Insulin-like Growth factor-I mRNA Research Articles

Involvement of Insulin-Like Growth Factor-I Secretion and All-Trans-Retinoic Acid-Induced Decrement in Viability in MCF-7 Cells

Background/Aim: Insulin-like growth factor-I (IGF-I) is associated with survival, apoptosis and proliferation in MCF-7 cells. All-trans-retinoic acid (RA) is used as a cancer therapeutic, but the use of RA in cancer therapy is limited by the unpredictable resistance of cancer cells to drug action. Furthermore, the relationship of IGF-I with RA-induced decrement in cell viability has yet to be elucidated. Materials and Methods: MCF-7 cells were grown as confluent monolayers. To demonstrate the signaling pathways and roles of IGF-I, we suppressed endogenous target IGF-I with specific small interfering RNA treatment. Protein kinase C-δ and insulin receptor substrate 1 (IRS-1) protein levels were analyzed by Western blot. Radioimmunoassays were used to assess the concentration of endogenous IGF-I, and RT-PCR was used to assess IGF-I mRNA expression. Cell viability was analyzed with the MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide] assay. Results: We showed that RA treatment resulted in a dose- and time-dependent decrease in the secretion and synthesis of IGF-I. Subsequently, we found that suppression of IGF-I and IRS-1 protein decreased cell viability. In contrast, suppression of protein kinase C-δ and stimulation of IGF-I protected cells from RA-induced decrement in cell viability. The combination of RA treatment with IGF-I or IRS-1 small interfering RNA resulted in an additive decrease in cell viability. Conclusion: These results indicate that IGF-I plays an important role in the effect of RA and that suppression of IGF-I is implicated in the RA-induced inhibition of cell viability in MCF-7 cells.

Effect of dietary methionine on growth performance and insulin-like growth factor-I mRNA expression of growing meat rabbits

An experiment was conducted to determine the effects of different amounts of dietary methionine on growth performance, serum protein, growth hormone (GH), insulin-like growth factor-I (IGF-I) concentrations and IGF-I mRNA expression of growing meat rabbits. One hundred weaned growing meat rabbits were allocated to individual cages and randomly divided into five groups. The methionine addition concentrations of the five groups were 0, 2, 4, 6 and 8 g/kg diet (as-fed basis) and sulphur amino acids (SAA) concentrations ranging from 3.8 to 11.6 g/kg diet, respectively. The results obtained were as follows: the average daily gain of 2, 4 and 6 g/kg diet groups was higher than that of 0 g/kg diet group (p < 0.01). The feed gain ratio of the 4 g/kg diet group was lower than those of 0 and 8 g/kg diet group (p < 0.01). Methionine concentrations did not affect serum urea nitrogen, total protein, insulin and IGF-I concentration (p > 0.05). The quadratic effects of methionine on the serum concentration of albumin (Alb) and GH were obtained (p = 0.013, p = 0.018). The quadratic effect of methionine amount on IGF-I mRNA expression was obtained (p = 0.045). The serum concentration of Alb of the 4 g/kg diet group was higher than those of 0 and 8 g/kg diet group (p < 0.01). The serum concentration of GH of 8 g/kg diet group was higher than that of the 0 g/kg diet group (p < 0.05). The liver IGF-I mRNA expression of 4 g/kg diet group was higher than those of the 0 and 8 g/kg diet group (p < 0.05). Providing a diet mainly consisted of corn, wheat bran and peanut vine, the optimum dietary methionine addition concentration and SAA concentration for a weaner to 2-month-old growing meat rabbits were shown to be 2 and 5.7 g/kg diet respectively.

Effects of Zinc Supplementation and Deficiency on Bone Metabolism and Related Gene Expression in Rat

One hundred male rats were randomly divided into four groups (n = 25) and fed a Zn-adequate diet (ZA, 46.39 mg/kg), Zn-deficient diet (ZD, 3.20 mg/kg), Zn-overdose diet (ZO, 234.39 mg/kg), or were pair-fed a Zn-adequate diet (PF) for 5 weeks, respectively. The body weight, femur weight, and activity of alkaline phosphatase (ALP) were reduced in the ZD group but were increased in the ZO group. Zn concentrations in both liver and femur were elevated in the ZO group, whereas femur Zn was decreased in the ZD group. The concentrations of calcium and phosphorus were lower in the ZD than those in other groups. Serum calcium concentration was decreased in the ZD. The relative expression level of ALP was decreased in both ZD and PF, and no significant differences were observed between ZO and ZA. Insulin-like growth factor-I (IGF-I) mRNA level was reduced in the ZD but unchanged in the ZO and PF group. Zn deficiency also decreased ALP mRNA level as compared with that of PF group. Carbonic anhydrase II mRNA level was not affected by Zn. Nevertheless, dietary Zn influenced the growth, bone metabolism, and expression of IGF-I and ALP in male growing rats.

