The prostaglandin E EP3 receptor has disparate effects on islet insulin secretion and content in β-cells in a high-fat diet-induced mouse model of obesity.

Signaling through prostaglandin E EP3 receptor (EP3) actively contributes to the β-cell dysfunction of type 2 diabetes (T2D). In T2D models, full-body EP3 knockout mice have a significantly worse metabolic phenotype than wild-type controls due to hyperphagia and severe insulin resistance resulting from loss of EP3 in extra-pancreatic tissues, masking any potential beneficial effects of EP3 loss in the β cell. We hypothesized β-cell-specific EP3 knockout (EP3 βKO) mice would be protected from high-fat diet (HFD)-induced glucose intolerance, phenocopying mice lacking the EP3 effector, Gα, which is much more limited in its tissue distribution.

Diazobutanone-assisted isobaric labelling of phospholipids and sulfated glycolipids enables multiplexed quantitative lipidomics using tandem mass spectrometry.

Mass spectrometry-based quantitative lipidomics is an emerging field aiming to uncover the intricate relationships between lipidomes and disease development. However, quantifying lipidomes comprehensively in a high-throughput manner remains challenging owing to the diverse lipid structures. Here we propose a diazobutanone-assisted isobaric labelling strategy as a rapid and robust platform for multiplexed quantitative lipidomics across a broad range of lipid classes, including various phospholipids and glycolipids.

What the BTBR/J mouse has taught us about diabetes and diabetic complications.

Human and mouse genetics have delivered numerous diabetogenic loci, but it is mainly through the use of animal models that the pathophysiological basis for their contribution to diabetes has been investigated. More than 20 years ago, we serendipidously identified a mouse strain that could serve as a model of obesity-prone type 2 diabetes, the BTBR (Black and Tan Brachyury) mouse (BTBR T+ Itpr3tf/J, 2018) carrying the mutation. We went on to discover that the BTBR- mouse is an excellent model of diabetic nephropathy and is now widely used by nephrologists in academia and the pharmaceutical industry.

A plasma membrane-associated glycolytic metabolon is functionally coupled to K channels in pancreatic α and β cells from humans and mice.

The ATP-sensitive K (K) channel is a key regulator of hormone secretion from pancreatic islet endocrine cells. Using direct measurements of K channel activity in pancreatic β cells and the lesser-studied α cells, from both humans and mice, we provide evidence that a glycolytic metabolon locally controls K channels on the plasma membrane. The two ATP-consuming enzymes of upper glycolysis, glucokinase and phosphofructokinase, generate ADP that activates K.

Metformin Monotherapy Alters the Human Plasma Lipidome Independent of Clinical Markers of Glycemic Control and Cardiovascular Disease Risk in a Type 2 Diabetes Clinical Cohort.

Type 2 diabetes (T2D) is a rising pandemic worldwide. Diet and lifestyle changes are typically the first intervention for T2D. When this intervention fails, the biguanide metformin is the most common pharmaceutical therapy.

Plasma Prostaglandin E Metabolite Levels Predict Type 2 Diabetes Status and One-Year Therapeutic Response Independent of Clinical Markers of Inflammation.

Over half of patients with type 2 diabetes (T2D) are unable to achieve blood glucose targets despite therapeutic compliance, significantly increasing their risk of long-term complications. Discovering ways to identify and properly treat these individuals is a critical problem in the field. The arachidonic acid metabolite, prostaglandin E (PGE), has shown great promise as a biomarker of β-cell dysfunction in T2D.

Islet allografts expressing a PD-L1 and IDO fusion protein evade immune rejection and reverse preexisting diabetes in immunocompetent mice without systemic immunosuppression.

Allogeneic islet transplantation is a promising experimental therapy for poorly controlled diabetes. Despite pharmacological immunosuppression, long-term islet engraftment remains elusive. Here, we designed a synthetic fusion transgene coupling PD-L1 and indoleamine dioxygenase [hereafter PIDO] whose constitutive expression prevents immune destruction of genetically engineered islet allograft transplanted in immunocompetent mice.

Cholecystokinin attenuates β-cell apoptosis in both mouse and human islets.

Loss of functional pancreatic β-cell mass and increased β-cell apoptosis are fundamental to the pathophysiology of type 1 and type 2 diabetes. Pancreatic islet transplantation has the potential to cure type 1 diabetes but is often ineffective due to the death of the islet graft within the first few years after transplant. Therapeutic strategies to directly target pancreatic β-cell survival are needed to prevent and treat diabetes and to improve islet transplant outcomes.

