Prostaglandin EP3 Receptor signaling is required to prevent insulin hypersecretion and metabolic dysfunction in a non-obese mouse model of insulin resistance

When homozygous for the LeptinOb mutation (Ob), Black-and-Tan Brachyury (BTBR) mice become morbidly obese and severely insulin resistant, and by 10 weeks of age, frankly diabetic. Previous work has shown Prostaglandin EP3 Receptor (EP3) expression and activity is up-regulated in islets from BTBR-Ob mice as compared to lean controls, actively contributing to their beta-cell dysfunction. In this work, we aimed to test the impact of beta-cell-specific EP3 loss on the BTBR-Ob phenotype by crossing Ptger3 floxed mice with the Rat insulin promoter (RIP)-CreHerr driver strain. Instead, germline recombination of the floxed allele in the founder mouse - an event whose prevalence we identified as directly associated with underlying insulin resistance of the background strain - generated a full-body knockout. Full-body EP3 loss provided no diabetes protection to BTBR-Ob mice, but, unexpectedly, significantly worsened BTBR-lean insulin resistance and glucose tolerance. This in vivo phenotype was not associated with changes in beta-cell fractional area or markers of beta-cell replication ex vivo. Instead, EP3-null BTBR-lean islets had essentially uncontrolled insulin hypersecretion. The selective up-regulation of constitutively-active EP3 splice variants in islets from young, lean BTBR mice as compared to C57BL/6J, where no phenotype of EP3 loss has been observed, provides a potential explanation for the hypersecretion phenotype. In support of this, high islet EP3 expression in Balb/c females vs. Balb/c males was fully consistent with their sexually-dimorphic metabolic phenotype after loss of EP3-coupled Gαz protein. Taken together, our findings provide a new dimension to the understanding of EP3 as a critical brake on insulin secretion.

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1875-P: The Impact of Carbohydrate/Fat Intake Balance on Beta-Cell Dedifferentiation and Fatty Liver in Obese Mouse Model

Diabetes ◽

10.2337/db20-1875-p ◽

2020 ◽

Vol 69 (Supplement 1) ◽

pp. 1875-P ◽

Cited By ~ 2

Author(s):

EMI ISHIDA ◽

XIAO LEI ◽

EIJIRO YAMADA ◽

SHUICHI OKADA ◽

MASANOBU YAMADA

Keyword(s):

Mouse Model ◽

Beta Cell ◽

Fatty Liver ◽

Obese Mouse ◽

Fat Intake ◽

Cell Dedifferentiation ◽

The Impact

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Circulating Chemerin, Oxidative Stress, Inflammation and Insulin Resistance in Morbid Obesity

Revista de Chimie ◽

10.37358/rc.17.5.5601 ◽

2017 ◽

Vol 68 (5) ◽

pp. 1014-1018 ◽

Cited By ~ 1

Author(s):

Viviana Aursulesei ◽

Siminela Bulughiana ◽

Bogdan Alexandru Stoica ◽

Ecaterina Anisie

Keyword(s):

Oxidative Stress ◽

Insulin Resistance ◽

Morbid Obesity ◽

Independent Predictor ◽

Metabolic Phenotype ◽

Morbidly Obese ◽

Pathophysiological Role ◽

Obese Subjects ◽

Relationship Of ◽

The Relationship

Chemerin is a relatively novel adipokine with controversial pathophysiological role in obesity. Our study aimed to investigate the relationship of serum chemerin level with inflammation, oxidative stress and insulin resistance in morbidly obese subjects. Circulating chemerin was an independent predictor of TNF-Q level, superoxide dismutase activity and lipid peroxidation, but no relation with insulin resistance could be sustained. Taken together chemerin could be a marker of dysfunctional adipose tissue, but its serum level does not reflect properly the metabolic phenotype in morbid obesity.

