Regulation of the acid-labile subunit of the insulin-like growth factor ternary complex in patients with insulin-dependent diabetes mellitus and severe burns

OBJECTIVE Little information is available regarding the regulation of serum acid-labile subunit (ALS) in human disease. We have studied alterations in serum ALS of the insulin-like growth factor (IGF) ternary complex in children with untreated insulin-dependent diabetes mellitus (IDDM) and subjects with severe burns before and after insulin therapy. In addition, we have investigated the effect of insulin plus GH on serum ALS in burn patients. DESIGN Serum samples were obtained from children with newly diagnosed and untreated IDDM before the initiation of insulin therapy and 1 month thereafter. Serum samples were also obtained from adult patients with severe burns who were on a continuous infusion of a carbohydrate-rich enteral diet via nasogastric and duodenal catheters under basal conditions, after a 1-week period of continuous insulin infusion, and after an additional week of insulin plus recombinant GH. PATIENTS Twenty children and adolescents with untreated IDDM, aged 1.2–16 years, and 6 young adult patients with severe burns aged 17–28 years were studied longitudinally. Control sera were obtained from age, sex and pubertal status matched subjects (for children with IDDM) and from fed healthy adults. MEASUREMENTS Serum insulin, GH, cortisol and IGF-I were measured by radioimmunoassay, and serum ALS levels were assessed by Western immunoblot before and after treatment periods. RESULTS Serum ALS levels were lower in untreated children with IDDM (69 ± 6% of control children). Insulin therapy significantly increased serum ALS (79 ± 5%, P<0.05) in these children. Patients with severe burns also had lower serum ALS levels (79 ± 10% of control adults). After one week of insulin therapy serum ALS levels increased to 90 ± 15% of control values (P<0.05). Addition of GH to insulin therapy for another week did not significantly further increase serum ALS levels (95 ± 27%). Serum IGF-I concentrations increased nearly 2.5-fold in diabetic subjects and fourfold in burn subjects at the end of the study periods. There were no proteolytic fragments of ALS in the sera studied. The deglycosylation pattern of ALS did not differ between diabetic and control sera. CONCLUSION Serum ALS levels were diminished in children with untreated IDDM and were partially restored after the initiation of insulin therapy. Serum ALS levels were also diminished in patients with severe burn injury and restored by insulin treatment. Addition of GH to insulin therapy did not significantly increase serum ALS levels over levels obtained during insulin therapy alone. These decreases in serum ALS were smaller than the decrease in serum IGF-I concentrations in both conditions, suggesting that IGF-I is the limiting factor for the ternary complex formation in the catabolic states. Insulin may regulate circulating ALS levels in catabolic states and helps to restore the IGF system.     

Serum levels of free insulin-like growth factor (IGF)-I and IGF-binding protein-1 in prepubertal children with idiopathic short stature

The study was performed to evaluate the relationships among serum free and total insulin-like growth factor (IGF)-I, IGF-binding protein-1 (IGFBP-1), IGFBP-3, and insulin concentrations in prepubertal children with idiopathic short stature (ISS). Eighteen children with ISS and 15 age-matched controls were included in the study. All short children had a height standard deviation score of more than 2 below the mean, and maximum stimulated GH levels greater than 10 microg/l after two standard provocation tests. The serum levels of free IGF-I were significantly lower in short children (1.6 +/- 0.3 microg/l) than in the controls (2.8 +/- 0.6 microg/l, P<0.05), while total IGF-I levels were slightly, but not significantly, lower in short children than in controls. The serum levels of IGFBP-1 were significantly higher in the ISS group (124.6 +/- 5.6 microg/l) than in controls (80.0 +/- 8.7 microg/l, P < 0.0001). The fasting insulin and IGFBP-3 levels were similar in both groups. A stepwise regression analysis for all subjects revealed that IGFBP-1 is the only independent predictor of log free IGF-I (R2 = 0.23, P<0.01). The present study shows that the serum levels of free IGF-1 are significantly lower and insulin-like growth factor-binding protein-1 levels are higher in prepubertal children with idiopathic short stature, as compared with age-matched controls. The high IGFBP-1 may contribute to growth retardation in a subgroup of idiopathic short stature through a decrease in free IGF-1.     