Limaprost reduces motor disturbances by increasing the production of insulin-like growth factor I in rats subjected to spinal cord injury

Calcitonin gene-related peptide (CGRP) released from sensory neurons increases the production of a neuroprotective substance insulin-like growth factor I (IGF-I), and sensory neuron stimulation contributes to a reduction of spinal cord injury (SCI) by inhibiting inflammatory responses in rats. Because receptors for prostaglandin E₂ (EP receptors) are present on sensory neurons, it is possible that prostaglandin E₁ analog limaprost reduces SCI by increasing IGF-I production through sensory neuron stimulation. We examined this possibility in rats subjected to compression-trauma-induced SCI. Limaprost increased the CGRP release from dorsal root ganglion (DRG) neurons isolated from rats, and this increase was reversed by pretreatment with the EP4 receptor antagonist ONO-AE3-208. Spinal cord tissue levels of CGRP and IGF-I were increased after the induction of SCI, peaking at 2 h postinduction. The intravenous administration of limaprost enhanced increases of spinal cord tissue levels of CGRP, IGF-I, and IGF-I mRNA at 2 h after the induction of SCI. Increases of spinal cord tissue levels of tumor necrosis factor, caspase-3, myeloperoxidase, and the number of apoptotic nerve cells were inhibited by the administration of limaprost. Motor disturbances of hind legs in animals subjected to the compression-trauma-induced SCI were reduced by the administration of limaprost. These effects of limaprost were reversed completely by pretreatment with a specific transient receptor potential vanilloid 1 inhibitor SB366791 and by sensory denervation. These observations strongly suggest that limaprost may increase the IGF-I production by stimulating sensory neurons in the spinal cord, thereby ameliorating compression-trauma-induced SCI through attenuation of inflammatory responses.

Impact of viral-mediated IGF-I gene transfer on skeletal muscle following cast immobilization.

Insulin-like growth factor I (IGF-I) is a potent myogenic factor that plays a critical role in muscle regeneration and muscle hypertrophy. The purpose of this study was to evaluate the effect of IGF-I overexpression on the recovery of muscle size and function during reloading/reambulation after a period of cast immobilization in predominantly fast twitch muscles. In addition, we investigated concomitant molecular responses in IGF-I receptor and binding proteins (BPs). Recombinant adeno-associated virus vector for IGF-I (rAAV-IGF-IA) was injected into the anterior compartment of one of the hindlimbs of young (3 wk) C57BL6 female mice. At 20 wk of age, both hindlimbs were cast immobilized in a shortened position for 2 wk to unload the tibialis anterior (TA) and extensor longus digitorum (EDL) muscles. The TA and EDL muscles were removed bilaterally after 2 wk of cast immobilization and after 1 and 3 wk of free cage reambulation. Increases in IGF-I mRNA and protein levels with IGF-I overexpression were associated with significant increases in muscle wet weight, fiber size, and tetanic force, although overexpression did not protect against cast immobilization-induced muscle atrophy. After 1 wk of reambulation, evidence of enhanced muscle regeneration was noted in IGF-I-overexpressing muscles with an increased prevalence of central nuclei, embryonic myosin, and Pax7 positive fibers. We also observed larger relative gains in muscle size (wet weight and fiber area), but not force, during the 3-wk reambulation period in hindlimb muscles overexpressing IGF-I compared with contralateral control legs. Changes in IGFBP-5 mRNA expression during cast immobilization and reambulation paralleled those of IGF-I, whereas IGFBP-3 expression changed inversely to IGFBP-5.

