Kegg Pathway: Insulin signaling pathway

PLoS Biol. 2009 Nov; 7(11): e1000245
Zhang M, Poplawski M, Yen K, Cheng H, Bloss E, Zhu X, Patel H, Mobbs CV

How dietary restriction (DR) increases lifespan and decreases disease burden are questions of major interest in biomedical research. Here we report that hypothalamic expression of CREB-binding protein (CBP) and CBP-binding partner Special AT-rich sequence binding protein 1 (SATB-1) is highly correlated with lifespan across five strains of mice, and expression of these genes decreases with age and diabetes in mice. Furthermore, in Caenorhabditis elegans, cbp-1 is induced by bacterial dilution DR (bDR) and the daf-2 mutation, and cbp-1 RNAi specifically in adults completely blocks lifespan extension by three distinct protocols of DR, partially blocks lifespan extension by the daf-2 mutation but not of cold, and blocks delay of other age-related pathologies by bDR. Inhibiting the C. elegans ortholog of SATB-1 and CBP-binding partners daf-16 and hsf-1 also attenuates lifespan extension by bDR, but not other protocols of DR. In a transgenic Abeta42 model of Alzheimer's disease, cbp-1 RNAi prevents protective effects of bDR and accelerates Abeta42-related pathology. Furthermore, consistent with the function of CBP as a histone acetyltransferase, drugs that enhance histone acetylation increase lifespan and reduce Abeta42-related pathology, protective effects completely blocked by cbp-1 RNAi. Other factors implicated in lifespan extension are also CBP-binding partners, suggesting that CBP constitutes a common factor in the modulation of lifespan and disease burden by DR and the Insulin/IGF1 signaling pathway.

Pancreas. 2009 Nov 16;
Hui H, Tang YG, Zhu L, Khoury N, Hui Z, Wang KY, Perfetti R, Go VL

OBJECTIVES:: That glucagonlike peptide-1 (GLP-1) induces differentiation of primate embryonic stem (ES) cells into Insulin-producing cells has been reported by several groups and also confirmed with our observations. METHODS:: To further elucidate the process in detail and the signaling pathways involved in this differentiation, we induced human ES cells HUES1 differentiated into Insulin secretion cells by GLP-1 treatment. RESULTS:: A time-dependent pattern of down expression of the stem cell markers (human telomerase reverse transcriptase and octamer-4), and the appearance of multiple beta-cell-specific proteins (Insulin, glucokinase, glucose transporter, type 2, and islet duodenal homeobox 1) and hedgehog signal molecules (Indian hedgehog, sonic hedgehog, and hedgehog receptor, patched) have been identified. Cotreatment with hedgehog signal inhibitor cytopamine was able to block this differentiation, providing evidence of the involvement of the hedgehog signaling pathway in GLP-1-induced differentiation. We also observed increased transcripts of the transcription factors of activator protein 1, serum response element-1, DNA-binding transcription factors, and cAMP response element in GLP-1-induced ES cell differentiation. Inhibition profile by its specific inhibitors indicated that the cyclic adenosine monophosphate and phosphatidylinositol-3-kinase pathways, but not the mitogen-activated protein kinase pathway, were required for the induced differentiation of ES cells. CONCLUSIONS:: These data support that GLP-1 directs human ES cell differentiation into Insulin-producing cells via hedgehog, cyclic adenosine monophosphate, and phosphatidylinositol-3-kinase pathways.

J Biol Chem. 2009 Nov 18;
Alper S, McElwee MK, Apfeld J, Lackford B, Freedman JH, Schwartz DA

