Intrauterine growth retardation and postnatal acute diabetes result from insulin deficiency in double homozygous null mutants for Ins1 and Ins2 (Duvillié B, et al., Proc. Natl. Acad. Sci. USA ...94:5137-5140, 1997). The characterization of single homozygous null mutants for Ins1 or Ins2 is described here. Neither kind of mutant mice was diabetic. Immunocytochemical analysis of the islets showed normal distribution of the endocrine cells producing insulin, glucagon, somatostatin, or pancreatic polypeptide. Analysis of the expression of the functional insulin gene in Ins1-/- or Ins2-/- mice revealed a dramatic increase of Ins1 transcripts in Ins2-/- mutants. This compensatory response was quantitatively reflected by total pancreatic insulin content similar for both types of mutants and wild-type mice. Moreover, both mutants had normal plasma insulin levels and normal glucose tolerance tests. The determination of beta-cell mass by morphometry indicated beta-cell hyperplasia in the mutant mice. The beta-cell mass in Ins2-/- mice was increased almost threefold, which accounts for the increase of Ins1 transcripts in Ins2-/-mutants. This study thus contributes to evaluate the potential of increasing the beta-cell mass to compensate for low insulin production.
Growth hormone and prolactin are important growth factors for pancreatic β-cells. The effects exerted by these hormones on proliferation and on insulin synthesis and secretion in β-cells are largely ...mediated through the Janus kinase (JAK)/signal transducer and activator of transcription (STAT) signaling pathway. Suppressors of cytokine signaling (SOCS) proteins are specific inhibitors of the JAK/STAT pathway acting through a negative-feedback loop. To investigate in vivo effects of SOCS-3 in growth hormone (GH)/prolactin signaling in β-cells we generated transgenic mice with β-cell-specific overexpression of SOCS-3. The relative β-cell proliferation and volume in the mice were measured by morphometry. β-Cell volume of transgenic female mice was reduced by over 30% compared with β-cell volume in wild-type female mice. Stimulation of transgenic islets in vitro with GH showed a reduced tyrosine phosphorylation of STAT-5 when compared with wild-type islets. Transduction of primary islet cultures with adenoviruses expressing various SOCS proteins followed by stimulation with GH or glucagon-like peptide-1 (GLP-1) revealed that SOCS-3 inhibited GH- but not GLP-1-mediated islet cell proliferation, indicating that the decreased β-cell volume observed in female transgenic mice could be caused by an inhibition of GH-induced β-cell proliferation by SOCS-3. In spite of the reduced β-cell volume the transgenic female mice exhibited enhanced glucose tolerance compared with wild-type littermates following an oral glucose-tolerance test. Together these data suggest that SOCS-3 modulates cytokine signaling in pancreatic β-cells and therefore potentially could be a candidate target for development of new treatment strategies for diabetes.
Non-insulin-dependent diabetes mellitus (NIDDM) is a complex heterogeneous polygenic disease characterized mainly by insulin resistance and pancreatic beta-cell dysfunction. In recent years, several ...genetically engineered mouse models have been developed for the study of the pathophysiological consequences of defined alterations in a single gene or in a set of candidate diabetogenes. These represent new tools that are providing invaluable insights into NIDDM pathogenesis. In this review, we highlight the lessons emerging from the study of some of the transgenic or knockout mice in which the expression of key actors in insulin signaling, action or secretion has been manipulated. In addition to contributing to our knowledge of the specific roles of individual genes in the control of glucose homeostasis, these studies have made it possible to address several crucial issues in NIDDM that have remained controversial or unanswered for a number of years.
Full text
Available for:
FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Insulin receptor (IR)-deficient pups rapidly become hyperglycemic and hyperinsulinemic and die of diabetic ketoacidosis within a few days. Immunocytochemical analysis of the endocrine pancreas ...revealed that IR deficiency did not alter islet morphology or the number of beta-, alpha-, delta-, and pancreatic polypeptide (PP) cells. The lack of IR did not result in major changes in the expression of islet hormone genes or of beta-cell-specific marker genes encoding pancreas duodenum homeobox-containing transcription factor-1 (PDX-1), glucokinase (GCK), and GLUT2, as shown by reverse transcriptase-polymerase chain reaction analysis. The serum glucagon levels in IR-deficient and nondiabetic littermates were comparable. Finally, total insulin content in the pancreas of IR-deficient pups was gradually depleted, indicating sustained insulin secretion, not compensated for by increased insulin biosynthesis. These findings are discussed in light of recent results suggesting a role of IR in beta-cell function.
