The gut microbiota modulate locomotion via vagus-dependent glucagon-like peptide-1 signaling.

Locomotor activity is an innate behavior that can be triggered by gut-motivated conditions, such as appetite and metabolic condition. Various nutrient-sensing receptors distributed in the vagal terminal in the gut are crucial for signal transduction from the gut to the brain. The levels of gut hormones are closely associated with the colonization status of the gut microbiota, suggesting a complicated interaction among gut bacteria, gut hormones, and the brain. However, the detailed mechanism underlying gut microbiota-mediated endocrine signaling in the modulation of locomotion is still unclear. Herein, we show that broad-spectrum antibiotic cocktail (ABX)-treated mice displayed hypolocomotion and elevated levels of the gut hormone glucagon-like peptide-1 (GLP-1). Blockade of the GLP-1 receptor and subdiaphragmatic vagal transmission rescued the deficient locomotor phenotype in ABX-treated mice. Activation of the GLP-1 receptor and vagal projecting brain regions led to hypolocomotion. Finally, selective antibiotic treatment dramatically increased serum GLP-1 levels and decreased locomotion. Colonizing Lactobacillus reuteri and Bacteroides thetaiotaomicron in microbiota-deficient mice suppressed GLP-1 levels and restored the hypolocomotor phenotype. Our findings identify a mechanism by which specific gut microbes mediate host motor behavior via the enteroendocrine and vagal-dependent neural pathways.

Butterflies in the gut: the interplay between intestinal microbiota and stress.

Psychological stress is a global issue that affects at least one-third of the population worldwide and increases the risk of numerous psychiatric disorders. Accumulating evidence suggests that the gut and its inhabiting microbes may regulate stress and stress-associated behavioral abnormalities. Hence, the objective of this review is to explore the causal relationships between the gut microbiota, stress, and behavior. Dysbiosis of the microbiome after stress exposure indicated microbial adaption to stressors. Strikingly, the hyperactivated stress signaling found in microbiota-deficient rodents can be normalized by microbiota-based treatments, suggesting that gut microbiota can actively modify the stress response. Microbiota can regulate stress response via intestinal glucocorticoids or autonomic nervous system. Several studies suggest that gut bacteria are involved in the direct modulation of steroid synthesis and metabolism. This review provides recent discoveries on the pathways by which gut microbes affect stress signaling and brain circuits and ultimately impact the host's complex behavior.

Microbial metabolites regulate social novelty via CaMKII neurons in the BNST.

Social novelty is a cognitive process that is essential for animals to interact strategically with conspecifics based on their prior experiences. The commensal microbiome in the gut modulates social behavior through various routes, including microbe-derived metabolite signaling. Short-chain fatty acids (SCFAs), metabolites derived from bacterial fermentation in the gastrointestinal tract, have been previously shown to impact host behavior. Herein, we demonstrate that the delivery of SCFAs directly into the brain disrupts social novelty through distinct neuronal populations. We are the first to observe that infusion of SCFAs into the lateral ventricle disrupted social novelty in microbiome-depleted mice without affecting brain inflammatory responses. The deficit in social novelty can be recapitulated by activating calcium/calmodulin-dependent protein kinase II (CaMKII)-labeled neurons in the bed nucleus of the stria terminalis (BNST). Conversely, chemogenetic silencing of the CaMKII-labeled neurons and pharmacological inhibition of fatty acid oxidation in the BNST reversed the SCFAs-induced deficit in social novelty. Our findings suggest that microbial metabolites impact social novelty through a distinct neuron population in the BNST.

Tight adherent feature on optical coherence tomography predict postoperative visual outcome in epiretinal membrane eyes.

