Insulin signal transduction in rat small intestine: role of MAP kinases in expression of mucosal hydrolases

Marandi, Soheila; Keyser, Nadine De; Saliez, Alain; Maernoudt, Anne-Sophie; Sokal, Étienne; Stilmant, Catherine; Rider, Mark H.; Buts, Jean-Paul

doi:10.1152/ajpgi.2001.280.2.g229

Cited by 26 publications

(43 citation statements)

References 56 publications

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“…The method of Rothenberg et al (16) was used with slight adaptations (12). Briefly, samples of intestinal mucosa were homogenized for 1 min in a solubilization buffer (1:5 vol/vol) maintained at 100°C in a water bath (2 min) with an Ultraturax generator (Janke and Kunkel, Staugen, Germany) operated at maximum speed.…”

Section: Reagentsmentioning

confidence: 99%

“…Immunoprecipitated proteins were separated by SDS-PAGE in 10% polyacrylamide gels as described previously (4,12). Electrotransfer of proteins to polyvinylidene difluoride membranes was performed for 90 min at 50 V as described by Towbin et al (18).…”

Section: Electrophoresis and Immunoblottingmentioning

confidence: 99%

“…The blots were then incubated with 50 Ci of 125 I-labeled protein A (Amersham) in 10 mL of blocking buffer for 1 h at 22°C and washed again as described above. Bound proteins were detected by autoradiography using 24 ϫ 30 cm Fuji films (St-Nicolas, Belgium) at Ϫ70°C for 24 -72 h as described previously (4,12). Equivalent amounts of proteins determined by the method of Lowry et al (19) were immunoprecipitated, and equal amounts of immunoprecipitated material were layered onto gel slots.…”

Section: Electrophoresis and Immunoblottingmentioning

confidence: 99%

“…The final step of the signal leads to the activation of the SI gene promoter with a dose-dependent accumulation of SI mRNA (6), probably by the binding of a nuclear transcription factor [hepatocyte nuclear factor 1, (10,11)] to regulatory elements located upstream of the SI gene promoter (10,11). A recent study (12) has shown that the insulin signal that stimulates BBM hydrolases would be regulated by the cascade of MAP kinases and not by PI-3 kinase or protein kinase B. The MAP kinase cascade activation is mediated by a dualspecificity kinase, termed MKK, which in turn is activated upstream by Raf oncoproteins (9).…”

mentioning

confidence: 99%

“…Likewise, in suckling and weaning rats, exogenous insulin stimulates the ontogenic expression of lactase and maltase with enzyme responses proportional to the dose of insulin given (6). These effects are mediated by the binding of the hormone to the extramembranous ␣-subunits of the insulin receptor and by the autophosphorylation of the tyrosine kinase domain of the receptor (4,7,12). In a preliminary study (12), we have shown that the postreceptor pathway transducing the signal downstream is not mediated by PI-3 kinase but likely by the cascade of Raf-Ras-GAP (GTPaseactivating protein) phosphorylations leading to the activation of ERKs.…”

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confidence: 99%

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Ontogeny of MAP Kinases in Rat Small Intestine: Premature Stimulation by Insulin of BBM Hydrolases Is Regulated by ERKs but not by p-38 MAP Kinase

Marandi

2002

Pediatric Research

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Although mitogen-activating protein (MAP) kinases are crucial signal transduction molecules regulating cellular proliferation, differentiation, and morphology, their ontogenic changes in the small intestine have not been analyzed. Also, it remains unknown which pathway of activated MAP kinases regulates the expression of brush border membrane hydrolases during growth. Therefore, we have analyzed the mucosal distribution, ontogeny, and responses to insulin and to inhibitors of p44, p42, and p38 MAP kinases in immature and mature enterocytes using Western blot analysis and autoradiography after immunoprecipitation, immunohistochemistry, and in vitro phosphorylation assays. Between d 10 and 40 postpartum, diphosphorylated active p44/p42 extracellular regulated protein kinases (ERKs) increased in abundance compared with total immunoprecipitated ERKs, and were highly responsive to exogenous insulin. In concordance, ERK total activity increased by 4-fold during the same period of growth and was further enhanced 2-fold by exogenous insulin. In weaning rats, ERKs were mainly located in membranes of villus cells and with less intensity in crypt cells. By contrast, p38 MAP kinase was unresponsive to insulin and was confined to nuclei. Administration to sucklings of PD 098059, a specific inhibitor of ERKs, not only inhibited the premature stimulation of sucrase, lactase, and maltase total activities in response to exogenous insulin, but also depressed the natural expression of these brush border membrane enzymes in the absence of insulin stimulation.In concordance, administration of SB 203580, a specific inhibitor of p38 MAP kinase, failed to inhibit both the response of brush border membrane hydrolases to insulin and their natural expression in the absence of insulin stimulation. We conclude that the ontogenic expression of brush border membrane hydrolases and their premature stimulation by insulin are regulated at least in part by the activation of p44/p42 The onset of weaning (d 14 -17) in the suckling rat is a critical period during which immature enterocytes exhibit elevated responsiveness to insulin (1). At this time, plasma insulin levels rise markedly (2), whereas milk-borne insulin is still active (3), allowing optimal interaction of the hormone with intestinal IR, which are located on both endoluminal and basolateral membranes of the cell (4). After weaning, the 2-fold decrease in IR concentration is associated with a reduction in responsiveness of mature enterocytes to the hormone (1, 5). Our recent studies (6, 7) suggest that the premature induction of SI is triggered by the binding of the hormone to the extracellular ␣-receptor subunit, allowing autophosphorylation of the tyrosine-kinase intrinsic to the juxtamembrane and

