Multi-omics identify xanthine as a pro-survival metabolite for nematodes with mitochondrial dysfunction.

Aberrant mitochondrial function contributes to the pathogenesis of various metabolic and chronic disorders. Inhibition of insulin/IGF-1 signaling (IIS) represents a promising avenue for the treatment of mitochondrial diseases, although many of the molecular mechanisms underlying this beneficial effect remain elusive. Using an unbiased multi-omics approach, we report here that IIS inhibition reduces protein synthesis and favors catabolism in mitochondrial deficient Caenorhabditis elegans We unveil that the lifespan extension does not occur through the restoration of mitochondrial respiration, but as a consequence of an ATP-saving metabolic rewiring that is associated with an evolutionarily conserved phosphoproteome landscape. Furthermore, we identify xanthine accumulation as a prominent downstream metabolic output of IIS inhibition. We provide evidence that supplementation of FDA-approved xanthine derivatives is sufficient to promote fitness and survival of nematodes carrying mitochondrial lesions. Together, our data describe previously unknown molecular components of a metabolic network that can extend the lifespan of short-lived mitochondrial mutant animals.

A nonrandomized controlled clinical pilot trial on 8 wk of intermittent fasting (24 h/wk).

OBJECTIVE: The aim of the study was to evaluate whether intermittent fasting (IF) is an effective preventive measure, and whether it is feasible for healthy volunteers under every day conditions. METHODS: A nonrandomized controlled clinical trial on IF was performed with healthy volunteers over a period of 8 wk, and a subsequent 4-mo follow-up. Outcomes were assessed at baseline, after 8 wk, and after 6 mo. Volunteers who were not interested in fasting served as a control group. Participants in the fasting group were asked to continue their regular nutritional habits on the nonfasting days, whereas the control group maintained their habitual nutrition throughout the whole period. Outcomes included changes of metabolic parameters (insulin, glucose, insulin resistance, insulin-like growth factor-1, brain-derived neurotropic factor, lipids, liver enzymes, hemoglobin A1c) and coagulation markers; bioelectrical impedance analysis; body mass index; abdominal girth; blood pressure; general quality of life (five-item World Health Organization Well-Being Index [WHO-5] questionnaire), as well as mood and anxiety (Hospital Anxiety and Depression Scale [HADS], Profile of Mood States, Flourishing-Scale, visual analog scale, Likert scales). The intervention consisted of a fasting day, which was repeated every week for 8 wk, with abstinence from solid food between 00:00 and 23:59 at minimum and a maximum caloric intake of 300 kcal on each fasting day. A per-protocol analysis was performed. P < 0.05 was considered significant. RESULTS: Thirty-six volunteers were included; 22 allocated themselves to the fasting group, and 14 to the control group. Thirty-three data sets were included in the final analysis. Although significant in-group changes were observed in both groups for a number of outcomes after 8 wk and 6 mo, no significant between-group differences were observed for any outcome other than overall body fat mass after 8 wk as well as for the HADS total score and the WHO-5 total score after 6 mo, all in favor of the fasting group. However, none of the between-group differences were clinically relevant. CONCLUSIONS: We did not find any clinically relevant differences between groups in this controlled clinical pilot trial of 8 wk of IF in healthy volunteers. Further clinical research in this field is warranted to further analyze mechanisms and effects of IF.

Inhibitory effect of imperatorin on insulin-like growth factor-1-induced sebum production in human sebocytes cultured in vitro.

AIMS: Acne is a common skin disease that originates in the sebaceous gland. The pathogenesis of acne is very complex, involving the increase of sebum production and perifollicular inflammation. In this study, we screened the anti-lipogenic material and demonstrated its effect using cultured human sebocytes. MAIN METHODS: Normal human sebocytes were cultured by explanting the sebaceous glands. To evaluate the anti-lipogenic effect, sebocytes were treated with test materials and (14)C-acetate incorporation assay was performed. KEY FINDINGS: To screen the anti-lipogenic materials, we tested the effect of many herbal plant extracts. We found that Angelica dahurica extract inhibited the insulin-like growth factor-1 (IGF-1)-induced sebum production in terms of squalene synthesis in sebocytes. Furthermore, imperatorin isolated from A. dahurica showed remarkable inhibitory effect on squalene production as well as squalene synthase promoter activity. To investigate the putative action mechanism, we tested the effect of imperatorin on intracellular signaling. The results showed that imperatorin inhibited IGF-1-induced phosphorylation of Akt. In addition, imperatorin significantly down-regulated PPAR-γ and SREBP-1, the important transcription factors for lipid synthesis. SIGNIFICANCE: These results suggest that imperatorin has a potential for reducing sebum production in sebocytes, and can be applicable for acne treatment.

