HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Abstract Full Text (PDF) Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Serradas, P. Articles by Portha, B. Search for Related Content PubMed PubMed Citation Articles by Serradas, P. Articles by Portha, B. Social Bookmarking                What's this?

Fetal Insulin-Like Growth Factor-2 Production Is Impaired in the GK Rat Model of Type 2 Diabetes

¹ Laboratory of Physiopathology of Nutrition, Université Paris, Paris, France
² Instituto de Bioquimica, Facultad de Farmacia, Ciudad Universitaria, Madrid, Spain

	ABSTRACT

TOP ABSTRACT INTRODUCTION RESEARCH DESIGN AND METHODS RESULTS DISCUSSION REFERENCES

 
At late fetal age (21.5 days postcoitum [dpc]), GK rats present a severely reduced ß-cell mass compared with Wistar rats. This anomaly largely antedates the onset of hyperglycemia in GK rats. Thus, the ß-cell mass deficit could represent the primary defect leading to type 2 diabetes in the adult. The aim of this work was to investigate, in GK fetuses at the end of fetal age (21.5 dpc), whether impaired availability of growth factors such as insulin, growth hormone, and IGFs and their IGF binding proteins (IGFBPs) could be instrumental in this anomaly. Although it confirms that GK fetuses are hypoinsulinemic despite enhanced plasma glucose level due to maternal hyperglycemia, the present study shows for the first time that IGF-2 expression in the liver and pancreas and IGF-2 serum levels are decreased in GK fetuses. Serum level as well as liver and pancreatic mRNA expression of IGFBP-2 were found to be normal in GK fetuses, whereas serum level and liver mRNA expression of IGFBP-1 were increased. Finally, we found that the maximal ß-cell mitogenic response to IGFs in vitro is kept intact, therefore suggesting that the direct biological action of IGFs on fetal GK ß-cells is not grossly impaired. In conclusion, in GK fetuses at 21.5 dpc, the defective IGF-2 production appears to be an early landmark in the pathological sequence leading to retardation of ß-cell growth in the fetal GK rat.

	INTRODUCTION

TOP ABSTRACT INTRODUCTION RESEARCH DESIGN AND METHODS RESULTS DISCUSSION REFERENCES

	RESEARCH DESIGN AND METHODS

TOP ABSTRACT INTRODUCTION RESEARCH DESIGN AND METHODS RESULTS DISCUSSION REFERENCES

 
Animals and samples.
Pregnant GK and Wistar rats were obtained from our local colony. The morning of the discovery of the vaginal plug was taken as day 0.5 dpc. On day 21.5, dpc pregnant rats were anesthetized with pentobarbital sodium (1 ml/kg body wt i.p.; Sanofi Santé Animale, Sanofi, France). Fetal blood samples were collected at the level of the axillary vessels and centrifuged, and plasma (from one fetus) or serum (from two fetuses) were stored at -20°C until assayed. Pancreases (from five fetuses) and a piece of liver (from each fetus) were rapidly excised from fetuses, frozen in liquid nitrogen, and then stored at -70°C until RNA preparation.

Determination of plasma glucose, insulin, and GH levels.
Plasma glucose was determined with a glucose analyzer (Beckman Instruments, Fullerton, CA). Immunoreactive insulin plasma was estimated as previously described (8). GH was determined in the plasma of fetuses with a rat GH ¹²⁵I assay system (Biotrak; Amersham Life Science, Amersham, U.K.). The radioimmunoassay was carried out according to the kit protocol. The sensitivity of the assay was 1.6 ng/ml.

Iodination, purification, and determination of serum IGF-1 and -2.
Recombinant human IGF-1 and -2 were labeled by a modified chloramine T method (9,10). The specific activity achieved was 90–175 µCi/µg for both peptides. Before IGF-1 and -2 determination, serum IGFBPs were removed by standard acid gel filtration. This method has proved to be the most reliable one for use with rat serum in developing stages (9,10).

The radioimmunoassay for IGF-1 and rat liver membrane receptor assay for IGF-2 were carried out as previously described (9,10). The coefficients of variation within and between assay were 8.0 and 12.4%, respectively. Recombinant human IGF-I and -II (Boehringer Mannheim, Leverkusen, Germany) were used for iodination.

