Normal Values of Circulating IGF-I Bioactivity in the Healthy Population: Comparison with five widely used IGF-I immunoassays

Background: IGF-I immunoassays are primarily used to estimate IGF-I bioactivity. Recently, an IGFI specific Kinase Receptor Activation Assay (KIRA) has been developed as an alternative method. However, no normative values have been established for the IGF-I KIRA. Objective: To establish normative values for the IGF-I KIRA in healthy adults. Design: Cross-sectional study in healthy non-fasting blood donors. Study participants: 426 healthy individuals (310 M, 116 F; age range: 18 – 79 yrs) Main outcome Measures: IGF-I bioactivity determined by the KIRA. Results were compared with total IGF-I, measured by five different IGF-I immunoassays. Results: Mean (± SD) IGF-I bioactivity was 423 (± 131) pmol/L and decreased with age (β = -3.4 pmol/L/yr, p < 0.001). In subjects younger than 55 yrs mean IGF-I bioactivity was significantly higher in women than in men. Above this age this relationship was inverse, suggesting a drop in IGF-I bioactivity after menopause. This drop was not reflected in total IGF-I levels. IGF-I bioactivity was significantly related to total IGF-I (rs varied between 0.46 – 0.52; P-values < 0.001). Conclusions: We established age-specific normative values for the IGF-I KIRA. We observed a significant drop in IGF-I bioactivity in women between 50 and 60 years, which was not perceived by IGF-I immunoassays. The IGF-I KIRA, when compared to IGF-I immunoassays, theoretically has the advantage that it measures net effects of IGF-binding proteins on IGF-I receptor activation. However, it has to be proven whether information obtained by the IGF-I KIRA is clinically more relevant than measurements obtained by IGF-I immunoassays

Effect of estrogen on tendon collagen synthesis, tendon structural characteristics, and biomechanical properties in postmenopausal women

Udgivelsesdato: 2009-AprThe knowledge about the effect of estradiol on tendon connective tissue is limited. Therefore, we studied the influence of estradiol on tendon synthesis, structure, and biomechanical properties in postmenopausal women. Nonusers (control, n = 10) or habitual users of oral estradiol replacement therapy (ERT, n = 10) were studied at rest and in response to one-legged resistance exercise. Synthesis of tendon collagen was determined by stable isotope incorporation [fractional synthesis rate (FSR)] and microdialysis technique (NH(2)-terminal propeptide of type I collagen synthesis). Tendon area and fibril characteristics were determined by MRI and transmission electron microscopy, whereas tendon biomechanical properties were measured during isometric maximal voluntary contraction by ultrasound recording. Tendon FSR was markedly higher in ERT users (P &lt; 0.001), whereas no group difference was seen in tendon NH(2)-terminal propeptide of type I collagen synthesis (P = 0.32). In ERT users, positive correlations between serum estradiol (s-estradiol) and tendon synthesis were observed, whereas change in tendon synthesis from rest to exercise was negatively correlated to s-estradiol. Tendon area, fibril density, fibril volume fraction, and fibril mean area did not differ between groups. However, the percentage of medium-sized fibrils was higher in ERT users (P &lt; 0.05), whereas the percentage of large fibrils tended to be greater in control (P = 0.10). A lower Young's modulus (GPa/%) was found in ERT users (P &lt; 0.05). In conclusion, estradiol administration was associated with higher tendon FSR and a higher relative number of smaller fibrils. Whereas this indicates stimulated collagen turnover in the resting state, collagen responses to exercise were negatively associated with s-estradiol. These results indicate a pivotal role for estradiol in maintaining homeostasis of female connective tissue

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 &lt; 0.001 and p &lt; 0.05, respectively). Upon infliximab treatment, total IGF-I levels were augmented (p &lt; 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 &lt; 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).</p

Insulin-Like Growth Factor Binding Protein 4 Fragments Provide Incremental Prognostic Information on Cardiovascular Events in Patients With ST-Segment Elevation Myocardial Infarction