The relationship between the mechanisms that control an organism's lifespan and its ability to respond to environmental challenges are poorly understood. In C. elegans, an Insulin-like signaling pathway modulates lifespan and the innate immune response to bacterial pathogens, via a common mechanism involving transcriptional regulation by the DAF-16/FOXO transcription factor. The C. elegans germline also modulates lifespan in a daf-16-dependent manner. Here we show that the germline controls the innate immune response of C. elegans somatic cells to two different Gram negative bacteria. In contrast to the Insulin-like signaling pathway, the germline acts via distinct signaling pathways to control lifespan and innate immunity. Under standard nematode culture conditions, the germline regulates innate immunity in parallel to a known p38 MAPK signaling pathway, via a daf-16-independent pathway. Our findings indicate that a complex regulatory network integrates inputs from Insulin-like signaling, p38 MAPK signaling, and germline stem cells to control innate immunity in C. elegans. We also confirm that innate immunity and lifespan in C. elegans are distinct processes, as non-overlapping regulatory networks control survival in the presence of pathogenic and non-pathogenic bacteria. Finally, we demonstrate that the p38 MAPK pathway in C. elegans is activated to a similar extent by both pathogenic and non-pathogenic bacteria, suggesting that both can induce the nematode innate immune response.

Cancer Chemother Pharmacol. 2009 Nov 18;
Choi YJ, Rho JK, Jeon BS, Choi SJ, Park SC, Lee SS, Kim HR, Kim CH, Lee JC

PURPOSE: H1650 non-small cell lung cancer (NSCLC) cells display primary resistance to epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs) although they have a deletion mutation on exon 19 of the EGFR gene. We investigated the effect of inhibition of both Insulin-like growth factor receptor (IGFR) and EGFR signaling considering that IGFR signaling pathway has been implicated in the development and progression with therapeutic resistance of various cancers including lung cancer. METHODS: Three human NSCLC cell lines with an EGFR mutation of PC-9, HCC827 and H1650 were used for experiment. Cell viability and proliferative activity were assessed by MTT and three-dimensional culture assay. Combination index was obtained by CalcuSyn software. The change of EGFR- and IGFR-related signals was evaluated by western blots. RESULTS: H1650 cells were 1,000 times more resistant to gefitinib and erlotinib than HCC827 and PC-9 cells possessing the same EGFR mutation. Phosphatase and tensin homolog loss and sustained phosphorylation of Akt in spite of treatment with gefitinib were evident only in H1650 cells. Interestingly, IGFR phosphorylation was decreased by gefitinib in HCC827 and PC-9 cells while being maintained in H1650 cells. Combined treatment with the IGFR inhibitors alpha-IR3 and AG1024 enhanced gefitinib-induced growth inhibition and apoptosis, and down-regulated phosphorylation of Akt, EGFR and IGFR. CONCLUSION: Combined inhibition of IGFR signaling enhances the growth inhibitory and apoptosis-inducing effects of gefitinib, suggesting that this approach could be useful to overcome the primary resistance to EGFR-TKIs in lung cancer.

J Endocrinol Invest. 2009 Nov 12;
Zhang X, Ke L, Yu Y

Aims: To evaluate the effects of elevated circulating free fatty acids(FFAs) concentration on basal and glucose stimulate Insulin secretion (GSIS) of pancreatic beta-cell in vivo and in vitro, and to explore the pathophysiologic links between FFAs and impaired beta cell dysfunction. Methods: Male S-D rats were assigned to three groups and underwent 4 days infusions with normal saline(NC), 20% Intralipid plus heparin (FFA) or Intralipid plus heparin and N-acetylcysteine (FFANAC). The plasma Insulin, malonyldialdehyde(MDA) reduced glutathione (GSH), oxidized glutathione (GSSG) were measured. The ability of Insulin secretion was evaluated by intravenous glucose tolerance test (IVGTT) in vivo and isolated pancreas perfusion test in vitro. The expression of Insulin and key factors of oxidative stress- activated signaling pathways in pancreatic islets were tested by immunohistochemistry. Results: GSIS was decreased in FFA group compared with saline group in IVGTT, and the response to 16.7 mM glucose in isolated perfused pancreas were 214.7 +/- 29.5 mIU/L (NS), 46.8 +/- 33.0 mIU/L (FFA), and 165.4 +/- 14.8 mIU/L(FFA+NAC) respectively(P<0.05). The GSH/GSSG were 88.7+/-3.1 (NS), 40.4+/-14.3 (FFA), and 70.8+/-5.4(FFA+NAC), while MDA level were 3.11+/-0.48 nmol/L(NS), 5.05+/-1.08 nmol/L (FFA), and 3.60+/-0.66 nmol/L (FFA+NAC) respectively. The pancreatic tissues immunohistochemistry test showed that Insulin expressions were decreased in FFA group while NF-kappaB and iNOS expressions in islets were markedly increased compared to NS group (P<0.001 and P<0.01), but those were significantly improved in FFANAC group(P<0.05). Conclusion: Elevated circulating FFAs levels may contribute to causing the abnormalities of pancreatic islet cell function through active oxidative stress and oxidative stress-sensitive signaling pathway (IkappaB-NF-kappaB-iNOS signaling pathway). Antioxidant N-acetylcysteine may partly mitigate impaired beta-cell function produced by elevated FFA concentration.

