Free Insulin-like Growth Factor Research Articles

Follicular fluid concentrations of free insulin-like growth factor (IGF)-I during follicular development in mares

The objective of the present study was to evaluate changes in concentrations of free insulin-like growth factor (IGF)-I in follicular fluid (FFL) during follicle development in the mare. Mares ( n = 14) were classified as either in the follicular phase ( n = 8) or luteal phase ( n = 6). Follicles ( n = 92) were categorized as small (6–15 mm; n = 54), medium (16–25 mm; n = 23) or large (>25 mm; n = 15) and FFL was collected. Free IGF-I levels in FFL in large follicles of follicular phase mares were greater ( P < 0.05) than in large follicles of luteal phase mares and small or medium follicles of luteal and follicular phase mares. Free IGF-I concentrations were greater ( P < 0.05) in large follicles of luteal phase mares than small but not medium follicles of luteal phase mares. FFL ratio of estradiol:progesterone paralleled changes in free IGF-I. Free IGF-I concentrations were negatively correlated ( P < 0.05) with insulin-like growth factor binding protein (IGFBP)-2, -4 and -5 but not IGFBP-3 levels. In addition, free IGF-I concentrations in FFL were positively correlated ( P < 0.01) with FFL estradiol, progesterone, androstenedione, estradiol:progesterone ratio, total IGF-I and total IGF-II. We conclude that increases in intrafollicular levels of bioavailable (free) IGF-I are associated with increased steroidogenesis in developing mare follicles.

No Effect of Exercise on Insulin-Like Growth Factor 1 and Insulin-Like Growth Factor Binding Protein 3 in Postmenopausal Women: a 12-Month Randomized Clinical Trial

A meta-analysis indicated that increased circulating concentrations of insulin-like growth factor 1 (IGF-1) are associated with increased risks for colorectal, prostate, and premenopausal breast cancers, and that increased concentrations of IGF binding protein 3 (IGFBP-3) are associated with

The serum levels of proinsulin and their relationship with IGFBP‐1 in obese children

Serum proinsulin (PI) levels were investigated in obese children to determine whether PI is a sensitive indicator of insulin resistance, as previously shown in adults with type 2 diabetes mellitus (DM), and to evaluate their relationship with insulin-like growth factor-binding protein-1 (IGFBP-1) known as a predictor of the development of cardiovascular disease in diabetic adults. Forty-two obese children without DM (age, 12.1 +/- 1.5 year) and 42 age-matched control children were included in the study. The serum levels of PI, immunoreactive insulin (IRI), IGFBP-1 and free insulin-like growth factor-1 (IGF-1) were measured in the fasting state. The fasting levels of serum PI and IRI were significantly higher in obese children than in controls (PI, 10.5 +/- 6.8 vs. 5.6 +/- 2.0 pmol/l, p < 0.001; IRI, 72.0 +/- 41.8 vs. 32.7 +/- 19.5 pmol/l, p < 0.001). Serum IGFBP-1 levels were significantly lower in obese children than in controls (37.7 +/- 24.6 vs. 76.3 +/- 26.5 microg/l, p < 0.001). The ratio of PI to IRI (calculated as molar ratios) did not differ significantly between obese and control subjects (0.16 +/- 0.08 vs. 0.19 +/- 0.11, p = 0.08). For the whole group, serum PI levels correlated positively with IRI and inversely with IGFBP-1 (IRI, r = 0.67, p < 0.001; IGFBP-1, r = -0.49, p < 0.001). Serum IGFBP-1 levels correlated inversely with both BMI and IRI (BMI, r = -0.73, p < 0.001; IRI, r = -0.60, p < 0.001). Multiple regression analysis revealed that the best predictive parameters for IGFBP-1 were BMI and PI (R2 = 0.57, p < 0.001 and p < 0.05, respectively). These findings suggest that fasting serum PI levels may be a better predictor than fasting insulin levels for the future development of type 2 DM and cardiovascular disease in obese children, and PI, in addition to insulin, contributes to the suppression of hepatic IGFBP-1 production.

