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

J. Biol. Chem., Vol. 280, Issue 45, 37489-37494, November 11, 2005

This Article Abstract Full Text (PDF) All Versions of this Article: 280/45/37489    most recent M506967200v2 M506967200v1 Submit a Letter to Editor Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map 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 Barbour, L. A. Articles by Draznin, B. Search for Related Content PubMed PubMed Citation Articles by Barbour, L. A. Articles by Draznin, B. Social Bookmarking                      What's this?

Increased P85 Is a Potent Negative Regulator of Skeletal Muscle Insulin Signaling and Induces in Vivo Insulin Resistance Associated with Growth Hormone Excess^*

Linda A. Barbour, Shaikh Mizanoor Rahman¶, Inga Gurevich||, J. Wayne Leitner||, Stephanie J. Fischer¶, Michael D. Roper¶, Trina A. Knotts¶, Yen Vo||, Carrie E. McCurdy¶, Shoshana Yakar**, Derek LeRoith**, C. Ronald Kahn, Lewis C. Cantley, Jacob E. Friedman¶¶¶1, and Boris Draznin||

From the Departments of Medicine, Obstetrics and Gynecology, ^¶Pediatrics, ^¶¶Biochemistry and Molecular Genetics, University Colorado Health Sciences Center, Denver, Colorado 80262, the ^||Veterans Affairs Research Service, Denver Veterans Affairs Medical Center, Denver, Colorado 80220, the ^**Diabetes Branch, NIDDK, National Institutes of Health, Bethesda, Maryland 20892, the Research Division, Joslin Diabetes Center, Children's Hospital, Harvard Medical School, Boston, Massachusetts 02215, and the Department of Systems Biology, Harvard Medical School, Boston, Massachusetts 02115

Received for publication, June 27, 2005 , and in revised form, August 29, 2005.

	ABSTRACT

TOP ABSTRACT INTRODUCTION EXPERIMENTAL PROCEDURES RESULTS DISCUSSION REFERENCES

 
Insulin resistance is a cardinal feature of normal pregnancy and excess growth hormone (GH) states, but its underlying mechanism remains enigmatic. We previously found a significant increase in the p85 regulatory subunit of phosphatidylinositol kinase (PI 3-kinase) and striking decrease in IRS-1-associated PI 3-kinase activity in the skeletal muscle of transgenic animals overexpressing human placental growth hormone. Herein, using transgenic mice bearing deletions in p85, p85, or insulin-like growth factor-1, we provide novel evidence suggesting that overexpression of p85 is a primary mechanism for skeletal muscle insulin resistance in response to GH. We found that the excess in total p85 was entirely accounted for by an increase in the free p85-specific isoform. In mice with a liver-specific deletion in insulin-like growth factor-1, excess GH caused insulin resistance and an increase in skeletal muscle p85, which was completely reversible using a GH-releasing hormone antagonist. To understand the role of p85 in GH-induced insulin resistance, we used mice bearing deletions of the genes coding for p85 or p85, respectively (p85 ^+/– and p85^–/–). Wild type and p85^–/– mice developed in vivo insulin resistance and demonstrated overexpression of p85 and reduced insulin-stimulated PI 3-kinase activity in skeletal muscle in response to GH. In contrast, p85^+/–mice retained global insulin sensitivity and PI 3-kinase activity associated with reduced p85 expression. These findings demonstrated the importance of increased p85 in mediating skeletal muscle insulin resistance in response to GH and suggested a potential role for reducing p85 as a therapeutic strategy for enhancing insulin sensitivity in skeletal muscle.

	INTRODUCTION

TOP ABSTRACT INTRODUCTION EXPERIMENTAL PROCEDURES RESULTS DISCUSSION REFERENCES

 
Insulin resistance is a common feature associated with growth hormone excess; however, the cellular mechanism underlying insulin resistance remains elusive. We previously demonstrated that transgenic mice overexpressing human placental growth hormone (TG-hPGH),² at levels comparable with the third trimester of pregnancy, were severely insulin-resistant and display increased amounts of the p85 regulatory subunit of phosphatidylinositol 3-kinase (PI 3-kinase) in skeletal muscle (1).

Several recent studies have suggested that a disrupted balance between the levels of the PI 3-kinase subunits may alter insulin-stimulated PI 3-kinase activity (2–6). This enzyme consists of a regulatory subunit, p85, and a catalytic subunit, p110 (7). Normally, the regulatory subunit exists in stoichiometric excess to the catalytic one, resulting in a pool of free p85 monomers not associated with the p110 catalytic subunit. The p85 monomers bind to phosphorylated IRS proteins, blocking access to p85-p110 heterodimers. Thus, there exists a balance between the free p85 monomer and the p85-p110 heterodimer with the latter being responsible for the PI 3-kinase activity. Increases or decreases in expression of p85 shift this balance in favor of either free p85 or p85-p110 complexes (3–6). Because the monomer and the heterodimer compete for the same binding sites on the IRS proteins, an imbalance could cause either increased or decreased PI 3-kinase activity.

