SERUM LEVELS OF INSULIN-LIKE GROWTH FACTOR BINDING PROTEIN-3 IN BENIGN AND MALIGNANT BREAST DISEASE

Background : The insulin-like growth factors IGF-I and IGF-II and their major binding protein IGFBP-3 influence the growth of breast cancer cells in vitro. Some benign non-breast tumours appear to be associated with increased serum IGFBP-3 levels which would tend to reduce bioactive-free IGF concentrations. The present study investigates whether this pattern also occurs in neoplastic breast disease. Methods : Serum IGF-I, IGF-II and IGFBP-3 were measured by specific radioassay in 12 women with benign breast disease, 31 patients with breast cancer and in age-matched controls. Results : The mean (± SD) serum IGFBP-3 concentration was higher in benign breast disease (3.6 ± 0.7 mg/L) than in controls (2.7 ± 0.6 mg/L) or in breast cancer patients (2.7 ± 0.5 mg/L) (P = 0.001). Serum IGF-I and IGF-II levels were not significantly different among the groups. However, the index of free unbound IGF measured as the molar ratio of IGF-I plus IGF-II divided by IGFBP-3 was significantly lower in benign breast disease than in the other subjects. Conclusions : Either the production or clearance of IGFBP-3 is altered in benign breast disease so that there is less free IGF available to cells. This may serve to protect against malignant transformation in patients with benign breast disorders.     

Effect of Breast Surgery on Serum Levels of Insulin-Like Growth Factors (IGF-I, IGF-II, and IGF Binding Protein-3) in Women With Benign and Malignant Breast Lesions

Background: There is evidence that insulin-like growth factors play a role in the development of breast cancer. Antiestrogens reduce circulating levels of IGF-I, but the influence of other breast cancer treatments, including surgery, is unknown and is investigated in this study.Methods: Circulating serum concentrations of IGF-I, IGF-II, and IGF binding protein-3 (IGFBP-3) were measured before and after breast surgery in 31 patients with breast cancer and 12 controls with benign breast lesions. Serum albumin was measured as a marker of the nonspecific metabolic effect of surgery.Results: Serum IGF-I, IGF-II, IGFBP-3, and albumin fell 24 hours after surgery for breast cancer but largely normalized again over the next 7 days. The fall in IGF-I and IGFBP-3 was not significant when the change in serum albumin was used as a covariate, suggesting a nonspecific effect of surgery. However, the reduction in IGF-II remained significant when adjusted for albumin and was greater after lumpectomy of malignant tumors (–8 ± 2%) compared with benign disease (2 ± 2%, P = .001). The fall in IGF-II was significantly related to the size of the removed tumor.Conclusions: Breast cancer may directly influence the serum concentration of IGF-II, possibly by direct tumor production.     

Insulin-like growth factor system components in hyperparathyroidism and renal osteodystrophy