Expression and alteration of insulin-like growth factor II-messenger RNA in hepatoma tissues and peripheral blood of patients with hepatocellular carcinoma

To investigate the clinical values of serum free insulin-like growth factor II (IGF-II) levels and IGF-II mRNA in hepatocellular carcinoma (HCC) tissues and peripheral blood for diagnosis of HCC and monitoring of extrahepatic metastasis. Total RNAs were extracted from HCC tissues or peripheral blood mononuclear cells from patients with HCC, liver diseases devoid of cancer, non-hepatic tumors, and healthy controls, respectively. IGF-II cDNAs were synthesized through random primers and reverse-transcriptase, amplified by polymerase chain reaction (PCR), and confirmed by DNA sequencing analysis. Serum free IGF-II levels in patients with different liver diseases were analyzed by an enzyme-linked immunosorbent assay. The amplified fragments of IGF-II mRNA by RT-PCR were identical to originally designed ones with a size of 170 bp and confirmed by sequencing analysis. The dilution experiments revealed that the lowest sensitivity of our system was 2 ng/L of total RNA. The positive frequencies of IGF-II mRNA were 100% in HCC tissues, 53.3% in para-cancerous tissues, and 0% in non-cancerous tissues, respectively. The serum free IGF-II levels were significantly higher in HCC than those in chronic hepatitis or liver cirrhosis. The positive frequency of circulating IGF-II mRNA was 34.2% in HCC, no amplified fragment was found in other liver diseases, extrahepatic tumors, and normal controls, respectively. The circulating IGF-II mRNA correlated with the stage of HCC, and its positive rate was 100% in HCC with extrahepatic metastasis and 35.5% in HCC with AFP-negative. No significant correlation was found between tumor sizes and circulating IGF-II mRNA fragment. The abnormal expressions of free IGF-II and IGF-II mRNA are useful tumor markers for HCC diagnosis, differentiation of extrahepatic metastasis and monitoring postoperative recurrence.

Free IGF-I, IGFBP-1, and the Binary Complex of IGFBP-1 and IGF-I Are Increased during Human Pregnancy

Background/Aims: To investigate changes in free insulin-like growth factor I (IGF-I) and IGF-binding protein 1 (IGFBP-1) complexed IGF-I during human pregnancy. Methods: Overnight fasting serum was obtained in a longitudinal design from 11 women with non-complicated pregnancy at gestation weeks 6–10, 16–20, 24–28 and 35–38 and, for comparison, 5 weeks post-partum. All samples were analyzed for total and free IGF-I and IGF-II, IGFBP-3 and IGFBP-3 proteolysis, total and non-phosphorylated (np-) IGFBP-1, and IGFBP-1 complexed IGF-I. Results: Total IGF-I was increased in late pregnancy (week 35–38) (p < 0.001), whereas free IGF-I was significantly increased by 77% already at week 6–10 (p = 0.004) and by 140% (p = 0.002) at week 34–38, when compared to post-partum levels. At weeks 16–20 and 24–28, levels of free IGF-I were not significantly different from post-partum levels. Significant IGFBP-3 proteolysis was detectable from week 6–10 and throughout pregnancy (p < 0.05). Total and np-IGFBP-1 were significantly increased from 16–20 weeks of pregnancy (both p < 0.05) and IGFBP-1 complexed IGF-I was increased 2-fold from week 16–20 and throughout pregnancy (p < 0.05). However, the saturation of IGFBP-1 remained constant at 27–29% during the study. Conclusion: We found evidence of increased free IGF-I and increased IGF-I in binary complexes during pregnancy, possibly caused by IGFBP-3 proteolysis and decreased ternary complex formation.

A polymorphism in type I deiodinase is associated with circulating free insulin-like growth factor I levels and body composition in humans.