In the present study, we found that excess p85 regulatory subunits in TG-hPGH muscle was accounted for by a specific increase in the free p85 isoform. To elucidate whether the increase in p85 was mediated by GH or IGF-1, we selected an insulin-resistant knock-out mouse with a liver-specific deletion of IGF-1 and with compensatory high GH levels (8, 9). Increased skeletal muscle p85 in liver-specific IGF-1 gene deletion (LID) mice was observed and was reversible along with insulin resistance with the administration of a growth hormone-releasing hormone antagonist. Finally, to confirm the role of p85 in the genesis of GH-induced insulin resistance, we took advantage of insulin-sensitive mice with either heterozygous deletions of p85 or a complete knockout of p85 (5, 10, 11) and investigated the effect of GH injections on skeletal muscle p85 levels and IRS-1-associated PI 3-kinase activity. Animals with heterozygous disruption of p85 gene (p85^+/– mice) were unable to increase p85 expression and remained insulin-sensitive, whereas their wild type (WT) and p85^–/– counterparts responded to 3 days of GH administration with increases in p85 expression, reduction in insulin-stimulated IRS-1-associated PI 3-kinase activity and insensitivity to insulin. Together, these findings suggested that increased p85 is a potent negative regulator of insulin signaling in skeletal muscle and insulin resistance in vivo in response to growth hormone.

	EXPERIMENTAL PROCEDURES

TOP ABSTRACT INTRODUCTION EXPERIMENTAL PROCEDURES RESULTS DISCUSSION REFERENCES

 
Animals—TG mice that overexpress human placental growth hormone (TG-hPGH) driven by the metallothionine promoter have been described previously (1, 12). The TG-hPGH mice are extremely insulin-resistant when examined by glucose and insulin challenge tests. Their IGF-1 levels are elevated, but free fatty acids are not increased.

Mice heterozygous for the Pik3r1 allele (p85^+/–) and homozygous Pik3r2 knock-out mice (p85^–/–) have been characterized previously in the laboratories of Drs. Kahn and Cantley (5, 10, 11). All mice were of mixed genetic background consisting of 129S and C57BL/6; therefore, C57BL/6 mice were used as WT controls.

Skeletal muscle from mice with a LID was kindly provided by D. LeRoith, NIDDK, National Institutes of Health, Bethesda, MD and have been described previously (8, 9). These mice show a marked reduction in circulating IGF-1, elevated GH levels, and severe insulin resistance, primarily at the level of skeletal muscle. Treatment with a GH-releasing hormone antagonist, MZ4-71 (GA), for 28 days effectively normalized GH levels and also restored insulin sensitivity (9).

Four to six mice in each group were used in each comparison. All mice were studied at 14–18 weeks and were fed a normal mouse diet ad libitum. The guidelines for the care and treatment of the animals were approved by the Institutional Animal Care and Use Committee at the University of Colorado Health Sciences Center.

Materials—Regular insulin was purchased from Novo Nordisc, Princeton, NJ. Bovine serum albumin and protease inhibitors aprotinin and leupeptin were purchased from Roche Applied Science. Antibodies to IRS-1 and total (pan) p85, and specific to the component of p85 (p85), were purchased from Upstate Biotechnology, Lake Placid, NY. Antibodies to p110 were purchased from Santa Cruz Biotechnology, Inc. (Santa Cruz, CA). Secondary horseradish peroxidase-conjugated antibody, protein A-Sepharose, and chemiluminescence reagents (ECL kit) were obtained from Amersham Biosciences. AG Resins, polyvinylidene difluoride membranes, PAGE gel equipment, and protein assay kits were from Bio-Rad. [-³²P]ATP was obtained from PerkinElmer Life Sciences. Recombinant rat growth hormone (rrGH) was purchased from the National Hormone and Pituitary Program, Harbor-UCLA Medical Center (Los Angeles, CA).

Insulin Tolerance Tests—Insulin tolerance tests were performed in p85^+/–, p85^–/–, and WT mice before and after GH injections (1 mg/kg subcutaneously twice daily for 3 days). Mice were fasted for 6 h and injected intraperitoneally with insulin (0.75 units/kg of body weight). Blood (5 µl) was collected from the tail vein at 0 and 60 min after insulin injection. Glucose measurements were performed with an Acucheck Advantage glucose meter.