Insulin-like growth factor-I regulates LH release by modulation of kisspeptin and NMDA-mediated neurotransmission in young and middle-aged female rats.

This study investigated potential mechanisms by which age and IGF-I receptor (IGF-Ir) signaling in the neuroendocrine hypothalamus affect estradiol-positive feedback effects on GnRH neuronal activation and on kisspeptin and N-methyl-D-aspartate (NMDA)-induced LH release and on the abundance of NMDA receptor subunits Nr1 and Nr2b and Kiss1r transcript and protein in the hypothalamus of young and middle-aged female rats. We infused vehicle, IGF-I, or JB-1, a selective antagonist of IGF-Ir, into the third ventricle of ovariectomized female rats primed with estradiol or vehicle and injected with vehicle, kisspeptin (3 or 30 nmol/kg), or NMDA (15 or 30 mg/kg). Regardless of dose, NMDA and kisspeptin resulted in significantly more LH release, GnRH/c-Fos colabeling, and c-Fos immunoreative cells in young than in middle-aged females. Estradiol priming significantly increased Kiss1r, Nr1, and Nr2b receptor transcript and protein abundance in young but not middle-aged female hypothalamus. JB-1 attenuated kisspeptin and NMDA-induced LH release, numbers of GnRH/c-Fos and c-Fos cells, and Kiss1r, Nr1, and Nr2b transcript and protein abundance in young females to levels observed in middle-aged females. IGF-I significantly enhanced NMDA and kisspeptin-induced LH release in middle-aged females without increasing numbers of GnRH/c-Fos or c-Fos immunoreactive cells. IGF-I infusion in middle-aged females also increased Kiss1r, Nr1, and Nr2b protein and transcript to levels that were equivalent to young estradiol-primed females. These findings indicate that age-related changes in estradiol-regulated responsiveness to excitatory input from glutamate and kisspeptin reflect reduced IGF-Ir signaling.

Green tea (-)-epigallocatechin gallate inhibits IGF-I and IGF-II stimulation of 3T3-L1 preadipocyte mitogenesis via the 67-kDa laminin receptor, but not AMP-activated protein kinase pathway.

SCOPE: This study investigated the pathways involved in epigallocatechin gallate (EGCG) modulation of insulin-like growth factor (IGF)-I-stimulated and IGF-II-stimulated mitogenesis in 3T3-L1 preadipocytes. METHODS AND RESULTS: We found that this process was dose and time dependent, and caused by suppression of IGF-I-stimulated and IGF-II-stimulated phosphorylation of p66Shc and mitogen-activated protein kinase (MAPK) pathway proteins, including MEK1 kinase (RAF1), extracellular signal-regulated protein kinase (ERK) kinase (MEK1), and ERK 1 and ERK 2 (ERK1/2), but not phospho-Jun-N-terminal kinase, protein kinase B, p52Shc, or p46Shc. Furthermore, EGCG inhibited the IGF-I-stimulated phosphorylation of the IGF-I receptor-beta (IGF-IR ß), the association of IGF-IR with the p66Shc protein, and the IGF-II-stimulated associations of the IGF-II receptor with G(αi-2) and p66Shc proteins, suggesting that EGCG selectively affects particular types of Shc and MAPK family members. Pretreatment with antiserum against the EGCG receptor (also known as the 67-kDa laminin receptor; 67LR), but not with an adenosine monophosphate (AMP)-activated protein kinase (AMPK) inhibitor, prevented the inhibitory actions of EGCG on IGF-I- and IGF-II-stimulated ERK1/2 phosphorylation and subsequent preadipocyte proliferation. CONCLUSION: The results of this study suggest that EGCG mediates anti-IGF-I and anti-IGF-II signals in preadipocyte mitogenesis via the 67LR but not the AMPK pathway.

IGF1/insulin receptor kinase inhibition by BMS-536924 is better tolerated than alloxan-induced hypoinsulinemia and more effective than metformin in the treatment of experimental insulin-responsive breast cancer.

