Characterization of genetic variants of GIPR reveals a contribution of ß-arrestin to metabolic phenotypes.

Incretin-based therapies are highly successful in combatting obesity and type 2 diabetes1. Yet both activation and inhibition of the glucose-dependent insulinotropic polypeptide (GIP) receptor (GIPR) in combination with glucagon-like peptide-1 (GLP-1) receptor (GLP-1R) activation have resulted in similar clinical outcomes, as demonstrated by the GIPR-GLP-1R co-agonist tirzepatide2 and AMG-133 (ref. 3) combining GIPR antagonism with GLP-1R agonism. This underlines the importance of a better understanding of the GIP system. Here we show the necessity of ß-arrestin recruitment for GIPR function, by combining in vitro pharmacological characterization of 47 GIPR variants with burden testing of clinical phenotypes and in vivo studies. Burden testing of variants with distinct ligand-binding capacity, Gs activation (cyclic adenosine monophosphate production) and ß-arrestin 2 recruitment and internalization shows that unlike variants solely impaired in Gs signalling, variants impaired in both Gs and ß-arrestin 2 recruitment contribute to lower adiposity-related traits. Endosomal Gs-mediated signalling of the variants shows a ß-arrestin dependency and genetic ablation of ß-arrestin 2 impairs cyclic adenosine monophosphate production and decreases GIP efficacy on glucose control in male mice. This study highlights a crucial impact of ß-arrestins in regulating GIPR signalling and overall preservation of biological activity that may facilitate new developments in therapeutic targeting of the GIPR system.

Intra-islet α-cell Gs signaling promotes glucagon release.

Glucagon, a hormone released from pancreatic α-cells, is critical for maintaining euglycemia and plays a key role in the pathophysiology of diabetes. To stimulate the development of new classes of therapeutic agents targeting glucagon release, key α-cell signaling pathways that regulate glucagon secretion need to be identified. Here, we focused on the potential importance of α-cell Gs signaling on modulating α-cell function. Studies with α-cell-specific mouse models showed that activation of α-cell Gs signaling causes a marked increase in glucagon secretion. We also found that intra-islet adenosine plays an unexpected autocrine/paracrine role in promoting glucagon release via activation of α-cell Gs-coupled A2A adenosine receptors. Studies with α-cell-specific Gαs knockout mice showed that α-cell Gs also plays an essential role in stimulating the activity of the Gcg gene, thus ensuring proper islet glucagon content. Our data suggest that α-cell enriched Gs-coupled receptors represent potential targets for modulating α-cell function for therapeutic purposes.

Evaluating GIP and glucagon as key regulators of insulin secretion in the pancreatic islet.

The incretin axis is an essential component of postprandial insulin secretion and glucose homeostasis. There are two incretin hormones, glucagon-like peptide 1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), which exert multiple actions throughout the body. A key cellular target for the incretins are pancreatic b-cells, where they potentiate nutrient-stimulated insulin secretion. This feature of incretins have made this system an attractive target for therapeutic interventions aimed at controlling glycemia. Here, we discuss the role of GIP in both b-cells and a-cells within the islet, to stimulate insulin and glucagon secretion, respectively. Moreover, we discuss how glucagon secretion from a-cells has important insulinotropic actions in b-cells through an axis termed a- to b-cell communication. These recent advances have elevated the potential of GIP and glucagon as a therapeutic targets, coinciding with emerging compounds that pharmacologically leverage the actions of these two peptides in the context of diabetes and obesity.

Training Law Enforcement Officers About Autism: Evaluation of Adding Virtual Reality or Simulation to a Traditional Training Approach.

Prevalence rates of autism spectrum disorder (ASD) across the globe and lifespan suggest that law enforcement officers (LEOs) are likely to interact with autistic people in their professional duties. In developed countries, LEOs have professional encounters with autistic individuals, and research strongly supports LEOs need training to increase their knowledge about autism and confidence interacting with autistic people. The purpose of the present study is to compare three training approaches with LEOs: (a) a training presentation alone (P), (b) a training presentation combined with virtual reality simulation (P + VR), and (c) a training presentation combined with in-vivo simulation (P + SIM). The primary outcomes are LEO knowledge of autism and self-reported confidence in responding to autism calls. The present study included 259 LEOS who completed a survey assessing autism knowledge and confidence in level of skill before and after participating in ASD-specific training for LEOs. Findings support that participant knowledge of autism and confidence in responding significantly increased for all LEOs equally across training conditions. Results support that formalized training in ASD significantly impacts LEO's knowledge of ASD and confidence responding to calls. As such, standardized training for LEOs is needed to assure appropriate knowledge and confidence when responding to calls involving autistic persons.