BACKGROUND: The insulin-like growth factor (IGF) system plays a key role in regulation of bone formation. In patients with renal osteodystrophy, an elevation of some IGF binding proteins (IGFBPs) has been described, but there is no study measuring serum levels of both IGF-I and IGF-II as well as IGFBP-1 to -6 in different forms of renal osteodystrophy and hyperparathyroidism. METHODS: In a cross-sectional study, we investigated 319 patients with mild (N = 29), moderate (N = 48), preuremic (N = 37), and end-stage renal failure (ESRF; N = 205). The ESRF group was treated by hemodialysis (HD; N = 148), peritoneal dialysis (PD; N = 27), or renal transplantation (RTX; N = 30). As controls without renal failure, we recruited age-matched healthy subjects (N = 87) and patients with primary hyperparathyroidism (pHPT; N = 25). Serum levels of total and free IGF-I, IGF-II, IGFBP-1 to -6, and biochemical bone markers including intact parathyroid hormone (PTH), bone alkaline phosphatase (B-ALP), and osteocalcin (OSC) were measured by specific immunometric assays. IGF system components and bone markers were correlated with clinical and bone histologic findings. Mean values +/- SEM are given. RESULTS: With declining renal function a significant increase was measured for IGFBP-1 (range 7- to 14-fold), IGFBP-2 (3- to 8-fold), IGFBP-3 (1.5- to 3-fold), IGFBP-4 (3- to 19-fold), and IGFBP-6 (8- to 25-fold), whereas IGFBP-5 levels tended to decrease (1.3- to 1. 6-fold). In contrast, serum levels of IGF-I, free IGF-I, and IGF-II remained constant in most patients. Compared with renal failure patients, pHPT patients showed a similar decline in IGFBP-5 levels and less elevated levels of IGFBP-1 (3.5-fold), IGFBP-2 (2-fold), IGFBP-3 (1.2-fold), and IGFBP-6 (4-fold) but no elevation of IGFBP-4 levels. In all subjects, free and total IGF-I levels showed significant negative correlations with IGFBP-1, IGFBP-2, and IGFBP-4 (that is, inhibitory IGF system components) and significant positive correlations with IGFBP-3 and IGFBP-5 (that is, stimulatory IGF system components). A positive correlation was observed between IGF-II and IGFBP-6. ESRF patients with mixed uremic bone disease and histologic evidence for osteopenia revealed significantly (P < 0.05) higher levels of IGFBP-2 and IGFBP-4 but lower IGFBP-5 levels. Histologic parameters of bone formation showed significant positive correlations with serum levels of IGF-I, IGF-II, and IGFBP-5. In contrast, IGFBP-2 and IGFBP-4 correlated positively with indices of bone loss. Moreover, dialysis patients with low bone turnover (N = 24) showed significantly (P < 0.05) lower levels of IGFBP-5, PTH, B-ALP, and OSC than patients with high bone turnover. CONCLUSION: Patients with primary and secondary hyperparathyroidism showed lower levels of the putative stimulatory IGFBP-5 but higher levels of IGFBP-1, -2, -3, and -6, whereas total IGF-I and IGF-II levels were not or only moderately increased. The marked increase in serum levels of IGFBP-4 appeared to be characteristic for chronic renal failure. IGFBP-5 correlated with biochemical markers and histologic indices of bone formation in renal osteodystrophy patients and was not influenced by renal function. Therefore, IGFBP-5 may gain significance as a serological marker for osteopenia and low bone turnover in long-term dialysis patients.     

Serum-free insulin-like growth factor I correlates with clearance in patients with chronic renal failure

Serum-free insulin-like growth factor I correlates with clearance in patients with chronic renal failure. BACKGROUND: Chronic renal failure (CRF) results in major changes in the circulating growth hormone (GH)/insulin-like growth factor (IGF) system. However, there are only limited data on changes in free IGF-I in CRF. METHODS: Matched groups of nondiabetic, nondialyzed patients with CRF (N = 25) and healthy controls (N = 13) were compared. The creatinine clearance (CCr) based on a 24-hour urine collection ranged from 3 to 59 and 89 to 148 ml/min/1.73 m2 in patients and controls, respectively. Overnight fasting serum samples were analyzed for free and total IGF-I and -II, and IGF-binding protein (IGFBP)-1, -2, and -3. Additionally, intact as well as proteolyzed IGFBP-3 was determined. RESULTS: The patients had reduced serum-free IGF-I (-53%) and increased levels of total IGF-II (40%), IGFBP-1 (546%), and IGFBP-2 (270%, P < 0.05). Serum total IGF-I and free IGF-II were normal. Also, serum levels of immunoreactive IGFBP-3 were elevated (33%, P < 0.05), but this could be explained by an increased abundance of IGFBP-3 fragments, as ligand blotting showed no difference in levels of intact IGFBP-3. Accordingly, patients had an increased proteolysis of IGFBP-3 in vivo (17%) and in vitro (7%, P < 0.05). In patients, free IGF-I levels correlated positively with CCr (r2 = 0.38, P < 0.002) and inversely with IGFBP-1 (r2 = 0.69, P < 0. 0001) and IGFBP-2 (r2 = 0.41, P < 0.0007), whereas CCr was inversely correlated with levels of IGFBP-1 (r2 = 0.48, P < 0.0001) and IGFBP-2 (r2 = 0.63, P < 0.0001). CONCLUSIONS: These data strongly support the hypothesis that CRF-related growth failure and tissue catabolism are caused by an increased concentration of circulating IGFBP-1 and -2, resulting in low serum levels of free IGF-I and thus IGF-I bioactivity. In addition, low levels of free IGF-I may explain the increased secretion of GH in CRF.     