Epidemiologic and experimental evidence suggest that a subset of breast cancer is insulin responsive, but it is unclear whether safe and effective therapies that target the insulin receptor (IR), which is homologous to oncogenes of the tyrosine kinase class, can be developed. We demonstrate that both pharmacologic inhibition of IR family tyrosine kinase activity and insulin deficiency have anti-neoplastic activity in a model of insulin-responsive breast cancer. Unexpectedly, in contrast to insulin deficiency, pharmacologic IR family inhibition does not lead to significant hyperglycemia and is well tolerated. We show that pharmacokinetic factors explain the tolerability of receptor inhibition relative to insulin deficiency, as the small molecule receptor kinase inhibitor BMS-536924 does not accumulate in muscle at levels sufficient to block insulin-stimulated glucose uptake. Metformin, which lowers insulin levels only in settings of hyperinsulinemia, had minimal activity in this normoinsulinemic model. These findings highlight the importance of tissue-specific drug accumulation as a determinant of efficacy and toxicity of tyrosine kinase inhibitors and suggest that therapeutic targeting of the IR family for cancer treatment is practical.

Targeting the type I insulin-like growth factor system for breast cancer therapy.

The insulin-like growth factors (IGFs) acting via the type I IGF receptor (IGF-1R) regulate cancer cell proliferation, survival, metabolism and metastasis. Drugs targeting the IGF-1R are being tested in human clinical trials for cancer therapy and it seems likely that this class of drugs could be approved soon. Recent data suggests that insulin receptor, which is closely related to IGF-1R, should also be targeted to maximally inhibit the system. Furthermore, biomarkers that will identify patients whose tumors are driven by IGF-1R and biomarkers that allow monitoring or prediction of response are needed. This article reviews the different drugs against IGF-1R that are being tested in and how this receptor pathway can be optimally targeted for cancer therapy with an emphasis on breast cancer therapy.

Lycopene effects contributing to prostate health.

Epidemiological evidence links lycopene consumption with decreased prostate cancer risk. Several signaling pathways have been identified as players in prostate cancer development. Chronic prostatitis, for example, due to infections, is a suggested risk factor for prostate cancer. Endogenous production of reactive oxygen species during inflammation may lead to oxidative DNA damage, which can be mutagenic, if unrepaired. Androgen signaling, cytokine (IL-6, IL-4) and growth factor signaling (e.g., IGF, Wnt/beta-catenin) cross-talk via PI3K/Akt, MAPK, and Jak/STAT pathways have been identified as major controllers of prostate growth. During disease progression, and after androgen ablation therapy, the remaining operational pathways are upregulated to compensate for the lost growth signal, finally resulting in androgen-independent prostate cancer. Lycopene modulates several of the aforementioned pathways, providing a promising rationale for prostate cancer risk reduction by lycopene: In many experimental setups, lycopene reduced inflammatory signals, prevented oxidative DNA damage, modulated the expression or activity of IGF axis members, of Wnt/beta-catenin and androgen signalling, and enhanced gap junctional communication. Lycopene's influence on these pathways likely contributes to the observed cell growth inhibition and apoptosis induction by lycopene. A substantial part of the lycopene effects can be explained by its antioxidant action, but other mechanisms might also be involved.

Multitargeted therapy of cancer by green tea polyphenols.

Tea ranks second only to water as a major component of fluid intake worldwide and has been considered a health-promoting beverage since ancient times. For the past two decades, we and others have been investigating the potential cancer preventive and therapeutic effects of green tea and its polyphenolic mixture termed GTP. It has become clear that much of these effects of GTP are mediated by its most abundant catechin, epigallocatechin gallate (EGCG). Large amount of encouraging data from in vitro and animal models has emerged making clear that green tea is a nature's gift molecule endowed with anticancer effects. Epidemiological and geographical observations suggest that these laboratory data may be applicable to human population. Clinical trials of GTP, especially in prostate cancer patients have yielded encouraging results. This article briefly reviews properties of GTP, especially EGCG with reference to multitargeted therapy of cancer.

Burkholone, a new cytotoxic antibiotic against IGF-I dependent cells from Burkholderia sp.

