Cortical and Striatal Circuits in Huntington's Disease

Huntington's disease (HD) is a hereditary neurodegenerative disorder that typically manifests in midlife with motor, cognitive, and/or psychiatric symptoms. The disease is caused by a CAG triplet expansion in exon 1 of the huntingtin gene and leads to a severe neurodegeneration in the striatum and cortex. Classical electrophysiological studies in genetic HD mouse models provided important insights into the disbalance of excitatory, inhibitory and neuromodulatory inputs, as well as progressive disconnection between the cortex and striatum. However, the involvement of local cortical and striatal microcircuits still remains largely unexplored. Here we review the progress in understanding HD-related impairments in the cortical and basal ganglia circuits, and outline new opportunities that have opened with the development of modern circuit analysis methods. In particular, in vivo imaging studies in mouse HD models have demonstrated early structural and functional disturbances within the cortical network, and optogenetic manipulations of striatal cell types have started uncovering the causal roles of certain neuronal populations in disease pathogenesis. In addition, the important contribution of astrocytes to HD-related circuit defects has recently been recognized. In parallel, unbiased systems biology studies are providing insights into the possible molecular underpinnings of these functional defects at the level of synaptic signaling and neurotransmitter metabolism. With these approaches, we can now reach a deeper understanding of circuit-based HD mechanisms, which will be crucial for the development of effective and targeted therapeutic strategies

Alkoholi liigtarvitavate patsientide lühinõustamise tulemuslikkus Eesti perearstikeskustes: prospektiivne uuring

http://www.ester.ee/record=b4682183*es

Cortical circuit alterations precede motor impairments in Huntington's disease mice

Huntington's disease (HD) is a devastating hereditary movement disorder, characterized by degeneration of neurons in the striatum and cortex. Studies in human patients and mouse HD models suggest that disturbances of neuronal function in the neocortex play an important role in disease onset and progression. However, the precise nature and time course of cortical alterations in HD have remained elusive. Here, we use chronic in vivo two-photon calcium imaging to longitudinally monitor the activity of identified single neurons in layer 2/3 of the primary motor cortex in awake, behaving R6/2 transgenic HD mice and wildtype littermates. R6/2 mice show age-dependent changes in cortical network function, with an increase in activity that affects a large fraction of cells and occurs rather abruptly within one week, preceeding the onset of motor defects. Furthermore, quantitative proteomics demonstrate a pronounced downregulation of synaptic proteins in the cortex, and histological analyses in R6/2 mice and human HD autopsy cases reveal a reduction in perisomatic inhibitory synaptic contacts on layer 2/3 pyramidal cells. Taken together, our study provides a time-resolved description of cortical network dysfunction in behaving HD mice and points to disturbed excitation/inhibition balance as an important pathomechanism in HD

Intrahepatic cholestasis in nonalcoholic fatty liver disease

Aim. to determine the frequency of intrahepatic cholestasis and its impact on the clinical features of the different forms of non-alcoholic fatty liver disease (NAFLD). Materials and methods. The study involved 163 patients with NAFLD: 92 (56.4%) with hepatic steatosis (HS), 56 (34.4%) with steatohepatitis (SH) and 15 (9.2%) with liver cirrhosis (LC). Diagnosis is based on clinical, laboratory, ultrasound and histological data. Insulin, tumor necrosis factor α (TNF-α), fragments of cytokeratin-18 (FCK-18) were determined by ELISA. The index of insulin resistance (HOMA-IR) was calculated. NAFLD fibrosis score (NAFLD-FS) was determined, taking into account the patient's age, body mass index, presence or absence of carbohydrate metabolism disturbances, levels of ASAT, ALAT, albumin and blood platelets. Results. Cholestatic syndrome was detected in 49 (30.1%) NAFLD patients: in 23 (25%) with HS, in 19 (33.9%) with SH and in 7 (46.7%) with LC. Patients with HS, SH and LC with signs of cholestasis as compared to patients with the same forms of NAFLD without cholestasis had significantly higher levels of the following indicators: aminotransferases, triglycerides, HOMA-IR, TNF-α, FCK-18, NAFLD-FS, - the number of platelets is reduced, indirectly confirming the more rapid development of fibrosis in cholestasis. These findings were consistent with published data on the violation in cholestasis regulatory functions of bile acids, which are ligands of hepatocyte nuclear receptor, responsible for normal homeostasis. Сonclusion. In all forms of NAFLD with cholestasis were detected more pronounced liver cell inflammation, hepatocyte necrosis and apoptosis, fibrosis, disturbance of carbohydrate and lipid metabolism, which contributed to a progressive course of NAFLD and confirmed the need for medical correction of cholestasis, starting with the earliest form of NAFLD - hepatosteatosis