Hexadecanoic Acid from Buzhong Yiqi Decoction Induced Proliferation of Bone Marrow Mesenchymal Stem Cells

Buzhong Yiqi decoction (BYD) is a well-known ancient tonic prescription in traditional Chinese medicine (TCM). The purpose of this study is to identify active components of BYD involved in promoting proliferation of mesenchymal stem cells (MSCs) and to investigate its mechanism. BYD was extracted with petroleum ether, ethanol, and water. Evidence provided by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, bromodeoxyuridine, proliferation cell nuclear antigen immunoreactivity, cell cycle analysis, and gas chromatography-mass spectrometry indicated that hexadecanoic acid (HA) in BYD extracted with petroleum ether is the active compound responsible for increasing proliferation of MSCs. Western blot analysis show that HA significantly increase retinoic acid receptor (RAR) levels of MSCs, but not estrogen receptor, thyroid hormone receptor, vitamin D receptor, glucocorticoid receptor, and peroxisome proliferator-activated receptor. Reverse transcription-polymerase chain reaction revealed that HA significantly increased RAR mRNA levels. Furthermore, the mechanism of HA action depends on RAR pathway and up-regulates expression of mRNA for insulin-like growth factor-I, the target gene of RAR. Our findings have now allowed for a refinement in our understanding of TCM with respect to pharmacological regulation of stem cells and may be useful to stem cell biology and therapy.

Insulin-like growth factor and growth hormone receptor in postpartum lactating beef cows

The objective of this study was to evaluate the plasma concentrations of insulin-like growth factor-I (IGF-I), and the mRNA hepatic expression of IGF-I and of the growth hormone receptors GHR and GHR 1A, in postpartum beef cows. Four Angus and four crossbred (Angus x Nelore) postpartum suckled beef cows were used. Liver and blood samples were collected every 10 days, from calving to 40 days postpartum, for gene expression and for β-hydroxybutyrate and IGF-I assays, respectively. Samples for progesterone assay were collected every other day, from day 10 to 40 postpartum. Three cows ovulated before 40 days postpartum. IGF-I concentration was higher in Angus x Nelore than in Angus cows. There was no difference in the expression of GHR, GHR 1A and IGF-I according to breed or ovulatory status. IGF-I concentrations were higher in crossbred cows, but have not changed according to postpartum ovulatory status. Moreover, changes in postpartum IGF-I concentrations are not associated with changes in liver GHR, GHR 1A and IGF-I mRNA expression in either breed.

Effects of Dietary Lysine on Growth Performance, Serum Concentrations of Insulin-Like Growth Factor-I (IGF-I) and IGF-I mRNA Expression in Growing Rabbits

The effects of dietary lysine on production performance, serum concentrations of metabolites, growth hormone (GH), insulin-like growth factor-I (IGF-I) and IGF-I mRNA expression in growing rabbits were examined. One hundred weaned New Zealand rabbits were allocated to individual cages and randomly offered a diet containing 5.5 (L1), 6.5 (L2), 7.5 (L3), 8.5 (L4), or 9.5 g (L5) lysine per kg diet. The results showed that the average daily gain (ADG) of the rabbits from L3, L4 or L5 was higher than those from L1 or L2 ( P < 0.05). The feed gain ratio (F/G) in the rabbits from L4 or L5 was lower than those from L1 or L2 ( P < 0.05). Dietary lysine did not affect serum concentrations of total protein (TP), glucose, insulin (INS), and growth hormone (GH) ( P > 0.05). The quadratic effects of lysine on the serum urea nitrogen (SUN) concentration was detected ( P = 0.035). Serum IGF-I concentrations had a trend to increase quadratically with the increasing dietary lysine ( P = 0.07). A significant correlation was found between serum IGF-I concentrations ( x, ng mL −1) and ADG ( y, g kg −1): y = −0.017 x 2 + 1.984 x + 20.87 ( R 2 = 0.8982, P = 0.003). The relative abundance of hepatic and muscular IGF-I mRNA tended to increase with increasing dietary lysine levels ( P = 0.053 and 0.082, respectively). Providing the diets mainly consisted of corn, wheat bran and peanut vine, the most appropriate dietary lysine level for growing meat rabbits from weaning to 70 d old was found to be 8.5 g kg −1, and IGF-I may be an important factor controlling growth of weaned rabbits.

