Plasma IGF-binding Protein-3 Levels Research Articles

IGFBP3 inhibits tumor growth and invasion of lung cancer cells and is associated with improved survival in lung cancer patients

The insulin-like growth factor (IGF)-pathway is involved in tumor cell proliferation, metastasis, and survival. We aimed to find out what effects IGF binding protein 3 (IGFBP3) exerted on H1299 lung cancer (LC) cells in terms of tumor growth and invasion and whether IGFBP3 was associated with clinical and pathological parameters in a prospective cohort of LC patients. H1299 cells were transfected with an IGFBP3-expressing vector. Its influence on apoptosis induction via flow cytometry annexin V FITC assay, cell proliferation in 2D and 3D cell culture, and invasion were examined. Expression of several matrix metalloproteinases (MMPs) and inhibitors (TIMP-1) were also investigated in IGFBP3-transfected LC cells. Further, data on LC patients (n = 131), tumor characteristics, and survival were prospectively collected and correlated with IGFBP3 plasma levels. IGFBP3 did not influence apoptosis induction and 2D cell proliferation. However, both spheroid growth (3D proliferation) and invasion of IGFBP3-transfected cells planted in an extracellular matrix-based gel were significantly inhibited. IGFBP3 inhibited MMP-1 release, and the total MMP activity. In LC patients, higher IGFBP3 plasma levels correlated with both lower clinical tumor stage, grading, Ki-67 staining, and the absence of necrosis (P < 0.05, respectively). Increased IGFBP3 plasma levels were associated with improved overall survival (hazard ratio 0.37, P = 0.01). In conclusion, overexpressed IGFBP3 in a LC cell line inhibited tumor growth and invasion. Translating from bench to bedside, investigation of clinicopathological parameters confirmed these experimental results showing that higher IGFBP3 plasma levels were associated with less aggressive tumor growth, reduced tumor spread, and improved survival of LC patients.

IGF1 and IGFBP3 in acute respiratory distress syndrome

IGF1 and its most abundant binding protein, IGF-binding protein 3 (IGFBP3), have been implicated in fibrotic lung diseases and persistent acute respiratory distress syndrome (ARDS) due to profibrogenic and antiapoptotic activity. Whether circulating levels of IGF1 and IGFBP3 are altered in ARDS and whether they predict progression of and survival from ARDS remains unknown. This study aims to characterize the circulating levels of IGF1 and IGFBP3 in patients at risk for ARDS in relation to i) development of ARDS and ii) mortality among ARDS cases. In this case-cohort study, consecutive patients with risk factors for ARDS admitted to the intensive care unit were enrolled and followed prospectively for the development of ARDS. Cases were followed for all-cause mortality through day 60. Of the 2397 patients enrolled in the parent study, plasma samples were available in 531 (22%) patients (356 controls and 175 cases) from early in presentation. Total plasma IGF1 and IGFBP3 levels were measured. After adjusting for relevant clinical covariates including severity of illness, IGF1 and IGFBP3 levels were significantly lower in ARDS cases than in controls (odds ratio (OR), 0.58; P=0.006; OR, 0.57; P=0.0015 respectively). Among the ARDS cases, IGF1 and IGFBP3 levels were significantly lower in the 78 (45%) non-survivors (hazard ratio (HR), 0.70; P=0.024; HR, 0.69; P=0.021 respectively). Lower circulating levels of IGF1 and IGFBP3 were independently associated with ARDS case status. Furthermore, lower levels were associated with mortality among the ARDS cases. These data support the role of the IGF pathway in ARDS.

Influence of IGFBP3 Gene Polymorphisms on IGFBP3 Serum Levels and the Risk of Prostate Cancer in Low-risk Korean Men

To understand the relationship between the -202 A/C single-nucleotide polymorphism (SNP) of the insulin-like growth factor-binding protein 3 (IGFBP3) gene, IGFBP3 serum levels, and risk of prostate cancer (PCa) in a Korean population, as a potential reason for the lower incidence of PCa in the Korean population. The IGFBP3 levels were measured and the -202 A/C SNP of the IGFBP3 gene was typed for 225 PCa cases and the same number of matched controls. Linear regression analysis and unconditional logistic regression analysis were used to test for the associations between the genotypes and the circulating IGFBP3 levels and the risk of PCa, respectively. To adjust for the potential bias introduced by the hospital cohort, the result of the genotyping was compared with that of 683 community-indwelling healthy men. Significantly lower plasma levels of IGFBP3 were noted in the PCa cases. Lower IGFBP3 plasma levels were associated with an increased number of C alleles (P<.001). Compared with the PCa cases, a lower frequency of the C allele was found in the hospital and community controls (P<.05). Compared with AA genotype, logistic regression analysis revealed an increased risk of PCa in subjects who were CC genotype (odds ratio: 2.39, 95% confidence interval: 1.05-5.48). Larger odds (odds ratio: 3.37, 95% confidence interval: 1.35-8.43) for PCa were associated with CC genotype when the analysis was confined to those who had high-risk PCa. The results supported the protective role of -202 A/C SNP of the IGFBP3 gene against PCa in Korean men.