Exhaustive characterizations of antisera to the structurally related peptides
pancreatic polypeptide (PP), neuropeptide Y (NPY), and peptide YY (PYY) enabled us to
establish the developmental pattern ...of these peptides in rat and mouse pancreas. PYY
was the earliest detectable peptide and was present in all early appearing endocrine
cell types. NPY appeared later and occurred exclusively in a subpopulation of insulin
cells, whereas PP cells arose latest. At the earliest stage studied, all endocrine
cells stored PYY. Most of these cells also contained glucagon. Subsequently, the
endocrine cells comprised glucagon+PYY cells and glucagon+PYY+insulin cells. Later,
cells storing either only insulin or insulin+PYY appeared. Quantitations of the
relative numbers of these cell populations during development were consistent with a
precursor role of triple-positive (insulin+glucagon+PYY) cells. Moreover,
bromodeoxyuridine (BrdU) injections at E15.5 showed that a large percentage of
triple-positive cells were in S-phase and therefore were actively dividing, whereas
almost no pure insulin cells or insulin+PYY cells synthesized DNA at this time. These
results suggest that PYY-positive endocrine cells may represent precursors for mature
islet cells.
Insulin receptor null mutant mice develop severe diabetes, ketoacidosis and liver steatosis and die within 1 week after birth. Since the liver plays an essential role in the control of glucose ...homeostasis, we examined in this work whether the metabolic disorders of insulin receptor-deficient mice could be improved upon restoration of hepatic glucose metabolism by transgenic constitutive overexpression of glucokinase selectively in the liver.
We first generated transgenic mice overexpressing rat glucokinase cDNA under control of the liver-specific phenylalanine hydroxylase gene promoter. These transgenic mice were crossed with heterozygous insulin-receptor-null mutants to produce homozygous insulin-receptor-null mice overexpressing glucokinase in the liver.
The transgenic mice overexpressing glucokinase in the liver showed improved glucose tolerance and were mildly hypoglycaemic and hyperlipidaemic under starved conditions. The introduction of the glucokinase transgene in insulin receptor null mice did not prevent the development of glycosuria. However, ketoacidosis was delayed by more than 1 week and survival was prolonged to 10 to 16 days in 16% of the pups. In these longer surviving pups, serum glucose and triglyceride concentrations were lowered, hepatic glycogen stores were reconstituted and liver steatosis was absent as compared with the pups which had developed strong ketoacidosis and died earlier.
These results show that overexpression of hepatic glucokinase can compensate, in part, for the metabolic disorders developed by insulin receptor-deficient mice. This shows the importance of improving hepatic function in diabetes and must revive interest in enhancement of glucokinase activity as a therapeutic strategy for the treatment of diabetes.
