Search

Aim: Postprandial secretion of the appetite-inhibiting hormones, glucagon-like peptide-1 (GLP-1), and peptide YY are reduced with obesity. It is unclear if the reduced secretion persists following weight loss (WL), if other appetite-inhibiting hormones are also reduced, and if so whether reduced secretion results from intrinsic changes in the gut. Methods: To address whether WL may restore secretion of GLP-1 and other appetite-inhibiting hormones, we performed a gut perfusion study of the small intestine in diet-induced obese (DIO) rats after WL. A 20% weight loss (means ± SEM (g): 916 ± 53 vs. 703 ± 35, p < 0.01, n = 7) was induced by calorie restriction, and maintained stable for ≥7 days prior to gut perfusion to allow for complete renewal of enteroendocrine cells. Age-matched DIO rats were used as comparator. Several gut hormones were analyzed from the venous effluent, and gene expression was performed on gut tissue along the entire length of the intestine. Results: Secretion of cholecystokinin, gastrin, glucose-dependent insulinotropic peptide, GLP-1, neurotensin, and somatostatin was not affected by WL during basal conditions (p ≥ 0.25) or in response to macronutrients and bile acids (p ≥ 0.14). Glucose absorption was indistinguishable following WL. The expression of genes encoding the studied peptides, macronutrient transporters (glucose, fructose, and di-/tripeptides) and bile acid receptors did also not differ between DIO and WL groups. Conclusions: These data suggest that the attenuated postprandial responses of GLP-1, as well as reduced responses of other appetite-inhibiting gut hormones, in people living with obesity may persist after weight loss and may contribute to their susceptibility for weight regain.

Objective Dietary fibres are essential for maintaining microbial diversity and the gut microbiota can modulate host physiology by metabolising the fibres. Here, we investigated whether the soluble dietary fibre oligofructose improves host metabolism by modulating bacterial transformation of secondary bile acids in mice fed western-style diet. Design To assess the impact of dietary fibre supplementation on bile acid transformation by gut bacteria, we fed conventional wild-type and TGR5 knockout mice western-style diet enriched or not with cellulose or oligofructose. In addition, we used germ-free mice and in vitro cultures to evaluate the activity of bacteria to transform bile acids in the caecal content of mice fed with western-style diet enriched with oligofructose. Finally, we treated wild-type and TGR5 knockout mice orally with hyodeoxycholic acid to assess its antidiabetic effects. Results We show that oligofructose sustains the production of 6α-hydroxylated bile acids from primary bile acids by gut bacteria when fed western-style diet. Mechanistically, we demonstrated that the effects of oligofructose on 6α-hydroxylated bile acids were microbiota dependent and specifically required functional TGR5 signalling to reduce body weight gain and improve glucose metabolism. Furthermore, we show that the 6α-hydroxylated bile acid hyodeoxycholic acid stimulates TGR5 signalling, in vitro and in vivo, and increases GLP-1R activity to improve host glucose metabolism. Conclusion Modulation of the gut microbiota with oligofructose enriches bacteria involved in 6α-hydroxylated bile acid production and leads to TGR5-GLP1R axis activation to improve body weight and metabolism under western-style diet feeding in mice., Gut, 72 (2), ISSN:1468-3288, ISSN:0017-5749

Peptic ulcer disease is a frequent clinical problem with potentially serious complications such as bleeding or perforation. A decisive factor in the pathogenesis of peptic ulcers is gastric acid, the secretion of which is controlled by the hormone gastrin released from gastric G cells. However, the molecular mechanisms regulating gastrin plasma concentrations are poorly understood. Here, we identified a semaphorin-plexin signaling pathway that operates in gastric G cells to inhibit gastrin expression on a transcriptional level, thereby limiting food-stimulated gastrin release and gastric acid secretion. Using a systematic siRNA screening approach combined with biochemical, cell biology, and in vivo mouse experiments, we found that the RasGAP protein Rasal1 is a central mediator of plexin signal transduction, which suppresses gastrin expression through inactivation of the small GTPase R-Ras. Moreover, we show that Rasal1 is pathophysiologically relevant for the pathogenesis of peptic ulcers induced by nonsteroidal anti-inflammatory drugs (NSAIDs), a main risk factor of peptic ulcers in humans. Last, we show that application of recombinant semaphorin 4D alleviates peptic ulcer disease in mice in vivo, demonstrating that this signaling pathway can be harnessed pharmacologically. This study unravels a mode of G cell regulation that is functionally important in gastric homeostasis and disease.

