Insulin-like Growth factor-I Binding Protein-3 Research Articles

Prognostic impact of insulin-like growth factor-I and its binding proteins, insulin-like growth factor-I binding protein-2 and -3, on adverse histopathological features and survival outcomes after radical cystectomy.

ObjectivesInsulin‐like growth factor‐I and its binding proteins are involved in cancer development, progression, and metastasis. In urothelial carcinoma, the impact of this pathway is still poorly investigated. The present large cohort study aimed to evaluate the association of preoperative circulating levels of insulin‐like growth factor‐I, insulin‐like growth factor‐I binding protein‐2 and ‐3 on outcomes after radical cystectomy.MethodsA retrospective cohort study of the plasma specimens from 1036 consecutive urothelial carcinoma patients who were treated with radical cystectomy. The primary and secondary outcomes were adverse histopathological features and survival outcomes. Binominal logistic regression and multivariable Cox regression analyses were performed to assess the association of plasma levels of insulin‐like growth factor‐I, insulin‐like growth factor‐I binding protein‐2 and ‐3 with outcomes.ResultsOn multivariable analysis adjusting for the effects of preoperative variables, lower insulin‐like growth factor‐I binding protein‐2 levels were associated with an increased risk of lymph node metastasis and (any non‐organ confined disease) any non‐organ confined disease. Insulin‐like growth factor‐I binding protein‐3 levels were also inversely independently associated with lymph node metastasis. Receiver operating characteristic curve analysis showed that the addition of insulin‐like growth factor‐I binding proteins biomarkers to a reference model significantly improved the discriminating ability for the prediction of lymph node metastasis (+10.0%, P < 0.001). On multivariable Cox regression models, lower levels of both insulin‐like growth factor‐I binding protein‐2 and ‐3 plasma levels were associated with recurrence‐free survival, cancer‐specific survival, and overall survival. insulin‐like growth factor‐I binding protein‐2 and ‐3 levels and improved the discrimination of a standard reference model for the prediction of recurrence‐free survival, cancer‐specific survival, and overall survival (+4.9%, 4.9%, 2.3%, respectively).ConclusionsPreoperative insulin‐like growth factor‐I binding protein‐2 and ‐3 are significantly associated with features of biologically and clinically aggressive urothelial carcinoma. These biomarkers improved prognostic urothelial carcinoma models.

Patients with low IGF-I after curative surgery for Cushing's syndrome have an adverse long-term outcome of hypercortisolism-induced myopathy.

Glucocorticoid excess leads to muscle atrophy and weakness in patients with endogenous Cushing's syndrome. Insulin-like growth factor I (IGF-I) is known to have protective effects on muscle loss. We hypothesized that individual serum IGF-I concentrations might be predictive for long-term myopathy outcome in Cushing's syndrome. In a prospective longitudinal study of 31 patients with florid Cushing's syndrome, we analyzed IGF-I and IGF binding protein 3 (IGFBP 3) concentrations at the time of diagnosis and following surgical remission over a period of up to 3 years. We assessed muscle strength by grip strength measurements using a hand grip dynamometer and muscle mass by bio-impedance measurements. Individual serum IGF-I concentrations in the postoperative phase were strongly predictive of long-term grip strength outcome (rs = 0.696, P ≤ 0.001). Also, lower IGF-I concentrations were associated with a lower muscle mass after 3 years (rs = 0.404, P = 0.033). While patients with high IGF-I s.d. scores (SDS; >1.4) showed an improvement in grip strength within the follow-up period (P = 0.009), patients with lower IGF-I SDS (≤-0.4) had a worse outcome with persisting muscle dysfunction. In contrast, preoperative IGF-I concentrations during the florid phase of Cushing's syndrome did not predict long-term muscle function outcome (rs = 0.285, P = 0.127). Lower individual IGF-I concentrations 6 months after curative surgery for Cushing's syndrome are associated with adverse long-term myopathy outcome and IGF-I might be essential for muscle regeneration in the early phase after correction of hypercortisolism.

The IGF-Axis and Diabetic Retinopathy Before and After Gastric Bypass Surgery.