Suppressor of Cytokine Signaling-2 Gene Disruption Promotes ApcMin/+ Tumorigenesis and Activator Protein-1 Activation

Epigenetic in vitro and in vivo studies suggest that suppressor of cytokine signaling-2 (SOCS2) may normally limit tumorigenesis in the intestine; however, this theory has not been directly tested. We hypothesized that SOCS2 deficiency promotes spontaneous intestinal tumorigenesis in Apc(Min/+) mice. Therefore, we quantified tumor number, size, and load in the small intestine and colon using SOCS2(+/+)/Apc(Min/+), SOCS2(+/-)/Apc(Min/+), and SOCS2(-/-)/Apc(Min/+) mice and assayed hematocrit as an indirect marker of disease severity. Biochemical and histological assays were used to assess mechanisms. Heterozygous and homozygous disruption of SOCS2 alleles promoted 166 and 441% increases in tumor load in the small intestine, respectively, accelerated development of colon tumors, and caused severe anemia. SOCS2 deletion promoted significant increases in intestinal insulin-like growth factor-I mRNA but did not affect plasma insulin-like growth factor-I. Western blots and immunohistochemical analysis demonstrated that tumor and nontumor intestinal tissue of SOCS2(-/-)/Apc(Min/+) mice had increased serine 727 phosphorylation of signal transducer and activator of transcription 3 compared with SOCS2(+/+)/Apc(Min/+) mice. Moreover, electromobility shift assays showed that SOCS2 deletion did not alter signal transducer and activator of transcription 3 DNA binding. However, tumors and small intestine from SOCS2(-/-)/Apc(Min/+) showed dramatic increases in activator protein-1 (AP-1) DNA binding, and SOCS2 overexpression in vitro reduced levels of AP-1. These studies indicate that SOCS2 deletion promotes the spontaneous development of intestinal tumors driven by mutations in the adenomatous polyposis coli/beta-catenin pathway and activates AP-1. Therefore, reduced expression or epigenetic silencing of SOCS2 may serve as a useful biomarker for colorectal cancer risk.

Effects of Topical Application of α-D-Glucosylglycerol on Dermal Levels of Insulin-Like Growth Factor-I in Mice and on Facial Skin Elasticity in Humans

Sensory neurons release calcitonin-gene related peptide (CGRP) on stimulation. We have reported that topical application of capsaicin increases facial skin elasticity by increasing the production of dermal insulin-like growth factor-I (IGF-I) through stimulation of sensory neurons in mice and humans. In this study, we examined whether topical application of alpha-D-glucosylglycerol (GG), a compound found in Japanese traditional brewed foods such as sake (Japanese rice wine), increases the dermal production of IGF-I in mice and increases the facial skin elasticity in females. GG increased CGRP release and cAMP levels in dorsal root ganglion (DRG) neurons isolated from wild-type mice. Pretreatment with capsazepine, an inhibitor of vanilloid receptor-1 activation, and with KT5720, an inhibitor of protein kinase A, reversed GG-induced increases in CGRP release from DRG neurons. Topical application of GG increased dermal levels of IGF-I, IGF-I mRNA, and collagen in wild-type mice, but not in CGRP-knockout mice. Topical application of GG increased cheek-skin elasticity in 13 female volunteers. These observations strongly suggest that GG increases the production of IGF-I in the skin through sensory neuron stimulation, thereby increasing skin elasticity.

Growth hormone stimulates the collagen synthesis in human tendon and skeletal muscle without affecting myofibrillar protein synthesis

In skeletal muscle and tendon the extracellular matrix confers important tensile properties and is crucially important for tissue regeneration after injury. Musculoskeletal tissue adaptation is influenced by mechanical loading, which modulates the availability of growth factors, including growth hormone (GH) and insulin-like growth factor-I (IGF-I), which may be of key importance. To test the hypothesis that GH promotes matrix collagen synthesis in musculotendinous tissue, we investigated the effects of 14 day administration of 33-50 microg kg(-1) day(-1) recombinant human GH (rhGH) in healthy young individuals. rhGH administration caused an increase in serum GH, serum IGF-I, and IGF-I mRNA expression in tendon and muscle. Tendon collagen I mRNA expression and tendon collagen protein synthesis increased by 3.9-fold and 1.3-fold, respectively (P < 0.01 and P = 0.02), and muscle collagen I mRNA expression and muscle collagen protein synthesis increased by 2.3-fold and 5.8-fold, respectively (P < 0.01 and P = 0.06). Myofibrillar protein synthesis was unaffected by elevation of GH and IGF-I. Moderate exercise did not enhance the effects of GH manipulation. Thus, increased GH availability stimulates matrix collagen synthesis in skeletal muscle and tendon, but without any effect upon myofibrillar protein synthesis. The results suggest that GH is more important in strengthening the matrix tissue than for muscle cell hypertrophy in adult human musculotendinous tissue.

