Myostatin regulates pituitary development and hepatic IGF1

Circulating myostatin-attenuating agents are being developed to treat muscle-wasting disease despite their potential to produce serious off-target effects, as myostatin/activin receptors are widely distributed among many nonmuscle tissues. Our studies suggest that the myokine not only inhibits striated muscle growth but also regulates pituitary development and growth hormone (GH) action in the liver. Using a novel myostatin-null label-retaining model (Jekyll mice), we determined that the heterogeneous pool of pituitary stem, transit-amplifying, and progenitor cells in Jekyll mice depletes more rapidly after birth than the pool in wild-type mice. This correlated with increased levels of GH, prolactin, and the cells that secrete these hormones, somatotropes and lactotropes, respectively, in Jekyll pituitaries. Recombinant myostatin also stimulated GH release and gene expression in pituitary cell cultures although inhibiting prolactin release. In primary hepatocytes, recombinant myostatin blocked GH-stimulated expression of two key mediators of growth, insulin-like growth factor (IGF)1 and the acid labile subunit and increased expression of an inhibitor, IGF-binding protein-1. The significance of these findings was demonstrated by smaller muscle fiber size in a model lacking myostatin and liver IGF1 expression (LID-o-Mighty mice) compared with that in myostatin-null (Mighty) mice. These data together suggest that myostatin may regulate pituitary development and function and that its inhibitory actions in muscle may be partly mediated by attenuating GH action in the liver. They also suggest that circulating pharmacological inhibitors of myostatin could produce unintended consequences in these and possibly other tissues.

The Potent Humanin Analogue (HNG) Protects Germ Cells and Leucocytes While Enhancing Chemotherapy-Induced Suppression of Cancer Metastases in Male Mice

Humanin is a peptide that is cytoprotective against stresses in many cell types. We investigated whether a potent humanin analogue S14G-humanin (HNG) would protect against chemotherapy-induced damage to normal cells without interfering with the chemotherapy-induced suppression of cancer cells. Young adult male mice were inoculated iv with murine melanoma cells. After 1 week, cancer-bearing mice were randomized to receive either: no treatment, daily ip injection of HNG, a single ip injection of cyclophosphamide (CP), or CP+HNG and killed at the end of 3 weeks. HNG rescued the CP-induced suppression of leucocytes and protected germ cell from CP-induced apoptosis. Lung metastases were suppressed by HNG or CP alone, and further suppressed by CP+HNG treatment. Plasma IGF-1 levels were suppressed by HNG with or without CP treatment. To investigate whether HNG maintains its protective effects on spermatogonial stem cells, sperm output, and peripheral leucocytes after repeated doses of CP, normal adult male mice received: no treatment, daily sc injection of HNG, 6 ip injections of CP at 5-day intervals, and the same regimens of CP+HNG and killed at the end of 4 weeks of treatment. Cauda epididymal sperm counts were elevated by HNG and suppressed by CP. HNG rescued the CP-induced suppression of spermatogonial stem cells, sperm count and peripheral leucocytes. We conclude that HNG 1) protects CP-induced loss of male germ cells and leucocytes, 2) enhances CP-induced suppression of cancer metastases, and 3) acts as a caloric-restriction mimetic by suppressing IGF-1 levels. Our findings suggest that humanin analogues may be promising adjuvants to chemotherapy.

Effects of tibolone and its metabolites on prolactin and insulin-like growth factor binding protein-1 expression in human endometrial stromal cells

The effects of the postmenopausal replacement steroid tibolone and its 3α-, 3β-OH and Δ-4 tibolone metabolites were evaluated on progesterone receptor-mediated classic decidualization markers insulin-like growth factor binding protein-1 (IGFBP-1) and prolactin expression in human endometrial stromal cells (HESCs). Supernatants of conditioned medium or erxtracted RNA from experimental cell incubations of confluent HESCs were subjected to ELISAs, Western blot analysis and RT/PCR, and results were statisically assesed. Over 21 days, specific ELISAs observed linear increases in secreted IGFBP-1 and prolactin levels elicited by tibolone and its metabolites. Cultured HESCs were refractory to E2 and dexamethasone, whereas tibolone and each metabolite exceeded medroxyprogesterone acetate in significantly elevating IGFBP-1 and prolactin output. Anti-progestins eliminated IGFBP-1 and prolactin induction by tibolone and its metabolites. Immunoblotting and RT/PCR confirmed ELISA results. These observations of IGFBP-1 and prolactin expression: (a) indicate the relevance of cultured HESCs in evaluating the chronic effects of tibolone administration to women; (b) are consistent with PR-mediated endometrial atrophy and protection against endometrial bleeding despite the persistence of circulating ER-binding, but not PR-binding metabolites following tibolone administration to women.

GLP-1 infusion reduces IGFBP-1 serum level in humans

OBJECTIVE

Glucagon-like peptide-1 (GLP-1) and the insulin-like growth factor (IGF) system are important factors in metabolic regulation and cellular growth. Interactions between the systems exist but these are vaguely explored and only in vitro, where GLP-1 has been reported to stimulate IGF-binding protein 1 (IGFBP-1). This study, therefore, aimed to elucidate the effects of GLP-1 on IGF-I and the IGFBPs, which regulate IGF-I bioactivity.

DESIGN

We investigated the effects of a 2-hour intravenous GLP-1 infusion on the IGF system in 12 overnight fasted healthy humans, using a randomized, double-blinded, cross-over study design. Serum samples were assessed for immunoreactive levels of IGF-I, IGFBP-1 and -2 as well as for bioactive IGF-I, which was determined by a cell-based IGF-I kinase receptor activation assay.

RESULTS

GLP-1 infusion markedly increased insulin levels (p<0.0001), reduced IGFBP-1 levels (p=0.02), and tended to increase IGF-I bioactivity (p=0.06). There were no significant changes in IGFBP-2 or immunoreactive IGF-I levels.

CONCLUSION

In this short-term study, GLP-1 reduced IGFBP-1 levels in vivo and tended to increase IGF-I bioactivity. The IGFBP-1 outcome is opposite to the in vitro situation, hereby demonstrating that in vivo the ability of GLP-1 to stimulate insulin and hereby suppress IGFBP-1 outweighs any direct stimulatory effects of GLP-1 on IGFBP-1.

[Effects of gibberellins on early development and IGF-1 expression in female rats]

OBJECTIVE

To explore the effects of plant growth regulator gibberellin on early development and IGF-1 expression in female rats.