Insulin-like growth factors and risk of benign prostatic hyperplasia

BACKGROUND: Insulin-like growth factors (IGFs) have potent growth mitogenic and anti-apoptotic effects on prostate tissue, whereas IGF binding proteins (IGFBPs) inhibit growth of prostatic tissue. The IGF axis has been implicated in prostate cancer risk, but its role in benign prostatic hyperplasia (BPH) is unclear. METHODS: Plasma levels of IGF-I, IGF-II, IGFBP-1, and IGFBP-3 were determined from the fasting bloods of 206 BPH cases admitted for treatment and 306 randomly selected population controls in Shanghai, China. RESULTS: Relative to the lowest tertile, men in the highest tertile of IGF-I levels had a significantly elevated risk of BPH (odds ratio [OR] = 2.80, 95% confidence interval [95% CI] = 1.60-4.92; P(trend) < 0.001). Results for IGF-I were more pronounced after adjustment for serum androgens. In contrast, men in the highest IGFBP-3 tertile had a significantly reduced risk (OR = 0.40; 95% CI = 0.23-0.69; P(trend) < 0.001). No associations of BPH with IGF-II and IGFBP-1 were observed. CONCLUSION: As has been previously observed for prostate cancer, we found that IGF-I and IGFBP-3 are associated with BPH risk in China. Further investigation is needed to elucidate the role of the IGF axis in BPH etiology.     

Evaluation of IGF system component levels and mitogenic activity of uremic serum on normal human osteoblasts

To test the hypothesis that impairment in bone formation in renal osteodystrophy in adults with chronic renal failure (CRF) might be mediated in part by alterations in circulating levels of the insulin-like growth factor (IGF) system components, we compared serum levels of IGF-I, IGF-II, IGF-binding protein (IGFBP)-3, IGFBP-4 and IGFBP-5 in adults with CRF (CRF patients with parathyroid hormone (PTH) < 100 pg/ml, PTH > 300 pg/ml and end-stage renal failure (ESRF) patients) versus age-matched controls. To evaluate the biological significance of alterations in circulating level of IGF system components, we compared the mitogenic activity of the sera on proliferation of normal human osteoblasts in vitro by using [(3)H]thymidine incorporation. We found severalfold increased serum levels of IGFBP-3 (2-fold), IGFBP-4 (5-fold) and slightly increased IGF-II levels in ESRF patients as well as a 2.6-fold increase in free IGF-I in CRF patients with PTH < 100 pg/ml. The mitogenic activity was found to be increased in serum of kidney failure patients compared to controls. This was most pronounced in CRF patients with PTH < 100 pg/ml showing also a significant increase in free IGF-I and the lowest levels of the IGF-inhibitory IGFBP-4. Our data support the hypothesis that alterations in serum levels of stimulating (i.e. free IGF-I) and inhibitory IGF system components (i.e. IGFBP-4) may influence osteoblastic cell proliferation in renal osteodystrophy.     

Serum insulin-like growth factor-I and insulin-like growth factor-binding protein-3 in localized, metastasized prostate cancer and benign prostatic hyperplasia