Laparoscopic gastric bypass (LGB) abruptly causes remission of type 2 diabetes (T2D). Such dramatic metabolic changes have previously been found to cause worsening of diabetic retinopathy (DR) and circulating insulin-like growth factor I (IGF-I) has been suggested as a causal mediator. We aimed to evaluate baseline imbalances in the circulating IGF-system and changes after LGB in patients with T2D. Prospective ocular examinations and measurement of the IGF-axis before and 3 and 12months after LGB. IGF-bioactivity was measured by cell-based IGF-I receptor (IGF-IR) kinase activation assay (bioactive IGF). Total IGF-I, IGF-II and IGF binding protein (IGFBP) 1 and 3 were determined by immunoassays. At baseline, 18 of 36 patients presented with DR. These patients had higher levels of bioactive IGF (p=0.03) than patients without DR and this association was strengthened in multivariate analysis (p=0.006). Three patients had worsening of DR, unrelated to other markers. In univariate analysis, bioactive IGF increased at 3months (p=0.05) but this change became insignificant in multivariate analysis (p=0.11). IGFBP-1 increased whereas IGFBP-3 and total IGF-II decreased at the two postoperative visits (p≤0.001). Total IGF-I showed no significant changes. HbA1c, glucose, HOMA-IR and lipids improved after surgery. Two patients did not complete the 12-month visit. In obese T2D patients, bioactive IGF is a potential biomarker for DR and levels tended to increase 3months after bariatric surgery. IGFBP-1 increased while IGFBP-3 and total IGF-II decreased postoperatively, but these changes were unassociated with the development of DR. Markers of the metabolic syndrome improved.

Effect of insulin-like growth factor-I during the early postnatal period in intrauterine growth-restricted rats.

Insulin-like growth factor-I (IGF-I) is essential for perinatal growth and development; low serum IGF-I has been observed during intrauterine growth restriction (IUGR). We investigated the effects of recombinant human (rh) IGF-I in IUGR rats during the early postnatal period. Intrauterine growth restriction was induced by bilateral uterine artery ligation in pregnant rats. IUGR pups were divided into two groups injected daily with rhIGF-I (2 mg/kg; IUGR/IGF-I, n = 16) or saline (IUGR/physiologic saline solution (PSS), n = 16) from postnatal day (PND) 7 to 13. Maternal sham-operated pups injected with saline were used as controls (control, n = 16). Serum IGF-I and IGF binding proteins (IGFBP) 3 and 5 were measured on PND25. The expression of Igf-i, IGF-I receptor (Igf-ir), Igfbp3, and 5 mRNA in the liver and brain was measured using real-time polymerase chain reaction on PND25. Immunohistochemical staining of the liver for IGF expression was performed. Mean bodyweight on PND3 and PND25 in the IUGR pups (IUGR/IGF-I and IUGR/PSS) was significantly lower than that of the control pups. Serum IGF-I and hepatic Igf-ir mRNA in the IUGR pups were significantly lower than those in the control pups. In the IUGR/IGF-I group, hepatic Igfbp3 mRNA and liver immunohistochemical staining were increased. In the IUGR/PSS and control pups, there were no significant differences between these two groups in serum IGFBP3 and IGFBP5, hepatic Igf-i and Igfbp-5 mRNA, or brain Igf mRNA. No benefits on body and brain weight gain but an effective increase in hepatic IGFBP-3 was observed after treatment with 2 mg/kg rhIGF-I during the early postnatal period.

Cross-sectional and longitudinal associations between insulin-like growth factor I and metabolic syndrome: a general population study in German adults

A previous study showed an inverse association between the insulin-like growth factor I (IGF-I) and the risk of impaired glucose tolerance or diabetes mellitus. Moreover, myocardial infarction patients with high baseline IGF-I levels had a lower risk of diabetes mellitus. These data suggested a protective effect of IGF-I against the development of metabolic syndrome. However, there are no longitudinal data regarding IGF-I and metabolic syndrome. The aim of the present study was to investigate the longitudinal association between IGF-I and metabolic syndrome. Data from the population-based Study of Health in Pomerania, Germany, were used for cross-sectional (n = 3903) and longitudinal (n = 2143) analyses (5-year follow-up). Metabolic syndrome was defined by three or more of the following five components: abdominal obesity, elevated triglycerides, reduced high-density lipoprotein cholesterol, elevated blood pressure and elevated nonfasting glucose. Serum IGF-I and IGF binding protein 3 (IGFBP-3) were determined by chemiluminescence immunoassays. Logistic and Poisson regression analyses were performed to determine associations. In cross-sectional analyses high IGFBP-3 as well as high and low IGF-I/IGFBP-3 ratio levels were associated with prevalent metabolic syndrome. In longitudinal analyses, the direction of the relation changed: men but not women with high IGF-I or IGF-I/IGFBP-3 ratio levels had an increased, whereas men with low levels had a decreased risk of incident metabolic syndrome. In concordance with previous studies, our cross-sectional analyses showed a relation between low IGF-I/IGFBP-3 ratio and the prevalence of metabolic syndrome. In contrast, the longitudinal analyses indicated that a high IGF-I level was a risk marker for incident metabolic syndrome.