IGF-I and IGFBP-3 polymorphisms in relation to circulating levels among African American and Caucasian women.

Circulating insulin-like growth factor-I (IGF-I) and IGF-binding protein-3 (IGFBP-3) levels have been associated with common diseases. Although family-based studies suggest that genetic variation contributes to circulating IGF-I and IGFBP-3 levels, analyses of associations with multiple IGF-I and IGFBP-3 single nucleotide polymorphisms (SNP) have been limited, especially among African Americans. We evaluated 30 IGF-I and 15 IGFBP-3 SNPs and estimated diplotypes in association with plasma IGF-I and IGFBP-3 among 984 premenopausal African American and Caucasian women. In both races, IGFBP-3 rs2854746 (Ala32Gly) was positively associated with plasma IGFBP-3 (CC versus GG mean difference among Caucasians, 631 ng/mL; 95% confidence interval, 398-864; African Americans, 897 ng/mL; 95% confidence interval, 656-1,138), and IGFBP-3 diplotypes with the rs2854746 GG genotype had lower mean IGFBP-3 levels than reference diplotypes with the CG genotype, whereas IGFBP-3 diplotypes with the CC genotype had higher mean IGFBP-3 levels. IGFBP-3 rs2854744 (-202 A/C) was in strong linkage disequilibrium with rs2854746 in Caucasians only, but was associated with plasma IGFBP-3 in both races. Eight additional IGFBP-3 SNPs were associated with >or=5% differences in mean IGFBP-3 levels, with generally consistent associations between races. Twelve IGF-I SNPs were associated with >or=10% differences in mean IGF-I levels, but associations were generally discordant between races. Diplotype associations with plasma IGF-I did not parallel IGF-I SNP associations. Our study supports that common IGFBP-3 SNPs, especially rs2854746, influence plasma IGFBP-3 levels among African Americans and Caucasians but provides less evidence that IGF-I SNPs affect plasma IGF-I levels.

Plasma Insulin-Like Growth Factor-1 (IGF-1), IGF-Binding Protein-3, and the Risk of Prostate Cancer: A Matched Case-Control Study in a Korean Population

Purpose: Conflicting results have been reported for western populations on associations of serum insulin-like growth factor I (IGF-I) and major IGF-binding protein-3 (IGFBP-3) with the risk of prostate cancer. However, few data have been available for oriental populations. We undertook a matched case-control study in a low-risk Korean population to extend our knowledge about potential associations. Materials and Methods: Serum IGF-I and IGFBP-3 levels were determined for 330 men (165 cases and 165 healthy age-matched controls). Conditional logistic regression was used to estimate the odds ratio (OR) and 95% confidence interval (CI) for the association between plasma IGF levels and prostate cancer. We also investigated the potential influence of the associations according to clinical risk for advanced disease at diagnosis. Results: We noted that the risks of prostate cancer were unrelated to the IGF-1 level and IGF-I/IGFBP-3 molar ratio. In contrast, a strong inverse association was observed between IGFBP-3 levels and the risk for prostate cancer. Men in the highest quartile of IGFBP-3 levels had a 71% reduced risk of prostate cancer compared with men in the lowest quartile (OR= 0.29, 95% CI: 0.11-0.64, Ptrend<0.001). Subgroup analysis revealed a significant inverse association between plasma IGFBP-3 and the likelihood of a high risk prostate cancer. Conclusions: Plasma IGFBP-3 levels were inversely associated with the risk of prostate cancer and the likelihood for high-risk disease, suggesting that IGFBP-3 plays a protective role against prostate cancer in the Korean population. (Korean J Urol 2009;50:642-648) 󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏

Plasma Insulin-like Growth Factors, Insulin-like Binding Protein-3, and Outcome in Metastatic Colorectal Cancer: Results from Intergroup Trial N9741