TCF19 Impacts a Network of Inflammatory and DNA Damage Response Genes in the Pancreatic β-Cell.

Transcription factor 19 (TCF19) is a gene associated with type 1 diabetes (T1DM) and type 2 diabetes (T2DM) in genome-wide association studies. Prior studies have demonstrated that Tcf19 knockdown impairs β-cell proliferation and increases apoptosis. However, little is known about its role in diabetes pathogenesis or the effects of TCF19 gain-of-function.

Human Islet Expression Levels of Prostaglandin E Synthetic Enzymes, But Not Prostaglandin EP3 Receptor, Are Positively Correlated with Markers of β-Cell Function and Mass in Nondiabetic Obesity.

Elevated islet production of prostaglandin E (PGE), an arachidonic acid metabolite, and expression of prostaglandin E receptor subtype EP3 (EP3) are well-known contributors to the β-cell dysfunction of type 2 diabetes (T2D). Yet, many of the same pathophysiological conditions exist in obesity, and little is known about how the PGE production and signaling pathway influences nondiabetic β-cell function. In this work, plasma arachidonic acid and PGE metabolite levels were quantified in a cohort of nondiabetic and T2D human subjects to identify their relationship with glycemic control, obesity, and systemic inflammation.

The influence of intermittent hypoxia, obesity, and diabetes on male genitourinary anatomy and voiding physiology.

We used male BTBR mice carrying the mutation, which are subject to severe and progressive obesity and diabetes beginning at 6 wk of age, to examine the influence of one specific manifestation of sleep apnea, intermittent hypoxia (IH), on male urinary voiding physiology and genitourinary anatomy. A custom device was used to deliver continuous normoxia (control) or IH to wild-type and (mutant) mice for 2 wk. IH was delivered during the 12-h inactive (light) period in the form of 90 s of 6% O followed by 90 s of room air.

PREVENT: A Randomized, Placebo-controlled Crossover Trial of Avexitide for Treatment of Postbariatric Hypoglycemia.

Context: Postbariatric hypoglycemia (PBH), characterized by enteroinsular axis overstimulation and hyperinsulinemic hypoglycemia, is a complication of bariatric surgery for which there is no approved therapy.

Objective: To evaluate efficacy and safety of avexitide [exendin (9-39)], a glucagon-like peptide-1 antagonist, for treatment of PBH.

Methods: A multicenter, Phase 2, randomized, placebo-controlled crossover study (PREVENT).

Systemic Metabolic Alterations Correlate with Islet-Level Prostaglandin E Production and Signaling Mechanisms That Predict β-Cell Dysfunction in a Mouse Model of Type 2 Diabetes.

The transition from β-cell compensation to β-cell failure is not well understood. Previous works by our group and others have demonstrated a role for Prostaglandin EP3 receptor (EP3), encoded by the gene, in the loss of functional β-cell mass in Type 2 diabetes (T2D). The primary endogenous EP3 ligand is the arachidonic acid metabolite prostaglandin E (PGE).

Pyruvate Kinase Controls Signal Strength in the Insulin Secretory Pathway.

Pancreatic β cells couple nutrient metabolism with appropriate insulin secretion. Here, we show that pyruvate kinase (PK), which converts ADP and phosphoenolpyruvate (PEP) into ATP and pyruvate, underlies β cell sensing of both glycolytic and mitochondrial fuels. Plasma membrane-localized PK is sufficient to close K channels and initiate calcium influx.

Ultrahigh-Resolution Mass Spectrometry-Based Platform for Plasma Metabolomics Applied to Type 2 Diabetes Research.

Metabolomics-the endpoint of the omics cascade-is increasingly recognized as a preferred method for understanding the ultimate responses of biological systems to stress. Flow injection electrospray (FIE) mass spectrometry (MS) has advantages for untargeted metabolic fingerprinting due to its simplicity and capability for high-throughput screening but requires a high-resolution mass spectrometer to resolve metabolite features. In this study, we developed and validated a high-throughput and highly reproducible metabolomics platform integrating FIE with ultrahigh-resolution Fourier transform ion cyclotron resonance (FTICR) MS for analysis of both polar and nonpolar metabolite features from plasma samples.

Differential Expression of Ormdl Genes in the Islets of Mice and Humans with Obesity.

