Rosiglitazone Promotes PPARγ-Dependent and -Independent Alterations in Gene Expression in Mouse Islets

Abstract The glitazone class of insulin-sensitizing agents act, in part, by the activation of peroxisome proliferator-activated receptor (PPAR)-γ in adipocytes. However, it is unclear whether the expression of PPARγ in the islets is essential for their potential β-cell-sparing properties. To investigate the in vivo effects of rosiglitazone on β-cell biology, we used an inducible, pancreatic and duodenal homeobox-1 enhancer element-driven, Cre recombinase to knockout PPARγ expression specifically in adult β-cells (PPARgKO). Subjecting the PPARgKO mice to a chow diet led to virtually undetectable changes in glucose or insulin sensitivity, which was paralleled by minimal changes in islet gene expression. Similarly, challenging the mutant mice with a high-fat diet and treatment with rosiglitazone did not alter insulin sensitivity, glucose-stimulated insulin secretion, islet size, or proliferation in the knockout mice despite PPARγ-dependent and -independent changes in islet gene expression. These data suggest that PPARγ expression in the β-cells is unlikely to be directly essential for normal β-cell function or the insulin-sensitizing actions of rosiglitazone.

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Pericytes contribute to the islet basement membranes to promote beta-cell gene expression

Scientific Reports ◽

10.1038/s41598-021-81774-8 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Lina Sakhneny ◽

Alona Epshtein ◽

Limor Landsman

Keyword(s):

Gene Expression ◽

Cell Function ◽

Basement Membranes ◽

Cell Physiology ◽

Β Cells ◽

Β Cell ◽

Cell Clustering ◽

Β Cell Function ◽

Cell Gene Expression ◽

Glucose Stimulated Insulin Secretion

Abstractβ-Cells depend on the islet basement membrane (BM). While some islet BM components are produced by endothelial cells (ECs), the source of others remains unknown. Pancreatic pericytes directly support β-cells through mostly unidentified secreted factors. Thus, we hypothesized that pericytes regulate β-cells through the production of BM components. Here, we show that pericytes produce multiple components of the mouse pancreatic and islet interstitial and BM matrices. Several of the pericyte-produced ECM components were previously implicated in β-cell physiology, including collagen IV, laminins, proteoglycans, fibronectin, nidogen, and hyaluronan. Compared to ECs, pancreatic pericytes produce significantly higher levels of α2 and α4 laminin chains, which constitute the peri-islet and vascular BM. We further found that the pericytic laminin isoforms differentially regulate mouse β-cells. Whereas α2 laminins promoted islet cell clustering, they did not affect gene expression. In contrast, culturing on Laminin-421 induced the expression of β-cell genes, including Ins1, MafA, and Glut2, and significantly improved glucose-stimulated insulin secretion. Thus, alongside ECs, pericytes are a significant source of the islet BM, which is essential for proper β-cell function.

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The effects of aging on male mouse pancreatic β-cell function involve multiple events in the regulation of secretion: influence of insulin sensitivity

The Journals of Gerontology Series A ◽

10.1093/gerona/glab276 ◽

2021 ◽

Author(s):

Eva Tudurí ◽

Sergi Soriano ◽

Lucía Almagro ◽

Anabel García-Heredia ◽

Alex Rafacho ◽

...

Keyword(s):

