Associations of adiposity from childhood into adulthood with insulin resistance and the insulin-like growth factor system: 65-year follow-up of the Boyd Orr Cohort

Maternal obesity and acute lymphoblastic leukemia risk in offspring: A summary of trends, epidemiological evidence, and possible biological mechanisms

Acute lymphoblastic leukemia, a heterogenous malignancy characterized by uncontrolled proliferation of lymphoid progenitors and generally initiated in utero, is the most common pediatric cancer. Although incidence of ALL has been steadily increasing in recent decades, no clear reason for this trend has been identified. Rising concurrently with ALL incidence, increasing maternal obesity rates may be partially contributing to increasing ALL prevelance. Epidemiological studies, including a recent meta-analysis, have found an association between maternal obesity and leukemogenesis in offspring, although mechanisms underlying this association remain unknown. Therefore, the purpose of this review is to propose possible mechanisms connecting maternal obesity to ALL risk in offspring, including changes to fetal/neonatal epigenetics, altered insulin-like growth factor profiles and insulin resistance, modified adipokine production and secretion, changes to immune cell populations, and impacts on birthweight and childhood obesity/adiposity. We describe how each proposed mechanism is biologically plausible due to their connection with maternal obesity, presence in neonatal and/or fetal tissue, observation in pediatric ALL patients at diagnosis, and association with leukemogenesis, A description of ALL and maternal obesity trends, a summary of epidemiological evidence, a discussion of the pathway from intrauterine environment to subsequent malignancy, and propositions for future directions are also presented.

Early-Life Body Adiposity and the Breast Tumor Transcriptome

BACKGROUND

Cumulative epidemiologic evidence has shown that early-life adiposity is strongly inversely associated with breast cancer risk throughout life, independent of adult obesity. However, the molecular mechanisms remain poorly understood.

METHODS

We assessed the association of early-life adiposity, defined as self-reported body size during ages 10-20 years from a validated 9-level pictogram, with the transcriptome of breast tumor (N = 835) and tumor-adjacent histologically normal tissue (N = 663) in the Nurses' Health Study. We conducted multivariable linear regression analysis to identify differentially expressed genes in tumor and tumor-adjacent tissue, respectively. Molecular pathway analysis using Hallmark gene sets (N = 50) was further performed to gain biological insights. Analysis was stratified by tumor estrogen receptor (ER) protein expression status (n = 673 for ER+ and 162 for ER- tumors).

RESULTS

No gene was statistically significantly differentially expressed by early-life body size after multiple comparison adjustment. However, pathway analysis revealed several statistically significantly (false discovery rate < 0.05) upregulated or downregulated gene sets. In stratified analyses by tumor ER status, larger body size during ages 10-20 years was associated with decreased cellular proliferation pathways, including MYC target genes, in both ER+ and ER- tumors. In ER+ tumors, larger body size was also associated with upregulation in genes involved in TNFα/NFkB signaling. In ER- tumors, larger body size was additionally associated with downregulation in genes involved in interferon α and interferon γ immune response and Phosphatidylinositol 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) signaling; the INFγ response pathway was also downregulated in ER- tumor-adjacent tissue, though at borderline statistical significance (false discovery rate = 0.1).

CONCLUSIONS

These findings provide new insights into the biological and pathological underpinnings of the early-life adiposity and breast cancer association.

The Neglected Insulin: IGF-II, a Metabolic Regulator with Implications for Diabetes, Obesity, and Cancer

When originally discovered, one of the initial observations was that, when all of the insulin peptide was depleted from serum, the vast majority of the insulin activity remained and this was due to a single additional peptide, IGF-II. The IGF-II gene is adjacent to the insulin gene, which is a result of gene duplication, but has evolved to be considerably more complicated. It was one of the first genes recognised to be imprinted and expressed in a parent-of-origin specific manner. The gene codes for IGF-II mRNA, but, in addition, also codes for antisense RNA, long non-coding RNA, and several micro RNA. Recent evidence suggests that each of these have important independent roles in metabolic regulation. It has also become clear that an alternatively spliced form of the insulin receptor may be the principle IGF-II receptor. These recent discoveries have important implications for metabolic disorders and also for cancer, for which there is renewed acknowledgement of the importance of metabolic reprogramming.

Serum IGF-binding protein 2 (IGFBP-2) concentrations change early after gastric bypass bariatric surgery revealing a possible marker of leptin sensitivity in obese subjects

PURPOSE

Expression of IGFBP-2 in mice is regulated by leptin. Over-expression of IGFBP-2 is associated with reduced caloric intake and resistance to weight gain. Hormonal variations contributing to weight loss occur very early after bariatric surgery but have not been fully elucidated. We evaluated IGFBP-2 serum changes after bariatric surgery and their relationship with leptin variations to test the hypothesis that an increase of leptin sensitivity may explain some of the effects of gastric bypass.

METHODS

This is a historical prospective study. Fifty-one obese patients (41 women e 10 men), 9 non-obese surgical controls and 41 lean matched controls were studied. Serum IGFBP-2 and leptin were measured after bariatric bypass surgery at various time points up to 18 months, after non-bariatric laparoscopic surgery in a control group, and in lean matched controls.