Development of novel iron(III) crosslinked bioinks comprising carboxymethyl cellulose, xanthan gum, and hyaluronic acid for soft tissue engineering applications.

The advent of three-dimensional (3D) bioprinting offers a feasible approach to construct complex structures for soft tissue regeneration. Carboxymethyl cellulose (CMC) has been emerging as a very promising biomaterial for 3D bioprinting. However, due to the inability to maintain the post-printed stability, CMC needs to be physically blended and/or chemically crosslinked with other polymers. In this context, this study presents the combination of CMC with xanthan gum (XG) and hyaluronic acid (HA) to formulate a multicomponent bioink, leveraging the printability of CMC and XG, as well as the cellular support properties of HA. The ionic crosslinking of printed constructs with iron(III) via the metal-ion coordination between ferric cations and carboxylate groups of the three polymers was introduced to induce improved mechanical strength and long-term stability. Moreover, immortalized human epidermal keratinocytes (HaCaT) and human foreskin fibroblasts (HFF) encapsulated within iron-crosslinked printed hydrogels exhibited excellent cell viability (more than 95%) and preserved morphology. Overall, the presented study highlights that the combination of these three biopolymers and the ionic crosslinking with ferric ions is a valuable strategy to be considered for the development of new and advanced hydrogel-based bioinks for soft tissue engineering applications.

The impact of sire breed on feedlot performance and carcass characteristics of beef × Holstein steers.

Dairy herds are mating a portion of cows to beef cattle semen to create a value-added calf. Objectives of this study were to compare the feedlot performance and carcass characteristics of beef × Holstein steers by breed when sires represented bulls with commercially available semen. Three groups of single-born, male calves (n = 262) born to Holstein dams on 10 Pennsylvania dairies were sourced during 3 yr. Steers were sired by seven beef breeds: Angus, Charolais, Limousin, Hereford, Red Angus, Simmental, and Wagyu. Steers were picked up within a week of age and raised at two preweaned calf facilities until weaning (8 ±â€…1 wk of age) under similar health and management protocols. Steers were then transported to a commercial calf growing facility where they were managed as a single group until 10 ±â€…2 mo of age when they were moved to be finished at the Pennsylvania Department of Agriculture's Livestock Evaluation Center feedlot. Groups of steers were selected for slaughter based on body weight. Carcass characteristics were evaluated by trained personnel and a three-rib section of the longissimus muscle (LM) was collected from each carcass for Warner-Bratzler shear force (WBSF) evaluation and intramuscular fat determination. Steers sired by all sire breeds except for Limousin had greater average daily gain (ADG; 1.62 to 1.76 kg/d) than Wagyu × Holstein steers (1.39 kg/d; P < 0.05). Angus-sired steers had an 8.6% greater ADG than Red Angus-sired steers (P < 0.05). Angus, Charolais (1.73 kg/d), and Simmental-sired steers (1.68 kg/d) also had greater ADG than Limousin-sired steers (1.55 kg/d; P < 0.05). Wagyu × Holstein steers spent 5 to 26 more days on feed (P < 0.05) than Limousin × Holstein, Simmental × Holstein, Angus × Holstein, and Charolais × Holstein steers. Angus and Charolais-sired steers were also on feed for 19 and 21 d fewer, respectively, than Limousin-sired steers (P < 0.05). Red Angus-sired steers had greater marbling scores than Simmental and Limousin-sired steers and Angus and Charolais-sired steers had greater marbling scores than Limousin-sired steers (P < 0.05). Angus, Limousin, and Hereford-sired steers produced the most tender LM as evaluated by WBSF; Angus-sired carcasses (3.82 kg) were more tender than Charolais (4.30 kg) and Simmental-sired carcasses (4.51 kg; P < 0.05). Limousin and Hereford-sired steers (3.70 and 3.83 kg, respectively) also had more tender steaks than Simmental-sired steers.

Cost-Effectiveness of HIV Screening in Emergency Departments: Results From the Pragmatic Randomized HIV Testing Using Enhanced Screening Techniques in Emergency Departments Trial.

