PAR2 promotes impaired glucose uptake and insulin resistance in NAFLD through GLUT2 and Akt interference.

BACKGROUND AND AIMS: Insulin resistance and poor glycemic control are key drivers of the development of NAFLD and have recently been shown to be associated with fibrosis progression in NASH. However, the underlying mechanisms involving dysfunctional glucose metabolism and relationship with NAFLD/NASH progression remain poorly understood. We set out to determine whether protease-activated receptor 2 (PAR2), a sensor of extracellular inflammatory and coagulation proteases, links NAFLD and NASH with liver glucose metabolism. APPROACH AND RESULTS: Here, we demonstrate that hepatic expression of PAR2 increases in patients and mice with diabetes and NAFLD/NASH. Mechanistic studies using whole-body and liver-specific PAR2-knockout mice reveal that hepatic PAR2 plays an unexpected role in suppressing glucose internalization, glycogen storage, and insulin signaling through a bifurcating Gq -dependent mechanism. PAR2 activation downregulates the major glucose transporter of liver, GLUT2, through Gq -MAPK-FoxA3 and inhibits insulin-Akt signaling through Gq -calcium-CaMKK2 pathways. Therapeutic dosing with a liver-homing pepducin, PZ-235, blocked PAR2-Gq signaling and afforded significant improvements in glycemic indices and HbA1c levels in severely diabetic mice. CONCLUSIONS: This work provides evidence that PAR2 is a major regulator of liver glucose homeostasis and a potential target for the treatment of diabetes and NASH.

Lipopeptide Pepducins as Therapeutic Agents.

Pepducins are lipidated peptides that target the intracellular loops of G protein-coupled receptors (GPCRs) in order to modulate transmembrane signaling to internally located effectors. With a wide array of potential activities ranging from partial, biased, or full agonism to antagonism, pepducins represent a versatile class of compounds that can be used to potentially treat diverse human diseases or be employed as novel tools to probe complex mechanisms of receptor activation and signaling in cells and in animals. Here, we describe a number of different pepducins including an advanced compound, PZ-128, that has successfully progressed through phase 2 clinical trials in cardiac patients demonstrating safety and efficacy in suppressing myonecrosis and arterial thrombosis.

Investigating the role of interleukin 10 on Eimeria intestinal pathogenesis in broiler chickens.

Eimeria species are intestinal protozoan parasites that cause lack of production, malabsorption and mortality in floor raised chickens. Administering an oral antibody to interleukin 10 (aIL-10) reduces the symptoms of coccidiosis in broilers, indicating interleukin 10 (IL-10) is key to Eimeria pathology. IL-10 is an anti-inflammatory cytokine and acts as a stand down signal to reduce inflammation and host pathology during disease. Related protozoan parasites exploit IL-10 to reduce pathogen-damaging host inflammatory responses. We hypothesize that IL-10 is increased during Eimeria infection through an unknown host-pathogen interaction, and by feeding aIL-10 to neutralize excess IL-10 the bird is allowed to mount an effective immune response to Eimeria. To determine the effects of aIL-10 during the intestinal immune response, intestinal pathology and the relationship between IL-10, interferon gamma (IFNγ) and Eimeria infection were evaluated in this study. In both experiments, broilers were administered either a 10x dose of Advent® Eimeria vaccine or saline. Duodenum, jejunum and cecum samples were collected, processed, stained and examined under a microscope. Evaluation of intestinal histomorphology during aIL-10 administration showed minimal differences in birds fed aIL-10 during infection compared to animals fed a control antibody during Eimeria infection. To further evaluate aIL-10's positive effect during infection, immunofluorescent histochemistry was performed on chicken intestines days 3-7 post Eimeria infection for IL-10 and IFNγ presence in intestinal mucosa in control and infected birds, in regions with and without visible Eimeria burden. IL-10 and IFNγ had significant changes between days 4.5-7 post-infection in birds fed aIL-10 compared to animals fed a control antibody. Overall we found that the duodenum had increased IL-10 presence and increased IFNγ presence, and the jejunum and cecum had decreased IL-10 presence and decreased IFNγ presence. These differences in spatial regulation of IL-10 and IFNγ may indicate Eimeria species induce slightly different cytokine responses.

Trace amine-associated receptor 1 (TAAR1) promotes anti-diabetic signaling in insulin-secreting cells.