Western immunoblotting and determination of serum IGFBP-1 and -2.
Western immunoblots for enhanced chemiluminescence were performed in polyvinylidene fluoride (PVDF) immobilon-P membranes (Millipore, Madrid). PVDF membranes were blocked with 5% (wt/vol) nonfat dry milk for 60 min in Tris-buffered saline (TBS; 0.01 mol/l Tris and NaCl 0.15 mol/l, pH 8) with 0.05% Tween-20. Membranes were then incubated with a 1:100 dilution (as suggested by the manufacturer) of affinity-purified goat polyclonal anti-rat IGFBP-1 or -rat IGFBP-2 (Santa Cruz Biotechnology, Madrid) in the same buffer (TBS-Tween plus 5% nonfat dry milk) at 4°C overnight, after which the membrane was washed three times for 10 min in TBS-Tween. After a 1-h incubation at room temperature with a 1:1,000 dilution of anti-goat IgG-horseradish peroxidase in TBS-Tween plus 5% nonfat dry milk, the membrane was washed three times with TBS-Tween and finally once with TBS alone. Antigen-antibody complexes were detected after an enhanced chemiluminescence (hyperfilm ECL; Amersham, Madrid).

Preparation of total RNA.
Total RNA was prepared by homogenization of fetal pancreases and livers in guanidinium thiocyanate as originally described (11). RNA concentration was determined by absorbance at 260 nm. Samples were electrophoresed through 1.1% agarose and 2.2 mol/l formaldehyde gels and then stained with ethidium bromide to render the 28S and 18S ribosomal RNA visible and thereby confirm the integrity of the RNA and normalize the quantity of RNA in the different lanes. A pT7 RNA 18S anti-sense (Ambion, Austin, TX) was used for lane loading control.

Riboprobes.
Rat IGF-1 and -2 and IGFBP-1 and -2 cDNAs were kindly provided by Drs. C.T. Roberts Jr. and D. LeRoith (National Institutes of Health, Bethesda, MD). Rat IGF-I cDNA ligated into a pGEM-3 plasmid (Promega Biotech, Madison, WI) was linearized with HindIII, and an anti-sense riboprobe was produced by T7 RNA polymerase. The size of the protected fragment represented in the figures (IGF-Ib) was 386 bp. Rat IGF-II cDNA ligated into a pGEM-3 plasmid was linearized with HindIII and incubated with T7 RNA polymerase to generate a riboprobe that recognized a fragment of 700 bp. Rat IGFBP-1 cDNA, ligated into a pGEM-3 plasmid, was linearized with HindIII and incubated with T7 RNA polymerase to generate an anti-sense riboprobe that recognizes two fragments of 300 and 700 bases. Rat IGFBP-2 cDNA, ligated into a pGEM-4Z (Promega Biotech, Madison, WI) plasmid, was linearized with HindIII and incubated with SP6 RNA polymerase to generate a 550 base anti-sense riboprobe devoid of pGEM-4Z complementary sequences. pT7 RNA 18S was incubated with T7 RNA polymerase to produce a 109 nucleotide runoff transcript, 80 nucleotides of which are complementary to human 18S ribosomal RNA. (³²P)UTP was purchased from ICN (Nuclear Iberica, Madrid). The Riboprobe Gemini II Core System (Promega) was used for the generation of RNA probes.

Solution hybridization/RNase protection assay.
Solution hybridization/RNase protection assays were performed as previously described (10,12). Autoradiography was performed at -70°C against a Hyperfilm MP film between intensifying screens. Bands representing protected probe fragments were quantified using a Molecular Dynamics scanning densitometer and accompanying software. RNase A and T1 were purchased from Boehringer Mannheim.

Fetal rat islet preparation and islet culture with IGFs.
Fetal islets from GK and Wistar rats were prepared according to Hellerström et al. (13) as previously described (8). At the end of the 6-day culture period, 40 fetal islets in each group were collected under a stereomicroscope and further cultured for 2 days in RPMI 1640 medium (Bio Whittaker, Verviers, Belgium) supplemented with 2 mmol/l glutamine (Bio Whittaker), 1% heat-inactivated fetal bovine serum (Bio Whittaker), and 100 ng/ml IGF-1 (R&D Systems, Abingdon, U.K.) or 100 ng/ml IGF-2 (R&D Systems). The culture dishes were kept at 37°C in a humidified atmosphere of 5% CO₂ in air. The complete culture medium was changed the next day.