OBJECTIVE: Insulin-like growth factors (IGF-I and IGF-II) are important mitogenic peptides and are thought to be significant factors involved in normal and malignant cellular proliferation including benign prostatic hyperplasia (BPH) and prostate cancer (PC). In particular, the association between IGF-I and PC has received much attention. Insulin-like growth factor binding protein-3 (IGFBP-3) is the major carrier protein in serum for the IGF-I, thus is an important functional modulator of it. On the other hand, one of the functions of prostate-specific antigen (PSA) is to cleave IGFBP-3. Epidemiological studies have shown that decreased levels of serum IGFBP-3 are associated with increased PC risk. Controversial results have also been reported on the value of serum IGF-I and/or IGFBP-3 in the detection of PC, especially of metastatic PC; as increased, decreased or unchanged when compared to BPH. The aim of the present study was to investigate whether serum IGF-I and IGFBP-3 levels change in localized and metastasized PC cases compared with BPH as the control cases. METHOD: The study included 45 BPH, 24 localized PC and 19 metastasized PC cases. Serum IGF-I and IGFBP-3 levels were measured by two-site immunoradiometric assay kits, and serum total and free PSA levels were assayed by chemiluminescence method. RESULTS: Serum IGF-I levels in both localized and metastasized PC cases were similar to BPH cases (138.3 +/- 58.2, 137.7 +/- 39.0 and 147.7 +/- 44.2 ng/ml, respectively), whereas serum IGFBP-3 levels were lower in metastasized PC group than in BPH group (1,795.6 +/- 305.6 and 2,196.0 +/- 505.7 ng/ml; p = 0.005). In localized PC, serum IGFBP-3 levels (1,911.00 +/- 349.58 ng/ml) were similar to metastasized PC. There were significant correlations between serum IGFBP-3 and serum free PSA in three groups (r = -0.46, p = 0.02 for localized PC; r = -0.56, p = 0.01 for metastasized PC, and r = -0.31, p = 0.03 for BPH). CONCLUSION: These data reveal that serum IGF-I levels may not change either in localized or metastasized PC, and that decreased serum IGFBP-3 levels may be attributed to its proteolysis by PSA which is increased in PC.     

Serum insulin-like growth factors and their binding proteins in children with end-stage renal disease

Serum levels of insulin-like growth factor-I (IGF-I), IGF-II, and IGF binding protein-1 (IGFBP-1), IGFBP-2, and IGFBP-3 were measured in 54 children with end-stage renal disease (ESRD). The results were compared with their respective age-dependent normal ranges. IGFs and IGFBPs were quantified by specific radioimmunoassay. Serum IGF-I in children with ESRD tended to cluster in the low-normal range. Mean age-related serum IGF-I levels were slightly, but significantly decreased (–1.08±0.17 SDS). In view of the prevailing elevated growth hormone levels in ESRD, these serum, IGF-I levels must be interpreted as inadequately low. In contrast to IGF-I, individual serum IGF-II levels were either in the uppernormal range or clearly elevated. Mean age-related IGF-II (1.09±0.15 SDS) was lightly, but significantly elevated. Mean age-related IGFBP-1 serum levels (2.20±0.10 SDS) were moderately increased, while mean age-related serum IGFBP-2 (5.65±0.36) and IGFBP-3 levels (3.60±0.19) were markedly elevated. Affinity cross-linking of¹²⁵iodine-IGF-II to sera from patients with ESRD and immunoprecipitation with a specific antiserum showed that low molecular weight IGFBP-3 fragments in ESRD serum are capable of binding IGF. In patients with ESRD, a rapid and persistent decline of immunoreactive IGFBP-3 in response to restoration of renal function by renal transplantation was observed. This finding indicates that renal dysfunction contributes to high immunoreactive, IGFBP-3 levels in ESRD. In conclusion, the imbalance between normal total IGF levels and the excess of IGFBPs in ESRD is likely to play a role in growth failure in these children.     

Growth hormone/insulin-like growth factor system in children with chronic renal failure

Disturbances of the somatotropic hormone axis play an important pathogenic role in growth retardation and catabolism in children with chronic renal failure (CRF). The apparent discrepancy between normal or elevated growth hormone (GH) levels and diminished longitudinal growth in CRF has led to the concept of GH insensitivity, which is caused by multiple alterations in the distal components of the somatotropic hormone axis. Serum levels of IGF-I and IGF-II are normal in preterminal CRF, while in end-stage renal disease (ESRD) IGF-I levels are slightly decreased and IGF-II levels slightly increased. In view of the prevailing elevated GH levels in ESRD, these serum IGF-I levels appear inadequately low. Indeed, there is both clinical and experimental evidence for decreased hepatic production of IGF-I in CRF. This hepatic insensitivity to the action of GH may be partly the consequence of reduced GH receptor expression in liver tissue and partly a consequence of disturbed GH receptor signaling. The actions and metabolism of IGFs are modulated by specific high-affinity IGFBPs. CRF serum has an IGF-binding capacity that is increased by seven- to tenfold, leading to decreased IGF bioactivity of CRF serum despite normal total IGF levels. Serum levels of intact IGFBP-1, -2, -4, -6 and low molecular weight fragments of IGFBP-3 are elevated in CRF serum in relation to the degree of renal dysfunction, whereas serum levels of intact IGFBP-3 are normal. Levels of immunoreactive IGFBP-5 are not altered in CRF serum, but the majority of IGFBP-5 is fragmented. Decreased renal filtration and increased hepatic production of IGFBP-1 and -2 both contribute to high levels of serum IGFBP. Experimental and clinical evidence suggests that these excessive high-affinity IGFBPs in CRF serum inhibit IGF action in growth plate chondrocytes by competition with the type 1 IGF receptor for IGF binding. These data indicate that growth failure in CRF is mainly due to functional IGF deficiency. Combined therapy with rhGH and rhIGF-I is therefore a logical approach.This work was presented in part at the IPNA Seventh Symposium on Growth and Development in Children with Chronic Kidney Disease: The Molecular Basis of Skeletal Growth, 1–3 April 2004, Heidelberg, Germany     