Insulin Secretion ◽

Insulin Sensitivity ◽

Cell Function ◽

Aged Mouse ◽

Β Cells ◽

Β Cell ◽

Peripheral Insulin Sensitivity ◽

Increased Risk ◽

Β Cell Function ◽

Effects Of Aging

Abstract Aging is associated with a decline in peripheral insulin sensitivity and an increased risk of impaired glucose tolerance and type 2 diabetes. During conditions of reduced insulin sensitivity, pancreatic β-cells undergo adaptive responses to increase insulin secretion and maintain euglycemia. However, the existence and nature of β-cell adaptations and/or alterations during aging are still a matter of debate. In this study, we investigated the effects of aging on β-cell function from control (3-month-old) and aged (20-month-old) mice. Aged animals were further categorized in two groups: high insulin sensitive (aged-HIS) and low insulin sensitive (aged-LIS). Aged-LIS mice were hyperinsulinemic, glucose intolerant and displayed impaired glucose-stimulated insulin and C-peptide secretion, whereas aged-HIS animals showed characteristics in glucose homeostasis similar to controls. In isolated β-cells, we observed that glucose-induced inhibition of KATP channel activity was reduced with aging, particularly in the aged-LIS group. Glucose-induced islet NAD(P)H production was decreased in aged mice, suggesting impaired mitochondrial function. In contrast, voltage-gated Ca 2+ currents were higher in aged-LIS β-cells, and pancreatic islets of both aged groups displayed increased glucose-induced Ca 2+ signaling and augmented insulin secretion compared with controls. Morphological analysis of pancreas sections also revealed augmented β-cell mass with aging, especially in the aged-LIS group, as well as ultrastructural β-cell changes. Altogether, these findings indicate that aged mouse β-cells compensate for the aging-induced alterations in the stimulus-secretion coupling, particularly by adjusting their Ca 2+ influx to ensure insulin secretion. These results also suggest that decreased peripheral insulin sensitivity exacerbates the effects of aging on β-cells.

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Effects of c-MYC activation on glucose stimulus-secretion coupling events in mouse pancreatic islets

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.90235.2008 ◽

2008 ◽

Vol 295 (1) ◽

pp. E92-E102 ◽

Cited By ~ 14

Author(s):

Séverine M. A. Pascal ◽

Yves Guiot ◽

Stella Pelengaris ◽

Michael Khan ◽

Jean-Christophe Jonas

Keyword(s):

Gene Expression ◽

Cell Survival ◽

Cell Function ◽

Tamoxifen Treatment ◽

Insulin Content ◽

Wild Type ◽

Β Cells ◽

Β Cell ◽

Membrane Hyperpolarization ◽

Stimulus Secretion Coupling

Alteration of pancreatic β-cell survival and Preproinsulin gene expression by prolonged hyperglycemia may result from increased c-MYC expression. However, it is unclear whether c-MYC effects on β-cell function are compatible with its proposed role in glucotoxicity. We therefore tested the effects of short-term c-MYC activation on key β-cell stimulus-secretion coupling events in islets isolated from mice expressing a tamoxifen-switchable form of c-MYC in β-cells (MycER) and their wild-type littermates. Tamoxifen treatment of wild-type islets did not affect their cell survival, Preproinsulin gene expression, and glucose stimulus-secretion coupling. In contrast, tamoxifen-mediated c-MYC activation for 2–3 days triggered cell apoptosis and decreased Preproinsulin gene expression in MycER islets. These effects were accompanied by mitochondrial membrane hyperpolarization at all glucose concentrations, a higher resting intracellular calcium concentration ([Ca2+]i), and lower glucose-induced [Ca2+]i rise and islet insulin content, leading to a strong reduction of glucose-induced insulin secretion. Compared with these effects, 1-wk culture in 30 mmol/l glucose increased the islet sensitivity to glucose stimulation without reducing the maximal glucose effectiveness or the insulin content. In contrast, overnight exposure to a low H2O2 concentration increased the islet resting [Ca2+]i and reduced the amplitude of the maximal glucose response as in tamoxifen-treated MycER islets. In conclusion, c-MYC activation rapidly stimulates apoptosis, reduces Preproinsulin gene expression and insulin content, and triggers functional alterations of β-cells that are better mimicked by overnight exposure to a low H2O2 concentration than by prolonged culture in high glucose.

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Neuromedin U uses Gαi2 and Gαo to suppress glucose-stimulated Ca2+ signaling and insulin secretion in pancreatic β cells

PLoS ONE ◽

10.1371/journal.pone.0250232 ◽

2021 ◽

Vol 16 (4) ◽

pp. e0250232

Author(s):

Weidong Zhang ◽

Hideyuki Sakoda ◽

Yuki Nakazato ◽

Md Nurul Islam ◽

François Pattou ◽

...

