Reduced Serum Insulin-like Growth Factor-1 Research Articles

Antagonists of growth hormone-releasing hormone and somatostatin analog RC-160 inhibit the growth of the OV-1063 human epithelial ovarian cancer cell line xenografted into nude mice.

The effects of antagonists of GHRH and the somatostatin analog RC-160 on the growth of OV-1063 human epithelial ovarian cancer cells xenografted into nude mice were investigated. Treatment with 20 microg/day of the GHRH antagonist JV-1-36 or MZ-5-156 and 60 microg/day of the somatostatin analog RC-160 for 25 days decreased tumor volume by 70.9% (P < 0.01), 58.3% (P < 0.05), and 60.6% (P < 0.01), respectively, vs. the control value. The levels of GH in serum were decreased in all of the treated groups, but only RC-160 significantly reduced serum insulin-like growth factor I (IGF-I). The levels of messenger ribonucleic acid (mRNA) for IGF-I and -II and for their receptors in OV-1063 tumors were investigated by multiplex RT-PCR. No expression of mRNA for IGF-I was detected, but treatment with JV-1-136 caused a 51.8% decrease (P < 0.05) in the level of mRNA for IGF-II in tumors. Exposure of OV-1063 cells cultured in vitro to GHRH, IGF-I, or IGF-II significantly (P < 0.05) stimulated cell growth, but 10(-5) mol/L JV-1-36 nearly completely inhibited (P < 0.001) OV-1063 cell proliferation. OV-1063 tumors expressed mRNA for GHRH receptors and showed the presence of binding sites for GHRH. Our results indicate that antagonistic analogs of GHRH and the somatostatin analog RC-160 inhibit the growth of epithelial ovarian cancers. The effects of RC-160 seem to be exerted more on the pituitary GH-hepatic IGF-I axis, whereas GHRH antagonists appear to reduce IGF-II production and interfere with the autocrine regulatory pathway. The antitumorigenic action of GHRH antagonists appears to be mediated by GHRH receptors found in OV-1063 tumors.

Mapping quantitative trait loci for serum insulin-like growth factor-1 levels in mice

Serum insulin-like growth factor-1 (IGF-1) and femoral bone mineral density (BMD) differ between two inbred strains of mice, C3H/HeJ (C3H) and C57BL/6J (B6), by approximately 30% and 50%, respectively. Similarly, skeletal IGF-1 content, bone formation, mineral apposition, and marrow stromal cell numbers are higher in C3H than in B6 mice. Because IGF-1 and several bone parameters cosegregate, we hypothesize that the serum IGF-1 phenotype has a strong heritable component and that genetic determinants for serum IGF-1 are involved in the regulation of bone mass. We intercrossed (B6 × C3H)F1 hybrids and analyzed 682 F2 female offspring at 4 months of age for serum IGF-1 by radioimmunoassay and femoral BMD by peripheral quantitative computerized tomography (pQCT). Genomic DNA was assayed by polymerase chain reaction (PCR) to determine alleles for 114 Mit markers inherited in F2 mice at average distances of 14 centimorgans (cM) along each chromosome (Chr). Serum IGF-1 levels in the F2 progeny were relatively normal in distribution, but showed a greater range than either progenitor, indicating that serum IGF-1 level is a polygenic trait with an estimated heritability of 52%. Serum IGF-1 correlated with femoral length ( r = 0.266, p < 0.0001) and femoral BMD ( r = 0.267, p < 0.0001). Whole genome scans for main effects associated with serum IGF-1 levels revealed three significant QTLs (in order of significance) on mouse Chrs 6, 15, and 10. The QTL on Chr 6 showed a significant reduction in IGF-1 associated with increasing C3H allele number, whereas the Chr 15 and Chr 10 loci showed additive effects with increasing C3H allele number. A genome-wide search for interacting marker pairs identified a significant interaction between the Chr 6 QTL and a locus on Chr 11. This interactive effect suggested that when the Chr 11 locus was homozygous for C3H, there was no effect of the Chr 6 locus on serum IGF-1; however, the combination of C3H alleles on Chr 6 with B6 alleles on Chr 11 was associated with reduced serum IGF-1 concentrations. To test this in vivo, we tested congenic mice carrying the Chr 6 QTL region from C3H on a B6 background (B6.C3H-6). Both serum IGF-1 and femoral BMD were significantly lower in female congenic than progenitor B6 mice. In summary, we identified three major QTLs on mouse Chrs 6, 10, and 15, and noted a major locus-locus interaction between Chrs 6 and 11. We named these QTLs IGF-1 serum levels ( Igf1sl1 to Igf1sl4). Functional isolation of the Igf1sl1 QTL on Chr 6 for IGF-1 in B6.C3H-6 congenic mice demonstrated effects on both the IGF-1 and BMD phenotypes. The genetic determinants of these Igf1sl QTLs will provide much insight into the regulation of IGF-1 and the subsequent acquisition of peak bone mass.