Relation of insulin‐like growth factor‐IandIGFbinding protein 3 with markers of inflammation: results of a population‐based study

Previous studies in acromegaly and growth hormone deficiency observed inverse associations between insulin-like growth factor-I (IGF-I) levels and inflammatory biomarkers including high-sensitive C-reactive protein (hsCRP), interleukin-6 or fibrinogen. We aimed to assess the relations between IGF-I or IGF binding protein 3 (IGFBP-3) levels and hsCRP, interleukin-6, fibrinogen and white blood cell count (WBC) in a population-based sample. Data from 3480 subjects from the population-based Study of Health in Pomerania (SHIP) were used. IGF-I, IGFBP-3 and inflammatory biomarkers were measured. Analysis of variance (anova), quantile regression models and logistic regression models, adjusted for age, smoking, diabetes mellitus and waist circumference, were performed. anova and/or quantile regression showed inverse associations between IGF-I and hsCRP as well as positive associations between IGF-I and fibrinogen among both sexes. Furthermore, the odds of elevated fibrinogen levels increased with increasing IGF-I levels (per SD IGF-I increase: men: odds ratio (OR) 1·35 [95% confidence interval (CI) 1·04, 1·55]; women: OR 1·44 [95% CI 1·21, 1·71]) in both sexes, whereas the odds of increased hsCRP (women: OR 0·46 [95% CI 0·36, 0·58]) and interleukin-6 (men: odds ratio (OR) 0·77 [95% CI 0·61, 0·96]; women: OR 0·69 [95% CI 0·55, 0·86]) decreased. Serum IGF-I levels are associated with inflammatory biomarkers including hsCRP, interleukin-6 and fibrinogen. Further experimental studies are needed to elucidate the mechanisms underlying the relation between the GH/IGF axis and the inflammatory system.

Bone Metabolism in Cholestatic Children Before and After Living-Related Liver Transplantation—a Long-Term Prospective Study

Bone disorders are common in children with end-stage liver diseases, especially those associated with cholestasis. Abnormal hepatocyte function, disordered vitamin D metabolism and calcium-phosphorous homeostasis, malnutrition, and immunosuppressive treatment are potential risk factors of bone tissue pathology before and after transplantation.The aim of the study was to analyze the long-term effect of successful living-related liver transplantation (LRLTx) on skeletal status and bone metabolism in cholestatic children.Eighteen cholestatic children (1.4±0.5yr old; 12 females [F]/6 males [M]) qualified for LRLTx were analyzed; 16 (5F/11M) of them participated in long-term observation (V4). Serum levels of osteocalcin (OC), procollagen type 1 N-terminal propeptide (P1NP), cross-linked telopeptide of type 1 collagen (CTx), insulin-like growth factor I (IGF-I), IGF-I binding protein 3 (IGFBP-3), parathyroid hormone (PTH), 25-hydroxyvitamin D (25(OH)D), and 1,25-dihydroxyvitamin D (1,25(OH)2D) were assayed before (V0) and 6mo (V1), 12mo (V2), 18mo (V3), and 4.4yr (V4) after LRLTx. Total body bone mineral content (TBBMC) and total body bone mineral density (TBBMD) were measured by dual-energy X-ray absorptiometry (DXA) at the same pattern.Before LRLTx, the OC, P1NP, CTx, IGF-I, and IGFBP-3 levels as well as TBBMC and TBBMD were decreased compared with age-matched control group. The mean serum levels of 25(OH)D and 1,25(OH)2D were within reference ranges from V0 to V4. After LRLTx, the OC, P1NP, CTx, IGF-I, and IGFBP-3 as well as TBBMC and TBBMD reached the age-matched reference values. At V4, the level of P1NP decreased below and the PTH increased above the reference range that coincided with reduced Z-scores of both TBBMC (−1.11±1.24) and TBBMD (−1.00±1.19). P1NP and CTx, both measured at V3, correlated with IGF-I at V2 (R=0.86, p=0.014 and R=0.78, p=0.021, respectively) and PTH at V3 for P1NP and V1 for CTx (R=0.64, p=0.048 and R=0.54, p=0.038, respectively). The TBBMC changes between V0 and V4 correlated with IGF-I (R=0.68, p=0.015) and 1,25(OH)2D (R=0.54, p=0.025), both assayed at V1. The change of TBBMC Z-scores between V0 and V4 correlated with P1NP at V1 (R=0.69, p=0.002). The TBBMD changes between V0 and V4 correlated with CTx at V1 (R=0.54, p=0.027) and P1NP change between V0 and V1 (R=0.51, p=0.038).In short-term observation, successful LRLTx led to bone metabolism normalization triggered by probable anabolic action of IGF-I and PTH and manifested by TBBMC and TBBMD increases. In long-term horizon, moderately impaired DXA assessed bone status coincided with disturbances in bone metabolism. Bone metabolism markers, especially P1NP and CTx, appeared to be good predictors of changes in bone status evaluated by DXA.