The interaction between the GH-IGF-I axis and thyroid hormone metabolism is complex and not fully understood. T(4) stimulates IGF-I activity in animals in the absence of GH. On the other hand, GH replacement therapy results in an increase in serum T(3) and a decrease in T(4) and rT(3) levels, suggesting a stimulation of type I deiodinase (D1) activity. Recently, we demonstrated the association of two polymorphisms in D1 (D1a-C/T; T = 34%, and D1b-A/G; G = 10%) with serum iodothyronine levels. Haplotype alleles were constructed, suggesting a lower activity of the D1 haplotype 2 allele (aT-bA) and a higher activity of the haplotype allele 3 (aC-bG). In this study, we investigated whether genetic variations in D1 are associated with the IGF-I system. In 156 blood donors and 350 elderly men, the association of the D1 haplotype alleles with circulating IGF-I and free IGF-I levels was studied. In addition, potential associations with muscle strength and body composition were investigated in the elderly population. Finally, the relation between serum iodothyronine levels and IGF-I levels was studied. In blood donors, haplotype allele 2 was associated with higher levels of free IGF-I (302.9 +/- 22.9 vs. 376.3 +/- 19.1 pg/ml, P = 0.02). In elderly men, haplotype allele 2 also showed an allele dose increase in free IGF-I levels (P(trend) = 0.01) and an allele dose decrease in serum T(3) levels (P(trend) = 0.01), independent of age. Carriers of the D1a-T variant also had a higher isometric grip strength (P = 0.047) and maximum leg extensor strength (P = 0.07) as well as a higher lean body mass (P = 0.03). In blood donors, T(4) and free T(4) were negatively correlated with total IGF-I levels (R = -0.18, P = 0.03 and R = -0.24, P = 0.003), whereas T(3) to T(4) and T(3) to reverse T(3) ratios were positively correlated with total IGF-I (R = 0.31, P < 0.001 and R = 0.18, P = 0.03). Free IGF-I showed a negative correlation with T(4) (R = -0.26, P = 0.001) and T(4)-binding globulin (R = -0.31, P < 0.001) and a positive correlation with T(3) to T(4) ratio (R = 0.21, P = 0.01). In conclusion, a polymorphism that results in a decreased D1 activity is associated with an increase in free IGF-I levels. The pathophysiological significance of this association with IGF-I is supported by an increased muscle strength and muscle mass in carriers of the D1 haplotype 2 allele in a population of elderly men. The association of D1 haplotype allele 2 with serum T(3) levels in the elderly population suggests a relative increase in its contribution to circulating T(3) in old age.

Maternal plasma concentrations of insulinlike growth factor-1 and insulinlike growth factor-binding protein-1 in early pregnancy and subsequent risk of preeclampsia

Abstract Objectives: We investigated the relationship between maternal plasma free insulinlike growth factor-1 (IGF-1) and insulinlike growth factor-binding protein-1 (IGFBP-1) concentrations and risk of preeclampsia. Design and methods: Maternal blood samples were collected at 13 weeks' gestation on average. From the cohort, we selected 53 women who developed preeclampsia and 477 who remained normotensive. Free IGF-1 and IGFBP-1 concentrations were measured using immunoassays. Logistic regression procedures were used to calculate odds ratios (OR) and 95% confidence intervals (95% CI). Results: Women who developed preeclampsia had 18% and 27% lower concentrations of free IGF-1 and IGFBP-1, respectively, than controls ( P < 0.05). There was a 57% reduced risk of preeclampsia among women with free IGF-1 concentrations of ≥ 0.81 ng/mL (OR = 0.43, 95% CI 0.23–0.83) and a 43% reduced risk among women with IGFBP-1 concentrations of ≥ 72.36 ng/mL (OR = 0.53, 95% CI 0.23–1.21). Conclusions: Alterations of free IGF-1 and IGFBP-1 concentrations in maternal plasma during early pregnancy are associated with risk of preeclampsia. These associations may help to further elucidate the pathologic processes of preeclampsia.

Circulating free insulin-like growth factor (IGF)-I, total IGF-I, and IGF binding protein-3 levels do not predict the future risk to develop prostate cancer: results of a case-control study involving 201 patients within a population-based screening with a 4-year interval.