RESULTS

Compared to lean controls, serum IGFBP-2 levels were lower in obese patients. After gastric bypass, IGFBP-2 significantly increased at 3 days and became normal before the occurrence of relevant changes in body weight, remaining stable up to 18 months after surgery. IGFBP-2/leptin ratio increased early after surgery and became normal after one year.

CONCLUSIONS

After gastric bypass, serum IGFBP-2 increases in a window of time when variations of hormones mediating the effects of bariatric surgery occur. Our results suggest that IGFBP-2, a leptin-regulated protein, may be an in-vivo marker of leptin action. If this is the case, an early improvement of leptin sensitivity might contribute to the anorectic effect of gastric bypass.

Insulin-Like Growth Factor Binding Protein 2 (IGFBP-2) and the Risk of Developing Type 2 Diabetes

Recent studies suggest that insulin-like growth factor binding protein 2 (IGFBP-2) may protect against type 2 diabetes, but population-based human studies are scarce. We aimed to investigate the prospective association of circulating IGFBP-2 concentrations and of differential methylation in the IGFBP-2 gene with type 2 diabetes risk.

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.

Insulin-like growth factor-II in adipocyte regulation: depot-specific actions suggest a potential role limiting excess visceral adiposity

The IGF system has an important role in growth and development. IGF-II is a recognized fetal growth promoter. However, its physiological postnatal role remains uncertain, although it is maintained in the circulation at a substantially high level throughout life. IGF-II has been strongly linked to obesity in genetic studies, and more recent evidence suggests a metabolic role. We examined fat depot differences in IGF-II's action on differentiation and metabolism. We speculate a specific effect on visceral adipocytes in relation to the differential distribution of insulin receptors between visceral and subcutaneous fat depots. We used a previously established adipocyte, cell culture system of matched pairs of visceral and subcutaneous fat biopsies from 20 normal weight children undergoing routine surgery for nonmalignant, nonseptic conditions. Preadipocytes were differentiated for 14 days in the presence or absence of IGF-II. Oil Red O staining, Western blotting, and reverse transcription polymerase chain reaction techniques were employed to assess levels of adipogenesis markers and levels of the insulin receptor and insulin receptor isoforms. Our data indicate that IGF-II promotes preadipocyte differentiation in subcutaneous preadipocytes but showed a protective, opposing effect restricting visceral preadipocyte differentiation, confirmed by reductions in the differentiation markers peroxisome proliferator-activated receptor gamma and adiponectin and in triglyceride staining. Additionally, IGF-II reduced mRNA expression of the insulin receptor in adipocytes and downregulated insulin receptor isoform A and glucose transporter 4 abundance and corresponding glucose uptake in visceral adipocytes. In conclusion, IGF-II is a regulator of preadipocyte differentiation and metabolism by acting as a differential modulator of fat accumulation favoring less visceral fat deposition in children.

Serum IGFBP-2 and Risk of Atypical Hyperplasia of the Breast

Atypical hyperplasia of the breast (AH) is associated with increased risk of subsequent invasive breast cancer, yet little is known about the etiology of AH. Insulin-like growth factor binding protein 2 (IGFBP-2) may contribute to the development of AH due to its proliferative effects on mammary tissue. We conducted a nested case-control study of postmenopausal women enrolled in Women's Health Initiative-Clinical Trial. Cases were 275 women who developed incident AH during follow-up, individually (1 : 1) matched to controls. Levels of IGFBP-2 were determined from fasting serum collected at baseline. Multivariable conditional logistic regression models were used to estimate odds ratios for the association of IGFBP-2 with risk of AH. Serum IGFBP-2 was associated with a nonsignificant decrease in risk for AH, when comparing the highest quartile to lowest quartile (OR = 0.65; 95% CI = 0.32–1.31). This decrease in risk was most evident when analyses were restricted to nondiabetic, nonusers of hormone therapy (OR = 0.33, 95% CI = 0.13–0.86, p_trend = 0.06) and nondiabetic women who were overweight or obese (OR = 0.43, 95% CI = 0.18–1.03, p_trend = 0.05). Results from this study provide some support for an inverse association between serum IGFBP2 levels and risk of AH, particularly in nondiabetic women who are overweight or obese. Further studies are required to confirm these results.

The association of plasma IGF-I with dietary, lifestyle, anthropometric, and early life factors in postmenopausal women

OBJECTIVE

Higher circulating concentrations of insulin like growth factor (IGF-I) are associated with an increased risk of breast cancer. The objective of this study was to investigate associations between circulating IGF-I concentrations and dietary factors (intakes of protein, dairy protein, and alcohol), lifestyle factors (smoking and HT use), anthropometric indices (height and adiposity) and factors in early life (birth weight, having been breastfed, body size at age 10, and at age 20) in postmenopausal women in the UK.

DESIGN

An analysis of plasma IGF-I concentrations (measured by immunoassay) in 1883 postmenopausal women. Multivariate analysis was used to examine correlates of plasma IGF-I concentrations.

