SPECT/CT SUV-based metrics: A promising diagnostic tool in classifying patients with suspected transthyretin cardiac amyloidosis among the different Perugini grades?

OBJECTIVE: The purpose of this study was to evaluate the contribution of single photon emission computed tomography/computed tomography (SPECT/CT) standardized uptake value (SUV) metrics in classifying patients with suspected transthyretin cardiac amyloidosis (ATTR-CA) among the different Perugini grades. SUBJECTS AND METHODS: One hundred four patients suspected of ATTR-CA underwent planar scintigraphy with bone seeking tracer (99mTc pyrophosphate-PYP). Patients were classified according to the Perugini scale, the H/CL, H/Bone and H/Bkg ratios. A subset of 48 patients received additional SPECT/CT. Single photon emission computed tomography/CT SUV quantitative parameters, of the heart, myocardium, lungs, liver, soft tissues, bone, and SUV ratios (SUVmaxmyo, SUVmaxlungs, SUVmaxliver, SUVmaxbone and SUVmaxsoft tissue ratios), were evaluated in order to investigate potential metrics that could more clearly differentiate Perugini grades. RESULTS: A total of 33.7% of patients were considered grade 0, 34.6% grade 1 and 31.7% grade 2/3. A combination of H/CL >1.33 and H/Bone >0.85 showed the highest sensitivity 100%. Standardized uptake value-based metrics clearly differentiated grade 0 or 1 vs grades 2 or 3, whereas no significant difference was found between grades 0 and 1, or between grades 1 and 2. The combined cut-off values H/CL 1.33 and SUVmaxmyo 2.88 yielded 100% sensitivity and 84.6% specificity in differentiating ATTR-CA positives vs negatives. The metric SUVmaxmyo/SUVmaxliver was the best metric to classify patients with grade 1 as negative (grade 0) or positive (grade 2 or 3). CONCLUSION: Single photon emission computed tomography/CT SUV metrics could be complementary to planar scintigraphy in classifying patients among the different Perugini grades. The ratio SUVmaxmyo/SUVmaxliver was the only parameter with high affinity to differentiate patients with grade 1, as grade 0 or grade 2/3 for ATTR-CA.

Personalized screening and risk profiles for Mild Cognitive Impairment via a Machine Learning Framework: Implications for general practice.

OBJECTIVES: Diagnosis of Mild Cognitive Impairment (MCI) requires lengthy diagnostic procedures, typically available at tertiary Health Care Centers (HCC). This prospective study evaluated a flexible Machine Learning (ML) framework toward identifying persons with MCI or dementia based on information that can be readily available in a primary HC setting. METHODS: Demographic and clinical data, informant ratings of recent behavioral changes, self-reported anxiety and depression symptoms, subjective cognitive complaints, and Mini Mental State Examination (MMSE) scores were pooled from two aging cohorts from the island of Crete, Greece (N = 763 aged 60-93 years) comprising persons diagnosed with MCI (n = 277) or dementia (n = 153), and cognitively non-impaired persons (CNI, n = 333). A Balanced Random Forest Classifier was used for classification and variable importance-based feature selection in nested cross-validation schemes (CNI vs MCI, CNI vs Dementia, MCI vs Dementia). Global-level model-agnostic analyses identified predictors displaying nonlinear behavior. Local level agnostic analyses pinpointed key predictor variables for a given classification result after statistically controlling for all other predictors in the model. RESULTS: Classification of MCI vs CNI was achieved with improved sensitivity (74 %) and comparable specificity (73 %) compared to MMSE alone (37.2 % and 94.3 %, respectively). Additional high-ranking features included age, education, behavioral changes, multicomorbidity and polypharmacy. Higher classification accuracy was achieved for MCI vs Dementia (sensitivity/specificity = 87 %) and CNI vs Dementia (sensitivity/specificity = 94 %) using the same set of variables. Model agnostic analyses revealed notable individual variability in the contribution of specific variables toward a given classification result. CONCLUSIONS: Improved capacity to identify elderly with MCI can be achieved by combining demographic and medical information readily available at the PHC setting with MMSE scores, and informant ratings of behavioral changes. Explainability at the patient level may help clinicians identify specific predictor variables and patient scores to a given prediction outcome toward personalized risk assessment.