Recent studies have reported that serum IGF-I levels in the highest quartile of the normal range and IGF binding protein-3 (IGFBP-3) in the lowest quartile of the normal range are associated with an increased risk of future prostate cancer and/or presence of prostate cancer. It has also been suggested that the measurement of circulating total IGF-I concentrations might be a useful tool for the early detection of prostate cancer in men with moderately increased prostate-specific antigen (PSA) levels. To determine whether circulating free IGF-I, total IGF-I, and IGFBP-3 levels can predict future prostate cancer risk, we prospectively studied prostate cancer characteristics in a cohort of men during two rounds (mean interval, 4 yr) of a population-based screening study for prostate cancer. Two hundred one prostate cancer cases were detected at the second-round screening (aged 55-70 yr), and all these subjects were enrolled in the case group for the present study. Prostate cancer had been confirmed by biopsy in all cases. These 201 subjects were matched with the 201 nonprostate cancer cases by age, serum PSA range at the first-round screening (PSA < 2 ng/ml, n = 67; PSA = 2-3 ng/ml, n = 67; and PSA = 3-4 ng/ml, n = 67), and residence area. At baseline, total IGF-I, free IGF-I, and IGFBP-3 levels and prostate volume of cases with prostate cancer were not different from those of healthy controls. PSA velocity was significantly different between cases and controls (P < 0.001).Stepwise forward logistic regression analysis showed that only PSA levels at baseline and PSA at round 2 after 4 yr are good predictors of prostate cancer, whereas total IGF-I, free IGF-I, and IGFBP-3 did not predict the development of prostate cancer. Only one of the 201 subjects with prostate cancer had metastases. Within the subjects with prostate cancer, there were no differences of IGF-I parameters with different tumor node metastasis categories and/or Gleason scores. Our study suggests that the measurement of serum IGF-I and/or IGFBP-3 concentrations in addition to PSA does not improve the identification of men at high risk to develop early stages of prostate cancer. In addition, our results indicate that the endocrine IGF-I system is not directly involved in the growth of the early stages of prostate cancer.

Insulin-like growth factor (IGF)-I and IGF-II serum concentrations in patients with benign and malignant breast lesions: free IGF-II is correlated with breast cancer size.

Insulin-like growth factors (IGFs) are potent mitogens for breast cancer cells in vitro, and elevated IGF-I serum levels are a risk factor for breast malignancies. This study evaluated IGF-I and IGF-II serum levels in healthy women and in patients with benign and malignant breast lesions and correlated them with tumor size. Serum levels of the total and unbound fractions of IGF-I and IGF-II were analyzed in 65 patients with benign and malignant breast lesions and in 38 women without breast disease. ELISAs were used to detect serum IGF levels, with (total IGF) or without (free IGF) prior acid-ethanol extraction. Total IGF-I serum concentrations were lower in healthy women than in breast cancer patients (P < 0.001) or patients with benign breast lesions (P = 0.010), but no differences were observed in free IGF-I levels. Conversely, healthy women had higher serum levels of free IGF-II than women with breast lesions (P = 0.003), and the free/total IGF-II ratio was significantly reduced in patients with breast disease (P = 0.001). Although IGF-I or IGF-II serum concentrations of breast cancer patients were similar to those of patients with benign lesions, the size of a malignant tumor was correlated to the ratio free/total IGF-II (P = 0.002). Malignant breast tumors cannot be distinguished from benign breast lesions by systemic IGF serum levels. However, women with breast lesions have decreased IGF-II concentrations, and free IGF-II levels are clearly correlated to the size of a breast cancer, indicating an involvement in tumor growth.

Growth impairment of primary chondrocyte cells by serum of rats with chronic renal failure.

Insulin-like growth factor (IGF)/IGF binding protein (IGFBP) abnormalities may be important in the pathogenesis of growth failure in chronic renal failure (CRF). We induced experimental CRF by 5/6 nephrectomy in Sprague Dawley rats (100 g) and observed for 2 weeks comparing with sham-operated pair-fed control rats (Sham- C). CRF rats gained 30% less height than Sham- C rats (P < 0.01). Serum IGFBP profiles by Western ligand blot revealed that IGFBP4 was elevated two fold in CRF rats (P < 0.01 vs. Sham-C). However, IGFBP4 mRNA levels in liver or skeletal muscle were not different in two groups. To determine if the increase of serum IGFBP4 in CRF retarded the growth of cartilage, epiphyseal chondrocytes were isolated from CRF or control rats and cultured in the presence of control or CRF rat sera. Incubation with 10% CRF serum reduced proliferations of normal chondrocytes and L6 rat skeletal muscle cells. In contrast, 10% CRF serum did not inhibit the growth of CRF chondrocytes. Rat sera from two groups were separated into two different fractions, high (>10 kDa, containing IGFBPs) and low (<10 kDa, containing free IGF) molecular weight fractions using a gel filtration column. Both fractions obtained from CRF sera decreased the growth of control chondrocytes up to 40% compared with those from control sera. We suggest that the pathogenesis of growth failure in CRF may be involved in the increase of circulating IGFBP4 as well as the unidentified small molecular weight uremic serum factors which block the growth of chondrocytes in growth plate.