RESULTS

Women in the highest quintile of total protein and dairy protein intakes had, respectively, 7.6% and 5.5% higher plasma IGF-I concentrations than women in the lowest quintile (p trend <0.05 for both). Other factors significantly (p<0.05) associated with reduced IGF-I concentrations were: consuming 14 or more vs 3-7 alcoholic drinks per week (8.8% lower IGF-I); current vs non-current HT users (9.9% lower IGF-I); current use of oestrogen alone vs oestrogen+progestagen (16.9% lower IGF-I); obese vs overweight (6.8% lower IGF-I); and women who reported wearing larger vs smaller clothes sizes at age 20 (4.9% lower IGF-I).

CONCLUSIONS

This study in post-menopausal women identified several potentially modifiable determinants of circulating IGF-I concentrations. There is now strong evidence from this and other studies that IGF-I concentrations are associated with dietary protein intakes.

Changes in insulin-like growth factor-I and -II associated with fat but not lean mass in early old age

OBJECTIVE

To test the hypothesis that insulin-like growth factors-I and II (IGF-I and II) decline during late midlife and that greater declines are related to higher fat mass and lower lean mass.

METHODS

A total of 1,542 men and women in a British birth cohort study had IGF-I and II measured by immunoassay of blood samples at age 53 and/or 60-64 years. Fat mass, android:gynoid fat ratio, and appendicular lean mass were measured at 60-64 years using dual-energy X-ray absorptiometry (DXA). Associations between changes in IGF-I or II and body composition outcomes were examined using conditional change linear regression models.

RESULTS

Mean IGF-I and IGF-II concentrations were lower at 60-64 than at 53 years, by 12.8% for IGF-I and by 12.5% for IGF-II. Larger declines in either IGF-I or II were associated with higher fat mass at 60-64 years. Although higher IGF-I at 53 years was associated with higher lean mass, there was little evidence linking changes in IGF-I or II to lean mass.

CONCLUSIONS

The findings suggest that IGF-I and II concentrations decline with age, and greater declines are associated with higher fat mass levels. These results provide some evidence for the suggested roles of IGF-I and II in regulating fat mass but not lean mass in older age.

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.

Interplay between polymorphisms and methylation in the H19/IGF2 gene region may contribute to obesity in Mexican-American children

Imprinted genes often affect body size-related traits such as weight. However, the association of imprinting with obesity, especially childhood obesity, has not been well studied. Mexican-American children have a high prevalence, approaching 50%, of obesity and/or overweight. In a pilot study of 75 Mexican-American children, we analyzed the relationships among obese/overweight status, methylation status and single-nucleotide polymorphism (SNP) status at a CpG site in a differentially methylated region (DMR) of the imprinted H19/IGF2 locus. We observed a significant difference in SNP rs10732516 frequency between boys and girls among the overweight and obese children but not among the lean children. We also found that children with lower methylation of the polymorphic CpG site (CpG4) in the H19 DMR had higher birth weights than did children with higher methylation (P = 0.04). Our results suggest that CpG4 methylation status may be associated with childhood obesity in Mexican-American children in a sex-specific manner.

Childhood obesity: the impact on long-term risk of metabolic and CVD is not necessarily inevitable

The worldwide prevalence of overweight and obesity in the adult population is estimated to be 35 %. These trends are reflected in childhood obesity prevalence, and the potential impact of early-onset obesity is of great concern. The aim of this review was to investigate the long-term implications of childhood obesity for metabolic and cardiovascular health, focusing on the independent contribution of childhood obesity to adult disease risk, as distinct from associations mediated by tracking of obesity across the lifespan. The data systematically reviewed provide little evidence to suggest that childhood overweight and obesity are independent risk factors for metabolic and cardiovascular risk during adulthood. Instead, the data demonstrate that the relationships observed are dependent on tracking of BMI between childhood and adulthood, alongside persistence of dietary patterns and physical activity. Adjustment for adult BMI uncovers unexpected negative associations between childhood BMI and adult disease, suggesting a protective effect of childhood obesity at any given level of adult BMI. Further work is required to explain these findings, both in terms of pathways and statistical artefacts. To conclude, it must be stressed that it is not suggested that childhood obesity is without negative consequence. Childhood obesity is clearly associated with a range of adverse physical and psychological outcomes. However, the data are important in supporting a positive message that the long-term consequences of childhood obesity are avoidable; and that there remains opportunity for intervention across the lifespan. This nuance in understanding long-term risk is important when considering the effectiveness of interventions at different stages of the lifespan.