METHODS

Forty weaned female SD rats were randomly divided into four groups and fed with basic diet. Gibberellin was administered intragastrically at the levels of 0, 2.0, 100.0 and 200.0 mg/kg respectively for 15 days. Body weight and body length were measured weekly and the time of vaginal opening was observed every day. Liver, uterus and ovary were dissected after exposure for 15 days. Total RNA of liver was extracted and the expression of IGF-1 and IGFBP-1 mRNA was detected by RT-PCR.

RESULTS

Compared with the control group, no significant differences of body weight, body length, vaginal opening time, as well as the organ coefficients of liver, uterus and ovary were observed in gibberellin-treated groups. There was no significant change on the expressions of IGF-1 and IGFBP-1 in the liver of gibberellin-treated groups, although the expression of IGFBP-1 was more than IGF-1 in a few samples. Organ coefficient of liver in high dose group was significantly lower than that in the control group (P < 0.05).

CONCLUSION

Gibberellin does not cause abnormal change on growth and development as well as the expression of IGF-1 and IGFBP-1 in liver of female SD rats, but at the level of 200.0 mg/kg gibberellin may induce damages in liver.

Oral 17beta-estradiol and sequential progesterone in menopause: effects on insulin-like growth factors and their binding proteins

OBJECTIVE

We evaluated the acute effects of low-dose oral estradiol and sequential progesterone on the insulin-like growth factor (IGF)/growth hormone (GH) axis, IGF-binding proteins (IGFBPs) 1 and 3, and plasma levels of sex hormone-binding globulin (SHBG) in postmenopausal subjects.

STUDY DESIGN

Thirty healthy normal-weight women (mean age: 54.2 +/- 5.7 years) spontaneously postmenopausal for at least 6 months were enrolled. None had used hormone replacement therapy (HRT). Appropriate investigations excluded renal, glucose, lipid and coagulation abnormalities. Breast X-ray and endometrial ultrasound examinations excluded organic pathologies. They received oral cyclical HRT for 1 year, based on the administration of oral estradiol (1 mg/day) for 28 consecutive days plus progesterone (200 mg/day) from day 15 to day 28; out of the whole group, 15 subjects received progesterone orally (group A), while in 15 progesterone was administered transvaginally (group B). On the day before treatment (T0), on day 14 (T14) and on day 28 (T28) of the first cycle, plasma levels of estradiol, progesterone, SHBG, GH, IGF-I and -II, IGFBP-1 and -3, insulin and C-peptide were assayed in all patients. The same parameters were evaluated at T14 and T28 during the 12th month of treatment.

RESULTS

At T14, we observed significant increases in the levels of estradiol (from 20 +/- 16 to 115 +/- 71 pg/ml, p < 0.001), SHBG (from 132 +/- 42 to 182 +/- 55 nmol/l, p < 0.001) and IGFBP-1 (from 92 +/- 57 to 127 +/- 87 ng/ml, p < 0.004), while the level of IGF-I decreased (from 197 +/- 138 to 129 +/- 85 ng/ml, p < 0.003). At T28, progesterone levels were significantly higher in the women receiving it orally than transvaginally (8.4 +/- 6.1 vs. 3.7 +/- 3.2 ng/ml, p < 0.025). However, while oral progesterone did not affect the estrogen-induced variations, transvaginal progesterone abrogated the increase in the levels of IGFBP-1. The levels of IGF-II, IGFBP-3, GH, glucose, C-peptide and insulin did not change at any time. At 1 year, the values maintained the same trends. The estrogen-induced variations of SHBG were correlated directly with those of estradiol (r = 0.48) and inversely with those of IGF-I (r = -0.424).

CONCLUSIONS

Low-dose oral estradiol reduces plasma levels of IGF-I and increases IGFBP-1 and SHBG concentrations, while GH is unchanged. These effects, significant and immediate, lead us to hypothesize a direct action of estradiol on hepatocytes.

Anti-TNF antibody treatment improves glucocorticoid induced insulin-like growth factor 1 (IGF1) resistance without influencing myoglobin and IGF1 binding proteins 1 and 3

BACKGROUND

Insulin-like growth factor 1 (IGF1) is an important determinant of muscle mass because it promotes growth and suppresses protein degradation. IGF1 is decreased in rheumatoid arthritis and juvenile idiopathic arthritis because its synthesis is inhibited by inflammation. In parallel, glucocorticoids induce IGF1 resistance and add to muscle degradation.

OBJECTIVE

To investigate the influence of anti-tumour necrosis factor antibody treatment (anti-TNF) with adalimumab on levels of myoglobin (degradation marker) and IGF1 in patients with rheumatoid arthritis with and without prednisolone treatment.

METHODS

Subcutaneous adalimumab was given to 32 patients with longstanding rheumatoid arthritis (16 with and 16 without prednisolone) in a longitudinal study. IGF1, IGF1 binding protein 1 (IGFBP-1), IGFBP-3, and myoglobin were measured by enzyme linked immunosorbent assay.

RESULTS

Rheumatoid patients had normal serum myoglobin. Patients on prednisolone had higher myoglobin than patients not receiving prednisolone, indicating increased muscle degradation. On treatment with anti-TNF, myoglobin levels did not change in either patient group. Serum IGF1 was increased in patients with v without prednisolone, indicating IGF1 resistance (mean (SEM): 221 (23) v 122 (14) microg/l, p<0.001). Adalimumab treatment decreased the raised IGF1 levels in patients with prednisolone, so that after 12 weeks of treatment they reached the level of patients without prednisolone. Serum IGFBP-1 and IGFBP-3 did not differ in the two groups, and anti-TNF did not change these concentrations.

CONCLUSIONS

Anti-TNF antibody treatment over 12 weeks improved glucocorticoid induced IGF1 resistance without influencing myoglobin and IGF1 binding proteins. Thus, in rheumatoid patients on glucocorticoids with generally decreased muscle mass anti-TNF treatment with adalimumab has favourable effects.

The effect of clozapine on factors controlling glucose homeostasis

BACKGROUND

This prospective study examines the effect of clozapine on factors determining glucose homeostasis.

METHOD

The sample consisted of all patients meeting DSM-IV criteria for schizophrenia who commenced clozapine treatment within the South London and Maudsley hospitals during 1 year (2000-2001). Growth hormone (GH), insulin-like growth factor-1 (IGF-1), and IGF binding protein-1 (IGFBP-1) were measured in 19 patients (10 female; mean age = 31.1 years [SD = 5.8]; 9 black British/African, 10 white British) before and after a mean of 2.5 (SD = 0.9) months of clozapine treatment.

RESULTS

Baseline IGFBP-1 was low. IGFBP-1, GH, and IGF-1 were not significantly changed by clozapine treatment.