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Section: Reagentsmentioning

confidence: 99%

Section: Electrophoresis and Immunoblottingmentioning

confidence: 99%

Section: Electrophoresis and Immunoblottingmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Ontogeny of MAP Kinases in Rat Small Intestine: Premature Stimulation by Insulin of BBM Hydrolases Is Regulated by ERKs but not by p-38 MAP Kinase

Marandi

2002

Pediatric Research

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Intestinal and Systemic Effects of Oral Insulin Supplementation in Rats After Weaning

et al. 2005

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Oral insulin has intestinal trophic effects in suckling animals. In mice, lower glucose and lipid levels may be seen when oral insulin is given after the weaning period. The purpose of the present study is to examine local and systemic effects of oral insulin supplementation in rats in the postweaning period. Immediately after weaning, Sprague-Dawley rats received either drinking water (controls) or oral insulin in their drinking water (1 U/ml) for either 1 week or 6 weeks. Intestinal mucosal parameters (bowel and mucosal weight, mucosal DNA and protein) and histological changes were examined in all study groups. Glucose levels were monitored weekly, and at the end of the study, blood levels of glucose, lipids, and insulin were measured in the fasting state. After 1 week of insulin supplementation, mucosal weight in duodenum and jejunum as well as jejunal DNA content were significantly higher in insulin-supplemented rats compared to controls. Duodenal circumference and villus height in jejunum were significantly higher in insulin-supplemented rats compared to controls on both day 7 and day 42. Total cholesterol levels were significantly lower in the study group compared with the controls. We conclude that oral insulin supplementation exerts intestinal trophic effects, as well as systemic effects in the postweaning period in rats.

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Oral Insulin Enhances Intestinal Regrowth Following Massive Small Bowel Resection in Rat

et al. 2005

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Experimental studies have suggested that insulin (INS) plays an important role in small intestinal growth and development. In the present study we investigated the effect of oral INS on structural intestinal adaptation and enterocyte proliferation and loss via apoptosis in a rat model of short bowel syndrome (SBS). Male Sprague-Dawley rats were divided into three experimental groups: sham rats underwent bowel transection, SBS rats underwent 75% small bowel resection, and SBS-INS rats underwent bowel resection and were treated with oral INS given in the drinking water from the 3rd to the 15th postoperative day. Parameters of intestinal adaptation (bowel and mucosal weight, mucosal DNA and protein, villous height, and crypt depth), enterocyte proliferation, and apoptosis were determined on day 15. SBS-INS rats demonstrated a significant increase (vs SBS rats) in jejunal and ileal overall bowel and mucosal weight, ileal mucosal DNA and protein, ileal villous height, and crypt depth. SBS-INS rats also showed an increased cell proliferation index in jejunum and ileum and decreased apoptotic index in jejunum compared to SBS animals. In conclusion, in a rat model of SBS, oral INS strongly enhances intestinal adaptation. Possible mechanisms may include increased cell proliferation and decreased enterocyte loss via apoptosis.

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Insulin signal transduction in rat small intestine: role of MAP kinases in expression of mucosal hydrolases

Cited by 26 publications

References 56 publications

Ontogeny of MAP Kinases in Rat Small Intestine: Premature Stimulation by Insulin of BBM Hydrolases Is Regulated by ERKs but not by p-38 MAP Kinase

Ontogeny of MAP Kinases in Rat Small Intestine: Premature Stimulation by Insulin of BBM Hydrolases Is Regulated by ERKs but not by p-38 MAP Kinase

Intestinal and Systemic Effects of Oral Insulin Supplementation in Rats After Weaning

Oral Insulin Enhances Intestinal Regrowth Following Massive Small Bowel Resection in Rat

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