Effects of raloxifene and estrogen on bioactive IGF1 in GH-deficient women

Exergaming Improves Cardiac Risk Factors in Prostate Cancer Patients: A Single-Blinded Randomized Controlled Trial

Purpose: Androgen deprivation therapy (ADT) may induce unfavorable changes in metabolic outcomes, insulin sensitivity, insulin-like growth factors (IGFs), and in serum levels of adipocyte-derived hormones. In this preplanned randomized ancillary study, we aimed to investigate the ability of exercise to counteract alterations in triglyceride, cholesterol, waist circumference, and insulin caused by ADT in men with locally advanced and metastatic prostate cancer (PCa). Materials and Methods: Forty-six PCa patients undergoing treatment were randomized to 12 weeks of 180 minutes of weekly unsupervised home-based exergaming or usual care. Blood glucose, lipids, cholesterol, adiponectin, leptin, insulin sensitivity, and the insulin growth factor axis were measured at baseline, and after 12 and 24 weeks. Biomarkers were analyzed using a linear mixed-effect model of the difference between the groups from baseline to week 24. In addition, blood pressure, body mass index, body weight, and waist circumference were measured at baseline and after 12 weeks/end of intervention and analyzed using adjusted linear regression analysis. Results: After 24 weeks, a significant difference was seen between the intervention and usual care groups in plasma triglyceride (diff: 0.5 mmol/L, P = 0.02) and high-density lipoprotein (HDL; diff: 0.2 mmol/L, P = 0.01) favoring the intervention group, whereas IGF-binding protein-3 (diff: 148 μg/L, P = 0.01) favored the usual care group. The remaining outcomes were unaffected. Conclusion: Improvement in HDL cholesterol could be used as a primary biomarker in future randomized controlled trials investigating the cardiovascular protecting properties of exergaming.

Effects of raloxifene administration on serum levels of insulin-like growth factor-1 and insulin-like growth factor-binding protein 3 levels: A systematic review and meta-analysis of randomized controlled trials

OBJECTIVE

To ascertain the clinical magnitude of raloxifene administration on insulin-like growth factor-1 (IGF-1) and insulin-like growth factor-binding protein 3 (IGFBP-3) levels.

METHODS

A systematic comprehensive search was performed without language limitation up to 14 December 2020. We included only trials that assessed the effect of raloxifene on IGF-1 and IGFBP-3 in adults. Meta-analysis was performed using the Stata software (Stata Corp. College Station, Texas, USA).

RESULTS

Seven arms were included, encompassing postmenopausal women with type 2 diabetes mellitus, postmenopausal women with breast cancer, healthy postmenopausal women, and healthy elderly men. Raloxifene therapy significantly reduced IGF-1 levels (WMD: -2.92 nmol/L, 95% CI: -3.49, -2.35, p < 0.001) compared to placebo. Raloxifene dosage ˃60 mg/day (WMD: -3.29 ng/mL, 95% CI: -3.50 to -3.08, I² = 0.0%) decreased IGF-1 levels more than 60 mg/day (WMD: -2.29 ng/mL, 95% CI: -2.90 to -1.69, I² = 16%). Moreover, intervention duration ˃26 weeks (WMD: -3.48 ng/mL, 95% CI: -5.26 to -1.69, I² = 0.0%) reduced IGF-1 levels more than ˂26 weeks (WMD: -2.55 ng/mL, 95% CI: -3.31 to -1.79, I² = 92%). In contrast, overall results from the random-effects model did not suggest a significant change in IGFBP-3 levels upon raloxifene therapy.

CONCLUSION

Raloxifene therapy significantly reduced serum levels of IGF-1 levels but without changes in IGFPB-3 levels.

IGFBP3 as an indicator of lymph node metastasis and unfavorable prognosis for papillary thyroid carcinoma

Lymph node metastasis (LNM) is a usual event in papillary thyroid carcinoma (PTC) patients, which usually leads to poor prognosis. However, the molecular mechanisms of LNM remain unclear. Thus, we aimed to screen the possible key genes in the progression of LNM in PTC patients and further validate their roles. The study involved two phases: a discovery phase and a validation one. In the former phase, the candidate genes were screened by using bioinformatics methods. In the latter one, the genes were firstly assessed in a cohort from the cancer genome atlas (TCGA) to evaluate the associations of their expressions with clinical features and the prognostic values, and then, they were assessed at protein levels by using an immunohistochemical assay. Consequently, IGHBP3 was selected as the candidate gene, which might be enriched in several metabolism-related pathways and cancer progression-related pathways. High expressions of IGHBP3 have an association with gender, advanced clinical stages, high T stages, and the presence of LNM. Survival analysis indicated that IGHBP3 may affect the prognosis of PTC patients. The use of a tissue chip confirmed the view that IGHBP3 might play a crucial role in the LNM of PTC. In conclusion, IGHBP3 might be involved in the development of LNM in PTC patients. IGHBP3 over-expression might be a novel indicator and a potential target for PTC therapy.