Bone Mineral Density in Femoral Neck is Positively Correlated to Circulating Insulin-Like Growth Factor (IGF)-I and IGF-Binding Protein (IGFBP)-3 in Swedish Men

Studies on the hormonal regulation of bone metabolism in men have indicated covariation between insulin-like growth factor-I (IGF-I) and sex hormones with bone mineral density (BMD). In this study the relationships between BMD in total body, lumbar spine, femoral neck, distal and ultradistal (UD) radius and circulating levels of IGFs, IGF binding proteins (IGFBPs), and sex steroids were investigated in 55 Swedish men between 22 and 85 (52 +/- 18, mean +/- SD) years of age. BMD in total body, distal and UD radius, and femoral neck was positively correlated with serum IGF-I (r = 0.31 to 0.49), IGF-II (r = 0.32 to 0.48), IGFBP-3 (r = 0.37 to 0.53), and free androgen index (FAI) (r = 0.32 to 0.40), and negatively with IGFBP-1 (r = -0.37 to -0.41) and IGFBP-2 (r = -0.29 to -0.41) levels. A positive correlation was observed between BMD in femoral neck and estradiol/SHBG ratio (r = 0.34, P = 0.01). Age correlated negatively with serum IGF-I, IGF-II, IGFBP-3, FAI, estradiol/SHBG ratio, and BMD in total body, distal and UD radius, and femoral neck, and positively with IGFBP-1, IGFBP-2, and SHBG levels. According to stepwise multiple regression analyses, a combination of weight, IGFBP-3, and testosterone accounted for 43% of the variation in BMD in femoral neck, 34% in ultradistal radius and 48% in total body (P < 0.0001). These findings indicate that sex hormones and the different components of the IGF system are associated with BMD in Swedish men, suggesting that age-related changes in these systems could contribute to the development of osteoporosis in elderly men.     

IGF-I and IGFBP-3 polymorphisms and risk of prostate cancer

BACKGROUND: Insulin-like growth factor-I (IGF-I) is a potent mitogen for both normal and malignant prostate epithelial cells. The majority of circulating IGF-I is bound in a complex with IGF binding protein-3 (IGFBP-3), which in turn limits IGF-I bioavailability. Multiple studies suggest that higher IGF-I and/or lower IGFBP-3 serum levels are positively associated with prostate cancer risk. Several polymorphisms within the IGF-I and IGFBP-3 coding regions have been associated with increased serum protein levels. METHODS: To ascertain the potential relationship between serum levels and polymorphism, and prostate cancer risk, we investigated the role of two polymorphisms the IGF-I cytosine-adenosine (CA)-repeat and the IGFBP-3 Ala32Gly, and prostate cancer in a population-based, case-control, study of middle-aged men. RESULTS: We found no significant association between the IGFBP-3 Ala32Gly polymorphism and prostate cancer risk, even though the presence of at least one Gly allele did correlate with increased serum levels of IGFBP-3. For IGF-I, more controls (42%) than cases (38%) were homozygous for 19-CA-repeats (odds ratio, OR = 0.85; 95% confidence interval (CI) = 0.66-1.09). After stratifying by disease characteristics, 19-CA-repeat homozygous men displayed a decreased risk of low-grade disease (OR = 0.50; 95% CI = 0.27-0.93), but no associations were observed with more aggressive features of disease. Additionally, there was no correlation between mean serum IGF-I protein levels and IGF-I genotype in controls. CONCLUSIONS: Further evaluation of the IGF-I CA-repeat polymorphism and prostate cancer is necessary to determine if the modest risk reduction associated with the 19-CA-repeat homozygous state is observed in other study populations.     