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Understanding the Long-Lasting Effects of Fetal Nutrient Restriction versus Exposure to an Obesogenic Diet on Islet-Cell Mass and Function

Metabolites ◽

10.3390/metabo11080514 ◽

2021 ◽

Vol 11 (8) ◽

pp. 514

Author(s):

Stephanie E. O’Hara ◽

Kelly M. Gembus ◽

Lisa M. Nicholas

Keyword(s):

Beta Cell ◽

Beta Cell Function ◽

Cell Function ◽

Islet Cells ◽

Cell Mass ◽

Adult Life ◽

Metabolic Phenotype ◽

The Road ◽

Obesogenic Diet ◽

The Impact

Early life represents a window of phenotypic plasticity. Thus, exposure of the developing fetus to a compromised nutritional environment can have long term consequences for their health. Indeed, undernutrition or maternal intake of an obesogenic diet during pregnancy leads to a heightened risk of type 2 diabetes (T2D) and obesity in her offspring in adult life. Given that abnormalities in beta-cell function are crucial in delineating the risk of T2D, studies have investigated the impact of these exposures on islet morphology and beta-cell function in the offspring in a bid to understand why they are more at risk of T2D. Interestingly, despite the contrasting maternal metabolic phenotype and, therefore, intrauterine environment associated with undernutrition versus high-fat feeding, there are a number of similarities in the genes/biological pathways that are disrupted in offspring islets leading to changes in function. Looking to the future, it will be important to define the exact mechanisms involved in mediating changes in the gene expression landscape in islet cells to determine whether the road to T2D development is the same or different in those exposed to different ends of the nutritional spectrum.

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Liraglutide and sitagliptin counter beta- to alpha-cell transdifferentiation in diabetes

Journal of Endocrinology ◽

10.1530/joe-19-0451 ◽

2020 ◽

Vol 245 (1) ◽

pp. 53-64 ◽

Cited By ~ 2

Author(s):

Neil Tanday ◽

Peter R Flatt ◽

Nigel Irwin ◽

R Charlotte Moffett

Keyword(s):

Insulin Resistance ◽

Beta Cell ◽

Beta Cells ◽

Lineage Tracing ◽

Alpha Cell ◽

Beta Cell Destruction ◽

Glucose Levels ◽

Cell Destruction ◽

Cell Transdifferentiation ◽

The Impact

Transdifferentiation of beta- to alpha-cells has been implicated in the pathogenesis of diabetes. To investigate the impact of contrasting aetiologies of beta-cell stress, as well as clinically approved incretin therapies on this process, lineage tracing of beta-cells in transgenic Ins1 Cre/+/Rosa26-eYFP mice was investigated. Diabetes-like syndromes were induced by streptozotocin (STZ), high fat feeding (HFF) or hydrocortisone (HC), and effects of treatment with liraglutide or sitagliptin were investigated. Mice developed the characteristic metabolic features associated with beta-cell destruction or development of insulin resistance. Liraglutide was effective in preventing weight gain in HFF mice, with both treatments decreasing energy intake in STZ and HC mice. Treatment intervention also significantly reduced blood glucose levels in STZ and HC mice, as well as increasing either plasma or pancreatic insulin while decreasing circulating or pancreatic glucagon in all models. The recognised changes in pancreatic morphology induced by STZ, HFF or HC were partially, or fully, reversed by liraglutide and sitagliptin, and related to advantageous effects on alpha- and beta-cell growth and survival. More interestingly, induction of diabetes-like phenotype, regardless of pathogenesis, led to increased numbers of beta-cells losing their identity, as well as decreased expression of Pdx1 within beta-cells. Both treatment interventions, and especially liraglutide, countered detrimental islet cell transitioning effects in STZ and HFF mice. Only liraglutide imparted benefits on beta- to alpha-cell transdifferentiation in HC mice. These data demonstrate that beta- to alpha-cell transdifferentiation is a common consequence of beta-cell destruction or insulin resistance and that clinically approved incretin-based drugs effectively limit this.

