Joubert syndrome type 23, thus expanding the phenotype. CASE PRESENTATION: Clinical features were consistent with JBTS already from infancy, yet the syndrome was not suspected before cerebral MRI later in childhood showed the characteristic molar tooth sign and ectopic neurohypophysis. From age 11 years seizures developed and after few years became increasingly difficult to treat, also related to inadequate compliance to therapy. He died at 23 years of sudden unexpected death in epilepsy (SUDEP). The genetic diagnosis remained elusive for many years, despite extensive genetic testing. We reached the genetic diagnosis by performing whole genome sequencing of the family trio and analyzing the data with the combination of one analysis pipeline for single nucleotide variants (SNVs)/indels and one for structural variants (SVs). This lead to the identification of the most common variant detected in patients with JBTS23 (OMIM# 616490), rs534542684, in compound heterozygosity with a 8.3 kb deletion in KIAA0586, not previously reported. CONCLUSIONS: We describe for the first time ectopic neurohypophysis and SUDEP in JBTS23, expanding the phenotype of this condition and raising the attention on the possible severity of the epilepsy in this disease. We also highlight the diagnostic power of WGS, which efficiently detects SNVs/indels and in addition allows the identification of SVs.

The Glutamine Transporter Slc38a1 Regulates GABAergic Neurotransmission and Synaptic Plasticity.

GABA signaling sustains fundamental brain functions, from nervous system development to the synchronization of population activity and synaptic plasticity. Despite these pivotal features, molecular determinants underscoring the rapid and cell-autonomous replenishment of the vesicular neurotransmitter GABA and its impact on synaptic plasticity remain elusive. Here, we show that genetic disruption of the glutamine transporter Slc38a1 in mice hampers GABA synthesis, modifies synaptic vesicle morphology in GABAergic presynapses and impairs critical period plasticity. We demonstrate that Slc38a1-mediated glutamine transport regulates vesicular GABA content, induces high-frequency membrane oscillations and shapes cortical processing and plasticity. Taken together, this work shows that Slc38a1 is not merely a transporter accumulating glutamine for metabolic purposes, but a key component regulating several neuronal functions.