Background Fragments of insulin‐like growth factor binding protein 4 ( IGFBP ‐4) are potential new biomarkers for cardiac risk assessment. The fragments are generated on specific cleavage by pregnancy‐associated plasma protein‐A, which exerts proatherogenic activity. This study investigated the prognostic value of IGFBP ‐4 fragments in patients with ST ‐segment elevation myocardial infarction. Methods and Results We prospectively included 656 patients with ST ‐segment elevation myocardial infarction treated with percutaneous coronary intervention from September 2006 to December 2008. Blood samples were drawn before percutaneous coronary intervention, and levels of intact IGFBP ‐4 and N‐terminal and C‐terminal IGFBP ‐4 fragments were measured by specific assays. End points were 5‐year all‐cause and cardiovascular mortality and the combined end point of major adverse cardiac events. Prognostic potential was evaluated on top of a clinical model in terms of discrimination, calibration, and reclassification analysis. During follow‐up, 166 patients experienced a major adverse cardiac event and 136 patients died, of whom 69 died from cardiovascular causes. Both IGFBP ‐4 fragments were associated with all end points ( P &lt;0.001). After multivariable adjustments, both N‐terminal and C‐terminal IGFBP ‐4 fragment levels remained associated with all end points, including cardiovascular mortality with hazard ratios per doubling in protein concentration of 2.54 (95% CI 1.59–4.07; P &lt;0.001) and 2.07 (95% CI 1.41–3.04; P &lt;0.001), respectively. Incorporation of IGFBP ‐4 fragments into a clinical model with 15 risk factors improved C‐statistics and model calibration and provided incremental prognostic contribution, as assessed by net reclassification improvement and integrated discrimination improvement. Conclusions IGFBP ‐4 fragments are associated with increased risk of all‐cause mortality, cardiovascular mortality, and major adverse cardiac events in patients with ST ‐segment elevation myocardial infarction. </jats:sec

Growth hormone/insulin-like growth factor I axis in health and disease states:an update on the role of intra-portal insulin

Growth hormone (GH) is the key regulator of insulin-like growth factor I (IGF-I) generation in healthy states. However, portal insulin delivery is also an essential co-player in the regulation of the GH/IGF-I axis by affecting and regulating hepatic GH receptor synthesis, and subsequently altering hepatic GH sensitivity and IGF-I generation. Disease states of GH excess (e.g., acromegaly) and GH deficiency (e.g., congenital isolated GH deficiency) are characterized by increased and decreased GH, IGF-I and insulin levels, respectively, where the GH/IGF-I relationship is reflected by a “primary association”. When intra-portal insulin levels are increased (e.g., obesity, Cushing’s syndrome, or due to treatment with glucocorticoids and glucagon-like peptide 1 receptor agonists) or decreased (e.g., malnutrition, anorexia nervosa and type 1 diabetes mellitus), these changes secondarily alter hepatic GH sensitivity resulting in a “secondary association” with discordant GH and IGF-I levels (e.g., high GH/low IGF-I levels or low GH/high IGF-I levels, respectively). Additionally, intra-portal insulin regulates hepatic secretion of IGFBP-1, an inhibitor of IGF-I action. Through its effects on IGFBP-1 and subsequently free IGF-I, intra-portal insulin exerts its effects to influence endogenous GH secretion via the negative feedback loop. Therefore, it is important to understand the effects of changes in intra-portal insulin when interpreting the GH/IGF-I axis in disease states. This review summarizes our current understanding of how changes in intra-portal insulin delivery to the liver in health, disease states and drug therapy use and misuse that leads to alterations in GH/IGF-I secretion that may dictate management decisions in afflicted patients.</p

Analyses of IGFBP2 DNA methylation and mRNA expression in visceral and subcutaneous adipose tissues of obese subjects