Structural Evolution of Primate Glutamate Dehydrogenase 2 as Revealed by In Silico Predictions and Experimentally Determined Structures.

Glutamate dehydrogenase (GDH) interconverts glutamate to a-ketoglutarate and ammonia, interconnecting amino acid and carbohydrate metabolism. In humans, two functional GDH genes, GLUD1 and GLUD2, encode for hGDH1 and hGDH2, respectively. GLUD2 evolved from retrotransposition of the GLUD1 gene in the common ancestor of modern apes. These two isoenzymes are involved in the pathophysiology of human metabolic, neoplastic, and neurodegenerative disorders. The 3D structures of hGDH1 and hGDH2 have been experimentally determined; however, no information is available about the path of GDH2 structure changes during primate evolution. Here, we compare the structures predicted by the AlphaFold Colab method for the GDH2 enzyme of modern apes and their extinct primate ancestors. Also, we analyze the individual effect of amino acid substitutions emerging during primate evolution. Our most important finding is that the predicted structure of GDH2 in the common ancestor of apes was the steppingstone for the structural evolution of primate GDH2s. Two changes with a strong functional impact occurring at the first evolutionary step, Arg443Ser and Gly456Ala, had a destabilizing and stabilizing effect, respectively, making this step the most important one. Subsequently, GDH2 underwent additional modifications that fine-tuned its enzymatic properties to adapt to the functional needs of modern-day primate tissues.

High Hereditary Transthyretin-Related Amyloidosis Prevalence in Crete: Genetic Heterogeneity and Distinct Phenotypes.

Background and Objectives: Our goal was to study hereditary transthyretin-related amyloidosis (hATTR) in Crete, Greece. Methods: We aimed at ascertaining all hATTR cases in Crete, an island of 0.62 million people. For this, we evaluated patients with polyneuropathy, autonomic involvement, cardiomyopathy, and/or ophthalmopathy suggestive of hATTR, who presented to the physicians of this study or were referred to them by other physicians. Genetic analyses were performed on all patients suspected of suffering from hATTR. We included in our observational longitudinal cohort study all individuals, residents of Crete, who, during the study period (1993-2019), were found to carry a pathogenic TTR variant. Results: Over the past 27 years, 30 individuals (15 female patients, 15 male patients), from 12 apparently unrelated families, were diagnosed with hATTR, whereas evaluation of their offspring identified 5 asymptomatic TTR pathogenic variant carriers. The most prevalent TTR variant detected was p.Val50Met, affecting 19 patients (11 female patients, 8 male patients) and causing a rather consistent phenotype characterized by predominant polyneuropathy of early adult onset (median age of symptom onset: 30 years; range: 18-37 years). Specifically, patients affected by the p.Val50Met TTR variant experienced progressive sensorimotor disturbances, involving mainly the lower extremities, associated with autonomic and/or gastrointestinal dysfunction. The second most frequent TTR variant was p.Val114Ala, found in 10 patients (4 female patients, 6 male patients) who were affected at an older age (median age of symptom onset: 70 years; range: 54-78 years). This variant caused a predominantly cardiomyopathic phenotype, manifested by congestive heart failure and associated with peripheral neuropathy, carpal tunnel syndrome, and/or autonomic involvement. In these patients, cardiac amyloid deposition was detected on 99m-technetium pyrophosphate scintigraphy and/or heart biopsy. The third TTR variant (p.Arg54Gly) was found in a 50-year-old male patient with ophthalmopathy due to vitreous opacities and positive family history for visual loss. As 22 patients were alive at the end of the study, we calculated the hATTR prevalence in Crete to be 35 cases per 1 million inhabitants. Discussion: Our study revealed that the prevalence of hATTR in Crete is one of the world's highest. Three different pathogenic TTR variants causing distinct clinical phenotypes were identified in this relatively small population pool.

