Reduced basal insulin secretion from islets isolated from tafazzin deficient mice is associated with reduced mitochondrial function
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ABSTRACT:
PROVIDER: PRJNA561720 | ENA |
REPOSITORIES: ENA
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Project description:Tafazzin is a transacylase which causes the content and molecular structure of cardiolipin (CL) to be altered in the inner mitochondrial membrane. The enzymatic machinery responsible for oxidative respiration are localized to the inner mitochondrial membrane and require CL for activity. As a result, tafazzin is critical for maintaining mitochondrial function. In beta-cells, which are the insulin secreting cells in pancreatic islets, mitochondrial function is linked to insulin secretion. We previously established that tafazzin knock-down mice were lean and maintained insulin sensitivity compared to the obese insulin resistant control litter mates. However, it was unknown whether tafazzin deficiency also influenced insulin secretion in the establishment of the lean phenotype. Using X week-old mice, we ascertained that the number of beta-cells was similar between genotypes. Ex vivo insulin secretion under low glucose conditions was reduced (52%) from islets isolated from tafazzin knock-down mice. Consistent with this tafazzin knock-down mice exhibited reduced fasting insulin plasma insulin levels. Measurement of mitochondrial oxygen consumption revealed that basal oxygen consumption was reduced (58%) in islets from tafazzin-deficient animals. The addition of etomoxir, an inhibitor of mitochondrial fatty acid translocation, significantly elevated basal mitochondrial respiration (5-fold) in islets from tafazzin knockdown mice, indicating a significant fatty acid-mediated inhibitory effect. In contrast, etomoxir lacked any measurable effect on control wild-type islets. The altered mitochondrial function identified in taffazin knock-down islets was not associated with reduced CL content or elevated oxyCL species. Our experiments indicate that tafazzin plays a key role in regulating normal islet beta-cell function.
2021-07-31 | GSE136242 | GEO
Project description:Wolfram syndrome, an autosomal recessive disorder characterized by juvenile-onset diabetes mellitus and optic atrophy, is caused by mutations in the WFS1 gene. WFS1 encodes an endoplasmic reticulum resident transmembrane protein. The Wfs1-null mice exhibit progressive insulin deficiency and diabetes. The aim of the present study was to describe the insulin secretion and transcriptome of pancreatic islets in WFS1-deficient mice. WFS1-deficient (Wfs1KO) mice had considerably less pancreatic islets than heterozygous (Wfs1HZ) or wild-type (WT) mice. Wfs1KO pancreatic islets secreted less insulin after stimulation with 2 and 10 mM glucose and with tolbutamide solution compared to WT and Wfs1HZ islets, but not after stimulation with 20 mM glucose. Differences in proinsulin amount were not statistically significant although there was a trend that Wfs1KO had an increased level of proinsulin. After stimulation with 2 mM glucose solution the proinsulin/insulin ratio in Wfs1KO was significantly higher than that of WT and Wfs1HZ. RNA-seq from pancreatic islets found melastatin-related transient receptor potential subfamily member 5 protein gene (Trpm5) to be downregulated in WFS1-deficient mice. Functional annotation of RNA sequencing results showed that WFS1 deficiency influenced significantly the pathways related to tissue morphology, endocrine system development and function, molecular transport network. These findings suggest an interactive role of WFS1 and TRPM5 in insulin secretion. 12 samples: three genotypes, 4 individuals in each genotype
2015-02-14 | E-GEOD-65929 | biostudies-arrayexpress
Project description:Wolfram syndrome, an autosomal recessive disorder characterized by juvenile-onset diabetes mellitus and optic atrophy, is caused by mutations in the WFS1 gene. WFS1 encodes an endoplasmic reticulum resident transmembrane protein. The Wfs1-null mice exhibit progressive insulin deficiency and diabetes. The aim of the present study was to describe the insulin secretion and transcriptome of pancreatic islets in WFS1-deficient mice. WFS1-deficient (Wfs1KO) mice had considerably less pancreatic islets than heterozygous (Wfs1HZ) or wild-type (WT) mice. Wfs1KO pancreatic islets secreted less insulin after stimulation with 2 and 10 mM glucose and with tolbutamide solution compared to WT and Wfs1HZ islets, but not after stimulation with 20 mM glucose. Differences in proinsulin amount were not statistically significant although there was a trend that Wfs1KO had an increased level of proinsulin. After stimulation with 2 mM glucose solution the proinsulin/insulin ratio in Wfs1KO was significantly higher than that of WT and Wfs1HZ. RNA-seq from pancreatic islets found melastatin-related transient receptor potential subfamily member 5 protein gene (Trpm5) to be downregulated in WFS1-deficient mice. Functional annotation of RNA sequencing results showed that WFS1 deficiency influenced significantly the pathways related to tissue morphology, endocrine system development and function, molecular transport network. These findings suggest an interactive role of WFS1 and TRPM5 in insulin secretion.