Insulin-like growth factor (IGF)-I and IGF-II stimulate neoplastic cell growth and inhibit apoptosis, whereas IGF-binding protein-3 (IGFBP-3) inhibits the bioavailability of IGF-I and has independent proapoptotic activity. We examined the influence of baseline plasma levels of IGF-I, IGF-II, IGFBP-3, and C-peptide on outcome among patients receiving first-line chemotherapy for metastatic colorectal cancer. The plasma levels of IGF-I, IGF-II, IGFBP-3, and C-peptide as well as data on prognostic factors and body size were measured at baseline among 527 patients participating in a randomized trial of first-line chemotherapy for metastatic colorectal cancer. Higher baseline plasma IGFBP-3 levels were associated with a significantly greater chemotherapy response rate (P = 0.03) after adjusting for other prognostic factors, whereas neither IGF-I nor IGF-II levels significantly predicted tumor response. Higher levels of IGF-I, IGF-II, and IGFBP-3 were all univariately associated with improved overall survival (P = 0.0001 for all). In a model that mutually adjusted for IGF-I and IGFBP-3, as well as other prognostic factors, increasing baseline-circulating IGFBP-3 was associated with a significantly longer time to tumor progression (P = 0.03), whereas circulating IGF-I was not associated with disease progression (P = 0.95). Levels of C-peptide were not associated with any measure of patient outcome. Among colorectal cancer patients receiving first-line chemotherapy, increasing levels of IGFBP-3, an endogenous antagonist to IGF-I, are associated with an improved objective treatment response and a prolonged time to cancer progression. The IGF pathway may represent an important target for future treatment strategies.

Homozygous and heterozygous expression of a novel mutation of the acid-labile subunit

Acid-labile subunit (ALS) deficiency due to homozygous inactivation of the ALS gene (IGFALS) is associated with moderate short stature, and in few cases pubertal delay. The clinical expression of heterozygosity is unknown. To investigate the clinical, laboratory, and radiological features of homozygous and heterozygous carriers of a novel mutation in the ALS gene in comparison with non-carriers. Three short Kurdish brothers and their relatives. The index cases presented with short stature, microcephaly, and low circulating IGF-I and IGF-binding protein-3 (IGFBP-3), and undetectable ALS levels. Two were known with a low bone mineral density and one of them had suffered from two fractures. We found a novel homozygous ALS gene mutation resulting in a premature stop codon (c.1490dupT, p.Leu497PhefsX40). The IGF-I, IGFBP-3, and ALS 150 kDa ternary complex was absent, and ALS proteins in serum were not detected with western blot. IGFPB-1 and IGFPB-2 were low and there was a mild insulin resistance. Five heterozygous carriers tended to have a lower height and head circumference than five non-carriers, and had low plasma ALS and IGFBP-3 levels. Bone mineral (apparent) density was low in two out of three homozygous carriers, and also in four out of nine relatives. The clinical presentation of homozygous ALS mutations may, besides short stature, include microcephaly. Heterozygous carriers may have less statural and head growth, suggestive for a gene dosage effect.

Genetic Polymorphisms Involved in Insulin-like Growth Factor (IGF) Pathway in Relation to Mammographic Breast Density and IGF Levels

The insulin-like growth factor (IGF) pathway is believed to play a role in carcinogenesis of the mammary gland. Single nucleotide polymorphisms (SNPs) of IGF-I, IGF-binding protein-3 (IGFBP-3), IGF receptor 1, insulin receptor substrate 1, and phosphoinositide-3-kinase, catalytic, beta polypeptide genes, which are members of the IGF pathway, have been associated with risk of common cancers, breast density, and/or IGF levels but results remain inconclusive. Thus, we evaluated the association of 11 targeted IGF pathway SNPs with circulating IGF levels and mammographic breast density. Among 741 white premenopausal women, blood samples were collected at time of screening mammography, and plasma IGF-I and IGFBP-3 levels were measured by ELISA. Percent and absolute breast density were estimated using a computer-assisted method. Multivariate linear models were used to examine the associations. Women carrying increasing number of copies of the rare allele of IGF-I rs1520220 and rs6220 SNPs had increased percent breast density (P(trend) = 0.04 and 0.06, respectively). Carriers of increasing number of copies of the rare allele of phosphoinositide-3-kinase, catalytic, beta polypeptide rs361072 SNP had decreased percent (P(trend) = 0.04) and absolute (P(trend) = 0.02) breast density. An association of insulin receptor substrate 1 rs1801278 SNP with absolute density (P(trend) = 0.03) was also observed. All four IGFBP-3 SNPs (including rs2854744) were associated with IGF-I and IGFBP-3 levels. This study shows that several components of the IGF pathway are associated with breast density or IGF levels. Our findings provide additional support for the idea that several components of the IGF pathway may affect breast cancer risk and that this effect on breast cancer development may be mediated, at least in part, through its influence on the morphogenesis of breast tissue.