Maternal nutritional history modulates the hepatic IGF-IGFBP axis in adult male rat offspring

Alterations in early life nutrition lead to an increased risk of obesity and metabolic syndrome in offspring. We have shown that both relative maternal undernutrition (UN) and maternal obesity result in metabolic derangements in offspring, independent of the postnatal dietary environment. Since insulin-like growth factor binding protein 2 (IGFBP2) has been shown to be independently associated with obesity and diabetes risk, we examined the IGF-IGFBP axis in male rat offspring following either maternal UN or maternal obesity to explain possible common pathways in the development of metabolic disorders. Wistar rats were time-mated and fed either a control diet (CONT), 50 % of CONT (UN) or a high-fat (HF) diet throughout pregnancy. Male offspring were weaned onto a standard chow diet and blood and tissues were collected at postnatal day 160. Plasma and hepatic tissue samples were analysed for key players in the IGF-IGFBP system. Both maternal UN and HF resulted in increased fat mass, hyperinsulinemia, hyperleptinemia and altered blood lipid profiles in offspring compared to CONT. Circulating IGF-1 and IGFBP3 levels and hepatic mRNA expression of IGFBP1 and IGFBP2 were significantly decreased in UN and HF offspring compared to CONT. DNA methylation of the IGFBP2 promotor region was similar between maternal dietary groups. Although chaperone gene heat-shock protein 90 and hepatic IGFBP1 were significantly correlated in CONT offspring this effect was absent in both UN and HF offspring. In conclusion, this study is one of the first to directly compare two experimental models of developmental programming representing both ends of the maternal dietary spectrum. Our data suggest that two disparate nutritional models that elicit similar adverse metabolic phenotypes in offspring are characterised by common alterations in the IGF-IGFBP pathway.

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.

Hyperglycaemia-induced chemoresistance of prostate cancer cells due to IGFBP2

Clinically relevant prostate cancer (PCa) is more frequent in Westernised societies and increasingly men have co-morbidities associated with a Western lifestyle, primarily diabetes, characterised by hyperinsulinaemia and hyperglycaemia. IGFs and their binding proteins (IGFBPs) are important mediators of the effects of nutrition on growth and play a key role in the development of PCa. We used DU145, PC3 and LNCaP PCa cell lines to examine how hyperglycaemia altered their response to docetaxel. Trypan Blue dye-exclusion assay was used to determine the percentage of cell death. Protein abundance was determined using western immunoblotting. Levels of IGFBP2 were measured using an ELISA. IGFBP2 gene silencing was achieved using siRNA technology. DNA methylation was assessed using combined bisulphide restriction analysis. Acetylation status of histones H3 and H4 associated with IGFBP2 gene was assessed using chromatin immunoprecipitation assay. Hyperglycaemia reduced docetaxel-induced apoptosis by 40% for DU145 cells and by 88% for LNCaP cells. This reduced cell death was mediated by a glucose-induced up-regulation of IGFBP2, as silencing IGFBP2 negated the survival effect of high glucose. Glucose increased IGFBP2 via increasing the acetylation of histones associated with the IGFBP2 gene promoter. This finding could have important implications in relation to therapeutic strategies as epigenetic modulation could be reversible.

Prenatal low-protein and postnatal high-fat diets induce rapid adipose tissue growth by inducing Igf2 expression in Sprague Dawley rat offspring

Maternal low-protein diets result in lower birth weight followed by accelerated catch-up growth that is accompanied by the development of obesity and glucose intolerance in later life. Whether postnatal high-fat (HF) diets further contribute to the development of obesity and insulin resistance in offspring by affecting adipose tissue metabolism and DNA methylation is currently unknown. Obese-prone Sprague-Dawley rats were fed 8% low protein (LP) or 20% normal protein diets for 3 wk prior to conception and throughout pregnancy and lactation to investigate whether prenatal LP and postnatal HF diets affect the rate of adipose tissue growth, insulin-like growth factor 2 (Igf2) expression, and DNA methylation in male offspring. At weaning, the offspring were fed 10% normal fat or 45% HF diets for 12 wk. The adipose tissue growth rate was increased (up to 26-fold) by the LP prenatal and HF postnatal diets. Adipose tissue Igf2 mRNAs and DNA methylation were increased by the LP prenatal and HF postnatal diets. The LP prenatal and HF postnatal diet increased the number of small adipocytes in adipose tissue and decreased insulin sensitivity. These findings suggest that prenatal LP and postnatal HF intake result in adipose tissue catch-up growth through alterations in the expression of the Igf2 gene and DNA methylation within adipocytes. These alterations in adiposity are accompanied by an increased risk of development of type 2 diabetes.

The maternal womb: a novel target for cancer prevention in the era of the obesity pandemic?

The dramatic rise in worldwide prevalence of obesity has necessitated the search for more efficacious antiobesity strategies to counter the increased cancer risks in overweight and obese individuals. The mechanistic pathways linking obesity status with adult chronic diseases such as cancer remain incompletely understood. A growing body of evidence suggests that novel approaches and interventional agents to disrupt the feed-forward cycle of maternal to offspring obesity transfer that is initiated in utero will be important for stemming both the obesity pandemic and the associated increase in cancer incidence. The convergence of multiple research areas including those encompassing the insulin and insulin-like growth factor systems, epigenetics, and stem cell biology is providing insights into the potential for cancer prevention in adult offspring previously exposed to the intrauterine environment of overweight/obese mothers. Here, we review the current state of this nascent research field, with a focus on three major cancers, namely breast, colorectal, and liver, and suggest some possible future directions to optimize its impact for the health of future generations.