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Local and Systemic Impact of Transcriptional Up-Regulation of 11β-Hydroxysteroid Dehydrogenase Type 1 in Adipose Tissue in Human Obesity

The Journal of Clinical Endocrinology & Metabolism ◽

10.1210/jc.2003-030286 ◽

2003 ◽

Vol 88 (8) ◽

pp. 3983-3988 ◽

Cited By ~ 154

Author(s):

Deborah J. Wake ◽

Eva Rask ◽

Dawn E. W. Livingstone ◽

Stefan Söderberg ◽

Tommy Olsson ◽

...

Keyword(s):

Insulin Resistance ◽

Adipose Tissue ◽

Ex Vivo ◽

Hydroxysteroid Dehydrogenase ◽

Mrna Levels ◽

Urinary Cortisol ◽

Cortisol Metabolism ◽

The Impact

In idiopathic obesity circulating cortisol levels are not elevated, but high intraadipose cortisol concentrations have been implicated. 11β-Hydroxysteroid dehydrogenase type 1 (11HSD1) catalyzes the conversion of inactive cortisone to active cortisol, thus amplifying glucocorticoid receptor (GR) activation. In cohorts of men and women, we have shown increased ex vivo 11HSD1 activity in sc adipose tissue associated with in vivo obesity and insulin resistance. Using these biopsies, we have now validated this observation by measuring 11HSD1 and GR mRNA and examined the impact on intraadipose cortisol concentrations, putative glucocorticoid regulated adipose target gene expression (angiotensinogen and leptin), and systemic measurements of cortisol metabolism. From aliquots of sc adipose biopsies from 16 men and 16 women we extracted RNA for real-time PCR and steroids for immunoassays. Adipose 11HSD1 mRNA was closely related to 11HSD1 activity [standardized β coefficient (SBC) = 0.58; P < 0.01], and both were positively correlated with parameters of obesity (e.g. for BMI, SBC = 0.48; P < 0.05 for activity, and SBC = 0.63; P < 0.01 for mRNA) and insulin sensitivity (log fasting plasma insulin; SBC = 0.44; P < 0.05 for activity, and SBC = 0.33; P = 0.09 for mRNA), but neither correlated with urinary cortisol/cortisone metabolite ratios. Adipose GR-α and angiotensinogen mRNA levels were not associated with obesity or insulin resistance, but leptin mRNA was positively related to 11HSD1 activity (SBC = 0.59; P < 0.05) and tended to be associated with parameters of obesity (BMI: SBC = 0.40; P = 0.09), fasting insulin (SBC = 0.65; P < 0.05), and 11HSD1 mRNA (SBC = 0.40; P = 0.15). Intraadipose cortisol (142 ± 30 nmol/kg) was not related to 11HSD1 activity or expression, but was positively correlated with plasma cortisol. These data confirm that idiopathic obesity is associated with transcriptional up-regulation of 11HSD1 in adipose, which is not detected by conventional in vivo measurements of urinary cortisol metabolites and is not accompanied by dysregulation of GR. Although this may drive a compensatory increase in leptin synthesis, whether it has an adverse effect on intraadipose cortisol concentrations and GR-dependent gene regulation remains to be established.

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A role for EP3 and its associated G protein, Gz, in negatively regulating beta-cell function and mass in the context of insulin resistance and obesity

10.1101/671289 ◽

2019 ◽

Author(s):

Austin Reuter ◽

Jaclyn A. Wisinski ◽

Darby Peter ◽

Michael D. Schaid ◽

Rachel J. Fenske ◽

...