Alendronate administration and skeletal response during chronic alcohol intake in the adolescent male rat.

Alendronate is an aminobisphosphonate that inhibits bone resorption in osteoporotic humans and rats but does not induce osteomalacia. Several bisphosphonates, including alendronate, also have direct positive actions on osteoblasts, bone formation, and mineralization. We studied the effects of alendronate on skeletal development in adolescent male rats during chronic alcohol intake. Four groups of age- and weight-matched male Sprague-Dawley rats (35 days of age) were fed the Lieber-DeCarli diet containing 36% of calories as EtOH (E), the EtOH diet plus 60 mg/kg alendronate (EA) every other day intraperitoneally (ip), an isocaloric diet (I), or the isocaloric diet plus 60 mg/kg alendronate (IA) every other day ip. Body weight, femur length, serum levels of osteocalcin (OC), insulin-like growth factor 1 (IGF-1), testosterone, and luteinizing hormone (LH); femur distal metaphyseal and middiaphyseal bone mineral density (BMD) and tibial metaphyseal gene expression for alpha-1-type I collagen (Col I), OC, and bone alkaline phosphatase (AP); and femur strength by four-point bending to failure were measured after 28 days of feeding and alendronate injections. Serum alcohol levels at death were 156 +/- 13 mg/dl (E) and 203 +/- 40 mg/dl (EA). Alendronate given to alcohol-fed rats increased metaphyseal BMD by more than 3-fold over rats fed alcohol alone. Alendronate given to isocaloric pair-fed rats increased metaphyseal BMD by more than 2.5-fold over rats fed the isocaloric diet alone. Cortical BMD was reduced by alcohol but was increased by alendronate. Alcohol consumption reduced serum IGF-1 levels, and alendronate increased IGF-1 levels in alcohol-fed rats. Serum OC, testosterone, and LH were unaffected by alcohol and alendronate. Quantitative dot blot hybridization using rat complementary DNA (cDNA) probes and normalization against 18S subunit ribosomal RNA (rRNA) levels revealed no changes in tibial metaphyseal gene expression for type I collagen, osteocalcin, or alkaline phosphatase. Alcohol significantly reduced the biomechanical properties of the femurs that were partially compensated by alendronate. Chronic alcohol consumption uncouples formation from ongoing resorption, and resorption is inhibited by alendronate. However, alendronate's positive effects on osteoblast-mediated mineralization during chronic alcohol consumption point to the potential use of bisphosphonates in the treatment of decreased bone formation secondary to alcohol-induced diminished osteoblast function.

Reduced Serum Insulin-Like Growth Factor (IGF) and IGF-Binding Protein-3 Concentrations in Two Deerhounds with Congenital Portosystemic Shunts

Reduced Serum Insulin-Like Growth Factor (IGF) and IGF-Binding Protein-3 Concentrations in Two Deerhounds with Congenital Portosystemic Shunts

A dose-finding study of lanreotide (a somatostatin analog) in patients with colorectal carcinoma.

