Jaap van Doorn

Hypoglycaemia associated with the production of insulin-like growth factor II and insulin-like growth factor binding protein 6 by a haemangiopericytoma.

Non‐islet‐cell tumour‐induced hypoglycaemia (NICTH) is, in most cases, attributable to tumour production of insulin‐like growth factor II (IGF‐II). Tumour‐derived IGF‐II has a higher than normal molecular weight (big ‘IGF‐II’) and an impaired ability to form the normal ternary 150 kD complex with IGF binding protein‐3 (IGFBP‐3) and the acid‐labile subunit (ALS). Consequently, tumoral IGF‐II circulates mainly in smaller binary complexes which have a higher bioavailability than the ternary complex.

Various components of the insulin‐like growth factor system in tumor tissue, cerebrospinal fluid and peripheral blood of pediatric medulloblastoma and ependymoma patients

The insulin‐like growth factor (IGF) system plays an important role in neuronal development and may contribute to the development of brain tumors. In this study, we studied mRNA expression levels of IGFs, insulin‐like growth factor binding proteins (IGFBPs) and insulin‐like growth factor receptors (IGFRs) in 27 pediatric medulloblastomas, 13 pediatric ependymomas and 5 control cerebella. Compared to normal cerebellum, mRNA levels of IGFBP‐2 and IGFBP‐3 were significantly increased in medulloblastomas and ependymomas. IGFBP‐2 expression was indicative of poor prognosis in medulloblastomas, whereas IGFBP‐3 mRNA levels were especially high in anaplastic ependymomas. IGFBP‐5 and IGF‐II mRNA levels were significantly increased in ependymomas compared to control cerebellum. Protein expression levels of IGFs and IGFBPs were analyzed in the cerebrospinal fluid (CSF) of 16 medulloblastoma, 4 ependymoma and 23 control patients by radioimmuno assay to determine whether they could be used as markers for residual disease after surgery. No aberrant CSF protein expression levels were found for ependymoma patients. In medulloblastoma patients, the IGFBP‐3 protein levels were significantly higher than in ependymoma patients and controls. Moreover, enhanced levels of proteolytic fragments of IGFBP‐3 were found in the CSF of medulloblastoma patients, being in concordance with a significantly increased IGFBP‐3 proteolytic activity in the CSF of these patients. In conclusion, our data suggest that the IGF system is of importance in pediatric medulloblastomas and ependymomas. Larger studies should be conducted to validate the predictive values of the levels of intact IGFBP‐3 and proteolytic fragments in CSF in the follow‐up of medulloblastomas.

Effects of Lycopene on the Insulin-Like Growth Factor (IGF) System in Premenopausal Breast Cancer Survivors and Women at High Familial Breast Cancer Risk

Insulin-like growth factor-I (IGF-I) is an important growth factor associated with increased risk of premenopausal breast cancer. We conducted a randomized, placebo-controlled, double-blind, crossover trial to evaluate whether tomato-derived lycopene supplementation (30 mg/day for 2 mo) decreases serum levels of total IGF-I in premenopausal women with 1) a history of breast cancer ( n = 24) or 2) a high familial breast cancer risk ( n = 36). Also, IGF binding protein (IGFBP) increasing effects were evaluated. Lycopene supplementation did not significantly alter serum total IGF-I and other IGF system components in the 2 study populations combined. However, statistically significant discordant results were observed between the 2 study populations (i.e., P < 0.05 for total IGF-I, free IGF-I, and IGFBP-3). Total IGF-I and IGFBP-3 were increased in the breast cancer survivor population [total IGF-I = 7.0%, 95% confidence interval (CI) = –0.2 to 14.3%; IGFBP-3 = 3.3%, 95% CI = 0.7–6.0%), and free IGF-I was decreased in the family history population (–7.6%, 95% CI = –14.6 to –0.6%). This randomized controlled trial shows that 2 mo of lycopene supplementation has no effect on serum total IGF-I in the overall study population. However, lycopene effects were discordant between the 2 study populations showing beneficial effects in high-risk healthy women but not in breast cancer survivors.

Expression of insulin-like growth factor system components in colorectal tissue and its relation with serum IGF levels.