ß-Cell replication.
To measure ß-cell replication in isolated fetal islets, 5'-bromo-2'-deoxyuridine (BrdU) (Amersham, Amersham, U.K.) was incorporated in newly synthesized DNA and therefore labeled replicating cells. In each group of fetal islets, 1 h before the end of islet cultures, BrdU was added at 100 µmol/l final concentration. Thereafter, islets were collected under stereomicroscope, fixed, and then processed for serial sections as previously described (8). Islets sections were doubled-stained for BrdU, using a cell proliferation kit (Amersham International, Amersham, U.K.), and insulin. Sections were incubated with a mouse monoclonal antibody anti-BrdU diluted in a nuclease solution (according to the kit protocol) for 1 h at room temperature and washed with Tris 0.05 mol/l, pH 7.6. Thereafter, they were incubated with an affinity-purified peroxidase anti-mouse IgG and stained with DAB using a peroxidase substrate kit 3,3'-diaminobenzidine-tetra-hydrochloride (DAB). Sections were then incubated with guinea pig anti-insulin antibody for 1 h as described above and then with alkaline phosphatase-conjugated goat anti-guinea pig IgG for 45 min (Dako, Trappes France). The activity of the antibody-alkaline phosphatase complex was revealed with an alkaline phosphatase substrate kit (Valbiotech, Paris, France). Sections were mounted in Eukitt (Labonord, Templemars, France). On these sections, ß-cells showed red cytosol, and BrdU-positive ß-cell appeared with brown nuclei. A mean of 250 ß-cells were counted per islet at a final magnification of 1000x. The proportion of BrdU-positive ß-cell nuclei to total ß-cell nuclei was calculated. The result represents the percentage ß-cell replicative rate in a 1-h interval (BrdU labeling index of ß-cells).

Statistical analysis.
All data are presented as means ± SE. Comparison between groups were evaluated using Student’s unpaired t test. P < 0.05 was considered significant.

	RESULTS

TOP ABSTRACT INTRODUCTION RESEARCH DESIGN AND METHODS RESULTS DISCUSSION REFERENCES

 
Biological characteristics of Wistar and GK fetuses at 21.5 dpc.
Body weight was similar in the two groups of fetuses (Table 1). GK pancreases used for RNase protection assay (determination of IGF and IGFBP mRNA expression) showed a lower (P < 0.001) weight than Wistar pancreases. By contrast, GK fetuses exhibited a higher plasma glucose concentration and a lower plasma insulin level (P < 0.001) as compared with values in Wistar fetuses. Plasma GH levels in GK fetuses were slightly increased (P < 0.05) as compared with Wistar levels.

View larger version (29K): [in this window] [in a new window]   FIG. 1. A: Serum concentrations of IGF-1 and -2 in Wistar () and GK () fetuses at 21.5 dpc. B: Serum IGFBP-1 and -2 levels in Wistar () and GK () fetuses at 21.5 dpc. Left panel: Representative Western immunoblot of IGFBP-1 and -2 in Wistar and GK fetuses. Right panel: Densitometric measurements of bands from Western immunoblot are expressed as percent of the corresponding Wistar values. Values are means ± SE for 7–11 observations in each group. Fetuses were obtained from three to five different litters. *P < 0.001.

View larger version (43K): [in this window] [in a new window]   FIG. 2. A: RNase protection assay of liver IGF-1 and -2 mRNA transcripts in Wistar () and GK () fetuses at 21.5 dpc. Densitometric measurements of protected probe fragments are expressed as percent of the corresponding Wistar fetuses. B: RNase protection assay of liver IGFBP-1 and -2 mRNA transcripts in Wistar () and GK () fetuses at 21.5 dpc. Densitometric measurements of protected probe fragments are expressed as percent of the corresponding Wistar fetuses. 18S ribosomal antisense assayed in the same samples are shown beneath the IGF and IGFBP bands; + and - designate riboprobe lanes treated with or without RNases, respectively. Representative experiments are shown in the figure. Values are means ± SE for six to eight observations in each group. Fetuses were obtained from four different litters. *P < 0.05; **P < 0.01.

