Serum insulin-like growth factor-binding protein-2 levels and metabolic and cardiovascular risk factors in young adults and children born small for gestational age

IGF Signaling in the Heart in Health and Disease

One of the most vital processes of the body is the cardiovascular system's proper operation. Physiological processes in the heart are regulated by the balance of cardioprotective and pathological mechanisms. The insulin-like growth factor system (IGF system, IGF signaling pathway) plays a pivotal role in regulating growth and development of various cells and tissues. In myocardium, the IGF system provides cardioprotective effects as well as participates in pathological processes. This review summarizes recent data on the role of IGF signaling in cardioprotection and pathogenesis of various cardiovascular diseases, as well as analyzes severity of these effects in various scenarios.

Associations between Insulin-Like Growth Factor Binding Protein-2 and lipoprotein kinetics in men

Low circulating concentrations of insulin-like growth factor binding protein-2 (IGFBP-2) have been associated with dyslipidemia, notably with high triglyceride (TG) levels. However, the determinants by which IGFBP-2 influences lipoprotein metabolism, especially that of TG-rich lipoproteins (TRLs), are poorly understood. Here, we aimed to assess the relationships between IGFBP-2 levels and lipoprotein production and catabolism in human subjects. Fasting IGFBP-2 concentrations were measured in the plasma of 219 men pooled from previous lipoprotein kinetics studies. We analyzed production rate and fractional catabolic rates of TRLapoB-48, and LDL-, IDL-, and VLDLapoB-100 by multicompartmental modeling of l-[5,5,5-D3] leucine enrichment data after a 12 h primed constant infusion in individuals kept in a constant nutritional steady state. Subjects had an average BMI of 30 kg/m², plasma IGFBP-2 levels of 157 ng/ml, and TG of 2.2 mmol/l. After adjustments for age and BMI, IGFBP-2 levels were negatively associated with plasma TG (r = −0.29; P < 0.0001) and positively associated with HDL-cholesterol (r = 0.26; P < 0.0001). In addition, IGFBP-2 levels were positively associated with the fractional catabolic rate of VLDLapoB-100 (r = 0.20; P < 0.01) and IDLapoB-100 (r = 0.19; P < 0.05) and inversely with the production rate of TRLapoB-48 (r = −0.28; P < 0.001). These correlations remained statistically significant after adjustments for age, BMI, and the amount of fat given during the tracer infusion. These findings show that the association between low plasma IGFBP-2 and high TG concentrations could be due to both an impaired clearance of apoB-100-containing VLDL and IDL particles and an increased production of apoB-48-containing chylomicrons. Additional studies are necessary to investigate whether and how IGFBP-2 directly impacts the kinetics of TRL.

IGFBP-1 and IGFBP-2 are associated with a decreased pulse-wave velocity in young, healthy adults

Background and aims

In healthy, young adults we analyzed a panel of cardiovascular disease related proteins in plasma and compared them with the vascular health of the subjects. The aim was to identify proteins with a relationship to the early atherosclerotic process in healthy individuals.

Methods

We employed the proximity extension assay from OLINK proteomics to analyze 92 cardiovascular disease (CVD) related proteins on 833 subjects (men and women, ages 18–26). The women were further divided into an estrogen-using group and non-users. Protein expression was analyzed using principal component analysis (PCA). The following vascular examinations were performed: Pulse-wave velocity (PWV), augmentation index (AIX), carotid-intima media thickness (cIMT).

Results

Three principal components were obtained using PCA to analyze the protein expression. None of the obtained principal components correlated significantly with AIX or cIMT. One of the components, explaining 6% of the total variance of the data, was significantly correlated with PWV. Upon examination of the proteins with the highest factor loadings on this component independently in a multivariable model, adjusting for established CVD risk biomarkers, insulin-like growth factor-binding protein 1 (IGFBP-1) and insulin-like growth factor-binding protein 2 (IGFBP-2) were found to independently, negatively correlate with PWV. Among the established risk factors included in the multivariable model, age was significantly and adversely correlated with all vascular measurements.