In the course of our screening program for new inhibitors of IGF-I signaling, we isolated a new cytotoxic antibiotic, burkholone, from the culture broth of Burkholderia sp. QN15488. The structure of burkholone was determined to be (E)-3-methyl-2-(2-octenyl)-4-quinolone by a series of NMR analyses. Burkholone induced cell death 32D/GR15 cells with an IC50 value of 160 nM in IGF-I containing medium, while no cell death was observed in IL-3 containing medium even at the concentration of 37 microM.

Regulation of IGF-I production and proliferation of human leiomyomal smooth muscle cells by Scutellaria barbata D. Don in vitro: isolation of flavonoids of apigenin and luteolin as acting compounds.

Scutellaria barbata D. Don (Lamiaceae) (SB) is a perennial herb, which is natively distributed throughout Korea and southern China. This herb is known in traditional Chinese Medicine as Ban-Zhi-Lian and traditional Korean medicine as Banjiryun, respectively. SB has been used as an anti-inflammatory and antitumor agent. We aimed to determine the expression of growth factor molecules for growth inhibition after treatment of SB in two different human myometrial smooth muscle cell (SMC)s and leiomyomal SMCs. Water-soluble ingredients of SB, myometrial SMCs, and the leiomyomal cell lines were used in vitro. SB significantly reduced cell numbers in culture and arrested cell proliferation, and also induced apoptosis, indicating that the presence of an intact apoptotic pathway was demonstrated in these cells by SB. Uterine leiomyoma is the most common benign smooth muscle cell tumor of the myometrium. The expression of insulin-like growth factor-I (IGF-I) was measured at the mRNA and protein level in myometrium and leiomyomal cells with and without treatment with a water extract of SB for 3 days. IGF-I mRNA expression was significantly higher in leiomyomal cells than in myometrium cells. The IGF-I protein was more abundant in leiomyomal cells than in myometrium. When SB was treated to the cells, the IGF-I protein concentrations in myometrial and leiomyomal cells from the SB-treated cells were similar. The results indicated that IGF-I expression is probably associated with a proliferation of leiomyomal cells than myometrium. However, SB down-regulated the IGF-I expression where IGF-I contributes to the selective growth of the leiomyoma. Therefore, growth modulation of LMs by SB occurs via mechanisms dependent of apoptosis. The raw materials were extracted and subjected to functional isolation for the active molecules in the present assay systems. The five flavonoids were isolated and the chemical structures of resveratrol, baicalin, berberine, apigenin, and luteolin were determined. The effects of resveratrol, baicalin, and berberine on the above parameters have not been significantly evidenced, whereas apigenin and luteolin were effective. The anti-proliferative compounds apigenin and luteolin belong to the flavones, a class of flavonoids and are characterized as selectively inhibitors of the growth of LM cells. Our findings suggest that flavonoids of apigenin and luteolin are potentially useful for the development of therapeutic treatments of cancer. These data also suggest that SB reduces tumor volume with inducing a concomitant increase in the rate of apoptosis.

Oral consumption of green tea polyphenols inhibits insulin-like growth factor-I-induced signaling in an autochthonous mouse model of prostate cancer.

We earlier demonstrated that oral infusion of green tea polyphenols inhibits development and progression of prostate cancer in transgenic adenocarcinoma of the mouse prostate (TRAMP) model. Evidence indicates that elevated levels of IGF-I with concomitant lowering of IGF binding protein (IGFBP)-3 are associated with increased risk for prostate cancer development and progression. In this study, we examined the role of IGF/IGFBP-3 signaling and its downstream and other associated events during chemoprevention of prostate cancer by green tea polyphenols in TRAMP mice. Our data demonstrated an increase in the levels of IGF-I, phosphatidylinositol 3'-kinase, phosphorylated Akt (Thr-308), and extracellular signal-regulated kinase 1/2 with concomitant decrease in IGFBP-3 in dorso-lateral prostate of TRAMP mice during the course of cancer progression, i.e., as a function of age. Continuous green tea polyphenol infusion for 24 weeks to these mice resulted in substantial reduction in the levels of IGF-I and significant increase in the levels of IGFBP-3 in the dorso-lateral prostate. This modulation of IGF/IGFBP-3 was found to be associated with an inhibition of protein expression of phosphatidylinositol 3'-kinase, phosphorylated forms of Akt (Thr-308) and extracellular signal-regulated kinase 1/2. Furthermore, green tea polyphenol infusion resulted in marked inhibition of markers of angiogenesis and metastasis most notably vascular endothelial growth factor, urokinase plasminogen activator, and matrix metalloproteinases 2 and 9. Based on our data, we suggest that IGF-I/IGFBP-3 signaling pathway is a prime pathway for green tea polyphenol-mediated inhibition of prostate cancer that limits the progression of cancer through inhibition of angiogenesis and metastasis.