Keyword(s):

Insulin Secretion ◽

Er Stress ◽

Cell Biology ◽

Molecular Mechanisms ◽

Cell Function ◽

Mitochondrial Dynamics ◽

Intracellular Camp ◽

Β Cells ◽

Β Cell ◽

Signaling Mechanism

Neuromedin U (NMU), a highly conserved peptide in mammals, is involved in a wide variety of physiological processes, including impairment of pancreatic β-cell function via induction of mitochondrial dysfunction and endoplasmic reticulum (ER) stress, ultimately suppressing insulin secretion. NMU has two receptors, NMU receptor 1 (NMUR1) and NMUR2, both of which are G-protein–coupled receptors (GPCRs). Only NMUR1 is expressed in mouse islets and β cell–derived MIN6-K8 cells. The molecular mechanisms underlying the insulinostatic action mediated by NMUR1 in β cells have yet to be elucidated. In this study, we explored the molecular mechanism driving impairment of insulin secretion in β cells by the NMU–NMUR1 axis. Pretreatment with the Gαi/o inhibitor Bordetella pertussis toxin (PTX), but not the Gαq inhibitor YM254890, abolished NMU-induced suppression of glucose-stimulated insulin secretion and calcium response in β cells. Knockdown of Gαi2 and Gαo in β cells counteracted NMU-induced suppression of insulin secretion and gene alterations related to mitochondrial fusion (Mfn1, Mfn2), fission (Fis1, Drp1), mitophagy (Pink1, Park2), mitochondrial dynamics (Pgc-1α, Nrf1, and Tfam), ER stress (Chop, Atp2a3, Ryr2, and Itpr2), intracellular ATP level, and mitochondrial membrane potential. NMU decreased forskolin-stimulated intracellular cAMP in both mouse and human islets. We concluded that NMUR1 coupled to PTX-sensitive Gαi2 and Gαo proteins in β cells reduced intracellular Ca2+ influx and cAMP level, thereby causing β-cell dysfunction and impairment. These results highlight a novel signaling mechanism of NMU and provide valuable insights into the further investigation of NMU functions in β-cell biology.

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Addition of olive oil to diet of rats with mild pre-gestational diabetes impacts offspring β-cell development

Journal of Endocrinology ◽

10.1530/joe-20-0047 ◽

2020 ◽

Vol 246 (2) ◽

pp. 175-187

Author(s):

Bushra Taqui ◽

Farzad Asadi ◽

Evangelina Capobianco ◽

Daniel Barry Hardy ◽

Alicia Jawerbaum ◽

...

Keyword(s):

Oleic Acid ◽

Gestational Diabetes ◽

Olive Oil ◽

Metabolic Diseases ◽

Cell Mass ◽

Male Offspring ◽

Chow Diet ◽

Peroxisome Proliferator ◽

Β Cells ◽

Β Cell

Maternal diabetes impairs fetal development and increases the risk of metabolic diseases in the offspring. Previously, we demonstrated that maternal dietary supplementation with 6% of olive oil prevents diabetes-induced embryo and fetal defects, in part, through the activation of peroxisome proliferator-activated receptors (PPARs). In this study, we examined the effects of this diet on neonatal and adult pancreatic development in male and female offspring of mothers affected with pre-gestational diabetes. A mild diabetic model was developed by injecting neonatal rats with streptozotocin (90 mg/kg). During pregnancy, these dams were fed a chow diet supplemented or not with 6% olive oil. Offspring pancreata was examined at day 2 and 5 months of age by immunohistochemistry followed by morphometric analysis to determine number of islets, α and β cell clusters and β-cell mass. At 5 months, male offspring of diabetic mothers had reduced β-cell mass that was prevented by maternal supplementation with olive oil. PPARα and PPARγ were localized mainly in α cells and PPARβ/δ in both α and β cells. Although Pparβ/δ and Pparγ RNA expression showed reduction in 5-month-old male offspring of diabetic rats, Pparβ/δ expression returned to control levels after olive-oil supplementation. Interestingly, in vitro exposure to oleic acid (major component of olive oil) and natural PPAR agonists such as LTB4, CPC and 15dPGJ2 also significantly increased expression of all Ppars in αTC1–6 cells. However, only oleic acid and 15dPGJ2 increased insulin and Pdx-1 expression in INS-1E cells suggesting a protective role in β-cells. Olive oil may be considered a dietary supplement to improve islet function in offspring of affected mothers with pre-gestational diabetes.

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STAT3 Regulates Mitochondrial Gene Expression in Pancreatic β-Cells and its Deficiency Induces Glucose Intolerance in Obesity

10.2337/figshare.14831049.v1 ◽

2021 ◽

Author(s):

Anaïs Schaschkow ◽

Lokman Pang ◽

Valerie Vandenbempt ◽

Bernat Elvira ◽

Sara A. Litwak ◽

...