STUDY OBJECTIVE: Identification of HIV remains a critical health priority for which emergency departments (EDs) are a central focus. The comparative cost-effectiveness of various HIV screening strategies in EDs remains largely unknown. The goal of this study was to compare programmatic costs and cost-effectiveness of nontargeted and 2 forms of targeted opt-out HIV screening in EDs using results from a multicenter, pragmatic randomized clinical trial. METHODS: This economic evaluation was nested in the HIV Testing Using Enhanced Screening Techniques in Emergency Departments (TESTED) trial, a multicenter pragmatic clinical trial of different ED-based HIV screening strategies conducted from April 2014 through January 2016. Patients aged 16 years or older, with normal mental status and not critically ill, or not known to be living with HIV were randomized to 1 of 3 HIV opt-out screening approaches, including nontargeted, enhanced targeted, or traditional targeted, across 4 urban EDs in the United States. Each screening method was fully integrated into routine emergency care. Direct programmatic costs were determined using actual trial results, and time-motion assessment was used to estimate personnel activity costs. The primary outcome was newly diagnosed HIV. Total annualized ED programmatic costs by screening approach were calculated using dollars adjusted to 2023 as were costs per patient newly diagnosed with HIV. One-way and multiway sensitivity analyses were performed. RESULTS: The trial randomized 76,561 patient visits, resulting in 14,405 completed HIV tests, and 24 (0.2%) new diagnoses. Total annualized new diagnoses were 12.9, and total annualized costs for nontargeted, enhanced targeted, and traditional targeted screening were $111,861, $88,629, and $70,599, respectively. Within screening methods, costs per new HIV diagnoses were $20,809, $23,554, and $18,762, respectively. Enhanced targeted screening incurred higher costs but with similar annualized new cases detected compared with traditional targeted screening. Nontargeted screening yielded an incremental cost-effectiveness ratio of $25,586 when compared with traditional targeted screening. Results were most sensitive to HIV prevalence and costs of HIV tests. CONCLUSION: Nontargeted HIV screening was more costly than targeted screening largely due to an increased number of HIV tests performed. Each HIV screening strategy had similar within-strategy costs per new HIV diagnosis with traditional targeted screening yielding the lowest cost per new diagnosis. For settings with budget constraints or very low HIV prevalences, the traditional targeted approach may be preferred; however, given only a slightly higher cost per new HIV diagnosis, ED settings looking to detect the most new cases may prefer nontargeted screening.

Medicare Part D Coverage of Drugs Selected for the Drug Price Negotiation Program.

This cross-sectional study describes and historically benchmarks Medicare Part D coverage in 2019 and 2023 for the first 10 drugs selected for negotiation.

GLP1R and GIPR expression and signaling in pancreatic alpha cells, beta cells and delta cells.

Glucagon-like peptide-1 receptor (GLP1R) and glucose-dependent insulinotropic polypeptide receptor (GIPR) are transmembrane receptors involved in insulin, glucagon and somatostatin secretion from the pancreatic islet. Therapeutic targeting of GLP1R and GIPR restores blood glucose levels in part by influencing beta cell, alpha cell and delta cell function. Despite the importance of the incretin-mimetics for diabetes therapy, our understanding of GLP1R and GIPR expression patterns and signaling within the islet remain incomplete. Here, we present the evidence for GLP1R and GIPR expression in the major islet cell types, before addressing signaling pathway(s) engaged, as well as their influence on cell survival and function. While GLP1R is largely a beta cell-specific marker within the islet, GIPR is expressed in alpha cells, beta cells, and (possibly) delta cells. GLP1R and GIPR engage Gs-coupled pathways in most settings, although the exact outcome on hormone release depends on paracrine communication and promiscuous signaling. Biased agonism away from beta-arrestin is an emerging concept for improving therapeutic efficacy, and is also relevant for GLP1R/GIPR dual agonism. Lastly, dual agonists exert multiple effects on islet function through GIPR > GLP1R imbalance, increased GLP1R surface expression and cAMP signaling, as well as beneficial alpha cell-beta cell-delta cell crosstalk.

High Doses of Exogenous Glucagon Stimulate Insulin Secretion and Reduce Insulin Clearance in Healthy Humans.