2015-02-14 | GSE65929 | GEO
Project description:Differential effects of voclosporin and tacrolimus on insulin secretion from human islets
| PRJNA659488 | ENA
Project description:After the discovery of insulin a century ago, extensive work has been done to unravel the molecular network regulating insulin secretion. Here, we performed a chemical screen and identified AZD7762, a compound that potentiates glucose-stimulated insulin secretion (GSIS) of human β cell line, healthy and type 2 diabetic (T2D) human islets, and primary cynomolgus macaque islets. In vivo studies in diabetic mouse models and cynomolgus macaques demonstrated that AZD7762 enhances GSIS and improves glucose tolerance. Furthermore, genetic manipulation confirmed that ablation of CHEK2 in human β cells results in increased insulin secretion. Consistently, high-fat-diet fed Chk2-/- mice show elevated insulin secretion and improved glucose clearance. Finally, an untargeted metabolic profiling demonstrated the key role of the CHEK2-PP2A-PLK1-G6PD-PPP pathway in insulin secretion. This study successfully identifies a previously unknown insulin secretion regulating pathway that is conserved across rodents, cynomolgus macaques and human β cells in both healthy and T2D conditions.
2023-10-25 | GSE239335 | GEO
Project description:Objective: Histone deacetylases are epigenetic regulators known to control gene transcription in various tissues. A member of this family, histone deacetylase 3 (HDAC3), has been shown to regulate metabolic genes. Cell culture studies with HDAC-specific inhibitors and siRNA suggest that HDAC3 plays a role in pancreatic β-cell function, but a recent genetic study in mice has been contradictory. Here we address the functional role of HDAC3 in β-cells of adult mice. Methods: An HDAC3 β-cell specific knockout was generated in adult MIP-CreERT transgenic mice using the Cre-loxP system. Induction of HDAC3 deletion was initiated at 8 weeks of age with administration of tamoxifen in corn oil (2 mg/day for 5 days). Mice were assayed for glucose tolerance, glucose-stimulated insulin secretion, and islet function 2 weeks after induction of the knockout. Transcriptional functions of HDAC3 were assessed by ChIP-seq as well as RNA-seq comparing control and -cell knockout islets. Results: HDAC3 β-cell specific knockout (HDAC3βKO) did not increase total pancreatic insulin content or β-cell mass. However, HDAC3βKO mice demonstrated markedly improved glucose tolerance. This improved glucose metabolism coincided with increased basal and glucose-stimulated insulin secretion in vivo as well as in isolated islets. Cistromic and transcriptomic analyses of pancreatic islets revealed that HDAC3 regulates multiple genes that contribute to glucose-stimulated insulin secretion. Conclusions: HDAC3 plays an important role in regulating insulin secretion in vivo and therapeutic intervention may improve glucose homeostasis.