Full text
Available for:
EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Insulin receptor (IR)-deficient mice develop severe diabetes mellitus, diabetic ketoacidosis (DKA) and liver steatosis and die within 1 week after birth. We examined in this work whether the ...metabolic phenotype of IR(-/-) mutants could be improved by transgenic complementation with IR selectively in the liver. We first generated transgenic mice expressing a human DNA complementary to RNA encoding a truncated constitutively activated form of IR (IRdelta) under the control of liver-specific phenylalanine hydroxylase (PAH) gene promoter. These mice presented more pronounced fasting hypoglycemia and showed slightly improved glucose tolerance as compared to controls. The transgenic mice were crossed with IR(+/-) mutants to generate IR(-/-) mice carrying the PAH-IRDelta transgene. Although such mutants developed glycosuria, DKA was delayed by more than 1 week and survival was prolonged to 8-20 days in approximately 10% of mice. In these partially rescued pups, serum glucose and triglyceride levels were lowered, hepatic glycogen stores were reconstituted and liver steatosis was absent as compared with pups which developed strong DKA and died earlier. Thus, lack of insulin action in the liver is responsible in large part for the metabolic disorders seen in IR(+/-) mice. This study should stimulate interest in therapeutic strategies aimed at improving hepatic function in diabetes.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
We report here knock-in of diphteria toxin A chain (dta) gene at the Ins2 locus, using the strategy previously employed to insert lacZ under control of the Ins2 promoter. Mutant Ins2(dta/+), ...Ins2(dta/lacZ) or Ins2(lacZ/+) mouse pups were generated by breeding and analyzed to study the effects of toxigenetic beta-cell ablation on islet development and to localize the extrapancreatic Ins2 expression site in the brain. Ins2(dta/+) and Ins2(dta/lacZ) pups developed a severe diabetic ketoacidosis and died rapidly. Histological analysis of their pancreas revealed that beta-cells completely disappeared in their islets as evidenced by loss of lacZ activity or insulin immunonostaining. beta-cell ablation did not alter the size of other islet cell populations which were normal at birth, although the glucagon-cell population was reduced by 85% at embryonic day E12.5. In the brain, comparative analysis of lacZ expression in Ins2(lacZ/+) and Ins2(dta/laZ) mice identified the choroid plexus (CP) as a major Ins2 expression site. This finding was confirmed by RT-PCR analysis of insulin transcripts in RNAs prepared from microdissected wild-type CP. Transcripts for other key beta-cell markers, with the notable exception of Pdx-1, were also found in CP RNAs. These results must revive interest in studies focused on extrapancreatic insulin gene expression.
Full text
Available for:
EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Neuropeptide Y (NPY) and peptide YY (PYY) are structurally related peptides that are considered to mediate inhibitory actions on gastrointestinal motility, secretion, and blood flow. Several receptor ...subtypes for these peptides have been identified and the Y1, Y2, Y4/PP1, Y5, and Y5/PP2/Y2b receptors have been cloned. In this article we report the immunocytochemical localization of the Y1 receptor to myenteric and submucosal nerve cell bodies, endothelial cells, and scattered endocrine-like cells of rat intestinal tract. Moreover, double immunofluorescence demonstrates that subpopulations of the Y1 receptor-positive nerve cell bodies are immunopositive for NPY, vasoactive intestinal polypeptide, and nitric oxide synthase. In part, such co-localizations were made possible by use of peroxidase-mediated deposition of tyramide, which permitted use of antisera derived from the same species. Our observations suggest the existence of multiple neuronal, endothelial, and endocrine target sites for NPY and PYY and that some of the actions of these regulatory peptides can be mediated by vasoactive intestinal peptide and nitric oxide synthase.
Neuropeptide Y, peptide YY, and pancreatic polypeptide are structurally related peptides that are considered to play a role in the regulation of pancreatic secretion and blood flow. Several receptor ...subtypes for these peptides have been identified, and the Y1, Y2, Y4/PP1, Y5, and Y5/PP2/Y2b receptors are cloned. We have prepared polyclonal peptide antibodies that recognize the Y1 receptor and now report on its localization in the adult and developing rat pancreas. In the adult pancreas, Y1 receptors were detected both in some centroacinar and intralobular duct cells and in endothelial cells. In the developing pancreas (E12.5-E16.5), Y1 receptor immunoreactivity was observed in numerous nonendocrine epithelial cells. These cells occurred in the immediate vicinity of peptide YY-positive endocrine cells. At E16.5, a fraction of these Y1 receptor-containing cells co-stored amylase. One day later, Y1 receptor immunoreactivity became restricted to pancreatic duct-like cells that occurred in close proximity to peptide YY cells. In fetal rats, intense Y1 receptor staining was also observed in endothelial cells. These observations, together with the finding of early pancreatic peptide YY expression, suggest that peptide YY produced by fetal endocrine cells may exert an action on exocrine cells, duct cells and endothelial cells during development.
PDF