Pancreas IGF and IGFBP mRNA expression in Wistar and GK fetuses.
Densitometric measurements of protected probe fragments are expressed as percent of the corresponding Wistar fetuses (Fig. 3). Whereas pancreas IGF-1 mRNA expression in GK fetuses was similar to that in Wistar fetuses, IGF-2 mRNA expression was decreased (P < 0.001) by 55% in GK pancreas. IGFBP-1 and -2 mRNA expression were similar in the two groups of fetuses.

View larger version (41K): [in this window] [in a new window]   FIG. 3. A: RNase protection assay of pancreas IGF-1 and -2 mRNA transcripts in Wistar () and GK () fetuses at 21.5 dpc. Densitometric measurements of protected probe fragments are expressed as percent of the corresponding Wistar fetuses. B: RNase protection assay of pancreas IGFBP-1 and -2 mRNA transcripts in in Wistar () and GK () fetuses at 21.5 dpc. Densitometric measurements of protected probe fragments are expressed as percent of the corresponding Wistar fetuses. 18S ribosomal anti-sense assayed in the same samples are shown beneath the IGF and IGFBP bands; + and - designate riboprobe lanes treated with or without RNases, respectively. Representative experiments are shown in the figure. Values are means ± SE for six to seven observations in each group. Fetuses were obtained from seven to nine different litters. *P < 0.001.

View larger version (32K): [in this window] [in a new window]   FIG. 4. BrdU labeling index of ß-cells in isolated fetal islets from Wistar (W) and GK rats. Isolated fetal islets obtained after 6 days, culture were further cultured for 2 days without (ast;) or with 100 ng/ml IGF-1 () or 100 ng/ml IGF-2 ().Values are means ± SE. BrdU labeling index was determinated in each condition in 14–19 isolated fetal islets. Fetal islets were obtained from three to four independent islet cultures. *P < 0.05 and **P < 0.01 as compared with the respective values obtained in the absence of IGF.

	DISCUSSION

TOP ABSTRACT INTRODUCTION RESEARCH DESIGN AND METHODS RESULTS DISCUSSION REFERENCES

Although it confirms that GK fetuses are hypoinsulinemic despite enhanced plasma glucose level due to maternal hyperglycemia, the present study shows for the first time that IGF-2 expression in the liver and pancreas and IGF-2 serum levels are decreased in GK fetuses.

IGFs are locally produced by pancreas, where they act in an autocrine or paracrine manner and are involved in the regulation of islet growth and differentiation (5). We have previously shown that the reduced ß-cell mass in GK fetuses is due to an early impaired rate of ß-cell neogenesis, because poor proliferation and/or survival of endocrine precursor cells leads to early defective development of the ß-cell mass (3). Thus, the reduced IGF-2 serum level together with the reduced expression of IGF-2 in pancreas of GK fetuses could play a crucial role in the anomaly of ß-cell mass in the GK fetuses. This is substantiated by the recent demonstration that an increased expression of IGF-2 under the control of the rat insulin promoter in ß-cells of transgenic mice led to ß-cell hyperplasia (14). In a rat model of increased islet number induced by high- carbohydrate feeding in the neonate, IGF-2 expression was found increased within the pancreatic ductal epithelium, and it may contribute to the associated higher rate of neogenesis (15). There is also clear evidence that IGF-2 inhibits cell apoptosis in many cell types. Hill et al. (16) have demonstrated that increased and persistent circulating IGF-2 in neonatal transgenic mice suppresses developmental apoptosis in the pancreatic islets. Conversely, Petrik and al. (17) have suggested that a reduced pancreatic expression of IGF-2 may contribute to the increased apoptosis seen in the fetus after low-protein diet. However, it is unlikely that the reduced pancreatic expression of IGF-2 observed in GK fetuses may contribute to an increased ß-cell death because ß-cell apoptosis rate was not increased in GK fetuses at late fetal age (3). Due to our observation that the pancreatic expression of IGF-2 is decreased by 55% in GK fetuses, the anomaly of the IGF-2 expression in pancreas of GK fetuses could be the reflection of the reduced ß-cell mass (by 60%) observed at this stage. However, in the present study, we observed that the IGF-1 pancreatic expression is similar in GK and Wistar fetuses, and it is known that IGF-1 is produced by fetal and neonatal rat pancreatic islets (18,19). Therefore, the reduced pancreatic IGF-2 expression in GK fetuses cannot be solely attributed to the decreased ß-cell mass observed at this stage. Moreover, whereas pancreatic expression of IGF-2 in normal fetus, as shown by in situ hybridization technique, is largely associated with pancreatic endocrine cells (20), it has also been reported within the pancreatic ductal epithelium in neonatal rat pancreas (15).