Glucagon is generally defined as a counterregulatory hormone with a primary role to raise blood glucose concentrations by increasing endogenous glucose production (EGP) in response to hypoglycemia. However, glucagon has long been known to stimulate insulin release, and recent preclinical findings have supported a paracrine action of glucagon directly on islet ß-cells that augments their secretion. In mice, the insulinotropic effect of glucagon is glucose dependent and not present during basal euglycemia. To test the hypothesis that the relative effects of glucagon on hepatic and islet function also vary with blood glucose, a group of healthy subjects received glucagon (100 ng/kg) during fasting glycemia or experimental hyperglycemia (∼150 mg/dL) on 2 separate days. During fasting euglycemia, administration of glucagon caused blood glucose to rise due to increased EGP, with a delayed increase of insulin secretion. When given during experimental hyperglycemia, glucagon caused a rapid, threefold increase in insulin secretion, as well as a more gradual increase in EGP. Under both conditions, insulin clearance was decreased in response to glucagon infusion. The insulinotropic action of glucagon, which is proportional to the degree of blood glucose elevation, suggests distinct physiologic roles in the fasting and prandial states.

Intellectual, Adaptive, and Behavioral Functioning Associated with Designated Levels of Support in a Sample of Autistic Children Referred for Tertiary Assessment.

The diagnostic criteria for autism spectrum disorder in the DSM-5-TR features the option to designate levels of support for social communication (SC) and restricted, repetitive behaviors (RRB). These levels are conceptual in nature, but research indicates standardized assessment outcomes correspond with clinician-assigned levels of support. The purpose of the present study was to identify factors that influence designated levels of support for SC and RRBs when diagnosing autism. Standardized assessment scores across intellectual functioning, adaptive skills, and ASD symptomology were analyzed to determine corresponding levels of support in SC and RRBs assigned by clinicians for 136 autistic children following a comprehensive diagnostic evaluation. At diagnosis, approximately 46% of participants were described as needing substantial support (Level 2) for SC and 49% were described as needing substantial support (Level 2) for RRB. There was a consistent pattern of higher to lower intellectual and adaptive functioning needing Level 1-Level 3 support. Autism assessment results followed a gradient of fewer to greater autism symptoms from Level 1 to Level 3 support. Findings indicated clinician-assigned levels of support for SC and RRB were associated with intellectual functioning, adaptive functioning, autism symptomology, and age, but not sex.

Interprofessional education on autism and intellectual disabilities: Program description and initial evaluation.

Project INTERprofessional Autism Collaborative Training (INTERACT) is an interprofessional education program designed to prepare graduate students in psychology, special education, and speech-language pathology to work with autistic children with moderate to severe intellectual disabilities. The rising prevalence of autism, coupled with increased appreciation for interprofessional approaches to service delivery, indicates the need for university training programs to prepare graduate students to work interprofessionally with this population; yet descriptions of such programs and their effectiveness are not reported in the literature. In this article, we explain the process through which an interprofessional faculty team developed Project INTERACT, describe the sequence of coursework and team-based clinical experiences that comprise the program, and present preliminary data regarding its effectiveness. Twenty-four graduate students in psychology, special education, and speech-language pathology participated in this quantitative study. We report results from three rating scales that participants completed at program entry, midpoint, and program exit. Participants endorsed positive attitudes toward interprofessional practice and demonstrated high levels of knowledge about autism. Self-rated knowledge and abilities in interprofessional practice increased significantly by program exit. Project INTERACT scholars developed knowledge and skills related to understanding, assessing, and treating autistic children with intellectual disabilities, through the lens of team-based interprofessional collaboration. We discuss implications for practice with Project INTERACT. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

GIPR/GLP-1R dual agonist therapies for diabetes and weight loss-chemistry, physiology, and clinical applications.

The incretin system is an essential metabolic axis that regulates postprandial metabolism. The two incretin peptides that enable this effect are the glucose-dependent insulinotropic polypeptide (GIP) and the glucagon-like peptide 1 (GLP-1), which have cognate receptors (GIPR and GLP-1R) on islet ß cells as well as in other tissues. Pharmacologic engagement of the GLP-1R is a proven strategy for treating hyperglycemia in diabetes and reducing body weight. Tirzepatide is the first monomeric peptide with dual activity at both incretin receptors now available for clinical use, and in clinical trials it has shown unprecedented effects to reduce blood glucose and body weight. Here, we discuss the foundational science that led to the development of monomeric multi-incretin receptor agonists, culminating in the development of tirzepatide. We also look to the future of this field and comment on how the concept of multi-receptor agonists will continue to progress for the treatment of metabolic disease.

GPCR Promiscuity Reshapes Islet Physiology.