Keyword(s):

Insulin Resistance ◽

Cell Proliferation ◽

Insulin Secretion ◽

Beta Cell ◽

G Protein ◽

Beta Cell Function ◽

Cell Function ◽

Beta Cell Proliferation ◽

Wild Type ◽

Full Body

AbstractObjectiveBlack and Tan Brachyury (BTBR) mice have underlying defects in insulin sensitivity and beta-cell function, even when lean. When homozygous for theLeptinObmutation (BTBR-Ob), hyperphagia leads to morbid obesity, and by 10 weeks of age, a type 2 diabetes (T2D) phenotype is fully penetrant. The second messenger molecule, cyclic AMP (cAMP), promotes glucose-stimulated and incretin-potentiated insulin secretion, beta-cell proliferation, and beta-cell survival. We have previously shown that a key player in the loss of functional beta-cell mass in the BTBR-Ob strain is Prostaglandin EP3 receptor (EP3); dysfunctionally up-regulated in the islet by the pathophysiological conditions of T2D. EP3 transmits a signal from its ligand, prostaglandin E2 (PGE2), to the unique cAMP-inhibitory G protein alpha-subunit, Gαz, reducing beta-cell cAMP production. Our objective in this study was to study the effect of beta-cell EP3 and Gαzloss on the metabolic phenotype of both BTBR-lean and -Ob mice, providing support for targeting this pathway in a genetically-susceptible population before and after the progression to frank T2D.MethodsEP3 or Gαz-floxed BTBR mice were bred with BTBR mice expressing Cre recombinase under the control of the rat insulin promoter in order to design beta-cell-specific knockout mice. A final cross into the BTBR-Ob strain provided both lean and obese experimental animals. To our surprise, the EP3 deleted allele was transferred via the germline, making full-body EP3-null mice, as confirmed by qPCR. Beta-cell-specific Gαzloss in Gαz-flox-RIP-Cre mice (GαzβKO) was confirmed; yet, these mice were poor breeders, particularly in the context of theLeptinObmutation; therefore, only BTBR-lean mice were phenotyped. Full-body metabolic and ex vivo islet assays were conducted in wild-type and EP3-null BTBR-lean and Ob mice and wild-type and GαzβKO BTBR-lean mice, linking any islet phenotype with observed effects on glucose homeostasis.ResultsSystemic EP3 loss accelerated the early T2D phenotype of BTBR-Ob mice and caused insulin resistance and glucose intolerance in BTBR-lean mice, likely due to the extra-pancreatic effects described previously in other mouse models. Even so, islets from EP3-null BTBR-Ob mice had significantly increased insulin-positive pancreas area, supportive of an increased proliferation response. GαzβKO BTBR-lean mice, on the other hand, had significantly improved glucose tolerance due to elevated glucose-stimulated and incretin-potentiated insulin secretion, with no apparent effect of beta-cell Gαzloss on beta-cell proliferation. Combined, our findings suggest a divergence in signaling downstream of EP3/Gαzdepending on the (patho)physiologic conditions to which the islet is exposed.ConclusionsOur work sheds light on G protein-mediated mechanisms by which beta-cells compensate for systemic insulin resistance and how these become dysfunctional in the T2D state.

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Meal Timing-Based Dietary Patterns Are Associated With Glucose Regulation, Insulin Resistance, and Incretin Effect in Individuals at Risk for Type 2 Diabetes

Current Developments in Nutrition ◽

10.1093/cdn/nzab039_008 ◽

2021 ◽

Vol 5 (Supplement_2) ◽

pp. 472-472

Author(s):

Heyjun Park ◽

Ahmed Metwally ◽

Dalia Perelman ◽

Alessandra Celli ◽

Susan Kirkpatrick ◽

...