The p.Pro482Ala Variant in the CNNM2 Gene Causes Severe Hypomagnesemia Amenable to Treatment with Spironolactone.

Renal hypomagnesemia syndromes involving CNNM2 protein pathogenic variants are associated with variable degrees of neurocognitive dysfunction and hypomagnesemia. Here, we report a family with a novel CNNM2 p.Pro482Ala variant, presenting with overt hypomagnesemia and mild neurological involvement (autosomal dominant renal hypomagnesemia 6, HOMG6, MIM# 613882). Using a bioinformatics approach, we showed that the p.Pro482Ala amino acid substitution causes a 3D conformational change in CNNM2 structure in the cystathionin beta synthase (CBS) domain and the carboxy-terminal protein segment. A novel finding was that aldosterone inhibition with spironolactone helped to alleviate hypomagnesemia and symptoms in the proband.

Interactions of Mediterranean Diet, Obesity, Polypharmacy, Depression and Systemic Inflammation with Frailty Status.

Objective:Comprehensive characterization of potential frailty determinants, including sociodemographic, clinical, dietary, psychological, cognitive and systemic inflammation parameters. Methods:A rural cohort of 186 subjects aged 60-89 years recruited from a community-based study in Crete, Greece (the Cretan Aging Cohort). Frailty was assessed with the Simple "Frail" Questionnaire Screening Tool. Results:Univariate analyses revealed significant (a) positive associations (p<0.01) between frailty and age, widowhood, Geriatric Depression Scale (GDS) score, waist circumference, polypharmacy, IL-6 and (b) negative associations between frailty and frequency of contact with friends, Mini Mental State Examination (MMSE), and adherence to the Mediterranean diet. Multivariate analyses revealed a significant independent contribution of the following variables to frailty: age (B=0.035, p<0.001), GDS score (B=0.041, p=0.034), polypharmacy (B=0.568, p<0.001), waist circumference (B=0.015, p=0,006), plasma IL-6 levels (B=0.189, p=0.004), and adherence to the Mediterranean diet (B=-0.036, p=0.015). Conclusion:Older age, depression symptoms, polypharmacy, waist circumference, poor adherence to Mediterranean diet and IL-6 plasma levels are associated with increased frailty.

Dent-2 disease with a Bartter-like phenotype caused by the Asp631Glu mutation in the OCRL gene.

BACKGROUND: Dent disease is an X-linked disorder characterized by low molecular weight proteinuria (LMWP), hypercalciuria, nephrolithiasis and chronic kidney disease (CKD). It is caused by mutations in the chloride voltage-gated channel 5 (CLCN5) gene (Dent disease-1), or in the OCRL gene (Dent disease-2). It is associated with chronic metabolic acidosis; however metabolic alkalosis has rarely been reported. CASE PRESENTATION: We present a family with Dent-2 disease and a Bartter-like phenotype. The main clinical problems observed in the proband included a) primary phosphaturia leading to osteomalacia and stunted growth; b) elevated serum calcitriol levels, leading to hypercalcemia, hypercalciuria, nephrolithiasis and nephrocalcinosis; c) severe salt wasting causing hypotension, hyperaldosteronism, hypokalemia and metabolic alkalosis; d) partial nephrogenic diabetes insipidus attributed to hypercalcemia, hypokalemia and nephrocalcinosis; e) albuminuria, LMWP. Phosphorous repletion resulted in abrupt cessation of hypercalciuria and significant improvement of hypophosphatemia, physical stamina and bone histology. Years later, he presented progressive CKD with nephrotic range proteinuria attributed to focal segmental glomerulosclerosis (FSGS). Targeted genetic analysis for several phosphaturic diseases was unsuccessful. Whole Exome Sequencing (WES) revealed a c.1893C > A variant (Asp631Glu) in the OCRL gene which was co-segregated with the disease in male family members. CONCLUSIONS: We present the clinical characteristics of the Asp631Glu mutation in the OCRL gene, presenting as Dent-2 disease with Bartter-like features. Phosphorous repletion resulted in significant improvement of all clinical features except for progressive CKD. Angiotensin blockade improved proteinuria and stabilized kidney function for several years.