Serum concentrations of free and total insulin-like growth factor-I, IGF binding proteins -1 and-3 and IGFBP-3 protease activity in boys with normal or precocious puberty

OBJECTIVE  Circulating IGF-I and IGF binding protein-3 (IGFBP-3) levels both increase in puberty where growth velocity is high. The amount of free IGF-I is dependent on the IGF-I level and on the concentrations of the specific IGFBPs. Furthermore, IGFBP-3 proteolysis regulates the bioavailability of IGF-I. However, the concentration of free IGF-I and possible IGFBP-3 proteolytic activity in puberty has not previously been studied.
SUBJECTS AND MEASUREMENTS  We investigated serum levels of easily dissociable IGF-I concentrations and ultrafiltrated free IGF-I levels by specific assays in 60 healthy boys and in 5 boys with precocious puberty before and during GnRH agonist treatment. In addition, total serum IGF-I, IGFBP-1 and IGFBP-3 levels as well as IGFBP-3 protease activity were determined.
RESULTS  Free (dissociable and ultrafiltrated) IGF-I concentrations were significantly higher in pubertal boys than in prepubertal children and correlated significantly with the molar ratio between IGF-I and IGFBP-3 ( r =0.69, P <0.0001 and r =0.54, P =0.0008, respectively) and inversely with IGFBP-1 ( r =−0.47, P <0.0001 and r =−0.43, P =0.0003, respectively). Multiple regression analysis suggested that IGFBP-3 level, and not IGFBP-1, was the major determinant of the free IGF-I serum level in normal boys. Free IGF-I levels were elevated in boys with precocious puberty and decreased during GnRH treatment. IGFBP-3 proteolysis was constant throughout puberty (mean 20%).
CONCLUSIONS  We conclude that easily dissociable and ultrafiltrated free IGF-I serum levels are increased in boys with normal and precocious puberty and suggest that the increased free IGF-I serum concentration in puberty primarily reflects changes in total concentrations of IGF-I and IGFBPs secondary to increased GH secretion, but that it is not influenced by changes in IGFBP-3 proteolysis.     

Elevated free IGF-I levels in prepubertal Hispanic girls with premature adrenarche: relationship with hyperandrogenism and insulin sensitivity.

Girls with premature adrenarche (PA) (the onset of pubic hair before the age of 8 yr associated with elevated levels of adrenal androgens and no evidence of true puberty or adrenal dysfunction) may be at increased risk for development of polycystic ovarian syndrome (PCOS). Alterations in the IGF system, including elevated free IGF-I, have been demonstrated in PCOS and may be involved in its pathogenesis. Hyperinsulinemia, elevated total IGF-I, and decreased IGF-binding protein-1 (IGFBP-1) have also been reported in PA. Dysregulation of the IGF system may be involved in the pathogenesis of PA and its progression to PCOS. We compared the insulin/IGF system in 17 prepubertal girls with PA and nine prepubertal controls. Both groups were predominantly obese. Total and free IGF-I were elevated in the premature adrenarche group. No differences in basal insulin, insulin area under the curve in response to an oral glucose tolerance test, or IGFBP-1 were noted. These effects persisted when adjusted for adiposity using body mass index-Z score. Total and free IGF-I were positively correlated, and IGFBP-1 was negatively correlated with Delta4-androstenedione, but not with dehydroepiandrosterone sulfate. Free IGF-I trended toward higher levels in the insulin-resistant subgroup, compared with the insulin-sensitive subgroup. These results suggest altered regulation of the insulin/IGF system in prepubertal girls with PA and a possible role for free IGF-I in the pathogenesis of the hyperandrogenism of PA as well as its progression to PCOS.     

The phosphorylation status of insulin-like growth factor-binding protein-1 in prepubertal obese children