Insulin-like growth factor binding-protein 2 (IGFBP-2) is secreted by differentiating white adipocytes. Clinical studies demonstrate that circulating IGFBP-2 levels associated inversely with body mass index (BMI) and insulin resistance. To explore possible epigenetic changes of the IGFBP2 gene in obesity, we analyzed DNA methylation and mRNA expression in adipocytes from different depots. Healthy lean controls (BMI = 24.5 ± 0.3 kg/m 2 , n = 19) and obese subjects (BMI &gt; 35 kg/m 2 , n = 24) were recruited. All subjects were Swedish Caucasian. Visceral abdominal adipose tissue (VAT) and subcutaneous adipose tissue (SAT) fragments were homogenized. Genomic DNA and total RNAs were extracted. Four CpG sites in the IGFBP2 gene promoter region were analyzed with bisulfite pyrosequencing. IGFBP2 gene expression at mRNA levels was determined with TaqMan real time RT-PCR. Serum samples were used for measurement of circulating IGFBP-2 and leptin levels. IGFBP2 DNA methylation levels in VAT were increased in obese subjects compared with controls (P &lt;.05). By contrast, IGFBP2 mRNA expression levels in VAT were lower in obesity subjects than in controls (P &lt;.05). In SAT, IGFBP2 DNA methylation and RNA expression levels were lower than in VAT, irrespective of obesity. Obese subjects demonstrated increased serum leptin levels (P &lt;.001) and reduced serum IGFBP-2 levels compared to controls (P &lt;.05). In conclusion, the current study demonstrates that IGFBP2 DNA methylation levels are increased in VAT from obese subjects. This suggests that IGFBP-2 is epigenetically regulated in abdominal obesity. </p

Feasibility study of advanced cardiovascular screening in middle-aged patients with diabetes

Purpose: Cardiovascular mortality remains high among patients with diabetes compared with the general population. The primary aim was to evaluate the interest in and demand for advanced cardiovascular screening in patients with diabetes; the secondary aim was to explore its efficiency in detecting unprotected subclinical cardiovascular disease (CVD). Patients and Methods: In a cross-sectional design, randomly selected 40–60-year-old men and women with diabetes were invited to the screening trial. Screening encompassed (1) a comprehensive medical interview; (2) non-contrast computed tomography scanning to quantify coronary artery and aortic valve calcification, to measure left atrial size, to assess heart rhythm and to detect aortic and iliac dilatations; (3) ankle and brachial blood pressure measurements; and (4) blood and urine samples for measurements of HbA1c, lipid profile, renal function, NT-pro B-type natriuretic peptide (pro-BNP) and albuminuria. Primary outcome was participation rate; secondary outcome was rate of unprotected subclinical CVD. Results: Of 465 invited patients, 191 (41.1%) attended screening. The participation rate was 40% (95% CI:33–47) for males and 42% (95% CI:36–48) for females. Twenty-four patients were excluded due to previous CVD. The remaining patients’ mean age was 52 years; 58% were males. Subclinical CVD was found in 64%, with a male preponderance (males 75% (95% CI:66–83; females 49% (95% CI:37–60)). Presence of severe coronary artery calcification (score ≥ 400) showed a male preponderance (males 19% (95% CI:12–27); females 7% (95% CI:3–16)). Aortic valve calcification, enlarged left atrial volume, atrial fibrillation, aortic dilatations, peripheral artery disease or increased pro-BNP were uncommon, and without any sex differences. Unprotected subclinical CVD was very common, and medical treatment was intensified in 60% (95% CI:53–68) of patients. Conclusion: We propose a feasible cardiovascular screening examination from which middle-aged patients with diabetes may benefit. However, the participation rate may be too low to warrant screening.</p

Home-based Intervention with Semaglutide Treatment of Neuroleptic-Related Prediabetes (HISTORI):Protocol describing a prospective, randomised, placebo controlled and double-blinded multicentre trial