Physiol Behav. 2009 Nov 12;
Bandaru SS, Lin K, Roming SL, Vellipuram R, Harney JP

Alterations in two components of the brain's Insulin signaling pathway, docosahexaenoic acid (DHA) content and phosphoinositide 3-kinase (PI3K) activity, have been implicated in the Insulin resistance that is central to type II diabetes mellitus (DM). A 2- to 3-fold increased risk of developing Alzheimer's disease (AD) in patients with type II DM suggests a potential link between cognition and Insulin action. The current study was designed to examine the impact of DHA dietary content and PI3K activity on learning, memory, depression, and anxiety in rodents. Mice were divided into the following groups: (1) control diet and vehicle injection (control PI3K), (2) control diet and wortmannin injection (PI3K inhibition), (3) low DHA diet and vehicle, and (4) low DHA diet and wortmannin. Each group was assessed for effects on activity, cognition, depression, and anxiety. Concentrations of glucose and Insulin in plasma were quantified to confirm Insulin resistance. Results showed significant increases in depression, anxiety, plasma Insulin and glucose, and significant decreases in activity in wortmannin-treated mice regardless of diet. The control diet/wortmannin-treated group showed a significant decrease in memory compared to all other groups. The low DHA diet/wortmannin-treated group had slightly improved memory and lower levels of depression compared to the control diet/wortmannin-treated group. Results of the present study suggest that inhibition of PI3K decreases activity and memory while increasing Insulin resistance, depression, and anxiety. In addition, these results suggest a possible compensatory role of low DHA in decreasing the effects of dysfunctional PI3K in AD associated cognitive decline and depression.

Metabolism. 2009 Nov 13;
Elam MB, Yellaturu C, Howell GE, Deng X, Cowan GS, Kumar P, Park EA, Hiler ML, Wilcox HG, Hughes TA, Cook GA, Raghow R

We compared hepatic expression of genes that regulate lipid biosynthesis and metabolic signaling in liver biopsy specimens from women who were undergoing gastric bypass surgery (GBP) for morbid obesity with that in women undergoing ventral hernia repair who had experienced massive weight loss (MWL) after prior GBP. Comprehensive metabolic profiles of morbidly obese (MO) (22 subjects) and MWL (9 subjects) were also compared. Analyses of gene expression in liver biopsies from MO and MWL were accomplished by Affymetrix microarray, real-time polymerase chain reaction, and Western blotting techniques. After GBP, MWL subjects had lost on average 102 lb as compared with MO subjects. This was accompanied by effective reversal of the dyslipidemia and Insulin resistance that were present in MO. As compared with MWL, livers of MO subjects exhibited increased expression of sterol regulatory element binding protein (SREBP)-1c and its downstream lipogenic targets, fatty acid synthase and acetyl-coenzyme A-carboxylase-1. Livers of MO subjects also exhibited enhanced expression of suppressor of cytokine signaling-3 protein and attenuated Janus kinase signal transducer and activator of transcription (JAK/STAT) signaling. Consistent with these findings, we found that the human SREBP-1c promoter was positively regulated by Insulin and negatively regulated by STAT3. These data support the hypothesis that suppressor of cytokine signaling-3-mediated attenuation of the STAT signaling pathway and resulting enhanced expression of SREBP-1c, a key regulator of de novo lipid biosynthesis, are mechanistically related to the development of hepatic Insulin resistance and dyslipidemia in MO women.

