Developmental programming of neonatal pancreatic ß-cells by a maternal low-protein diet in rats involves a switch from proliferation to differentiation.

Maternal low-protein diets (LP) impair pancreatic ß-cell development, resulting in later-life failure and susceptibility to type 2 diabetes (T2D). We hypothesized that intrauterine and/or postnatal developmental programming seen in this situation involve altered ß-cell structure and relative time course of expression of genes critical to ß-cell differentiation and growth. Pregnant Wistar rats were fed either control (C) 20% or restricted (R) 6% protein diets during pregnancy (1st letter) and/or lactation (2nd letter) in four groups: CC, RR, RC, and CR. At postnatal days 7 and 21, we measured male offspring ß-cell fraction, mass, proliferation, aggregate number, and size as well as mRNA level for 13 key genes regulating ß-cell development and function in isolated islets. Compared with CC, pre- and postnatal LP (RR) decreased ß-cell fraction, mass, proliferation, aggregate size, and number and increased Hnf1a, Hnf4a, Pdx1, Isl1, Rfx6, and Slc2a2 mRNA levels. LP only in pregnancy (RC) also decreased ß-cell fraction, mass, proliferation, aggregate size, and number and increased Hnf1a, Hnf4a, Pdx1, Rfx6, and Ins mRNA levels. Postnatal LP offspring (CR) showed decreased ß-cell mass but increased ß-cell fraction, aggregate number, and Hnf1a, Hnf4a, Rfx6, and Slc2a2 mRNA levels. We conclude that LP in pregnancy sets the trajectory of postnatal ß-cell growth and differentiation, whereas LP in lactation has smaller effects. We propose that LP promotes differentiation through upregulation of transcription factors that stimulate differentiation at the expense of proliferation. This results in a decreased ß-cell reserve, which can contribute to later-life predisposition to T2D.

Exposure to Glucocorticoids in the First Part of Fetal Life is Associated with Insulin Secretory Defect in Adult Humans.

OBJECTIVE: High glucocorticoid levels in rodents inhibit development of beta cells during fetal life and lead to insulin deficiency in adulthood. To test whether similar phenomena occur in humans, we compared beta-cell function in adults who were exposed to glucocorticoids during the first part of fetal life with that of nonexposed subjects. RESEARCH DESIGN AND METHODS: The study was conducted in 16 adult participants exposed to glucocorticoids during the first part of fetal life and in 16 nonexposed healthy participants with normal glucose tolerance who were matched for age, sex, and body mass index (BMI). Exposed participants had been born to mothers who were treated with dexamethasone 1 to 1.5 mg/day from the sixth gestational week (GW) to prevent genital virilization in children at risk of 21-hydroxylase deficiency. We selected offspring of mothers who stopped dexamethasone before the 18th GW following negative genotyping of the fetus. Insulin and glucagon secretion were measured during an oral glucose tolerance test (OGTT) and graded intravenous (IV) glucose and arginine tests. Insulin sensitivity was measured by hyperinsulinemic-euglycemic-clamp. RESULTS: Age, BMI, and anthropometric characteristics were similar in the 2 groups. Insulinogenic index during OGTT and insulin sensitivity during the clamp were similar in the 2 groups. In exposed subjects, insulin secretion during graded IV glucose infusion and after arginine administration decreased by 17% (P = 0.02) and 22% (P = 0.002), respectively, while glucagon secretion after arginine increased. CONCLUSION: Overexposure to glucocorticoids during the first part of fetal life is associated with lower insulin secretion at adult age, which may lead to abnormal glucose tolerance later in life.

Potential role of glucocorticoid signaling in the formation of pancreatic islets in the human fetus.