Insulin-Like Growth Factor I Serum Levels Influence Ischemic Stroke Outcome

Insulin-like growth factor I (IGF-I) is neuroprotective in animal models of stroke. We investigated whether serum IGF-I levels in patients with acute ischemic stroke influence stroke severity and outcome. Concentrations of IGF-I and IGF binding protein 3 were measured in serum samples obtained within 6 hours after stroke onset from 255 patients who took part in the placebo arm of the United States and Canadian Lubeluzole in Acute Ischemic Stroke Study. Stroke severity was assessed with the National Institutes of Health Stroke Scale. Multivariate analysis was performed to assess the overall shift in modified Rankin Scale score and changes in the National Institutes of Health Stroke Scale score at 3 months. Survival curves were plotted using the Kaplan-Meier method, and the Cox proportional hazard model was used for multivariate analysis to investigate factors influencing survival. After controlling for statistically relevant risk factors, subjects with high IGF-I levels or IGF-I/IGF binding protein 3 ratios had a better neurological and functional outcome at 3 months. Baseline stroke severity was not different between high and low IGF-I groups. In contrast to the low IGF-I group, neurological symptoms gradually improved from Day 3 in the high IGF-I group. Our results suggest that high serum IGF-I levels just after ischemic stroke onset are associated with neurological recovery and a better functional outcome.

Effect of a high-protein diet on ghrelin, growth hormone, and insulin-like growth factor–I and binding proteins 1 and 3 in subjects with type 2 diabetes mellitus

We have developed a diet that over 5 weeks dramatically lowers plasma glucose in people with type 2 diabetes mellitus. This diet consists of 30% carbohydrate, 30% protein, and 40% fat and is referred to as a Low Biologically Available Glucose (LoBAG) diet. The diet also resulted in an approximately 30% increase in fasting insulin-like growth factor-I (IGF-I). Thus, we were interested in determining if the IGF-I elevation was due to an increase in ghrelin and growth hormone (GH) or to a change in IGF-I binding proteins (IGFBPs). Eight men with type 2 diabetes mellitus ingested a control diet (15% protein, 55% carbohydrate, and 30% fat) and a LoBAG(30) diet for 5 weeks in a randomized crossover design with a washout period in between. Before and after each 5-week period, subjects had blood drawn for total glycated hemoglobin and, at several time points over 24 hours, for GH, IGF-I, IGFBP-1, IGFBP-3, ghrelin, glucose, and insulin. Fasting and 24-hour glucose concentrations and total glycated hemoglobin were decreased, as expected (all Ps < .05). Fasting IGF-I increased by approximately 30% (P = .05) and remained unchanged throughout 24 hours. Ghrelin, GH, IGFBP-1, IGFBP-3, and insulin were not different between diets. Insulin and IGFBP-1 concentrations were reciprocal, as expected. Insulin-like growth factor-I binding protein 1 decreased as insulin increased to greater than approximately 30 to 40 μU/mL. Ingestion of a LoBAG(30) diet by weight-stable subjects with type 2 diabetes mellitus resulted in an increase in total IGF-I without an increase in ghrelin, GH, and IGFBP-3 or a change in IGFBP-1 regulation. The mechanism remains to be determined.

The growth hormone/insulin‐like growth factor‐I system in chronic heart failure and its interaction with adiponectin

The growth hormone/insulin‐like growth factor‐I system in chronic heart failure and its interaction with adiponectin

Impact of viral-mediated IGF-I gene transfer on skeletal muscle following cast immobilization.