Keyword(s):

Insulin Resistance ◽

Beta Cell ◽

Glucose Homeostasis ◽

Dietary Patterns ◽

Beta Cell Function ◽

Cell Function ◽

Energy Contribution ◽

Meal Timing ◽

Study Participants ◽

The Impact

Abstract Objectives Food is an external cue to entrain the circadian rhythm, and when and how to eat may be a crucial factor for glucose homeostasis. This study sought to quantify the impact of meal timing-based dietary habits on glucose homeostasis in prediabetic and normal individuals by using digital monitoring technologies. Methods 35 study participants (56.6 y; prediabetes n = 19 and normoglycemia n = 16) tracked their food intake and timing by a food-logging mobile app for at least two weeks. Gold-standard glucose metabolic tests were performed such as OGTT, insulin suppression test, and isoglycemic intravenous glucose infusion to quantify insulin resistance, beta-cell function, and incretin effects. The energy contribution of six meal timings to the total daily energy intake was determined. Principal component analysis (PCA) was used to group participants in the cohort based on their meal timing patterns. Multivariate linear regression (MLR) models confirmed differences in each meal timing feature by glycemic control groups. Results A total of 2307 meals and 625 days of food logs were collected from study participants. From the PCA plot based on meal timing features, the cohort was clearly separated into two clusters by their HbA1c levels: normoglycemia (HbA1c < 5.7%) vs. prediabetes (5.7%< HbA1c < 6.5%). MLR models further showed that people with prediabetes had lower Meal_4 (2pm-5pm) energy contribution (P = 0.00,697) and higher Meal_5 (5pm-9pm) energy contribution (P = 0.0462) than normal group even after adjustment for age, sex, ethnicity, and BMI. Similarly, insulin resistant and sensitive groups were separated based on meal timing features, as did incretin function. However, beta-cell function groups were not distinguished by meal timing features. Conclusions The data suggest that meal timing-based dietary patterns can be used to predict different types of glucose metabolic dysregulation such as prolonged high blood glucose, insulin resistance, and incretin dysfunction. Funding Sources NIH 2T32HL09804911, NIH 5R01DK110186-02, Stanford PHIND Award.

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EP3 signaling is decoupled from regulation of glucose-stimulated insulin secretion in β-cells compensating for obesity and insulin resistance

10.1101/2020.07.10.197863 ◽

2020 ◽

Author(s):

Michael D. Schaid ◽

Jeffrey M. Harrington ◽

Grant M. Kelly ◽

Sophia M. Sdao ◽

Matthew J. Merrins ◽

...

Keyword(s):

Insulin Resistance ◽

Type 2 Diabetes ◽

Insulin Secretion ◽

Beta Cell ◽

Duty Cycle ◽

Β Cell ◽

Inhibitory G Protein ◽

Glucose Stimulated Insulin Secretion ◽

Ep3 Receptor

ABSTRACTOf the β-cell signaling pathways altered by non-diabetic obesity and insulin resistance, some are adaptive while others actively contribute to β-cell failure and demise. Cytoplasmic calcium (Ca2+) and cyclic AMP (cAMP), which control the timing and amplitude of insulin secretion, are two important signaling intermediates that can be controlled by stimulatory and inhibitory G protein-coupled receptors. Previous work has shown the importance of the cAMP-inhibitory EP3 receptor in the beta-cell dysfunction of type 2 diabetes. To examine alterations in β-cell cAMP during diabetes progression we utilized a β-cell specific cAMP biosensor in tandem with islet Ca2+ recordings and insulin secretion assays. Three groups of C57BL/6J mice were used as a model of the progression from metabolic health to type 2 diabetes: wildtype, normoglycemic LeptinOb, and hyperglycemic LeptinOb. Here, we report robust increases in β-cell cAMP and insulin secretion responses in normoglycemic Leptinob mice as compared to wild-type: an effect that was lost in islets from hyperglycemic Leptinob mice, despite elevated Ca2+ duty cycle. Yet, the correlation of EP3 expression and activity to reduce cAMP levels and Ca2+ duty cycle with reduced insulin secretion only held true in hyperglycemic LeptinOb mice. Our results suggest alterations in beta-cell EP3 signaling may be both adaptive and maladaptive and define β-cell EP3 signaling as much more nuanced than previously understood.

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