Development of a novel assay for IGFBP-2 complexed with IGF-I and-II in human serum

BACKGROUND

Insulin-like growth factor binding-protein 2 (IGFBP-2) was originally identified as an IGF-carrier, governing IGF half-life, tissue accessibility and biological effects. Later, IGFBP-2 was discovered to possess IGF-independent effects. IGFBP-2 circulates in several forms, as free protein, complexed with IGF-I or IGF-II, or as IGFBP-2 fragments. The various IGFBP-2 forms are all included when measuring serum IGFBP-2 concentrations by immunoassay (i.e., immunoreactive (ir-)IGFBP-2). In this study, we describe a novel method to measure the amount of IGF that circulates bound to IGFBP-2.

METHOD

IGFBP-2 was immunoprecipitated from human serum using magnetic beads, which were subsequently eluted by acidification. After neutralization, eluates were assayed for ir-IGFBP-2, IGF-I and IGF-II and compared to serum concentrations. This allowed measurement of IGFBP-2-compexed IGF-I and IGF-II, respectively. To test the method clinically, serum from 146 patients with lung cancer, 151 patients with non-cancer pulmonary diseases and 28 healthy controls were analyzed.

RESULTS

We immuno-precipitated 97 ± 3.3% of serum IGFBP-2 and recovered > 75% of IGFBP-2-complexed IGFs, with intra- and inter-assay coefficient of variations (CVs) averaging < 5% and < 13%, respectively. No co-precipitation with IGFBP-1, -3 or - 4 was detected. Serum levels of ir-IGFBP-2 (median [25;75%]) differed between groups (cancer patients vs. non-cancer patients vs. healthy controls): 342 [260;480] vs. 262 [189;388] vs. 190 [141;269] μg/l (p < .0001). In parallel with this, concentrations of IGF-II carried by IGFBP-2 averaged: 45.0 [33.3;52.5] vs. 34.2 [25.4;46.1] vs. 19.8 [14.1;26.0] μg/l (p < .0001), and concentrations of IGF-I 8.0 [5.2;11.8] vs. 5.4 [3.6;7.3] vs. 7.0 [3.8;13.0] μg/l (p < .0001). Thus, IGFBP-2 carried more IGF-II than IGF-I in all groups (p < .0001). When expressed relative to IGF-concentrations, IGFBP-2 carried 9.0 [5.3;15.5] % of the IGF-I and 4.8 [2.9;5.8] % of the IGF-II in serum from healthy subjects. Notably, in patients, IGFBP-2 carried relatively less IGF-I, but more IGF-II (p < .0001).

CONCLUSION

Using our novel assay, we demonstrate: that IGFBP-2 carries ≈10% of circulating IGF-I and ≈5% of circulating IGF-II in healthy subjects; that IGF-II is the primary ligand for IGFBP-2; and that IGFBP-2 carries even more IGF-II in patients than in healthy subjects. Thus, our assay may provide information on IGFBP-2 beyond what is achievable by simply measuring ir-IGFBP-2.

The insulin-like growth factor-I receptor stimulating activity (IRSA) in health and disease

Determination of true IGF-I bioactivity in serum and other biological fluids is still a substantial challenge. The IGF-IR Kinase Receptor Activation assay (IGF-IR KIRA assay) is a novel tool to asses IGF-IR stimulating activity (IRSA) and has opened a new era in studying the IGF system. In this paper we discuss many studies showing that measuring IRSA by the IGF-IR KIRA assay often provides fundamentally different information about the IGF system than the commonly used total IGF-I immunoassays. With the IGF-IR KIRA assay phosphorylation of tyrosine residues of the IGF-IR is used as read out to quantify IRSA in unknown (serum) samples. The IGF-IR KIRA assay gives information about net overall effects of circulating IGF-I, IGF-II, IGFBPs and IGFBP-proteases on IGF-IR activation and seems especially superior to immunoreactive total IGF-I in monitoring therapeutic interventions. Although the IRSA as measured by the IGF-IR KIRA assay probably more closely reflects true bioactive IGF-I than measurements of total IGF-I in serum, the IGF-IR KIRA assay in its current form does not give information about all the post-receptor intracellular events mediated by the IGF-IR. Interestingly, in several conditions in health and disease IRSA measured by the IGF-IR KIRA assay is considerably higher in interstitial fluid and ascites than in serum. This suggests that both the paracrine (local) and endocrine (circulating) IRSA should be measured to get a complete picture about the role of the IGF system in health and disease.