Long-term low-dose dehydroepiandrosterone replacement therapy in aging males with partial androgen deficiency

Dehydroepiandrosterone (DHEA) and dehydroepiandrosterone sulfate (DHEAS) age-related withdrawal is very likely to be involved in the aging process and the onset of age-related diseases, giving rise to the question of whether preventing or compensating the decline of these steroids may have endocrine and clinical benefits. The aim of the present trial was to evaluate the endocrine, neuroendocrine and clinical consequences of a long-term (1 year), low-dose (25 mg/day) replacement therapy in a group of aging men who presented the clinical characteristics of partial androgen deficiency (PADAM). Circulating DHEA, DHEAS, androstenedione, total testosterone and free testosterone, dihydrotestosterone (DHT), progesterone, 17-hydroxyprogesterone, allopregnanolone, estrone, estradiol, sex hormone binding globulin (SHBG), cortisol, follicle stimulating hormone (FSH), luteinizing hormone (LH), growth hormone (GH) and insulin-like growth factor 1 (IGF-1) levels were evaluated monthly to assess the endocrine effects of the therapy, while β-endorphin values were used as a marker of the neuroendocrine effects. A Kupperman questionnaire was performed to evaluate the subjective symptoms before and after treatment.The results showed a great modification of the endocrine profile; with the exception of cortisol levels, which remained unchanged, DHEA, DHEAS, androstenedione, total and free testosterone, DHT, progesterone, 17-hydroxyprogesterone, estrone, estradiol, GH, IGF-1 and β-endorphin levels increased significantly with respect to baseline values, while FSH, LH and SHBG levels showed a significant decrease. The Kupperman score indicated a progressive improvement in mood, fatigue and joint pain.In conclusion, the present study demonstrates that 25 mg/day of DHEA is able to cause significant changes in the hormonal profile and clinical symptoms and can counteract the age-related decline of endocrine and neuroendocrine functions. Restoring DHEA levels to young adult values seems to benefit the age-related decline in physiological functions but, however promising, placebo-controlled trials are required to confirm these preliminary results.

Aberrant blood flow area and plasma gonadotropin concentrations during the development of dominant-sized transitional anovulatory follicles in mares.

Color Doppler transrectal ultrasound was used to evaluate blood flow area in the wall of dominant anovulatory follicles versus ovulatory follicles in mares during the transition between anovulatory and ovulatory seasons. Daily examinations were done in 11 control mares toward the end of the anovulatory season. In 13 separate mares, follicular fluid was collected from 30-mm follicles, and blood flow areas from control mares were used as a basis for designating the sampled follicle as either anovulatory or ovulatory. Blood flow area in the controls ranged from 0.18 to 0.35 cm(2) in six mares on the day of a 30-mm anovulatory follicle and from 0.25 to 0.86 cm(2) in 11 mares on the day of a 30-mm ovulatory follicle; the ranges did not overlap except for one follicle. In the controls, mean blood flow area was lower (P < 0.05) in the anovulatory group than in the ovulatory group for each day beginning with the first Doppler examination at 25 mm. For plasma LH in controls, an effect of follicle group (P < 0.0001) and an interaction (P < 0.0001) of group by day reflected lower (P < 0.05) concentrations in the anovulatory group on Days -6, -2, and 5-8 (Day 0 = 30-mm follicle). For plasma FSH, an interaction (P < 0.0001) reflected higher (P < 0.05) concentrations in the anovulatory group on Days -3 and 1-4. More (P < 0.05) statistically identified FSH surges occurred in the anovulatory group during Days -7 to 8. In the sampled mares, follicular-fluid concentrations of estradiol, free insulin-like growth factor-1, inhibin-A, and vascular endothelial growth factor were lower (P < 0.05) in 30-mm designated anovulatory follicles than in 30-mm designated ovulatory follicles. Results were interpreted as follows: 1) The future anovulatory dominant-sized follicle developed under an LH deficiency, 2) the LH deficiency led to reductions in blood flow area and in concentrations of follicular-fluid factors, and 3) the reduction in follicle production of FSH suppressors resulted in higher plasma FSH concentrations.

Height, predictors of C-peptide and cancer risk in men.