Development of Method for Estimating Diplotype Associations with Linear or Binomial Outcomes

We developed a simulation method to account for phase uncertainty in associations between outcomes and diplotypes imputed from genotypes. Participants were 582 black and 402 white premenopausal women (age 35–49 years) randomly selected from an urban health plan and enrolled in the NIEHS Uterine Fibroid Study. Thirty IGF-I (insulin-like growth factor-I) and 15 IGFBP-3 (IGF binding protein-3) single nucleotide polymorphisms (SNPs) were genotyped based on previous research, functional significance, or haplotype-tagging properties. Diplotypes were estimated using PHASE version 2.1, which reports posterior probabilities reflecting uncertainty of individual diplotype assignments. Our approach uses information on all possible diplotypes from women with data for at least 50% of the SNPs in each gene. Using SAS V9.1, we simulated the study population separately by race 100,000 times and 1) randomly assigned diplotypes to each woman according to her posterior probability of having each possible diplotype; 2) used linear regression to model associations between diplotypes and plasma IGF-I and IGFBP-3 levels; 3) used binary regression to estimate prevalence differences for uterine fibroids; and 4) drew a random variable from a normal distribution to simulate ordinary sampling error. Simulation results are summarized by the mean and the 2.5th and 97.5th percentiles of the simulated distributions. Preliminary results for IGFBP-3 confirm the feasibility of the method, which allowed us to retain about 10% of observations that ordinarily would be excluded because of low posterior probabilities. This approach uses complete diplotype information, reduces the number of excluded observations, and can be used to estimate associations with both binary and continuous outcomes. It can be applied to any exposure for which potential misclassification (probability of exposure) can be estimated for each individual.

Ethnic Disparity in the Relationship between Obesity and Plasma Insulin-Like Growth Factors: The Multiethnic Cohort

Previous studies on the relationship between obesity and circulating insulin-like growth factor (IGF) hormones show inconsistent findings and have not considered the possibility of racial/ethnic-specific differences that may exist. We therefore examined the relationship between obesity status [as measured by body mass index (BMI)] and plasma levels of the IGF proteins, IGF-I, IGF-binding protein 3 (IGFBP-3), and the molar ratio of IGF-I/IGFBP-3 in Whites, African Americans, Latinos, Japanese Americans, and Native Hawaiians from the ongoing Hawaii and Los Angeles Multiethnic Cohort Study. We measured plasma IGF-I and IGFBP-3 by ELISA in a random sample of 811 Multiethnic Cohort participants (53% male, age range = 47-82 at blood draw). In a multivariate regression of IGF-I levels, we found a statistically significant interaction between race/ethnicity and obesity status (P = 0.005). Plasma IGF-I levels declined with increasing BMI most dramatically in Latinos and Japanese. This decline was attenuated in Whites and absent in African-American and Native Hawaiian subjects. In Japanese, the quadratic term (BMI(2)) was statistically significant in a multivariate model (P = 0.002). In Latinos, the adjusted least-squares mean IGF-I levels in ng/mL for BMI < 25, 25 to 29.99, and >or=30 were 184.6, 147.7, and 132.7, respectively. No interaction between race/ethnicity and BMI explained the plasma IGFBP-3 levels in these data. These results may help to resolve the uncertainty in the relationship between circulating IGF levels and obesity and highlight the potential importance of racial/ethnic-specific effects among these factors in explaining ethnic disparities in obesity-related cancers.