Down-regulation of the serum stimulatory components of the insulin-like growth factor (IGF) system (IGF-I, IGF-II, IGF binding protein [BP]-3, and IGFBP-5) in age-related (type II) femoral neck osteoporosis.

Both a decrease in bone formation and an increase in bone resorption have been implicated in the pathogenesis of age-related (type II) femoral neck osteoporosis. While the increase in the bone resorption rate has been shown to be partially related to secondary hyperparathyroidism, the mechanisms underlying the decline in bone formation have not yet been identified. The aim of the present study was to test the hypothesis that the bone formation deficit associated with type II osteoporosis might be due to secondary hyperparathyroidism and/or to a deficiency of the insulin-like growth factor (IGF) system. Circulating concentrations of IGF-I, IGF-II, IGF binding protein (IGFBP)-3, IGFBP-4, IGFBP-5, 25-hydroxycholecalciferol (25(OH)D3), and intact parathyroid hormone (PTH) were measured in 50 elderly women after sustaining a hip fracture and in 50 healthy age-matched controls. In addition, serum levels of osteocalcin (OC), skeletal alkaline phosphatase, and N-terminal procollagen peptide and urinary pyridinium cross-links were determined as markers of bone remodeling, and bone mineral density (BMD) was assessed at the proximal femur. In the patient group, serum was drawn within 18 h of the fracture and prior to surgery. Circulating protein concentrations did not change over this time frame. No difference was found between mean IGFBP-4 serum levels in the two groups studied, while mean levels of IGF-I, IGF-II, IGFBP-3, IGFBP-5, 25(OH)D3, and markers of bone formation were significantly lower (p < 0.006) in patients as compared with healthy subjects. Serum PTH and urinary pyridinium cross-links, however, were markedly increased (p < 0.001) in the osteoporotic group. In pooled data from the normal and osteoporotic populations, age-adjusted multiple regression models based on IGF-I, IGF-II, IGFBP-3, and IGFBP-5 were found to be highly predictive of serum OC (R2 = 19%, p < 0.001) and BMD of femoral neck (R2 = 49%, p < 0.0001), consistent with an effect of the anabolic IGF components on overall bone formation rate. Similar models based on 25(OH)D3 and PTH, however, were statistically unrelated to OC. To address further the potential impact of trauma on circulating IGF system components, we measured IGF system component levels in 10 male patients within 18 h following tibial fracture and in 10 age-matched normal male subjects. There was no significant difference in serum level of any of the IGF system components between the two groups. Although limited by its cross-sectional design, the present study suggests that, in addition to bone resorption resulting from secondary hyperparathyroidism, impaired bone formation associated with deficiency of the IGF system might predispose elderly women to fragility fracture of the proximal femur.     

IGF and IGF-binding protein system in the synovial fluid of osteoarthritic and rheumatoid arthritic patients

