Pancreatic insulin-producing β-cells have a long lifespan, such that in healthy conditions they replicate little during a lifetime. Nevertheless, they show increased self-duplication upon increased metabolic demand or after injury (i.e. β-cell loss). It is unknown if adult mammals can differentiate (regenerate) new β-cells after extreme, total β-cell loss, as in diabetes. This would imply differentiation from precursors or other heterologous (non β-cell) source. Here we show β-cell regeneration in a transgenic model of diphtheria toxin (DT)-induced acute selective near-total β-cell ablation. If given insulin, the mice survived and displayed β-cell mass augmentation with time. Lineage-tracing to label the glucagon-producing α-cells before β-cell ablation tracked large fractions of regenerated β-cells as deriving from α-cells, revealing a previously disregarded degree of pancreatic cell plasticity. Such inter-endocrine spontaneous adult cell conversion could be harnessed towards methods of producing β-cells for diabetes therapies, either in differentiation settings in vitro or in induced regeneration.

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.

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Early malnutrition decreases beta-cell mass in the first generation of offspring and impairs the subsequent beta-cell adaptation to pregnancy. The beta-cell alteration is also present in the next generation and involves a decreased expansion of the epithelial population expressing Pdx-1.

In humans, an altered control of cortisol secretion was reported in adult men born with a low birth weight making the hypothalamic-pituitary-adrenal (HPA) axis a possible primary target of early life programming. In rats, we have recently shown that maternal food restriction during late pregnancy induces both an intrauterine growth retardation and an overexposure of fetuses to maternal corticosterone, which disturb the development of the HPA axis in offspring. The first aim of this work was to investigate, in adult male rats, whether perinatal malnutrition has long-lasting effects on the HPA axis activity during both basal and stressful conditions. Moreover, as the HPA axis and sympathetic nervous system are both activated by stress, the second aim of this work was to investigate, in these rats, the adrenomedullary catecholaminergic system under basal and stressful conditions. This study was conducted on 4-month-old male rats malnourished during their perinatal life and on age-matched control animals. Under basal conditions, perinatal malnutrition reduced body weight and plasma corticosteroid-binding globulin (CBG) level but increased mineralocorticoid receptor (MR) gene expression in CA1 hippocampal area. After 30 min of restraint, perinatally malnourished (PM) rats showed increased plasma noradrenaline, adrenocorticotropin hormone (ACTH) and corticosterone concentrations similarly as controls, but calculated plasma-free corticosterone concentration was significantly higher and adrenaline level lower than controls. During the phase of recovery, PM rats showed a rapid return of plasma ACTH and corticosterone concentrations to baseline levels in comparison with controls. These data suggest that in PM rats, an elevation of basal concentrations of corticosterone, in face of reduced CBG and probably increased hippocampal MR lead to a much larger impact of corticosterone on target cells that mediate the negative-feedback mechanism on the activities of both the HPA axis and sympathoadrenal one.

Gene inactivation studies have shown that members of the Gata family of transcription factors are critical for endoderm development throughout evolution. We show here that Gata-4 and/or Gata-6 are not only expressed in the adult exocrine pancreas but also in glucagonoma and insulinoma cell lines, whereas Gata-5 is restricted to the exocrine pancreas. During pancreas development, Gata-4 is expressed already at embryonic d 10.5 and colocalizes with early glucagon+ cells at embryonic d 12.5. Gata-4 was able to transactivate the glucagon gene both in heterologous BHK-21 (nonislet Syrian baby hamster kidney) and in glucagon-producing InR1G9 cells. Using gel-mobility shift assays, we identified a complex formed with nuclear extracts from InR1G9 cells on the G5 control element (-140 to -169) of the glucagon gene promoter as Gata-4. Mutation of the GATA binding site on G5 abrogated the transcriptional activation mediated by Gata-4 and reduced basal glucagon gene promoter activity in glucagon-producing cells by 55%. Furthermore, Gata-4 acted more than additively with Forkhead box A (hepatic nuclear factor-3) to trans-activate the glucagon gene promoter. We conclude that, besides its role in endoderm differentiation, Gata-4 might be implicated in the regulation of glucagon gene expression in the fetal pancreas and that Gata activity itself may be modulated by interactions with different cofactors.

We investigated the cellular mechanisms responsible for the inability of 8-month-old previously malnourished (PM) females to adapt their -cell mass during pregnancy. The evolution during pregnancy of -cell fraction, size and proliferation was studied. At day 21 of pregnancy -cell fraction increased less in PM than in control females, compared with their non-pregnant values. A slight -cell hypertrophy was observed during pregnancy in both groups. In control females, -cell 5-bromo-2 -deoxyuridine (BrdU) labelling index (LI) increased from 0·07 0·04% before pregnancy to 1·13 0·20% at day 12 and decreased thereafter to reach again basal levels at day 21. In PM females, -cell proliferation rate was decreased at day 12 (0·74 0·15%, P<0·05) but similar to controls at all other stages studied. Separate analysis of the head and tail parts of the pancreas in control animals revealed that the -cell fraction during pregnancy increased more in the head than in the tail; similarly, BrdU LI increased 20-fold in the head and 10-fold in the tail, compared with non-pregnant values. In PM females, no adaptation of -cell fraction could be observed in the head, where BrdU LI was decreased by half at day 12 of pregnancy. In PM females the lactogenic activity was twice that of controls at day 12 whereas all -cells expressed the prolactin receptor. In conclusion, perinatal malnutrition impairs subsequent adaptation to pregnancy by decreasing -cell proliferation in the head of the pancreas at a critical time during pregnancy.

The control of glucose metabolism by pancreatic endocrine cells throughout life relies on a tight regulation of the mass of insulin-producing beta-cells. How this homoeostasis is achieved is not well understood. Over the last few years, experimental rodent models with altered beta-cell mass, and, more recently, new transgenic approaches designed to tackle this problem, have provided abundant information. Processes such as beta-cell proliferation and apoptosis, or even beta-cell differentiation from poorly characterized progenitor cells, whether immature or differentiated, appear to be implicated. A complex picture is thus emerging in which the nature of the pancreatic lesion appears to determine the kind of regenerative response. The environment formed by acinar and ductal cells, and also by vascular and neuronal structures, which surround islets and penetrate into their beta-cell core, might play crucial roles so far unsuspected, which should be explored in the near future.