Insulin-like growth factor-I mRNA and peptide are distinctly confined to subtypes of macrophages, antigen-presenting cells, lymphocytes and HEV cells in non-neoplastic human lymph node

Event Abstract Back to Event Insulin-like growth factor-I mRNA and peptide are distinctly confined to subtypes of macrophages, antigen-presenting cells, lymphocytes and HEV cells in non-neoplastic human lymph node Elisabeth Eppler1*, Dominique Oberlin1 and Christian Fellbaum2 1 University of Zürich, Institute of Anatomy, Switzerland 2 Hegau-Klinikum, Institute of Pathology, Germany IGF-I is a potent hormone that stimulates growth and differentiation and inhibits apoptosis in numerous tissues. Preliminary evidence suggests that IGF-I exerts differentiating, mitogenic and restoring activities also in the immune system. The present study investigates the cellular sites of IGF-I mRNA and peptide on archival human lymph node samples by routine staining, in situ hybridisation with an IGF-I probe, and immunohistochemistry with antisera specific for human IGF-I and CD3 (T-lymphocytes), CD20 (B-lymphocytes), CD68 (macrophages), CD21 (follicular dendritic cells, DC), S100 (interdigitating DC) and podoplanin (fibroblastic reticular cells). Numerous cells within the B- and T-cell compartments showed IGF¬I gene and peptide expression the majority of which was identified as macrophages. Solitary follicular DC exhibited IGF-I mRNA and peptide. B-lymphocytes did not contain IGF-I immunoreactive material, while few T-lymphocytes did. Furthermore, IGF-I mRNA and peptide-expressing cells were identified as high endothelial venule (HEV) cells. From this we conclude that the main task of IGF-I in human non-neoplastic lymph node may be autocrine and paracrine regulation of differentiation, stimulation and survival of lymphocytes, antigen-presenting cells and macrophages and differentiation and maintenance of HEV cells, and that the role for IGF-I in formation and sustaining of lymph node structures is more important than thought so far. Keywords: comparative endocrinology Conference: 25th Conference of the European Comparative Endocrinologists, Pécs, Hungary, 31 Aug - 4 Sep, 2010. Presentation Type: Conference Presentation Topic: Comparative endocrinology Citation: Eppler E, Oberlin D and Fellbaum C (2010). Insulin-like growth factor-I mRNA and peptide are distinctly confined to subtypes of macrophages, antigen-presenting cells, lymphocytes and HEV cells in non-neoplastic human lymph node. Front. Endocrinol. Conference Abstract: 25th Conference of the European Comparative Endocrinologists. doi: 10.3389/conf.fendo.2010.01.00008 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 26 Aug 2010; Published Online: 29 Aug 2010. * Correspondence: Dr. Elisabeth Eppler, University of Zürich, Institute of Anatomy, Zürich, Switzerland, elisabeth.eppler@ana.unibe.ch Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Elisabeth Eppler Dominique Oberlin Christian Fellbaum Google Elisabeth Eppler Dominique Oberlin Christian Fellbaum Google Scholar Elisabeth Eppler Dominique Oberlin Christian Fellbaum PubMed Elisabeth Eppler Dominique Oberlin Christian Fellbaum Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Cilostazol improves cognitive function in mice by increasing the production of insulin-like growth factor-I in the hippocampus

Insulin-like growth factor I (IGF-I) exerts beneficial effects on cognitive function by inducing angiogenesis and neurogenesis in the hippocampus. We demonstrated that stimulation of sensory neurons in the gastrointestinal tract increased IGF-I production in the hippocampus, and thereby improved cognitive function in mice. Since cAMP plays a critical role in stimulation of sensory neurons, the type III phosphodiesterase (PDE3) inhibitor cilostazol might increase IGF-I production in the hippocampus by stimulating sensory neurons and thus improve cognitive function in mice. We tested this hypothesis in the present study. Cilostazol increased the release of calcitonin gene-related peptide (CGRP) and levels of cAMP in dorsal root ganglion (DRG) neurons isolated from wild-type (WT) mice. Tissue levels of cAMP in the DRG and hippocampus and those of CGRP, IGF-I, and IGF-I mRNA in the hippocampus were increased after 4-week oral administration of cilostazol to WT mice. Levels of expression of c-fos in the spinal dorsal horns, parabrachial nuclei, the solitary tract nucleus, and the hippocampus were also increased in these animals. Significant enhancement of angiogenesis and neurogenesis was observed in the dentate gyrus of the hippocampus after cilostazol administration in WT mice. Significant improvement of spatial learning was also observed in WT mice administered cilostazol. However, none of these effects in WT mice were observed in CGRP-knockout mice. These observations suggest that cilostazol may improve cognitive function in mice by increasing the hippocampal production of IGF-I through stimulation of sensory neurons.