BACKGROUND: To identify the predictive parameter among preoperative measurements that best predicts postoperative visual outcome in the epiretinal membrane (ERM). METHODS: Thirty-three consecutive patients with idiopathic unilateral ERM patients between 2015 and 2018 were enrolled. Nineteen healthy normal eyes were selected as an independent age-matched group. Based on preoperative optical coherence tomography (OCT), we further divided the patients with ERM into two groups: type 1, loosely attached ERM, and type 2, tight adherent ERM. We documented the vision and thickness of various retinal layers: nerve fiber layer, ganglion cell layer, inner plexiform layer (GCL + IPL), inner nuclear layer (INL), outer retinal layer (ORL), and retinal pigment epithelium/Bruch complex layer before and after the surgery. The association between postoperative visual acuity and these variables was analyzed using multiple linear regression analysis. RESULTS: All retinal layers of ERM eyes were thicker than the normal eyes (P < 0.05). Among ERMs, we identified 11 eyes with type 1 adhesions and 22 eyes with type 2 adhesions. The preoperative GCL + IPL layers were significantly thicker in type 2 patients than in type 1 patients (93.67 ± 33.03 um vs 167.71 ± 13.77 um; P = 0.023). Greater GCL + IPL thickness was correlated with a worse postoperative visual acuity and multiple linear regression analysis showed that GCL + IPL thickness was an independent predictor of postoperative visual acuity (VA) (beta value = 0.689; P = 0.012). A greater thickness of GCL + IPL layers of type 2 patients had worse postoperative best-corrected visual acuity (BCVA) (P = 0.028). Ectopic inner foveal layers with disappearance of fovea pit were persistently presented in OCT profiles of both groups. CONCLUSION: Idiopathic ERM demonstrated significantly thicker inner retinal layers (GCL + IPL and INL). However, the ORL thickness was similar between the normal eyes and ERM eyes. The preoperative GCL + IPL layers were significantly thicker in patients with type 2 ERM than that in patients with type 1 ERM. The increase in GCL + IPL thickness was significantly correlated with worse postoperative visual outcomes.

Oral short-chain fatty acids administration regulates innate anxiety in adult microbiome-depleted mice.

Anxiety is characterized by feelings of tension and worry even in the absence of threatening stimulus. Pathological condition of anxiety elicits defensive behavior and aversive reaction ultimately impacting individuals and society. The gut microbiota has been shown to contribute to the modulation of anxiety-like behavior in rodents through the gut-brain axis. Several studies observed that germ-free (GF) and the broad spectrum of antibiotic cocktail (ABX)-treated rodents display lowered anxiety-like behavior. We speculate that gut microbial short-chain fatty acids (SCFA) modulate the innate anxiety response. Herein, we administered SCFA in the drinking water in adult mice treated with ABX to deplete the microbiota and tested their anxiety-like behavior. To further augment the innate fear response, we enhanced the aversive stimulus of the anxiety-like behavior tests. Strikingly, we found that the anxiety-like behavior in ABX mice was not altered when enhanced aversive stimulus, while control and ABX mice supplemented with SCFA displayed increased anxiety-like behavior. Vagus nerve serves as a promising signaling pathway in the gut-brain axis. We determined the role of vagus nerve by subdiaphragmatic vagotomy (SDV) in ABX mice supplemented with SCFA. We found that the restored anxiety-like behavior in ABX mice by SCFA was unaffected by SDV. These findings suggest that gut microbiota can regulate anxiety-like behavior through their fermentation products SCFA.

Elevated α-synuclein and NfL levels in tear fluids and decreased retinal microvascular densities in patients with Parkinson's disease.

The pathognomonic hallmark of Parkinson's disease (PD), α-synuclein, has been observed in the retina of PD patients. We investigated whether biomarkers in the tears and retinal microvascular changes associate with PD risk and progression. This prospective study enrolled 49 PD patients and 45 age-matched healthy controls. The α-synuclein and neurofilament light chain (NfL) levels were measured using an electrochemiluminescence immunoassay. Retinal vessel density was assessed using optical coherence tomography angiography (OCT-A). The Movement Disorder Society-Unified Parkinson's Disease Rating Scale (MDS-UPDRS) and Mini-Mental State Examination score were used to assess motor and cognitive progression. The α-synuclein and NfL levels in the tears were higher in PD patients than in controls (α-synuclein: 55.49 ± 8.12 pg/mL vs. 31.71 ± 3.25 pg/mL, P = 0.009; NfL: 2.89 ± 0.52 pg/mL vs. 1.47 ± 0.23 pg/mL, P = 0.02). The vessel densities in the deep plexus of central macula and the radial peripapillary capillary layer of disc region were lower in PD patients with moderate-stage compared with early-stage PD (P < 0.05). The accuracy of predicting PD occurrence using age and sex alone (area under the curve [AUC] 0.612) was significantly improved by adding α-synuclein and NfL levels and retinal vascular densities (AUC 0.752, P = 0.001). After a mean follow-up of 1.5 ± 0.3 years, the accuracy of predicting motor or cognitive progression using age, sex, and baseline motor severity as a basic model was increased by incorporating retinal microvascular and biofluid markers as a full model (P = 0.001). Our results showed that retinal microvascular densities combined with α-synuclein and NfL levels in tears are associated with risk and progression of PD.