Objectives: Pre-clinical evaluation of drug efficacy on weight loss is usually done in diet-induced obese (DIO) mice housed at room temperature (∼22°C) , where the mice display adaptive thermogenic responses through brown adipose tissue (BAT) activation to increase energy expenditure (EE) and maintain core-temperature. These adaptive responses may influence drug-induced weight loss and ultimately likelihood for translatability to humans, who does not have thermogenic responses at room-temperature. We tested whether the efficacy of diverse weight-reducing pharmaco-therapies with distinct mode of action is impacted by housing temperature. Methods: Male DIO mice were studied with indirect calorimetry (Sable Systems International) at 22°C or 30°C (thermoneutrality) . Mice were treated daily for 10-21 days with analogues of weight-modulating compounds that have been in clinical development: glucagon-like peptide-1 (GLP-1) , melanocortin-4-receptor (MC4R) agonist, growth differentiation factor 15 (GDF15) , peptide YY (PYY) , and fibroblast growth factor 21 (FGF21) aiming for a weight loss (WL) of 10-25%. Results: Energy expenditure was ∼30% higher 22°C compared to 30°C. Housing temperature did not affect GLP-1 (∼20%) and MC4R (∼10%) mediated WL. However, FGF21 and PYY-mediated WL was higher at 30°C (∼20% vs. ∼17% for FGF21 and ∼9% vs. ∼1% for PYY) . In contrast, GDF15-mediated WL was higher at 22°C (∼14% vs. ∼8%) . The relative contribution of inhibition of food intake vs. increase in EE differed for FGF21 but not for the other compounds. In this case, increased EE, by BAT, drove more of the weight loss in the 22°C group. Conclusion: Ambient temperature may affect both efficacy and mode of action of weight-reducing pharmaco-therapies in DIO mice. This may affect human translatability, and we, therefore, suggest that studies at thermoneutrality should be included at an early stage in drug-development programs. Disclosure N. Petersen: Employee; Novo Nordisk A/S. B. Ø. Christoffersen: Employee; Novo Nordisk A/S, Stock/Shareholder; Novo Nordisk A/S. L. M. John: None. R. E. Kuhre: Employee; Novo Nordisk. L. Torz: Other Relationship; Novo Nordisk A/S. M. K. Gerstenberg: Employee; Novo Nordisk. K. Pedersen: Employee; Novo Nordisk A/S. S. H. Madsen: None. S. Østergaard: Employee; Novo Nordisk A/S. B. S. Wulff: Employee; Novo Nordisk A/S. S. B. Jørgensen: Employee; Novo Nordisk A/S. B. S. Andersen: Employee; Novo Nordisk A/S. Funding Novo Nordisk A/S

Weight loss and regain are associated with profound cytoskeleton changes in collapsing and re-expanding adipocytes. These drastic changes in the adipose tissue may drive proinflammatory signalling and fibrotic processes during weight regain. It remains unclear how adipose tissue re-expansion affects adipose tissue function and thereby the comorbidities related to obesity. The aim of this study was to characterize structural and metabolic changes in subcutaneous adipose tissue after weight loss and regain in diet-induced obesity (DIO) mice. DIO mice underwent calorie restriction to achieve a 25% weight loss and then returned to ad libitum high fat diet feeding to regain weight. Inguinal adipose tissue was collected and analysed from five groups of mice during the experiment: before high fat diet feeding (Lean) , before weight loss (DIO 1) , after weight loss (WL) , after 3 weeks of weight regain (WR) and age-matched ad libitum DIO mice (DIO 2) . We found that WR group had lower weight and fat mass compared to DIO2 group (31.9±1.6 vs. 23.9±1.9 %) and lower basal lipolysis measured ex-vivo. We detected a larger population of small adipocytes in WR mice compared to DIO2 group, resulting in smaller average adipocyte size (81.6±1.4 vs. 52.5±0.9 µm) and increased expression of cell renewal markers Cidea, Antrx1 and Prkaa in adipose tissue, indicating activation of adipogenesis. Expression of cytokines Il2, Ccl19, Cdc3 in adipose tissue in WR compared to DIO was reduced as well as plasma levels of cytokines Il2, KC/GRO and Inf-γ. In conclusion, our study does not support that increased adipogenesis in weight regain results in accelerated fat accumulation in mice. Weight regain is accompanied by reduced systemic and adipose inflammation. This suggests in general a beneficial effect of regain-induced adipogenesis resulting in potentially healthier adipose tissue in mice. Weather these findings represent the human situation with weight loss and regain is unknown and is currently under investigation. Disclosure M. K. Gerstenberg: Employee; Novo Nordisk. R. E. Kuhre: Employee; Novo Nordisk. N. Petersen: Employee; Novo Nordisk A/S. A. Bookout: Employee; Novo Nordisk. C. M. Castorena: Employee; Novo Nordisk. L. Torz: Other Relationship; Novo Nordisk A/S. T. H. Dovmark: None. S. Lundh: Employee; Novo Nordisk A/S. S. H. Madsen: None. B. S. Andersen: Employee; Novo Nordisk A/S. T. A. Pedersen: Employee; Novo Nordisk A/S, Stock/Shareholder; Novo Nordisk A/S.

There has been a lack of research systematically identifying the kinds of international students who struggle to succeed academically in the New Zealand tertiary context. This research was conducte...

Obesity is caused by prolonged energy surplus. Current anti-obesity medications are mostly centralized around the energy input part of the energy balance equation by increasing satiety and reducing appetite. Our gastrointestinal tract is a key organ for regulation of food intake and supplies a tremendous number of circulating signals that modulate the activity of appetite-regulating areas of the brain by either direct interaction or through the vagus nerve. Intestinally derived messengers are manifold and include absorbed nutrients, microbial metabolites, gut hormones and other enterokines, collectively comprising a fine-tuned signalling system to the brain. After a meal, nutrients directly interact with appetite-inhibiting areas of the brain and induce satiety. However, overall feeding behaviour also depends on secretion of gut hormones produced by highly specialized and sensitive enteroendocrine cells. Moreover, circulating microbial metabolites and their interactions with enteroendocrine cells further contribute to the regulation of feeding patterns. Current therapies exploiting the appetite-regulating properties of the gut are based on chemically modified versions of the gut hormone, glucagon-like peptide-1 (GLP-1) or on inhibitors of the primary GLP-1 inactivating enzyme, dipeptidyl peptidase-4 (DPP-4). The effectiveness of these approaches shows that that the gut is a promising target for therapeutic interventions to achieve significant weigh loss. We believe that increasing understanding of the functionality of the intestinal epithelium and new delivery systems will help develop selective and safe gut-based therapeutic strategies for improved obesity treatment in the future. Here, we provide an overview of the major homeostatic appetite-regulating signals generated by the intestinal epithelial cells and how these signals may be harnessed to treat obesity by pharmacological means.