Conclusions

In this population of healthy, young adults, groups of CVD related proteins correlate with PWV, but not AIX or cIMT. This group of proteins, of which IGFBP-1 and IGFBP-2 were independently, negatively correlated in a multivariable model with PWV, could have benificial effects on vascular stiffness. The robust association between age and PWV, AIX and cIMT provide insight into the impact of aging on the vasculature, which is detectable even in a population of young, healthy, non-smoking individuals of ages spanning only 8 years.

Supplementary information

The online version contains supplementary material available at 10.1186/s12872-021-01914-w.

Current Insights into the Role of the Growth Hormone-Insulin-Like Growth Factor System in Short Children Born Small for Gestational Age

BACKGROUND

The reason for the insufficient catch-up growth seen in 10% of children born small for gestational age (SGA) is poorly understood. Disturbances in the growth hormone (GH) - insulin-like growth factor (IGF) axis might underlie this failure to show sufficient catch-up growth.

CONCLUSION

This review summarizes insights gained in the molecular and (epi) genetic mechanisms of the GH-IGF axis in short children born SGA. The most notable anomalies of the IGF system are the lowered IGF-I levels in both cord blood and the placenta, and the increased expression of IGF-binding proteins (IGFBP)-1 and IGFBP-2, which inhibit IGF-I, in the placenta of SGA neonates. These observations suggest a decreased bioactivity of IGF-I in utero. IGF-I levels remain reduced in SGA children with short stature, as well as IGFBP-3 and acid-labile subunit levels. Proteolysis of IGFBP-3 appears to be increased.

MicroRNA-351 eases insulin resistance and liver gluconeogenesis via the PI3K/AKT pathway by inhibiting FLOT2 in mice of gestational diabetes mellitus

Gestational diabetes mellitus (GDM) is known as different degree glucose intolerance that is initially identified during pregnancy. MicroRNAs (miRs) may be a potential candidate for treatment of GDM. Herein, we suggested that miR‐351 could be an inhibitor in the progression of GDM via the phosphoinositide 3‐kinase/protein kinase B (PI3K/AKT) pathway. Microarray analysis was used to identify differentially expressed genes and predict miRs regulating flotillin 2 (FLOT2). Target relationship between miR‐351 and FLOT2 was verified. Gestational diabetes mellitus mice were treated with a series of mimic, inhibitor and small interfering RNA to explore the effect of miR‐351 on insulin resistance (IR), cell apoptosis in pancreatic tissues and liver gluconeogenesis through evaluating GDM‐related biochemical indexes, as well as expression of miR‐351, FLOT2, PI3K/AKT pathway‐, IR‐ and liver gluconeogenesis‐related genes. MiR‐351 and FLOT2 were reported to be involved in GDM. FLOT2 was the target gene of miR‐351. Gestational diabetes mellitus mice exhibited IR and liver gluconeogenesis, up‐regulated FLOT2, activated PI3K/AKT pathway and down‐regulated miR‐351 in liver tissues. Additionally, miR‐351 overexpression and FLOT2 silencing decreased the levels of FLOT2, phosphoenolpyruvate carboxykinase, glucose‐6‐phosphatase, fasting blood glucose, fasting insulin, total cholesterol, triglyceride, glyeosylated haemoglobin and homeostasis model of assessment for IR index (HOMA‐IR), extent of PI3K and AKT phosphorylation, yet increased the levels of HOMA for islet β‐cell function, HOMA for insulin sensitivity index and glucose transporter 2 expression, indicating reduced cell apoptosis in pancreatic tissues and alleviated IR and liver gluconeogenesis. Our results reveal that up‐regulation of miR‐351 protects against IR and liver gluconeogenesis by repressing the PI3K/AKT pathway through regulating FLOT2 in GDM mice, which identifies miR‐351 as a potential therapeutic target for the clinical management of GDM.

Changes in IGFBP-2 levels following a one-year lifestyle modification program are independently related to improvements in plasma apo B and LDL apo B levels

BACKGROUND AND AIMS

Recent transversal studies have associated insulin-like growth factor binding protein (IGFBP)-2 levels with glucose tolerance and parameters of the lipoprotein-lipid profile. Here, we aimed at determining the longitudinal effects of a one-year lifestyle modification program on IGFBP-2 levels and to identify specific metabolic improvements impacted by the changes in IGFBP-2.