Insulin Resistance, Apoptosis, and Colorectal Adenoma Risk

Compelling evidence from epidemiologic studies indicates that elevated circulating insulin-like growth factor (IGF)-I, insulin resistance, and associated complications, such as elevated fasting plasma insulin, glucose and free fatty acids, glucose intolerance, increased body mass index, and visceral adiposity, are linked with increased risk of colorectal cancer. However, the role of insulin and markers of glucose control in the development of adenomas, precursors to colorectal cancer, has not been fully explored. We evaluated the relationship between plasma insulin, glucose, IGF-I, IGF-II, IGF-binding protein-3 (IGFBP-3), apoptosis, and colorectal adenomas in a case-control study. Participants were drawn from consenting patients undergoing colonoscopy at the University of North Carolina hospitals (Chapel Hill, NC). Participants were classified as cases or controls based on whether they had one or more colorectal adenomatous polyps. Fasting plasma insulin, IGF-I, IGF-II, and IGFBP-3 levels were assessed by ELISA. Glucose was measured by glucose hexokinase assay. Apoptosis was assessed by morphology on H&E-stained sections. Dietary and lifestyle information were obtained by telephone interview. Logistic regression was used to examine the association between adenoma status and insulin-IGF markers. Adenoma cases (n = 239) and adenoma-free controls (n = 517) provided rectal biopsies and/or blood samples and interview data. Consistent with prior findings, cases were more likely to be males, older, have higher waist-to-hip ratio, lower calcium intake, lower apoptosis, and less likely to report nonsteroidal anti-inflammatory drug use. Those in the highest quartile of insulin (adjusted odds ratio, 2.2; 95% confidence interval, 1.1-4.2) and glucose (adjusted odds ratio, 1.8; 95% confidence interval, 0.9-3.6) were more likely to have an adenoma compared with the lowest quartile. Similarly, subjects in the highest two quartiles of insulin were more likely to be in the lowest two quartiles of apoptosis. Overall, there were no significant differences between mean circulating levels of glucose, IGF-I, IGF-II, and IGFBP-3 among cases and controls and no association between these variables and apoptosis. The results provide novel evidence that elevated insulin and glucose are associated with increased adenoma risk and decreased apoptosis in normal rectal mucosa. These findings suggest that insulin may act early in the adenoma-carcinoma sequence to promote the development of colorectal adenoma by decreasing apoptosis in the normal mucosa.

Insulin-like growth factor-I (IGF-I), IGF-binding protein-3 (IGFBP-3), and mammographic breast density

9501 Background: A few small studies have suggested that higher IGF-I and lower IGFBP-3 may be associated with increased premenopausal mammographic breast density, one of the strongest known breast cancer risk factors. This large cross-sectional study was designed specifically to evaluate the associations of IGF-I, IGFBP-3, and IGF-I/IGFBP-3 molar ratio with breast density. Methods: For this study, 784 premenopausal and 791 postmenopausal healthy women were recruited during screening mammography examinations. Using a computer-assisted method, a single observer assessed mammographic breast density with high reproducibility (intraclass correlation coefficient = 0.98). Blood samples collected at the time of the mammography allowed measurement of plasma IGF-I and IGFBP-3 levels by ELISA methods (coefficients of variation below 10% and 13%, respectively). Spearman's partial correlation coefficients (r) were used to evaluate the associations while adjusting for confounding factors including age, body mass index and IGF-I or IGFBP-3 when applicable. Results: Among premenopausal women, breast density is positively associated with IGF-I and IGF-I/IGFBP-3 ratio (r = 0.084, p = 0.019 and r = 0.070, p = 0.051, respectively) and negatively associated with IGFBP-3 (r = −0.123, p = 0.0005). No significant correlations were observed among postmenopausal women. Correlations among postmenopausal women (p-values) for IGF-I, IGFBP-3 and their ratio were 0.038 (0.282), −0.019 (0.593) and 0.035 (0.332), respectively. Conclusions: To date, this is the largest study of the relation of IGF to breast density. IGF-I and the IGF-I/IGFBP-3 ratio were correlated with mammographic breast density among premenopausal women supporting the view that the IGF axis plays a role in the development of some breast cancers among premenopausal women by its influence on breast density. No significant financial relationships to disclose.

Insulin-like growth factor-I (IGF-I), IGF-binding protein-3 (IGFBP-3), and mammographic breast density

9501 Background: A few small studies have suggested that higher IGF-I and lower IGFBP-3 may be associated with increased premenopausal mammographic breast density, one of the strongest known breast cancer risk factors. This large cross-sectional study was designed specifically to evaluate the associations of IGF-I, IGFBP-3, and IGF-I/IGFBP-3 molar ratio with breast density. Methods: For this study, 784 premenopausal and 791 postmenopausal healthy women were recruited during screening mammography examinations. Using a computer-assisted method, a single observer assessed mammographic breast density with high reproducibility (intraclass correlation coefficient = 0.98). Blood samples collected at the time of the mammography allowed measurement of plasma IGF-I and IGFBP-3 levels by ELISA methods (coefficients of variation below 10% and 13%, respectively). Spearman's partial correlation coefficients (r) were used to evaluate the associations while adjusting for confounding factors including age, body mass index and IGF-I or IGFBP-3 when applicable. Results: Among premenopausal women, breast density is positively associated with IGF-I and IGF-I/IGFBP-3 ratio (r = 0.084, p = 0.019 and r = 0.070, p = 0.051, respectively) and negatively associated with IGFBP-3 (r = −0.123, p = 0.0005). No significant correlations were observed among postmenopausal women. Correlations among postmenopausal women (p-values) for IGF-I, IGFBP-3 and their ratio were 0.038 (0.282), −0.019 (0.593) and 0.035 (0.332), respectively. Conclusions: To date, this is the largest study of the relation of IGF to breast density. IGF-I and the IGF-I/IGFBP-3 ratio were correlated with mammographic breast density among premenopausal women supporting the view that the IGF axis plays a role in the development of some breast cancers among premenopausal women by its influence on breast density. No significant financial relationships to disclose.