OBJECTIVE: We measured the total and nonphosphorylated insulin-like growth factor-binding protein (IGFBP)-1 concentrations in obese children to determine the effect of obesity on the status of IGFBP-1 phosphorylation. We also measured the serum levels of insulin, total and free IGF-I, and IGFBP-3 to investigate their relationships to the IGFBP-1 phosphorylation status in obese subjects. SUBJECTS AND METHODS: Nineteen prepubertal obese and 15 age-matched control children were included in the study. The serum levels of total and nonphosphorylated IGFBP-1 were determined by noncompetitive RIAs. RESULTS: The serum levels of total and nonphosphorylated IGFBP-1 were significantly lower in the obese group (48.7+/-5.6 microgram/l, P<0.001 and 11.1+/-1.9 microgram/l, P<0.01 respectively) than in the controls (86.7+/-9.0 microgram/l and 28.8+/-6.2 microgram/l respectively). However, the ratio of nonphosphorylated IGFBP-1 to total IGFBP-1 did not differ significantly between the obese and control groups. The circulating free IGF-I level was significantly higher in the obese children than in the controls (P<0.05), while the serum levels of insulin, total IGF-I and IGFBP-3 were not significantly different between the two groups. A stepwise regression analysis of the combined group revealed that only the total IGFBP-1 level was an independent predictor of the free IGF-I concentration (P<0.001). CONCLUSION: The present study shows that both total and nonphosphorylated IGFBP-1 concentrations are decreased in obese children and the increased free IGF-I level in obese children is related to the reduced total IGFBP-1 level, but unrelated to the change in the IGFBP-1 phosphorylation status.     

Effects of cholinergic modulation on serum insulin-like growth factor4 and its binding proteins in normal and diabetic subjects*

OBJECTIVE We wished to study alterations In serum Insulin-like growth factor-I (IGF-I) and its binding proteins in subjects with insulin dependent diabetes mellitus (IDDM) and possible relations with metabolic and GH secretory status, before and after cholinergic modulation. In addition, we have Investigated whether cholinergic modulation exerts any effects on IGF-I secretion, Independently of any actions on GH secretory status. DESIGN All subjects received OH releasing hormone (GHRH) 1-44; 80 μg i.v.) alone and 60 minutes following 120mg of pyridostigmine orally or 200 mg of plrenzepine orally. The three tests were carried out In random order at least one week apart. Blood was sampled at 15-mInute Intervals over 120 minutes. PATIENTS Twelve male subjects with IDDM and no clinical evidence of complications were selected on the basis of HbA₁ levels to provide a wide range of metabolic control. SIX normal male subjects were also studied. MEASUREMENTS Serum IGF-I, IGF-binding protein 1 (IGFBP-1) and IGFBP-3 were measured at regular intervals throughout the study. Fasting plasma glucose and HbA₁ were measured before each study to provide measures of metabolic control. RESULTS Serum IGF-I and IGFBP-3 levels were significantly lower while serum IGFBP-I levels were significantly higher In the diabetic subjects. Plrenzepine had no effect on serum IGF-I, IGFBP-1 or IGFBP-3 In diabetic subjects but caused a significant Increase In serum IGF-I and IGFBP-3 levels in normal subjects. Pyridostigmine had no effect on IGF-I, IGFBP-1 or IGFBP-3 In either diabetic or normal subjects. IGFBP-1 levels were significantly correlated with fasting plasma glucose but no correlation was demonstrated between measures of diabetic control and serum IGF-I or IGFBP-3 levels In diabetic subjects, nor was there any correlation between OH responses to GHRH alone or after plrenzepine or pyridostigmine pretreatment and serum levels of IGF-I, IGFBP-1 or IGFBP-3. CONCLUSION These data confirm that subjects with IDDM have reduced serum IGF-I and IGFBP-3 and Increased IGFBP-1 levels, the latter being directly related to the fasting plasma glucose concentrations. The absence of any relation between changes In the IGF-I system and altered GH neuroregulation after cholinergic modulation suggests that changes In IGF-I are not the sole contributors to the altered GH neuroregulation which occurs In IDDM. We have also shown an acute stimulatory effect of pirenzepine on serum IGF-I and IGFBP-3 In normal subjects which Is not present in IDDM although the underlying mechanism Is unknown.     

The 'dawn phenomenon' in adolescents with insulin dependent diabetes mellitus: possible contribution of insulin-like growth factor binding protein-1