CONCLUSIONS

Clozapine does not alter GH, IGF-1, or IGFBP-1 within 3 months of commencing treatment, indicating that alteration in glucose tolerance associated with clozapine treatment involves other mechanisms yet to be elucidated. Baseline abnormalities in IGFBP-1 indicate a preexisting susceptibility to glucoregulatory dysfunction.

High levels of 150-kDa insulin-like growth factor binding protein three ternary complex in patients with acromegaly and the effect of pegvisomant-induced serum IGF-I normalization

OBJECTIVE

To assess the effect of pegvisomant-induced serum insulin-like growth factor 1 (IGF-1) normalization on IGF binding proteins 1, 2, 3 (IGFBP-1, IGFBP-2 and IGFBP-3), total, non-bound (45 kDa) and 150-kDa ternary complex-associated IGFBP-3, and in vivo IGFBP-3 proteolysis in patients with active acromegaly.

DESIGN

The above parameters were measured in 16 patients (median age 57 (range 27-78)) with active acromegaly (serum IGF-I at least 30% above the upper limit of an age-related reference range after washout) in a paired manner on samples obtained after washout and the first occurrence of serum IGF-I normalization during pegvisomant therapy (median dose 15 mg/day (10-40 mg)).

RESULTS

Total IGFBP-3 and 150-kDa ternary complex-associated IGFBP-3 were significantly elevated in patients at baseline compared to controls ((mean+/-SEM) 4345+/-194 vs. 3456+/-159 microg/L, P<0.01 and 3908+/-160 va. 3042+/-149 microg/L, P<0.01, respectively), but no significant difference in 45-kDa IGFBP-3 or in vivo IGFBP-3 proteolysis was observed. Serum IGF-I normalization (699+/-76 to 242+/-28 microg/L, P<0.0001) was associated with a fall in total IGFBP-3 (4345+/-194 to 3283+/-160 microg/L, P<0.001) due to a reduction in 150-kDa ternary complex-associated IGFBP-3 (3908+/-160 to 3008+/-140 microg/L, P<0.0001). 45 kDa IGFBP-3 and in vivo IGFBP-3 proteolysis were unaffected by GH receptor blockade (326+/-13 to 330+/-18 microg/L, P=0.86; 30+/-3.5 to 30+/-3.9%, P=0.75, respectively).

CONCLUSIONS

GH receptor blockade in patients with acromegaly lowers IGF-I and 150-kDa IGFBP-3 ternary complex formation. 50 kDa ternary complex formation (not in vivo IGFBP-3 proteolysis) is GH dependent and measurement of 150-kDa ternary complex-associated IGFBP-3 may provide useful information regarding treatment efficacy in patients with acromegaly.

Modification of serum IGF-I, IGFBPs and SHBG levels by different HRT regimens

During the menopause, levels of SHBG, IGF-I and IGFBPs are significantly modified by the use of different HRT regimens.

OBJECTIVE

The aim of this study is to evaluate the influence of three different HRT regimens on serum levels of SHBG, IGF-I, IGFBP-1 and IGFBP-3 in postmenopausal women.

METHODS

41 postmenopausal women requesting HRT were enrolled in the study. Subjects were divided in three groups according to the therapy assigned; Group A: estradiol 2 mg/day+cyproterone acetate 1 mg/day in a cyclic sequential regimen; Group B: estradiol hemihydrate 2 mg/day plus norethisterone acetate (NETA) 1 mg/day in a continuous combined regimen; Group C: estradiol hemihydrate 1 mg/day plus NETA 0.5 mg/day in a continuous combined regimen. Blood samples were drawn before the start of hormonal treatment and after 6 months of HRT. Levels of SHBG, IGF-I, IGFBP-1 and IGFBP-3 in the serum were measured by means of a specific immunoassay.

RESULTS

In group A, a significant increase of SHBG, no change of IGFBPs and a significant decrease of IGF-I were observed; in group B and in group C, no significant variations for any of the parameters were recorded.

CONCLUSIONS

The association of cyproterone acetate to oral estradiol determines a significant reduction of IGF-I levels and an increase of SHBG; nevertheless, it does not seem to influence the serum levels of the IGF-I binding proteins. The treatment with oral continuous combined estrogens plus androgenic progestins, at low doses, produces minor, not significant, changes in the circulating levels of IGF-I, SHBG and IGFBPs.

[Optimal time for the administration of rhGH in severely burned patients--analysis of the dynamic changes of IGF axis and blood sugar]

OBJECTIVE

To investigate the effects of recombinant human growth hormone (rhGH) on the changes in serum insulin-like growth factor-I (IGF-I), IGF binding protein 3 (IGFBP-3) and blood sugar in severely burned patients, so as to validate the optimal time of rhGH administration.

METHODS

Forty severely burned patients were enrolled in the study and were randomly divided into control (C), treatment 1 (rhGH given from 7 - 9 PBD, T1) and treatment 2 (rhGH from 10 - 14 PBD, T2) groups. The dynamic changes in serum IGF-I, IGFBP-3 and blood sugar on the 1, 3, 5, 7, 10, 14 and 21 PBDs in all 3 groups of burn patients were determined, analyzed and compared with one another.

RESULTS

The serum IGF-I, IGFBP-3 and blood sugar levels in T1 and T2 groups were higher than those in C group after the use of rhGH, especially the IGFBP-3 and blood sugar (P < 0.05). There was no difference of all the indices between T1 and T2 groups.

CONCLUSION

It might be optimal to give rhGH to severely burned patients during 7-9 PBDs.

The effect of mifepristone on the expression of insulin-like growth factor binding protein-1, prolactin and progesterone receptor mRNA and protein during the implantation phase in human endometrium

Insulin-like growth factor binding protein-1 (IGFBP-1) and prolactin are recognized as crucial signals for the initiation and maintainance of decidualization. The purpose of the study was to investigate the effect of mifepristone on the expression of IGFBP-1, prolactin and progesterone receptors (PR) during the implantation phase in human endometrium. Eight fertile women were studied during control and treatment cycles. Treatment with 200 mg of mifepristone was administered on day LH +2. Endometrial samples were collected on day LH +6 to +8. Expression of IGFBP-1, prolactin and PR was identified using immunohistochemistry, and mRNA levels were determined with RT-PCR. In control specimens, IGFBP-1 and prolactin were localized to the cytoplasm of the endometrial glandular and to a lesser extent in stromal cells. In the same samples, PR immunoreactivity was detected in the nucleus of the endometrial stromal cells, and was absent from the glandular cells. After mifepristone treatment, there was a significant increase in the immunostaining and mRNA expression for IGFBP-1 and PR. Prolactin expression increased only slightly after treatment. These results support the view that administration of mifepristone in the early luteal phase does not simply retard endometrial development. Our findings provide further insight into the regulation of IGFBP-1 and prolactin by PR in the human endometrium in vivo.