The IGF system in patients with inflammatory bowel disease treated with prednisolone or infliximab: potential role of the stanniocalcin-2 / PAPP-A / IGFBP-4 axis

Background

Patients with inflammatory bowel disease (IBD) present with reduced serum insulin-like growth factor I (IGF-I). Anti-inflammatory treatment with prednisolone or infliximab ameliorates symptoms and increases circulating IGF-I, but prednisolone induces catabolism, whereas infliximab may promote protein synthesis. Recently, stanniocalcin-2 (STC2) was discovered as a novel inhibitor of the enzyme pregnancy-associated plasma protein-A (PAPP-A), which modulates IGF-I activity. PAPP-A can cleave IGF binding protein-4 (IGFBP-4), upon which IGF-I is liberated. We hypothesized that prednisolone and infliximab exert different effects on levels of STC2, PAPP-A, and IGFBP-4, thereby explaining the distinct metabolic effects of prednisolone and infliximab.

Methods

Thirty-eight patients with active IBD treated with either prednisolone (n = 17) or infliximab (n = 21) were examined before and after 7 days of treatment. Circulating levels of IGF-I, IGF-II, IGFBP-3, PAPP-A, and STC2 were measured by immunoassays. Intact IGFBP-4 and two IGFBP-4 fragments were determined by a novel immunoassay. Bioactive IGF was assessed by cell-based IGF receptor activation assay. Concentrations of IGFBP-4, PAPP-A, and STC2 on day 0 and 7 were compared to healthy control subjects.

Results

Following seven days of prednisolone treatment, total and bioactive IGF-I were increased (p < 0.001 and p < 0.05, respectively). Upon infliximab treatment, total IGF-I levels were augmented (p < 0.05), yet IGF bioactivity remained unaltered. Intact IGFBP-4 and the two IGFBP-4 fragments generated upon cleavage by PAPP-A were all decreased following treatment with either prednisolone or infliximab (all p < 0.05). PAPP-A levels were only increased by infliximab (p = 0.005), whereas the inhibitor STC2 did not respond to any of the treatments.

Conclusion

IGF-I and IGFBP-4 concentrations were markedly altered in patients with IBD and near-normalized with disease remission following treatment with prednisolone or infliximab. Thus, IGFBP-4 may modulate IGF bioavailability in IBD. The effect of immunosuppression did not appear to extend beyond the regulation of IGF and IGFBP-4, as neither PAPP-A nor STC2 were discernibly affected.

Trial registration

ClinicalTrials.gov: NCT00955123. Date of registration: August 7, 2009 (retrospectively registered).

The effect of growth hormone on bioactive IGF in overweight/obese women

OBJECTIVE

Overweight/obesity is characterized by decreased growth hormone (GH) secretion whereas circulating IGF-I levels are less severely reduced. Yet, the activity of the circulating IGF-system appears to be normal in overweight/obese subjects, as estimated by the ability of serum to activate the IGF-I receptor in vitro (bioactive IGF). We hypothesized that preservation of bioactive IGF in overweight/obese women is regulated by an insulin-mediated suppression of IGF-binding protein-1 (IGFBP-1) and IGFBP-2, and by suppression of IGFBP-3, mediated by low GH. We additionally hypothesized that increases in bioactive IGF would drive changes in body composition with low-dose GH administration.

DESIGN

Cross-sectional analysis and 3-month interim analysis of a 6-month randomized, placebo-controlled study of GH administration in 50 overweight/obese women without diabetes mellitus. Bioactive IGF (kinase receptor activation assay) and body composition (DXA) were measured.