Acute Insulin Stimulation in Vivo and Tissue Collection—Mice were fasted for 6 h and anesthetized with ketamine (150 mg/kg) and acepromazine (5 mg/kg), and abdominal cavities were opened, and the inferior vena cava was exposed. Approximately 300 mg of gastrocnemius muscle from one hind limb was rapidly removed and frozen immediately in liquid nitrogen. An insulin bolus of 10 units/kg of body weight was then injected into the inferior vena cava vein as described previously (1). At 5 min after injection, the gastrocnemius muscle from the opposite limb was excised and frozen immediately. The samples were stored at –80 °C until analysis.

Western Blotting of Total p85, p85, and p110—Muscle tissue was homogenized, and protein was assayed as described previously (1). Membranes were blocked with 5% nonfat milk (Bio-Rad,) in TBS-T for 1 h at room temperature. The membrane was washed three times with TBS-T and probed with a polyclonal total p85 antibody (1:500 dilution), monoclonal p85 antibody (1:500 dilution), or polyclonal p110 antibody (1:250 dilution). Transfer and washing conditions were performed as described previously (1). The bands were visualized with enhanced chemiluminescence (ECL) and exposed to Kodak BIOMAX films (Eastman Kodak Co.). The specific bands were quantitated using a GEL-DOC density scanner and Quantity One software (Bio-Rad).

View larger version (16K): [in this window] [in a new window]   FIGURE 1. Increased p85 total versus p85-specific isoform in WT and TG-hPGH mice. Equivalent amounts of protein isolated from the muscle of WT and hPGH mice were subjected to SDS-PAGE gel and blotted with antibodies to pan p85 and p85 specific to the subunit (p85). A representative blot is shown in the upper panel. The values are mean ± S.E. of the scanning densitometry values expressed in arbitrary units; *, p < 0.05; WT versus TG-hPGH mice (n = 4–6 in each group).

IRS-1-associated PI 3-Kinase Activity—The level of IRS-1-associated PI 3-kinase activity was determined in muscle extracts after immunoprecipitation with IRS-1 antibody overnight at 4 °C (400 µg of muscle protein/4 µg of antibody) followed by incubation with protein A-Sepharose overnight, as described previously (1). The lipids were resolved by thin layer chromatography in CHCl₃:MEOH:H₂0:NH₄OH (60:47:11·3: 2), dried, and visualized by autoradiography. The images were quantified using a Kodak Dynamic phosphorimaging device.

Cell Culture Experiments—3T3-L1 preadipocytes were grown to 60% confluence in growth medium (Dulbecco's modified Eagle's medium containing 5% glucose, 10% fetal calf serum, 50 µg/ml gentamicin, and 0.5 mM glutamine). After 24 h incubation with 1% fetal calf serum, cells were exposed to rrGH, either 500 or 2500 ng/ml for an additional 24 h. Cells were lysed, and expression of p85 was determined by Western blotting as described above.

Statistics—Results are expressed as mean ± S.E. and compared using either paired or unpaired t test as indicated. p values of < 0.05 are considered statistically significant.

	RESULTS

TOP ABSTRACT INTRODUCTION EXPERIMENTAL PROCEDURES RESULTS DISCUSSION REFERENCES

 
In our initial experiments, we previously reported increases in the amounts of total p85 expressed in skeletal muscle of transgenic mice overexpressing hPGH (1). Further analyses revealed that the increases in p85 levels were predominantly accounted for by significant increases in p85-specific isoform (p < 0.005; Fig. 1), whereas the levels of p110 were unchanged (data not shown). We confirmed this 2–3-fold increase in the p85 isoform by immunoprecipitating and immunoblotting with a p85-specific antibody (data not shown).

The catalytic p110 subunit was depleted by triple immunoprecipitation from the muscle lysate (4–6), and the levels of p110 and p85 were analyzed by immunoblotting the immunoprecipitate and the supernatant. The amount of p85 recovered in the immunoprecipitate reflects p85 bound to p110, whereas the amount of p85 in the supernatant denotes free p85 subunit, existing in excess of p110.

View larger version (17K): [in this window] [in a new window]   FIGURE 2. Excess free p85 in supernatant unbound to p110 in WT and TG-hPGH mice. The p110 catalytic unit was depleted by triple immunoprecipitation from the muscle lysate, and the levels of p85 were analyzed by Western blot of the immunoprecipitate (IP) and the supernatant (Sn). The amount of p85 recovered in the immunoprecipitate reflects p85 bound to p110, whereas the amount of p85 in the supernatant denotes free p85 subunit, existing in excess of p110. The upper panel depicts a representative blot. The values are mean ± S.E. of the scanning densitometry values and expressed in arbitrary units; *, p < 0.05; WT versus TG-hPGH mice in supernatant (4–6 in each group). IB, immunoblot.