Insulin stimulates IGFBP-2 expression in 3T3-L1 adipocytes through the PI3K/mTOR pathway

Insulin-like growth factor binding protein 2 (IGFBP-2) has been implicated in the etiology of several diseases, including the metabolic syndrome. Although IGFBP-2 derives mostly from the liver, recent evidence in mice and humans indicate that aging and obesity are associated with altered IGFBP-2 levels in white adipocytes. The present study was aimed at determining the mechanisms that control IGFBP-2 expression in mature adipocytes. IGFBP-2 mRNA and protein expression in serum-deprived 3T3-L1 adipocytes were twofold increased by acute insulin treatment. Co-treatments with the phosphatidylinositol 3-kinase (PI3K) inhibitor wortmannin or the mammalian target of rapamycin (mTOR) inhibitor rapamycin blunted the effects of insulin. Coherently, IGFBP-2 mRNA levels were robustly increased in adipocytes lacking either TSC2 or 4E-BP1. Insulin triggered the recruitment of CAAT/enhancer binding protein α (C/EBPα) to the IGFBP-2 proximal promoter. These findings suggest that insulin upregulates IGFBP-2 expression through a PI3K/mTOR/C/EBPα pathway in white adipocytes.

Upregulation of plasma insulin-like growth factor binding protein 2 levels after biliopancreatic diversion in humans

The biliopancreatic diversion surgery with duodenal switch (BPD-DS) is a surgical procedure that not only induces significant weight loss, but also promotes remission of diabetes. However, the mechanism responsible for this insulin-potentiating effect (both on sensitivity and production) is not yet clearly understood. The insulin-like growth factor (IGF) binding protein 2 (IGFBP-2) is a 36 kDa circulating protein that has been recently suggested to modulate insulin sensitization and fat accumulation. In humans, a low-circulating concentration of IGFBP-2 has been associated with obesity and insulin resistance. We thus tested the hypothesis that BPD-DS would trigger an increase in IGFBP-2 levels. Plasma IGFBP-2 was quantified by enzyme-linked immunosorbent assay in 77 severely obese men and women before and up to 1 year after BPD-DS surgery. Baseline IGFBP-2 levels were 159 ± 17 ng/ml. Plasma IGFBP-2 levels increased significantly as soon as 24 h after BPD-DS surgery and were further augmented at both 6 months and 1 year after the surgery, reaching 748 ± 65 ng/ml. Changes in IGFBP-2 concentrations were significantly and negatively associated with blood glucose, insulin, triglycerides, and total cholesterol levels. The present findings suggest that the rise in IGFBP-2 levels is associated with the improvements in glucose and lipid metabolism in the short- and long-term after BPD-DS. The mechanisms for the augmentation in IGFBP-2 after BPD-DS and its contribution to insulin sensitization remain to be elucidated.

Insulin-like growth factor physiology: what we have learned from human studies

Although very similar to insulin and its receptor; the modus operandi of the insulin-like growth factors (IGFs) within the body is very different from that of the traditional peptide hormone. The IGF-binding proteins bind the IGFs with greater affinity than the cell surface receptors, enabling them to tightly control tissue activity. In addition to their role in fetal and childhood growth, IGFs play an important role in metabolic regulation. This article describes the basic underlying human physiology of IGFs, how this differs from that of experimental models, and why some information can only be learned from human clinical studies.

Associations of insulin and insulin-like growth factors with physical performance in old age in the Boyd Orr and Caerphilly studies

Objective

Insulin and the insulin-like growth factor (IGF) system regulate growth and are involved in determining muscle mass, strength and body composition. We hypothesised that IGF-I and IGF-II are associated with improved, and insulin with worse, physical performance in old age.

Methods

Physical performance was measured using the get-up and go timed walk and flamingo balance test at 63–86 years. We examined prospective associations of insulin, IGF-I, IGF-II and IGFBP-3 with physical performance in the UK-based Caerphilly Prospective Study (CaPS; n = 739 men); and cross-sectional insulin, IGF-I, IGF-II, IGFBP-2 and IGFBP-3 in the Boyd Orr cohort (n = 182 men, 223 women).

Results

In confounder-adjusted models, there was some evidence in CaPS that a standard deviation (SD) increase in IGF-I was associated with 1.5% faster get-up and go test times (95% CI: −0.2%, 3.2%; p = 0.08), but little association with poor balance, 19 years later. Coefficients in Boyd Orr were in the same direction as CaPS, but consistent with chance. Higher levels of insulin were weakly associated with worse physical performance (CaPS and Boyd Orr combined: get-up and go time = 1.3% slower per SD log-transformed insulin; 95% CI: 0.0%, 2.7%; p = 0.07; OR poor balance 1.13; 95% CI; 0.98, 1.29; p = 0.08), although associations were attenuated after controlling for body mass index (BMI) and co-morbidities. In Boyd Orr, a one SD increase in IGFBP-2 was associated with 2.6% slower get-up and go times (95% CI: 0.4%, 4.8% slower; p = 0.02), but this was only seen when controlling for BMI and co-morbidities. There was no consistent evidence of associations of IGF-II, or IGFBP-3 with physical performance.