RESULTS

Prior to treatment, IGFBP-3 (r = -0.33, p = 0.02), but neither IGFBP-1 nor IGFBP-2, associated inversely with bioactive IGF. In multivariate analysis, lower IGFBP-3 correlated with lower peak stimulated GH (r = 0.45, p = 0.05) and higher insulin sensitivity (r = -0.74, p = 0.003). GH administration resulted in an increase in mean serum IGF-I concentrations (144 ± 56 to 269 ± 66 μg/L, p < 0.0001) and bioactive IGF (1.29 ± 0.39 to 2.60 ± 1.12 μg/L, p < 0.0001). The treatment-related increase in bioactive IGF, but not total IGF-I concentration, predicted an increase in lean mass (r = 0.31, p = 0.03) and decrease in total adipose tissue/BMI (r = -0.43, p = 0.003).

CONCLUSIONS

Our data suggest that in overweight/obesity, insulin sensitivity and GH have opposing effects on IGF bioactivity through effects on IGFBP-3. Furthermore, increases in bioactive IGF, rather than IGF-I concentration, predicted GH administration-related body composition changes.

CLINICAL TRIAL REGISTRATION NUMBER

NCT00131378.

Effects of Prednisolone on Serum and Tissue Fluid IGF-I Receptor Activation and Post-Receptor Signaling in Humans

CONTEXT

Short-term glucocorticoid exposure increases serum insulinlike growth factor I (IGF-I) concentrations but antagonizes IGF-I tissue signaling. The underlying mechanisms remain unknown.

OBJECTIVE

To identify at which levels glucocorticoid inhibits IGF-I signaling.

DESIGN AND METHODS

Nineteen healthy males received prednisolone (37.5 mg/d) and placebo for 5 days in a randomized, double-blinded, placebo-controlled crossover study. Serum was collected on days 1, 3, and 5, and abdominal skin suction blister fluid (SBF; ~interstitial fluid) was taken on day 5 (n = 9) together with muscle biopsy specimens (n = 19). The ability of serum and SBF to activate the IGF-I receptor (IGF-IR) (bioactive IGF) and its downstream signaling proteins was assessed using IGF-IR-transfected cells.

RESULTS

Prednisolone increased IGF-I concentrations and bioactive IGF in serum (P ≤ 0.001) but not in SBF, which, compared with serum, contained less bioactive IGF (~28%) after prednisolone (P < 0.05). This observation was unexplained by SBF concentrations of IGFs and IGF-binding proteins (IGFBPs) 1 to 4. However, following prednisolone treatment, SBF contained less IGFBP-4 fragments (P < 0.05) generated by pregnancy-associated plasma protein A (PAPP-A). Concomitantly, prednisolone increased SBF levels of stanniocalcin 2 (STC2) (P = 0.02) compared with serum. STC2 blocks PAPP-A from cleaving IGFBP-4. Finally, prednisolone suppressed post-IGF-IR signaling pathways at the level of insulin receptor substrate 1 (P < 0.05) but did not change skeletal muscle IGF-IR, IGF-I, or STC2 messenger RNA.

CONCLUSION

Prednisolone increased IGF-I concentrations and IGF bioactivity in serum but not in tissue fluid. The latter may relate to a STC2-mediated inhibition of PAPP-A in tissue fluids. Furthermore, prednisolone induced post-IGF-IR resistance. Thus, glucocorticoid may exert distinct, compartment-specific effects on IGF action.

Sex steroids and the GH axis: Implications for the management of hypopituitarism

Growth hormone (GH) regulates somatic growth, substrate metabolism and body composition. Sex hormones exert profound effect on the secretion and action of GH. Estrogens stimulate the secretion of GH, but inhibit the action of GH on the liver, an effect that occurs when administered orally. Estrogens suppress GH receptor signaling by stimulating the expression proteins that inhibit cytokine receptor signaling. This effect of estrogens is avoided when physiological doses of estrogens are administered via a non-oral route. Estrogen-like compounds, such as selective estrogen receptor modulators, possess dual properties of inhibiting the secretion as well as the action of GH. In contrast, androgens stimulate GH secretion, driving IGF-1 production. In the periphery, androgens enhance the action of GH. The differential effects of estrogens and androgens influence the dose of GH replacement in patients with hypopituitarism on concomitant treatment with sex steroids. Where possible, a non-oral route of estrogen replacement is recommended for optimizing cost-benefit of GH replacement in women with GH deficiency. Adequate androgen replacement in conjunction with GH replacement is required to achieve the full anabolic effect in men with hypopituitarism.