Because TG-hPGH animals have elevated IGF-1 levels (8, 9), which could potentially contribute to the p85 excess, we measured the expression of p85 in a different model of insulin resistance and GH excess. LID mice demonstrate profound insulin resistance, primarily at the level of skeletal muscle (8). These animals display low circulating levels of IGF-1 and compensatory elevations of GH (8, 9). Furthermore, treatment of these animals with a GA for 28 days reduced their levels of GH and completely reversed their insulin resistance (9).

We found that expression of p85 in skeletal muscle of LID mice was significantly higher (p < 0.01) than in WT mice (Fig. 3), suggesting a direct influence of GH. Moreover, treatment of LID mice with GA resulted in normalization of the p85 expression (Fig. 3) concomitant with a reversal of insulin resistance (9).

Lastly, we performed a series of definitive experiments in animals lacking either p85 (heterozygotes p85^+/–) or p85 (homozygotes p85^–/–). These mice were studied before and after twice daily injections of GH for 3 days. Both p85^+/– and p85^–/– mice are more sensitive to insulin than the WT mice, as described previously (2, 5, 10, 11). Here we demonstrated that GH failed to induce insulin resistance in the p85^+/– mice while inducing insulin resistance in the WT and p85^–/– animals. Blood glucose levels were measured following an insulin challenge test before and after GH administration to document the development of insulin resistance, shown in Fig. 4. Although the WT and the p85^–/– mice became resistant to insulin after 3 days of GH injections, as noted by blunted blood glucose responses to insulin at 60 min (p < 0.005 versus pre-GH treatment), the p85^+/– mice remained highly sensitive to insulin.

The levels of p85 in skeletal muscle from the p85^+/– mice were 50% of those in the WT mice (Fig. 5). Although GH administration significantly increased p85 in the WT and p85^–/– animals (p < 0.05 and <0.01, respectively), it had no effect on p85 in the p85^+/– mice. As expected, insulin increased IRS-1-associated PI 3-kinase activity in all animals not exposed to GH (Fig. 6A, p < 0.01). Insulin-stimulated PI 3-kinase activity was somewhat greater in the p85^+/– mice than in two other groups. Moreover, whereas administration of GH blunted insulin-stimulated IRS-1-associated PI 3-kinase activity in the WT and p85^–/– animals, it failed to affect PI 3-kinase activity in the p85^+/– mice. In addition we measured the amount of p110 associated with IRS-1 in p85^+/– and p85^–/– mice versus controls treated with and without GH (Fig. 6B). As expected, we observed a reduced amount of p110 in the IRS-1 immunoprecipitates after GH treatment, confirming that p85 competes with the p85-p110 heterodimer for the IRS-1 binding sites in GH-treated animals. Notably, in p85^+/– mice, the GH effect is absent, mirroring the PI 3-kinase activity results, demonstrating that reducing the p85 levels restores insulin-stimulated p110 association with IRS-1.

View larger version (16K): [in this window] [in a new window]   FIGURE 3. Expression of p85 in skeletal muscle of LID knock-out mice before and after administration of GA for 28 days. Equivalent amounts of protein isolated from the muscle of WT, LID, and LID+GA mice were subjected to SDS-PAGE gel and blotted with PI 3-kinase p85 antibody. Control animals treated with GA were also studied. A representative blot is shown in the upper panel. The values are mean ± S.E. of the scanning densitometry values (n = 4–6) and expressed in arbitrary units; *, p < 0.01; WT versus LID mice and LID+GA versus LID mice (n = 4–6).

	DISCUSSION

TOP ABSTRACT INTRODUCTION EXPERIMENTAL PROCEDURES RESULTS DISCUSSION REFERENCES

 
The seminal finding of this investigation was that GH, whether endogenous or administered exogenously, induces in vivo insulin resistance by increasing the amount of skeletal muscle p85 monomers, unbound to its catalytic p110 subunit. Confirmation of this mechanism was illustrated in this study by critical observations in knock-out mice of opposing insulin sensitivity. Liver-specific IGF-1 knock-out mice, known to be insulin-resistant and to manifest high GH levels (8, 9), demonstrated p85 levels that were approximately twice as high as WT mice. Definitive support for this direct GH effect was achieved by treating these IGF-1-deficient animals with a GH-releasing hormone antagonist for 28 days, which normalized their p85 levels and reversed their insulin resistance (9). Consistent with the hypothesis tested in this study, animals with heterozygous disruption of p85 gene (p85^+/– mice) were unable to increase p85 expression and remained insulin-sensitive, whereas their WT and p85^–/– counterparts responded to GH with increases in p85 expression (Fig. 5), reduction in insulin-stimulated IRS-1-associated PI 3-kinase activity (Fig. 6), and insensitivity to insulin (Fig. 4).