Insulin-like growth factor I (IGF-I) is a potent myogenic factor that plays a critical role in muscle regeneration and muscle hypertrophy. The purpose of this study was to evaluate the effect of IGF-I overexpression on the recovery of muscle size and function during reloading/reambulation after a period of cast immobilization in predominantly fast twitch muscles. In addition, we investigated concomitant molecular responses in IGF-I receptor and binding proteins (BPs). Recombinant adeno-associated virus vector for IGF-I (rAAV-IGF-IA) was injected into the anterior compartment of one of the hindlimbs of young (3 wk) C57BL6 female mice. At 20 wk of age, both hindlimbs were cast immobilized in a shortened position for 2 wk to unload the tibialis anterior (TA) and extensor longus digitorum (EDL) muscles. The TA and EDL muscles were removed bilaterally after 2 wk of cast immobilization and after 1 and 3 wk of free cage reambulation. Increases in IGF-I mRNA and protein levels with IGF-I overexpression were associated with significant increases in muscle wet weight, fiber size, and tetanic force, although overexpression did not protect against cast immobilization-induced muscle atrophy. After 1 wk of reambulation, evidence of enhanced muscle regeneration was noted in IGF-I-overexpressing muscles with an increased prevalence of central nuclei, embryonic myosin, and Pax7 positive fibers. We also observed larger relative gains in muscle size (wet weight and fiber area), but not force, during the 3-wk reambulation period in hindlimb muscles overexpressing IGF-I compared with contralateral control legs. Changes in IGFBP-5 mRNA expression during cast immobilization and reambulation paralleled those of IGF-I, whereas IGFBP-3 expression changed inversely to IGFBP-5.

A cross-sectional analysis of the associations between adult height, BMI and serum concentrations of IGF-I and IGFBP-1 -2 and -3 in the European Prospective Investigation into Cancer and Nutrition (EPIC)

Background: Height and BMI are risk factors for several types of cancer and may be related to circulating concentrations of insulin-like growth factor-I (IGF-I), a peptide associated with increased cancer risk.Aim: To assess the associations between height, BMI and serum concentrations of IGF-I and IGF binding protein (IGFBP)-1, -2 and -3.Subjects and methods: This cross-sectional analysis included 1142 men and 3589 women aged 32–77 years from the multi-centre study, the European Prospective Investigation of Cancer and Nutrition (EPIC).Results: In men, there was a positive association between height and IGF-I; each 10 cm increment in height was associated with an increase in IGF-I concentrations of 4.3% (95% confidence interval (CI): 1.3–7.5%, p for trend = 0.005), but this association was not statistically significant for women (0.9%, 95% CI: − 0.7 to 2.6%, p for trend = 0.264). In both men and women, the association between IGF-I and BMI was non-linear and those with a BMI of 26–27 kg/m2 had the highest IGF-I concentration. BMI was strongly inversely related to concentrations of IGFBP-1 and IGFBP-2 in men and in women (p for trend for all < 0.001).Conclusion: Height and BMI are associated with IGF-I and its binding proteins, which may be mechanisms through which body size contributes to increased risk of several cancers.

Abstract 4830: Insulin-like growth factors and kidney cancer risk in men

Abstract Context: Causes of kidney cancer are not fully understood. Incidence is highest in those ages 50 to 70, and almost twice as high in men as in women. Smokers are twice as likely as non-smokers to develop renal cell carcinoma and about four times as likely to develop cancer of the renal pelvis. Insulin-like growth factor-I (IGF-I) has been shown to increase kidney microvascular growth and glomerular filtration rate, and its administration increases renal function in animal models of chronic renal failure, and has been proposed as a possible therapeutic agent (Hirschberg et al, 1998). However, the possible roles of IGF in the development of kidney cancer have not been well-studied. Objective: To examine the relation of serum levels of IGF-I and insulin-like growth factor binding protein 3 (IGFBP-3) to kidney cancer risk. Methods: We conducted a case-cohort study nested within the prospective Alpha-Tocopherol, Beta-Carotene Cancer Prevention (ATBC) Study of 29,133 Finnish male smokers who were 50-69 years of age and not diagnosed with cancer at study entry. Serum concentrations of IGF-I, IGFBP-3 were measured in blood samples collected in 1985 to 1988. One hundred men were identified who had a diagnosis of kidney cancer &amp;gt;5 years after blood collection through the end of 1997. Self-reported information on lifestyle and medical history was collected and weight and height were measured at baseline. Multivariable logistic regression models were used to estimate the relative risk of kidney cancer associated with IGF levels. Results: A history of hypertension (known to be increased in those who are older, overweight, or heavier smokers) was more common among cases than among noncases. Men with IGF-I levels &amp;gt;108 ng/mL were 63% less likely to develop kidney cancer than men with IGF-I levels ≤108 ng/mL (OR=0.37; 95% CI=0.20-0.69). IGFBP-3 levels did not alter the association between IGF-I and kidney cancer risk. Further, no association was observed between IGFBP-3 levels and the development of kidney cancer. Conclusions: Low serum IGF-I levels in this cohort of older middle-aged male smokers are associated with increased kidney cancer risk, independent of IGFBP-3, age, anthropometry, lifestyle and medical history. Further research is needed to confirm the findings and examine the association in women and non-smokers. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4830.