Pedigree-based quantitative genetic analysis of interindividual variation in circulating levels of IGFBP-3.

Circulating levels of insulin-like growth factor binding protein-3 (IGFBP-3) vary greatly between normal individuals, but until now little attention has been given to the study of the genetic factors involved in IGFBP-3 variability in healthy populations. The present study investigated the extent and pattern of the possible genetic influences on plasma levels of IGFBP-3 in 91 nuclear and more complex families, totaling 396 individuals (201 males and 195 females) of Caucasian ethnic origin. The variance decomposition analysis, was performed using the FISHER statistical package. In the second stage of the analysis, we used complex segregation analysis as implemented in the statistical package MAN. Significant negative correlation was revealed between age and plasma levels of IGFBP-3 in both sexes ( r=-0.49; r=-0.23; P<0.001). Multivariate analysis identified age, body weight, and height as significant covariates in men, but for women only age had a considerable effect. It has been demonstrated that about 57.7% of IGBP-3 variation adjusted for significant confounding factors was attributable to genetic factors. The results of bivariate variance decomposition analysis showed no significant genetic and phenotypic correlation between the mineral density of hand bones and IGFBP-3. Segregation analysis revealed the existence of a potential major gene effect that was able to explain some 27.5% of IGFBP-3 variation. Multifactorial effects, likely, unknown minor genes, contributed an additional 30% to IGFBP-3 variation. The segregation analysis also provided evidence of significant genotype X sex interaction in the determination of plasma levels of IGFBP-3.

Plasma levels of IGF-1, IGF-2, and IGFBP-3 in white and African-American men at increased risk of prostate cancer

Objectives. To further investigate the relationship between the plasma levels of insulin-like growth factor-1 (IGF-1), insulin-like growth factor-2 (IGF-2), insulin-like growth factor binding protein-3 (IGFBP-3), growth hormone, testosterone, and demographic factors, particularly race, within a group of men at increased risk of prostate cancer development. Methods. Enzyme-linked immunosorbent assays or an immunosorbent assay was used to quantitate the plasma levels of IGF-1, IGF-2, IGFBP-3, growth hormone, and testosterone. The study group consisted of 169 men (85 African-American, 84 white) aged 35 to 69 years, with no personal history of prostate cancer, but having at least one first-degree relative diagnosed with the disease, unless they were African-American. The relationships between the plasma levels and the categorical covariates were assessed using the nonparametric Wilcoxon test and between the continuous variables using Spearman’s correlation coefficient. Results. The mean plasma levels of IGFBP-3 were significantly lower in African-American (2657 ng/mL) than in white (2965 ng/mL) men ( P = 0.0062). The plasma levels of IGF-2 were also lower in the African-American (503.5 ng/mL) than in the white (549.1 ng/mL) men ( P = 0.0084). Overall, the IGF-1 plasma levels correlated positively with the IGF-2, IGFBP-3, and growth hormone levels and the IGF-2 plasma levels correlated negatively with the testosterone levels. Conclusions. Our results demonstrate that lower plasma levels of IGFBP-3 and IGF-2 are associated with race in a population of men at increased risk of developing prostate cancer. The ability of these markers to predict earlier disease onset is currently under investigation.