Pancreatic ß-cell failure in type 2 diabetes mellitus is a serious challenge that results in an inability of the pancreas to produce sufficient insulin to properly regulate blood glucose levels. Trace amine-associated receptor 1 (TAAR1) is a G protein-coupled receptor expressed by ß-cells that has recently been proposed as a potential target for improving glycemic control and suppressing binge eating behaviors. We discovered that TAAR1 is coupled to Gαs-signaling pathways in insulin-secreting ß-cells to cause protein kinase A (PKA)/exchange protein activated by cAMP (Epac)-dependent release of insulin, activation of RAF proto-oncogene, Ser/Thr kinase (Raf)-mitogen-activated protein kinase (MAPK) signaling, induction of cAMP response element-binding protein (CREB)-insulin receptor substrate 2 (Irs-2), and increased ß-cell proliferation. Interestingly, TAAR1 triggered cAMP-mediated calcium influx and release from internal stores, both of which were required for activation of a MAPK cascade utilizing calmodulin-dependent protein kinase II (CaMKII), Raf, and MAPK/ERK kinase 1/2 (MEK1/2). Together, these data identify TAAR1/Gαs-mediated signaling pathways that promote insulin secretion, improved ß-cell function and proliferation, and highlight TAAR1 as a promising new target for improving ß-cell health in type 2 diabetes mellitus.

Mechanisms underlying stage-1 TRPL channel translocation in Drosophila photoreceptors.

BACKGROUND: TRP channels function as key mediators of sensory transduction and other cellular signaling pathways. In Drosophila, TRP and TRPL are the light-activated channels in photoreceptors. While TRP is statically localized in the signaling compartment of the cell (the rhabdomere), TRPL localization is regulated by light. TRPL channels translocate out of the rhabdomere in two distinct stages, returning to the rhabdomere with dark-incubation. Translocation of TRPL channels regulates their availability, and thereby the gain of the signal. Little, however, is known about the mechanisms underlying this trafficking of TRPL channels. METHODOLOGY/PRINCIPAL FINDINGS: We first examine the involvement of de novo protein synthesis in TRPL translocation. We feed flies cycloheximide, verify inhibition of protein synthesis, and test for TRPL translocation in photoreceptors. We find that protein synthesis is not involved in either stage of TRPL translocation out of the rhabdomere, but that re-localization to the rhabdomere from stage-1, but not stage-2, depends on protein synthesis. We also characterize an ex vivo eye preparation that is amenable to biochemical and genetic manipulation. We use this preparation to examine mechanisms of stage-1 TRPL translocation. We find that stage-1 translocation is: induced with ATP depletion, unaltered with perturbation of the actin cytoskeleton or inhibition of endocytosis, and slowed with increased membrane sterol content. CONCLUSIONS/SIGNIFICANCE: Our results indicate that translocation of TRPL out of the rhabdomere is likely due to protein transport, and not degradation/re-synthesis. Re-localization from each stage to the rhabdomere likely involves different strategies. Since TRPL channels can translocate to stage-1 in the absence of ATP, with no major requirement of the cytoskeleton, we suggest that stage-1 translocation involves simple diffusion through the apical membrane, which may be regulated by release of a light-dependent anchor in the rhabdomere.

TNF-alpha-dependent regulation of acute pancreatitis severity by Ly-6C(hi) monocytes in mice.

The roles of monocytes/macrophages and their mechanisms of action in the regulation of pancreatitis are poorly understood. To address these issues, we have employed genetically altered mouse strains that either express the human diphtheria toxin receptor (DTR) coupled to the CD11b promoter or have global deletion of TNF-α. Targeted, conditional depletion of monocytes/macrophages was achieved by administration of diphtheria toxin (DT) to CD11b-DTR mice. We show that in the absence of DT administration, pancreatitis is associated with an increase in pancreatic content of Ly-6C(hi) monocytes/macrophages but that this response is prevented by prior administration of DT to CD11b-DTR mice. DT administration also reduces pancreatic edema and acinar cell injury/necrosis in two dissimilar experimental models of acute pancreatitis (a secretagogue-induced model and a model elicited by retrograde pancreatic duct infusion of sodium taurocholate). In the secretagogue-elicited model, the DT-induced decrease in pancreatitis severity is reversed by adoptive transfer of purified Ly-6C(hi) monocytes harvested from non-DT-treated CD11b-DTR mice or by the transfer of purified Ly-6C(hi) monocytes harvested from TNF-α(+/+) donor mice, but it is not reversed by the transfer of Ly-6C(hi) monocytes harvested from TNF-α(-/-) donors. Our studies indicate that the Ly-6C(hi) monocyte subset regulates the severity of pancreatitis by promoting pancreatic edema and acinar cell injury/necrosis and that this phenomenon is dependent upon the expression of TNF-α by those cells. They suggest that therapies targeting Ly-6C(hi) monocytes and/or TNF-α expression by Ly-6C(hi) monocytes might prove beneficial in the prevention or treatment of acute pancreatitis.