CONTEXT The insulin-like growth factor (IGF)-system has been implicated in colorectal tumor carcinogenesis. Although both tumor expression levels and serum concentrations of IGF-system components are related to colorectal cancer risk, it is unknown whether IGF levels in tissue and serum are correlated. OBJECTIVE The objective of this study was to determine expression levels of various IGF-system components in different locations of the colorectum, and to investigate whether normal tissue IGF expression levels are correlated with serum IGF-I and IGF-II concentrations. DESIGN Biopsies from macroscopically normal mucosa at four locations in the colorectum (ascending, transverse, sigmoid colon, and rectum) and a fasting serum sample were obtained from 48 asymptomatic patients at increased risk of colorectal cancer. Expression levels of IGF-I, IGF-II, IGF-IR, IGF-IIR, and IGFBP-3 messenger RNA (mRNA) in tissue were quantitatively evaluated using real-time RT-PCR. Expression of IGF-IR protein in the ascending colon and rectum tissue specimens was assessed semi-quantitatively by immunohistochemistry. Serum IGF-I and IGF-II concentrations were determined using immunometric assays. RESULTS With the exception of IGF-IIR, mRNA levels of all the IGF-system components investigated, as well as IGF-IR protein expression, were significantly higher in the rectum compared with the ascending colon (p<or=0.001). Serum IGF-I and IGF-II concentrations did not correlate with any of the parameters studied in colorectal tissues. CONCLUSIONS Our results indicate that in humans IGF-system components are differentially expressed in the colorectum. Moreover, our findings suggest that local and circulating components of the IGF-system are differentially regulated. However, due to large intra-individual variation in mRNA expression, we cannot formally exclude undetected but existing routes of co-regulation.

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.

Insulin-Like Growth Factor-Binding Protein-1: Serum Levels, Promoter Polymorphism, and Associations with Components of the Metabolic Syndrome in Short Subjects Born Small for Gestational Age

CONTEXT IGF binding protein (IGFBP)-1 is the only acute regulator of IGF-I bioavailability. Its production is suppressed by insulin, and low levels are associated with hyperinsulinemia and cardiovascular disease risk in adults. Data on IGFBP-1 levels in short, small for gestational age (SGA) subjects are scarce, and associations with IGFBP1 promoter single nucleotide polymorphisms have not been established. OBJECTIVE The aim of the study was to determine IGFBP-1 levels in short SGA subjects compared with those in controls, to assess genotype frequency of the -575 G/A single nucleotide polymorphism, and to determine its impact on IGFBP-1 levels. SUBJECTS A total of 272 short subjects born SGA and 330 subjects with normal stature (245 children, 85 young adults) participated in the study. OUTCOME MEASURES We measured fasting levels of IGFBP-1, IGF-I, insulin and lipid parameters, and body composition. RESULTS IGFBP-1 sd score (SDS) was comparable to controls in lean, short, SGA children but significantly lower in short SGA adults with normal fat mass (P < 0.001). IGFBP-1 SDS correlated significantly with insulin levels, systolic blood pressure SDS, and various lipid parameters. Baseline IGFBP-1 SDS was lowest in SGA children with -575 GG genotype and significantly higher in SGA children with one or two copies of the A allele. In response to a given insulin level, children with the AA genotype had a significantly higher IGFBP-1 SDS compared to children with the GG genotype. CONCLUSION Normal IGFBP-1 levels in lean, short, SGA children may reflect a normal metabolic state, despite reported hyperinsulinemia. IGFBP-1 is modulated by polymorphic variability and seems to be an additional player in the complex interaction between the IGF-IGFBP axis, glucose homeostasis, and lipid metabolism.

Hypoglycemia in a Patient With a Big “Big”-IGF-II-Producing Tumor

Non-islet cell tumor-induced hypoglycemia is a rare cause of hypoglycemia (1). Mesenchymal and epithelial tumors account for most cases (2, 3). A 60-year-old man with a palpable abdominal mass (computed tomography scan, 12 16 16-cm lesion, retroperitoneal) presented with neuroglycopenia responding to iv glucose. A fasting test confirmed symptomatic hypoglycemia (plasma glucose, 2.3 mmol/L within 4 h). Plasma levels of insulin (0.2 mU/L) and C-peptide ( 10 pmol/L) were suppressed, excluding endogenous hyperinsulinemia. Plasma IGF-I was also suppressed ( 2.6 nmol/L). Plasma total IGF-II was normal (460 ng/mL; 0.57 SD score) but pro-IGF-IIE (68–88) (“big”-IGF-II) was markedly raised (98 ng/ml; 8.97 SD score) (4). In agreement with the hypothesis that aberrant processing of IGF-II disrupts the ternary complex of IGF-II, IGF-binding protein 3, and acid labile subunit, we show here that pro-IGF-IIE (68– 88) was mainly present within binary complexes and as plasma free “big”-IGF-II (Figure 1). This would increase its accessibility to insulin and IGF-I receptors, ultimately leading to hypoglycemia and suppression of the pituitary GH-IGF-I axis (2, 3). Our patient fully recovered after surgery (histology, Figure 2), and successfully passed a 72-hour fasting test (glucose, 4.6 mmol/L). All laboratory parameters, including pro-IGF-IIE (68–88), had normalized. The distribution of “big”-IGF-II in the postoperative plasma became comparable to control plasma (Figure 1). The patient is still asymptomatic 1 year after surgery, with 10-year recurrence-free survival expected to be 50% (5). “Big”-IGF-II-producing tumors should be considered in tumor patients presenting with hypoglycemia. This case demonstrates that the ensuing changes in “big”-IGF-II distribution toward free pro-IGF-IIE (68–88) coincide with IGF-I suppression and are fully reversible.