Estrogens and selective estrogen receptor modulators in acromegaly

Despite recent advances in acromegaly treatment by surgery, drugs, and radiotherapy, hormonal control is still not achieved by some patients. The impairment of IGF-1 generation by estrogens in growth hormone deficient patients is well known. Patients on oral estrogens need higher growth hormone doses in order to achieve normal IGF-1 values. In the past, estrogens were one of the first drugs used to treat acromegaly. Nevertheless, due to the high doses used and the obvious side effects in male patients, this strategy was sidelined with the development of more specific drugs, as somatostatin receptor ligands and dopamine agonists. In the last 15 years, the antagonist of growth hormone receptor became available, making possible IGF-1 control of the majority of patients on this particular drug. However, due to its high cost, pegvisomant is still not available in many centers around the world. In this setting, the effect of estrogens and also of selective estrogen receptor modulators on IGF-1 control was reviewed, and proved to be an ancillary tool in the management of acromegaly. This review describes data concerning their efficacy and place in the treatment algorithm of acromegaly.

Is insulin-like growth factor-I a good marker for treatment adherence in growth hormone deficiency in adulthood?

OBJECTIVE

There is a paucity of studies on adherence to growth hormone treatment in growth hormone deficient (GHD) adults. Therefore, this study reports on adherence to GH-replacement therapy in adults with GHD, with a special focus on the course and potential predictors of nonadherence.

DESIGN

Retrospective single-centre cohort study.

PATIENTS

From the local patient database, 179 suitable patients with GHD were identified.

MEASUREMENTS

The primary outcome was adherence assessed by calculating the percentage of available prescription data in comparison with recommended GH dosages over a mean follow-up period of 92·4 months. Patients were categorized into five adherence categories ranging from <20% to >80%.

RESULTS

Mean overall adherence was 74·0%, with 52·9% of patients falling into the adherence group of >80% and 8·8% of <20%. There was a significant drop in adherence (9·8%) between the first and second years of treatment (P < 0·001). Patients with childhood-onset GHD were significantly less adherent to GH treatment than patients with adult-onset GHD (62·0% vs 77·0%, P = 0·012); however, this finding was no longer significant after including age as a covariate. Frequency of IGF-1 levels lying outside the age- and sex-specific reference range was not a good indicator for adherence.

CONCLUSION

Although overall adherence was relatively high in our study sample, there is a significant amount of patients who should be regarded as nonadherent. This applies in particular to younger patients. Treating physicians should be aware of the fact that IGF-1 levels do not seem to be a good indicator for adherence.

Differential effects of low birthweight and intrauterine growth restriction on umbilical cord blood insulin-like growth factor concentrations

OBJECTIVE

Alterations in the growth hormone-insulin-like growth factor (IGF) axis have been considered as a causal factor for intrauterine growth restriction (IUGR) and for the increased risk of metabolic disease in later life. We compared members of the IGF axis in umbilical cord blood between IUGR neonates, small for gestational age without foetal restriction (SGA) and appropriate for gestational age (AGA) neonates.

DESIGN

Prospective controlled multicenter study.

PATIENTS

Sixteen ultrasound-proven IUGR, 8 SGA and 40 AGA neonates.

MEASUREMENTS

Concentrations of total IGF-I and total IGF-II by immunoassays, bioactive IGF by cell-based bioassay and IGFBP-I in mixed venous and arterial umbilical cord blood samples at birth. Auxological parameters at birth.

RESULTS

IGF-I concentrations in IUGR [17·7 μg/l (CI 13·8;21·6)] were clearly below those in AGA [48·3 μg/l (CI 43·7;52·9)] and SGA neonates [36·0 μg/l (CI 26·6;45·4)]. IGF-II levels were significantly reduced in IUGR [201·4 μg/l (CI 190·2;212·6)] compared to AGA neonates [231·2 μg/l (CI 220·6;241·9)]. A trend for lower IGF-II concentrations was observed in IUGR when compared to SGA neonates [232·0 μg/l (CI 207·2;256·8)]. These differences could not be explained by confounding. For IGFBP-1, a trend towards higher values in IUGR was observed.

CONCLUSIONS

Low IGF-I cord blood concentrations in hypotrophic neonates after IUGR might not only result from low birthweight per se, but also reflect prenatal placental environment. Alterations of the IGF axis could be in the causal pathway of IUGR and thus constitute a potential surrogate marker for IUGR in the assessment of foetal programming.