A novel variant in DYNC1H1 could contribute to human amyotrophic lateral sclerosis-frontotemporal dementia spectrum.

Amyotrophic lateral sclerosis (ALS) belongs to the ALS-frontotemporal dementia (FTD) spectrum and is hallmarked by upper and lower motor neuron degeneration. Here, we present a patient with a cytoplasmic dynein 1 heavy chain 1 (DYNC1H1) pathogenic variant who fulfilled the ALS El Escorial criteria, and we review relevant literature. Using whole-exome sequencing, we identified a deleterious point variant in DYNC1H1 (c.4106A > G (p. Q1369R)) as a likely contributor to the ALS phenotype. In silico structural analysis, molecular dynamics simulation, and protein stability analysis predicted that this variant may increase DYNC1H1 protein stability. Moreover, this variant may disrupt binding of the transcription factor TFAP4, thus potentially acting as duon. Because (a) DYNC1H1 forms part of a ubiquitous eukaryotic motor protein complex, and (b) disruption of dynein function by perturbation of the dynein-dynactin protein complex is implicated in other motor neuron degenerative conditions, this variant could disrupt processes like retrograde axonal transport, neuronal migration, and protein recycling. Our findings expand the heterogenous spectrum of the DYNC1H1 pathogenic variant-associated phenotype and prompt further investigations of the role of this gene in ALS.

Variant transthyretin amyloidosis (ATTRv) polyneuropathy in Greece: a broad overview with a focus on non-endemic unexplored regions of the country.

Comprehensive data on variant transthyretin amyloidosis polyneuropathy (ATTRv-PN) in Greece are lacking. We presently provide an overview of ATTRv-PN in Greece, focusing on unexplored non-endemic regions of the country. In total, we identified 57 cases of ATTRv-PN diagnosed over the past 25 years, including 30 from the island of Crete, an apparent endemic region. Patients carried 10 different TTR mutations (C10R; P24S; V30M; R34G; R34T; I68L; A81T; E89Q; E89K and V94A). Carriers of the common V30M mutation constituted 54.3 % of the cohort. A known founder effect for the V30M mutation was present on the island of Crete. Non-endemic cases identified outside the island of Crete are presently reported in more detail. The age of onset ranged from 25 to 77 years, with a mean of 51.1 years. A mean diagnostic delay of 3.2 years was observed. V30M patients had earlier onset and less cardiac involvement than patients carrying other mutations. Genotype-phenotype correlations were largely consistent with published data. We conclude that, with the exception of the Cretan cluster, ATTRv-PN is not endemic in the Greek population. This makes timely diagnosis more challenging, yet absolutely essential given the availability of therapies that can alter the long-term course of the disease.

Crystal structure of glutamate dehydrogenase 2, a positively selected novel human enzyme involved in brain biology and cancer pathophysiology.

INTRODUCTION: Mammalian glutamate dehydrogenase (hGDH1 in human cells) interconverts glutamate to α-ketoglutarate and ammonia while reducing NAD(P) to NAD(P)H. During primate evolution, humans and great apes have acquired hGDH2, an isoenzyme that underwent rapid evolutionary adaptation concomitantly with brain expansion, thereby acquiring unique catalytic and regulatory properties that permitted its function under conditions inhibitory to its ancestor hGDH1. Although the 3D-structures of GDHs, including hGDH1, have been determined, attempts to determine the hGDH2 structure were until recently unsuccessful. Comparison of the hGDH1/hGDH2 structures would enable a detailed understanding of their evolutionary differences. This work aimed at the determination of the hGDH2 crystal structure and the analysis of its functional implications. Recombinant hGDH2 was produced in the Spodoptera frugiperda ovarian cell line Sf21, using the Baculovirus expression system. Purification was achieved via a two-step chromatography procedure. hGDH2 was crystallized, X-ray diffraction data were collected using synchrotron radiation and the structure was determined by molecular replacement. The hGDH2 structure is reported at a resolution of 2.9 Å. The enzyme adopts a novel semi-closed conformation, which is an intermediate between known open and closed GDH1 conformations, differing from both. The structure enabled us to dissect previously reported biochemical findings and to structurally interpret the effects of evolutionary amino acid substitutions, including Arg470His, on ADP affinity. In conclusion, our data provide insights into the structural basis of hGDH2 properties, the functional evolution of hGDH isoenzymes, and open new prospects for drug design, especially for cancer therapeutics.