Conclusions

There was some evidence that high IGF-I and low insulin levels in middle-age were associated with improved physical performance in old age, but estimates were imprecise. Larger cohorts are required to confirm or refute the findings.

Association between insulin-like growth factor binding protein-2 levels and cardiovascular risk factors in Korean children

Emerging evidence has indicated that insulin-like growth factor binding protein-2 (IGFBP-2) may be involved in the development of obesity and insulin resistance like IGFBP-1. The aim of this study was to measure serum IGFBP-2 levels in overweight and obese children and to compare these levels with those of controls. We also analyzed the associations between IGFBP-2 and insulin sensitivity indices and cardiovascular risk factors. 134 Korean children including 55 overweight and 59 obese subjects were enrolled. We measured anthropometric values and determined fasting serum levels of IGFBP-2, glucose, insulin, lipid profiles, and insulin sensitivity indices including the homeostatic model assessment of insulin resistance (HOMA-IR) and the Quantitative Insulin Sensitivity Check Index (QUICKI). The subjects were subgrouped based on body mass index (BMI) and pubertal stage, and association analyses between IGFBP-2 levels and measured factors were performed in each group. Serum IGFBP-2 levels in overweight or obese children were significantly lower than those of controls regardless of pubertal development. Serum IGFBP-2 levels were negatively correlated with weight, BMI, waist circumference, fasting insulin levels, and HOMA-IR but were positively correlated with QUICKI. The associations were stronger in pubertal children than those in prepubertal children. However, no association was observed between serum IGFBP-2 levels and auxological or metabolic parameters in children with normal BMIs. These results suggested that IGFBP-2 might be a promising marker for early recognition of insulin resistance, particularly in overweight or obese children, regardless of pubertal stage.

Childhood obesity and risk of the adult metabolic syndrome: a systematic review

BACKGROUND

While many studies have demonstrated positive associations between childhood obesity and adult metabolic risk, important questions remain as to the nature of the relationship. In particular, it is unclear whether the associations reflect the tracking of body mass index (BMI) from childhood to adulthood or an independent level of risk. This systematic review aimed to investigate the relationship between childhood obesity and a range of metabolic risk factors during adult life.

OBJECTIVE

To perform an unbiased systematic review to investigate the association between childhood BMI and risk of developing components of metabolic disease in adulthood, and whether the associations observed are independent of adult BMI.

DESIGN

Electronic databases were searched from inception until July 2010 for studies investigating the association between childhood BMI and adult metabolic risk. Two investigators independently reviewed studies for eligibility according to the inclusion/exclusion criteria, extracted the data and assessed study quality using the Newcastle-Ottawa Scale.

RESULTS

The search process identified 11 articles that fulfilled the inclusion and exclusion criteria. Although several identified weak positive associations between childhood BMI and adult total cholesterol, low-density lipo protein-cholesterol, triglyceride and insulin concentrations, these associations were ameliorated or inversed when adjusted for adult BMI or body fatness. Of the four papers that considered metabolic syndrome as an end point, none showed evidence of an independent association with childhood obesity.

CONCLUSIONS

Little evidence was found to support the view that childhood obesity is an independent risk factor for adult blood lipid status, insulin levels, metabolic syndrome or type 2 diabetes. The majority of studies failed to adjust for adult BMI and therefore the associations observed may reflect the tracking of BMI across the lifespan. Interestingly, where adult BMI was adjusted for, the data showed a weak negative association between childhood BMI and metabolic variables, with those at the lower end of the BMI range in childhood, but obese during adulthood at particular risk.

Influence of catch-up growth on IGFBP-2 levels and association between IGFBP-2 and cardiovascular risk factors in Korean children born SGA

Small for gestational age (SGA) at birth and postnatal growth pattern may have an impact on insulin resistance and body composition in their later life. Emerging evidence has indicated that insulin-like growth factor binding protein-2 (IGFBP-2) may be related to insulin sensitivity. The aim of this study was to evaluate insulin resistance and IGFBP-2 levels in SGA children, and to identify the effect of catch-up growth on IGFBP-2 concentration. Serum IGFBP-2 levels were measured in 103 Korean SGA children including 49 prepubertal and 54 pubertal subjects. Anthropometric values, fasting serum levels of metabolic parameters and insulin sensitivity indices were determined. Each prepubertal or pubertal group was subgrouped based on height or weight catch-up growth. The subgroups with weight catch-up showed higher values of BMI, body fat mass, percent body fat, and total cholesterol. Particularly in pubertal children, IGFBP-2 concentration was lower in the subgroup with weight catch-up. Catch-up growth in height did not affect insulin resistance and metabolic parameters. IGFBP-2 levels were inversely correlated with BMI, body fat mass, percent body fat, insulin and leptin levels in both prepubertal and pubertal groups. Additionally in the pubertal group, systolic blood pressure, cholesterol levels were related to IGFBP-2. A strong relationship between IGFBP-2, the insulin sensitivity index, and some cardiovascular risk factors was observed in children born SGA, suggesting that IGFBP-2 might be a promising marker for early recognition of insulin resistance, particularly in children with weight catch-up.