Glucocorticoids have been suggested to play a role in programming late adult disorders like diabetes during fetal life. Recent work in rodents showed their role in pancreas development by modulating the expression of transcription factors. The aim of this work was to investigate their possible implication in human pancreas development. The ontogenesis of glucocorticoid receptor (GR) and several pancreatic transcription factors was studied by immunohistochemistry and RT-PCR on human fetal pancreatic specimens. At 6 wk of development (wd) insulin promoting factor 1 (IPF1) was expressed in the majority of epithelial cells forming tubular structures while GR was present in the mesenchyme, suggesting an early role of glucocorticoids, before endocrine and exocrine differentiation. Only GR alpha (active form) mRNA was expressed from 6 wk onwards while GR beta (inactive form) was never observed. The first insulin cells did not express IPF1 or GR. Islet formation occurred from 10 wd as IPF1-positive cells started to express simultaneously insulin and GR. This coexpression in beta cells persisted until adulthood. The mRNA expression profiles confirmed immunohistochemistry and showed the early expression of crucial transcription factors. In conclusion, the presence of the active GR isoform around islet formation supports the novel idea that glucocorticoids could modulate human pancreas development.

[Developmental origin of health and adult diseases (DOHaD): evolution of a concept over three decades]. / Le concept des origines développementales de la santé--Évolution sur trois décennies.

In the 1980s, D. Barker and his team proposed the hypothesis of a fetal origin of adult diseases. The concept subsequently evolved into the developmental origins of health and diseases. Progresses in various domains such as social epidemiology, neuroscience, toxicology have contributed to establish the early years of life as a key period for future health. Finally, epigenetics has provided biological plausibility to long-term programming of health by early exposures. The convergence of all these currents has led to conceptualize human health in a complex and dynamic continuum, the Lifecourse Health Development, beginning in the prenatal period and covering the whole life. Many animal models have been developed to try to unravel the mechanisms involved. Their contributions are described in this paper with the example of type 2 diabetes.

Glucocorticoids Inhibit Basal and Hormone-Induced Serotonin Synthesis in Pancreatic Beta Cells.

Diabetes is a major complication of chronic Glucocorticoids (GCs) treatment. GCs induce insulin resistance and also inhibit insulin secretion from pancreatic beta cells. Yet, a full understanding of this negative regulation remains to be deciphered. In the present study, we investigated whether GCs could inhibit serotonin synthesis in beta cell since this neurotransmitter has been shown to be involved in the regulation of insulin secretion. To this aim, serotonin synthesis was evaluated in vitro after treatment with GCs of either islets from CD1 mice or MIN6 cells, a beta-cell line. We also explored the effect of GCs on the stimulation of serotonin synthesis by several hormones such as prolactin and GLP 1. We finally studied this regulation in islet in two in vivo models: mice treated with GCs and with liraglutide, a GLP1 analog, and mice deleted for the glucocorticoid receptor in the pancreas. We showed in isolated islets and MIN6 cells that GCs decreased expression and activity of the two key enzymes of serotonin synthesis, Tryptophan Hydroxylase 1 (Tph1) and 2 (Tph2), leading to reduced serotonin contents. GCs also blocked the induction of serotonin synthesis by prolactin or by a previously unknown serotonin activator, the GLP-1 analog exendin-4. In vivo, activation of the Glucagon-like-Peptide-1 receptor with liraglutide during 4 weeks increased islet serotonin contents and GCs treatment prevented this increase. Finally, islets from mice deleted for the GR in the pancreas displayed an increased expression of Tph1 and Tph2 and a strong increased serotonin content per islet. In conclusion, our results demonstrate an original inhibition of serotonin synthesis by GCs, both in basal condition and after stimulation by prolactin or activators of the GLP-1 receptor. This regulation may contribute to the deleterious effects of GCs on beta cells.

Correction: Glucocorticoids Inhibit Basal and Hormone-Induced Serotonin Synthesis in Pancreatic Beta Cells.

[This corrects the article DOI: 10.1371/journal.pone.0149343.].

Dissecting the role of glucocorticoids on pancreas development.

To determine whether glucocorticoids are involved in pancreas development, glucocorticoid treatment of rat pancreatic buds in vitro was combined with the analysis of transgenic mice lacking the glucocorticoid receptor (GR) in specific pancreatic cells. In vitro treatment of embryonic pancreata with dexamethasone, a glucocorticoid agonist, induced a decrease of insulin-expressing cell numbers and a doubling of acinar cell area, indicating that glucocorticoids favored acinar differentiation; in line with this, expression of Pdx-1, Pax-6, and Nkx6.1 was downregulated, whereas the mRNA levels of Ptf1-p48 and Hes-1 were increased. The selective inactivation of the GR gene in insulin-expressing beta-cells in mice (using a RIP-Cre transgene) had no measurable consequences on beta- or alpha-cell mass, whereas the absence of GR in the expression domain of Pdx-1 (Pdx-Cre transgene) led to a twofold increased beta-cell mass, with increased islet numbers and size but normal alpha-cell mass in adults. These results demonstrate that glucocorticoids play an important role in pancreatic beta-cell lineage, acting before hormone gene expression onset and possibly also modulating the balance between endocrine and exocrine cell differentiation.