Expression of osteotropic growth factors and growth hormone receptor in a canine distraction osteogenesis model.

Osteotropic growth factors play an important role in bone metabolism. Nevertheless, knowledge about their expression in relation to distraction osteogenesis remains limited. The aim of the present study was to determine the expression of growth hormone (GH), growth hormone receptor (GHR), insulin-like growth factor I (IGF-I), insulin-like growth factor II (IGF-II), and bone morphogenetic protein 2 (BMP-2) in distraction-induced bone regeneration. Expression of these factors was assessed during the consolidation phase, comparing distraction osteogenesis with osteotomy-induced bone formation. Real-time PCR was performed as a semiquantitative measurement of mRNA, and the relative expression levels of these factors were determined. In addition, plasma GH profiles and plasma concentrations of IGF-I, IGF-II, and insulin-like growth factor-binding protein 4 and -6 (IGFBP-4 and -6) were measured to assess their potential systemic role during bone formation. Expression of GHR, IGF-I, and BMP-2 had significantly increased in comparison with the expression of these factors in mature bone. Expression of GHR was significantly higher in distraction-induced bone regenerate than in osteotomy-induced bone. No significant differences were found for the expression of IGF-I and BMP-2 between distraction and osteotomy. Plasma concentrations of GH, IGF-I, IGF-II, IGFBP-4, and IGFBP-6 did not demonstrate any significant differences between treatment groups and controls. Upregulation of GHR expression in distraction osteogenesis may enhance sensitivity to endogenous systemic GH and thus promote consolidation of the regenerated bone. Changes in the systemic osteotropic growth factors GH, IGF-I, IGF-II, IGFBP-4, and IGFBP-6 do not seem to be of importance during distraction osteogenesis.

Dehydroepiandrosterone sulfate treatment for atrichia pubis.

Objective: To evaluate the efficacy of oral dehydroepiandrosterone sulfate (DHEAS) treatment for atrichia pubis in female adolescents. Study Design: Two XY female adolescents with 17-hydroxylase deficiency and 2 XX females with panhypopituitarism presenting with atrichia pubis were treated with a daily dosage of DHEAS 10 mg/m2 body surface in addition to their regular substitution therapy. The dosage was increased according to clinical response. Pubic hair stages, growth and serum DHEAS were evaluated and in 1 case also serum IGFs and IGFBPs. Results: A dosage of 10 mg/m2 for 1 year led to serum DHEAS levels at the lower limit of the normal range. 15 mg/m2 was needed to achieve pubic hair stage 4–5 and axillary hair in patients with 17-hydroxylase deficiency. In panhypopituitarism, pubic hair developed at a slower pace and reached stage 4 on a dosage of 25– 30 mg/m2. Baseline serum IGF-I SDS was –0.67 and did not change on the initial dosage of DHEAS, in combination with submaximal estrogen substitution (10 µg ethinyl estradiol). On the combination of 15 mg/m2 DHEAS and full estrogen substitution, IGF-I SDS increased to an average of –0.15. IGFBP-3 SDS increased from 1.4 to a mean of 2.6 in the first year, and went back to 1.4 in the second year. IGFBP-6 SDS was low at baseline (–2.5) and rose to –1.9 and –1.7 IGF-II and IGFBP-1 showed an irregular pattern. Conclusions: Oral administration of DHEAS in a dosage of 15 mg/m2 o.d. is an efficacious treatment for atrichia pubis. For females with a panhypopituitarism a higher dosage appears needed. Given this and other biological actions of DHEAS, substitution therapy with DHEAS or DHEA to females with adrenal androgen deficiency appears rational.

Marginal growth increase, altered bone quality and polycystic ovaries in female prepubertal rats after treatment with the aromatase inhibitor exemestane.

Background: Aromatase inhibition has been proposed as a potential approach for growth enhancement in children with short stature, but detailed animal studies are lacking. Aim: To assess the effect and potential adverse effects of aromatase inhibition on growth in female rats. Methods: Prepubertal Wistar rats received intramuscular injections with placebo or the aromatase inhibitor exemestane at a dose of 10, 30 or 100 mg/kg/week (E10, E30, E100) for 3 weeks. A control group was ovariectomized (OVX). Weight and length gain, tibia and femur length, growth plate width, organ weights, insulin-like growth factor I (IGF-I) levels, and histology of the ovaries, uterus and brain were analyzed. X-ray microtomography of femora was performed. Results: E100 significantly increased weight gain and growth plate width, but less prominently than OVX. Trabecular number and thickness were decreased in E100 and OVX in the metaphysis and epiphysis. E100 significantly decreased ovarian weight and multiple cysts were seen upon histological evaluation. No significant effects were found on IGF-I levels and brain morphology in E100. E10 and E30 had no effects on growth. Conclusion: A high dose of exemestane marginally increases axial and appendicular growth in female rats, at the expense of osteopenia and polycystic ovaries.