Objective Daytime Napping is Associated with Disease Severity and Inflammation in Patients with Mild to Moderate Dementia1.

BACKGROUND: Patients with dementia report excessive daytime sleep/sleepiness, which is associated with worse cognitive performance. Inflammatory markers may be elevated in patients with dementia and have been proposed as mediators of sleep/sleepiness. OBJECTIVE: To examine the association of objective daytime napping with cognitive performance and peripheral markers of inflammation in patients with dementia as compared to not cognitively impaired (NCI) controls. METHODS: A sub-sample of 46 patients with mild-to-moderate dementia and 85 NCI controls, were recruited from a large, population-based cohort of 3,140 elders (≥60 years) in Crete, Greece. All participants underwent medical history/physical examination, extensive neuropsychiatric and neuropsychological evaluation, 3-day 24 h actigraphy and a single morning measure of IL-6 and TNFα plasma levels. Comparisons of sleep parameters and inflammation markers between diagnostic groups, and between nappers and non-nappers within each diagnostic group, were conducted using ANCOVA controlling for demographics/related clinical factors. Associations between inflammatory markers, sleep variables, and neuropsychological performance were assessed within each group using partial correlation analysis controlling for confounders. RESULTS: Patients with dementia slept 15 minutes longer during the day than NCI. Within dementia patients, nappers had significantly worse performance on autobiographic memory (p = 0.002), working memory (p = 0.007), episodic memory (p = 0.010), and assessment of daily function (p = 0.012) than non-nappers. Finally, IL-6 levels were significantly associated with nap duration within dementia patients who napped (r = 0.500, p = 0.01). CONCLUSIONS: Daytime napping in patients with dementia is associated with worse cognitive performance and increased IL-6 levels. In dementia, objective daytime napping, may be a marker of the severity of the disease.

Self-reported fatigue as a risk index for dementia diagnosis.

INTRODUCTION: Cognitive impairment and frailty are major problems of older age. This study aims to explore the association between frailty and cognitive impairment in a rural cohort of older subjects in southern Europe (Cretan Aging Cohort). METHODS: Community-based, primary care, cross-sectional, study in the Heraklion Prefecture, Crete, Greece. Four hundred and two persons aged 60-100 years from the Cretan Aging Cohort [100 with dementia, 175 with mild cognitive impairment (MCI) and 127 cognitively non-impaired] were enrolled, mostly rural dwellers (86.2%). Frailty was assessed with the Simple "Frail" Questionnaire Screening Tool. Demographic data, BMI, Mini-Mental State Examination scores (MMSE), severity of dementia according to the Clinical Dementia Rating Scale, and depressive symptoms according to the Geriatric Depression Scale (GDS) were recorded. RESULTS: Frailty was present in 17% of persons with dementia (73.8% of mild severity), in 6.3% of persons with MCI and in 8.7% of cognitively non-impaired persons (P < 0.05). Among the various frailty variables, fatigue and difficulty walking were significantly more frequently reported by persons with dementia. Each frailty variable and the frailty score correlated negatively with MMSE score and positively with GDS score and polypharmacy. Multivariate analysis revealed that reported fatigue improved the identification of dementia in addition to MMSE, significantly and independently of symptoms of depression (P = 0.04). CONCLUSION: Frailty rates are significantly higher in persons with dementia. In this predominantly rural cohort of older subjects, reported fatigue could serve as a marker of physical decline and a complementary index for referral for further neuropsychological and neuropsychiatric evaluation.

The Glutamate Dehydrogenase Pathway and Its Roles in Cell and Tissue Biology in Health and Disease.