Clin Chim Acta. 2009 Nov 10;
Banudevi S, Senthilkumar K, Sharmila G, Arunkumar R, Vijayababu R, Arunakaran J

BACKGROUND: Prostate cancer is one of the most frequently diagnosed cancers in men. Progression of these tumors is facilitated by growth factors that activate critical signaling cascades thereby promote prostate cancer cell growth, survival, and migration. Among these, Insulin-like growth factors (IGFs) signaling pathway contributes a major role. In this study, we examined the effect of zinc on Insulin-like growth factors signaling in prostate cancer cells. METHODS: Human androgen-independent prostatic carcinoma (PC-3) cells were treated with different concentrations of zinc (20-100micromol/l) for 24 and 48h. Cell viability was performed by 3 [4, 5-dimethylthiazol-2-yl]-2, 5-diphenyltetrazolium bromide (MTT) assay. Insulin-like growth factor binding protein-3 (IGFBP-3), Insulin-like growth factor - I receptor (IGF-IR), Insulin receptor substrates -1 (IRS-1) and IRS-2, phosphatidylinositol-3 kinase (PI-3K), protein kinase B or Akt, phosphorylated Akt (p-Akt), extracellular regulated kinase 1/2 (ERK1/2), phosphorylated ERK1/2 (p- ERK1/2), and cyclin D1 protein levels were assessed by western blot analysis. Apoptosis was confirmed by 4', 6'-diaminido-2- phenylindole dihydrochloride (DAPI) staining, and mitochondrial membrane potential was performed using rhodamine-123 staining method. RESULTS: Zinc significantly reduces the cell viability of PC-3 cells. It decreases the protein levels of IGF-IR, IRS-1, IRS-2 and increases the level of IGFBP-3. Zinc reduces the levels of PI-3K, Akt, ERK1/2, and cyclin Dl. Loss of mitochondrial membrane potential and apoptotic cell death were also observed in zinc-treated cells. CONCLUSION: This study suggests that zinc decreases the survival of androgen-independent prostate cancer cells by modulating the expression of IGF system components and its signaling molecules. Thus, zinc may be qualified as a potential agent for the treatment of prostate cancer.

J Cell Sci. 2009 Nov 15; 122(Pt 22): 4160-7
Kim WK, Jung H, Kim DH, Kim EY, Chung JW, Cho YS, Park SG, Park BC, Ko Y, Bae KH, Lee SC

Mesenchymal stem cells (MSCs) are multipotent adult stem cells that can differentiate into a variety of mesodermal-lineage cells. MSCs have significant potential in tissue engineering and therapeutic applications; however, the low differentiation and proliferation efficiencies of these cells in the laboratory are fundamental obstacles to their therapeutic use, mainly owing to the lack of information on the detailed signal-transduction mechanisms of differentiation into distinct lineages. With the aid of protein-tyrosine-phosphatase profiling studies, we show that the expression of leukocyte common antigen related (LAR) tyrosine phosphatase is significantly decreased during the early adipogenic stages of MSCs. Knockdown of endogenous LAR induced a dramatic increase in adipogenic differentiation, whereas its overexpression led to decreased adipogenic differentiation in both 3T3-L1 preadipocytes and MSCs. LAR reduces tyrosine phosphorylation of the Insulin receptor, in turn leading to decreased phosphorylation of the adaptor protein IRS-1 and its downstream molecule Akt (also known as PKB). We propose that LAR functions as a negative regulator of adipogenesis. Furthermore, our data support the possibility that LAR controls the balance between osteoblast and adipocyte differentiation. Overall, our findings contribute to the clarification of the mechanisms underlying LAR activity in the differentiation of MSCs and suggest that LAR is a candidate target protein for the control of stem-cell differentiation.