Laboratory data suggest that insulin-like growth factor-1 (IGF-1) may stimulate the growth of different human tumors. At least in acromegalic patients, somatostatin (SMS) analogs, such as lanreotide, suppress the serum levels of growth hormone (GH) and IGF-1. To evaluate the tolerability and biologic activity of different doses of lanreotide in patients with advanced colorectal carcinoma, consecutive groups of 3 patients each were subcutaneous treated with lanreotide at doses of 1, 2, 3, 4, 5, or 6 mg three times a day for 2 months. In the event of Grade 3 side effects, 3 additional patients were treated with the same dose before the next dose escalation. Serum samples were obtained on Days 0, 15, 30, and 60 for serum GH, IGF-1, and lanreotide assessment. Twenty-four patients were enrolled and all were evaluable. Except for the 3 and 6 mg doses, for which the observation of a Grade 3 side effect required that an additional three patients be treated, it was sufficient to treat 3 patients at each dose. The overall incidence of side effects was as follows: changes in bowel habits, 83%; abdominal cramps, 79%; diarrhea, 17%; vomiting, 17%; nausea, 21%; steatorrhea, 78%; hyperglycemia, 35%; laboratory hypothyroidism, 39%; gallstones, 13%; and weight loss, 17%. No evidence of an increase in the incidence, intensity, or duration of side effects was observed with dose escalation. Serum IGF-1 levels were as follows: Day 15: 63%, 60%, and 67% of the baseline values for the low (1-2 mg), intermediate (3-4 mg), and high (5-6 mg) dose groups, respectively; Day 30: 63%, 59%, and 51%, respectively; and Day 60: 73%, 69%, and 47%, respectively. Serum lanreotide levels declined during treatment in all of the dose groups (90 ng/mL on Day 15, and 35 ng/mL on Day 60 for the 5-6 mg group; 10 ng/mL on Day 15, and 1.5 ng/mL on Day 60 for the 1-2 mg group). No antitumor activity or tumor marker reduction was observed. No increase in toxicity was observed when subcutaneous lanreotide doses were escalated to 6 mg three times a day for 2 months. The highest doses seemed to maintain reduced serum IGF-1 levels; with the lowest doses, a "rebound" in serum IGF-1 levels was observed during treatment. Nevertheless, intermittent subcutaneous injections do not ensure constant serum drug concentrations over time.

Suppression of the hypothalamus-pituitary somatotrope axis in men with spinal cord injuries

Thirty-two men with spinal cord injury (SCI) were studied for evaluation of the hypothalamus-pituitary somatotrope axis, using growth hormone-(GH)-releasing hormone (GHRH) and insulin-induced hypoglycemia. Twenty-six age-matched normal male volunteers served as controls. Six SCI subjects (18.7%) had elevated basal follicle-stimulating hormone (FSH) levels, eight (25.0%) had hyperprolactinemia, and 11 (34.4%) had reduced serum insulin-like growth factor-1 (IGF-1) levels. Twenty SCI subjects (62.5%) had reduced and/or delayed GH responses to GHRH, and eight (25.8%) had reduced GH response to insulin-induced hypoglycemia. Seven of eight hyperprolactinemic SCI subjects showed reduced GH response to GHRH and/or insulin-induced hypoglycemia. These findings are consistent with the notion that SCI subjects have a reduced central dopaminergic tone.

Validation of a Heterologous Radioimmunoassay for Insulin-Like Growth Factor-1 in Chicken Serum.