Recent studies in our laboratory have suggested that the growth and endocrine differentiation of GK and Wistar pancreatic rudiments are identical when followed in vitro (3). Thus, as far as the in vivo fetal situation is recapitulated by the in vitro development of the GK rudiments, the anomaly of the GK rat leading to deficient pancreatic endocrine cell differentiation in vivo could mainly result from a deficiency of one (or several) extrapancreatic factor(s) (3). Because it is known that in the developing normal pancreas, IGF-2 is involved in the regulation of both islet growth and differentiation (5), the reduced circulating IGF-2 levels in GK fetuses could therefore play a crucial role in the anomaly of ß-cell mass in the GK fetuses. As circulating levels of IGF-2 in the rat fetus derive predominantly from the hepatic production site (5), the decreased serum IGF-2 levels are probably the result of the decreased IGF-2 mRNA hepatic expression. Involvement of circulating insulin and plasma glucose levels in the regulation of liver IGFs production at fetal stages has been repeatedly reported (21), whereas the role of plasma GH on fetal IGF regulation is considered as negligible (10,21). Therefore, it is important to take into account the IGF data available in a rat model of induced (streptozotocin) gestational diabetes with fetal hyperglycemia and hypoinsulinemia in the range of the values found in GK fetuses (10). In this study (10), the fetal serum IGF-2 (and IGF-1) level as well as the fetal liver IGF-2 (and IGF-1) mRNA expression were found to be clearly increased, which is in accordance with reports showing that high glucose in vivo (22) or in vitro (23) increases liver IGF-2 expression. The only in vivo situation with a reported decrease of the serum IGF-2 was found in fetuses from undernourished mothers (10). However, in this last situation, both fetal liver IGF-2 (and IGF-1) mRNA levels were still significantly increased as compared with normal fetuses. Taken together, these observations suggest that the situation in the GK fetuses is a very unique one because the decreased IGF-2 level in the serum and its decreased expression in the liver seems to be largely independent of the variations of fetal insulin and glucose levels. Thus, IGF-2 defective production in the GK fetuses may reflect a primary and generalized anomaly. Such a view is also consistent with the results of previous genetic studies reporting that a locus containing the gene encoding the IGF-2 is associated with diabetes phenotype in the GK rat (24). Whereas defective IGF-2 appears to be an early landmark in the pathological sequence leading to retardation of ß-cell growth in the fetal GK rat, the pancreatic IGF-2 status in the aging adult GK animal is quite different. Using the swedish GK colony, Höög et al. (25) have reported that an inappropriately processed IGF-2 of high molecular weight accumulates in pancreas from 6-month-old GK rats. More immunoreactive IGF-2 was localized together with insulin to secretory granules in a subset of large and irregular-shaped islets than in either GK rat islets with normal structure or islets from normal rats (26). Because this increase in the high molecular weight form of IGF-2 in the GK pancreas appears to be a late consequence of the early reduction of ß-cell number/function in the GK model, it might be triggered by long-term hyperglycemia and might represent an islet self-damaging process disrupting normal arrangement of islet architecture through fibroblast proliferation and collagen deposition.

In view of the reported ability of IGFBPs to modulate IGF bioactivity, we examined serum and tissular expression of IGFBP-1 and -2 in GK fetuses. In general, IGFBP-2 appears to inhibit IGF actions, particularly those of IGF-2 (4). We report here normal serum, liver, and pancreatic mRNA expression of IGFBP-2 in GK fetuses. This conclusion is not at odds with the general agreement that few changes in liver IGFBP-2 mRNA were found in fetuses from experimental diabetic (10) or undernourished mothers (6). By contrast, an increased serum and liver mRNA expression of IGFBP-1 was found in GK fetuses. Insulin appears to play a major role in regulating IGFBP-1 gene transcription in adult animals, i.e., IGFBP-1 transcription is high in diabetic animals and rapidly reduced to normal values after insulin treatment (27,28). The hypoinsulinemic status of GK fetuses could therefore contribute to the high levels of IGFBP-1.