PADMA-28, a traditional Tibetan herbal preparation, blocks cellular responses to bFGF and IGF-I.

The growth factors basic fibroblast growth factor (bFGF) and insulin-like growth factor 1 (IGF-I) have been implicated in the pathophysiology of atherosclerosis and restenosis. The Tibetan herbal preparation PADMA-28 (a mixture of 22 plants which is used as an anti-atherosclerosis agent) was tested for its ability to inhibit the mitogenic activity of bFGF and IGF-I, growth factors involved in restenosis, atherosclerosis and tumour progression. DNA synthesis and proliferation of vascular smooth muscle cells, in response to serum bFGF, thrombin, or combinations thereof, were abrogated in the presence of microgram amounts of both the aqueous and organic, partially purified, extracts of PADMA-28. These fractions also inhibited IGF-I-mediated proliferation, migration and invasion of tumour cells responsive to IGF-I. The inhibition by PADMA 28 was reversible upon removal of the PADMA extracts, indicating that the effects were not related to cell toxicity. These and other properties (i.e., anti-oxidant activity) of PADMA-28 may be responsible for its beneficial effect as an anti-atherosclerotic agent, suggesting that this herbal preparation may have potential applications in the prevention of intimal hyperplasia and arterial stenosis secondary to coronary angioplasty and bypass surgery, as well as in the prevention and treatment of other vascular diseases and tumour growth and metastasis.

Black tea polyphenols inhibit IGF-I-induced signaling through Akt in normal prostate epithelial cells and Du145 prostate carcinoma cells.

Tea polyphenols have been proposed as potential chemopreventive agents against prostate cancer, primarily because of their high intake by populations with reduced cancer incidence and their reported ability to inhibit proliferation and increase apoptosis in prostate cancer cells in culture. Insulin-like growth factor-I (IGF-I) has been implicated as a risk factor for the development of prostate cancer by epidemiological studies and has been shown to be causative in animal models. One of the primary signal transduction pathways activated by IGF-I binding to its receptor is the Akt pathway. We determined that phosphorylated Akt levels are very low in serum-starved human normal prostate epithelial cells (PrEC) and Du145 prostate carcinoma cells, and that treatment of these cells with IGF-I results in a rapid and sustained phosphorylation of Akt. Pre-treatment of PrEC and Du145 cells with doses as low as 20 microg/ml of a mixture of black tea polyphenols (BTP) substantially reduced IGF-I-mediated Akt phosphorylation. This effect of BTP appears to be due partially to the reduced autophosphorylation of IGF-I receptor-1 in BTP-treated cells. BTP pre-treatment also decreased downstream effects of Akt activation including phosphorylation of glycerol synthase kinase-3, increased cyclin D1 protein levels and increased DNA synthesis. Our results indicate that polyphenols from black tea inhibit the IGF-I signal transduction pathway, which has been linked to increased prostate cancer incidence in human populations and, therefore, provide further support for the potential of BTP to prevent prostate cancer.

Arginine counteracts the inhibitory effect of recombinant human insulin-like growth factor I on the somatotroph responsiveness to growth hormone-releasing hormone in humans.