Body size in early life and adult levels of insulin-like growth factor 1 and insulin-like growth factor binding protein 3

Body size in early life has been associated with breast cancer risk. This may be partly mediated through the insulin-like growth factor (IGF) pathway. The authors assessed whether birth weight, body fatness at ages 5 and 10 years, and body mass index (BMI; weight (kg)/height (m)(2)) at age 18 years were associated with plasma concentrations of insulin-like growth factor 1 (IGF-1) and insulin-like growth factor binding protein 3 in 6,520 women aged 32-70 years at blood draw from the Nurses' Health Study (1990-2006) and Nurses' Health Study II (1997-2005). Birth weight, body fatness in childhood, and BMI at age 18 years were inversely associated with adult IGF-1 levels. For example, IGF-1 levels were 11.9% lower in women who reported being heaviest at age 10 years than in those who were leanest at age 10 (P-trend < 0.0001). Further, women who reported their birth weight as ≥10 pounds (≥4.5 kg) (vs. <5.5 pounds (<2.5 kg)) had 7.9% lower IGF-1 levels (P-trend = 0.002). Women whose BMI at age 18 years was ≥30 (vs. <20) had 14.1% lower IGF-1 levels (P-trend < 0.0001). Similar inverse associations were observed for insulin-like growth factor binding protein 3. These observations did not vary by adult BMI or menopausal status at blood draw. These findings suggest that altered IGF-1 levels in adulthood may be a mechanism through which early-life body size influences subsequent breast cancer risk.

Hormonal mechanisms underlying the relationship between obesity and breast cancer

Given the worldwide epidemic of obesity, it is inevitably an increasingly common comorbidity for women who develop breast cancer; therefore, it is critical to understand its impact on this disease. This review focuses on the influence of obesity on breast cancer development and progression and describes the hormonal factors that may underlie the observations, with particular emphasis on the roles of estrogen, insulin/insulin-like growth factor axis, and adipokines.

Prenatal exposure to the major DDT metabolite 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (DDE) and growth in boys from Mexico

Recent data suggest that prenatal exposure to p,p'-DDE may reduce height and increase body mass index (BMI) in childhood, thus potentially raising the risk of adult health problems. The association between prenatal DDE exposure and growth was evaluated in 788 boys from Chiapas, an area of Mexico where DDT was recently used. The median DDE levels in maternal serum at birth (2002-2003) were 2.7 microg/g lipid. 2633 measurements of height (cm) and weight (kg) were obtained in 2004-2005. The median age of the children during follow-up was 18 months (quartiles 14 and 22 months). Height and body mass index (kg/m(2)) were age-standardized and expressed as standard deviation scores (SDS). Multivariate random-effect models for longitudinal data were fitted and predicted height and BMI SDS were estimated from the adjusted models. Overall, associations between prenatal DDE level and height or BMI SDS at any given age were not observed. For example, the predicted values showed that children with the highest exposure (DDE: >9.00 microg/g) compared to those least exposed (DDE: <3.01 microg/g) grew similarly and they had a BMI SDS similar to the referent group. The results do not support the prior findings of an association of DDE exposure with childhood height or BMI.

Insulin-like growth factor binding protein: a possible marker for the metabolic syndrome?

Insulin-like growth factor (IGF) binding proteins (IGFBPs) moved on to contain both IGF high- and low-affinity binders, exerting mitogenic and metabolic actions through its complex interplay between IGF/insulin and its IGF/insulin-independent manner. Progress on the metabolic-related function of IGFBPs has been rapid in recent years. A wealth of studies in 3T3-L1 adipocytes and the transgenic mice models demonstrated that IGFBPs played important roles in the pathogenesis of obesity and insulin resistance. Studies conducted in humans demonstrated the close relation between IGFBPs and the components of the metabolic syndrome. Abnormal expression of IGFBP was detected in various states of the metabolic disorders, suggesting that it could be used as a convenient and sensitive marker of insulin resistance, identification of insulin-resistant individuals at high cardiovascular risk, and may be an earlier marker of the metabolic syndrome. These exciting findings bring us new insight into the elucidation of the metabolic syndrome, which may have important clinical implications.

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

BACKGROUND

IGF binding protein (IGFBP)-2 might protect against cardiovascular disease. Small for gestational age (SGA) birth could be associated with a higher risk for type 2 diabetes mellitus and cardiovascular disease in later life. No data are available on the relationship between serum IGFBP-2 levels and cardiovascular risk factors in young adults and children born SGA.

OBJECTIVE

The aim of the study was to determine circulating IGFBP-2 levels in subjects born SGA and to investigate the association with cardiovascular risk factors.

METHODS

IGFBP-2 levels were measured in sera from 151 young adults born SGA and 147 short SGA children. Age- and gender-adjusted sd scores (SDS) were calculated. We determined blood pressure, serum lipids, body composition by dual-energy x-ray absorptiometry, and glucose homeostasis by homeostasis model of assessment for insulin resistance or frequently sampled iv glucose tolerance test.