Coordinated increase in skeletal muscle fiber area and expression of IGF-I with resistance exercise in elderly post-operative patients

Hypertrophy of developing skeletal muscle involves stimulation by insulin-like growth factor-I (IGF-I), however, the role of IGF-I in adult muscle is less clarified. In the present study, the mRNA splice variants of IGF-I (IGF-IEa and MGF) and the changes in muscle fiber cross sectional area after 12 weeks of training were studied in elderly post-operative patients. About 28 subjects, 14 men and 14 women (age 69, range 60–86 years) were randomized to unilateral resistance training (RT: 3/week), electrical stimulation (ES: 1 h/day) or functional exercises (FE: 1 h/day). The non-operated-side served as a within subject control. Muscle biopsies were obtained from the vastus lateralis of both limbs at +2d post-operative (baseline), at 5 weeks and 12 weeks post-surgery to analyze for changes in type 1 and type 2 muscle fiber area. Changes in expression levels of IGF-I mRNA isoforms were determined using real-time RT-PCR, normalized to the ribosomal protein large protein 0 (RPLP0) mRNA and presented relative to the control-side. At baseline there was no difference between the three groups in muscle fiber area or resting levels of IGF-IEa and MGF. RT resulted in a significant increase in muscle fiber area of type 1 (+17%, p < 0.05) and type 2 (+36%, p < 0.05) parallel to an increase in the expression of IGF-IEa and MGF, in contrast to ES and FE. The present study demonstrates that resistance training initiated in the acute post-operative phase is highly effective in increasing mean fiber area and in addition induces marked increases in the expression of IGF-I splice variants, supporting the idea that IGF-I is involved in regulating muscle hypertrophy.

Effect of the herbicide pendimethalin on rat uterine weight and gene expression and in silico receptor binding analysis

The endocrine disrupting potential of the herbicide pendimethalin was investigated in vivo on the uterotrophic response and on the expression of estrogen-regulated genes examined by quantitative real-time RT PCR. Receptor binding characteristics of pendimethalin were analyzed by an in silico method. Pendimethalin (150, 225, 300 and 600 mg/kg/day) was administered by oral gavage to immature female rats for 3 days, with ethinylestradiol (0.001 mg/kg/day) as positive control. Pendimethalin caused a small but significant increase in absolute uterine weight at and above 300 mg/kg/day and in relative uterine weight at 600 mg/kg/day. Estrogen receptor (ER)-alpha mRNA levels were not affected, whereas ER-beta mRNA was up-regulated at the highest dose. Progesterone receptor mRNA level was not significantly changed, while insulin-like growth factor-I mRNA was reduced, significantly at 225 mg/kg/day to 65% of control. Androgen receptor (AR) mRNA showed a marked down-regulation at doses of 225 mg/kg/day and above. The expression pattern differed from that of ethinylestradiol. In silico analysis revealed potential binding of pendimethalin to ER-beta and AR, but virtually no binding to ER-alpha. These data demonstrate that pendimethalin exhibits estrogenic activity also in vivo. However, its uterotrophic effect, which is an ER-alpha-mediated response, is very small, and it appears that in vivo actions should rather be sought in ER-beta-regulated functions.