Endocrine pancreas development in growth-retarded human fetuses.

Glucose intolerance in adults born with intrauterine growth retardation (IUGR) may involve peripheral insulin resistance and/or abnormal endocrine pancreas development during fetal life. We quantified insulin-containing cells in deceased human fetuses with IUGR (<10th percentile, n = 21) or normal growth (control fetuses, n = 15). Paraffin-embedded pancreatic tissues from fetuses older than 32 weeks were obtained from two fetopathology departments. Mean gestational age was 36 weeks in both groups. Tissues with lysis and those fetuses with defects, aneuploidy, or genetic abnormalities were excluded. For each subject, six pancreatic sections spaced evenly throughout the organ were immunostained with anti-insulin antibody. Total tissue and insulin-positive areas were measured by computer-assisted quantitative morphometry. Results were expressed in percentages. To evaluate islet morphogenesis, the percentages of beta-cells inside and outside islets were determined. Islet density was similar in the two groups (P = 0.86). The percentage of pancreatic area occupied by beta-cells (beta-cell fraction) was not correlated with gestational age (r = 0.06 and P = 0.97 in IUGR fetuses; r = 0.12 and P = 0.67 in control fetuses) or body weight (r = 0.16 and P = 0.47 in IUGR fetuses; r = 0.24 and P = 0.39 in control fetuses). Mean beta-cell fraction was 2.53% in the IUGR fetuses and 2.86% in the control fetuses (P = 0.47). The percentage of beta-cells located within islets was identical in the two groups (mean 35%). Our data militate against a primary developmental pancreatic abnormality in human IUGR, leaving peripheral insulin resistance as the most likely mechanism of glucose intolerance in adults born with IUGR.

Targeted deletion of the PRL receptor: effects on islet development, insulin production, and glucose tolerance.

PRL and placental lactogen (PL) stimulate beta-cell proliferation and insulin gene transcription in isolated islets and rat insulinoma cells, but the roles of the lactogenic hormones in islet development and insulin production in vivo remain unclear. To clarify the roles of the lactogens in pancreatic development and function, we measured islet density (number of islets/cm(2)) and mean islet size, beta-cell mass, pancreatic insulin mRNA levels, islet insulin content, and the insulin secretory response to glucose in an experimental model of lactogen resistance: the PRL receptor (PRLR)-deficient mouse. We then measured plasma glucose concentrations after ip injections of glucose or insulin. Compared with wild-type littermates, PRLR-deficient mice had 26-42% reductions (P < 0.01) in islet density and beta-cell mass. The reductions in islet density and beta-cell mass were noted as early as 3 wk of age and persisted through 8 months of age and were observed in both male and female mice. Pancreatic islets of PRLR-deficient mice were smaller than those of wild-type mice at weaning but not in adulthood. Pancreatic insulin mRNA levels were 20-30% lower (P < 0.05) in adult PRLR-deficient mice than in wild-type mice, and the insulin content of isolated islets was reduced by 16-25%. The insulin secretory response to ip glucose was blunted in PRLR-deficient males in vivo (P < 0.05) and in isolated islets of PRLR-deficient females and males in vitro (P < 0.01). Fasting blood glucose concentrations in PRLR-deficient mice were normal, but glucose levels after an ip glucose load were 10-20% higher (P < 0.02) than those in wild-type mice. On the other hand, the glucose response to ip insulin was normal. Our observations establish a physiologic role for lactogens in islet development and function.

Fetal PGC-1α overexpression programs adult pancreatic ß-cell dysfunction.

