Starvation to Glucose Reprograms Development of Neurovascular Unit in Embryonic Retinal Cells

Perinatal exposure to starvation is a risk factor for development of severe retinopathy in adult patients with diabetes. However, the underlying mechanisms are not completely understood. In the present study, we shed light on molecular consequences of exposure to short-time glucose starvation on the transcriptome profile of mouse embryonic retinal cells. We found a profound downregulation of genes regulating development of retinal neurons, which was accompanied by reduced expression of genes encoding for glycolytic enzymes and glutamatergic signaling. At the same time, glial and vascular markers were upregulated, mimicking the diabetes-associated increase of angiogenesis—a hallmark of pathogenic features in diabetic retinopathy. Energy deprivation as a consequence of starvation to glucose seems to be compensated by upregulation of genes involved in fatty acid elongation. Results from the present study demonstrate that short-term glucose deprivation during early fetal life differentially alters expression of metabolism- and function-related genes and could have detrimental and lasting effects on gene expression in the retinal neurons, glial cells, and vascular elements and thus potentially disrupting gene regulatory networks essential for the formation of the retinal neurovascular unit. Abnormal developmental programming during retinogenesis may serve as a trigger of reactive gliosis, accelerated neurodegeneration, and increased vascularization, which may promote development of severe retinopathy in patients with diabetes later in life.publishedVersio

MafA and MafB Regulate Genes Critical to β-Cells in a Unique Temporal Manner

OBJECTIVE-Several transcription factors are essential to pancreatic islet beta-cell development, proliferation, and activity, including MafA and MafB. However, MafA and MafB are distinct from others in regard to temporal and islet cell expression pattern, with beta-cells affected by MafB only during development and exclusively by MafA in the adult. Our aim was to define the functional relationship between these closely related activators to the beta-cell. RESEARCH DESIGN AND METHODS-The distribution of MafA and MafB in the beta-cell population was determined immunohistochemically at various developmental and perinatal stages in mice. To identify genes regulated by MafB, microarray profiling was performed on wild-type and MafB(-/-) pancreata at embryonic day 18.5, with candidates evaluated by quantitative RT-PCR and in situ hybridization. The potential role of MafA in the expression of verified targets was next analyzed in adult islets of a pancreas-wide MafA mutant (termed MafA(Delta Panc)). RESULTS-MafB was produced in a larger fraction of beta-cells than MafA during development and found to regulate potential effectors of glucose sensing, hormone processing, vesicle formation, and insulin secretion. Notably, expression from many of these genes was compromised in MafA(Delta Panc) islets, suggesting that MafA is required to sustain expression in adults. CONCLUSIONS-Our results provide insight into the sequential manner by which MafA and MafB regulate islet beta-cell formation and maturation. Diabetes 59:2530-2539, 201

The type 1 diabetes gene TYK2 regulates beta-cell development and its responses to interferon-alpha

The TYK2 gene is associated with development of type 1 diabetes. Here the authors show that TYK2 regulates beta-cell development, but at the same time TYK2 inhibition in the islets prevents IFN alpha responses and enhances their survival against CD8(+) T-cell cytotoxicity; representing a potent therapeutic target to halt T1D progression. Type 1 diabetes (T1D) is an autoimmune disease that results in the destruction of insulin producing pancreatic beta-cells. One of the genes associated with T1D is TYK2, which encodes a Janus kinase with critical roles in type-Iota interferon (IFN-Iota) mediated intracellular signalling. To study the role of TYK2 in beta-cell development and response to IFN alpha, we generated TYK2 knockout human iPSCs and directed them into the pancreatic endocrine lineage. Here we show that loss of TYK2 compromises the emergence of endocrine precursors by regulating KRAS expression, while mature stem cell-islets (SC-islets) function is not affected. In the SC-islets, the loss or inhibition of TYK2 prevents IFN alpha-induced antigen processing and presentation, including MHC Class Iota and Class Iota Iota expression, enhancing their survival against CD8(+) T-cell cytotoxicity. These results identify an unsuspected role for TYK2 in beta-cell development and support TYK2 inhibition in adult beta-cells as a potent therapeutic target to halt T1D progression.Peer reviewe

Mapping the Cord Blood Transcriptome of Pregnancies Affected by Early Maternal Anemia to Identify Signatures of Fetal Programming

Context Anemia during early pregnancy (EP) is common in developing countries and is associated with adverse health consequences for both mothers and children. Offspring of women with EP anemia often have low birth weight, which increases risk for cardiometabolic diseases, including type 2 diabetes (T2D), later in life. Objective We aimed to elucidate mechanisms underlying developmental programming of adult cardiometabolic disease, including epigenetic and transcriptional alterations potentially detectable in umbilical cord blood (UCB) at time of birth. Methods We leveraged global transcriptome- and accompanying epigenome-wide changes in 48 UCB from newborns of EP anemic Tanzanian mothers and 50 controls to identify differentially expressed genes (DEGs) in UCB exposed to maternal EP anemia. DEGs were assessed for association with neonatal anthropometry and cord insulin levels. These genes were further studied in expression data from human fetal pancreas and adult islets to understand their role in beta-cell development and/or function. Results The expression of 137 genes was altered in UCB of newborns exposed to maternal EP anemia. These putative signatures of fetal programming, which included the birth weight locus LCORL, were potentially mediated by epigenetic changes in 27 genes and associated with neonatal anthropometry. Among the DEGs were P2RX7, PIK3C2B, and NUMBL, which potentially influence beta-cell development. Insulin levels were lower in EP anemia-exposed UCB, supporting the notion of developmental programming of pancreatic beta-cell dysfunction and subsequently increased risk of T2D in offspring of mothers with EP anemia. Conclusions Our data provide proof-of-concept on distinct transcriptional and epigenetic changes detectable in UCB from newborns exposed to maternal EP anemia.Peer reviewe