Hepatic gene expression in multiparous Holstein cows treated with bovine somatotropin and fed n-3 fatty acids in early lactation

Multiparous cows were fed supplemental dietary fat and treated with bST to assess effects of n-3 fatty acid supply, bovine somatotropin (bST), and stage of lactation on hepatic gene expression. Cows were blocked by expected calving date and previous milk yield and assigned randomly to treatment. Supplemental dietary fat was provided from calving as either whole high-oil sunflower seeds (SS; 10% of dietary dry matter; n-6/n-3 ratio of 4.6) as a source of linoleic acid or a mixture of Alifet-High Energy and Alifet-Repro (AF; 3.5 and 1.5% of dietary dry matter, respectively; n-6/n-3 ratio of 2.6) as a source of protected n-3 fatty acids. Cows were treated with 0 (SSN, AFN) or 500 (SSY, AFY) mg of bST every 10 d from 12 to 70 d in milk (DIM) and at 14-d intervals thereafter. Liver biopsies were collected on −12, 10, 24, and 136 DIM for gene expression analysis. Growth hormone receptor (GHR), insulin-like growth factor-I (IGF-I), IGF-binding protein-3 (IGFBP3), hepatic nuclear factor 4α (HNF4α), fibroblast growth factor-21 (FGF-21), and peroxisome proliferator-activated receptor α (PPARα) were the target genes and hypoxanthine phosphoribosyltransferase (HPRT) was used as an endogenous control gene. Expression was measured by quantitative real-time reverse transcription-PCR analyses of 4 samples from each of 32 cows (8 complete blocks). Amounts of hepatic HPRT mRNA were not affected by bST or diet but were increased by approximately 3.8% in early lactation (3.42, 3.52, 3.54, and 3.41×104 message copies for −12, 10, 24, and 136 DIM, respectively). This small change had little detectable impact on the ability of HPRT to serve as an internal control gene. Amounts of hepatic GHR, IGF-I, and IGFBP3 mRNA were reduced by 1.5 to 2-fold after calving. Expression of GHR and IGF-I increased and IGFBP3 tended to increase within 12 d (by 24 DIM) of bST administration. These effects of bST persisted through 136 DIM. Hepatic HNF4α mRNA was not altered by DIM or any of the treatments. Abundance of PPARα mRNA was unchanged through 24 DIM but increased by 136 DIM. There was a trend for an interaction of bST, diet, and DIM on PPARα mRNA abundance from 24 to 136 DIM because the amount of PPARα mRNA increased in SSN, SSY, and AFN cows but was not altered in AFY cows. The amount of FGF-21 mRNA increased markedly in early lactation but, like HNF4α mRNA, was not affected by bST, diet, or their interactions. These results indicate 1) that bST induced increases in hepatic expression of GHR, IGF-I, and IGFBP3 when cows were in negative energy balance in early lactation, 2) there was no effect of reduced dietary n-6/n-3 content on hepatic gene expression, and 3) there was support for a potential homeorhetic role of hepatic FGF-21 via uncoupling the somatotropin-IGF-axis in early lactation.

Nanoparticle-rich diesel exhaust may disrupt testosterone biosynthesis and metabolism via growth hormone

We previously reported that exposure to low (22.5±0.2nm in diameter, 15.4±1.0μg/m3 in mass weight, 2.27×105/cm3 in mean number concentration), and medium (26.1±0.5nm, 36.4±1.2μg/m3, 5.11×105/cm3) concentrations of nanoparticle-rich diesel exhaust (NR-DE) for 1 and 2 months (5h/day, 5 days/week) significantly increased plasma testosterone in male Fischer 344 rats, whereas exposure to a high concentration (27.1±0.5nm, 168.8±2.7μg/m3, 1.36×106/cm3) did not. The present study attempts to clarify the mechanism of this elevation. Low and medium exposures to NR-DE for 1 and 2 months significantly increased steroidogenic acute regulatory protein (StAR)- and cytochrome P450 side-chain cleavage (P450scc)-mRNA and their protein expressions in the testis of rats, in which the elevation pattern was very similar to that of plasma testosterone levels. Interestingly, both exposure levels for 1 month significantly increased growth hormone (GH) receptor expression in the testis, and low exposure also increased testicular insulin-like growth factor I-mRNA levels and hepatic microsomal cytochrome P450 2C11-mRNA and their protein levels in rats. These two factors are thought to be related to growth hormone secretion. Disruption of testosterone biosynthesis by NR-DE exposure may be a mode of action for reproductive toxicity, which may, in part, be regulated by increasing StAR and P450scc expressions via GH signalling.