METHODS

99 middle-aged Caucasian men were involved in a lifestyle modification program consisting in personalized healthy eating and physical activity counseling, combined to elicit a daily 500 kcal deficit. Anthropometric and metabolic parameters as well as circulating IGFBP-2 levels were measured before and after one year of the lifestyle modification program.

RESULTS

The intervention triggered positive changes in many metabolic parameters and a 43% (p < 0.0001) increase of IGFBP-2 levels. Subjects with the most substantial increases in IGFBP-2 also experienced the most important metabolic improvements. Changes in IGFBP-2 levels (both absolute and relative) were correlated with markers of body fat distribution and lipoprotein-lipid profile, and independently associated with changes in LDL apolipoprotein (apo) B but not VLDL apo B concentrations. Further analyses showed that for similar changes in BMI, waist circumference and visceral adipose tissue volume, large changes in IGFBP-2 levels were required to observe improvements in LDL apo B levels.

CONCLUSIONS

The 1-year lifestyle modification program was associated with increased IGFBP-2 concentrations. Increases in IGFBP-2 levels were closely associated with reduced LDL apo B concentrations and independently of the modifications in fat mass and insulin sensitivity. Further mechanistic studies are required to assess the effects of IGFBP-2 levels on LDL metabolism.

Role of IGF-binding proteins in regulating IGF responses to changes in metabolism

The IGF-binding protein family contains six members that share significant structural homology. Their principal function is to regulate the actions of IGF1 and IGF2. These proteins are present in plasma and extracellular fluids and regulate access of both IGF1 and II to the type I IGF receptor. Additionally, they have functions that are independent of their ability to bind IGFs. Each protein is regulated independently of IGF1 and IGF2, and this provides an important mechanism by which other hormones and physiologic variables can regulate IGF actions indirectly. Several members of the family are sensitive to changes in intermediary metabolism. Specifically the presence of obesity/insulin resistance can significantly alter the expression of these proteins. Similarly changes in nutrition or catabolism can alter their synthesis and degradation. Multiple hormones such as glucocorticoids, androgens, estrogen and insulin regulate IGFBP synthesis and bioavailability. In addition to their ability to regulate IGF access to receptors these proteins can bind to distinct cell surface proteins or proteins in extracellular matrix and several cellular functions are influenced by these interactions. IGFBPs can be transported intracellularly and interact with nuclear proteins to alter cellular physiology. In pathophysiologic states, there is significant dysregulation between the changes in IGFBP synthesis and bioavailability and changes in IGF1 and IGF2. These discordant changes can lead to marked alterations in IGF action. Although binding protein physiology and pathophysiology are complex, experimental results have provided an important avenue for understanding how IGF actions are regulated in a variety of physiologic and pathophysiologic conditions.

Clinical and biochemical characteristics and bone mineral density of homozygous, compound heterozygous and heterozygous carriers of three novel IGFALS mutations

OBJECTIVE

Acid-labile subunit (ALS) deficiency (ACLSD), caused by homozygous or compound heterozygous IGFALS mutations, is associated with moderate short stature, delayed puberty, low serum IGF-I and ALS and extremely low serum IGFBP-3. Its effect on birth weight, head circumference, bone mineral density (BMD), serum IGF-II and IGFBP-2 is uncertain, as well as the phenotype of heterozygous carriers of IGFALS mutations (partial ACLSD).

DESIGN

From all available members of five Turkish families, carrying three mutations in exon 2 of IGFALS (c.1462G > A, p.Asp488Asn (families A, B, E); c.251A > G, p.Asn84Ser (families C and E) and c.1477del, p.Arg493fs (family D)), clinical, laboratory and BMD data were collected.

METHODS

Auxological and biochemical findings were expressed as SDS for age and gender. Ternary complex formation in serum was investigated by size-exclusion chromatography. BMD using DXA bone densitometry was adjusted for height and age (Ha-BMD z-score).