Insulin-like growth factor I (IGF-I) exerts a negative feedback effect on GH secretion via either direct actions at the pituitary level or indirect ones at the hypothalamic level, through stimulation of somatostatin (SS) and/or inhibition of GHRH release. In fact, recombinant human IGF-I (rhIGF-I) in humans inhibits spontaneous GH secretion as well as the GH response to GHRH and even more to GH/GH-releasing peptides, whose main action is on the hypothalamus, antagonizing SS and enhancing GHRH activity. The aim of the present study was to further clarify in humans the mechanisms underlying IGF-I-induced inhibition of somatotroph secretion. In six normal young volunteers (all women; mean +/- SEM: age, 28.3+/-1.2 yr; body mass index, 21.3+/-1.2 kg/m2) we studied the GH response to GHRH (1 microg/kg, iv, at 0 min), both alone and combined with arginine (ARG; 0.5 g/kg, iv, from 0-30 min), which probably acts via inhibition of hypothalamic SS release, after pretreatment with rhIGF-I (20 microg/kg, sc, at -180 min) or placebo. rhIGF-I increased circulating IGF-I levels (peak at -60 vs. -180 min: 54.9+/-3.9 vs. 35.9+/-3.3 mmol/L; P < 0.05) to a reproducible extent, and these levels remained stable and within the normal range until 90 min. The mean GH concentration over 3 h (from -180 to 0 min) before ARG and/or GHRH was not modified by placebo or rhIGF-I. After placebo, the GH response to GHRH (peak, 23.6+/-2.9 microg/L) was strikingly enhanced (P < 0.05) by ARG coadministration (69.6+/-9.9 microg/L). rhIGF-I blunted the GH response to GHRH (13.1+/-4.5 microg/L; P < 0.05), whereas that to GHRH plus ARG was not modified (59.5+/-8.9 microg/L), although it occurred with some delay. Mean glucose and insulin concentrations were not modified by either placebo or rhIGF-I. In conclusion, ARG counteracts the inhibitory effect of rhIGF-I on somatotroph responsiveness to GHRH in humans. These findings suggest that the acute inhibitory effect of rhIGF-I on the GH response to GHRH takes place on the hypothalamus, possibly via enhancement of SS release, and that ARG overrides this action.

Growth failure occurs through a decrease in insulin-like growth factor 1 which is independent of undernutrition in a rat model of colitis.

BACKGROUND: Linear growth retardation is a frequent complication of inflammatory bowel disease in children. The precise mechanisms causing growth failure are not known. AIMS: To determine the relative contribution of reduced calorie intake and inflammation to linear growth delay and to determine the effect of inflammation on the hypothalamic-pituitary-growth axis. METHODS: Linear growth was assessed in prepubertal rats with trinitrobenzenesulphonic acid (TNBS) induced colitis, in healthy free feeding controls, and in a pair-fed group (i.e. healthy animals whose daily food intake was matched to the colitic group thereby distinguishing between the effects of undernutrition and inflammation). RESULTS: Changes in length over five days in the TNBS colitis and pair-fed groups were 30% and 56%, respectively, of healthy free feeding controls. Linear growth was significantly reduced in the colitic group compared with the pair-fed group. Nutritional supplementation in the colitic group increased weight gain to control values but did not completely reverse the growth deficit. Plasma interleukin 6 (IL-6) concentrations were sixfold higher in the colitic group compared with controls. Plasma concentrations of insulin-like growth factor 1 (IGF-1) but not growth hormone (GH) were significantly lower in the colitic compared with the pair-fed group. Administration of IGF-1 to the colitic group increased plasma IGF-1 concentrations and linear growth by approximately 44-60%. CONCLUSIONS: It seems likely that approximately 30-40% of linear growth impairment in experimental colitis occurs as a direct result of the inflammatory process which is independent of undernutrition. Inflammation acts principally at the hepatocyte/IGF-1 level to impair linear growth. Optimal growth in intestinal inflammation may only be achieved by a combination of nutritional intervention and anticytokine treatment.

Reduction in atherosclerotic lesion size in pigs by alphaVbeta3 inhibitors is associated with inhibition of insulin-like growth factor-I-mediated signaling.

Insulin-like growth factor-I (IGF-I) is a potent stimulant of smooth muscle cell (SMC) migration and proliferation and has been implicated in the development of experimental atherosclerotic lesions. Because optimal stimulation of SMC in vitro by IGF-I requires ligand occupancy of alphaVbeta3, these studies were conducted to determine whether alphaVbeta3 antagonists would result in a change in lesion size and whether they could alter IGF-I-mediated actions. Clamps were placed on the carotid and femoral arteries of normal pigs that had been fed a high-cholesterol diet for 4 weeks. alphaVbeta3 inhibitors (SC-69000, SC-65811) (10(-6) mol/L) or saline were infused for 2 weeks into the peristenotic area. Lesion area, the number of SMC layers, and proliferating cell nuclear antigen positive cells were determined in a 1.2-mm segment of each artery. Lesion areas were 304 788+/-113 453 micron(2) (saline), compared with 149 799+/-35 456 micron(2) (SC-69000) (P<0.01). Lesion areas in arteries treated with SC-64258, a compound that does not bind to alphaVbeta3, were 310 284+/-160 467 micron(2), P=not significant. In a second experiment, lesion areas were 110 391+/-17 347 micron(2) (saline) and 59 533+/-17 568 micron(2) (SC-65811, P<0.001). Neointimal SMC layers were reduced by SC-65811 from 7.4+/-4.5 to 3.0+/-0.4 (P<0.001). To determine whether IGF-I action was altered, IGF binding protein-5, which is synthesized in response to IGF-I, was analyzed. IGF-I binding protein-5 mRNA abundance was reduced by 67+/-8% in the 6 lesions treated with SRL-69000 compared with saline controls (P<0.001). We conclude that alphaVbeta3 antagonists block the development of lesions in pigs that have been induced by a high-cholesterol diet and stenosis, and the effect of these compounds is associated with their ability to inhibit IGF-I-mediated signaling.