Lithium chloride inhibits the expression and secretion of insulin-like growth factor-binding protein-1

Insulin-like growth factor-binding protein-1 (IGFBP-1) regulates IGF availability for glucose homeostasis. The IGFBP-1 promoter shares common regulatory response elements with phosphoenol pyruvate carboxykinase (PEPCK), the expression and activity of which is inhibited by lithium chloride, associated with an inhibition of glycogen synthase kinase (GSK)-3 activity, in the rat hepatoma cell line H4-II-E. We therefore determined the effect of lithium chloride on IGFBP-1 expression and secretion in H4-II-E cells. Lithium chloride inhibited IGFBP-1 secretion in a dose response and reversible manner by approx 80% during 5-h and 16-h incubations. An inhibitory effect on IGFBP-1 mRNA expression was observed at 2 h. The inhibitory effect of lithium and insulin were not additive when used alone, but inhibition by lithium occurred when insulin action was blocked by activating AMP-activated protein kinase with 5-aminoimidazole-4-carboxamide-riboside (AICAR). These findings suggest that GSK-3 inhibition, or another pathway activated by lithium, may be involved in a pathway controlling IGFBP-1, inhibiting synthesis when insulin activity is absent or impaired.

IGF status is altered by tamoxifen in patients with breast cancer

AIMS

An increased concentration of insulin-like growth factor 1 (IGF-1) is an independent risk factor for premenopausal breast cancer. Tamoxifen is thought initially to reduce concentrations of IGF-1 and increase concentrations of the IGF binding proteins. The aim of this study was to compare concentrations of IGF-1, IGF binding protein 1 (IGF-BP1), and IGF-BP3 in patients with breast cancer (n = 14) with those seen in control subjects (n = 23) and to assess the effect of tamoxifen on IGF status in these patients.

METHODS

Non-fasting blood samples were collected from patients with breast cancer before surgery and after nine, 18, and 27 months of tamoxifen treatment. The baseline concentrations were compared with those of age and sex matched healthy control subjects.

RESULTS

IGF-1, IGF-BP3, and IGF-BP1 concentrations were not significantly different in cases and controls. Tamoxifen treatment significantly increased IGF-BP1 after 18 and 27 months (baseline: mean, 21.6 ng/ml; SD, 16.6; 18 months: mean, 52.0 ng/ml; SD, 41.8; p = 0.019; 27 months: mean, 40.7 ng/ml; SD, 24.9; p = 0.043) and IGF-BP3 after nine, 18, and 27 months (baseline: mean, 3119 ng/ml; SD, 507; nine months: mean, 3673 ng/ml; SD, 476; p = 0.004; 18 months: mean, 3445 ng/ml; SD, 634; p = 0.034; 27 months: 3409 ng/ml; SD, 501; p = 0.043) when compared with baseline values. IGF-1 was not altered significantly from baseline at any time point. However, the IGF-1 to IGF-BP3 ratio was significantly decreased at both nine and 18 months (baseline: mean, 0.058; SD, 0.014; nine months: mean, 0.039; SD, 0.008; p = 0.033; 18 months: mean, 0.044; SD, 0.012; p = 0.01). This ratio was not significantly different from baseline at 27 months (mean, 0.054; SD, 0.01; p = 0.08).

CONCLUSIONS

Tamoxifen increases IGF-BP3 and IGF-BP1 concentrations. It also decreases the IGF-1 to IGF-BP3 ratio but this effect may be limited after long term use. Longer follow up, with larger numbers of patients, should determine when, and for how long, tamoxifen can reduce circulating IGF-1.

Cyclic changes in serum levels of insulin-like growth factor binding protein-1 in women treated with clomiphene citrate and tamoxifen

In order to investigate the cyclic changes of serum insulin-like growth factor-I (IGF-I), IGF binding protein-1 (IGFBP-1) and IGFBP-3 levels in menstrual cycles treated with or without antiestrogens (clomiphene citrate and tamoxifen), we treated 24 young women having irregular menstrual cycles with either clomiphene citrate (100 mg/day) (n = 12) or tamoxifen (60 mg/day) (n = 12) from the 5th to the 9th day of the menstrual cycle. Without antiestrogens, 12 women with regular menstrual cycles were recruited as controls. There was a preovulatory (day 13) peak of circulating IGFBP-1 in women treated with or without antiestrogens. A significant concomitant increase in serum estradiol was also observed on day 13 of the menstrual cycle in subjects treated with clomiphene citrate and in controls. However, no significant elevation in preovulatory estradiol was detected in women treated with tamoxifen. In clomiphene citrate and control groups, a significant positive correlation was found between circulating IGFBP-1 and estradiol, and between serum levels of IGFBP-1 and inhibin A at the preovulatory stage (on day 13). In contrast, no such association was observed in the tamoxifen group. Unlike cyclic changes in circulating IGFBP-1, serum concentrations of IGF-I and IGFBP-3 remained unchanged throughout the menstrual cycle in all groups. In conclusion, the preovulatory peak of circulating IGFBP-1 can be induced in cycles treated with both clomiphene citrate and tamoxifen. In addition, a significant positive correlation between estradiol, inhibin A and IGFBP-1 at the preovulatory stage indicates that IGFBP-1 may also reflect follicular development and may further be used as an additional indicator to monitor folliculogenesis under clomiphene citrate treatment.

Increased expression of insulin-like growth factor binding protein-1 during induced regression of bovine corpora lutea