RESULTS

In ACLSD (n = 24), mean ± s.d. height SDS (-2.7 ± 1.2), head circumference SDS (-2.3 ± 0.5) and body mass index (BMI) (-0.6 ± 1.0 SDS) were lower than those in partial ACLSD (n = 26, P ≤ 0.01) and birth weight SDS (n = 7) tended to be lower (-2.2 ± 1.1 vs -0.6 ± 0.3 in partial ACLSD (P = 0.07)). Serum IGF-I was -3.7 ± 1.4 vs -1.0 ± 1.0, IGF-II: -5.6 ± 0.7 vs -1.3 ± 0.7, ALS: <-4.4 ± 1.2 vs -2.1 ± 0.9 and IGFBP-3: -9.0 ± 1.9 vs -1.6 ± 0.8 SDS respectively (P < 0.001). Ha-BMD z-score was similar and normal in both groups.

CONCLUSIONS

To the known phenotype of ACLSD (i.e. short stature, reduced serum levels of IGF-I and ALS, extremely low serum IGFBP-3 and disturbed ternary complex formation), we add reduced birth weight, head circumference and serum IGF-II.

Early hypermethylation of hepatic Igfbp2 results in its reduced expression preceding fatty liver in mice

Obesity and ectopic fat disposition are risk factors for metabolic disease. Recent data indicate that IGFBP2 expression in liver is epigenetically inhibited during hepatic steatosis. The aim of this study was to investigate if epigenetic de-regulation of hepatic Igfbp2 occurs already early in life and is associated with increased risk for diet-induced obesity (DIO) during adolescence. Male C57BL/6J mice received a high-fat diet. After 3 weeks on this diet (age of 6 weeks), DIO-susceptible (responder, Resp) and DIO-resistant (non-responder, nResp) mice were identified by early weight gain. At the age of 6 weeks, Resp mice exhibited elevated blood glucose (p < 0.05), plasma insulin (p < 0.01), HOMA-IR and leptin/adiponectin ratio, whereas liver triglycerides were identical but significantly increased (p < 0.01) in Resp mice at 20 weeks of age. Igfbp2 expression was reduced in young Resp compared with nResp mice (p < 0.01), an effect that correlated with elevated DNA methylation of intronic CpG₂₆₀₅ (p < 0.01). The epigenetic inhibition of Igfbp2 was stable over time and preceded DIO and hepatosteatosis in adult mice. In vitro studies demonstrated that selective methylation of CpG₂₆₀₅ significantly reduced reporter activity by ∼85%, indicating that Igfbp2 expression is modulated by methylation. In human whole blood cells, methylation of IGFBP2 at the homologous CpG site was increased in obese men with impaired glucose tolerance. In conclusion, our data show that increased methylation of hepatic Igfbp2 during infancy predicts the development of fatty liver later in life and is linked to deterioration of glucose metabolism.

Physiology and pathophysiology of IGFBP-1 and IGFBP-2 - consensus and dissent on metabolic control and malignant potential

IGFBP-1 and IGFBP-2 are suppressed by growth hormone and therefore represent less prominent members of the IGFBP family when compared to IGFBP-3 that carries most of the IGFs during circulation under normal conditions in humans in vivo. As soon as the GH signal is decreased expression of IGF-I and IGFBP-3 is reduced. Under conditions of lowered suppression by GH the time seems come for IGFBP-1 and IGFBP-2. Both IGFBPs are potent effectors of growth and metabolism. Secretion of IGFBP-1 and IGFBP-2 is further suppressed by insulin and diminished with increasing obesity. Both IGFBP family members share the RGD sequence motif that mediates binding to integrins and is linked to PTEN/PI3K signalling. In mice, IGFBP-2 prevents age- and diet-dependent glucose insensitivity and blocks differentiation of preadipocytes. The latter function is modulated by two distinct heparin-binding domains of IGFBP-2 which are lacking in IGFBP-1. IGFBP-2 is further regulated by leptin and has been demonstrated to affect insulin sensitivity and glucose tolerance, further supporting a particular role of IGFBP-2 in glucose and fat metabolism. Since IGFBP-2 is controlled by sex steroids as well, we devised a scheme to compare IGFBP effects in breast, ovarian and prostate cancer. While a positive association does not seem to exist with IGFBP-1 and risk of cancers within these reproductive tissues, a relationship between IGFBP-2 and breast cancer, ovarian cancer and prostate cancer does indeed appear to be present. To date, the specific roles of IGFBP-2 in estrogen signalling are unclear, though there is accumulating evidence for an effect of IGFBP-2 on PI3K signalling via PTEN, particularly in breast cancer.

