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During pregnancy, changes in the IGF axis are associated with changes in maternal metabolism and nutrient repartitioning which are necessary to meet the demands of a growing conceptus. The aim of this study was to assess the IGF axis, maternal weight changes and food intake in female New Zealand White rabbits (n = 7) prior to breeding (day 0) and serially throughout pregnancy until term (day 30-31). The total weight of the pregnant does progressively increased from 4.03 +/- 0.06 kg (mean +/- S.E.M.) on day 0 to 4.47 +/- 0.07 kg on day 30 (P < 0.001). Maternal tissue mass (total weight minus estimated conceptus weight) increased until day 18, plateaued to day 22/23, and then significantly declined. On day 30, the maternal tissue mass was not significantly different from the non-pregnant value, such that the final increase in total weight was due to conceptus growth. Although the does were fed ad libitum, food intake did not change until day 29 when it decreased to approximately 50% of previous intake (P < 0.01). Maternal serum IGF-I was 499 +/- 32 ng/ml on day 0, reached a peak of 832 +/- 160 ng/ml on day 21 (P < 0.02), and then declined to 341 +/- 49 ng/ml on day 30. In contrast, serum IGF-II increased dramatically from a non-pregnant level of 85 +/- 14 ng/ml to 16,295 +/- 2488 ng/ml on day 23 (P < 0.001), and then rapidly declined (3335 +/- 954 ng/ml, day 30). Changes in serum IGF-binding proteins (IGFBPs) followed a pattern similar to IGF-II, as assessed by Western-ligand blotting. All IGFBPs, especially the 45-40 kDa IGFBP-3 doublet, increased dramatically between days 12 and 24 of pregnancy, and then declined towards term. In conclusion, we observed unique and dramatic changes in the maternal serum IGF axis that corresponded to periods of maternal weight gain and loss. The tissue source of IGFs and IGFBPs remains undetermined, although it is of note that the time when major changes in the IGF axis were first observed coincided with the time of functional change from yolk sac to placenta in the rabbit.

The insulin-like growth factors (IGFs) and IGF-binding proteins (IGFBPs) in human synovial fluid play an important role in maintaining articular cartilage metabolism. In this study we measured the concentrations of IGF-I, IGF-II, and IGFBP-3 in normal human synovial fluid by RIA and characterized the IGFBPs by Western ligand blot (WLB), Western immunoblot, and immunoprecipitation. We also extended the study and compared normal synovial fluid to synovial fluids from patients with osteoarthritis (OA) and rheumatoid arthritis (RA). The concentrations of IGF-I, IGF-II, and IGFBP-3 in normal synovial fluid were 19 +/- 3 (mean +/- SE), 194 +/- 14, and 349 +/- 65 ng/mL, respectively. In synovial fluid of patients with OA, IGF-I levels were elevated, whereas IGF-II was decreased, and the IGFBP-3 level was similar to the control value. In patients with RA, both IGF-I and IGFBP-3 were elevated, whereas IGF-II remained unchanged. WLB and immunoprecipitation of normal synovial fluid revealed IGFBP-1 (26-29 kDa), IGFBP-2 (32 kDa), IGFBP-3 (42- to 39-kDa doublet), and IGFBP-4 (24 kDa); the IGFBP-3 doublet was very faint. In RA synovial fluid, all IGFBPs were dramatically increased, whereas little change was seen in the synovial fluid of OA. Western immunoblot against IGFBP-3 revealed a prominent 30-kDa immunoreactive fragment of IGFBP-3 in synovial fluids of normal adults as well as in those of RA and OA patients. This was concurrent with detectable IGFBP-3 protease activity, which was characterized to be of the metallo- and serine protease family. Thus, in normal synovial fluid, there is a balance of circulating IGF, IGFBP, and proteases to modulate the bioactivity of IGF. In pathological states, the increased IGF-I concentrations were accompanied by an increase in IGFBP-I concentrations were accompanied by an increase in IGFBP-3 levels in synovial fluid. These findings suggest that alteration of the IGF and IGFBP axis in pathological states may be important for understanding the underlying pathophysiology of disordered articular growth and metabolism.

The insulin-like growth factors (IGFs) are key effectors of fetal growth and development which are modulated by serum carrier proteins (IGF binding proteins [IGFBPs]). Studies were performed to evaluate the developmental profile of IGFs and IGFBPs in the macaque, an important nonhuman primate model for human development and disease. IGF-I, IGF-II, and IGFBP-3 were studied in the rhesus (Macaca mulatta) and long-tailed (Macaca fascicularis) monkey fetus and dam during the second and third trimesters of pregnancy. Serial fetal blood samples were collected by cardiocentesis every 10 days from gestational day (GD) 90-160, and at 1 month postnatal age; maternal blood samples were collected at similar timepoints. Results indicated that maternal sera IGF-I and IGF-II did not change significantly whereas fetal concentrations of serum IGF-I and IGF-II increased approximately two-fold during the second to the third trimesters. No significant differences were detected between the two species. Western-ligand blot analysis revealed predominant IGFBPs of 45-40 (IGFBP-3) and 28 kDa (IGFBP-1) in both the maternal and fetal compartments, and Western-immunoblot analysis using a specific antisera against IGFBP-3 indicated 45-40 and 28 kDa immunoreactive forms. Thus, although IGF-I, IGF-II, and IGFBP-3 remained relatively unaffected in maternal sera during this period of gestation, fetal concentrations of IGF-I, IGF-II, and IGFBP-3 increased in a developmental profile similar to the human fetus.

