Project description:Pancreatic islets adapt to the increase in insulin demand during pregnancy by up-regulating beta cell proliferation, insulin synthesis, and lowering the threshold of glucose-stimulated insulin secretion. In vitro studies suggest that pregnancy hormones, such as placental lactogens and prolactin, both act through the prolactin receptor, are required for these adaptation. Furhtermore, we found that transgenic mice with heterogenous prolactin receptor null mutation are glucose intolerant, with a lower beta-cell mass and lower insulin levels. The goal here is to discover novel targets of prolactin receptor signaling in pancreatic beta cells during pregnancy.
Project description:ABSTRACT:Pregnancy requires a higher functional beta cell mass and this is associated with profound changes in the gene expression profile of pancreatic islets. Taking Tph1 as a sensitive marker for pregnancy-related islet mRNA expression in female mice, we previously identified prolactin receptors and placental lactogen as key signalling molecules. Since beta cells from male mice also express prolactin receptors, the question arose whether male and female islets have the same phenotypic resilience at the mRNA level during pregnancy. We addressed this question in vitro, by using islet tissue culture with placental lactogen and in vivo, by transplanting male or female islets into female acceptor mice. Additionally, the islet mRNA expression of pregnant prolactin receptor deficient mice was compared with that of their pregnant wild-type littermates. When cultured with placental lactogen, or transplanted in female recipients that became pregnant (day 12.5), male islets induced the ‘islet pregnancy gene signature’, which we defined as the 12 highest induced genes in non-transplanted female islets at day 12.5 of pregnancy. In addition, serotonin immunoreactivity was also induced in these male transplanted islets at day 12.5 of pregnancy. In order to investigate the importance of prolactin receptors in these mRNA changes we used a prolactin receptor deficient mouse model. For the 12 genes of the signature, which are highly induced in control pregnant mice, no significant induction of mRNA transcripts was found at day 9.5 of pregnancy. Together, our results support the key role of placental lactogen as a circulating factor that can trigger the pregnancy mRNA profile in male and female beta cells. Islets were isolated from non-prengant (NP) and pregnant (day 9.5) PRLR+/+ and PRLR-/- mice for RNA extraction and hybridization on Affymetrix microarrays. For every condition 3 biological replicates were used.
Project description:ABSTRACT:Pregnancy requires a higher functional beta cell mass and this is associated with profound changes in the gene expression profile of pancreatic islets. Taking Tph1 as a sensitive marker for pregnancy-related islet mRNA expression in female mice, we previously identified prolactin receptors and placental lactogen as key signalling molecules. Since beta cells from male mice also express prolactin receptors, the question arose whether male and female islets have the same phenotypic resilience at the mRNA level during pregnancy. We addressed this question in vitro, by using islet tissue culture with placental lactogen and in vivo, by transplanting male or female islets into female acceptor mice. Additionally, the islet mRNA expression of pregnant prolactin receptor deficient mice was compared with that of their pregnant wild-type littermates. When cultured with placental lactogen, or transplanted in female recipients that became pregnant (day 12.5), male islets induced the ‘islet pregnancy gene signature’, which we defined as the 12 highest induced genes in non-transplanted female islets at day 12.5 of pregnancy. In addition, serotonin immunoreactivity was also induced in these male transplanted islets at day 12.5 of pregnancy. In order to investigate the importance of prolactin receptors in these mRNA changes we used a prolactin receptor deficient mouse model. For the 12 genes of the signature, which are highly induced in control pregnant mice, no significant induction of mRNA transcripts was found at day 9.5 of pregnancy. Together, our results support the key role of placental lactogen as a circulating factor that can trigger the pregnancy mRNA profile in male and female beta cells. The data obtained from the normal islets of pregnant mice (day12.5) was already described in Schraenen et al. 2010 (PMID: 20886204 and PMID: 20938637). Islets and islet grafts were isolated from non-prengant and pregnant mice for RNA extraction and hybridization on Affymetrix microarrays. For every condition, at least 3 biological replicates were used.