The RGD sequence present in IGFBP-2 is required for reduced glucose clearance after oral glucose administration in female transgenic mice

Recent studies suggest that insulin-like growth factor-binding protein-2 (IGFBP-2) affects both growth and metabolism. Whereas negative growth effects are primarily due to negative interference with IGF-I, the mechanisms for metabolic interference of IGFBP-2 are less clear. As we demonstrate, overexpression of IGFBP-2 in transgenic mice is correlated with a decelerated clearance of blood glucose after oral administration. IGFBP-2 carries an integrin-binding domain (RGD motif), which has been shown to also mediate IGF-independent effects. We thus asked if higher serum levels of IGFBP-2 without an intact RGD motif would also partially block blood glucose clearance after oral glucose application. In fact, transgenic mice overexpressing mutated IGFBP-2 with higher levels of IGFBP-2 carrying an RGE motif instead of an RGD were not characterized by decelerated glucose clearance. Impaired glucose tolerance was correlated with lower levels of GLUT4 present in plasma membranes isolated from muscle tissues after glucose challenge. At the same time, activation of TBC1D1 was depressed in mice overexpressing wild-type but not mutated IGFBP-2. Although we do not have reason to assume altered activation of IGF-I receptor or PDK1/Akt activation in both models, we have identified increased levels of integrin-linked kinase and focal adhesion kinase dependent on the presence of the RGD motif. From our results we conclude that impaired glucose clearance in female IGFBP-2 transgenic mice is dependent on the presence of the RGD motif and that translocation of GLUT4 in the muscle may be regulated by IGFBP-2 via RGD-dependent mechanisms.

Quantitative analysis of the concentrations of IGFs and several IGF-binding proteins in a large fibrous abdominal tumor and the circulation of a patient with hypoglycemia

The syndrome of nonislet cell tumor induced hypoglycemia (NICTH) represent extreme cases of excessive expression and production of incompletely processed high-molecular-mass pro-IGF-II forms (big IGF-II) by an often large tumor. Tumor-derived big IGF-II is responsible for enhanced insulin-like effects in the body through complicated mechanisms, leading to hypoglycemia. Case studies on NICTH usually focus on measurements of diagnostic parameters in the circulation of patients. Some studies have also reported on qualitative immunohistochemical analysis of tumor tissue, in particular with respect to the expression of IGF-II at the mRNA or protein level. However, quantitative data on the concentrations of IGFs and IGFBPs in tumor specimen causing NICTH, in relation to their corresponding plasma levels are lacking. Such an analysis would provide an estimate of the total potential of (big) IGF-II retained by the tumor and more insight in the relative levels of different IGFBPs and their origin in the circulation, that is, systemically induced by tumor related factors or directly tumor-derived. Here we investigated quantitatively the levels of IGFs and IGFBPs in a large, 1.76 kg weighing, solitary fibrous tumor from a typical case of NICTH using highly specific immunometric assays. Besides a high level of big IGF-II, patient's plasma also contained increased levels of both IGFBP-2 and -6 which declined after removal of the tumor. These IGFBPs have a higher affinity for (pro-) IGF-II than IGF-I and exhibit intrinsic IGF-independent bioactivities. Tumor tissue contained high amounts of big IGF-II and IGFBP-6, exceeding that in patient's circulation many-fold. A relatively low tumor content of IGFBP-2 was found suggesting that the preoperative high levels in plasma were attributable to systemic mechanisms. The background literature and possible implications of these findings are briefly discussed. Based on the present results we postulate that tumor tissue is not the source of the elevated levels of IGFBP-2 often seen in NICTH patients. Large tumors that cause NICTH can produce IGFBP-6 leading to enhanced levels of this IGFBP in the circulation. Hence, the measurement of IGFBP-6 in plasma may serve as an additional marker of this disease pattern.