Microbiota regulate social behaviour via stress response neurons in the brain.

Social interactions among animals mediate essential behaviours, including mating, nurturing, and defence1,2. The gut microbiota contribute to social activity in mice3,4, but the gut-brain connections that regulate this complex behaviour and its underlying neural basis are unclear5,6. Here we show that the microbiome modulates neuronal activity in specific brain regions of male mice to regulate canonical stress responses and social behaviours. Social deviation in germ-free and antibiotic-treated mice is associated with elevated levels of the stress hormone corticosterone, which is primarily produced by activation of the hypothalamus-pituitary-adrenal (HPA) axis. Adrenalectomy, antagonism of glucocorticoid receptors, or pharmacological inhibition of corticosterone synthesis effectively corrects social deficits following microbiome depletion. Genetic ablation of glucocorticoid receptors in specific brain regions or chemogenetic inactivation of neurons in the paraventricular nucleus of the hypothalamus that produce corticotrophin-releasing hormone (CRH) reverse social impairments in antibiotic-treated mice. Conversely, specific activation of CRH-expressing neurons in the paraventricular nucleus induces social deficits in mice with a normal microbiome. Via microbiome profiling and in vivo selection, we identify a bacterial species, Enterococcus faecalis, that promotes social activity and reduces corticosterone levels in mice following social stress. These studies suggest that specific gut bacteria can restrain the activation of the HPA axis, and show that the microbiome can affect social behaviours through discrete neuronal circuits that mediate stress responses in the brain.

Clinicopathological and prognostic significance and molecular mechanisms governing uveal melanoma.

Uveal melanoma (UM) is the most common primary intraocular malignancy in adults. Although UM and cutaneous melanoma are derived from melanocytes, UM differs clinically and biologically from its more common skin counterparts. More than half of primary UMs metastasize. However, there is currently no effective treatment for metastatic UM. Therefore, studying mutations related to the metastasis, growth, proliferation, and survival of UM can help researchers understand its pathogenesis and metastatic mechanism, thereby leading to a more effective treatment. In addition, we provide an overview of the recent basic and clinical studies to provide a strong foundation for developing novel anti-carcinogenesis targets for future interventions.

Correlation of pterygium severity with IQ-domain GTPase-activating protein 1 (IQGAP1) and mast cells.

IQ-domain GTPase-activating protein 1 (IQGAP1) is a multidomain scaffold protein that is involved in cytoskeleton dynamics and tumor metastasis. Although the role of IQGAP1 in various cancers had been reported, the function of IQGAP1 in pterygium has not been studied. In this study, surgically excised pterygium and control conjunctival tissue from cataract patients were analysed by immunohistochemistry, confocal microscopy, and Western blot for IQGAP1 expression, mast cell counts, and microvascular count. Pterygium was clinically divided into mild and severe types according to Tan's classification and Kim's criteria based on translucency and vascularity of the tissue. Greater clinical severity of pterygium was associated with higher expression of IQGAP1 expression. Compared to normal conjunctival tissue, severe pterygium had significantly higher IQGAP1 expression (P = 0.005), which strongly correlated to the number of microvessels (P = 0.003) and mast cells (P = 0.01). Confocal microscopy revealed IQGAP1 colocalization with mast cell and CD31. IQGAP1 expression was higher in the pterygium body compared to the head. In conclusion, the level of IQGAP1 expression was found to be correlated to the clinical severity of pterygium. Mast cells were identified in pterygium and is suspected to be involved in promoting fibrovascular invasion.

The Oxidative Stress and Mitochondrial Dysfunction during the Pathogenesis of Diabetic Retinopathy.