Finally, we have tested the possibility that direct biological action of IGFs on fetal GK ß-cell is impaired. Our in vitro results showed that IGF-1 and -2 stimulate the ß-cell replication in fetal Wistar islets in accordance with a previous demonstration (29). Similarly, addition of IGF-1 or -2 to the GK isolated islets significantly increased the ß-cell replication. These effects were obtained with a submaximal IGF-2 concentration and a maximal IGF-1 concentration based in our circulating-levels evaluation and in vitro data, respectively (19,30). Therefore, we can conclude that IGF responsiveness by fetal GK islets is maintained but cannot eliminate the possibility that the sensitivity of the islet to these factors could be altered.

In conclusion, in GK fetuses at 21.5 dpc, the defective IGF-2 production appears to be an early landmark in the pathological sequence leading to retardation of ß-cell growth in the fetal GK rat.

	ACKNOWLEDGMENTS

 
This work was supported by DGICYT (Direccion General de Investigacion, Ciencia, Tecnologia, Ministerio de Educacion, Ciencia, Spain; Grant PM 97-0017), by a grant from the Ministère de l’Education Nationale, de l’Enseignement Supérieur et de la Recherche (no. 95-G-0103; program interministériel "Aliment Demain"), and by the France/Spain program for Science (Cooperation Franco-Espagnole Center National de la Recherche Scientifique/Consejo Superior Investigaciones Cientificas; projects 5249 and 7963). S. Ramos was a recipient of a fellowship from Conserjeria de Educacion y Cultura from Comunidad Autonoma de Madrid.

The authors are grateful to Mylène Vincent for expert assistance with serial sections of isolated fetal islets. They also thank Susana Fajardo for her invaluable technical help.

Parts of this work were presented at the 36th Annual Meeting of the European Association for the Study of Diabetes, Jerusalem, Israel, 17–21 September 2000, and has appeared as an abstract in Diabetologia 43 (Suppl. 1):A131, 2000.

	FOOTNOTES

 
Address correspondence and reprint requests to Dr. P. Serradas, Laboratory of Physiopathology of Nutrition, CNRS UMR 7059, Université Paris 7/Denis Diderot, 2 Place Jussieu, 75251 Paris Cedex 05, France. E-mail: serradas{at}paris7.jussieu.fr.

Received for publication 19 April 2001 and accepted in revised form 8 November 2001.

BrdU, 5'-bromo-2'-deoxyuridine; dpc, days postcoitum; GH, growth hormone; IGFBP, IGF binding protein; PVDF, polyvinylidene fluoride; TBS, Tris-buffered saline.

	REFERENCES

TOP ABSTRACT INTRODUCTION RESEARCH DESIGN AND METHODS RESULTS DISCUSSION REFERENCES

 