Glucagon-like peptide 1 (GLP-1) mimetics are effective drugs for treatment of type 2 diabetes, and there is consequently extensive interest in increasing endogenous GLP-1 secretion and L-cell abundance. Here we identify G-protein–coupled bile acid receptor 1 (GPBAR1) as a selective regulator of intestinal L-cell differentiation. Lithocholic acid and the synthetic GPBAR1 agonist, L3740, selectively increased L-cell density in mouse and human intestinal organoids and elevated GLP-1 secretory capacity. L3740 induced expression of Gcg and transcription factors Ngn3 and NeuroD1. L3740 also increased the L-cell number and GLP-1 levels and improved glucose tolerance in vivo. Further mechanistic examination revealed that the effect of L3740 on L cells required intact GLP-1 receptor and serotonin 5-hydroxytryptamine receptor 4 (5-HT4) signaling. Importantly, serotonin signaling through 5-HT4 mimicked the effects of L3740, acting downstream of GLP-1. Thus, GPBAR1 agonists and other powerful GLP-1 secretagogues facilitate L-cell differentiation through a paracrine GLP-1–dependent and serotonin-mediated mechanism.

Fatty acid amide hydrolase (FAAH) degrades 2 major classes of bioactive fatty acid amides, the N-acylethanolamines (NAEs) and N-acyl taurines (NATs), in central and peripheral tissues. A functional polymorphism in the human FAAH gene is linked to obesity and mice lacking FAAH show altered metabolic states, but whether these phenotypes are caused by elevations in NAEs or NATs is unknown. To overcome the problem of concurrent elevation of NAEs and NATs caused by genetic or pharmacological disruption of FAAH in vivo, we developed an engineered mouse model harboring a single-amino acid substitution in FAAH (S268D) that selectively disrupts NAT, but not NAE, hydrolytic activity. The FAAH-S268D mice accordingly show substantial elevations in NATs without alterations in NAE content, a unique metabolic profile that correlates with heightened insulin sensitivity and GLP-1 secretion. We also show that N-oleoyl taurine (C18:1 NAT), the most abundant NAT in human plasma, decreases food intake, improves glucose tolerance, and stimulates GPR119-dependent GLP-1 and glucagon secretion in mice. Together, these data suggest that NATs act as a class of lipid messengers that improve postprandial glucose regulation and may have potential as investigational metabolites to modify metabolic disease.

The choroid plexus (CP) plays a major role in controlling the entry of substances and immune cells into the brain as it forms the blood-cerebrospinal fluid barrier (BCSFB) in the brain ventricles. Dysregulated immune cell trafficking through the epithelial cell (EC) layer of CP is central for the pathogenesis of infectious diseases in the brain and many neurodegenerative disorders. In vitro studies elucidating the function of the CP have so far been limited to the monolayer culture of CP ECs. To mimic immune cell migration across the CP barrier, a three-dimensional model would be advantageous. Here, we present an in vitro platform for studies of the immune cell trafficking based on CP explants/organoids. The explants were generated from fragments of mouse CPs in Matrigel, where the cells formed luminal spaces and could be maintained in culture for at least 8 weeks. We demonstrate expression of the major CP markers in the explants, including transthyretin and aquaporin 1 as well as ZO1 and ICAM-1, indicating a capacity for secretion of cerebrospinal fluid (CSF) and presence of tight junctions. CP explants displayed CP-like cell polarization and formed an intact EC barrier. We also show that the expression of transthyretin, transferrin, occludin and other genes associated with various functions of CP was maintained in the explants at similar levels as in native CP. By using dendritic cells and neutrophils, we show that the migration activity of immune cells and their interactions with CP epithelium can be monitored by microscopy. Thereby, the three-dimensional CP explant model can be used to study the cellular and molecular mechanisms mediating immune cell migration through CP epithelium and other functions of choroid EC. We propose this platform can potentially be used in the search for therapeutic targets and intervention strategies to improve control of (drug) substances and (immune) cell entry into the central nervous system.