Diabetic retinopathy is one of the most serious microvascular complications induced by hyperglycemia via five major pathways, including polyol, hexosamine, protein kinase C, and angiotensin II pathways and the accumulation of advanced glycation end products. The hyperglycemia-induced overproduction of reactive oxygen species (ROS) induces local inflammation, mitochondrial dysfunction, microvascular dysfunction, and cell apoptosis. The accumulation of ROS, local inflammation, and cell death are tightly linked and considerably affect all phases of diabetic retinopathy pathogenesis. Furthermore, microvascular dysfunction induces ischemia and local inflammation, leading to neovascularization, macular edema, and neurodysfunction, ultimately leading to long-term blindness. Therefore, it is crucial to understand and elucidate the detailed mechanisms underlying the development of diabetic retinopathy. In this review, we summarized the existing knowledge about the pathogenesis and current strategies for the treatment of diabetic retinopathy, and we believe this systematization will help and support further research in this area.

Dbo/Henji Modulates Synaptic dPAK to Gate Glutamate Receptor Abundance and Postsynaptic Response.

In response to environmental and physiological changes, the synapse manifests plasticity while simultaneously maintains homeostasis. Here, we analyzed mutant synapses of henji, also known as dbo, at the Drosophila neuromuscular junction (NMJ). In henji mutants, NMJ growth is defective with appearance of satellite boutons. Transmission electron microscopy analysis indicates that the synaptic membrane region is expanded. The postsynaptic density (PSD) houses glutamate receptors GluRIIA and GluRIIB, which have distinct transmission properties. In henji mutants, GluRIIA abundance is upregulated but that of GluRIIB is not. Electrophysiological results also support a GluR compositional shift towards a higher IIA/IIB ratio at henji NMJs. Strikingly, dPAK, a positive regulator for GluRIIA synaptic localization, accumulates at the henji PSD. Reducing the dpak gene dosage suppresses satellite boutons and GluRIIA accumulation at henji NMJs. In addition, dPAK associated with Henji through the Kelch repeats which is the domain essential for Henji localization and function at postsynapses. We propose that Henji acts at postsynapses to restrict both presynaptic bouton growth and postsynaptic GluRIIA abundance by modulating dPAK.

Lovastatin protects neurite degeneration in LRRK2-G2019S parkinsonism through activating the Akt/Nrf pathway and inhibiting GSK3ß activity.

Parkinson's disease (PD) is a progressive neurodegenerative disorder that lacks a disease-modifying therapy. Leucine-rich repeat kinase 2 (LRRK2) was implicated as the most common genetic cause of PD. We previously established a LRRK2-G2019S Drosophila model that displayed the crucial phenotypes of LRRK2 parkinsonism. Here, we used a two-step approach to identify compounds from the FDA-approved licensed drug library that could suppress neurite degeneration in LRRK2-G2019S parkinsonism. Of 640 compounds, 29 rescued neurite degeneration phenotypes and 3 restored motor disability and dopaminergic neuron loss in aged LRRK2-G2019S flies. Of these three drugs, lovastatin had the highest lipophilicity, which facilitated crossing the blood-brain barrier. In LRRK2-G2019S knock-in mice and stably transfected human dopaminergic cells, lovastatin significantly rescued neurite degeneration in a dose-dependent manner, within a range of 0.05-0.1 µm The beneficial effect of lovastatin was exerted by activating anti-apoptotic Akt/Nrf signaling and decreasing caspase 3 levels. We also observed that lovastatin inhibited GSK3ß activity, a kinase downstream of Akt, by up-regulating GSK3ß (Ser9) phosphorylation. This inhibition subsequently decreased tau phosphorylation, which was linked to neuronal cytoskeleton instability. Conversely, pre-treatment with the Akt inhibitor, A6730, blocked the lovastatin-induced neuroprotective effect. The rescuing effects of lovastatin in dendritic arborization of LRRK2-G2019S neurons were abolished by co-expressing either a mutant allele of Akt (Akt104226) or a constitutively active form of GSK3ß (sggS9A). Our findings demonstrated that lovastatin restored LRRK2-G2019S neurite degeneration by augmenting Akt/NRF2 pathway and inhibiting downstream GSK3ß activity, which decreased phospho-tau levels. We suggested that lovastatin is a potential disease-modifying agent for LRRK2-G2019S parkinsonism.

Mutational analysis of FBXO7 gene in Parkinson's disease in a Taiwanese population.