J Hepatol. 2009 Oct 28;
Huynh H, Ngo VC, Koong HN, Poon D, Choo SP, Toh HC, Thng CH, Chow P, Ong HS, Chung A, Goh BC, Smith PD, Soo KC

BACKGROUND & AIMS: Hepatocellular carcinoma (HCC) is a particularly vascularized solid tumor where the Raf/MEK/ERK pathway is activated; suggesting that inhibition of this pathway may have therapeutic potential. METHODS: We treated patient-derived HCC xenografts with (i) sorafenib, (ii) AZD6244 (ARRY-142886), and (iii) sorafenib plus AZD6244. Western blotting was employed to determine pharmacodynamic changes in biomarkers relevant to both angiogenesis and MEK signaling. Apoptosis, microvessel density, and cell proliferation were analyzed by immunohistochemistry. RESULTS: We report here that sorafenib treatment resulted in suppression of tumor growth, reduction in cell proliferation, induction of apoptosis and inhibition of mTOR targets. Sorafenib-induced elevation of the Insulin-like growth factor receptor 1 (IGF-1R), phospho-c-Raf Ser338, phospho-MEK Ser217/221 and phospho-ERK Thr202/Tyr204 was attenuated by co-treating cells with anti-human IGF-1R antibody or over-expression of activated mutant p70S6K. Pharmacological inhibition of the MEK/ERK pathway by AZD6244 enhanced the anti-tumor effect of sorafenib in both orthotopic and ectopic models of HCC. Such inhibition led to a further increase in pro-apoptotic Bim, apoptosis and a profound inhibition of cell proliferation. CONCLUSION: Our findings underscore the potential of a combined therapeutic approach with sorafenib and MEK inhibitors in the treatment of HCC.

J Gerontol A Biol Sci Med Sci. 2009 Nov 11;
Masternak MM, Panici JA, Wang F, Wang Z, Spong A

The disruption of the growth hormone (GH) axis in mice promotes Insulin sensitivity and is strongly correlated with extended longevity. Ames dwarf (Prop1(df), df/df) mice are GH, prolactin (PRL), and thyrotropin (TSH) deficient and live approximately 50% longer than their normal siblings. To investigate the effects of GH on Insulin and GH signaling pathways, we subjected these dwarf mice to twice-daily GH injections (6 mug/g/d) starting at the age of 2 weeks and continuing for 6 weeks. This produced the expected activation of the GH signaling pathway and stimulated somatic growth of the Ames dwarf mice. However, concomitantly with increased growth and increased production of Insulinlike growth factor-1, the GH treatment strongly inhibited the Insulin signaling pathway by decreasing Insulin sensitivity of the dwarf mice. This suggests that improving growth of these animals may negatively affect both their healthspan and longevity by causing Insulin resistance.

J Gastroenterol. 2009 Nov 10;
Wang Y, Adachi Y, Imsumran A, Yamamoto H, Piao W, Li H, Ii M, Arimura Y, Park MY, Kim D, Lee CT, Carbone DP, Imai K, Shinomura Y

BACKGROUND AND AIMS: Insulin-like growth factor (IGF)-I receptor (IGF-IR) signaling plays important parts in both the tumorigenicity and progression of digestive/gastrointestinal malignancies. In this study, we sought to test the effectiveness of a practical approach to blocking IGF-IR signaling using RNA interference delivered by recombinant adenoviruses. METHODS: We constructed a recombinant adenovirus expressing short hairpin RNA targeting IGF-IR (shIGF-IR) and assessed its effect on signal transduction, proliferation, and survival in digestive/gastrointestinal cancer cell lines representing colorectal, gastric, and pancreatic adenocarcinoma, esophageal squamous cell carcinoma, and hepatoma. We analyzed the effects of shIGF-IR alone and with chemotherapy in vitro and in nude mouse xenografts, as well as on Insulin signaling and hybrid receptor formation between IGF-IR and Insulin receptor. RESULTS: shIGF-IR blocked expression and autophosphorylation of IGF-IR and downstream signaling by the IGFs, but not by Insulin. shIGF-IR suppressed proliferation and carcinogenicity in vitro and up-regulated apoptosis in a dose-dependent fashion. shIGF-IR augmented the effects of chemotherapy on in vitro growth and apoptosis induction. Moreover, the combination of shIGF-IR and chemotherapy was highly effective against tumors in mice. shIGF-IR reduced hybrid receptor formation without effect on expression of Insulin receptor. CONCLUSIONS: shIGF-IR may have therapeutic utility in human digestive/gastrointestinal cancers, both alone and in combination with chemotherapy.