Project description:ABSTRACT:Pregnancy requires a higher functional beta cell mass and this is associated with profound changes in the gene expression profile of pancreatic islets. Taking Tph1 as a sensitive marker for pregnancy-related islet mRNA expression in female mice, we previously identified prolactin receptors and placental lactogen as key signalling molecules. Since beta cells from male mice also express prolactin receptors, the question arose whether male and female islets have the same phenotypic resilience at the mRNA level during pregnancy. We addressed this question in vitro, by using islet tissue culture with placental lactogen and in vivo, by transplanting male or female islets into female acceptor mice. Additionally, the islet mRNA expression of pregnant prolactin receptor deficient mice was compared with that of their pregnant wild-type littermates. When cultured with placental lactogen, or transplanted in female recipients that became pregnant (day 12.5), male islets induced the ‘islet pregnancy gene signature’, which we defined as the 12 highest induced genes in non-transplanted female islets at day 12.5 of pregnancy. In addition, serotonin immunoreactivity was also induced in these male transplanted islets at day 12.5 of pregnancy. In order to investigate the importance of prolactin receptors in these mRNA changes we used a prolactin receptor deficient mouse model. For the 12 genes of the signature, which are highly induced in control pregnant mice, no significant induction of mRNA transcripts was found at day 9.5 of pregnancy. Together, our results support the key role of placental lactogen as a circulating factor that can trigger the pregnancy mRNA profile in male and female beta cells.
Project description:ABSTRACT:Pregnancy requires a higher functional beta cell mass and this is associated with profound changes in the gene expression profile of pancreatic islets. Taking Tph1 as a sensitive marker for pregnancy-related islet mRNA expression in female mice, we previously identified prolactin receptors and placental lactogen as key signalling molecules. Since beta cells from male mice also express prolactin receptors, the question arose whether male and female islets have the same phenotypic resilience at the mRNA level during pregnancy. We addressed this question in vitro, by using islet tissue culture with placental lactogen and in vivo, by transplanting male or female islets into female acceptor mice. Additionally, the islet mRNA expression of pregnant prolactin receptor deficient mice was compared with that of their pregnant wild-type littermates. When cultured with placental lactogen, or transplanted in female recipients that became pregnant (day 12.5), male islets induced the ‘islet pregnancy gene signature’, which we defined as the 12 highest induced genes in non-transplanted female islets at day 12.5 of pregnancy. In addition, serotonin immunoreactivity was also induced in these male transplanted islets at day 12.5 of pregnancy. In order to investigate the importance of prolactin receptors in these mRNA changes we used a prolactin receptor deficient mouse model. For the 12 genes of the signature, which are highly induced in control pregnant mice, no significant induction of mRNA transcripts was found at day 9.5 of pregnancy. Together, our results support the key role of placental lactogen as a circulating factor that can trigger the pregnancy mRNA profile in male and female beta cells. The data obtained from the normal islets of pregnant mice (day12.5) was already described in Schraenen et al. 2010 (PMID: 20886204 and PMID: 20938637).
Project description:During pregnancy, the energy requirements of the fetus impose changes in maternal metabolism. Increasing insulin resistance in the mother maintains nutrient flow to the growing fetus, while prolactin and placental lactogen counterbalance this resistance and prevent maternal hyperglycemia by driving expansion of the maternal population of insulin-producing beta-cells. However, the exact mechanisms by which the lactogenic hormones drive beta-cell expansion remain uncertain. Here we show that serotonin acts downstream of lactogen signaling to drive beta-cell proliferation. Serotonin synthetic enzyme Tph1 and serotonin production increased sharply in beta-cells during pregnancy or after treatment with lactogens in vitro. Inhibition of serotonin synthesis by dietary tryptophan restriction or Tph inhibition blocked beta-cell expansion and induced glucose intolerance in pregnant mice without affecting insulin sensitivity. Expression of the Gq-linked serotonin receptor Htr2b in maternal islets increased during pregnancy and normalized just prior to parturition, while expression of the Gi-linked receptor Htr1d increased at the end of pregnancy and postpartum. Blocking Htr2b signaling in pregnant mice also blocked beta-cell expansion and caused glucose intolerance. These studies reveal an integrated signaling pathway linking beta-cell mass to anticipated insulin need during pregnancy. Modulators of this pathway, including medications and diet, may affect the risk of gestational diabetes. Analysis of poly(A)+ RNA from 3 biological replicates of pancreatic islets isolated from normal female and pregnant female mice
Project description:ABSTRACT: The human growth hormone (hGH) minigene is frequently used in transgenic mouse lines to ensure proper transgene expression. Here, we show that hGH is expressed in islets isolated from the commonly used Pdx1-CreLate mouse model. Locally secreted hGH activates prolactin receptors on M-NM-2 cells causing phosphorylation of STAT5, and induces a pregnancy-like change in gene expression, augmented pancreatic M-NM-2 cell mass and insulin content. In addition, islets of Pdx1-CreLate mice had lower GLUT2 expression, reduced glucose-induced insulin release and were protected against the M-NM-2 cell toxin streptozotocin. As the hGH minigene is commonly used in a great number of Cre-driver and other transgenic mouse models in diabetes research, the currently reported profound phenotypic changes may necessitate the re-evaluation of a large amount of previously published work. Data obtained for the Pdx1-creLate and control samples were compaired to investigate the effect of hGH on the mRNA profile of islets. The data obtained from the islets of pregnant mice was added to the analysis to confirm the pregnacy-like phenotype in the Pdx1-creLate islets. The data of the different days of pregnancy was already described in Schraenen et al. 2010 (PMID: 20886204 and PMID: 20938637). Islets were isolated from Pdx1-creLate, control and pregnant mice for RNA extraction and hybridization on Affymetrix microarrays. For every condition, at least 3 biological replicates were used.