Local insulin-like growth factor I prevents sepsis-induced muscle atrophy

The present study tests the hypotheses that local bioavailability of insulin-like growth factor I (IGF-I) is capable of regulating muscle protein balance and that muscle-directed IGF-I can selectively maintain muscle mass during bacterial infection. Initial studies in C57BL/6 mice demonstrated that increasing or decreasing bioavailable IGF-I within muscle by local administration of either Leu 24 Ala 31 IGF-I or IGF binding protein 1, respectively, produced proportional changes in surrogate markers (eg, phosphorylation of 4E-BP1 and S6K1) of protein synthesis. We next examined the ability of a sustained local administration of IGF-I to prevent sepsis-induced muscle atrophy over a 5-day period. At the time of cecal ligation and puncture or sham surgery, mice had a time-release pellet containing IGF-I implanted next to the gastrocnemius and a placebo pellet placed in the contralateral limb. Data indicated that IGF-I released locally only affected the adjacent muscle and was not released into the circulation. Gastrocnemius from septic mice containing the placebo pellet was atrophied and had a reduced IGF-I protein content. In contrast, locally directed IGF-I increased IGF-I protein within adjacent muscle to basal control levels. This change was associated with a proportional increase in muscle weight and protein, as well as increased phosphorylation of 4E-BP1 and the redistribution of eIF4E from the inactive eIF4E∙4EBP1 complex to the active eIF4E∙eIF4G complex. Local IGF-I also prevented the sepsis-induced increase in atrogin-1 messenger RNA in the exposed muscle. Finally, local IGF-I prevented the sepsis-induced increase in muscle interleukin-6 messenger RNA. Thus, muscle-directed IGF-I attenuates the sepsis-induced atrophic response apparently by increasing muscle protein synthesis and potentially decreasing proteolysis. Collectively, our data suggest that agents that increase the bioavailability of IGF-I within muscle per se might be effective in ameliorating the sepsis-induced loss of muscle mass without having undesirable effects on metabolic processes in distant organs.

Insulin-like growth factor-I (IGF-I): Solution properties and NMR chemical shift assignments near physiological pH

Objective Insulin-like growth factor-I (IGF-I) plays important roles in normal growth and development, as well as in disease states, and its structure and function have been studied extensively using nuclear magnetic resonance (NMR) spectroscopy. However, IGF-I typically gives poor quality NMR spectra containing many broad peaks, because of aggregation at the protein concentrations generally required for NMR experiments as well as the internal dynamics of the molecule. The present study was undertaken to determine a reliable set of assignments under more physiological conditions. Design Several reports of chemical shift assignments have been published previously for IGF-I either bound to a ligand or at relatively low pH (∼3–4), but there are many contradictions among them, reflecting the poor behaviour of IGF-I. Low pH conditions are also suboptimal for the analysis of interactions between IGF-I and IGF binding proteins (IGFBP) or IGFBP fragments. Spectra were recorded at low concentrations in order to identify conditions of temperature and pH where all peaks could be observed. Results We show that good quality 2D 1H– 15N HSQC spectra of 15N-labelled IGF-I can be obtained at pH 6 and 37 °C, much closer to physiological conditions, by using lower IGF-I concentrations (0.05 mM). Surprisingly, at this concentration and temperature, spectra were of better quality at pH 6 than at pH 4, in contrast to previous observations made at millimolar concentrations of IGF-I. We were then also able to assign the chemical shifts of IGF-I at pH 6 and 37 °C using 3D heteronuclear spectra recorded on a 0.7 mM 15N/ 13C-labelled IGF-I sample. Conclusion These results provide a valuable resource for future studies of the structure, dynamics, folding, and binding interactions of IGF-I, as well as analogues thereof, by means of NMR spectroscopy.