Three experiments were conducted to examine gene expression during induced luteal regression in the cow; the initial purpose was the identification of potential embryotoxins. In experiment 1, changes in gene expression in the corpus luteum (CL) were identified by differential display reverse transcription-polymerase chain reaction (DD-PCR) during the first 72 h of luteal regression in cows treated with prostaglandin F(2alpha) (PGF(2alpha)) on Days 4-7 after estrus. Expression of insulin-like growth factor-binding protein-1 (IGFBP-1) was up-regulated, with greatest expression at 24 h (P < 0.05) after treatment with PGF(2alpha) began. In experiment. 2, IGFBP-1 and its mRNA were quantified in CL collected 24 or 48 h after treatment with PGF(2alpha) on Day 4 or 10 after estrus. Because local mechanisms for exchange of hormones between the ovary and uterus are known in ruminants, uterine flushings were assayed for IGFBP-1 to seek evidence of local transfer of luteal IGFBP-1 to the uterus. IGFBP-1 mRNA was increased (P < 0.05) in CL 24 h after treatment when PGF(2alpha) that began on Day 10, and by 48 h after treatment that began on Day 4. Concentrations of IGFBP-1 increased (P < 0.05) in a pattern similar to mRNA, by 24 h on Day 10, and by 48 h on Day 4. Concentrations of IGFBP-1 in uterine flushings did not change on either day. Concentrations of progesterone decreased (P < 0.05) by 8 h after treatment with PGF(2alpha) that began on Day 10, but not until 24 h after treatment that began on Day 4. In experiment 3, cows received either saline or PGF(2alpha) and CL were collected 2 or 10 h after a single treatment, or 2 h after a second treatment that was given 8 h after the first. Expression of IGFBP-1 was increased by 2 h after treatment with PGF(2alpha) on both Days 4 and 10 after estrus. In conclusion, secretion of IGFBP-1 is increased during luteolysis, and may inhibit the steroidogenic effects of insulin-like growth factor-I (IGF-I), but no evidence was found to implicate IGFBP-1 in the embryotoxic effect of regressing CL.

Insulin-like growth factor binding protein-1 (IGFBP-1) and IGF-I during oral and transdermal estrogen replacement therapy: relation to lipoprotein(a) levels

Low levels of insulin-like growth factor binding protein-1 (IGFBP-1) have recently been associated with several risk factors for cardiovascular disease. The effects of estrogen replacement therapy (ERT) on plasma IGFBP-1 levels are, however, unclear. A double-blind, placebo-controlled study for 6 months was conducted in 73 hysterectomized postmenopausal women randomized into two groups: oral estradiol (E2) valerate, 2 mg/day (n = 35) and transdermal E2 gel, 1 mg/day (n=38). Plasma IGFBP-1, insulin-like growth factor-I (IGF-I) and lipoprotein(a) (Lp(a)) were determined at baseline, 3 and 6 months. The groups were similar for age and BMI. The baseline levels of estrone (E1), E2, IGFBP-1, IGF-I and Lp(a) did not differ between the groups. During treatment, serum estradiol concentrations increased in both groups. During oral ERT, IGFBP-1 levels increased by 104% (P<0.001), whereas IGF-I levels decreased by 13% (mean, P<0.05). IGF-I and IGFBP-1 levels remained unchanged in the transdermal group. Lp(a) levels decreased by 23% (median, P<0.001) in the oral group, but were unaffected by transdermal therapy. The change in IGFBP-1 concentrations during oral ERT showed an inverse correlation to that in Lp(a) (r = -0.40, P<0.05, Spearman correlation). In conclusion, oral ERT seems to enhance plasma levels of IGFBP-1, which may be one reason for the reduced Lp(a) levels.

Different influences of classical antipsychotics and clozapine on glucose-insulin homeostasis in patients with schizophrenia or related psychoses

BACKGROUND

The aim of this study was to investigate the influence of classical antipsychotics and the atypical antipsychotic agent clozapine on glucose-insulin homeostasis to explain possible mechanisms behind weight gain associated with antipsychotic treatment.

METHOD

Twenty-eight patients on therapy with classical antipsychotics and 13 patients treated with clozapine (all meeting DSM-III-R criteria for schizophrenia or related psychoses) were studied. Fasting blood samples for glucose and insulin, as well as for 2 markers of the glucose-insulin homeostasis, i.e., the growth hormone (GH)-dependent insulin-like growth factor I (IGF-I) and the insulin-dependent insulin-like growth factor binding protein-1, were analyzed. Body mass index (BMI) was calculated and serum concentrations of the different antipsychotic drugs were measured. In addition, the relationship between the endocrine parameters and drug serum concentrations was examined.

RESULTS

The insulin levels were positively correlated to the serum concentration of clozapine, whereas no correlations were found between insulin and the serum concentrations of perphenazine (N = 12) or zuclopenthixol (N = 9). Insulin elevation was seen in the patients receiving clozapine more frequently than in the patients receiving classical antipsychotics. In addition, the median level of IGF-I was significantly lower in the patients receiving clozapine than in the patients receiving classical antipsychotics. No significant difference in BMI was found between the 2 patient groups, and all patients but 1 were normoglycemic.

CONCLUSION

The correlation between insulin and the clozapine concentration indicates a probable influence of clozapine on insulin secretion. The normal blood glucose levels in the clozapine group support the theory that clozapine induces concentration-dependent insulin resistance with secondary increased insulin secretion. In addition, lower median level of IGF-I in patients receiving clozapine compared with patients receiving classical antipsychotics points to a lower GH secretion in the clozapine group. This impaired GH secretion together with the clozapine-induced insulin resistance might be mechanisms behind weight gain during clozapine therapy.

Plasma insulin-like growth factor-I and its binding proteins 1 and 3 during continuous nonoral and oral combined hormone replacement therapy

OBJECTIVE

We determined the effects of continuous combined nonoral and oral estrogen-progestin therapy on plasma levels of insulin-like growth factor-I (IGF-I) and its binding proteins 1 (IGFBP-1) and 3 (IGFBP-3).

DESIGN

Forty women complaining of climacteric symptoms were randomized to receive either transdermal estradiol patches (50 microg daily) in combination with an intrauterine system releasing 20 microg of levonorgestrel daily or an established regimen of an oral dose of 2 mg of estradiol and 1 mg of norethisterone acetate daily for 1 year. Fifteen women in the nonoral therapy group and 17 in the oral therapy group completed the 1-year prospective study.

RESULTS

Plasma levels of IGF-I decreased significantly in the oral therapy group, but no changes were observed in the plasma levels of its binding proteins. Transdermal estrogen in combination with intrauterine levonorgestrel did not induce any change in plasma IGF-I, whereas the plasma levels of IGFBP-3 decreased. IGFBP-1 concentrations increased, which may be related to the induction of this protein into the endometrium by the intrauterine levonorgestrel delivery.

CONCLUSIONS

Both the nonoral and oral continuous combined estrogen-progestin therapies used in this study produced only minor changes in the circulating concentrations of IGF-I and its binding proteins.

Tissue availability of insulin-like growth factor I is inversely related to insulin resistance in essential hypertension: effects of angiotensin converting enzyme inhibition

BACKGROUND

The insulin-like growth factor I possesses biologic actions that resemble those of insulin. Tissue access of the factor depends on the distribution of the circulating bound factor between its binding protein 3 that remains within the intravascular space and its binding protein I that is able to cross the endothelium. Preliminary results have shown that tissue availability of insulin-like growth factor I is a determinant of glucose regulation in essential hypertension

OBJECTIVE

To investigate whether the tissue availability of circulating insulin-like growth factor I in patients with essential hypertension is related to insulin resistance and whether chronic angiotensin converting enzyme inhibition influences tissue availability of the factor and insulin resistance in these patients.