View larger version (10K): [in this window] [in a new window]   FIGURE 4. Insulin tolerance tests in WT, p85+/–, and p85–/– before and after 3 days of administration of GH. Blood was collected from the tail vein at 0 and 60 min after insulin injection. The solid line indicates blood glucose values prior to GH injection; the dotted line indicates blood glucose values after GH injection. The values are mean ± S.E. of 4–6 animals/group expressed as mg/dl; *, p < 0.005 versus pretreatment with GH at 60 min.

View larger version (16K): [in this window] [in a new window]   FIGURE 5. Expression of p85 in WT, p85+/–, and p85–/– mice before and after GH treatment. Equivalent amounts of protein isolated from the muscle of experimental animals were subjected to SDS-PAGE gel and blotted with an antibody to p85. A representative blot is shown in the upper panel. The values are mean ± S.E. of the scanning densitometry values expressed in arbitrary units; *, p < 0.05, and **, p < 0.01 versus pretreatment with GH (n = 4–6 in each group).

View larger version (22K): [in this window] [in a new window]   FIGURE 6. PI 3-kinase activity in WT, p85+/–, p85–/–before and after GH treatment, with and without insulin. A, the level of IRS-1-associated PI 3-kinase activity was determined in muscle extracts as described under "Experimental Procedures." PI3-P, PI 3-phosphate. B, the amount of IRS-1-associated p110 protein was determined in muscle extracts. The values are the mean ± S.E. of the scanning densitometry values expressed in arbitrary units; *, p < 0.01 insulin-stimulated versus control.

View larger version (23K): [in this window] [in a new window]   FIGURE 7. Effect of rrGH on p85 expression in 3T3-L1 preadipocytes. Cells were cultured to 60% confluence and challenged with rrGH, either 500 or 2500 ng/ml for 24 h. Results demonstrate a representative blot and a summary of three experiments. The values are expressed as the mean ± S.E. *, p < 0.01. control versus GH treated (2500 ng/ml).

A string of several publications including the laboratories of Drs. Kahn and Cantley expanded on this observation (2–6, 10, 11). These investigators have generated p85 knock-out mice and p85^+/– heterozygous mice to address this question. Initially, they found that animals with a targeted disruption of p85 are hypersensitive to insulin. They identified that mice with a higher ratio of p85-p110 dimer to free p85 are more insulin-sensitive. To determine this ratio, they immunodepleted p110 and blotted both the immunoprecipitates and the supernatant with p85 antibody. The amounts of p85 in the p110 immunoprecipitates denote p85 bound to p110, whereas the amount of p85 in the supernatant represents free (excess) p85. The greater the ratio of bound to free, the greater insulin sensitivity mice display. Furthermore, Cantley and Kahn (10, 11) have reported that mice with homozygous disruption of both genes encoding p85 (p85^–/–) are also more insulin-sensitive and display an enhanced insulin signaling in skeletal muscle. The p85 null mice were leaner and remained resistant to weight gain while on a high fat diet. Calculations of the expression of various isoforms of p85 revealed that 70–80% of skeletal muscle p85 is represented by p85 with p85 representing the majority of the remaining 20–30%. The same group of authors has then overexpressed p85 in cultured cells. This overexpression significantly inhibited the PI 3-kinase activity (4). Overexpression of p50 or p55 produced a lesser effect. These experiments were in concert with the competition hypothesis.

View larger version (8K): [in this window] [in a new window]   FIGURE 8. Pituitary or human placental GH increases expression of p85 that competes with p85-p110 heterodimer for binding to IRS-1. The inability of the heterodimer to associate with IRS-1 results in a decline in the IRS-1-associated PI 3-kinase activity and insulin resistance.

In summary, the current study fully supported the hypothesis that insulin resistance can be caused by an overabundance of the p85 monomer, which competes with the p85-p110 dimer for binding to IRS-1 and activation of PI 3-kinase. We have also demonstrated that when p85 is underexpressed, as in p85^+/– mice, GH is incapable of causing insulin resistance. Our data identify p85 overexpression as a potent negative regulator of skeletal muscle insulin sensitivity in vivo associated with growth hormone excess (Fig. 8). This mechanism of insulin resistance has direct clinical implications for states of GH excess such as the insulin resistance of normal pregnancy and acromegaly but could have implications for other states of glucose intolerance as well. Thus, p85 remains a potential therapeutic target for the treatment of insulin resistance and a possible factor underlying susceptibility to Type 2 Diabetes.