Plasma Insulin-Like Growth Factor I Is Inversely Associated with Colorectal Adenoma Recurrence: A Novel Hypothesis

The insulin-like growth factor I (IGF-I) axis has been proposed to be a significant factor in the development of certain cancers, including colorectal. However, results from epidemiologic studies suggest modest effects on colorectal cancer risk. Using cross-sectional and prospective study designs within the same cohort of men who had at least one adenoma at baseline, we investigated whether plasma IGF-I, IGF-I binding protein 1, and IGF-I binding protein 3 were associated with colorectal adenoma characteristics at baseline and whether their levels were related to odds for adenoma recurrence. Plasma levels of each marker were measured at baseline in 299 male participants in the Wheat Bran Fiber Trial, who were followed prospectively for recurrence of their adenomatous lesions. In cross-sectional analyses, plasma IGF-I was significantly positively associated with the presence of adenomas with any villous features (P = 0.04). In contrast, IGF-I levels were inversely associated with odds of colorectal adenoma recurrence, with adjusted odds ratios (95% confidence interval) of 0.55 (0.29-1.01) and 0.49 (0.26-0.91) for the second and third tertiles of IGF-I, respectively, compared with the first tertile (P(trend) = 0.02). The inverse association was stronger for advanced adenoma recurrence (P(trend) = 0.02) than for nonadvanced recurrence (P(trend) = 0.10). These results suggest that, once an adenoma is removed, higher IGF-I levels reduce the odds of the formation of new lesions in the colorectum.

Insulin-like Growth Factor I Regulates Apoptosis in Condylar Cartilage

Endogenous insulin-like growth factor-I (IGF-I) is known to affect the growth and development of condylar cartilage. However, the critical effect of IGF-I on cell survival is still unknown. We hypothesized that endogenous IGF-I could regulate the survival of cells of the mandibular condylar cartilage. Mandibular condyles dissected from 12-day-old rats were cultured for 1, 3, and 5 days in medium containing antisense oligodeoxynucleotide (AS-ODN) for IGF-I. Real-time RT-PCR analysis showed that the levels of IGF-I and IGF binding protein (IGFBP)3 mRNAs in the AS-ODN group were significantly decreased. After 3 days' culture, the number of necrotic cells was observed in the undifferentiated mesenchymal cell layer. These cells were TUNEL-positive and confirmed to be apoptotic by electron microscopic observation. Immunoblotting revealed that expression of cleaved caspase3 was increased with AS-ODN. These results may suggest that the cells in the undifferentiated mesenchymal cell layer of the mandibular condyle require IGF-I for survival.

90 EVIDENCE OF A VASOPRESSIN-INDEPENDENT AQP2 EXPRESSION AND WATER RETENTION IN REFRACTORY ASCITES

Liver transplantation is the only curative treatment for advanced liver cirrhosis. Therapies aimed at halting the progression of the disease are urgently needed. Previous studies have shown that the administration of recombinant insulin like growth factor-I (IGF-I) induces hepatoprotective effects in experimental cirrhosis. However, the necessity of using high daily doses of the protein for a long period of time makes this therapy very costly hampering their clinical application. As an alternative therapeutic approach, we have evaluated whether sustained IGF-I expression within the liver from viral vectors based on the Simian Virus 40 (rSVIGF-I) could exert therapeutic effects in liver cirrhosis. We have previously shown that intraportal injection of rSVIGF-I in rats prior to the development of liver cirrhosis induces the expression of hepatocyte growth factor (HGF) in the liver and delays the progression of the disease. In the present study we have tested the effect of the vector in rats that had already developed advanced liver cirrhosis. Liver cirrhosis was induced in Sprague-Dawley male rats by intragastric administration of CCl4 for 12 weeks and then a single dose of rSVIGF-I (1011 vp/rat) was administered by different routes. The following administration routes were tested: intraportal (IP), intrahepatic (IH), intraarterial (IA) and intrabiliar (IB). At the end of the study, cirrhotic rats treated with rSVIGF-I showed reduced serum bilirubin, transaminases and liver fibrosis scores as well as increased expression of serum albumin as compared to mock-infected cirrhotic animals. The effects were more prominent in rats treated by IP or IA injection, suggesting that these routes could allow better access of the vector to hepatocytes in fibrotic livers. IGF-I expression correlated with the increase of mRNA levels of IGF-I binding protein 3 (whose synthesis is induced by IGF-I) and with upregulation of HGF, a factor that seems to mediate hepatoprotective effects of IGF-I. These results indicate that established cirrhosis can be reverted by IGF-I and also, that rSVIGF-I are promising vectors for the treatment of this disease.