Excessive energy intake tends to increase circulating levels of insulin and free insulin-like growth factor-1 (IGF-I), which may increase risk of some cancers that are common in Western countries. However, the relative importance of these hormonal factors during pre-adulthood and adulthood is unknown. We prospectively examined height, as a marker of pre-adult IGF-I bioactivity, and modifiable adult determinants of insulin secretion, in relation to risk of cancer, particularly Western-related cancers (colon, pancreas, kidney, and aggressive prostate cancers) in 47,690 male health professionals. Information about dietary and lifestyle factors for these men was collected at baseline (1986) and was updated periodically. A C-peptide score, representing insulin secretion, was created by using body mass, physical activity, and diet in a stepwise linear regression to predict C-peptide level, in a sample of 263 cohort members. From 1986 to 1998, we documented 3270 incident cancers (excluding the less aggressive prostate cancers). Greater body mass index, lower physical activity, and a Western dietary pattern were independent predictors of higher plasma C-peptide levels in the sample. A C-peptide score, based on these variables, was positively related to risk of Western-related cancers, but not to other cancer types in the entire cohort. Height was also only related to Western-related cancers. For Western-related cancers, 29% (95% CI: 16%, 48%) were attributed to C-peptide scores above the first decile, 30% (95% CI: 11%, 58%) to heights >or=66 inches, and 49% (95% CI: 30%, 69%) to both factors combined. For total cancers, 29% (95% CI: 16%, 46%) were attributable to both factors. Maximal growth in the pre-adult period and hyperinsulinaemia during adulthood may largely underlie the excess risk of some cancers that are common in Western populations. A substantial proportion of these cancers may be modifiable in adulthood, through alterations in body weight, sedentary behaviour, and dietary patterns that stimulate hyperinsulinaemia.

Free insulin-like growth factor (IGF) in disorders of IGF binding protein 3 complex formation.

The concentration of free IGF-I and -II in normal human serum is less than 0.5% of the total concentration of the IGF (1). Despite the fact that this component is critical in the feedback regulation of pituitary GH secretion and is important in the endocrine action of IGF-I on target tissues, its measurement has been little used in clinical practice. This is because the small concentrations of this entity are technically difficult to measure accurately and concentrations are subject to rapid change, depending on the fluctuations of the concentration of IGF binding protein 1 (IGFBP1) in fasting and metabolic disorders such as diabetes mellitus. For this reason, measurement of total serum IGF-I has been the accepted clinical method of evaluating IGF-I activity in patients. About 80% of what is being measured is IGF-I that is bound to the ternary complexes of IGF-I-IGFBP3-acid labile subunit (ALS) (2) and to a lesser extent to the ternary complex of IGF-IGFBP5-ALS. The remainder is in loose binary association with IGFBP1, -2, and -4. Measurement of serum IGFBP3 as an index of GH action, therefore, is a surrogate measure of the total IGF-I and IGF-II in serum. However, in conditions when the formation of the IGFBP3 ternary complex is impaired, total serum IGF no longer reflects free IGF. Two different examples by which this might occur are considered.

Serum Levels of Free Insulin-Like Growth Factor (IGF)-I in Normal Children.

Serum levels of free insulin-like growth factor (IGF)-I were measured by immunoradiometric assay (IRMA) in fasting sera of 137 normal boys and 120 normal girls aged from 8 to 15 yr to study relationships between free IGF-I levels and ages, total IGF-I, IGF binding protein (IGFBP)-1, IGFBP-3, and acid-labile subunit (ALS) levels. In both sexes, serum free IGF-I levels and the ratios of free IGF-I to total IGF-I were significantly higher in the pubertal age groups than in the prepubertal age groups. Serum levels of free IGF-I showed a significant positive correlation with those of total IGF-I, IGFBP-3 and ALS, while they showed a significant negative correlation with those of IGFBP-1. These observations suggest that increase in serum free IGF-I levels during puberty is caused by a dramatic increase in total IGF-I, rather than IGFBP-3, and a decrease in IGFBP-1. Also, high free IGF-I levels may play an important role in pubertal growth spurt.

In vivo effects of an intrafollicular injection of insulin-like growth factor 1 on the mechanism of follicle deviation in heifers and mares.