The molecular distribution of insulin-like growth factor I (IGF-I) and IGF-II among the IGF binding proteins (IGFBPs) was studied before and during IGF-I therapy in Ecuadorean adults with growth hormone receptor deficiency (GHRD). Of the total circulating IGF-I and IGF-II, 70% was carried by the 150 kDa complex in normal subjects, while in patients with GHRD, 50% of serum IGF-I, but only 30-35% of serum IGF-II, was measured within the 150 kDa IGFBP-3 region. Administration of IGF-I altered the concentration of IGF-I and IGF-II, although the percentage of total IGF measured within each IGFBP region was not affected, as the increase in IGF-I and the decrease in IGF-II were proportional. Similarly, serum concentrations of IGFBP-3 and the acid-labile subunit, measured by radioimmunoassay, were unaltered. Thus, administration of IGF-I to patients with GHRD was unable to correct the aberrant distribution of IGFs among the IGFBPs.

We have previously reported that adult GH receptor-deficient (GHRD) patients treated subcutaneously with recombinant human insulin-like growth factor (IGF)-I have increased serum IGF-I levels and decreased IGF-II levels, whereas IGF-binding protein-3 (IGFBP-3) levels were unchanged. To further investigate the effects of IGF-I administration upon the IGF-IGFBP axis in GHRD, we have examined: 1) the molecular distribution of IGF-I and IGF-II among the IGFBPs; 2) the composition and distribution of the IGFBPs, in particular IGFBP-3; and 3) the acid labile subunit (ALS). Serum samples from adult GHRD patients who were treated sc with recombinant human IGF-I (40 micrograms/kg, sc, twice a day) or from normal Ecuadorian adults were incubated with [125I]IGF-II and subjected to neutral size-exclusion chromatography. The fractions were then subjected to Western ligand blot, Western immunoblot, IGFBP-3 RIA, and IGF RIAs. Serum of healthy adults incorporated [125I]IGF-II into the 150- and 44-kilodalton (kDa) IGFBP region. The 150-kDa IGFBP region contained most of the circulating IGFBP-3, whereas the 44-kDa IGFBP region contained mainly IGFBP-1, 2, and 4. The 150-kDa region also contained a unique 28-kDa immunoreactive form of IGFBP-3, which was not detectable by Western ligand blot. Endogenous IGF-I and IGF-II were distributed equally in the 150- and 44-kDa IGFBP regions. Sera from GHRD patients mainly incorporated [125I]IGF-II into the 44-kDa IGFBP region. Similar to control sera, the 150-kDa IGFBP region contained IGFBP-3, albeit at lower concentrations. The 44-kDa IGFBP region contained all IGFBPs including 50% of the total immunoreactive IGFBP-3. The two immunoreactive forms of IGFBP 3 (40- to 45-kDa doublet and 28-kDa band) were present in both IGFBP regions. The IGF size-distribution study revealed that the 150-kDa IGFBP region carried half of the circulating endogenous IGF-I, but only 30% of the IGF-II. Concentrations of the ALS were consistently low. Administration of IGF-I to GHRD patients was unable to increase concentrations of the molecular forms of IGFBP-3, correct the aberrant distribution of IGFs among the IGFBPs, or increase serum concentrations of ALS. In conclusion, we have found two forms of IGFBP-3 associated with IGF and ALS, which are capable of forming the ternary 150-kDa complex in healthy adult serum. The ratio of these two forms of IGFBP-3 and their distribution in serum was different between GHRD and control patients.(ABSTRACT TRUNCATED AT 400 WORDS)