DESIGN AND METHODS

We studied 29 patients with essential hypertension and 20 age-matched and sex-matched normotensive subjects. The measurements were repeated for 25 patients after 12 months of treatment with lisinopril. Tissue availability of circulating insulin-like growth factor I was assessed by analyzing its distribution between its binding proteins 3 and 1. An insulin resistance index was estimated using the homeostasis model analysis of fasting insulin-glucose interactions. Levels of serum insulin-like growth factor I binding proteins 3 and 1, plasma insulin-like growth factor I, and insulin were determined by specific radioimmunoassays.

RESULTS

Baseline insulin resistance index was significantly higher in the hypertensive patients than it was in the normotensive controls. With the upper 100% confidence limit of the normotensive population as the cutoff point, a subgroup of 12 hypertensives had an abnormally high insulin resistance index. Compared with patients with normal insulin resistance indexes, patients with greater than normal indexes were characterized by lower binding protein 1 levels, similar binding protein 3 levels, lower binding protein 1 : binding protein 3 ratio and similar insulin-like growth factor I levels. The serum binding protein 1 level and the binding protein 1 : binding protein 3 ratio were inversely correlated to the insulin resistance index for the whole group of hypertensives. After treatment with lisinopril hypertensive patients with higher than normal insulin resistance indexes at baseline exhibited normalization of this parameter and significant increases of binding protein 1 levels and binding protein 1 : binding protein 3 ratio, with no significant changes in insulin-like growth factor I levels. These parameters remained unchanged for the remaining patients.

CONCLUSIONS

These results suggest that tissue availability of circulating insulin-like growth factor I is a determinant of insulin sensitivity in patients with essential hypertension. Whereas the patients with normal insulin sensitivity exhibit greater than normal tissue access of circulating insulin-like growth factor I, patients with insulin resistance present normal tissue access of the factor. Our findings suggest that the ability of angiotensin converting enzyme inhibitors to restore insulin sensitivity in essential hypertensives may be related to their ability to facilitate the tissue availability of circulating insulin-like growth factor I.

mRNA expression of insulin-like growth factor-I (IGF-I) is suppressed and those of IGF-II and IGF-binding protein-1 are constantly expressed in the endometrium during use of an intrauterine levonorgestrel system

Insulin-like growth factors (IGF-I and IGF-II) are believed to mediate and modulate steroid hormone actions in the endometrium. In this study we determined the effects of an intrauterine system (IUS), releasing 20 microg levonorgestrel (LNG) daily, on endometrial expression of mRNAs encoding IGFs and insulin-like growth factor binding protein (IGFBP)-1. In Northern blotting, IGF-I mRNA was undetectable in all endometrial specimens from women with an LNG-IUS (n = 11) and in pregnancy decidua, whereas several transcripts of 0.6-7.6 kb were detected in proliferative and secretory phase endometria. In contrast, mRNAs encoding IGF-II and IGFBP-1 were strongly expressed in pregnancy and in all endometrial samples from women with an LNG-IUS, but were undetectable in proliferative or early to mid-secretory phase endometria. Using the more sensitive reverse transcriptase-polymerase chain reaction (RT-PCR) method, IGF-I and IGF-II mRNAs were detectable in all cycling endometria, in early pregnancy decidua and in LNG-exposed endometrium. IGFBP-1 mRNA was constantly expressed in LNG-exposed endometrium, in early pregnancy decidua and in premenstrual endometrium, but was undetectable in all specimens from proliferative or early to mid-secretory endometrium. Our data demonstrate that progestin treatment can affect the gene expression of endometrial growth factors in vivo. The consistent expression of mRNAs encoding IGF-II and IGFBP-1, with suppression of IGF-I mRNA in endometria exposed to LNG, suggests that this mode of hormone treatment can inhibit IGF-I action in the endometrium. If IGF-I mediates and modulates oestrogen action, suppression of IGF-I mRNA may be one of the molecular mechanisms which accounts for the antiproliferative effects of progestogens on oestrogen-primed endometrium and the atrophy of endometrial epithelium resulting from use of an LNG-IUS.

Differential role of glucocorticoids in mediating endotoxin-induced changes in IGF-I and IGFBP-1

The purpose of the present study was to determine whether endogenous elevations in glucocorticoids mediate the changes in insulin-like growth factor (IGF) 1 and IGF binding protein (IGFBP) 1 levels in plasma and tissues observed after in vivo administration of lipopolysaccharide (LPS). In overnight-fasted male rats LPS injected via the tail vein decreased the IGF-I concentration in plasma, liver, and skeletal muscle (30-45%) and increased IGF-I content in kidney (approximately 3-fold). LPS also decreased IGF-I mRNA abundance in liver and muscle and increased gene expression in kidney. Concomitantly, IGFBP-1 levels in plasma, liver, and muscle were markedly elevated by LPS. All these changes were associated with a greater than fourfold elevation in plasma corticosterone. Pretreatment of rats with the glucocorticoid receptor antagonist RU-486 completely prevented or blunted the LPS-induced changes in IGF-I content in plasma, liver, muscle, and kidney. In liver and muscle RU-486 significantly attenuated the reduction in IGF-I mRNA abundance produced by LPS, but in kidney the LPS-induced increase in IGF-I mRNA was still evident. In contrast, pretreatment with RU-486 did not prevent or attenuate the LPS-induced increase in IGFBP-1 levels in plasma, liver, or muscle. These data suggest that glucocorticoids play a major role in regulating IGF-I mRNA and peptide content in tissues in response to LPS, but the increased IGFBP-1 in blood and tissues induced by LPS appears largely glucocorticoid independent.

Progesterone receptor (PR) inhibits expression of insulin-like growth factor-binding protein-1 (IGFBP-1) in human endometrial cell line HEC-1B: characterization of the inhibitory effect of PR on the distal promoter region of the IGFBP-1 gene

Progestin has been shown to have both stimulatory and inhibitory effects on the expression of insulin-like growth factor binding protein-1 (IGFBP-1) in human endometrial cells. In this study, progestin was found to reduce levels of secreted IGFBP-1 and IGFBP-1 messenger RNA and IGFBP-1 promoter activity after stably transfecting a progesterone receptor (PR; B form) expression vector into HEC-1B cells. Deletion analysis of the IGFBP-1 promoter revealed that PR specifically inhibited promoter activity derived from a 59-bp distal BsaHI/RsaI fragment. It was concluded that PR inhibited the promoter activity through protein-protein interactions based on the facts that 1) no progesterone-responsive element was revealed by a series block mutation in the BsaHI/RsaI fragment; 2) PR bound by the antiprogesterone ZK98299 inhibited IGFBP-1 promoter activity; 3) a DNA-binding mutant of PR inhibited the IGFBP-1 promoter activity; and 4) in an in vivo competition assay, the DNA-binding domain of PR did not release the inhibitory effect of intact PR. Analysis of PR deletion mutants indicated that both transcriptional activation domains of PR (TAF-1 and TAF-2) were involved in the inhibition of IGFBP-1 expression. Thus, our data may explain the superinduction of IGFBP-1 in human endometrial cells after progestin withdrawal or progestin replacement with antiprogestin.