The family of proglucagon peptides Includes glucagon and glucagon-like peptide 1 (GLP-1), two unique peptides derived from the same prohormone. Despite numerous similarities between the peptides, these have long been viewed as having opposing actions on metabolism. GLP-1 is described as a postprandial hormone that stimulates anabolic actions via insulin, while glucagon is viewed as a fasting hormone that drives catabolic actions to maintain euglycemia. Here, we revisit a classic article in Diabetes that first established that glucagon and GLP-1 have more in common than previously appreciated, including actions at the same receptor. Furthermore, we discuss how the impact of this observation has guided research decades later that has reshaped the view of how proglucagon hormones regulate metabolism.

An Alternative Measure of Health for Value Assessment: The Equal Value Life-Year.

The quality-adjusted life-year (QALY) is an international standard in cost-effectiveness analysis. A known concern arises from the relatively lower QALY gains attributed to treatments that extend the life of individuals with chronic disability. We analyze here the advantages and disadvantages of the equal value life-year (evLY) as an alternative or a complementary measure to the QALY, and share learned experiences from using this measure in health technology assessments. We present the conceptual rationale for the evLY, describe how it is estimated, and assess the differences in results between analyses based on the evLY and the QALY. We share a how-to guide in estimating the evLY using a downloadable tool and summarize our empirical experience using this measure. Incremental evLYs are feasible and address concerns regarding the risk for a cost-effectiveness analysis to undervalue treatments for people with chronic disabilities. Based on our set of analyses using the evLY, a threshold of $84,000 per evLY gained would be needed to maintain alignment with a threshold of $100,000 per added QALY. The evLY is a measure of health gain that can be used as an alternative or a complement to the QALY to address concerns related to undervaluing treatments that extend the life of individuals with serious illness or chronic disability. We recommend that it be reported within all cost-effectiveness analyses but may have special relevance in the current political environment in the USA, where use of the QALY is often challenged or prohibited.

Oral and monoclonal antibody treatments for relapsing forms of multiple sclerosis: Effectiveness and value.

DISCLOSURES: Ms McKenna, Dr Lin, Dr Whittington, Mr Nikitin, Ms Herron-Smith, Dr Campbell, and Dr Peterson report grants from Arnold Ventures, grants from Blue Cross Blue Shield of MA, grants from California Healthcare Foundation, grants from The Commonwealth Fund, and grants from The Peterson Center on Healthcare, during the conduct of the study; other from America's Health Insurance Plans, other from Anthem, other from AbbVie, other from Alnylam, other from AstraZeneca, other from Biogen, other from Blue Shield of CA, other from CVS, other from Editas, other from Express Scripts, other from Genentech/Roche, other from GlaxoSmithKline, other from Harvard Pilgrim, other from Health Care Service Corporation, other from Kaiser Permanente, other from LEO Pharma, other from Mallinckrodt, other from Merck, other from Novartis, other from National Pharmaceutical Council, other from Premera, other from Prime Therapeutics, other from Regeneron, other from Sanofi, other from United Healthcare, other from HealthFirst, other from Pfizer, other from Boehringer-Ingelheim, other from uniQure, other from Envolve Pharmacy Solutions, other from Humana, and other from Sun Life, outside the submitted work.

100 years of glucagon and 100 more.

The peptide hormone glucagon, discovered in late 1922, is secreted from pancreatic alpha cells and is an essential regulator of metabolic homeostasis. This review summarises experiences since the discovery of glucagon regarding basic and clinical aspects of this hormone and speculations on the future directions for glucagon biology and glucagon-based therapies. The review was based on the international glucagon conference, entitled 'A hundred years with glucagon and a hundred more', held in Copenhagen, Denmark, in November 2022. The scientific and therapeutic focus of glucagon biology has mainly been related to its role in diabetes. In type 1 diabetes, the glucose-raising properties of glucagon have been leveraged to therapeutically restore hypoglycaemia. The hyperglucagonaemia evident in type 2 diabetes has been proposed to contribute to hyperglycaemia, raising questions regarding underlying mechanism and the importance of this in the pathogenesis of diabetes. Mimicry experiments of glucagon signalling have fuelled the development of several pharmacological compounds including glucagon receptor (GCGR) antagonists, GCGR agonists and, more recently, dual and triple receptor agonists combining glucagon and incretin hormone receptor agonism. From these studies and from earlier observations in extreme cases of either glucagon deficiency or excess secretion, the physiological role of glucagon has expanded to also involve hepatic protein and lipid metabolism. The interplay between the pancreas and the liver, known as the liver-alpha cell axis, reflects the importance of glucagon for glucose, amino acid and lipid metabolism. In individuals with diabetes and fatty liver diseases, glucagon's hepatic actions may be partly impaired resulting in elevated levels of glucagonotropic amino acids, dyslipidaemia and hyperglucagonaemia, reflecting a new, so far largely unexplored pathophysiological phenomenon termed 'glucagon resistance'. Importantly, the hyperglucagonaemia as part of glucagon resistance may result in increased hepatic glucose production and hyperglycaemia. Emerging glucagon-based therapies show a beneficial impact on weight loss and fatty liver diseases and this has sparked a renewed interest in glucagon biology to enable further pharmacological pursuits.