Various arthritic disorders result from a disruption of the equilibrium between the synthesis and degradation of tissue matrix macromolecules. Growth factors, particularly insulin-like growth factor-I (IGF-I), are believed to play an important role in maintaining this equilibrium. In this study, we determined the levels of IGF-I, IGF-II, and characterized and measured the amount of IGF-binding proteins (IGFBPs) in the synovial fluid (SF) of osteoarthritis (OA), rheumatoid arthritis (RA) patients and normal individuals. Furthermore, we characterized the IGFBP found in these SFs. The levels of IGF-I, IGF-II and IGFBP-3 were determined by specific radioimmunoassays (RIAs). IGFBP identification and measurement were carried out using the Western ligand blot (WLB) technique, and characterization performed by Western immunoblot. IGFBP-3 proteolysis was analyzed by autoradiography after incubation of SF with radiolabeled IGFBP-3. Results showed a statistically significant increase (P < 0.001) in the IGF-I level in arthritic SF vs normal controls; 75 +/- 11 ng/ml and 82 +/- 11 ng/ml were recorded for RA (N = 8) and OA (N = 10), respectively, whilst normal controls (N = 9) were at 19 +/- 7 ng/ml. No difference in the level of IGF-II was recorded between the three groups studied. Human SF demonstrated the presence of IGFBP-1, -2, -3 and -4, but not that of IGFBP-5 and -6. The level of IGFBP-3 tested either by WLB or RIA was significantly higher (P < 0.001) in RA and OA patients. Moreover, a statistical and positive correlation between the levels of IGF-I and IGFBP-3 was noted. WLB analysis indicated that the amount of IGFBP-1 did not vary among the groups. The levels of IGFBP-2 and -4 were significantly increased (P < 0.02) solely in the RA SF. Further experiments demonstrated that a limited IGFBP-3 proteolysis occurred in human SF. Moreover, the ratio of total IGF over total bioactive IGFBPs was lower in RA (P < 0.05), and to a lesser extent in OA than normal specimens. This study showed the presence of four IGFBPs (1 4) in human SF for which the IGFBP-2, -3 and -4 were enhanced in arthritic fluid. Importantly, although proteolysis occurred in the SF, an increased amount of bioactive IGFBPs were present in arthritic SF, which may affect the bioavailability of IGF-I within the articular tissues.     

Characterization of insulin-like growth factors and their binding proteins in peritoneal dialysate

.Serum insulin-like growth factors (IGFs), which circulate bound to specific IGF binding proteins (IGFBPs), must exit the intravascular space before acting on target tissues. Little is known about the nature of IGF/IGFBPs in extravascular fluids of patients with chronic renal failure (CRF). Peritoneal dialysate (PD) was studied since, after a short incubation, PD contains proteins which have entered an extravascular space; thus, IGF/IGFBP forms in PD are more likely than serum forms to interact with target tissues. IGF-I and IGF-II, and IGFBPs 1 – 4, were readily identified by specific immunoassays and/or ¹²⁵iodine-IGF ligand blotting of simultaneously obtained PD and serum samples from seven CRF children; IGFBP-3 was a major IGFBP in PD as in serum. Where quantitated, IGF and IGFBP levels in PD were approximately 10% of serum concentrations. After separation of PD and serum by size-exclusion chromatography, serum had more IGFBP-3 in 150-kilodalton (kDa) than 35-kDa fractions, while PD had far less IGFBP-3 in 150-kDa than 35-kDa fractions. Immunoblot studies revealed a major 29-kDa IGFBP-3 fragment, in addition to intact 41- and 38-kDa IGFBP-3 forms, in PD and CRF serum; the 29-kDa form predominated in the 35-kDa PD fractions. These data suggest that the 29-kDa fragment is the IGFBP-3 form most likely to modulate IGF effects on target tissues of CRF individuals. Received: April 17, 1995; received in revised form September 19, 1995; accepted October 12, 1995     

mRNA expression of the IGF system in the kidney of the hypersomatotropic rat

AIM: To examine the response of the insulinlike growth factor (IGF) system in the kidney during a state of extreme growth. METHODS: We studied the mRNA expression of IGF-I, IGF-I receptor, and IGF-binding proteins (BP) using sensitive RNase protection assays following subcutaneous implantation of growth hormone pituitary cells (GH(3)) in rats. RESULTS: Within 5 weeks, the serum GH levels increased from 18.0 +/- (SE) 5.0 ng/ml in control animals to 389.8 +/- 30.3 ng/ml in GH(3) rats (n = 5, p < 0.001). The circulating IGF-I levels were also elevated. The kidney weights increased from 0.74 +/- 0.01 g in controls to 1.06 +/- 0.03 g in GH(3) animals (n = 5, p < 0.001). Similar changes were observed at week 10. The renal IGF-I mRNA averaged 1.0 +/- (SD) 0.33 relative densitometry units in controls (n = 4) and increased to 2.11 +/- 0.13 relative densitometry units in GH(3) rats (n = 5, p < 0.001). On the other hand, mRNA for the type I IGF receptor decreased in hypersomatotropic rats. Messenger RNAs for IGFBP-1 and IGFBP-4, which have been localized to renal tubules, both decreased significantly following growth induction, while IGFBP-3, the mRNA of which has an interstitial localization, was increased at week 10. CONCLUSION: These data suggest that there is a dynamic relationship between tubular and interstitial compartments with regard to the IGF system in the kidney which may be important in the regulation of the cell mass.     