Mutations in the FBXO7 gene cause an autosomal-recessive early-onset parkinsonism with pyramidal tract signs. Its role in typical Parkinson's disease (PD) without pyramidal features is unclear. We assayed FBXO7 gene in 900 participants comprising 448 PD patients and 452 age- and sex-matched control subjects from Taiwan. The entire FBXO7 coding region and intron-exon boundaries were sequenced. We identified 2 novel missense substitutions, p.Ile87Thr and p.Asp328Arg, in a single heterozygous state in 2 early-onset PD patients individually (1.1% early-onset PD). These 2 variants were not observed in control subjects with a total of 904 normal alleles. Additionally, we also found 1 noncoding variant, exon 1 IVS-329C>T, modestly associated with PD. The frequency of the CT/TT genotype was higher in PD patients compared with control subjects (odds ratio, 1.43; 95% confidence interval, 1.02-2.01; p = 0.04). The clinical phenotypes of genetic variant carriers are similar to that seen in idiopathic PD. We conclude that FBXO7 gene contributes little to typical PD in our population. Further studies in other ethnic cohorts will be important to address its potential pathophysiological role in PD.

Nak regulates localization of clathrin sites in higher-order dendrites to promote local dendrite growth.

VIDEO ABSTRACT: During development, dendrites arborize in a field several hundred folds of their soma size, a process regulated by intrinsic transcription program and cell adhesion molecule (CAM)-mediated interaction. However, underlying cellular machineries that govern distal higher-order dendrite extension remain largely unknown. Here, we show that Nak, a clathrin adaptor-associated kinase, promotes higher-order dendrite growth through endocytosis. In nak mutants, both the number and length of higher-order dendrites are reduced, which are phenocopied by disruptions of clathrin-mediated endocytosis. Nak interacts genetically with components of the endocytic pathway, colocalizes with clathrin puncta, and is required for dendritic localization of clathrin puncta. More importantly, these Nak-containing clathrin structures preferentially localize to branching points and dendritic tips that are undergoing active growth. We present evidence that the Drosophila L1-CAM homolog Neuroglian is a relevant cargo of Nak-dependent internalization, suggesting that localized clathrin-mediated endocytosis of CAMs facilitates the extension of nearby higher-order dendrites.

Nak regulates Dlg basal localization in Drosophila salivary gland cells.

Protein trafficking is highly regulated in polarized cells. During development, how the trafficking of cell junctional proteins is regulated for cell specialization is largely unknown. In the maturation of Drosophila larval salivary glands (SGs), the Dlg protein is essential for septate junction formation. We show that Dlg was enriched in the apical membrane domain of proximal cells and localized basolaterally in distal mature cells. The transition of Dlg distribution was disrupted in nak mutants. Nak associated with the AP-2 subunit alpha-Ada and the AP-1 subunit AP-1gamma. In SG cells disrupting AP-1 and AP-2 activities, Dlg was enriched in the apical membrane. Therefore, Nak regulates the transition of Dlg distribution likely through endocytosis of Dlg from the apical membrane domain and transcytosis of Dlg to the basolateral membrane domain during the maturation of SGs development.

Fak56 functions downstream of integrin alphaPS3betanu and suppresses MAPK activation in neuromuscular junction growth.

BACKGROUND: Focal adhesion kinase (FAK) functions in cell migration and signaling through activation of the mitogen-activated protein kinase (MAPK) signaling cascade. Neuronal function of FAK has been suggested to control axonal branching; however, the underlying mechanism in this process is not clear. RESULTS: We have generated mutants for the Drosophila FAK gene, Fak56. Null Fak56 mutants display overgrowth of larval neuromuscular junctions (NMJs). Localization of phospho-FAK and rescue experiments suggest that Fak56 is required in presynapses to restrict NMJ growth. Genetic analyses imply that FAK mediates the signaling pathway of the integrin alphaPS3betanu heterodimer and functions redundantly with Src. At NMJs, Fak56 downregulates ERK activity, as shown by diphospho-ERK accumulation in Fak56 mutants, and suppression of Fak56 mutant NMJ phenotypes by reducing ERK activity. CONCLUSION: We conclude that Fak56 is required to restrict NMJ growth during NMJ development. Fak56 mediates an extracellular signal through the integrin receptor. Unlike its conventional role in activating MAPK/ERK, Fak56 suppresses ERK activation in this process. These results suggest that Fak56 mediates a specific neuronal signaling pathway distinct from that in other cellular processes.