J Hypertens. 2009 Dec; 27(12): 2409-2420
Muñoz MC, Giani JF, Dominici FP, Turyn D, Toblli JE

BACKGROUND: Angiotensin II (Ang II) has been shown to contribute to the pathogenesis of hypertension and Insulin resistance. In addition, administration of selective Ang II type-1 receptor blockers has been shown to improve Insulin sensitivity. However, only a few studies have addressed the molecular mechanisms involved in this association. OBJECTIVE AND DESIGN: The current study was undertaken to determine whether an Ang II receptor blocker (irbesartan) is effective in improving Insulin resistance in adipose tissue from obese Zucker rats, a model of metabolic syndrome. METHODS: Ten-week-old male obese Zucker rats (fa/fa) were treated daily with either vehicle or 50 mg/kg irbesartan for 6 months, and their age-matched lean (+/?) (lean Zucker rats) was used as a control. We determined systolic blood pressure (SBP), together with plasma levels of Insulin, triglycerides, cholesterol and glucose. In addition, we evaluated Insulin signaling through the Insulin receptor/Insulin receptor substrate-1/phosphatidylinositol 3 kinase/Akt/glucose transporter 4 pathway as well as the inflammatory status of adipose tissue. RESULTS: Obese Zucker rats displayed hyperglycemia, hypertriglyceridemia, hyperInsulinemia and hypercholesterolemia and increased SBP together with decreased activation of Insulin signaling through the Insulin receptor/Insulin receptor substrate-1/phosphatidylinositol 3 kinase/Akt pathway in adipose tissue as well as increased adipocytes size, macrophage infiltration and augmented levels of inflammatory mediators such tumor necrosis factor-alpha, monocyte chemoattractant protein-1 and Ang II. Chronic irbesartan treatment resulted in an improvement of all alterations. CONCLUSION: The present study provides substantial information that demonstrates that long-term selective Ang II blockade ameliorates Insulin resistance in adipose tissue from a model of metabolic syndrome via a mechanism that could involve the modulation of Insulin signaling.

Cell Cycle. 2009 Dec 14; 8(23):
Narasimhan SD, Mukhopadhyay A, Tissenbaum HA

Signal transduction pathways are tightly regulated by phosphorylation-dephosphorylation cycles and yet the mammalian genome contains far more genes that encode for protein kinases than protein phosphatases. Therefore, to target specific substrates, many phosphatases associate with distinct regulatory subunits and thereby modulate multiple cellular processes. One such example is the C. elegans PP2A regulatory subunit PPTR-1 that negatively regulates the Insulin/Insulin-like growth factor signaling pathway to modulate longevity, dauer diapause, fat metabolism and stress resistance. PPTR-1, as well as its mammalian homolog B56beta, specifically target the PP2A enzyme to AKT and mediate the dephosphorylation of this important kinase at a conserved threonine residue. In C. elegans, the major consequence of this modulation is activation of the FOXO transcription factor homolog DAF-16, which in turn regulates transcription of its many target genes involved in longevity and stress resistance. Understanding the function of B56 subunits may have important consequences in diseases such as Type 2 diabetes and cancer where the balance of Akt phosphorylation is deregulated.

Target Oncol. 2009 Nov 7;
Capdevila J, Salazar R

Gastroenteropancreatic neuroendocrine tumors (GEPNETs) are rare neoplasms that require a multidisciplinary approach for an optimal management. The traditional cytotoxic agents are of limited efficacy in the treatment of these tumors. A better understanding of the molecular pathways that characterize tumor growth has provided novel targets in cancer treatment. Several proteins have been implicated as having a crucial role in GEPNETs. Several proangiogenic molecules are overexpressed in GEPNETs including vascular endothelial growth factor (VEGF) and its receptors, and related signaling pathway components such as epidermal growth factor receptor (EGFR), Insulin growth factor-I receptor (IGF-IR) and PI3K-AKT-mTOR pathway. In this article we aim to review the recent development of the main molecules that target these proteins and have showed promising activity in the treatment of GEPNETs.