Serum levels of IGF-1 and IGFBP-3 during adjuvant chemotherapy for primary breast cancer

High serum concentrations of insulin-like growth factor-1 (IGF-1) are associated with an increased risk of breast, prostate, colorectal, and lung cancer whereas IGF binding protein-3 (IGFBP-3) seems to exert a protective effect. Therefore, patients may benefit from low IGF-1 levels and high IGFBP-3 levels. This study evaluated whether adjuvant anthracycline-containing chemotherapy modulates IGF-1 and/or IGFBP-3 serum levels in breast cancer patients. In 18 patients undergoing adjuvant treatment for primary breast cancer, IGF-1 and IGFBP-3 serum levels were measured with immunoassays during chemotherapy regimens of either 5-fluorouracil, epirubicin and cyclophosphamide (FEC) or epirubicin and cyclophosphamide (EC). Mean pre-treatment values of IGF-1 and IGFBP-3 were 124+/-13 and 3698+/-186 ng/ml, respectively. No significant changes in IGF-1 and IGFBP-3 serum concentrations were observed during adjuvant anthracycline-containing chemotherapy. IGF-1 levels significantly correlated with IGFBP-3 levels before and during chemotherapy. In conclusion, these chemotherapy regimens do not seem to modulate IGF-1 or IGFBP-3 levels in a favourable or unfavourable way.     

Decreased levels of IGF binding protein-3 in serum from children with Perthes' disease

The concentrations of insulin-like growth factor (IGF)-I and IGF-binding protein (IGFBP)-3 in serum obtained from 27 children with Perthes' disease and 10 age-matched control subjects were measured by radioimmunoassay (RIA). IGFBPs were also analyzed by a Western ligand blotting (WLB) method. The bone age was determined in 18 patients from hand-wrist radiographs. Serum levels of IGFBP-3 but not IGF-I were significantly lower than those in normal controls. WLB showed a decrease in the intensity of the IGFBP-3 band in 19 of the 27 patients. The bone age was delayed, 2 years or more compared with the chronological age in 7 of 18 patients, and all of them, except 1, showed decreased levels of IGFBP-3 on WLB. We conclude that there may be disturbances in availability of IGFs in some patients with Perthes' disease.     

Peritoneal loss of insulin-like growth factor-I and binding proteins in end-stage renal disease

The kinetics of peritoneal transport of insulin-like growth factor (IGF) system-related proteins during dialysis is not well characterized. We studied temporal changes in dialysate and serum concentrations of IGF-I and IGF-II as well as IGF binding protein (BP)-1, -2, and -3 in ten children with end-stage renal disease (ESRD) undergoing continuous cycling peritoneal dialysis (CCPD) during a 4-h peritoneal equilibration test (PET). Dialysate concentrations of IGF-I, IGF-II, and all three IGFBPs demonstrated a time-dependent increase during PET. Despite their transport, the serum concentrations of these proteins did not change significantly during the PET. Dialysate/serum ratios for IGF-I, IGF-II, and IGFBP-1, -2, and -3 were significantly increased at 2 h and increased further at 4 h, at which time values averaged 1.3±0.2%, 3.1±0.5%, 6.2±1.0%, 2.4±0.2%, and 1.3±0.2% of serum levels, respectively. The transperitoneal clearance (μl/min per 1.73 m²) of the three IGFBPs was inversely related to both their molecular weight and plasma concentration. However, peritoneal clearance of IGF-I and -II was similar to that of the larger and more-abundant IGFBP-3. Mass transfer rates (μg/h per 1.73 m²) for the IGFs and their binding proteins were directly proportional to their prevailing plasma concentration. Based on estimates of mass transfer, only a small molar excess of IGFBPs was removed from the circulation relative to the combined molar concentration of IGF-I and IGF-II. Hence, it seems unlikely that any beneficial effect of CCPD on growth in children with ESRD is mediated via a preferential loss of IGFBPs into the dialysate fluid. Received August 15, 1997; received in revised form January 7, 1998; accepted January 9, 1998