In cattle and mares, free insulin-like growth factor 1 (IGF-1) is higher in the future dominant follicle (F1) than in the future largest subordinate follicle (F2) before deviation in diameter or selection is manifested between the two follicles. The effect of IGF-1 on other follicular-fluid factors and on the destiny of F2 were studied in two experiments in each species, using a total of 40 heifers and 42 mares. An injection of IGF-1 was made into F2 at the expected beginning of deviation (heifers, F1 >or= 8.5 mm; mares, F1 >or= 20.0 mm; Hour 0). In heifers, follicular fluid was taken from F2 at Hours 3, 6, 12, or 24; each heifer was sampled only once. In mares, sequential F2 samples were taken from each mare at Hours 0, 6, and 24 or at Hours 12 and 24. Transvaginal ultrasound guidance was used for treatment and sample collection. In heifers, IGF-1 treatment of F2 stimulated the secretion of estradiol (P < 0.05) between Hours 3 and 6 and androstenedione (P < 0.05) between Hours 3 and 12. In F2 of control heifers, estradiol decreased (P < 0.05) and androstenedione did not change significantly. In mares, IGF-1 treatment of F2 did not affect the concentrations of estradiol during the 24-h posttreatment period; androstenedione decreased (P < 0.04) in the IGF-1 group and increased (P < 0.006) in the controls. Compared with control mares, the IGF-1 group had higher (P < 0.04) activin-A at Hours 12 and 24 and higher (P < 0.0006) inhibin-A at Hour 24. After ablating F1 at Hour 24 in mares, F2 became dominant and ovulated in more mares (P < 0.0002) in the IGF-1 group (12/14) than in the control group (2/14). These results are consistent with reported temporal relationships among follicular factors during deviation in both species and indicate that IGF-1 plays a key role in controlling the temporal relationships; however, no indication was found that IGF-1 stimulated estradiol production in mares during the 24 h after treatment.

Effects of GRF in early gestation on foetal development in Large White and Genex-Meishan gilts

The effects of growth hormone-releasing factor (GRF), given in early gestation, on reproductive traits, foetal development and pre-weaning growth of piglets from two breeds were studied. Large White (LW, n = 26) and Genex-Meishan (GM, containing 50% Meishan genes, n = 37) pregnant gilts were divided in two groups: (1) saline injections (n = 33) and, (2) injections of 6.66 µg kg-1 of a GRF analogue (n = 30), given thrice daily from days 18 to 33 of gestation. Jugular blood samples were collected on days 17, 34 and 109 of gestation and were assayed for various hormones and metabolites. Thirty-six gilts were slaughtered on day 110 of gestation and uterine, foetal and placental measurements were obtained. The other 27 gilts farrowed. There was a day × treatment interaction (P &lt; 0.001) for glucose, insulin, free fatty acids (FFA) and insulin-like growth factor I (IGF-I), with values being greater on day 34 in gilts receiving GRF. The increase in insulin concentration was greater in LW- than in GM-treated gilts (P = 0.02). Exogenous GRF increased foetal weight in LW litters only (1.13 ± 0.04 vs. 1.05 ± 0.03 kg; P = 0.04) whereas fat content of carcasses tended to be lower only in foetuses of treated GM gilts (5.3 ± 0.2 vs. 5.8 ± 0.2%; P = 0.1). Weight of the longissimus muscle and its fibre number were not influenced by GRF. Furthermore, growth of piglets to 28 d was not affected by GRF treatment (P &gt; 0.1). In conclusion, GRF given in early gestation seems to have different effects in LW and GM litters, yet it does not alter pre-weaning growth rate. Key words: Molybdenum, molybdenosis, copper, mine tailings, reclamation, animal health

Increase of free insulin-like growth factor-1 in normal human breast in vivo late in the menstrual cycle.

Prolonged exposure to endogenous and exogenous sex steroids increases the risk of breast cancer but the mechanisms are poorly understood. Increased levels of circulating insulin-like growth factor-1 (IGF-1) and low levels of IGF binding protein are associated with increased risk of breast cancer suggesting that IGF-1 has to be in its free form to be biologically active. Little is known about sex steroid regulation of IGF-1 locally in the breast. In this study microdialysis was used to determine the local levels of free IGF-1 in normal human breast tissue in healthy female volunteers during the menstrual cycle. The results showed that the extracellular levels of free IGF-1 locally in the breast were doubled in the luteal phase, when estradiol and progesterone levels were elevated, compared with the follicular phase. In plasma, free IGF-1 levels also exhibited a cyclic variation but to a less extent. The increased local levels of the free form of IGF-1 may promote proliferation in the breast epithelium. This could be important in sex steroid dependent breast cancer development.