Chicken serum insulin-like growth factor-1 (IGF-1) was extracted with an acid ethanol solution and submitted to a heterologous radioimmunoassay (RIA) after lyophilization. In the RIA, recombinant human IGF-1 (rhIGF-1) was used for standards and radioactive ligand. Anti-rhIGF-1 antiserum used was provided by the NIDDK. The inhibition curves for extracts of two-fold serial dilutions of chicken sera were essentially parallel to those for the standard and human sera. The recovery of rhIGF-1 added to chicken sera was 100.1±0.7% (n=30). The intrrassay and interassay variability (CV) for the RIA was 6.9% (n=10) and 7.6% (n=3), respectively. The limit of sensitivity for measurement of IGF-1 extracted from chicken serum was 5 pg/assay tube. Hypophysectomy significantly reduced serum levels of IGF-1 by 80% as compared to sham-operated control chicken. Dwarfing gene (dw) also significantly reduced serum IGF-1 by 89% compared to normal control. These results indicate that the present heterologous RIA was validated for measurement of immunoreactive IGF-1 levels in chicken serum.

Effects of growth hormone on growth and muscle Na(+)-K+ pump concentration in K(+)-deficient rats.

K(+)-deficient rats and control rats were injected for 16 days with saline or human growth hormone (hGH, 200 micrograms/day). hGH treatment of K(+)-deficient rats resulted in increased weight gain and soleus muscle weight. Extensor digitorum longus (EDL) muscle weight and tail and tibia length were unchanged. In control rats, hGH induced an increase in all weight and length parameters. K+ deficiency was associated with reduced serum insulin-like growth factor I (IGF-I) and serum insulin but unchanged total 3,5,3'-triiodothyronine (TT3) and total thyroxine. hGH treatment of the K(+)-deficient rats restored serum IGF-I, but not serum insulin, and decreased TT3. In saline-treated K(+)-deficient rats [3H]ouabain binding site concentration decreased by 44 and 39% in soleus and EDL muscle, respectively, as compared with the saline-treated controls. hGH had no effect on the [3H]ouabain binding site concentration in the K(+)-deficient group, but, in control rats, increases of 11 and 8% were observed in soleus and EDL muscle, respectively. When the increase in muscle weight was taken into account, this amounted to relative increases of 24 and 30%, respectively. Low circulating GH and IGF-I levels are not the sole explanation for the growth retardation in K+ deficiency. GH/IGF-I stimulate the synthesis of Na(+)-K+ pumps in rats with an otherwise normal hormonal status.

Serum insulin-like growth factor I levels in adult diabetic patients: the effect of age.

Despite reports of reduced serum insulin-like growth factor (IGF) levels in experimentally diabetic animals, human diabetic patients have been reported to have decreased, normal, or even elevated levels. This study was a cross-sectional examination of the effect of age on immunoreactive IGF-I levels in adult patients with insulin-dependent or noninsulin-dependent diabetes mellitus (IDDM and NIDDM) attending a diabetes out-patient clinic. The patients and normal subjects studied were divided into the age ranges 21-30, 31-40, 41-50, 51-60, and over 60 yr. For all ages combined, the mean IGF-I level (+/- SD) was 0.84 +/- 0.26 U/ml (202 +/- 62 ng/ml) in 133 normal subjects, significantly reduced to 0.41 +/- 0.17 U/ml in 121 IDDM patients, and 0.49 +/- 0.19 U/ml in 46 NIDDM patients (both P less than 0.001). In both groups there was a marked decline in IGF-I with increasing age (P less than 0.01). Except for NIDDM patients aged 21-30 yr (only two patients), IGF-I levels in both IDDM and NIDDM patients were significantly lower in every age range than those in age-matched normal subjects, but did not differ between the two diabetic groups. Glycosylated hemoglobin levels correlated inversely with IGF-I levels only in younger patients with IDDM (r = -0.486; P less than 0.05 for patients aged 21-40 yr). We conclude that factors common to IDDM and NIDDM, perhaps related to relative nutritional deficiency at the cellular level, cause a reduction in serum IGF-I levels, and that this reduction occurs independently of age-related changes in IGF-I.