Racial differences in insulin-like growth factor binding protein-3 in men at increased risk of prostate cancer

Objectives. To determine the overall plasma levels of insulin-like growth factor-1 (IGF-1) and insulin-like growth factor binding protein-3 (IGFBP-3) in a group of men at higher risk of prostate cancer development and to investigate the relationships between demographics and these levels, particularly with regard to race. Methods. An enzyme-linked immunosorbant assay was used to quantitate plasma levels of IGF-1 and IGFBP-3. The study group consisted of 105 men (63 African American [AA], 42 white), aged 35 to 69 years, with no personal history of prostate cancer, but having at least one first-degree relative diagnosed with the disease, unless they were AA. Differences in plasma levels and categorical covariates were assessed using the nonparametric Wilcoxon test. Associations between plasma levels and the continuous variables were quantified using the nonparametric Spearman correlation coefficient. Results. The mean plasma level of IGF-1 was not significantly different between AA (162.3 ng/mL) and white (172.1 ng/mL) men ( P = 0.415). However, the mean plasma level of IGFBP-3 was lower in AA (2789 ng/mL) than in white (3216 ng/mL) men, and this decrease was highly significant ( P = 0.0045). No correlation between IGFBP-3 plasma level and age was detected in the group as a whole, but an inverse relationship between IGF-1 plasma level and age was evident ( P = 0.0079). Conclusions. Our results demonstrate that IGFBP-3 plasma levels are lower in AA men than in white men. Since IGFBP-3 can control IGF-1 bioavailability, the lowered IGFBP-3 could explain in part the increased risk of prostate cancer in AA men.

The relationship between endogenous insulin-like growth factors and growth in pigs.

Previous studies have reported conflicting data on gender differences in plasma IGF-I in postnatal pigs. There is also debate over the role of IGF-II in regulation of postnatal growth. We have, therefore, determined the concentrations of plasma IGF-I, IGF-II, and IGF-binding protein-3 (IGFBP-3) in boars, barrows, and gilts and related these to postnatal growth characteristics. Plasma concentrations of IGF-I were higher in boars than in gilts or barrows from 13 wk. of age, and plasma IGF-II levels were generally higher in barrows than in boars or gilts. Plasma IGFBP-3 levels were higher in boars than in gilts or barrows at most ages. Between 15 and 23 wk. of age, IGF-I and IGFBP-3, but not IGF-II, were positively associated with growth rate, voluntary feed intake, and gain:feed ratio. Plasma IGF-II, but not IGF-I or IGFBP-3, was positively associated with backfat depth during this period. These results support the hypothesis that circulating IGF-I and IGF-II are regulators of lean and adipose tissue growth, respectively.

Megakaryocytes endocytose insulin-like growth factor (IGF) I and IGF-binding protein-3: a novel mechanism directing them into alpha granules of platelets.

Lysis of platelets releases the contents of the alpha-granules, which contain growth factors, including insulin-like growth factor I (IGF-I) and IGF-binding protein-3 (IGFBP-3). We investigated the mechanism by which IGF-I and IGFBP-3 appeared in the alpha-granules with a goal of modulating their levels in platelets to affect platelet functions. Reverse transcription-PCR was initially used to test whether megakaryocytes contained IGFBP-3 and IGF-I messenger RNA transcripts. We found that megakaryocytes did not express the IGFBP-3 gene, but did have IGF-I messenger RNA. We subsequently investigated whether they incorporated IGFBP-3 and IGF-I by the process of endocytosis and packaged them into the alpha-granules. This hypothesis was tested in two ways. 1) We examined whether during pregnancy in the rat the alpha-granule content for IGFBP-3 paralleled the changes in plasma IGFBP-3 levels caused by the pregnancy-induced IGFBP-3 protease. The alpha-granule contents of both IGFBP-3 and IGF-I declined in parallel to the plasma changes in pregnant rats and returned to normal postpartum. As the binding protein protease acts extracellularly, endocytosis of the IGF-I:IGFBP-3 complex from the extracellular fluid by megakaryocytes was suggested. 2) We tested whether an IGF-I:IGFBP-3 complex comprised of human IGF-I and IGFBP-3 (recombinant 28.7 kDa) injected i.v. appeared in rat platelet alpha-granules. Hypophysectomized rats were injected i.v. with 5.24 mg of a 1:1 complex of IGF-I:IGFBP-3. After 24 h, platelet lysates were prepared and analyzed for IGFBP-3 by Western ligand blotting, and IGF-I was determined by RIA. Platelet lysates of the treated animals showed a prominent new band at approximately 28 kDa, whereas control rats were negative. In addition, the alpha-granule IGF-I concentration increased from 0.38 to 1.9 ng/1 x 10(9) platelets. These results indicate that the IGF-I:IGFBP-3 complex is taken up by megakaryocytes and packaged into the alpha-granules of platelets and demonstrate how the contents of IGF-I and IGFBP-3 in platelets can be modulated by their plasma concentrations. As reverse transcription-PCR has shown that the IGF-I, but not the IGFBP-3, gene is expressed by megakaryocytes, there may be two mechanisms for directing IGF-I into the alpha-granules of platelets.