Elevated insulin, proinsulin and insulin-like growth factor-binding protein-1 in liver disease

Insulin-like growth factor-binding protein-1 (IGFBP-1) is one of six soluble binding proteins that regulate the actions of the insulin-like growth factors (IGFs). Liver is the major source of IGFBP-1 in non-pregnant humans. In normal physiology, IGFBP-1 transcription is potently inhibited by insulin and serum levels are limited by a rapid clearance rate. Elevated levels of IGFBP-1 in liver disease have been attributed to insulin resistance; however, the relationships between these analytes have not been defined. We studied insulin, proinsulin and IGFBP-1 in normal subjects (NL, N=47, 43+/-12 yr), cirrhosis (CIR, N=29, 54+/-14 yr), hepatocellular carcinoma (HCC, N=42, 61+/-11 yr), and other liver tumors (TUM, N=8, 60+/-17 yr). All three analytes were significantly increased in liver disease (mean+/-SEM; p-values relative to normals): IGFBP-1 (NL 24+/-4 ng/ml; CIR 235+/-53, p<0.0001; HCC 505+/-105, p<0.0001; TUM 118+/-36, p<0.0001), insulin (NL 72+/-4 pM; CIR 261+/-62, p<0.0002; HCC 180+/-25, p<0.0001; TUM 189+/-58, p<0.0001), proinsulin (NL 6.5+/-0.7 pM; CIR 36.8+/-7.7, p<0.0001; HCC 26.2+/-3.8, p<0.0001; TUM 32.1+/-9.7, p<0.0001). The ratio of proinsulin to insulin was also significantly elevated in liver disease. A typical curvilinear inverse relationship of insulin and IGFBP-1 was observed, but was shifted several fold higher for the liver disease groups. Our results demonstrate that insulin and proinsulin are elevated in liver disease. However, these elevations are paradoxically accompanied by elevated IGFBP-1 levels, indicating disruption of normal regulatory mechanisms. IGFBP-1 is postulated to play a dynamic role in metabolic substrate utilization via regulation of free IGF. Therefore, inappropriate elevation of IGFBP-1 could play an important role in the metabolic disturbances associated with liver disease.

The relationship between the circulating IGF system and the presence of retinopathy in Type 1 diabetic patients.

Patients with proliferative diabetic retinopathy (PDR) have increased vitreous levels of insulin-like growth factor (IGF)-I, IGF-II and IGF binding proteins (IGFBPs). This accumulation is probably caused by increased leakiness of the blood-retina barrier and influx of circulating IGFs and IGFBPs. To date, interest has focused on the role of circulating total IGF-I in the development of PDR, and there are only sparse data on circulating levels of free IGF-I and IGFBPs. We compared fasting serum samples from matched groups of Type 1 diabetic patients with no retinopathy (n = 29), non-PDR (n = 13) and PDR (n = 16). We also included matched controls (n = 26). Serum was analysed for free and total IGF-I and -II, free plus dissociable IGF-I, IGFBP-1, -2 and -3, IGFBP-1-bound IGF-I as well as IGFBP-3 proteolysis. When compared with controls, diabetic patients (n = 58) showed reduced (P < 0.0005) levels of free and total IGFs, free plus dissociable IGF-I and IGFBP-3, whereas levels of IGFBP-1, IGFBP-1-bound IGF-I and IGFBP-2 were elevated. IGFBP-3 proteolysis remained unaltered. When comparing diabetic patients with different degrees of retinopathy, IGFBP-2 and IGFBP-1-bound IGF-I were the only parameters that differed significantly. Patients with retinopathy (non-PDR as well as PDR) had elevated IGFBP-2 (P < 0.03) and reduced IGFBP-1-bound IGF-I (P < 0.03), when compared with patients without retinopathy. Noteworthy, both parameters correlated (0.11 < r2 < 0.14, P < 0.02) with the severity of retinopathy. Our study gives no evidence of a direct role of circulating free IGF-I in the development of PDR, whereas IGFBP-2 and IGFBP-1-bound IGF-I showed a relationship with the degree of retinopathy. However, further investigations are needed in order to clarify the basis and clinical relevance of this finding.