Keyword(s):

Gene Expression ◽

Glucose Intolerance ◽

High Fat Diet ◽

Cell Function ◽

Mitochondrial Gene ◽

High Fat ◽

Β Cells ◽

Β Cell ◽

Β Cell Function ◽

Deficient Mice

Most obese and insulin-resistant individuals do not develop diabetes. This is the result of the capacity of β-cells to adapt and produce enough insulin to cover the needs of the organism. The underlying mechanism of β-cell adaptation in obesity, however, remains unclear. Previous studies have suggested a role for STAT3 in mediating β-cell development and human glucose homeostasis, but little is known about STAT3 in β-cells in obesity. We observed enhanced cytoplasmic expression of STAT3 in severely obese and diabetic subjects. To address the functional role of STAT3 in adult β-cells, we generated mice with tamoxifen-inducible partial or full deletion of STAT3 in β-cells and fed them a high-fat diet before analysis. Interestingly, β-cell heterozygous and homozygous STAT3-deficient mice showed glucose intolerance when fed a high-fat diet. Gene expression analysis by RNA-Seq showed reduced expression of mitochondrial genes in STAT3 knocked down human EndoC-βH1 cells and was confirmed in FACS-purified β-cells from obese STAT3-deficient mice. Moreover, silencing of STAT3 impaired mitochondria activity in EndoC-βH1 cells and human islets, suggesting a mechanism for STAT3-modulated β-cell function. We propose STAT3 as a regulator of β-cell function, improving glucose-induced insulin secretion in obesity.

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Single-Cell RNAseq Reveals That Pancreatic β-Cells From Very Old Male Mice Have a Young Gene Signature

Endocrinology ◽

10.1210/en.2016-1235 ◽

2016 ◽

Vol 157 (9) ◽

pp. 3431-3438 ◽

Cited By ~ 15

Author(s):

Yurong Xin ◽

Haruka Okamoto ◽

Jinrang Kim ◽

Min Ni ◽

Christina Adler ◽

...

Keyword(s):

Gene Expression ◽

Single Cell ◽

Cell Function ◽

Functional Decline ◽

Cell Mass ◽

Gene Signature ◽

Β Cells ◽

Β Cell ◽

Very Old ◽

Old Mice

Aging improves pancreatic β-cell function in mice. This is a surprising finding because aging is typically associated with functional decline. We performed single-cell RNA sequencing of β-cells from 3- and 26-month-old mice to explore how changes in gene expression contribute to improved function with age. The old mice were healthy and had reduced blood glucose levels and increased β-cell mass, which correlated to their body weight. β-Cells from young and old mice had similar transcriptome profiles. In fact, only 193 genes (0.89% of all detected genes) were significantly regulated (≥2-fold; false discovery rate < 0.01; normalized counts > 5). Of these, 183 were down-regulated and mainly associated with pathways regulating gene expression, cell cycle, cell death, and survival as well as cellular movement, function, and maintenance. Collectively our data show that β-cells from very old mice have transcriptome profiles similar to those of young mice. These data support previous findings that aging is not associated with reduced β-cell mass or functional β-cell decline in mice.

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Targeted Elimination of Peroxisome Proliferator-Activated Receptor γ in β Cells Leads to Abnormalities in Islet Mass without Compromising Glucose Homeostasis

Molecular and Cellular Biology ◽

10.1128/mcb.23.20.7222-7229.2003 ◽

2003 ◽

Vol 23 (20) ◽

pp. 7222-7229 ◽

Cited By ~ 109

Author(s):

Evan D. Rosen ◽

Rohit N. Kulkarni ◽

Pasha Sarraf ◽

Umut Ozcan ◽

Terumasa Okada ◽

...