OBJECTIVE Insulin resistance increases during adolescence, and is exaggerated in patients with insulin dependent diabetes mellitus (IDDM). A relative deficiency of insulin-like growth factor-I (IGF-I) may contribute to this increased insulin requirement. Two mechanisms have been proposed: (a) increased GH secretion, caused by failure of IGF feedback control, leading to increased insulin resistance and (b) lack of Insulin-like action of the IGFs which is reinforced by high plasma levels of IGFBP-1, an inhibitor of IGF action. The contribution of these two mechanisms to the ‘dawn phenomenon’ is assessed. DESIGN The two possible mechanisms were studied during the dawn rise of glucose in pubertal adolescent patients with IDDM. Two overnight studies were performed in each subject. Patients remained on the same insulin regimen throughout. SUBJECTS Twenty-two diabetic adolescent subjects, aged (mean ± SEM) 14.0 ± 0.4 years, duration of IDDM 7.9 ± 0.8 years, were recruited. Pubertal status was: group 1 (breast stage 1–2; testicular volume < 4–8ml) 3 male and 4 female, group 2 (breast stage 3; testicular volume 10–12 ml) 0 male 4 female, group 3 (breast stage 4–5; testicular volume 15–25 ml) 4 male and 7 female. Height standard deviation score (mean ± SD) (-0.02 ± 099) and dally insulin dose (50.4 ± 3.1 U/day) did not change between studies. There were no differences in HbA1 (study A 11.26 ± 0.45%, study B 11.09 ± 0.42%). METHODS The subjects were admitted for the two studies 0.3 ± 0.03 years apart. Blood samples were taken via an indwelling cannula every 20 minutes between 1900 and 0700 h. MEASUREMENTS GH was assayed every 20 minutes, IGFBP-1, glucose and free Insulin every hour and lGF-I at 0700h. GH, IGFBP-1, IGF-I and free insulin were measured by radioimmunoassay. IGFBPs were also analysed by Western ligand blotting techniques. GH profiles were analysed by Pulsar and results compared by paired Student's t-test. The relations between the dawn rise In glucose and the changes in IGFBP-1, GH and free insulin were examined by multiple linear regression analysis. RESULTS Serum IGFBP-1 levels rose overnight In the two studies (study A, from 9·1 at 2200 to 59 ± 9μg/l at 0700 h; study B, from 10±1 at 2100 to 64 ± 14μg/l at 0700h) whilst insulin levels fell from 47 ± 5 at 2200 to 16 ± 2mU/l at 0700 h (study A) and from 45·5 at 2000 to 14 ± 2mU/l at 0700 h (study B). Glucose levels fell from 16.0 ± 1.0 to 9.3 ± 0.9 mmol/l at 0400h, and then rose to 11.9 ± 1.1 mmol/l at 0700 h during study A, and from 13.4 ± 1.3 to 10.1 ± 1.1 mmol/l at 0400 h and then rose to 13.5 ± 1.0 mmol/l at 0700 h during study B. There were no differences in GH secretion between studies (mean GH levels (mean ± SD) (study A, 15.7 ± 6.6 mU/I; study B, 16.2 ± 7.1 mU/l; correlation within subjects between studies r= 0.77, P < 0.001), sum of GH peaks (study A, 189.9 ± 903 mU/l; study B, 185.8 ±100.2 mU/l; r= 0.57, P= 0.006)). Mean GH levels varied with pubertal stage (group 1,12.1 ± 1.5 mU/l; group 2, 23.3 ± 2.1 mU/I; group 3, 15.3 ± 1.2mU/I). Serum IGF-l levels were not different (study A, 203 ± 12 μg/l; study B, 218 ± 13 μg/l). REGRESSION ANALYSIS The change In plasma glucose between 0200 and 0700 h In both studies related to free insulin, IGFBP-1 and the sum of the GH levels over the preceding hour (log glucose =7.87 + 5.32 log IGFBP-1 (P= 0.0001) ?5.05 log free insulin (P= 0.0001)-1.44 log GH (P= 0.004); R²= 72%). Mean overnight GH levels did not predict the morning rise In plasma glucose. CONCLUSION The morning rise of IGFBP-1 and plasma glucose appear to be related in this group of subjects with IDDM and this was a consistent finding In the two studies. This relation was additive to the effect of Insulin deficiency. No positive relation was noted between GH secretion and glucose levels. These findings support the hypothesis that the increased GH secretion In IDDM Is a marker of IGF-I deficiency rather than a direct causal factor in the increase In insulin resistance. The IGFs may therefore have a direct role In glucose homeostasis via the ‘free’ fraction of circulating IGFs, the availability of which may be modulated by changes in IGFBP-1 levels.     