Glutamate dehydrogenase (GDH) is a hexameric enzyme that catalyzes the reversible conversion of glutamate to α-ketoglutarate and ammonia while reducing NAD(P)⁺ to NAD(P)H. It is found in all living organisms serving both catabolic and anabolic reactions. In mammalian tissues, oxidative deamination of glutamate via GDH generates α-ketoglutarate, which is metabolized by the Krebs cycle, leading to the synthesis of ATP. In addition, the GDH pathway is linked to diverse cellular processes, including ammonia metabolism, acid-base equilibrium, redox homeostasis (via formation of fumarate), lipid biosynthesis (via oxidative generation of citrate), and lactate production. While most mammals possess a single GDH1 protein (hGDH1 in the human) that is highly expressed in the liver, humans and other primates have acquired, via duplication, an hGDH2 isoenzyme with distinct functional properties and tissue expression profile. The novel hGDH2 underwent rapid evolutionary adaptation, acquiring unique properties that enable enhanced enzyme function under conditions inhibitory to its ancestor hGDH1. These are thought to provide a biological advantage to humans with hGDH2 evolution occurring concomitantly with human brain development. hGDH2 is co-expressed with hGDH1 in human brain, kidney, testis and steroidogenic organs, but not in the liver. In human cerebral cortex, hGDH1 and hGDH2 are expressed in astrocytes, the cells responsible for removing and metabolizing transmitter glutamate, and for supplying neurons with glutamine and lactate. In human testis, hGDH2 (but not hGDH1) is densely expressed in the Sertoli cells, known to provide the spermatids with lactate and other nutrients. In steroid producing cells, hGDH1/2 is thought to generate reducing equivalents (NADPH) in the mitochondria for the biosynthesis of steroidal hormones. Lastly, up-regulation of hGDH1/2 expression occurs in cancer, permitting neoplastic cells to utilize glutamine/glutamate for their growth. In addition, deregulation of hGDH1/2 is implicated in the pathogenesis of several human disorders.

Cerebrovascular events in inflammatory bowel disease patients treated with anti-tumour necrosis factor alpha agents.

BACKGROUND AND AIMS: Cerebrovascular accidents [CVA] have rarely been reported in inflammatory bowel disease [IBD] patients treated with anti-tumour necrosis alpha [anti-TNF alpha] agents. Our aim here was to describe the clinical course of CVA in these patients. METHODS: This was a European Crohn's and Colitis Organisation [ECCO] retrospective observational study, performed as part of the CONFER [COllaborative Network For Exceptionally Rare case reports] project. A call to all ECCO members was made to report on IBD patients afflicted with CVA during treatment with anti-TNF alpha agents. Clinical data were recorded in a standardised case report form and analysed for event association with anti-TNF alpha treatment. RESULTS: A total of 19 patients were identified from 16 centres: 14 had Crohn's disease, four ulcerative colitis and one IBD colitis unclassified [median age at diagnosis: 38.0 years, range: 18.6-62.5]. Patients received anti-TNF alpha for a median duration of 11.8 months [range: 0-62] at CVA onset; seven had previously been treated with at least one other anti-TNF alpha agent. Complete neurological recovery was observed in 16 patients. Anti-TNF alpha was discontinued in 16/19 patients. However, recurrent CVA or neurological deterioration was not observed in any of the 11 patients who received anti-TNF alpha after CVA [eight resumed after temporary cessation, three continued without interruption] for a median follow-up of 39.8 months [range: 5.6-98.2]. CONCLUSION: These preliminary findings do not unequivocally indicate a causal role of anti-TNF alpha in CVA complicating IBD. Resuming or continuing anti-TNF alpha in IBD patients with CVA may be feasible and safe in selected cases, but careful weighing of IBD activity versus neurological status is prudent.

Glutamate dehydrogenase isoforms with N-terminal (His)6- or FLAG-tag retain their kinetic properties and cellular localization.