	FOOTNOTES

 
^* This work was supported by a grant from the Veterans Administration Research Service and by the National Institutes of Health Grants DK062155 (to J. E. F.) and GM41890 (to L. C. C.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

¹ To whom correspondence should be addressed: University of Colorado Health Sciences Center, Mail Stop 8106, P. O. Box 6511, Aurora, CO 80045. Tel.: 303-724-3983; Fax: 303-724-3920; E-mail: Jed.Friedman{at}uchsc.edu.

² The abbreviations used are: TG, transgenic; GH, growth hormone; rrGH, recombinant rat GH; hPGH, human placental growth hormone; IGF, insulin-like growth factor; PI, phosphatidylinositol; LID, liver-specific IGF-1 gene deletion; IRS, insulin receptor substrate; GA, GH-releasing hormone antagonist; WT, wild type.

³ J. E. Friedman, unpublished data.

	REFERENCES

TOP ABSTRACT INTRODUCTION EXPERIMENTAL PROCEDURES RESULTS DISCUSSION REFERENCES

 

1. Barbour, L. A., Shao, J., Qiao, L., Leitner, W., Anderson, M., Friedman, J. E., and Draznin, B. (2004) Endocrinology 145, 1144–1150[Abstract/Free Full Text]
2. Ueki, K., Fruman, D. A., Brachmann, S. M., Tseng, Y. H., Cantley, L. C., and Kahn, C. R. (2002) Mol. Cell. Biol. 22, 965–977[Abstract/Free Full Text]
3. Terauchi, Y., Tsuji, Y., Satoh, S., Minoura, H., Murakami, K., Okuno, A., Inukai, K., Asano, T., Kaburagi, Y., Ueki, K., Nakajima, H., Hanafusa, T., Matsuzawa, Y., Sekihara, H., Yin, Y., Barrett, J. C., Oda, H., Ishikawa, T., Akanuma, Y., Komuro, I., Suzuki, M., Yamamura, K.-I., Kodama, T., Suzuki, H., Koyasu, S., Aizawa, S., Tobe, K., Fukui, Y., Yazaki, Y., and Kadowaki, T. (1999) Nat. Genet. 21, 230–235[CrossRef][Medline] [Order article via Infotrieve]
4. Ueki, K., Algenstaedt, P., Mauvais-Jarvis, F., and Kahn C. R. (2000) Mol. Cell. Biol. 20, 8035–8046[Abstract/Free Full Text]
5. Mauvais-Jarvis, F., Ueki, K., Fruman, D. A., Hirshman, M. F., Sakamoto, K., Goodyear, L. J., Iannacone, M., Accili, D., Cantley, L. C., and Kahn C. R. (2002) J. Clin. Investig. 109, 141–149[CrossRef][Medline] [Order article via Infotrieve]
6. Ueki, K., Fruman, D. A., Uballe, C. M., Fasshauer, M., Klein, J., Asano, T., Cantley L. C., and Kahn, C. R. (2003) J. Biol. Chem. 278, 48453–48466[Abstract/Free Full Text]
7. Shepherd, P. R., Withers, D. J., and Siddle, K. (1998) Biochem. J. 333, 471–490[Medline] [Order article via Infotrieve]
8. Yakar, S., Liu, J.-L., Fernandez, A. M., Wu, Y., Schally, A. V., Frystyk, J., Chernausek, S. D., Mejia, W., and LeRoith, D. (2001) Diabetes 50, 1110–1118[Abstract/Free Full Text]
9. Yakar, S., Setser, J., Zhao, H., Stannard, B., Haluzik, M., Glatt, V., Bouxsein, M. L., Kopchick, J. J., and LeRoith, D. (2004) J. Clin. Investig. 113, 96–105[CrossRef][Medline] [Order article via Infotrieve]
10. Ueki, K., Yballe, C. M., Brachmann, S. M., Vicent, D., Watt, J. M., Kahn, C. R., and Cantley, L. C. (2002) Proc. Natl. Acad. Sci. U. S. A. 99, 419–424[Abstract/Free Full Text]
11. Lamia, K. A., Peroni, O. D., Kim, Y.-B., Rameh, L. E., Kahn, B. B., and Cantley, L. C. (2004) Mol. Cell. Biol. 24, 5080–5087[Abstract/Free Full Text]
12. Barbour, L. A., Shao, J., Qiao, L., Pulawa, L. K., Jensen, D. R., Bartke, A. B., Garrity, M., Draznin, B., and Friedman, J. E. (2002) Am. J. Obstet. Gynecol. 186, 512–517[CrossRef][Medline] [Order article via Infotrieve]