Subcortical differences among youths with attention-deficit/hyperactivity disorder compared to those with bipolar disorder with and without attention-deficit/hyperactivity disorder.

INTRODUCTION: A significant number of children with bipolar disorder (BP) have co-morbid attention-deficit/hyperactivity disorder (ADHD). It is unknown if these children have neuroimaging findings unique to their co-morbid presentation, or if their brain findings are similar to children diagnosed with BP alone. METHOD: Fifty three children with Diagnostic and Statistical Manual of Mental Disorders, 4(th) edition (DSM-IV) BP (23 with ADHD, 30 without), 29 healthy controls (HC), and 23 children with ADHD, similar in sex and age, had magnetic resonance imaging (MRI) scans on a 1.5T GE scanner. Volumetric assessments were performed for basal ganglia and limbic subcortical structures. RESULTS: Youths with ADHD had smaller caudate and putamen volumes compared to both BP groups and they had moderately smaller total amygdala volumes compared to the other three groups. Youths with BP + ADHD had moderately larger nucleus accumbens volumes than HC, and females in both BP groups had smaller hippocampal volumes compared to ADHD and HC. No differences were found between the BP and BP + ADHD groups. CONCLUSION: These data suggest that morphometric subcortical volumes in youths with BP + ADHD are more similar to those in youths with BP. They do not share subcortical neuroanatomic correlates with the ADHD group. These findings suggest that BP + ADHD is a subtype of pediatric BP rather than severe ADHD.

Double-blind comparison of first- and second-generation antipsychotics in early-onset schizophrenia and schizo-affective disorder: findings from the treatment of early-onset schizophrenia spectrum disorders (TEOSS) study.

OBJECTIVE: Atypical (second-generation) antipsychotics are considered standard treatment for children and adolescents with early-onset schizophrenia and schizoaffective disorder. However, the superiority of second-generation antipsychotics over first-generation antipsychotics has not been demonstrated. This study compared the efficacy and safety of two second-generation antipsychotics (olanzapine and risperidone) with a first-generation antipsychotic (molindone) in the treatment of early-onset schizophrenia and schizoaffective disorder. METHOD: This double-blind multisite trial randomly assigned pediatric patients with early-onset schizophrenia and schizoaffective disorder to treatment with either olanzapine (2.5-20 mg/day), risperidone (0.5-6 mg/day), or molindone (10-140 mg/day, plus 1 mg/day of benztropine) for 8 weeks. The primary outcome was response to treatment, defined as a Clinical Global Impression (CGI) improvement score of 1 or 2 and >or=20% reduction in Positive and Negative Syndrome Scale (PANSS) total score after 8 weeks of treatment. RESULTS: In total, 119 youth were randomly assigned to treatment. Of these subjects, 116 received at least one dose of treatment and thus were available for analysis. No significant differences were found among treatment groups in response rates (molindone: 50%; olanzapine: 34%; risperidone: 46%) or magnitude of symptom reduction. Olanzapine and risperidone were associated with significantly greater weight gain. Olanzapine showed the greatest risk of weight gain and significant increases in fasting cholesterol, low density lipoprotein, insulin, and liver transaminase levels. Molindone led to more self-reports of akathisia. CONCLUSIONS: Risperidone and olanzapine did not demonstrate superior efficacy over molindone for treating early-onset schizophrenia and schizoaffective disorder. Adverse effects were frequent but differed among medications. The results question the nearly exclusive use of second-generation antipsychotics to treat early-onset schizophrenia and schizoaffective disorder. The safety findings related to weight gain and metabolic problems raise important public health concerns, given the widespread use of second-generation antipsychotics in youth for nonpsychotic disorders.