Objective Binding of ghrelin to its receptor, growth hormone secretagogue receptor (GHSR), stimulates GH release, induces eating, and increases blood glucose. These processes may also be influenced by constitutive (ghrelin-independent) GHSR activity, as suggested by findings in short people with naturally occurring GHSR-A204E mutations and reduced food intake and blood glucose in rodents administered GHSR inverse agonists, both of which impair constitutive GHSR activity. In this study, we aimed to more fully determine the physiologic relevance of constitutive GHSR activity. Methods We generated mice with a GHSR mutation that replaces alanine at position 203 with glutamate (GHSR-A203E), which corresponds to the previously described human GHSR-A204E mutation, and used them to conduct ex vivo neuronal electrophysiology and in vivo metabolic assessments. We also measured signaling within COS-7 and HEK293T cells transfected with wild-type GHSR (GHSR-WT) or GHSR-A203E constructs. Results In COS-7 cells, GHSR-A203E resulted in lower baseline IP3 accumulation than GHSR-WT; ghrelin-induced IP3 accumulation was observed in both constructs. In HEK293T cells co-transfected with voltage-gated CaV2.2 calcium channel complex, GHSR-A203E had no effect on basal CaV2.2 current density while GHSR-WT did; both GHSR-A203E and GHSR-WT inhibited CaV2.2 current in the presence of ghrelin. In cultured hypothalamic neurons from GHSR-A203E and GHSR-deficient mice, native calcium currents were greater than those in neurons from wild-type mice; ghrelin inhibited calcium currents in cultured hypothalamic neurons from both GHSR-A203E and wild-type mice. In brain slices, resting membrane potentials of arcuate NPY neurons from GHSR-A203E mice were hyperpolarized compared to those from wild-type mice; the same percentage of arcuate NPY neurons from GHSR-A203E and wild-type mice depolarized upon ghrelin exposure. The GHSR-A203E mutation did not significantly affect body weight, body length, or femur length in the first ∼6 months of life, yet these parameters were lower in GHSR-A203E mice after 1 year of age. During a 7-d 60% caloric restriction regimen, GHSR-A203E mice lacked the usual marked rise in plasma GH and demonstrated an exaggerated drop in blood glucose. Administered ghrelin also exhibited reduced orexigenic and GH secretagogue efficacies in GHSR-A203E mice. Conclusions Our data suggest that the A203E mutation ablates constitutive GHSR activity and that constitutive GHSR activity contributes to the native depolarizing conductance of GHSR-expressing arcuate NPY neurons. Although the A203E mutation does not block ghrelin-evoked signaling as assessed using in vitro and ex vivo models, GHSR-A203E mice lack the usual acute food intake response to administered ghrelin in vivo. The GHSR-A203E mutation also blunts GH release, and in aged mice leads to reduced body length and femur length, which are consistent with the short stature of human carriers of the GHSR-A204E mutation., Graphical abstract Image 1, Highlights • We generated mice with a GHSR mutation replacing Ala at position 203 with Glu. • The A203E mutation ablates constitutive GHSR activity & hyperpolarizes NPY neurons. • GHSR-A203E mice lack the usual orexigenic response to administered ghrelin. • The GHSR-A203E mutation blunts GH release and causes reduced body length. • This finding is consistent with short stature in human carriers of the GHSR-A204E mutation.

Objectives G protein-coupled receptors (GPCRs) act as transmembrane molecular sensors of neurotransmitters, hormones, nutrients, and metabolites. Because unmyelinated vagal afferents richly innervate the gastrointestinal mucosa, gut-derived molecules may directly modulate the activity of vagal afferents through GPCRs. However, the types of GPCRs expressed in vagal afferents are largely unknown. Here, we determined the expression profile of all GPCRs expressed in vagal afferents of the mouse, with a special emphasis on those innervating the gastrointestinal tract. Methods Using a combination of high-throughput quantitative PCR, RNA sequencing, and in situ hybridization, we systematically quantified GPCRs expressed in vagal unmyelinated Nav1.8-expressing afferents. Results GPCRs for gut hormones that were the most enriched in Nav1.8-expressing vagal unmyelinated afferents included NTSR1, NPY2R, CCK1R, and to a lesser extent, GLP1R, but not GHSR and GIPR. Interestingly, both GLP1R and NPY2R were coexpressed with CCK1R. In contrast, NTSR1 was coexpressed with GPR65, a marker preferentially enriched in intestinal mucosal afferents. Only few microbiome-derived metabolite sensors such as GPR35 and, to a lesser extent, GPR119 and CaSR were identified in the Nav1.8-expressing vagal afferents. GPCRs involved in lipid sensing and inflammation (e.g. CB1R, CYSLTR2, PTGER4), and neurotransmitters signaling (CHRM4, DRD2, CRHR2) were also highly enriched in Nav1.8-expressing neurons. Finally, we identified 21 orphan GPCRs with unknown functions in vagal afferents. Conclusion Overall, this study provides a comprehensive description of GPCR-dependent sensing mechanisms in vagal afferents, including novel coexpression patterns, and conceivably coaction of key receptors for gut-derived molecules involved in gut-brain communication., Highlights • Profiling of G protein coupled receptors expression in unmyelinated vagal afferents. • GLP1R, NPY2R and CCK1R are preferentially coexpressed in fibers innervating the GI muscularis. • NTS1R is the only receptor for gut hormone coexpressed with Gpr65, a marker for GI mucosal afferents. • The receptors for ghrelin and GIP are not present in the vagal afferents. • Receptors for inflammatory lipids are broadly expressed in unmyelinated vagal afferents.