13. Bak, J. F., Møller, N., and Schmitz, O. (1991) Am. J. Physiol. 260, E736–E742[Medline] [Order article via Infotrieve]
14. Kim, J. K., Choi, C. S., and Youn, J. H. (1999) Am. J. Physiol. 277, E742–E749[Medline] [Order article via Infotrieve]
15. Thirone, A. C. P., Paez-Espinosa, E. V., Carvalho, C. R. O., and Saad, M. J. A. (1998) FEBS Lett. 421, 191–196[CrossRef][Medline] [Order article via Infotrieve]
16. Dominici, F. P., Cifone, D., Bartke, A., and Turyn, D. (1999) Am. J. Physiol. 277, E447–E454[Medline] [Order article via Infotrieve]
17. Thirone, A. C. P., Carvalho, C. R. O., Brenelli, S. L., Velloso, L. A., and Saad, M. J. A. (1997) Mol. Cell. Endocrinol. 130, 33–42[CrossRef][Medline] [Order article via Infotrieve]
18. Smith, T. R., Elmendorf, R. S., David, T. S., and Turinsky, J. (1997) Am. J. Physiol. 272, E1071–E1079[Medline] [Order article via Infotrieve]
19. Dhand, R., Hara, K., Hiles, I., Box, B., Gout, I., Panayatou, G., Fry, M. J., Yonezawa, K., Kasuga, M., and Waterfield, M. D. (1994) EMBO J. 13, 511–521[Medline] [Order article via Infotrieve]
20. Gout, I., Dhand, R., Panayatou, G., Fry, M. J., Hiles, I., Otsu, M., and Waterfiled, M. D. (1992) Biochem. J. 288, 395–405[Medline] [Order article via Infotrieve]
21. Hu, P., Mondino, A., Skolnik, E. Y., and Schlessinger, J. (1993) Mol. Cell. Biol. 13, 7677–7688[Abstract/Free Full Text]
22. Giorgino, F., Pedrini, M. T., Matera, L., and Smith, R. J. (1997) J. Biol. Chem. 272, 7455–7463[Abstract/Free Full Text]
23. Friedman, J. E., Ishizuka, T., Shao, J., Huston, L., Highman, T., and Catalano, P. (1999) Diabetes 48, 1807–1814[Abstract]
24. Kirwan, J., Varastehpour, A., Jing, M., Presley, L., Shao, J., Friedman, J. E., and Catalano, P. M. (2004) J. Clin. Endocrinol. Metab. 89, 4678–4684[Abstract/Free Full Text]
25. Barbour, L. A., Hernandez, T. L., Fischer, S., Leitner, J. W., Knotts, T., Rahman, M., Kirk, S., Cantley, L., Kahn, C. R., Draznin, B., and Friedman, J. E. (2005) in American Diabetes Association 65^th Scientific Sessions, San Diego, CA, Diabetes 54, Suppl. 1, A39 (abstr.)
26. Del Rincon, J. P., Iida, K., Gaylinn, B. D., and Thorner, M. O. (2005) The Endocrine Society 87^th Annual Meeting, San Diego, CA (abstr.)

CiteULike

Complore

Connotea

Del.icio.us

Digg

Reddit

Technorati

This article has been cited by other articles:

				S. R. Thorn, T. R. H. Regnault, L. D. Brown, P. J. Rozance, J. Keng, M. Roper, R. B. Wilkening, W. W. Hay Jr., and J. E. Friedman Intrauterine Growth Restriction Increases Fetal Hepatic Gluconeogenic Capacity and Reduces Messenger Ribonucleic Acid Translation Initiation and Nutrient Sensing in Fetal Liver and Skeletal Muscle Endocrinology, July 1, 2009; 150(7): 3021 - 3030. [Abstract] [Full Text] [PDF]

				T. de Castro Barbosa, J. E. Nicoletti de Carvalho, L. Lourenco Poyares, S. Bordin, U. Fabres Machado, and M. T. Nunes Potential Role of Growth Hormone in Impairment of Insulin Signaling in Skeletal Muscle, Adipose Tissue, and Liver of Rats Chronically Treated with Arginine Endocrinology, May 1, 2009; 150(5): 2080 - 2086. [Abstract] [Full Text] [PDF]