The incretin co-agonist tirzepatide requires GIPR for hormone secretion from human islets.

The incretins glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide 1 (GLP-1) mediate insulin responses that are proportionate to nutrient intake to facilitate glucose tolerance1. The GLP-1 receptor (GLP-1R) is an established drug target for the treatment of diabetes and obesity2, whereas the therapeutic potential of the GIP receptor (GIPR) is a subject of debate. Tirzepatide is an agonist at both the GIPR and GLP-1R and is a highly effective treatment for type 2 diabetes and obesity3,4. However, although tirzepatide activates GIPR in cell lines and mouse models, it is not clear whether or how dual agonism contributes to its therapeutic benefit. Islet beta cells express both the GLP-1R and the GIPR, and insulin secretion is an established mechanism by which incretin agonists improve glycemic control5. Here, we show that in mouse islets, tirzepatide stimulates insulin secretion predominantly through the GLP-1R, owing to reduced potency at the mouse GIPR. However, in human islets, antagonizing GIPR activity consistently decreases the insulin response to tirzepatide. Moreover, tirzepatide enhances glucagon secretion and somatostatin secretion in human islets. These data demonstrate that tirzepatide stimulates islet hormone secretion from human islets through both incretin receptors.

Hypothalamic and brainstem glucose-dependent insulinotropic polypeptide receptor neurons employ distinct mechanisms to affect feeding.

Central glucose-dependent insulinotropic polypeptide (GIP) receptor (GIPR) signaling is critical in GIP-based therapeutics' ability to lower body weight, but pathways leveraged by GIPR pharmacology in the brain remain incompletely understood. We explored the role of Gipr neurons in the hypothalamus and dorsal vagal complex (DVC) - brain regions critical to the control of energy balance. Hypothalamic Gipr expression was not necessary for the synergistic effect of GIPR/GLP-1R coagonism on body weight. While chemogenetic stimulation of both hypothalamic and DVC Gipr neurons suppressed food intake, activation of DVC Gipr neurons reduced ambulatory activity and induced conditioned taste avoidance, while there was no effect of a short-acting GIPR agonist (GIPRA). Within the DVC, Gipr neurons of the nucleus tractus solitarius (NTS), but not the area postrema (AP), projected to distal brain regions and were transcriptomically distinct. Peripherally dosed fluorescent GIPRAs revealed that access was restricted to circumventricular organs in the CNS. These data demonstrate that Gipr neurons in the hypothalamus, AP, and NTS differ in their connectivity, transcriptomic profile, peripheral accessibility, and appetite-controlling mechanisms. These results highlight the heterogeneity of the central GIPR signaling axis and suggest that studies into the effects of GIP pharmacology on feeding behavior should consider the interplay of multiple regulatory pathways.

Pancreas-derived DPP4 is not essential for glucose homeostasis under metabolic stress.

Mice systemically lacking dipeptidyl peptidase-4 (DPP4) have improved islet health, glucoregulation, and reduced obesity with high-fat diet (HFD) feeding compared to wild-type mice. Some, but not all, of this improvement can be linked to the loss of DPP4 in endothelial cells (ECs), pointing to the contribution of non-EC types. The importance of intra-islet signaling mediated by α to ß cell communication is becoming increasingly clear; thus, our objective was to determine if ß cell DPP4 regulates insulin secretion and glucose tolerance in HFD-fed mice by regulating the local concentrations of insulinotropic peptides. Using ß cell double incretin receptor knockout mice, ß cell- and pancreas-specific Dpp4-/- mice, we reveal that ß cell incretin receptors are necessary for DPP4 inhibitor effects. However, although ß cell DPP4 modestly contributes to high glucose (16.7 mM)-stimulated insulin secretion in isolated islets, it does not regulate whole-body glucose homeostasis.