Objective: GPR64/ADGRG2 is an orphan Adhesion G protein-coupled receptor (ADGR) known to be mainly expressed in the parathyroid gland and epididymis. This investigation aimed to delineate the cellular expression of GPR64 throughout the body with focus on the gastrointestinal (GI) tract. Methods: Transgenic Gpr64mCherry reporter mice were histologically examined throughout the body and reporter protein expression in intestinal tuft cells was confirmed by specific cell ablation. The GPCR repertoire of intestinal Gpr64mCherry-positive tuft cells was analyzed by quantitative RT-PCR analysis and in situ hybridization. The Gpr64mCherry was crossed into the general tuft cell reporter Trpm5GFP to generate small intestinal organoids for time-lapse imaging. Intestinal tuft cells were isolated from small intestine, FACS-purified and transcriptionally compared using RNAseq analysis. Results: Expression of the Gpr64mCherry reporter was identified in multiple organs and specifically in olfactory microvillous cells, enteric nerves, and importantly in respiratory and GI tuft cells. In the small intestine, cell ablation targeting Gpr64-expressing epithelial cells eliminated tuft cells. Transcriptional analysis of small intestinal Gpr64mCherry -positive tuft cells confirmed expression of Gpr64 and the chemo-sensors Sucnr1, Gprc5c, Drd3, and Gpr41/Ffar3. Time-lapse studies of organoids from Trpm5GFP:Gpr64mCherry mice revealed sequential expression of initially Trpm5GFP and subsequently also Gpr64mCherry in maturing intestinal tuft cells. RNA-seq analysis of small intestinal tuft cells based on these two markers demonstrated a dynamic change in expression of transcription factors and GPCRs from young to mature tuft cells. Conclusions: GPR64 is expressed in chemosensory epithelial cells across a broad range of tissues; however, in the GI tract, GPR64 is remarkably selectively expressed in mature versus young immunoregulatory tuft cells. (c) 2021 The Authors. Published by Elsevier GmbH. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

Objectives Obesity is a complex disease associated with a high risk of comorbidities. Gastric bypass surgery, an invasive procedure with low patient eligibility, is currently the most effective intervention that achieves sustained weight loss. This beneficial effect is attributed to alterations in gut hormone signaling. An attractive alternative is to pharmacologically mimic the effects of bariatric surgery by targeting several gut hormonal axes. The G protein-coupled receptor 39 (GPR39) expressed in the gastrointestinal tract has been shown to mediate ghrelin signaling and control appetite, food intake, and energy homeostasis, but the broader effect on gut hormones is largely unknown. A potent and efficacious GPR39 agonist (Cpd1324) was recently discovered, but the in vivo function was not addressed. Herein we studied the efficacy of the GPR39 agonist, Cpd1324, on metabolism and gut hormone secretion. Methods Body weight, food intake, and energy expenditure in GPR39 agonist-treated mice and GPR39 KO mice were studied in calorimetric cages. Plasma ghrelin, glucose-dependent insulinotropic polypeptide (GIP), glucagon-like peptide-1 (GLP-1), and peptide YY (PYY) levels were measured. Organoids generated from murine and human small intestine and mouse colon were used to study GLP-1 and PYY release. Upon GPR39 agonist administration, dynamic changes in intracellular GLP-1 content were studied via immunostaining and changes in ion transport across colonic mucosa were monitored in Ussing chambers. The G protein activation underlying GPR39-mediated selective release of gut hormones was studied using bioluminescence resonance energy transfer biosensors. Results The GPR39 KO mice displayed a significantly increased food intake without corresponding increases in respiratory exchange ratios or energy expenditure. Oral administration of a GPR39 agonist induced an acute decrease in food intake and subsequent weight loss in high-fat diet (HFD)-fed mice without affecting their energy expenditure. The tool compound, Cpd1324, increased GLP-1 secretion in the mice as well as in mouse and human intestinal organoids, but not in GPR39 KO mouse organoids. In contrast, the GPR39 agonist had no effect on PYY or GIP secretion. Transepithelial ion transport was acutely affected by GPR39 agonism in a GLP-1- and calcitonin gene-related peptide (CGRP)-dependent manner. Analysis of Cpd1324 signaling properties showed activation of Gαq and Gαi/o signaling pathways in L cells, but not Gαs signaling. Conclusions The GPR39 agonist described in this study can potentially be used by oral administration as a weight-lowering agent due to its stimulatory effect on GLP-1 secretion, which is most likely mediated through a unique activation of Gα subunits. Thus, GPR39 agonism may represent a novel approach to effectively treat obesity through selective modulation of gastrointestinal hormonal axes., Graphical abstract Image 1, Highlights • Orally active GPR39 agonist decreased food intake and body weight in high-fat diet-fed mice • Orally administrated GPR39 agonist increased plasma GLP-1 secretion while decreasing plasma ghrelin in mice • GPR39 agonist induced selective release of GLP-1 from enteroendocrine cells but not the other important L cell product PYY • GPR39 agonism acutely affected transepithelial ion transport through GLP-1 via CGRP signaling • GPR39 selective gut hormone release is suggested to be due to activation of the Gαq and Gα i/o signaling pathways