Free and total insulin-like growth factors and insulin-like growth factor binding proteins during 14 days of growth hormone administration in healthy adults

The objective was to investigate the effect of growth hormone (GH) administration on circulating levels of free insulin-like growth factors (IGFs) in healthy adults. Eight healthy male subjects were given placebo and two doses of GH (3 and 6 IU/m2 per day) for 14 days in a double-blind crossover study. Fasting blood samples were obtained every second day. Free IGF-I and IGF-II were determined by ultrafiltration of serum. Total IGF-I and IGF-II were measured after acid-ethanol extraction. In addition, GH, insulin, IGF binding protein 1 (IGFBP-1) and IGFBP-3 were measured. Serum-free and total IGF-I increased in a dose-dependent manner during the 14 days of GH administration. After 14 days, serum-free IGF-I values were 610 +/- 100 ng/l (mean +/- SEM) (placebo), 2760 +/- 190 ng/l (3 IU/ m2) and 3720 +/- 240 ng/l (6 IU/m2) (p = 0.0001 for 3 and 6 IU/m2 vs placebo; p = 0.004 for 3 IU/m2 vs 6 IU/m2). Total IGF-I values were 190 +/- 10 micrograms/l (placebo), 525 +/- 10 (3 IU/m2), and 655 +/- 40 micrograms/l (6 IU/m2) (p < 0.0001 for 3 and 6 IU/m2 vs placebo; p = 0.04 for 3 IU/m2). There were no differences in the levels of free or total IGF-II during the three study periods. Insulin-like growth factor binding protein 1 was decreased during GH administration (p = 0.04 for placebo vs 3 IU/m2; p = 0.006 for placebo vs 6 IU/m2). In conclusion, fasting serum free IGF-I increased dose dependently during GH administration and free IGF-I increased relatively more than total IGF-I. This may partly be due to the decrease in IGFBP-1.

Serum levels of insulin-like growth factor-1, IGF binding protein-1 and insulin and the response to human menopausal gonadotrophins in women with polycystic ovary syndrome

In order to determine which factors influence the large variations in sensitivity to gonadotrophins witnessed in women with polycystic ovary syndrome (PCOS), a prospective study was conducted of the correlation between basal clinical and endocrinological features and gonadotrophin requirements of 20 women with clomiphene-resistant PCOS undergoing ovulation induction. Baseline evaluation of serum concentrations of luteinizing hormone (LH), follicle stimulating hormone (FSH), testosterone, fasting insulin, insulin-like growth factor-1 (IGF-1), IGF binding protein-1 (IGFBP-1) and sex hormone-binding globulin (SHBG) were performed before administering gonadotrophin-releasing hormone agonist (GnRHa). Two weeks later, human menopausal gonadotrophin (HMG) was given in a standard individualized protocol according to ovarian response, until human chorionic gonadotrophin (HCG) was given. Serum concentrations of insulin, IGF-1, and IGFBP-1 were unaffected by GnRHa. The BMI correlated positively with insulin and inversely with IGFBP-1 serum concentrations and insulin and IGFBP-1 were inversely correlated. The amount of HMG required correlated positively with BMI and insulin concentrations and inversely with IGFBP-1 in the whole group and these correlations were maintained in the sub-group of lean women. No correlation was observed between HMG requirements and IGF-1 or other hormones. Women with hyperinsulinaemia and low IGFBP-1 concentrations required significantly more HMG. Multiple regression analysis revealed that insulin concentration is the most significant determinant of HMG requirement even when dissociated from BMI. We concluded that requirements of HMG in PCOS is not merely determined by obesity but by a cardinal role of insulin concentrations which, when high, induce, hypothetically, a hyperandrogenic intrafollicular milieu.

The effect of epidermal growth factor on circulating levels of free and total IGF-I and IGF-binding proteins in adult rats

In neonatal rats, systemic administration of epidermal growth factor (EGF) results in reduced body weight gain and decreased levels of circulating IGF-I, which suggests that it be involved in the EGF-induced growth retardation. We investigated the effect of 4 weeks of EGF administration on circulating free and total IGF-I and IGF-binding proteins (IGFBPs) in adult rats treated with saline (controls), 30 (low dose group) and 150 (high dose group) microgram/kg/day EGF. Serum IGF-I was determined in ultrafiltrates (free) and acid-ethanol extracts (total), and serum IGFBPs using Western ligand blotting, which yielded four distinct molecular bands. The IGFBPs were tentatively identified as IGFBP-3 (a double band at 42 and 38 kDa), IGFBP-1 and/or IGFBP-2 (a single band at 30 kDa) and IGFBP-4 (a single band at 24 kDa). EGF administration did not change the body weight, tibia length, or liver, heart and lung weight. In contrast, serum total IGF-I and IGFBP-3 decreased dose-dependently: total IGF-I averaged 1470 +/- 100 micrograms/l (controls; mean +/- SEM), 1030 +/- 60 micrograms/l (low dose group; P < 0.005) and 760 +/- 40 micrograms/l (high dose group; P < 0.005), whereas differences between IGFBP-3 levels reached significance (P < 0.05) between controls and high dose rats, only. When compared to controls, levels of IGFBP-1 and/or IGFBP-2 were increased in the low dose group (P < 0.05), but unchanged in the high dose group. IGFBP-4 was unaffected by EGF. Free IGF-I averaged 74 +/- 6 micrograms/l in controls, and was reduced to 35 +/- 6 micrograms/l (low dose group; P < 0.005) and 57 +/- 5 micrograms/l (high dose group; P < 0.05). Free IGF-I was inversely correlated (r = -0.49, P < 0.05) with IGFBP-1 and/or IGFBP-2. We conclude that in adult rats prolonged EGF administration has a marked depressing effect on circulating total and free IGF-I. Nevertheless, we did not observe any somatic growth retardation.