Adult ß-cell dysfunction, a hallmark of type 2 diabetes, can be programmed by adverse fetal environment. We have shown that fetal glucocorticoids (GCs) participate in this programming through inhibition of ß-cell development. Here we have investigated the molecular mechanisms underlying this regulation. We showed that GCs stimulate the expression of peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α), a coregulator of the GCs receptor (GR), and that the overexpression of PGC-1α represses genes important for ß-cell development and function. More precisely, PGC-1α inhibited the expression of the key ß-cell transcription factor pancreatic duodenal homeobox 1 (Pdx1). This repression required the GR and was mediated through binding of a GR/PGC-1α complex to the Pdx1 promoter. To explore PGC-1α function, we generated mice with inducible ß-cell PGC-1α overexpression. Mice overexpressing PGC-1α exhibited at adult age impaired glucose tolerance associated with reduced insulin secretion, decreased ß-cell mass, and ß-cell hypotrophy. Interestingly, PGC-1α expression in fetal life only was sufficient to impair adult ß-cell function whereas ß-cell PGC-1α overexpression from adult age had no consequence on ß-cell function. Altogether, our results demonstrate that the GR and PGC-1α participate in the fetal programming of adult ß-cell function through inhibition of Pdx1 expression.

Novel transgenic mice for inducible gene overexpression in pancreatic cells define glucocorticoid receptor-mediated regulations of beta cells.

Conditional gene deletion in specific cell populations has helped the understanding of pancreas development. Using this approach, we have shown that deleting the glucocorticoid receptor (GR) gene in pancreatic precursor cells leads to a doubled beta-cell mass. Here, we provide genetic tools that permit a temporally and spatially controlled expression of target genes in pancreatic cells using the Tetracycline inducible system. To efficiently target the Tetracycline transactivator (tTA) in specific cell populations, we generated Bacterial Artificial Chromosomes (BAC) transgenic mice expressing the improved Tetracycline transactivator (itTA) either in pancreatic progenitor cells expressing the transcription factor Pdx1 (BAC-Pdx1-itTA), or in beta cells expressing the insulin1 gene (BAC-Ins1-itTA). In the two transgenic models, itTA-mediated activation of reporter genes was efficient and subject to regulation by Doxycycline (Dox). The analysis of a tetracycline-regulated LacZ reporter gene shows that in BAC-Pdx1-itTA mice, itTA is expressed from embryonic (E) day 11.5 in all pancreatic precursor cells. In the adult pancreas, itTA is active in mature beta, delta cells and in few acinar cells. In BAC-Ins1-itTA mice tTA is active from E13.5 and is restricted to beta cells in fetal and adult pancreas. In both lines, tTA activity was suppressed by Dox treatment and re-induced after Dox removal. Using these transgenic lines, we overexpressed the GR in selective pancreatic cell populations and found that overexpression in precursor cells altered adult beta-cell fraction but not glucose tolerance. In contrast, GR overexpression in mature beta cells did not alter beta-cell fraction but impaired glucose tolerance with insufficient insulin secretion. In conclusion, these new itTA mouse models will allow fine-tuning of gene expression to investigate gene function in pancreatic biology and help us understand how glucocorticoid signaling affects on the long-term distinct aspects of beta-cell biology.

Maternal stress alters endocrine function of the feto-placental unit in rats.

Prenatal stress (PS) can cause early and long-term developmental effects resulting in part from altered maternal and/or fetal glucocorticoid exposure. The aim of the present study was to assess the impact of chronic restraint stress during late gestation on feto-placental unit physiology and function in embryonic (E) day 21 male rat fetuses. Chronic stress decreased body weight gain and food intake of the dams and increased their adrenal weight. In the placenta of PS rats, the expression of glucose transporter type 1 (GLUT1) was decreased, whereas GLUT3 and GLUT4 were slightly increased. Moreover, placental expression and activity of the glucocorticoid "barrier" enzyme 11beta-hydroxysteroid dehydrogenase type 2 was strongly reduced. At E21, PS fetuses exhibited decreased body, adrenal pancreas, and testis weights. These alterations were associated with reduced pancreatic beta-cell mass, plasma levels of glucose, growth hormone, and ACTH, whereas corticosterone, insulin, IGF-1, and CBG levels were unaffected. These data emphasize the impact of PS on both fetal growth and endocrine function as well as on placental physiology, suggesting that PS could program processes implied in adult biology and pathophysiology.