Changes in the plasma levels of insulin-like growth factor-I from the onset of spawning migration through upstream migration in chum salmon

An increase in activity of the pituitary–gonadal axis (PG-axis) and gonadal development are essential for the onset of spawning migration of chum salmon from the Bering Sea. In the Bering Sea, fish with larger body sizes initiated gonadal development and commenced spawning migration to the natal river by the end of summer. We thus hypothesized that insulin-like growth factor-I (IGF-I), a somatotropic signal that interacts with the PG-axis, can be one of such factors responsible for the onset of migration, and examined changes in plasma levels and hepatic expression of IGF-I gene in oceanic and homing chum salmon in 2001–2003. The plasma IGF-I levels and corresponding body sizes in maturing adults, which had developing gonads, were significantly higher than those in immature fish in all years examined. Such increase in the plasma IGF-I levels in maturing fish was observed even in the Gulf of Alaska during February 2006, while coincident increase was not observed in the hepatic amounts of IGF-I mRNA. In autumn, the plasma IGF-I levels in homing adults decreased during upstream migration in the Ishikari River-Ishikari bay water system in Hokkaido, Japan. In conclusion, the plasma IGF-I levels increased with gonadal development when chum salmon migrated from the winter Gulf of Alaska to the summer Bering Sea. Circulating IGF-I may interact with the PG-axis and promote gonadal development that is inseparable from the onset of spawning migration. Circulating IGF-I levels were thereafter lowered in accordance with final maturation during upstream migration in the breeding season.

Alterations of growth plate and abnormal insulin-like growth factor I metabolism in growth-retarded hypokalemic rats: effect of growth hormone treatment

Hypokalemic tubular disorders may lead to growth retardation which is resistant to growth hormone (GH) treatment. The mechanism of these alterations is unknown. Weaning female rats were grouped (n = 10) in control, potassium-depleted (KD), KD treated with intraperitoneal GH at 3.3 mg x kg(-1) x day(-1) during the last week (KDGH), and control pair-fed with KD (CPF). After 2 wk, KD rats were growth retarded compared with CPF rats, the osseous front advance (+/-SD) being 67.07 +/- 10.44 and 81.56 +/- 12.70 microm/day, respectively. GH treatment did not accelerate growth rate. The tibial growth plate of KD rats had marked morphological alterations: lower heights of growth cartilage (228.26 +/- 23.58 microm), hypertrophic zone (123.68 +/- 13.49 microm), and terminal chondrocytes (20.8 +/- 2.39 microm) than normokalemic CPF (264.21 +/- 21.77, 153.18 +/- 15.80, and 24.21 +/- 5.86 microm). GH administration normalized these changes except for the distal chondrocyte height. Quantitative PCR of insulin-like growth factor I (IGF-I), IGF-I receptor, and GH receptor genes in KD growth plates showed downregulation of IGF-I and upregulation of IGF-I receptor mRNAs, without changes in their distribution as analyzed by immunohistochemistry and in situ hybridization. GH did not further modify IGF-I mRNA expression. KD rats had normal hepatic IGF-I mRNA levels and low serum IGF-I values. GH increased liver IGF-I mRNA, but circulating IGF-I levels remained reduced. This study discloses the structural and molecular alterations induced by potassium depletion on the growth plate and shows that the lack of response to GH administration is associated with persistence of the disturbed process of chondrocyte hypertrophy and depressed mRNA expression of local IGF-I in the growth plate.

Influence of the photoperiod on growth rate and insulin‐like growth factor‐I gene expression in Nile tilapia Oreochromis niloticus

The effects of the duration of the light phase photoperiod (8 h light or 16 h light) on the growth and hepatic insulin-like growth factor-I (IGF-I) gene expression in Nile tilapia Oreochromis niloticus were evaluated. There was a slight but not significant tendency for fish in the long light phase group (L(P)) to display elevated specific growth rate (G) both in mass (M) and standard length (L(S)) compared with that in the short light phase group (S(P);P = 0.057 for G(M);P = 0.055 for G(L)). Significantly, higher food conversion efficiency was observed in the L(P) than in the S(P). There were significant positive correlations between IGF-I concentrations and G, both in M and L(S). A significantly negative correlation was observed between IGF-I mRNA level and eye colour pattern. The lack of significant differences in G and hepatic IGF-I gene expression, despite the significant difference in feed conversion efficiency, may be related partly to the development of different levels of social interactions in the different groups within a photoperiod regime leading to increased variation of results within each group. These findings suggest that hepatic IGF-I gene expression has potential utility as a growth rate indicator for this species of fish and social status, as quantified by eye colour pattern, appears to be a much stronger determinant of growth rate and IGF-I transcript level than does light phase photoperiod length.