Objective Enteroendocrine cells (EECs) of the gastro-intestinal tract sense gut luminal factors and release peptide hormones or serotonin (5-HT) to coordinate energy uptake and storage. Our goal is to decipher the gene regulatory networks controlling EECs specification from enteroendocrine progenitors. In this context, we studied the role of the transcription factor Rfx6 which had been identified as the cause of Mitchell–Riley syndrome, characterized by neonatal diabetes and congenital malabsorptive diarrhea. We previously reported that Rfx6 was essential for pancreatic beta cell development and function; however, the role of Rfx6 in EECs differentiation remained to be elucidated. Methods We examined the molecular, cellular, and metabolic consequences of constitutive and conditional deletion of Rfx6 in the embryonic and adult mouse intestine. We performed single cell and bulk RNA-Seq to characterize EECs diversity and identify Rfx6-regulated genes. Results Rfx6 is expressed in the gut endoderm; later, it is turned on in, and restricted to, enteroendocrine progenitors and persists in hormone-positive EECs. In the embryonic intestine, the constitutive lack of Rfx6 leads to gastric heterotopia, suggesting a role in the maintenance of intestinal identity. In the absence of intestinal Rfx6, EECs differentiation is severely impaired both in the embryo and adult. However, the number of serotonin-producing enterochromaffin cells and mucosal 5-HT content are increased. Concomitantly, Neurog3-positive enteroendocrine progenitors accumulate. Combined analysis of single-cell and bulk RNA-Seq data revealed that enteroendocrine progenitors differentiate in two main cell trajectories, the enterochromaffin (EC) cells and the Peptidergic Enteroendocrine (PE) cells, the differentiation programs of which are differentially regulated by Rfx6. Rfx6 operates upstream of Arx, Pax6 and Isl1 to trigger the differentiation of peptidergic EECs such as GIP-, GLP-1-, or CCK-secreting cells. On the contrary, Rfx6 represses Lmx1a and Tph1, two genes essential for serotonin biosynthesis. Finally, we identified transcriptional changes uncovering adaptive responses to the prolonged lack of enteroendocrine hormones and leading to malabsorption and lower food efficiency ratio in Rfx6-deficient mouse intestine. Conclusion These studies identify Rfx6 as an essential transcriptional regulator of EECs specification and shed light on the molecular mechanisms of intestinal failures in human RFX6-deficiencies such as Mitchell–Riley syndrome., Highlights • The lack of Rfx6 impairs the differentiation of peptide-producing enteroendocrine cells. • The number of 5-HT-expressing-cells is increased in Rfx6-deficient intestine. • Intestinal inactivation of Rfx6 leads to lipid malabsorption and decreased food efficiency.

This article promotes a discussion of western legal concept which sees individuals as subjects of rights, discussing the advisability of such a formulation in the context of clinical trials in humans, since the commonly borderline situation of vulnerability in which they are volunteers who submit to such procedures. For this purpose, it was used as a theoretical framework to work "Critical Introduction to Law" Michel Mialle, in which the author states in a forceful way that the construction of the legal institute of the "subject of law" and the imposition of unrestricted recognition of individual autonomy constitute a construction of the bourgeois state to facilitate the domination of vulnerable, so that this, although not legally obliged to practice certain behaviors, see forced by circumstances to act in line with the interests of that institution. It is argued, therefore, that autonomy to consent to participation in scientific trials must be assessed in each case, with special attention to circumstances which might vulnerabilizar voluntary research and mitigate their individual autonomy in the face of the experiments, under penalty to be subjecting the individual to harmful procedures to their lives and health for the benefit of capital society's interests., O presente artigo promove uma discussão em torno da concepção jurídica ocidental que concebe os indivíduos como sujeitos de direito, polemizando a conveniência de tal formulação no âmbito das pesquisas clínicas em seres humanos, posto a situação comumente limítrofe de vulnerabilidade em que se encontram os voluntários que se submetem aos referidos procedimentos. Para tanto, utilizou-se como marco teórico a obra Introdução crítica ao Direito de Michel Mialle, na qual o autor afirma de maneira contundente que a construção do instituto jurídico do sujeito de direito e a imposição do reconhecimento irrestrito da autonomia individual constituem uma construção do Estado burguês para facilitar a dominação do vulnerável, de maneira que este, mesmo não sendo juridicamente obrigado à praticar determinadas condutas, veja-se obrigado pelas circunstâncias a atuar em consonância com os interesses de tal instituição. Defende-se, desse modo, que a autonomia para consentir com a participação nos ensaios científicos deva ser aferida em cada caso concreto, com atenção especial às circunstâncias capazes de vulnerabilizar o voluntário de pesquisa e mitigar sua autonomia individual em face dos experimentos, sob pena de se estar submetendo o indivíduo à procedimentos nocivos a sua vida e saúde em prol dos interesses da sociedade de capital.

OBJECTIVES: GPR142, which is highly expressed in pancreatic islets, has recently been deorphanized as a receptor for aromatic amino acids; however, its physiological role and pharmacological potential is unclear.METHODS AND RESULTS: We find that GPR142 is expressed not only in β- but also in α-cells of the islets as well as in enteroendocrine cells, and we confirm that GPR142 is a highly selective sensor of essential aromatic amino acids, in particular Trp and oligopeptides with N-terminal Trp. GPR142 knock-out mice displayed a very limited metabolic phenotype but demonstrated that L-Trp induced secretion of pancreatic and gut hormones is mediated through GPR142 but that the receptor is not required for protein-induced hormone secretion. A synthetic GPR142 agonist stimulated insulin and glucagon as well as GIP, CCK, and GLP-1 secretion. In particular, GIP secretion was sensitive to oral administration of the GPR142 agonist an effect which in contrast to the other hormones was blocked by protein load. Oral administration of the GPR142 agonist increased [3H]-2-deoxyglucose uptake in muscle and fat depots mediated through insulin action while it lowered liver glycogen conceivably mediated through glucagon, and, consequently, it did not lower total blood glucose. Nevertheless, acute administration of the GPR142 agonist strongly improved oral glucose tolerance in both lean and obese mice as well as Zucker fatty rat. Six weeks in-feed chronic treatment with the GPR142 agonist did not affect body weight in DIO mice, but increased energy expenditure and carbohydrate utilization, lowered basal glucose, and improved insulin sensitivity.CONCLUSIONS: GPR142 functions as a sensor of aromatic amino acids, controlling GIP but also CCK and GLP-1 as well as insulin and glucagon in the pancreas. GPR142 agonists could have novel interesting potential in modifying metabolism through a balanced action of gut hormones as well as both insulin and glucagon.