IGFBP-2 - taking the lead in growth, metabolism and cancer

The activity of the Insulin-like Growth Factors (IGFs) ligands elicited via their receptors and transduced by various intracellular signal pathways is modulated by the IGF Binding Proteins (IGFBPs). Among all the IGFBPs, IGFBP-2 has been implicated in the regulation of IGF activity in most tissue and organs. Besides binding to IGFs in the circulation these IGF-regulatory activities of IGFBP-2 involve interactions with components of the extracellular matrix, cell surface proteoglycans and integrin receptors. In addition to these local peri-cellular activities, IGFBP-2 exerts other key functions within the nucleus, where IGFBP-2 directly or indirectly promotes transcriptional activation of specific genes. All of these IGFBP-2 activities, intrinsic or dependent on IGFs, contribute to its functional roles in growth/development, metabolism and malignancy as evidenced by studies in IGFBP-2 animal models and also by many in vitro studies. Finally, preclinical studies have demonstrated that IGFBP-2 administration can be beneficial in improving metabolic responses (inhibition of adipogenesis and enhanced insulin sensitivity), while blockade of IGFBP-2 appears to be an effective approach to inhibiting tumour growth and metastasis.

Circulating IGFBP-2 levels are incrementally linked to correlates of the metabolic syndrome and independently associated with VLDL triglycerides

OBJECTIVE

To assess whether plasma IGFBP-2 is independently associated with components of the lipoprotein-lipid profile and to suggest a cutoff value that could identify subjects with the features of the metabolic syndrome.

METHODS

In this cross-sectional study, 379 Caucasian men from the general population and covering a wide range of BMI were recruited through the media. Subjects with type 2 diabetes, BMI values > 40 kg/m(2), or taking medication targeting glucose or lipid metabolism or blood pressure were excluded. Anthropometric data were collected and plasma IGFBP-2 concentrations, glucose tolerance and an extensive plasma lipid profile were determined after an overnight fast.

RESULTS

Subjects with low IGFBP-2 levels were characterized by increased fat mass (p < 0.0001), impaired insulin sensitivity (p < 0.0001) and higher plasma triglyceride (TG) levels (p < 0.0001). When divided into 6 quantiles, only subjects with the highest IGFBP-2 levels (>221.5 ng/mL) did not meet the NCEP ATP III criteria for the clinical diagnosis of the metabolic syndrome. In addition, circulating IGFBP-2 levels were significantly associated with VLDL-TG (r = -0.51, p < 0.0001) and HDL-C (r = -0.27, p < 0.0001) levels. After adjustments, plasma IGFBP-2 was found to be independently associated with VLDL-TG levels but not with HDL-C concentrations.

CONCLUSIONS

In our cohort, IGFBP-2 levels <221.5 ng/mL are incrementally associated with a detrimental plasma lipoprotein-lipid profile. After adjustment for covariates, IGFBP-2 remained independently associated with VLDL-TG but not HDL-C levels. This study supports further investigations in other populations and validation of IGFBP-2 as a biomarker of early dyslipidemia.

Preterm birth and subsequent insulin sensitivity: a systematic review

OBJECTIVE

The incidence of preterm birth is increasing worldwide. Evidence suggests that in later life these children are at increased risk of 'metabolic syndrome', which is itself associated with reduced insulin sensitivity (IS). We carried out a systematic review to examine whether preterm birth is associated with later changes in IS and whether a difference exists between those born small-for-gestational age (SGA) and appropriate-for-gestational age (AGA).

METHODS

We used the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidance to structure our review with a priori data extraction criteria to answer the questions posed and then carried out our literature search. Only papers which included preterm infants in their study population and specifically assessed IS were included. Findings are reported by age group to enable change over the life course to be examined, even though the studies were mostly cross-sectional, observation studies.

RESULTS

We identified and reviewed 26 suitable publications representing 20 separate cohorts, of which 16 had a term control group. The heterogeneity of the methods used to measure IS precluded meta-analysis. In infancy and early childhood there is a measurable association between IS and preterm birth. In later childhood and adulthood the strength of this association reduces, and current body composition becomes the variable most strongly associated with IS.