Alkoholi tarvitamise muutused lühinõustamise järel ja seos elukvaliteediga perearsti poole pöördunud patsientide hulgas

Taust ja eesmärk. On teada, et lühinõustamisel on positiivne mõju patsientide alkoholitarvitamise harjumustele. Töö eesmärk oli hinnata alkoholitarvitamise ja tervisega seotud elukvaliteedi hinnangute muutusi perearstikeskuses teostatud lühinõustamine järel alkoholi liigtarvitavate patsientide hulgas.Metoodika. 12 kuu pikkuses prospektiivses uuringus osales 93 alkoholi liigtarvitavat ja lühinõustamist saanud uuritavat. Uuritavate alkoholitarvitamist mõõdeti AUDITi (Alcohol Use Disorders Identification Test) küsimustiku ning tervisega seotud elukvaliteedi SF-36 küsimustiku abil enne lühinõustamist ja 12 kuud hiljem. AUDITi skoori ja tervisega seotud elukvaliteedi muutuste seoseid hinnati lineaarse regressiooni abil.Tulemused. Aasta hiljem kordusvisiidil mõõdetud tulemustest selgus, et 81,7%-l uuritavatest oli võrreldes nõustamiseelse hindamisega AUDITi skoor oluliselt vähenenud (12,3 ± 0,5 kuni 7,5 ± 0,5 punkti; p < 0,001). Nende kehalist tervist kirjeldavate komponentide üldskoor suurenes keskmiselt 7,8 punkti võrra (68,3 ± 2,5 kuni 76,1 ± 2,0; p < 0,05), vaimset tervist kirjeldavate komponentide üldskoor suurenes keskmiselt 5,7 punkti võrra (68,2 ± 2,5 kuni 73,9 ± 2,0; p = 0,068). AUDITi skoori vähenemine seostus kehalise tervise komponentide üldskoori suurenemisega, kuid ei seostunud vaimse tervise komponentide üldskoori muutusega.Järeldused. Alkoholitarvitamise vähenemine lühinõustamise järel on seotud patsiendi enda hinnatud tervisega seotud elukvaliteedi kehalist tervist kirjeldavate komponentide üldskoori suurenemisega.Eesti Arst 2016; 95(10):628–63

Genetic targeting of NRXN2 in mice unveils role in excitatory cortical synapse function and social behaviors

Human genetics has identified rare copy number variations and deleterious mutations for all neurexin genes (NRXN1-3) in patients with neurodevelopmental diseases, and electrophysiological recordings in animal brains have shown that Nrxns are important for synaptic transmission. While several mouse models for Nrxn1α inactivation have previously been studied for behavioral changes, very little information is available for other variants. Here, we validate that mice lacking Nrxn2α exhibit behavioral abnormalities, characterized by social interaction deficits and increased anxiety-like behavior, which partially overlap, partially differ from Nrxn1α mutant behaviors. Using patch-clamp recordings in Nrxn2α knockout brains, we observe reduced spontaneous transmitter release at excitatory synapses in the neocortex. We also analyse at this cellular level a novel NRXN2 mouse model that carries a combined deletion of Nrxn2α and Nrxn2β. Electrophysiological analysis of this Nrxn2-mutant mouse shows surprisingly similar defects of excitatory release to Nrxn2α, indicating that the β-variant of Nrxn2 has no strong function in basic transmission at these synapses. Inhibitory transmission as well as synapse densities and ultrastructure remain unchanged in the neocortex of both models. Furthermore, at Nrxn2α and Nrxn2-mutant excitatory synapses we find an altered facilitation and N-methyl-D-aspartate receptor (NMDAR) function because NMDAR-dependent decay time and NMDAR-mediated responses are reduced. As Nrxn can indirectly be linked to NMDAR via neuroligin and PSD-95, the trans-synaptic nature of this complex may help to explain occurrence of presynaptic and postsynaptic effects. Since excitatory/inhibitory imbalances and impairment of NMDAR function are alledged to have a role in autism and schizophrenia, our results support the idea of a related pathomechanism in these disorders