Introduction Subjects with schizophrenia have a 2-3 fold higher mortality rate than the general population and a reduced life expectancy of 10-20 years. Approximately one-third of this excess mortality has been attributed to obesity-related type 2 diabetes (T2D) and to cardiovascular disease. Glucagon-like peptide-1 (GLP-1) analogues increase satiety and delay gastric emptying, thereby reducing food intake and weight. GLP-1 analogues also exert beneficial effects on cardiovascular outcomes in high-risk patients with T2D. Our aim is to investigate whether 30 weeks add-on treatment with the GLP-1 analogue semaglutide can reduce HbA1c sufficiently to reverse pre-diabetes and the metabolic syndrome in overweight schizophrenic patients. Methods and analysis We will perform a 30 week, two-armed, multicentre, superiority, double-blinded, randomised trial investigating the effect of weekly injections of semaglutide versus placebo in mental health facilities in Region of Southern Denmark and Region of Zealand, Denmark. In total, 154 adults with schizophrenia spectrum disease, aged 18-60 years treated with second generation antipsychotic treatment, HbA1c 39-47 mmol/mol and body mass index &gt;27 kg/m 2 will be randomised to injections of 1.0 mg semaglutide or placebo. The primary outcome is changes in HbA1c. Secondary outcomes encompass metabolic measures, psychotic symptoms and quality of life. Exploratory outcomes encompass insulin sensitivity, cardiovascular risk profile, medication adherence, general well-being and physical activity. Ethics and dissemination This study will be carried out in accordance with the Declaration of Helsinki and Good Clinical Practice guidelines. This research has obtained approval from both the Danish Medicines Agency and The Regional Committees on Health Research Ethics for Southern Denmark. Trial registration number NCT05193578 European Clinical Trials Database Number (EudraCT) 2020-004374-22, Regional Ethical Committee number S-20200182.</p

Heritability and circulating concentrations of pregnancy-associated plasma protein-A and stanniocalcin-2 in elderly monozygotic and dizygotic twins

Introduction: Pregnancy-associated plasma protein-A (PAPP-A) is an IGF-activating enzyme suggested to influence aging-related diseases. However, knowledge on serum PAPP-A concentration and regulation in elderly subjects is limited. Therefore, we measured serum PAPP-A in elderly same-sex monozygotic (MZ) and dizygotic (DZ) twins, as this allowed us to describe the age-relationship of PAPP-A, and to test the hypothesis that serum PAPP-A concentrations are genetically determined. As PAPP-A is functionally related to stanniocalcin-2 (STC2), an endogenous PAPP-A inhibitor, we included measurements on STC2 as well as IGF-I and IGF-II. Methods: The twin cohort contained 596 subjects (250 MZ twins, 346 DZ twins), whereof 33% were males. The age ranged from 73.2 to 94.3 (mean 78.8) years. Serum was analyzed for PAPP-A, STC2, IGF-I, and IGF-II by commercial immunoassays. Results: In the twin cohort, PAPP-A increased with age (r=0.19; P&lt;0.05), whereas IGF-I decreased (r=-0.12; P&lt;0.05). Neither STC2 nor IGF-II showed any age relationship. When analyzed according to sex, PAPP-A correlated positively with age in males (r=0.18; P&lt;0.05) and females (r=0.25; P&lt;0.01), whereas IGF-I correlated inversely in females only (r=-0.15; P&lt;0.01). Males had higher levels of PAPP-A (29%), STC2 (18%) and IGF-I (19%), whereas serum IGF-II was 28% higher in females (all P&lt;0.001). For all four proteins, within-pair correlations were significantly higher for MZ twins than for DZ twins, and they demonstrated substantial and significant heritability, which after adjustment for age and sex averaged 59% for PAPP-A, 66% for STC2, 58% for IGF-I, and 52% for IGF-II. Discussion: This twin study confirms our hypothesis that the heritability of PAPP-A serum concentrations is substantial, and the same is true for STC2. As regards the age relationship, PAPP-A increases with age, whereas STC2 remains unchanged, thereby supporting the idea that the ability of STC2 to inhibit PAPP-A enzymatic activity decreases with increasing age.</p