1. Movassat J, Saulnier C, Serradas P, Portha B: Impaired development of pancreatic beta-cell mass is a primary event during the progression to diabetes in the GK rat. Diabetologia 40:916–925, 1997[Medline]
2. Serradas P, Gangnerau MN, Giroix MH, Saulnier C, Portha B: Impaired pancreatic ß cell function in the fetal GK rat: impact of diabetic inheritance. J Clin Invest 101:899–904, 1998[Medline]
3. Miralles F, Portha B: Early development of ß-cells is impaired in the GK rat model of type 2 diabetes. Diabetes 50 (Suppl. 1):S84–S88, 2001
4. Jones JI, Clemmons DR: Insulin-like growth factors and their binding proteins: biological actions. Endocrine Rev 16:3–33, 1995[Medline]
5. Hill JD, Petrik J, Arany E: Growth factors and the regulation of fetal growth. Diabetes Care 21 (Suppl. 2):B60–B69, 1998
6. Straus DS, Ooi GT, Orlowski CC, Rechler MM: Expression of the genes for insulin-like growth factor-I (IGF-I), IGF-II, and IGF-Binding proteins-1 and -2 in fetal rat under conditions of intrauterine growth retardation caused by maternal fasting. Endocrinology 128:518–525, 1991[Abstract]
7. Cohick WS, Clemmons DR: The insulin-like growth factors. Annu Rev Physiol 55:131–153, 1993[Medline]
8. Serradas P, Giroix MH, Saulnier C, Gangnerau MN, Hakan Borg LA, Welsh M, Portha B, Welsh N: Mitochondrial deoxyribonucleic acid content is specifically decreased in adult, but not in fetal, pancreatic islets of the GK rat, a genetic model of non-insulin-dependent diabetes. Endocrinology 136:5623–5631, 1995[Abstract]
9. Rivero F, Goya L, Pascual-Leone AM: Comparaison of extraction methods for insulin-like growth factor-binding proteins prior to measurement of insulin-like growth factor-I in undernourished neonatal and adult rat serum. J Endocr 140:257–263, 1994[Abstract/Free Full Text]
10. Rivero F, Goya L, Alvarez C, Pascual-Leone AM: Effects of undernutrition and diabetes on serum and liver mRNA expression of IGFs and their binding proteins during rat development. J Endocr 145:427–440, 1995[Abstract/Free Full Text]
11. Chomczynski P, Sacchi N: Single step method of RNA isolation by acid guanidinium thiocyanate-phenol-chloroform extraction. Anal Biochem 162:156–159, 1987[Medline]
12. Goya L, Rivero F, Martin MA, Arahuetes R, Hernandez ER, Pascual-Leone AM: Effects of refeeding of undernourised and insulin treatment of diabetic neonatal rats on IGF and IGFBP. Am J Physiol 271:E223–E231, 1996[Abstract/Free Full Text]
13. Hellerström C, Lewis NJ, Borg H, Johnson R, Freinkel N: Method for large scale isolation of pancreatic islets by tissue culture of fetal pancreas. Diabetes 28:769–776, 1979[Medline]
14. Devedjian JC, George M, Casellas A, Pujol A, Visa J, Pelegrin M, Gros L, Bosh F: Transgenic mice overexpressing insulin-like growth factor-II in ß cells develop type 2 diabetes. J Clin Invest 105:731–740, 2000[Medline]
15. Petrik J, Srinivasan M, Aalinkeel R, Coukell S, Arany E, Patel MS, Hill DJ: A long-term high-carbohydrate diet causes an altered ontogeny of pancreatic islets of Langerhans in neonatal rat. Pedriatr Res 49:84–92, 2001[Medline]
16. Hill DJ, Strutt B, Arany E, Zaina S, Coukell S, Graham CF: Increased and persistent circulating insulin-like growth factor II in neonatal transgenic mice suppresses developmental apoptosis in the pancreatic islets. Endocrinology 141:1151–1157, 2000[Abstract/Free Full Text]
17. Petrik J, Reusens B, Arany E, Remacle C, Coelho C, Hoet JJ, Hill DJ: A low protein diet alters the balance of islet cell replication and apoptosis in the fetal and neonatal rat and is associated with a reduced pancreatic expression of insulin-like growth factor-II. Endocrinology 146:4861–4873, 1999
18. Scharfmann R, Corvol M, Czernichow P: Characterization of insulin-like growth factor I produced by fetal rat pancreatic islets. Diabetes 38:686–690, 1989[Abstract]
19. Romanus JA, Rabinovitch A, Rechler MM: Neonatal rat islet cell cultures synthesize insulin-like growth factor 1. Diabetes 34:696–702, 1985[Abstract]
20. Hill DJ, Hogg J, Petrik J, Arany E, Han WKM: Cellular distribution and ontogeny of insulin-like growth factors (IGFs) and IGF binding protein messengers RNAs and peptides in developing rat pancreas. J Endocrinol 160:305–317, 1999[Abstract]
21. Thissen JP, Ketelslegers JM, Underwood LE: Nutritional regulation of insulin-growth factors. Endocrine Rev 15:80–101, 1994[Medline]
22. Gluckman PD, Butler JH: Insulin-like growth factors in the fetus. In The Physiological Development of the Fetus and Newborn. Jones CT, Nathanielsz PW, Eds. New York, Academic Press, 1985, p.21–25
23. Goya L, de la Puente A, Ramos S, Martin MA, Escriva F, Pascual-Leone AM: Regulation of insulin-like growth factor-I and -II by glucose in primary cultures of fetal rat hepatocytes. J Biol Chem 274:24633–24640, 1999[Abstract/Free Full Text]
24. Gauguier D, Froguel P, Parent V, Bernard C, Bihoreau MT, Portha B, James MR, Penicaud L, Latrop M, Ktorza A: Chromosomal mapping of genetic loci associated with non-insulin dependent diabetes in the GK rat. Nat Genet 12:38–43, 1996[Medline]
25. Höög A, Sandberg-Nordqvist AC, Abdel-Halim SM, Carlsson-Skwirut C, Guenifi A, Tally M, ÖOstenson CG, Falkmer S, Sara VR, Efendic S, Shalling M, Grimelius L: Increased amounts of a high molecular weight insulin-like growth factor II (IGF-II) peptide and IGF-II messenger ribonucleic acid in pancreatic islets of diabetic GK rats. Endocrinology 137:2415–2423, 1996[Abstract]
26. Höög A, Hu W, Abdel-Halim SM, Falkmer S, Qing L, Grimelius L: Ultrastructural localization of insulin-like growth factor-2 (IGF-2) to the secretory granules of insulin cells: a study in normal and diabetic (GK) rats. Ultrastruct Pathol 21:457–466, 1997[Medline]
27. Suwanichkul A, Morris SL, Powell DR: Identification of an insulin responsive element in the promoter of the human gene for insulin-like growth factor binding protein-1. J Biol Chem 268:17063–17068, 1993[Abstract/Free Full Text]
28. Unterman TG, Patel K, Mamathre VK, Rajamohan G, Oehler DT, Becker RE: Regulation of low weight insulin-like growth factor binding proteins in experimental diabetes mellitus. Endocrinology 126:2614–2624, 1990[Abstract]
29. Swenne I: Pancreatic beta-cell growth and diabetes mellitus. Diabetologia 35:193–201, 1992[Medline]
30. Swenne I, Hill DJ, Strain AJ, Milner RDG: Growth hormone regulation of somatomedine C/insulin-like growth factor I production and DNA replication in fetal rat islets in tissue culture. Diabetes 36:288–294, 1987[Abstract]