CONCLUSIONS

There is an association between preterm birth and IS throughout the life course, but the data are conflicting and associations are likely to be affected by the heterogeneity of each study population and multiple confounding factors that may change over time. While the optimal nutritional strategy for preterm infants remains to be determined, standard public health guidance to avoid obesogenic lifestyle factors remains equally important to individuals born preterm.

The heparin-binding domains of IGFBP-2 mediate its inhibitory effect on preadipocyte differentiation and fat development in male mice

IGF-binding protein (IGFBP)-2 overexpression confers resistance to high-fat feeding and inhibits the differentiation of preadipocytes in vitro. However, whether administration of IGFBP-2 can regulate adipogenesis in vivo and the domains that mediate this response have not been defined. IGFBP-2 contains 2 heparin-binding domains (HBD), which are localized in the linker region (HBD1) and C-terminal region (HBD2) of IGFBP-2. To determine the relative importance of these domains, we used synthetic peptides as well as mutagenesis. Both HBD1 and HBD2 peptides inhibited preadipocyte differentiation, but the HBD2 peptide was more effective. Selective substitution of charged residues in the HBD1 or HBD2 regions attenuated the ability of the full-length protein to inhibit cell differentiation, but the HBD2 mutant had the greatest reduction. To determine their activities in vivo, pegylated forms of each peptide were administered to IGFBP-2(-/-) mice for 12 weeks. Magnetic resonance imaging scanning showed that only the HBD2 peptide significantly reduced (48 ± 9%, P < .05) gain in total fat mass. Both inguinal (32 ± 7%, P < .01) and visceral fat (44 ± 7%, P < .01) were significantly decreased by HBD2 whereas HBD1 reduced only visceral fat accumulation (24 ± 5%, P < .05). The HBD2 peptide was more effective peptide in reducing triglyceride content and serum adiponectin, but only the HBD2 peptide increased serum leptin. These findings demonstrate that the HBD2 domain of IGFBP-2 is the primary region that accounts for its ability to inhibit adipogenesis and that a peptide encompassing this region has activity that is comparable with native IGFBP-2.

Effects of cord serum insulin, IGF-II, IGFBP-2, IL-6 and cortisol concentrations on human birth weight and length: pilot study

BACKGROUND

The IGF system is recognised to be important for fetal growth. We previously described increased Insulin-like growth factor binding protein (IGFBP)-2 cord serum concentrations in intra-uterine growth retardation (IUGR) compared with appropriate for gestational age (AGA) newborns, and a positive relationship of IGFBP-2 with Interleukin (IL)-6. The role of cortisol in the fetus at birth is largely unknown, and interactions among peptides are their real effect on birth size is unknown. Furthermore, almost all studies have previously assayed peptides in serum several years after birth, and follow-up data from pregnancy are always lacking. This study aimed at establishing and clarifying the effect of cord serum insulin, IGF-II, IGFBP-2, cortisol and IL-6 concentrations on birth length and weight.

METHODS

23 IUGR and 37 AGA subjects were followed up from the beginning of pregnancy, and were of comparable gestational age. Insulin, IGF-II, IGFBP-2, cortisol and IL-6 concentrations were assayed in cord serum at birth, and a multiple regression model was designed and applied to assess which were the significant biochemical determinants of birth size.

RESULTS

Insulin, cortisol, and IL-6, showed similar concentrations in IUGR and AGA as previously described, whereas IGF-II was lower, and IGFBP-2 increased in IUGR compared with AGA. IGF-II serum concentration was found to have a significant positive effect on both birth length (r:(:)0.546; p: 0.001) and weight (r:0.679; p: 0.0001). IGFBP-2 had a near significant negative effect on both birth weight (r:-0.342; p: 0.05) and length (r:-0.372; p:0.03).

CONCLUSION

IGF-II cord serum concentration was shown to have a significant positive effect on both birth length and weight, whereas IGFBP-2 had a significant negative effect. Insulin, cortisol, and IL-6 cord serum concentrations had no significant effect on birth size.