Mol Endocrinol. 2009 Nov 6;
Gleason CE, Ning Y, Cominski TP, Gupta R, Kaestner KH, Pintar JE, Birnbaum MJ

A family of IGF-binding proteins (IGFBP) exerts biological actions both dependent on and independent of IGF-I. A major effector of the Insulin/IGF-I signaling pathway, the serine/threonine protein kinase Akt, mediates cellular processes such as glucose uptake, protein synthesis, cell survival, and growth. IGF-I is required for normal organismal growth, and in the pancreatic beta-cell, the Insulin/IGF-I signaling pathway is critical for normal and adaptive maintenance of beta-cell mass. Expression of myrAkt1, an activated form of Akt, in the endocrine pancreas drives beta-cell expansion through dramatic increases in both islet and beta-cell size and number. Herein we present a comparative expression profiling of myrAkt1 transgenic islets that demonstrates the increased abundance of transcripts encoding proteins associated with growth, suppression of apoptosis, RNA processing, and metabolism. Although IGFBP5 is identified as a gene induced by Akt1 activation in the beta-cell, Igfbp5 expression is not necessary for myrAkt1 to augment beta-cell size or mass in vivo. However, in the absence of Igfbp5, mice demonstrate an increase in size and mild glucose intolerance. This is accentuated during diet-induced obesity, when Igfbp5-deficient mice have increased adiposity compared with wild-type mice on the same diet. These studies reveal a novel role for Igfbp5 in the control of growth and metabolism.

J Insect Physiol. 2009 Nov 13;
Okada Y, Miyazaki S, Miyakawa H, Ishikawa A, Tsuji K, Miura T

In many social hymenopteran species, workers possess functional ovaries that are physiologically inactive in the presence of queens. We investigated the ovarian regulatory mechanism of workers and reproductives in a queenless ponerine ant, Diacamma, using histological and molecular techniques. In this ant, clear reproductive differentiation occurs via a highly sophisticated dominance behavioral interaction called "gemmae mutilation". This clear and rapid bifurcation of reproductive physiology allows us to elucidate the detailed ovarian differentiation process. Histological characteristics of functional ovaries (fusomes and ring canals) were found in both workers and reproductives, suggesting that early oogenesis is not blocked in workers. Since Insulin/Insulin-like growth factor signaling (IIS) is known to control insect reproduction, orthologs of 2 positive IIS regulators, Insulin receptor and serine-threonine kinase Akt (protein kinase B), were cloned in Diacamma (DiaInR, DiaAkt); their expression patterns during reproductive differentiation were examined by real-time quantitative polymerase chain reaction; DiaInR and DiaAkt were strongly expressed in the gasters of reproductives. Whole-mount in situ hybridization of ovaries indicated that DiaInR and DiaAkt were expressed in nurse cells, oocytes, and upper germarial regions of reproductives but not of workers. Our data suggest that the IIS pathway accounts for reproductive differentiation in late oogenesis.

Curr Eye Res. 2009 Oct; 34(10): 867-76
Weng CY, Kothary PC, Verkade AJ, Reed DM, Del Monte MA

PURPOSE: To investigate the mitogenic activity of Insulin-like growth factor-1 (IGF-1) on the proliferation of human retinal pigment epithelial cells (hRPE) and to elucidate the role of vascular endothelial growth factor (VEGF) and MAP kinase (MAPK) in the IGF-1 signaling cascade. METHODS: Human RPE specimens were obtained from postmortem non-pathological eyes and cultured in vitro through several passages. Cellular proliferation in the presence of increasing concentrations of IGF-1 and IGF-1 + PD98059 (a known MAPK inhibitor) was measured by [(3)H]thymidine incorporation; trypan blue exclusion studies (T) verified cell viability. Under the same experimental conditions, synthesis of VEGF was measured utilizing [(14)C]methionine immunoprecipitation and immunocytochemical methods as well as Western blot analysis. RESULTS: IGF-1 stimulated hRPE proliferation, as demonstrated by [(3)H]thymidine incorporation. There was also an IGF-1-induced increase in VEGF synthesis as measured quantitatively by [(14)C]methionine-VEGF immunoprecipitation. This was qualitatively confirmed by immunocytochemistry and Western blotting. PD98059 suppressed both IGF-1-induced cell proliferation as well as IGF-1-stimulated VEGF production. CONCLUSIONS: These studies suggest that IGF-1 is a mitogen for hRPE cells and also stimulates production of the angiogenic factor, VEGF. Additionally, PD98059 inhibits the production of VEGF, suggesting that the MAP kinase pathway is involved in IGF-1-mediated angiogenesis.