Keyword(s):

Glucose Homeostasis ◽

Cellular Proliferation ◽

Cell Mass ◽

Physiological Role ◽

Nuclear Hormone Receptor ◽

Chow Diet ◽

Peroxisome Proliferator ◽

Β Cells ◽

Β Cell ◽

Peroxisome Proliferator Activated Receptor

ABSTRACT The nuclear hormone receptor peroxisome proliferator-activated receptor γ (PPARγ) is an important regulator of lipid and glucose homeostasis and cellular differentiation. Studies of many cell types in vitro and in vivo have demonstrated that activation of PPARγ can reduce cellular proliferation. We show here that activation of PPARγ is sufficient to reduce the proliferation of cultured insulinoma cell lines. We created a model with mice in which the expression of the PPARG gene in β cells was eliminated (βγKO mice), and these mice were found to have significant islet hyperplasia on a chow diet. Interestingly, the normal expansion of β-cell mass that occurs in control mice in response to high-fat feeding is markedly blunted in these animals. Despite this alteration in β-cell mass, no effect on glucose homeostasis in βγKO mice was noted. Additionally, while thiazolidinediones enhanced insulin secretion from cultured wild-type islets, administration of rosiglitazone to insulin-resistant control and βγKO mice revealed that PPARγ in β cells is not required for the antidiabetic actions of these compounds. These data demonstrate a critical physiological role for PPARγ function in β-cell proliferation and also indicate that the mechanisms controlling β-cell hyperplasia in obesity are different from those that regulate baseline cell mass in the islet.

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STAT3 Regulates Mitochondrial Gene Expression in Pancreatic β-Cells and its Deficiency Induces Glucose Intolerance in Obesity

10.2337/figshare.14831049 ◽

2021 ◽

Author(s):

Anaïs Schaschkow ◽

Lokman Pang ◽

Valerie Vandenbempt ◽

Bernat Elvira ◽

Sara A. Litwak ◽

...

Keyword(s):

Gene Expression ◽

Glucose Intolerance ◽

High Fat Diet ◽

Cell Function ◽

Mitochondrial Gene ◽

High Fat ◽

Β Cells ◽

Β Cell ◽

Β Cell Function ◽

Deficient Mice

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A polysaccharide extract from the medicinal plant Maidong inhibits the IKK–NF-κB pathway and IL-1β–induced islet inflammation and increases insulin secretion

Journal of Biological Chemistry ◽

10.1074/jbc.ra120.014357 ◽

2020 ◽

Vol 295 (36) ◽

pp. 12573-12587

Author(s):

Dandan Mao ◽

Xiao Yu Tian ◽

Di Mao ◽

Sze Wan Hung ◽

Chi Chiu Wang ◽

...

Keyword(s):

Insulin Secretion ◽

Cell Function ◽

Nuclear Translocation ◽

Oral Glucose ◽

Chow Diet ◽

Obese Mice ◽

Β Cells ◽

Β Cell ◽

Iκb Kinase ◽

Β Cell Function

The herb dwarf lilyturf tuber (Maidong, Ophiopogonis Radix) is widely used in Chinese traditional medicine to manage diabetes and its complications. However, the role of Maidong polysaccharide extract (MPE) in pancreatic β-cell function is unclear. Here, we investigated whether MPE protects β-cell function and studied the underlying mechanisms. We treated db/db and high-fat diet (HFD)-induced obese mice with 800 or 400 mg/kg MPE or water for 4 weeks, followed by an oral glucose tolerance test. Pancreas and blood were collected for molecular analyses, and clonal MIN6 β-cells and primary islets from HFD-induced obese mice and normal chow diet–fed mice were used in additional analyses. In vivo, MPE both increased insulin secretion and reduced blood glucose in the db/db mice but increased only insulin secretion in the HFD-induced obese mice. MPE substantially increased the β-cell area in both models (3-fold and 2-fold, p < 0.01, for db/db and HFD mice, respectively). We observed reduced nuclear translocation of the p65 subunit of NF-κB in islets of MPE-treated db/db mice, coinciding with enhanced glucose-stimulated insulin secretion (GSIS). In vitro, MPE potentiated GSIS and decreased interleukin 1β (IL-1β) secretion in MIN6 β-cells. Incubation of MIN6 cells with tumor necrosis factor α (TNFα), interferon-γ, and IL-1β amplified IL-1β secretion and inhibited GSIS. These effects were partially reversed with MPE or the IκB kinase β inhibitor PS1145, coinciding with reduced activation of p65 and p-IκB in the NF-κB pathway. We conclude that MPE may have potential for therapeutic development for β-cell protection.

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