RESULTS

Serum IGFBP-2 SDS was significantly reduced in SGA young adults (with normal or short stature). Fat mass SDS was relatively high in SGA young adults and was reduced in short SGA children. Serum IGFBP-2 SDS in SGA young adults correlated positively with insulin sensitivity and negatively with fat mass SDS, insulin secretion (acute insulin response), fasting insulin, homeostasis model of assessment for insulin resistance, total cholesterol, triglycerides, and blood pressure SDS. The association between serum IGFBP-2 SDS and insulin sensitivity, blood pressure, total cholesterol, and triglyceride levels persisted after adjustment for known covariates including fat mass SDS. In short SGA children, IGFBP-2 SDS did not correlate with any of the cardiovascular risk factors.

CONCLUSION

In young adults who were born SGA, serum IGFBP-2 levels associate with cardiovascular risk markers.

IGF-dependent and IGF-independent actions of IGF-binding protein-1 and -2: implications for metabolic homeostasis

Insulin-like growth factor (IGF)-binding proteins (IGFBPs) confer temporospatial regulation to IGF bioactivity. Both stimulatory and inhibitory effects of IGFBPs on IGF actions have been described, and IGF-independent effects of several IGFBPs are emerging. Accumulating evidence indicates important roles for members of the IGFBP family in metabolic homeostasis. For example, IGFBP-1 concentrations fluctuate inversely in response to changes in plasma insulin levels, implicating IGFBP-1 in glucoregulation, and fasting levels of IGFBP-1 predict insulin sensitivity at the population level. IGFBP-2 concentrations reflect long-term insulin sensitivity and are reduced in the presence of obesity. Here, we review the evolving roles of IGFBP-1 and IGFBP-2 in metabolic homeostasis, summarize their effects on IGF bioactivity and explore putative mechanisms by which they might exert IGF-independent cellular actions.

Associations of insulin-like growth factor (IGF)-I, IGF-II, IGF binding protein (IGFBP)-2 and IGFBP-3 with ultrasound measures of atherosclerosis and plaque stability in an older adult population

CONTEXT

Circulating IGF-I is inversely associated with ischemic heart disease incidence. Whether this association relates to alterations in plaque growth or stability, and the role of IGF-II and the major binding proteins [IGF binding protein (IGFBP)-2 and -3], is unclear.

OBJECTIVE

Our objective was to test the hypothesis that circulating IGF-I is inversely, and IGF-II is positively, associated with subclinical atherosclerosis and plaque stability.

DESIGN, SETTING, AND PARTICIPANTS

This was a cross-sectional analysis based on 310 participants in the United Kingdom-based Boyd Orr cohort who were aged 63-82 yr. Cohort members from Aberdeen, Bristol, Dundee, Wisbech, and London were invited to clinics for fasted venepuncture and arterial ultrasound examination.

MAIN OUTCOMES

Arterial intima-media thickness, arterial plaque prevalence, and computerized assessment of plaque echogenicity (a measure of stability), undertaken using the gray scale median, were calculated.

RESULTS

In total, 269 of 310 (86.8%) participants had at least one carotid or femoral plaque. In models controlling for IGFBP-3, there was a 44% (95% confidence interval 12-64%) reduction in the odds of any plaque and a 28% lower (0-48%) odds of echolucent (unstable) plaques per sd increase in IGF-I. IGFBP-3 was positively associated with plaque instability (odds ratio: 1.38; 0.99-1.93). IGF-II was positively associated (0.05-mm increase per sd; 95% confidence interval 0.01-0.09), and IGFBP-2 was inversely associated, with carotid bifurcation intima-media thickness. Neither IGF-II nor IGFBP-2 was associated with plaque prevalence or echogenicity.

CONCLUSION

High-circulating IGF-I levels may promote arterial plaque stability. IGF-II and IGFBP-2 do not appear to play a role in plaque development or stability.

Molecular genetics of human growth hormone, insulin-like growth factors and their pathways in common disease

The human growth hormone gene (GH1) and the insulin-like growth factor 1 and 2 genes (IGF1 and IGF2) encode the central elements of a key pathway influencing growth in humans. This "growth pathway" also includes transcription factors, agonists, antagonists, receptors, binding proteins, and endocrine factors that constitute an intrincate network of feedback loops. GH1 is evolutionarily coupled with other genes in linkage disequilibrium in 17q24.2, and the same applies to IGF2 in 11p15.5. In contrast, IGF1 in 12q22-24.1 is not in strong linkage disequilibrium with neighbouring genes. Knowledge of the functional architecture of these regions is important for the understanding of the combined evolution and function of GH1, IGF2 and IGF1 in relation to complex diseases. A number of mutations accounting for rare Mendelian disorders have been described in GH-IGF elements. The constellation of genes in this key pathway contains potential candidates in a number of complex diseases, including growth disorders, metabolic syndrome, diabetes (notably IGF2BP2) cardiovascular disease, and central nervous system diseases, and in longevity, aging and cancer. We review these genes and their associations with disease phenotypes, with special attention to metabolic risk traits.