The quantitative and functional relation between insulin‐like growth factor‐I (IGF) and IGF‐binding proteins during human osteoarthritis

A previous hypothesis stated that during osteoarthritis (OA) increased insulin-like growth factor (IGF) binding proteins (IGFBPs) sequester IGFs and limit their access to the cell. The objective of this article was to test this by: (1) quantifying IGF and IGFBP-3 as well as their ratios in human OA cartilages, and (2) measuring the metabolic responses of diseased cartilage to IGF-I and its IGFBP-insensitive analogs. Knee or hip OA cartilages were staged for OA by histology. Cartilage slices were either extracted for assays of IGF proteins, or maintained intact as organ cultures. Proteoglycan (PG) metabolism +/- IGFs was measured by use of the (35)S-sulfate precursor. IGFBP-3 (ng/mg protein) was weakly correlated with OA score by regression analysis (R(2) = 0.122; p = 0.040; n = 35). IGF-I (ng/mg protein) was constant across all OA groups (ANOVA; p = .428, n = 18) and the IGF-I/IGFBP-3 ratios were > 1 in most samples. All OA cartilages responded to hrIGF-I by increasing PG synthesis [average 2.29-fold +/- 0.55 (+/-SD) at saturation, n = 12] irrespective of OA score. The des (1-3) IGF-I analog (which lacks the three N-terminal amino acids) had similar maximal effects (average 2.23-fold stimulation +/- 0.71, n = 10), but it was more effective in two out of three samples at suboptimal doses. The effect of hrIGF-I, des (1-3) IGF-I, or the B-chain analog on degradation was minimal. In summary, catabolism was insensitive to IGF-I, and this was probably not due to IGFBPs. By contrast, IGF-I exerted a robust stimulation of anabolism at sufficiently high doses, even though IGFBPs could tone down the ligand effect at low doses.

Serum Levels of Insulin-like Growth Factor-I and Insulin-like Growth Factor-I Binding Protein-3: Quality Control for Studies of Stored Serum

The insulin-like growth factor (IGF) axis, particularly IGF-I and IGF binding protein-3 (IGFBP-3), has been the subject of much attention because of its role in juvenile growth and their association with cancers at several sites. However, epidemiologic studies of IGF-I and IGFBP-3 have had mixed results and several authors have speculated that quality control (QC), sample storage history, and other methodologic concerns could play a role in this heterogeneity. This article documents the results of storage history and QC efforts for a study of IGF-I and IGFBP-3 in 6,226 serum samples from the National Health and Nutrition Examination Survey III (NHANES III). The study was carried out on site at Diagnostic Systems Laboratories in Webster, Texas, using the IGF-I ELISA (DSL 10-5600) and the IGFBP-3 immunoradiometric assay (DSL 6600). A run-in study of assay performance suggested that plates, days, and weeks significantly affected the variance of both assays. Analysis of samples with different storage histories also indicated strong effects of storage history. Serum samples disbursed to laboratories for measurement of diverse analytes and then returned for storage showed reductions in serum IGF-I level averaging 43% and reductions in IGFBP-3 of 25% compared with samples shipped immediately to the repository for long-term storage at -80 degrees C. Therefore, the main study was carried out using samples that had been shipped directly to the National Center for Health Statistics/NHANES collection center for storage. Laboratory analyses of NHANES III and QC samples were carried out over approximately 10 months. QC was monitored through repeated testing of blood samples from six individuals, with two individuals tested twice on each plate. Assay performance was stable over the entire study and coefficients of variation averaged 2% to 3% within plates and approximately 14% for IGF-I and approximately 11.5% for IGFBP-3 over the entire study. Coefficients of variation varied significantly among individual QC subjects, ranging from 12.3% to 17.6% for IGF-I and 8.9% to 12.8% for IGFBP-3. Based on Levy-Jennings plots, approximately 5% of the plates used for IGF-I in the main study were out of compliance. Finally, location on a plate had small but significant effects on IGF-I level. Together, these results highlight the need for care in large studies of putative biomarkers for cancer risk and illustrate some probable sources of heterogeneity in past epidemiologic studies of the IGF axis and cancer.