Glucose stimulates insulin secretion from β-cells by increasing intracellular Ca(2+). Ca(2+) then binds to synaptotagmin-7 as a major Ca(2+) sensor for exocytosis, triggering secretory granule fusion and insulin secretion. In type-2 diabetes, insulin secretion is impaired; this impairment is ameliorated by glucagon-like peptide-1 (GLP-1) or by GLP-1 receptor agonists, which improve glucose homeostasis. However, the mechanism by which GLP-1 receptor agonists boost insulin secretion remains unclear. Here, we report that GLP-1 stimulates protein kinase A (PKA)-dependent phosphorylation of synaptotagmin-7 at serine-103, which enhances glucose- and Ca(2+)-stimulated insulin secretion and accounts for the improvement of glucose homeostasis by GLP-1. A phospho-mimetic synaptotagmin-7 mutant enhances Ca(2+)-triggered exocytosis, whereas a phospho-inactive synaptotagmin-7 mutant disrupts GLP-1 potentiation of insulin secretion. Our findings thus suggest that synaptotagmin-7 is directly activated by GLP-1 signaling and may serve as a drug target for boosting insulin secretion. Moreover, our data reveal, to our knowledge, the first physiological modulation of Ca(2+)-triggered exocytosis by direct phosphorylation of a synaptotagmin.

Second generation antipsychotics cause derangements in glucose metabolism that are often interpreted as insulin resistance. In previous studies we have shown that this is not classical insulin resistance but the drugs were actually inducing a hyperglycaemic state associated with elevated hepatic glucose output (HGO) and increased levels of glucagon and insulin. However, it remains unclear whether these effects are directly elicited by drug actions in the liver and pancreas, or whether they are indirectly mediated. Here we investigated if clozapine is capable of inducing insulin resistance in the liver or enhancing insulin and glucagon secretion from the pancreas. It was observed that insulin signalling was elevated in livers from animals treated with clozapine indicating there was no insulin resistance in the early steps of insulin signalling. To explore whether the defects arise at later stages of insulin action we used an isolated perfused liver system. In this model, clozapine had no direct effect on insulin's counter regulatory effect on epinephrine-induced HGO. In isolated mouse islets clozapine significantly increased glucose-stimulated insulin secretion while simultaneously blocking glucose-induced reductions in glucagon secretion. We also show that the non-peptidic glucagon receptor like peptide-1 (GLP-1) receptor agonist Boc5 was able to overcome the inhibitory effects of clozapine on glucose metabolism. Taken together these results suggest that clozapine does not have any direct effect on glucose metabolism in the liver but it simultaneously stimulates insulin and glucagon secretion, a situation that would allow for the concurrent presence of high glucose and high insulin levels in treated animals.

Background & Aims Glucagon-like peptide 1 (GLP1) is produced by L cells in the intestine, and agonists of the GLP1 receptor are effective in the treatment of diabetes. Levels of GLP1 increase with numbers of L cells. Therefore, agents that increase numbers of L cell might be developed for treatment of diabetes. Ras homologue family member A (RhoA) signaling through Rho-associated coiled–coil-containing protein kinases 1 and 2 (ROCK1 and ROCK2) controls cell differentiation, but it is not clear whether this pathway regulates enteroendocrine differentiation in the intestinal epithelium. We investigated the effects of Y-27632, an inhibitor of ROCK1 and ROCK2, on L-cell differentiation. Methods We collected intestinal tissues from GLU-Venus, GPR41-RFP, and Neurog3-RFP mice, in which the endocrine lineage is fluorescently labeled, for in vitro culture and histologic analysis. Small intestine organoids derived from these mice were cultured with Y-27632 and we measured percentages of L cells, expression of intestinal cell-specific markers, and secretion of GLP1 in medium. Mice were fed a normal chow or a high-fat diet and given Y-27632 or saline (control) and blood samples were collected for measurement of GLP1, insulin, and glucose. Results Incubation of intestinal organoids with Y-27632 increased numbers of L cells and secretion of GLP1. These increases were associated with upregulated expression of genes encoding intestinal hormones, neurogenin 3, neurogenic differentiation factor 1, forkhead box A1 and A2, and additional markers of secretory cells. Mice fed the normal chow diet and given Y-27632 had increased numbers of L cells in intestinal tissues, increased plasma levels of GLP1 and insulin, and lower blood levels of glucose compared with mice fed the normal chow diet and given saline. In mice with insulin resistance induced by the high-fat diet, administration of Y-27632 increased secretion of GLP1 and glucose tolerance compared with administration of saline. Conclusions In mouse intestinal organoids, an inhibitor of RhoA signaling increased the differentiation of the secretory lineage and the development of enteroendocrine cells. Inhibitors of RhoA signaling or other strategies to increase numbers of L cells might be developed for treatment of patients with type 2 diabetes or for increasing glucose tolerance.