Recent studies in our laboratories have shown that urine from healthy adults contains immunoreactive and intact insulin-like growth factor-binding protein-3 (IGFBP-3). The aim of this study was to assess urinary IGF-I, IGF-II, and IGFBP-3 in a cross-sectional study of healthy subjects, as well as characterize urinary IGFBPs (uIGFBps) in patients with GH deficiency (GHD) and renal disease, such as, Alport syndrome, immunoglobulin A nephropathy, focal segmental glomerulosclerosis, and systemic lupus erythematosus. Urinary concentrations of IGF-I and IGF-II in pooled spot morning urines of healthy subjects, measured by RIA, were low and relatively unaltered throughout age, when expressed as either nanograms per milliliter or nanograms per milligram creatinine. To determine the complement of IGFBPs in urine of healthy subjects, spot morning urine samples were subjected to Western ligand blot and immunoblot analysis. IGFBP-3 was detected at 40-50 kDa, possibly due to variable glycosylation of uIGFBP-3. In addition, a 32-kDa IGFBP-2 and smaller unclassified IGFBPs were detected. Unlike uIGFs, urinary concentrations of IGFBP-3 (uIGFBP-3; nanograms per milligram creatinine) were age-, but not sex-related. Levels of uIGFBP-3 ranged from 40-60 ng/mL in children between 4 and 10 yr of age. After 11 yr, immunoreactive uIGFBP-3 progressively declined, attaining a plateau after 26 yr of age to approximately 18 ng/mg creatinine. uIGFBP-3 did not correlate with uIGF levels. Regulation of IGFBP-3 in the urine of normal subjects and of renal disorders was examined by RIA, Western ligand blot (WLB), and protease assay. Intact uIGFBP-3 was consistently found in normal urine and little urinary protease was identified. In GHD patients, IGFBP-3 by WLB was low or undetectable, whereas RIA levels of uIGFBP-3 were normal or high, consistent with the presence of IGFBP-3 proteolytic activity. In Alport syndrome, both RIA measures and WLB analysis were high, as was the IGFBP-3 proteolytic activity. Patients with immunoglobulin A nephropathy, focal segmental glomerulosclerosis and systemic lupus erythematosus measured low-normal levels of IGFBP-3 by WLB and RIA, and displayed little protease activity. This study provides normative data concerning radioimmunoassayable levels of IGFBP-3 in urine. The presence of normal-elevated levels of uIGFBP-3 by RIA in GHD indicates that uIGFBP-3 levels are not under GH control and are unlikely to represent filtered serum IGFBP-3.(ABSTRACT TRUNCATED AT 400 WORDS)

Six adult patients with growth hormone receptor deficiency (GHRD) (2 men, 4 women) with an identical defect in the growth hormone receptor (GHR) gene, were treated with recombinant human insulin-like growth factor I (IGF-I), 40 micrograms/kg s.c. twice daily, for 7 days. Serum concentrations of IGF peptide and IGF binding protein-3 (IGFBP-3) were measured by specific radioimmunoassays; serum IGFBPs were also measured by Western ligand blotting. The size distribution of both IGF-I and IGF-II was measured in serum following size-exclusion fast-performance liquid chromatography. IGF-I treatment resulted in a normalization of serum IGF-I levels on days 1-7 of treatment and a decrease in serum IGF-II levels. The fall in IGF-II levels and the simultaneous rise in IGF-I levels, however, resulted in an unchanged total serum IGF level. The low IGFBP-3 values did not significantly change during treatment, whereas there was a slight increase in IGFBP-2 levels. Preliminary analysis of size-fractionated sera suggested an increase in IGF-I levels in the 40 and 150 kDa regions at the expense of IGF-II levels. The results suggest that despite the failure of IGF-I treatment to increase IGFBPs significantly, serum IGFBP concentrations were sufficient to maintain normal levels of IGF-I.

The aim of this study was to assess the molecular size distribution of insulin-like growth factors (IGFs) complexed to IGF-binding proteins (IGFBPs) in serum of non-pregnant and pregnant women. Sera were fractionated on a size-exclusion column at pH 7.4 to resolve different IGF-IGFBP complexes from unbound IGFs. Each fraction was further chromatographed on a size-exclusion column under acid conditions to dissociate IGFs from binding proteins prior to measurement of the IGF content of the complexes. The IGF-containing fractions from the acid column were assayed specifically for IGF-I and IGF-II. Serum pooled from pregnant women contained more IGF-I and IGF-II than serum from non-pregnant women. In both groups most of the IGF-I and IGF-II was found in a large (150 kDa) complex in serum and the remainder was present in complexes eluting in the 40-50 kDa region at pH 7.4. Some free IGF-I was also detected. Serum fractions collected by size-exclusion chromatography at pH 7.4 were also analysed by Western-ligand blotting to characterize the IGFBPs in the two main IGFBP size classes. In serum pooled from non-pregnant women, the 150 kDa IGF-IGFBP complexes contained a 40-50 kDa IGFBP doublet following Western-ligand blot analysis. This IGFBP co-migrated with a pure IGFBP-3 standard. IGFBPs of 34, 28 and 24 kDa all contributed to the 40-50 kDa IGF-IGFBP complexes of the pH 7.4 chromatograph.(ABSTRACT TRUNCATED AT 250 WORDS)

Insulin-like growth factors (IGF) and binding proteins were measured in serum from pregnant and nonpregnant women. IGF-I determined by immunoassay after acid-ethanol extraction was increased by pregnancy (p less than 0.005) and was highest in the third trimester (p less than 0.01). Size exclusion chromatography of serum in acid before assay (i) gave a very similar IGF-I pattern, (ii) showed that IGF-II was much higher than IGF-I and (iii) revealed less serum IGF-binding protein activity in pregnancy and lactation. All IGF-binding proteins except binding protein-1 were markedly reduced by pregnancy. This indicates a major change in the main carrier protein for IGFs in the circulation and suggests that tissue targetting of IGFs may be altered during pregnancy.