Project description:ABSTRACT: The human growth hormone (hGH) minigene is frequently used in the derivation of transgenic mouse lines to enhance transgene expression. Although this minigene is present in the transgenes as a secondcistron, and thus not thought to be expressed, we found that three commonly used lines, Pdx1-CreLate, RIP-Cre, and MIP-GFP, each expressed significant amounts of hGH in pancreatic islets. Locally secreted hGH binds to prolactin receptors on β cells, activates STAT5 signaling, and induces pregnancy-like changes in gene expression, thereby augmenting pancreatic β cell mass and insulin content. In addition, islets of Pdx1-CreLate mice have lower GLUT2 expression and reduced glucose-induced insulin release and are protected against the β cell toxin streptozotocin. These findings may be important when interpreting results obtained when these and other hGH minigene-containing transgenic mice are used. Data obtained for the Pdx1-creLate and control samples were compaired to investigate the effect of hGH on the mRNA profile of islets. The data obtained from the islets of pregnant mice was added to the analysis to confirm the pregnacy-like phenotype in the Pdx1-creLate islets. The data of the different days of pregnancy was already described in Schraenen et al. 2010 (PMID: 20886204 and PMID: 20938637).
Project description:Pancreatic islets adapt to insulin resistance of pregnancy by up regulating beta-cell proliferation and increase insulin secretion. Previously, we found that prolactin receptor (Prlr) signaling is important for this process, as heterozygous prolactin receptor-null (Prlr+/-) mice are glucose intolerant, had a lower number of beta cells and lower serum insulin levels than wild type mice during pregnancy. However, since Prlr expression is ubiquitous, to determine its beta-cell-specific effects, we generated a transgenic mouse with a floxed Prlr allele under the control of an inducible promoter, i.e. bPrlR-/- mice, allowing conditional deletion of Prlr from beta cells in adult mice. In this study, we found that beta-cell-specific Prlr reduction resulted in elevated blood glucose during pregnancy. Similar to our previous finding in mice with global Prlr reduction, beta-cell-specific Prlr loss led to a lower beta-cell mass and a lower in vivo insulin level during pregnancy. However, these islets do not have an intrinsic insulin secretion defect when tested in vitro. Interestingly, when we compared the islet gene expression profile, using islets isolated from mice with global versus beta-cell-specific Prlr reduction, we found differences in expression of genes that regulate apoptosis, synaptic vesicle function and neuronal development. Indeed, islets from pregnant Prlr+/- mice are more susceptible glucolipotoxicity than bPrlR+/- islets. These observations suggest that Prlr has both cell-autonomous and non-cell-autonomous effect on beta cells, beyond its regulation of pro-proliferative genes.
Project description:During pregnancy, the energy requirements of the fetus impose changes in maternal metabolism. Increasing insulin resistance in the mother maintains nutrient flow to the growing fetus, while prolactin and placental lactogen counterbalance this resistance and prevent maternal hyperglycemia by driving expansion of the maternal population of insulin-producing beta-cells. However, the exact mechanisms by which the lactogenic hormones drive beta-cell expansion remain uncertain. Here we show that serotonin acts downstream of lactogen signaling to drive beta-cell proliferation. Serotonin synthetic enzyme Tph1 and serotonin production increased sharply in beta-cells during pregnancy or after treatment with lactogens in vitro. Inhibition of serotonin synthesis by dietary tryptophan restriction or Tph inhibition blocked beta-cell expansion and induced glucose intolerance in pregnant mice without affecting insulin sensitivity. Expression of the Gq-linked serotonin receptor Htr2b in maternal islets increased during pregnancy and normalized just prior to parturition, while expression of the Gi-linked receptor Htr1d increased at the end of pregnancy and postpartum. Blocking Htr2b signaling in pregnant mice also blocked beta-cell expansion and caused glucose intolerance. These studies reveal an integrated signaling pathway linking beta-cell mass to anticipated insulin need during pregnancy. Modulators of this pathway, including medications and diet, may affect the risk of gestational diabetes.