Micro-RNAs (miRNAs) are crucial for many biological processes, but their role in the enteroendocrine development and differentiation has been neglected due to the elusive nature of the enteroendocrine cells. However, transgenic mice expressing fluorescent reporter proteins under the control of promoters for Cck, Gpr41, and Lgr5, ie, two different enteroendocrine markers and a marker for the stem cells, now enables identification and FACS purification of enteroendocrine cells at different stages of their differentiation along the crypt-villus axis. Surprisingly few of the 746 analyzed miRNAs differed in their expression pattern between enteroendocrine and nonenteroendocrine cells of the gut mucosa and between enteroendocrine cells of the crypt versus the villus. Thus, only let-7g-3p, miR-7b-5p (miR-7b), and miR-375–3p (miR-375) were up-regulated in the enteroendocrine cells of both the crypt and villus compared with nonenteroendocrine cells, and in situ hybridization confirmed colocalization of miR-375 with the enteroendocrine cells. Finally, functional assays using miR-375 inhibitor and mimetic in organoid cultures revealed miR-375 as a potential regulator of the enteroendocrine lineage. Overexpression of miR-375 inhibited enteroendocrine lineage development, whereas inhibition of miR-375 stimulated the development of enteroendocrine cells in vitro. Thus, through an unbiased expression screening of all miRNA, we find very few miRNAs that are differentially expressed in the gastrointestinal mucosa. Of these, miR-375 is found to be both highly expressed and enriched in the enteroendocrine cells. Additionally, miR-375 appears to negatively regulate the development of enteroendocrine cells. Consequently, miR-375 emerges as a potential target to modulate the function of the enteroendocrine system.

Glucagon-like peptide-1-based (GLP-1-based) therapies improve glycemic control in patients with type 2 diabetes. While these agents augment insulin secretion, they do not mimic the physiological meal-related rise and fall of GLP-1 concentrations. Here, we tested the hypothesis that increasing the number of intestinal L cells, which produce GLP-1, is an alternative strategy to augment insulin responses and improve glucose tolerance. Blocking the NOTCH signaling pathway with the γ-secretase inhibitor dibenzazepine increased the number of L cells in intestinal organoid-based mouse and human culture systems and augmented glucose-stimulated GLP-1 secretion. In a high-fat diet-fed mouse model of impaired glucose tolerance and type 2 diabetes, dibenzazepine administration increased L cell numbers in the intestine, improved the early insulin response to glucose, and restored glucose tolerance. Dibenzazepine also increased K cell numbers, resulting in increased gastric inhibitory polypeptide (GIP) secretion. Using a GLP-1 receptor antagonist, we determined that the insulinotropic effect of dibenzazepine was mediated through an increase in GLP-1 signaling. Together, our data indicate that modulation of the development of incretin-producing cells in the intestine has potential as a therapeutic strategy to improve glycemic control.

Mantle Pds (Fig. 1) converted phases are detected in the records of 11 seismograph stations in easternmost Russia and China. These data reveal neither a strong depression on the 660-km discontinuity nor a layer of partial melting atop the 410-km discontinuity that were found previously beneath this region in studies using long-period underside SH reflections and multiple ScS reverberations. Apparently, a significant deepening of the 660-km discontinuity occurs only if the subducted plate penetrates the discontinuity, which is not the case in the study region. Most estimates of thickness of the mantle transition zone (MTZ) in Eurasia based on the Pds data are a few kilometres larger than the standard value (250 km), and suggest that the average thickness of the MTZ beneath Eurasia is about 10 kilometres more than beneath the surrounding oceans.

This article promotes a discussion of western legal concept which sees individuals as subjects of rights, discussing the advisability of such a formulation in the context of clinical trials in humans, since the commonly borderline situation of vulnerability in which they are volunteers who submit to such procedures. For this purpose, it was used as a theoretical framework to work "Critical Introduction to Law" Michel Mialle, in which the author states in a forceful way that the construction of the legal institute of the "subject of law" and the imposition of unrestricted recognition of individual autonomy constitute a construction of the bourgeois state to facilitate the domination of vulnerable, so that this, although not legally obliged to practice certain behaviors, see forced by circumstances to act in line with the interests of that institution. It is argued, therefore, that autonomy to consent to participation in scientific trials must be assessed in each case, with special attention to circumstances which might vulnerabilizar voluntary research and mitigate their individual autonomy in the face of the experiments, under penalty to be subjecting the individual to harmful procedures to their lives and health for the benefit of capital society's interests., O presente artigo promove uma discussão em torno da concepção jurídica ocidental que concebe os indivíduos como sujeitos de direito, polemizando a conveniência de tal formulação no âmbito das pesquisas clínicas em seres humanos, posto a situação comumente limítrofe de vulnerabilidade em que se encontram os voluntários que se submetem aos referidos procedimentos. Para tanto, utilizou-se como marco teórico a obra Introdução crítica ao Direito de Michel Mialle, na qual o autor afirma de maneira contundente que a construção do instituto jurídico do sujeito de direito e a imposição do reconhecimento irrestrito da autonomia individual constituem uma construção do Estado burguês para facilitar a dominação do vulnerável, de maneira que este, mesmo não sendo juridicamente obrigado à praticar determinadas condutas, veja-se obrigado pelas circunstâncias a atuar em consonância com os interesses de tal instituição. Defende-se, desse modo, que a autonomia para consentir com a participação nos ensaios científicos deva ser aferida em cada caso concreto, com atenção especial às circunstâncias capazes de vulnerabilizar o voluntário de pesquisa e mitigar sua autonomia individual em face dos experimentos, sob pena de se estar submetendo o indivíduo à procedimentos nocivos a sua vida e saúde em prol dos interesses da sociedade de capital.

Glucagon-like peptide 1 (GLP-1) is produced by intestinal L-cells, augments insulin secretion and plays an important role in glucose homeostasis. Enhancing endogenous GLP-1 secretion improves glycemic control in patients with type 2 diabetes. However, it is not clear how a change in L-cell number could contribute to circulating GLP-1 levels in physiological conditions and in type 2 diabetes.