J Biol Chem. 2009 Nov 5;
Tomilov AA, Bicocca V, Schoenfeld RA, Giorgio M, Migliaccio E, Ramsey JJ, Hagopian K, Pelicci PG, Cortopassi GA

A decrease in Reactive Oxygen Species (ROS) production has been associated with extended lifespan in animal models of longevity. Mice deficient in the p66Shc gene are long-lived, and their cells are both resistant to oxidative stress and produce less ROS. Our microarray analysis of p66Shc(-/-) mouse tissues showed alterations in transcripts involved in heme and superoxide production and Insulin signaling. Thus we carried out analysis of ROS production by NADPH Oxidase (PHOX) in macrophages of control and p66Shc-knockout mice. p66Shc(-/-) mice had a 40% reduction in PHOX-dependent superoxide production. To confirm whether the defect in superoxide production was a direct consequence of p66Shc deficiency, p66Shc was knocked down with siRNA in the macrophage cell line RAW264, and a 30% defect in superoxide generation was observed. The pathway of PHOX-dependent superoxide generation was investigated. PHOX protein levels were not decreased in mutant macrophages, however the rate and extent of phosphorylation of p47phox was decreased in mutants, as was membrane translocation of the complex. Consistently phosphorylation of protein kinase C delta, Akt and ERK (the kinases responsible for phosphorylation of p47phox) was decreased. Thus, p66Shc deficiency causes a defect in activation of the PHOX complex that results in decreased superoxide production. p66Shc-deficient mice have recently been observed to be resistant to atherosclerosis, and oxidant injury in kidney and brain. Since phagocyte-derived superoxide is often a component of oxidant injury and inflammation, we suggest that the decreased superoxide production by PHOX in p66Shc-deficient mice could contribute significantly to their relative protection from oxidant injury, and consequent longevity.

Mol Cancer. 2009 Nov 5; 8(1): 95
Yao JE, Yan M, Guan Z, Pan CB, Xia LP, Li CX, Wang LH, Long ZJ, Zhao Y, Li MW, Zheng FM, Xu J, Lin DJ, Liu Q

ABSTRACT: BACKGROUND: The mitotic Aurora-A kinase exerts crucial functions in maintaining mitotic fidelity. As a bona fide oncoprotein, Aurora A aberrant overexpression leads to oncogenic transformation. Yet, the mechanisms by which Aurora-A enhances cancer cell survival remain to be elucidated. RESULTS: Here, we found that Aurora-A overexpression was closely correlated with clinic stage and lymph node metastasis in tongue carcinoma. Aurora-A inhibitory VX-680 suppressed proliferation, induced apoptosis and markedly reduced migration in cancer cells. We further showed that Insulin-like growth factor-1, a PI3K physiological activator, reversed VX-680-decreased cell survival and motility. Conversely, wortmannin, a PI3K inhibitor, combined with VX-680 showed a synergistic effect on inducing apoptosis and suppressing migration. In addition, Aurora-A inhibition suppressed Akt activation, and VX-680-induced apoptosis was attenuated by Myr-Akt overexpression, revealing a cross-talk between Aurora-A and PI3K pathway interacting at Akt activation. Significantly, we showed that suppression of Aurora-A decreased phosphorylated Akt and was associated with increased IkappaB alpha expression. By contrast, Aurora-A overexpression upregulated Akt activity and downregulated IkappaB alpha, these changes were accompanied by nuclear translocation of nuclear factor-kappa B and increased expression of its target gene Bcl-xL. Lastly, Aurora-A overexpression induced IkappaB alpha reduction was abrogated by suppression of Akt either chemically or genetically. CONCLUSIONS: Taken together, our data established that Aurora-A, via activating Akt, stimulated nuclear factor-kappa B signaling pathway to promote cancer cell survival, and promised a novel combined chemotherapy targeting both Aurora-A and PI3K in cancer treatment.