Metabolic Effects of 12-Month Percutaneous Dehydroepiandrosterone Replacement Therapy in Postmenopausal Women

We have evaluated the effect of dehydroepiandrosterone (DHEA) replacement therapy in 60- to 70-year-old women (n = 15) who received a single daily percutaneous application of a 10% DHEA cream for 12 months. While anthropometric measurements showed no change in body weight, we observed a 9.8% decrease in subcutaneous skinfold thickness at 12 months (P < 0.05). This was confirmed by measurements of midthigh fat and muscle areas by computed tomography where a 3.8% decrease (P < 0.05) in femoral fat and a 3.5% increase (P < 0.05) in femoral muscular areas were observed at 12 months. There was no significant change in abdominal fat measurements but the waist-to-hip ratio was only 0.83 at the onset of treatment. These changes in body fat and muscular mass were associated with a 11% decrease (P < 0.05) in fasting plasma glucose and a 17% decrease (P < 0.05) in fasting insulin levels. Treatment with DHEA had no adverse effect on the lipid or lipoprotein profile. In fact, an overall trend towards a decrease in total cholesterol and its lipoprotein fractions was observed. Plasma triglycerides were not affected. Plasma high-density lipoprotein (HDL) cholesterol decreased by 8% but the ratio HDL/cholesterol was unchanged by DHEA treatment because of a parallel decrease in total cholesterol. The index of sebum secretion showed a 73% increase (P < 0.05) during the 12 months of DHEA therapy followed by a return to pretreatment values 3 months after cessation of therapy. At the same time, sex hormone-binding globulin levels decreased (P < 0.05) during treatment and returned to pretreatment values 3 months after the end of therapy. Serum gonadotropins were not changed by DHEA treatment. Although not significant, we observed a tendency towards an elevation in serum GH levels. Values of serum IGF-I remained unchanged while plasma IGF-binding protein-3 levels significantly decreased (P < 0.05) during treatment and returned to pretreatment values after cessation of DHEA therapy. The present data clearly indicate the beneficial effects of DHEA therapy in postmenopausal women through its transformation into androgens and/or estrogens in specific intracrine tissues without any significant side effects.

Metabolic effects of 12-month percutaneous dehydroepiandrosterone replacement therapy in postmenopausal women.

We have evaluated the effect of dehydroepiandrosterone (DHEA) replacement therapy in 60- to 70-year-old women (n = 15) who received a single daily percutaneous application of a 10% DHEA cream for 12 months. While anthropometric measurements showed no change in body weight, we observed a 9.8% decrease in subcutaneous skinfold thickness at 12 months (P < 0.05). This was confirmed by measurements of midthigh fat and muscle areas by computed tomography where a 3.8% decrease (P < 0.05) in femoral fat and a 3.5% increase (P < 0.05) in femoral muscular areas were observed at 12 months. There was no significant change in abdominal fat measurements but the waist-to-hip ratio was only 0.83 at the onset of treatment. These changes in body fat and muscular mass were associated with a 11% decrease (P < 0.05) in fasting plasma glucose and a 17% decrease (P < 0.05) in fasting insulin levels. Treatment with DHEA had no adverse effect on the lipid or lipoprotein profile. In fact, an overall trend towards a decrease in total cholesterol and its lipoprotein fractions was observed. Plasma triglycerides were not affected. Plasma high-density lipoprotein (HDL) cholesterol decreased by 8% but the ratio HDL/cholesterol was unchanged by DHEA treatment because of a parallel decrease in total cholesterol. The index of sebum secretion showed a 73% increase (P < 0.05) during the 12 months of DHEA therapy followed by a return to pretreatment values 3 months after cessation of therapy. At the same time, sex hormone-binding globulin levels decreased (P < 0.05) during treatment and returned to pretreatment values 3 months after the end of therapy. Serum gonadotropins were not changed by DHEA treatment. Although not significant, we observed a tendency towards an elevation in serum GH levels. Values of serum IGF-I remained unchanged while plasma IGF-binding protein-3 levels significantly decreased (P < 0.05) during treatment and returned to pretreatment values after cessation of DHEA therapy. The present data clearly indicate the beneficial effects of DHEA therapy in postmenopausal women through its transformation into androgens and/or estrogens in specific intracrine tissues without any significant side effects.