The clinical significance of insulin resistance in non-diabetic patients with early forms of non-alcoholic fatty liver disease

Aim. To assess the presence of insulin resistance (IR) in non-diabetic patients with early forms of non-alcoholic fatty liver disease (NAFLD) - liver steatosis (LS) and steatohepatitis (SH) of mild activity and the influence of IR on the clinical course of these diseases. Materials and methods. 134 patients with NAFLD were examined: 54 with LS and 80 with SH. The control group consisted of 37 healthy donors. Anthropometric parameters (body mass index (BMI), waist circumference (WC)), clinical and biochemical blood indices, including the blood level of cytokeratin-18 fragments (CK-18), TNF-α and IL-6 cytokines, insulin were evaluated. The HOMA index and the fibrosis index (NAFLD FS) were calculated. Patients were divided into groups: I - with the absence of IR (HOMA-index 2.7). Results and discussion. Indicators of hepatic injury, inflammation, cholestasis, fibrosis and atherogenic dyslipidemia are higher in patients with LS of group II (with IR) than in group I patients (without IR). BMI, WC, γ-glutamil transpeptidase, CK-18 and fibrosis index are significantly higher in group II patients with SH compared with group I, there is no significant difference in the level of cytolysis, inflammation and dyslipidemia indices. A high incidence of IR in non-diabetic patients with LS (37.0%) and SH (55.0%) was found and the effect of IR on the clinical course of these diseases was revealed. Conclusion. Insulin resistance in non-diabetic patients with NAFLD was detected in SH (55.0%) with higher frequency than in LS (37.0%). In LS, IR is associated with impaired hepatic cell damage, intrahepatic cholestasis, atherogenic dyslipidemia and fibrosis. In SH, IR is combined with reliable growth in indicators of hepatocyte apoptosis, cytokine proinflammatory status and fibrosis. IR determines the progressing course of NAFLD, promoting the transformation of steatosis into steatohepatitis and steatohepatitis into fibrosis and liver cirrhosis

The extracellular chaperone Clusterin enhances Tau aggregate seeding in a cellular model

Variants of the extracellular chaperone Clusterin are associated with Alzheimer's disease (AD) and Clusterin levels are elevated in AD patient brains. Here, the authors show that Clusterin binds to oligomeric Tau, which enhances the seeding capacity of Tau aggregates upon cellular uptake. They also demonstrate that Tau/Clusterin complexes enter cells via the endosomal pathway, resulting in damage to endolysosomes and entry into the cytosol, where they induce the aggregation of endogenous, soluble Tau. Spreading of aggregate pathology across brain regions acts as a driver of disease progression in Tau-related neurodegeneration, including Alzheimer's disease (AD) and frontotemporal dementia. Aggregate seeds released from affected cells are internalized by naive cells and induce the prion-like templating of soluble Tau into neurotoxic aggregates. Here we show in a cellular model system and in neurons that Clusterin, an abundant extracellular chaperone, strongly enhances Tau aggregate seeding. Upon interaction with Tau aggregates, Clusterin stabilizes highly potent, soluble seed species. Tau/Clusterin complexes enter recipient cells via endocytosis and compromise the endolysosomal compartment, allowing transfer to the cytosol where they propagate aggregation of endogenous Tau. Thus, upregulation of Clusterin, as observed in AD patients, may enhance Tau seeding and possibly accelerate the spreading of Tau pathology

The extracellular chaperone Clusterin enhances Tau aggregate seeding in a cellular model

Spreading of aggregate pathology across brain regions acts as a driver of disease progression in Tau-related neurodegeneration, including Alzheimer’s disease (AD) and frontotemporal dementia. Aggregate seeds released from affected cells are internalized by naïve cells and induce the prion-like templating of soluble Tau into neurotoxic aggregates. Here we show in a cellular model system and in neurons that Clusterin, an abundant extracellular chaperone, strongly enhances Tau aggregate seeding. Upon interaction with Tau aggregates, Clusterin stabilizes highly potent, soluble seed species. Tau/Clusterin complexes enter recipient cells via endocytosis and compromise the endolysosomal compartment, allowing transfer to the cytosol where they propagate aggregation of endogenous Tau. Thus, upregulation of Clusterin, as observed in AD patients, may enhance Tau seeding and possibly accelerate the spreading of Tau pathology