Ethanol inhibits insulin-like growth factor-1-mediated signalling and proliferation of C6 rat glioblastoma cells.

BACKGROUND: Alcohol consumption during pregnancy often results in disorders of fetal development (Fetal Alcohol Syndrome). The brain appears to be particularly vulnerable, and alcohol abuse during pregnancy is probably the most common cause of acquired mental retardation. We therefore studied the in vitro effects of ethanol on insulin-like growth factor-1 (IGF-1)-mediated proliferation of rat C6 glioblastoma cells. EXPERIMENTAL DESIGN: The proliferation of C6 rat glioblastoma cells was measured in serum-free medium supplemented with specific growth factors in the presence or absence of ethanol. The effect of ethanol on IGF-1 receptor and insulin receptor substrate 1 (IRS-1) tyrosine phosphorylation was determined by immunoprecipitation and Western blotting, as was the phosphatidylinositol 3-kinase content within IRS-1 immunoprecipitates. RESULTS: C6 cells grew slowly in serum-free medium and proliferated in response to IGF-1. Ethanol, at physiologically tolerated concentrations, markedly inhibited the growth of C6 cells in response to IGF-1, but had no effect on the proliferative rate in the presence of platelet-derived growth factor or 1% fetal bovine serum. Inhibition of cell proliferation was evident when ethanol was only present during a 1-hour pulse of IGF-1. Cell growth in the presence of IGF-2 was also prevented by ethanol. The inhibition of IGF-1-mediated cell proliferation was accompanied by abrogation of IGF-1 receptor tyrosine autophosphorylation. Ethanol also interfered with the IGF-1-induced tyrosine phosphorylation of IRS-1, and the association of phosphatidylinositol-3 kinase with IRS-1. CONCLUSIONS: The data indicate that physiologically relevant concentrations of ethanol inhibit the responses of glial cells to IGF-1, including IGF-1 receptor autophosphorylation, IRS-1 and phosphatidylinositol-3 kinase activation, and cell growth.

Similar hormonal changes in sera from scorbutic and fasted (vitamin C-supplemented) guinea pigs, including decreased IGF-I and appearance of an IGF-I reversible mitogenic inhibitor.

We previously proposed that the decreased rates of synthesis of collagen and proteoglycans in vitamin C-deficient guinea pigs were unrelated to the role of ascorbate in proline hydroxylation but might result from modulation of hormones known to change during fasting. In the present studies, we found that sera from guinea pigs on an ascorbate-free diet for 24-28 days or from those fasted for 4 days, with vitamin C supplementation, showed similar changes in the concentrations of several hormones. EGF and IGF-II concentrations were unchanged, but cortisol was increased 3-5 times and growth hormone was increased to approximately twice normal levels. Thyroxine and IGF-I concentrations were decreased to 40% and 25-33% of normal levels, respectively. The decrease in serum IGF-I must occur by a growth hormone-independent pathway. The extent of changes in hormone concentrations in sera from ascorbate-deficient guinea pigs was correlated with the extent of weight loss. Sera from scorbutic and fasted guinea pigs failed to stimulate DNA synthesis in quiescent BALB 3T3 cells in the presence of saturating concentrations of EGF and PDGF. Addition of experimental sera to normal serum showed that lack of mitogenic activity was due to the presence of an inhibitor. Inhibition was not related to IGF-I concentrations in the sera, although it was reversed by the addition of IGF-I to sera from scorbutic or fasted animals. These results support our proposed model and suggest that IGF-I, as well as an inhibitor of its activity, plays a role in the regulation of growth by vitamin C and other nutrients.