Retinoic acid suppresses in-vitro decidualization of human endometrial stromal cells

All-trans retinoic acid (RA) has potent effects on cell differentiation and gene expression. Previous studies have demonstrated that human endometrial stromal cells express mRNA for retinoic acid receptors (RARs) and cellular RA-binding protein-II (CRABP-II). We examined whether RA regulates stromal cell differentiation (decidualization), a critical process in preparation of the uterus for blastocyst implantation. Decidualization was induced by incubating cultured stromal cells with medroxyprogesterone acetate (MPA) and oestradiol. Decidualization was defined by the induction of prolactin, insulin-like growth factor binding protein-1 (IGFBP-1), appearance of a differentiated phenotype and changes in fibronectin expression. RA treatment significantly (P < 0.05) suppressed prolactin and IGFBP-1 production associated with stromal cells decidualization. The formation of differentiated cells was inhibited by RA, and consistent with maintenance of the undifferentiated phenotype, fibronectin mRNA content was approximately 3.5-times greater than in the absence of RA. Upon induction of decidualization, the expression of mRNA for the major RA receptor sub-types (RAR-alpha, -beta and -gamma) was maintained while the relative amounts of CRABP-II mRNA progressively decreased with differentiation. With RA treatment, RAR-alpha and RAR-gamma mRNA concentrations were approximately 70 and 25% respectively of those in cells decidualized in the absence of RA. The effects of RA appear to be partially mediated by inhibition of cAMP action. RA suppressed intracellular cAMP concentrations induced by MPA and oestradiol to approximately 35% of those in cells without RA. Addition of 50 microM dibutyryl cAMP to stromal cells treated with MPA and oestradiol only partially reversed the suppression of decidualization and prolactin release by RA. In summary, we have demonstrated that in-vitro decidualization of human endometrial stromal cells induced by MPA and oestradiol treatment is suppressed by RA.

Insulin-like growth factor-binding protein-1: a biochemical marker of endometrial response to progestin during hormone replacement therapy

OBJECTIVES

To compare immunohistochemical localization of insulin-like growth factor binding protein-1 (IGFBP-1) in endometrial stromal cells with endometrial morphology during three regimens of continuous combined hormone replacement therapy.

METHODS

Endometrial samples for morphological examination and immunohistochemical staining with monoclonal antibody against IGFBP-1 were obtained from 30 menopausal women before treatment and after 12 and 24 months of continuous combined hormone replacement therapy. All women received percutaneous estradiolgel releasing 1.5 mg estradiol daily. Regarding progestins, patients were divided into three groups: one group (n = 15) had a 20 micrograms/24 h levonorgestrel-releasing intrauterine device (LNG-IUD); the women in the other two groups received micronised natural progesterone either 100 mg orally (n = 7) or 100-200 mg vaginally (n = 8) daily, 25 days per calendar month.

RESULTS

Before treatment the endometrium of all women was atrophic or subatrophic and no IGFBP-1 could be detected in any of the samples which contained enough stromal cells for evaluation. After 12 and 24 months of treatment, epithelial atrophy with decidual transformation in stroma was detected in all specimens in the LNG-IUD group, and IGFBP-1 was localized in decidualized stromal cells in all samples. In the other two groups, no signs of progestin effect were detected by microscopic examination in any of the endometrial samples and IGFBP-1 staining was completely negative in all of them.

CONCLUSION

A striking difference occurred in both morphological and biochemical response in the endometrium of women treated with LNG-IUD compared with those receiving oral or vaginal micronised progesterone during continuous combined HRT. Micronised progesterone at doses used in this study turned out to be ineffective to prevent the proliferative effect of estrogen. Immunohistochemical localization of IGFBP-1 in endometrial stromal cells strongly correlated with decidual reaction in all endometrial specimens exposed to LNG-IUD, suggesting that the immunostaining of IGFBP-1 can be used as a means of assessing the strength of progestin effect in the endometrium during HRT.

Modulation of inflammation-induced changes in insulin-like growth factor (IGF)-I and IGF binding protein-1 by anti-TNF antibody

The aim of the present study was to characterize changes in the insulin-like growth factor (IGF) system produced by the nonbacterial nonendotoxic inflammatory agent zymosan and to determine whether these changes were mediated by enhanced production of tumor necrosis factor (TNF). Rats were injected intraperitoneally with either zymosan or saline and studied 18 h later. Animals were pretreated with either nonimmune IgG or neutralizing anti-TNF antibody 2 h before zymosan injection. Zymosan increased the plasma concentration of TNF alpha, and this was associated with a decrease (approximately 40%) in the IGF-I concentration in plasma, liver, heart, and brain. The IGF-I content was not altered in skeletal muscle and kidney. Zymosan also increased the concentration of IGF binding protein (BP)-1 in plasma (120%), liver (90%), and muscle (470%). Circulating TNF alpha was not detectable in rats injected with anti-TNF antibody before zymosan. The neutralizing antibody prevented the zymosan-induced reduction in IGF-I in plasma and blunted the decreased observed in liver, but did not alter the decrease in heart or brain. Anti-TNF antibody also attenuated (40-60%) the increased IGFBP-1 in plasma, liver, and muscle observed in zymosan-treated rats. We conclude that zymosan-induced inflammation not only decreases IGF-I in plasma and selected tissues, but also increases IGFBP-1 in plasma, liver, and muscle, and that these alterations are due in large part to the enhanced production of TNF alpha.

Oral intake of selenium has no effect on the serum concentrations of growth hormone, insulin-like growth factor-1, insulin-like growth factor-binding proteins 1 and 3 in healthy women

The administration of large doses of selenium (Se) to rats leads to reduced serum levels of somatotropin (growth hormone) and insulin-like growth factor-1 (IGF-1), followed by growth retardation. Similar experiments in humans have been contradictory. The effects of wheat Se and selenomethionine supplementation were investigated in healthy, Norwegian women. In study 1, the participants (n = 18) were given Se-rich bread with 100, 200 and 300 micrograms Se daily for 6 weeks. Initial serum Se concentration were 1.5 +/- 0.2 mumol/l (mean +/- SD). Serum Se increased in a dose-dependent manner in the three groups (p < 0.001). There was no effect on somatotropin and IGF-1 at any of the Se doses given. In study 2 (n = 24), the effects of 400 micrograms selenomethionine daily for 15 weeks were studied in a placebo controlled study. In the treatment group, serum Se concentrations increased by more than 100%. There was, however, no effect on serum somatotropin and IGF-1 concentrations, nor was there any effect on IGF-binding proteins 1 and 3. Our results indicate that at normal or slightly increased intakes, Se has no effect on the serum concentrations of these two hormones in healthy individuals.