Islet Gene View-a tool to facilitate islet research

Characterization of gene expression in pancreatic islets and its alteration in type 2 diabetes (T2D) are vital in understanding islet function and T2D pathogenesis. We leveraged RNA sequencing and genome-wide genotyping in islets from 188 donors to create the Islet Gene View (IGW) platform to make this information easily accessible to the scientific community. Expression data were related to islet phenotypes, diabetes status, other islet-expressed genes, islet hormone-encoding genes and for expression in insulin target tissues. The IGW web application produces output graphs for a particular gene of interest. In IGW, 284 differentially expressed genes (DEGs) were identified in T2D donor islets compared with controls. Forty percent of DEGs showed cell-type enrichment and a large proportion significantly co-expressed with islet hormone-encoding genes; glucagon (GCG, 56%), amylin (IAPP, 52%), insulin (INS, 44%), and somatostatin (SST, 24%). Inhibition of two DEGs, UNC5D and SERPINE2, impaired glucose-stimulated insulin secretion and impacted cell survival in a human beta-cell model. The exploratory use of IGW could help designing more comprehensive functional follow-up studies and serve to identify therapeutic targets in T2D.Peer reviewe

Life-long impairment of glucose homeostasis upon prenatal exposure to psychostimulants

Maternal drug abuse during pregnancy is a rapidly escalating societal problem. Psychostimulants, including amphetamine, cocaine, and methamphetamine, are amongst the illicit drugs most commonly consumed by pregnant women. Neuropharmacology concepts posit that psychostimulants affect monoamine signaling in the nervous system by their affinities to neurotransmitter reuptake and vesicular transporters to heighten neurotransmitter availability extracellularly. Exacerbated dopamine signaling is particularly considered as a key determinant of psychostimulant action. Much less is known about possible adverse effects of these drugs on peripheral organs, and if in utero exposure induces lifelong pathologies. Here, we addressed this question by combining human RNA-seq data with cellular and mouse models of neuroendocrine development. We show that episodic maternal exposure to psychostimulants during pregnancy coincident with the intrauterine specification of pancreatic beta cells permanently impairs their ability of insulin production, leading to glucose intolerance in adult female but not male offspring. We link psychostimulant action specifically to serotonin signaling and implicate the sex-specific epigenetic reprogramming of serotonin-related gene regulatory networks upstream from the transcription factor Pet1/Fev as determinants of reduced insulin production.Peer reviewe

Islet-specific monoamine oxidase A and B expression depends on MafA transcriptional activity and is compromised in type 2 diabetes.

Lack or dysfunction of insulin producing β cells results in the development of type 1 and type 2 diabetes mellitus, respectively. Insulin secretion is controlled by metabolic stimuli (glucose, fatty acids), but also by monoamine neurotransmitters, like dopamine, serotonin, and norepinephrine. Intracellular monoamine levels are controlled by monoamine oxidases (Mao) A and B. Here we show that MaoA and MaoB are expressed in mouse islet β cells and that inhibition of Mao activity reduces insulin secretion in response to metabolic stimuli. Moreover, analysis of MaoA and MaoB protein expression in mouse and human type 2 diabetic islets shows a significant reduction of MaoB in type 2 diabetic β cells suggesting that loss of Mao contributes to β cell dysfunction. MaoB expression was also reduced in β cells of MafA-deficient mice, a mouse model for β cell dysfunction, and biochemical studies showed that MafA directly binds to and activates MaoA and MaoB transcriptional control sequences. Taken together, our results show that MaoA and MaoB expression in pancreatic islets is required for physiological insulin secretion and lost in type 2 diabetic mouse and human β cells. These findings demonstrate that regulation of monoamine levels by Mao activity in β cells is pivotal for physiological insulin secretion and that loss of MaoB expression may contribute to the β cell dysfunction in type 2 diabetes

MaFA is a dedicated activator of the insulin gene in vivo.

As successful generation of insulin producing cells could be used for diabetes treatment, a concerted effort is being made to understand the molecular programs underlying islet beta cell formation and function. The closely related MafA and MafB transcription factors are both key mammalian beta cell regulators. MafA and MafB are co-expressed in insulin+ beta cells during embryogenesis, while in the adult pancreas MafA is only produced in beta cells and MafB in glucagon+ alpha cells. MafB-/- animals are also deficient in insulin+ and glucagon+ cell production during embryogenesis. However, only MafA over-expression selectively induced endogenous Insulin mRNA production in cell line based assays, while MafB specifically promoted Glucagon expression. Here we analyzed if these factors were sufficient to induce insulin+ and/or glucagon+ cell formation within embryonic endoderm using the chick in ovo electroporation assay. Ectopic expression of MafA, but not MafB, promoted Insulin production, however neither MafA nor MafB were capable of inducing Glucagon. Co-electroporation of MafA with the Ngn3 transcription factor resulted in the development of more organized cell clusters containing both insulin and glucagon producing cells. Analysis of chimeric proteins of MafA and MafB demonstrated that chick Insulin activation depended on sequences within the MafA C-terminal DNA binding domain. MafA was also bound to Insulin and Glucagon transcriptional control sequences in mouse embryonic pancreas and beta cell lines. Collectively, these results demonstrate a unique ability for MafA to independently activate Insulin transcription