CiteULike

Del.icio.us

Digg

Reddit

Technorati

This article has been cited by other articles:

				L.-S. Fetita, E. Sobngwi, P. Serradas, F. Calvo, and J.-F. Gautier Consequences of Fetal Exposure to Maternal Diabetes in Offspring J. Clin. Endocrinol. Metab., October 1, 2006; 91(10): 3718 - 3724. [Abstract] [Full Text] [PDF]

				G. Villuendas, J. I Botella-Carretero, A. Lopez-Bermejo, C. Gubern, W. Ricart, J. M. Fernandez-Real, J. L S. Millan, and H. F Escobar-Morreale The ACAA-insertion/deletion polymorphism at the 3' UTR of the IGF-II receptor gene is associated with type 2 diabetes and surrogate markers of insulin resistance. Eur. J. Endocrinol., August 1, 2006; 155(2): 331 - 336. [Abstract] [Full Text] [PDF]

				M. A Martin, P. Serradas, S. Ramos, E. Fernandez, L. Goya, M. N. Gangnerau, M. Lacorne, A. M. Pascual-Leone, F. Escriva, B. Portha, et al. Protein-Caloric Food Restriction Affects Insulin-Like Growth Factor System in Fetal Wistar Rat Endocrinology, March 1, 2005; 146(3): 1364 - 1371. [Abstract] [Full Text] [PDF]

				A. I. Duarte, M. S. Santos, R. Seica, and C. R. Oliveira Oxidative Stress Affects Synaptosomal {gamma}-Aminobutyric Acid and Glutamate Transport in Diabetic Rats: The Role of Insulin Diabetes, August 1, 2004; 53(8): 2110 - 2116. [Abstract] [Full Text] [PDF]

				A. E. Butler, J. Jang, T. Gurlo, M. D. Carty, W. C. Soeller, and P. C. Butler Diabetes Due to a Progressive Defect in {beta}-Cell Mass in Rats Transgenic for Human Islet Amyloid Polypeptide (HIP Rat): A New Model for Type 2 Diabetes Diabetes, June 1, 2004; 53(6): 1509 - 1516. [Abstract] [Full Text] [PDF]

This Article Abstract Full Text (PDF) Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Serradas, P. Articles by Portha, B. Search for Related Content PubMed PubMed Citation Articles by Serradas, P. Articles by Portha, B. Social Bookmarking                What's this?