2016-11-26 | GSE90531 | GEO
Project description:Fine-tuning of insulin release from pancreatic β-cells is essential to maintain blood glucose homeostasis. Here, we report that insulin secretion is regulated by a circular RNA containing the lariat sequence of the second intron of the insulin gene. Silencing of this intronic circular RNA in pancreatic islets leads to a decrease in the expression of key components of the secretory machinery of β-cells, resulting in impaired glucose- or KCl-induced insulin release and calcium signaling. The effect of the circular RNA is exerted at the transcriptional level and involves an interaction with the RNA-binding protein TAR DNA-binding protein 43 kDa (TDP-43). The level of this circularized intron is reduced in the islets of rodent diabetes models and of type 2 diabetic patients, possibly explaining their impaired secretory capacity. The study of this and other circular RNAs helps understanding β-cell dysfunction under diabetes conditions, and the etiology of this common metabolic disorder.
2020-09-21 | GSE134699 | GEO
Project description:Adaptation of the islet β-cell insulin secretory response to changing insulin demand is critical for blood glucose homeostasis, yet the mechanisms underlying this adaptation are unknown. Here, we show that nutrient cues adapt insulin secretion by modulating chromatin state and transcription of genes regulating β-cell nutrient sensing and metabolism. Feeding stimulates histone acetylation at sites occupied by the chromatin-modifying enzyme Lsd1 in islets. We demonstrate that β-cell-specific deletion of Lsd1 leads to insulin hypersecretion, aberrant expression of nutrient response genes, and histone hyperacetylation, features we also observed in the db/db model of chronically increased insulin demand. Moreover, genetic variants associated with fasting glucose levels and type 2 diabetes risk are enriched at LSD1-bound sites in human islets, suggesting interindividual variation in β-cell functional adaptation in humans. These findings reveal nutrient state-dependent modulation of the islet epigenome and identify Lsd1 as a regulator of feeding-stimulated chromatin modification and adaptive insulin secretion.
2023-02-24 | GSE134901 | GEO
Project description:In the setting of obesity and insulin resistance, glycemia is controlled in part by beta cell compensation and subsequent hyperinsulinemia. Weight loss improves glycemia and decreases hyperinsulinemia, whereas weight cycling worsens glycemic control. The mechanisms responsible for weight cycling-induced deterioration in glucose homeostasis are poorly understood. Thus, we aimed to pinpoint the main regulatory junctions at which weight cycling alters glucose homeostasis in mice. Using in vivo and ex vivo procedures we show that despite having worsened glucose tolerance, weight-cycled mice do not manifest impaired whole-body insulin action. Instead, weight cycling reduces insulin secretory capacity in vivo during clamped hyperglycemia and ex vivo in perifused islets. Islets from weight-cycled mice have reduced expression of drivers of b-cell identity (Mafa, Pdx1, Nkx6.1, Ucn3) and lower islet insulin content, compared to those from obese mice, suggesting inadequate transcriptional and posttranscriptional response to repeated nutrient overload. Collectively, these data support a model in which pancreatic plasticity is challenged in the face of large fluctuations in body weight resulting in a mismatch between glycemia and insulin secretion in mice.
2022-11-09 | GSE202697 | GEO
Project description:Pancreatic beta-cells are specialized for coupling glucose metabolism to insulin peptide production and secretion. Acute glucose exposure robustly and coordinately increases translation of proinsulin and proteins required for secretion of mature insulin peptide. By contrast, chronically elevated glucose levels that occur during diabetes impair beta-cell insulin secretion and have been shown experimentally to suppress insulin translation. Whether translation of other genes critical for insulin secretion are similarly downregulated by chronic high glucose is unknown. Here, we used high-throughput ribosome profiling and nascent proteomics in MIN6 insulinoma cells to elucidate the genome-wide impact of sustained high glucose on beta-cell mRNA translation. Prior to induction of ER stress or suppression of global translation, sustained high glucose suppressed glucose-stimulated insulin secretion and downregulated translation of not only insulin, but also of mRNAs related to insulin secretory granule formation, exocytosis, and metabolism-coupled insulin secretion. Translation of these mRNAs was also downregulated in primary rat and human islets following ex-vivo incubation with sustained high glucose and in an in vivo model of chronic mild hyperglycemia. Furthermore, translational downregulation decreased cellular abundance of these proteins. Our study uncovered a translational regulatory circuit during beta-cell glucose toxicity that impairs expression of proteins with critical roles in beta-cell function.
2023-12-01 | GSE248349 | GEO