Glutamate dehydrogenase (GDH) is a crucial enzyme on the crossroads of amino acid and energy metabolism and it is operating in all domains of life. According to current knowledge GDH is present only in one functional isoform in most animals, including mice. In addition to this housekeeping enzyme (hGDH1 in humans), humans and apes have acquired a second isoform (hGDH2) with a distinct tissue expression profile. In the current study we have cloned both mouse and human GDH constructs containing FLAG and (His)6 small genetically-encoded tags, respectively. The hGDH1 and hGDH2 constructs containing N-terminal (His)6 tags were successfully expressed in Sf9 cells and the recombinant proteins were isolated to ≥95 % purity in a two-step procedure involving ammonium sulfate precipitation and Ni(2+)-based immobilized metal ion affinity chromatography. To explore whether the presence of the FLAG and (His)6 tags affects the cellular localization and functionality of the GDH isoforms, we studied the subcellular distribution of the expressed enzymes as well as their regulation by adenosine diphosphate monopotassium salt (ADP) and guanosine-5'-triphosphate sodium salt (GTP). Through immunoblot analysis of the mitochondrial and cytosolic fraction of the HEK cells expressing the recombinant proteins we found that neither FLAG nor (His)6 tag disturbs the mitochondrial localization of GDH. The addition of the small tags to the N-terminus of the mature mitochondrial mouse GDH1 or human hGDH1 and hGDH2 did not change the ADP activation or GTP inhibition pattern of the proteins as compared to their untagged counterparts. However, the addition of FLAG tag to the C-terminus of the mouse GDH left the recombinant protein fivefold less sensitive to ADP activation. This finding highlights the necessity of the functional characterization of recombinant proteins containing even the smallest available tags.

Cultural adaptation, standardization and clinical validity of the test your memory dementia screening instrument in Greek.

BACKGROUND/AIMS: To adapt and standardize the Test Your Memory (TYM) dementia screening instrument in Greek. METHODS: Normative data on the Greek version of the TYM were obtained from a community sample of 239 adults aged 21-92 years. Clinical validity was assessed in a cohort of 134 Neurology Clinic patients. Concurrent validity was examined through comparisons with the Mini-Mental State Examination (MMSE) and the Greek Everyday Function Scale. RESULTS: Correlations between the TYM and the MMSE were 0.73 and 0.82 in the community and patient samples, respectively. Scores on both tests were moderately associated with everyday functional capacity. Using age- and education-corrected cutoff scores ranging from 26/50 to 45/50 points, the sensitivity of the TYM for Alzheimer's disease detection was found to be higher than that of the MMSE (0.82 vs. 0.70), although its specificity was lower (0.71 vs. 0.90). CONCLUSION: Findings are consistent with previous reports in a variety of cultural settings supporting the potential utility of the TYM as a dementia screening tool.

The effect of pH and ADP on ammonia affinity for human glutamate dehydrogenases.

Glutamate dehydrogenase (GDH) uses ammonia to reversibly convert α-ketoglutarate to glutamate using NADP(H) and NAD(H) as cofactors. While GDH in most mammals is encoded by a single GLUD1 gene, humans and other primates have acquired a GLUD2 gene with distinct tissue expression profile. The two human isoenzymes (hGDH1 and hGDH2), though highly homologous, differ markedly in their regulatory properties. Here we obtained hGDH1 and hGDH2 in recombinant form and studied their Km for ammonia in the presence of 1.0 mM ADP. The analyses showed that lowering the pH of the buffer (from 8.0 to 7.0) increased the Km for ammonia substantially (hGDH1: from 12.8 ± 1.4 mM to 57.5 ± 1.6 mM; hGDH2: from 14.7 ± 1.6 mM to 62.2 ± 1.7 mM), thus essentially precluding reductive amination. Moreover, lowering the ADP concentration to 0.1 mM not only increased the K0.5 [NH4 (+)] of hGDH2, but also introduced a positive cooperative binding phenomenon in this isoenzyme. Hence, intra-mitochondrial acidification, as occurring in astrocytes during glutamatergic transmission should favor the oxidative deamination of glutamate. Similar considerations apply to the handling of glutamate by the proximal convoluted tubules of the kidney during systemic acidosis. The reverse could apply for conditions of local or systemic hyperammonemia or alkalosis.