				M. Colomiere, M. Permezel, C. Riley, G. Desoye, and M. Lappas Defective insulin signaling in placenta from pregnancies complicated by gestational diabetes mellitus Eur. J. Endocrinol., April 1, 2009; 160(4): 567 - 578. [Abstract] [Full Text] [PDF]

				R. Adochio, J. W. Leitner, R. Hedlund, and B. Draznin Rescuing 3T3-L1 Adipocytes from Insulin Resistance Induced by Stimulation of Akt-Mammalian Target of Rapamycin/p70 S6 Kinase (S6K1) Pathway and Serine Phosphorylation of Insulin Receptor Substrate-1: Effect of Reduced Expression of p85{alpha} Subunit of Phosphatidylinositol 3-Kinase and S6K1 Kinase Endocrinology, March 1, 2009; 150(3): 1165 - 1173. [Abstract] [Full Text] [PDF]

				F. Kuhnert, M. R. Mancuso, J. Hampton, K. Stankunas, T. Asano, C.-Z. Chen, and C. J. Kuo Attribution of vascular phenotypes of the murine Egfl7 locus to the microRNA miR-126 Development, December 15, 2008; 135(24): 3989 - 3993. [Abstract] [Full Text] [PDF]

				J. E. Friedman, J. P. Kirwan, M. Jing, L. Presley, and P. M. Catalano Increased Skeletal Muscle Tumor Necrosis Factor-{alpha} and Impaired Insulin Signaling Persist in Obese Women With Gestational Diabetes Mellitus 1 Year Postpartum Diabetes, March 1, 2008; 57(3): 606 - 613. [Abstract] [Full Text] [PDF]

				R P Rhoads, J W Kim, M E Van Amburgh, R A Ehrhardt, S J Frank, and Y R Boisclair Effect of nutrition on the GH responsiveness of liver and adipose tissue in dairy cows J. Endocrinol., October 1, 2007; 195(1): 49 - 58. [Abstract] [Full Text] [PDF]

				D. R. Clemmons, M. Sleevi, G. Allan, and A. Sommer Effects of Combined Recombinant Insulin-Like Growth Factor (IGF)-I and IGF Binding Protein-3 in Type 2 Diabetic Patients on Glycemic Control and Distribution of IGF-I and IGF-II among Serum Binding Protein Complexes J. Clin. Endocrinol. Metab., July 1, 2007; 92(7): 2652 - 2658. [Abstract] [Full Text] [PDF]

				L. A. Barbour, C. E. McCurdy, T. L. Hernandez, J. P. Kirwan, P. M. Catalano, and J. E. Friedman Cellular Mechanisms for Insulin Resistance in Normal Pregnancy and Gestational Diabetes Diabetes Care, July 1, 2007; 30(Supplement_2): S112 - S119. [Full Text] [PDF]

				Z. Wang, M. M. Masternak, K. A. Al-Regaiey, and A. Bartke Adipocytokines and the Regulation of Lipid Metabolism in Growth Hormone Transgenic and Calorie-Restricted Mice Endocrinology, June 1, 2007; 148(6): 2845 - 2853. [Abstract] [Full Text] [PDF]

				J.-P. del Rincon, K. Iida, B. D. Gaylinn, C. E. McCurdy, J. W. Leitner, L. A. Barbour, J. J. Kopchick, J. E. Friedman, B. Draznin, and M. O. Thorner Growth Hormone Regulation of p85{alpha} Expression and Phosphoinositide 3-Kinase Activity in Adipose Tissue: Mechanism for Growth Hormone-Mediated Insulin Resistance Diabetes, June 1, 2007; 56(6): 1638 - 1646. [Abstract] [Full Text] [PDF]

				X. Wang, J. Hu, and S. R. Price Inhibition of PI3-kinase signaling by glucocorticoids results in increased branched-chain amino acid degradation in renal epithelial cells Am J Physiol Cell Physiol, May 1, 2007; 292(5): C1874 - C1879. [Abstract] [Full Text] [PDF]

				B. Draznin Molecular Mechanisms of Insulin Resistance: Serine Phosphorylation of Insulin Receptor Substrate-1 and Increased Expression of p85{alpha}: The Two Sides of a Coin. Diabetes, August 1, 2006; 55(8): 2392 - 2397. [Abstract] [Full Text] [PDF]

This Article Abstract Full Text (PDF) All Versions of this Article: 280/45/37489    most recent M506967200v2 M506967200v1 Submit a Letter to Editor Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map 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 Barbour, L. A. Articles by Draznin, B. Search for Related Content PubMed PubMed Citation Articles by Barbour, L. A. Articles by Draznin, B. Social Bookmarking                      What's this?