The orosomucoid-like (Ormdl) proteins play a critical role in sphingolipid homeostasis, inflammation, and ER stress, all of which are associated with obesity and βcell dysfunction. However, their roles in β cells and obesity remain unknown. Here, we show that islets from overweight/obese human donors displayed marginally reduced ORMDL1-2 expression, whereas ORMDL3 expression was significantly downregulated compared with islets from lean donors.

Intra-islet GLP-1, but not CCK, is necessary for β-cell function in mouse and human islets.

Glucagon-like peptide 1 (GLP-1) and cholecystokinin (CCK) are gut-derived peptide hormones known to play important roles in the regulation of gastrointestinal motility and secretion, appetite, and food intake. We have previously demonstrated that both GLP-1 and CCK are produced in the endocrine pancreas of obese mice. Interestingly, while GLP-1 is well known to stimulate insulin secretion by the pancreatic β-cells, direct evidence of CCK promoting insulin release in human islets remains to be determined.

Roux en Y gastric bypass hypoglycemia resolves with gastric feeding or reversal: Confirming a non-pancreatic etiology.

Objective: Postprandial hypoglycemia is an infrequent but disabling complication of Roux-en-Y gastric bypass (RYGB) surgery. Controversy still exists as to whether the postprandial hyperinsulinemia observed is due to inherent changes in pancreatic β-cell mass or function or to reversible alterations caused by RYGB anatomy. We aimed to determine if gastric feeding or reversal of RYGB would normalize postprandial glucose and hormone excursions in patients with symptomatic hypoglycemia.

Interleukin 6 protects pancreatic β cells from apoptosis by stimulation of autophagy.

IL-6 is a pleiotropic cytokine with complex roles in inflammation and metabolic disease. The role of IL-6 as a pro- or anti-inflammatory cytokine is still unclear. Within the pancreatic islet, IL-6 stimulates secretion of the prosurvival incretin hormone glucagon-like peptide 1 (GLP-1) by α cells and acts directly on β cells to stimulate insulin secretion Uncovering physiologic mechanisms promoting β-cell survival under conditions of inflammation and stress can identify important pathways for diabetes prevention and treatment.

Enriching Islet Phospholipids With Eicosapentaenoic Acid Reduces Prostaglandin E Signaling and Enhances Diabetic β-Cell Function.

Prostaglandin E (PGE) is derived from arachidonic acid, whereas PGE is derived from eicosapentaenoic acid (EPA) using the same downstream metabolic enzymes. Little is known about the impact of EPA and PGE on β-cell function, particularly in the diabetic state. In this work, we determined that PGE elicits a 10-fold weaker reduction in glucose-stimulated insulin secretion through the EP3 receptor as compared with PGE We tested the hypothesis that enriching pancreatic islet cell membranes with EPA, thereby reducing arachidonic acid abundance, would positively impact β-cell function in the diabetic state.

Successful in vitro fertilization and generation of transgenics in Black and Tan Brachyury (BTBR) mice.

The Black and Tan Brachyury (BTBR) mouse strain is a valuable model for the study of long-term complications from obesity-induced type 2 diabetes mellitus and autism spectrum disorder. Due to technical difficulties with assisted reproduction, genetically modified animals on this background have previously been generated through extensive backcrossing, which is expensive and time-consuming. We successfully generated two separate transgenic mouse lines after direct zygote microinjection into this background strain.

Glucagon-like peptide-1 and cholecystokinin production and signaling in the pancreatic islet as an adaptive response to obesity.

Precise control of blood glucose is dependent on adequate β-cell mass and function. Thus, reductions in β-cell mass and function lead to insufficient insulin production to meet demand, and result in diabetes. Recent evidence suggests that paracrine signaling in the islet might be important in obesity, and disruption of this signaling could play a role in the pathogenesis of diabetes.

The Importance of Exclusion of Obstructive Sleep Apnea During Screening for Adrenal Adenoma and Diagnosis of Pheochromocytoma.

Context. As catecholamine elevation is a key element in the diagnosis of pheochromocytoma, more commonplace causes of sympathetic excess, such as obstructive sleep apnea (OSA), should be excluded as standard practice prior to diagnosis. This is essential to avoid misdiagnosis of adrenal incidentalomas identified in the estimated 42 million Americans with OSA, with greater than 4 million projected to undergo a computed tomography study annually.