The complex regulation of human glud1 and glud2 glutamate dehydrogenases and its implications in nerve tissue biology.

Mammalian glutamate dehydrogenase (GDH) is a housekeeping mitochondrial enzyme (hGDH1 in the human) that catalyses the reversible inter-conversion of glutamate to α-ketoglutarate and ammonia, thus interconnecting amino acid and carbohydrate metabolism. It displays an energy sensing mechanism, which permits enzyme activation under low cellular energy states. As GDH is at the crossroads of important metabolic pathways, a tight control of its activity is essential. Indeed, to fulfill its role in metabolism and cellular energetics, mammalian GDH has evolved into a highly regulated enzyme subject to allosteric modulation by diverse compounds. The recent emergence (<23 million years ago) in apes and humans of a hGDH2 isoenzyme with distinct regulatory properties, as well as, the detection of gain-of-function variants in hGDH1 and hGDH2 that affect the nervous system, have introduced additional complexities. The properties of the two highly homologous human GDHs were studied using purified recombinant hGDH1 and hGDH2 obtained by expression of the corresponding cDNAs in Sf21 cells. Results showed that, in contrast to hGDH1 that maintains substantial basal activity (35-40% of its maximal capacity), hGDH2 displays low basal activity (3-8% of maximal) that is remarkably responsive to activation by rising levels of ADP and/or l-leucine. This is primarily due to the Arg443Ser evolutionary change, which also made hGDH2 markedly sensitive to estrogens and neuroleptic drugs. In contrast to hGDH1, which is subject to potent GTP inhibition, hGDH2 has dissociated its function from this energy switch, being able to metabolize glutamate even when the Krebs cycle generates GTP levels sufficient to inactivate the housekeeping hGDH1. Our data also show that spermidine, a polyamine thought to reduce oxidative stress and to prolong survival, and EGCG, a green tea polyphenol, inhibit hGDH2 at lower concentrations than hGDH1. The implications of these findings in nerve tissue biology are discussed.

A comparison of acute hemorrhagic stroke outcomes in 2 populations: the Crete-Boston study.

BACKGROUND AND PURPOSE: Although corticosteroid use in acute hemorrhagic stroke is not widely adopted, management with intravenous dexamethasone has been standard of care at the University Hospital of Heraklion, Crete with observed outcomes superior to those reported in the literature. To explore this further, we conducted a retrospective, multivariable-adjusted 2-center study. METHODS: We studied 391 acute hemorrhagic stroke cases admitted to the University Hospital of Heraklion, Crete between January 1997 and July 2010 and compared them with 510 acute hemorrhagic stroke cases admitted to Massachusetts General Hospital, Boston, from January 2003 to September 2009. Of the Cretan cases, 340 received a tapering scheme of intravenous dexamethasone, starting with 16 to 32 mg/day, whereas the Boston patients were managed without steroids. RESULTS: The 2 cohorts had comparable demographics and stroke severity on admission, although anticoagulation was more frequent in Boston. The in-hospital mortality was significantly lower on Crete (23.8%, n=340) than in Boston (38.0%, n=510; P<0.001) as was the 30-day mortality (Crete: 25.4%, n=307; Boston: 39.4%, n=510; P<0.001). Exclusion of patients on anticoagulants showed even greater differences (30-day mortality: Crete 20.8%; n=259; Boston 37.0%; n=359; P<0.001). The improved survival on Crete was observed 3 days after initiation of intravenous dexamethasone and was pronounced for deep-seated hemorrhages. After adjusting for acute hemorrhagic stroke volume/location, Glasgow Coma Scale, hypertension, diabetes mellitus, smoking, coronary artery disease and statin, antiplatelet, and anticoagulant use, intravenous dexamethasone treatment was associated with better functional outcomes and significantly lower risk of death at 30 days (OR, 0.357; 95% CI, 0.174-0.732). CONCLUSIONS: This study suggests that intravenous dexamethasone improves outcome in acute hemorrhagic stroke and supports a randomized clinical trial using this approach.