Modifications of growth velocity and the insulin-like growth factor system in children with acute lymphoblastic leukemia: a longitudinal study

The basis of impaired growth in children with acute lymphoblastic leukemia (ALL) is multifactorial, including the disease itself, infections, undernutrition, and adverse effects of therapy. Because growth is regulated by the GH-insulin-like growth factor (IGF) system, which may be altered in catabolic states, we studied serum IGF-I, free IGF-I, IGF-II, the IGF-binding proteins (IGFBP-1 to -3), and total and free acid-labile subunit (ALS) levels in 26 prepubertal children with ALL at diagnosis (n = 26) and 6 (n = 21), 12 (n = 21), 18 (n = 21), 24 (n = 20), 30 (n = 16), and 36 months (n = 16) after beginning treatment to investigate the effects of disease and therapy on this system and its relationship with growth in these patients. Intensive chemotherapy compromised growth, with a catch-up period beginning when maintenance therapy began and increased growth after stopping therapy. Weight increased 6 months after chemotherapy withdrawal, whereas the body mass index was increased both at 6 months after diagnosis and 6 months after therapy suppression. Serum IGF-I, IGF-II, IGFBP-3, and total and free ALS levels were significantly decreased at diagnosis. Normalization of IGF-II and IGFBP-3 occurred 6 months after diagnosis, and normalization of IGF-I and total and free ALS occurred 1 yr after terminating therapy. IGFBP-1 and IGFBP-2 levels were significantly increased at diagnosis and decreased after stopping therapy. Free IGF-I was elevated throughout the study. IGF and IGFBP-3 levels showed a close relationship to growth velocity at the end of chemotherapy, with this correlation remaining until at least 1 yr after therapy withdrawal. In conclusion, intensive chemotherapy compromises linear growth in prepubertal ALL patients, and this phenomenon is associated with alterations in the IGF system. However, when therapy is reduced or stopped, catch-up growth occurs, but various parameters of the GH-IGF axis remain impaired. This suggests the need for a longer period of follow-up to assess the long-term risks of therapy and disease on this system.     

Circulating acylated and total ghrelin and galanin in children with insulin-treated type 1 diabetes: relationship to insulin therapy, metabolic control and pubertal development

OBJECTIVE: To study the circulating levels of two gut-derived peptides in children with type 1 (insulin-dependent) diabetes mellitus (IDDM). RESEARCH DESIGN AND METHODS: Plasma levels of ghrelin, both total ghrelin (TG) and the acylated form (AG), and galanin and their relationships with insulin dosage, metabolic control, IGFBP-1, body mass and pubertal development were evaluated in 91 children, aged 11.1 +/- 2.7 years, affected by IDDM and treated with insulin. Ninety-one healthy children were selected as controls. RESULTS: Body mass index (BMI)-adjusted levels of both forms of ghrelin were reduced in IDDM compared with healthy subjects, with greater values in prepubertal than pubertal IDDM subjects. A negative association was found between AG and fasting insulin serum levels and insulin resistance [measured by using the homeostasis model assessment of insulin resistance (HOMA IR)] among the healthy children. IDDM children showed a negative association of their plasma ghrelin (both acylated and total) with daily insulin dosage, and the three adiposity indices (BMI, skinfold thickness and percentage fat mass). IGFBP-1 levels were higher among the IDDM children without any association with ghrelin serum values. BMI-adjusted plasma levels of galanin were higher among IDDM compared to healthy subjects, irrespective of sex or pubertal development. Greater values for galanin were found among pubertal than prepubertal subjects in both groups without any significant differences between the genders. A positive association was found between galanin and BMI in both groups and between galanin and haemoglobin A1c (HbA1c) among the IDDM children. No relationship existed between either galanin and fasting serum insulin among the healthy subjects or galanin and both insulin dosage or duration of treatment among the IDDM subjects. CONCLUSIONS: The associations found between both ghrelin and galanin with adiposity indices could be considered as an indirect signal of involvement of the two peptides in the development of the nutritional status of the IDDM adolescents. The reduction in both forms of ghrelin could be involved in the development of the body mass increase of IDDM subjects with opposite effects, either influencing insulin sensitivity or exerting a compensatory restraint of feeding.     

Growth hormone/insulin-like growth factor axis in patients with subclinical thyroid dysfunction

ObjectiveOur aim was to evaluate serum concentrations of GH, IGF-I, and insulin-like growth factor-binding protein-3 (IGFBP-3) in patients with subclinical thyroid dysfunction before and after normalization of thyroid function.Design and methodsThe study included 51 patients (mean age 42.2 ± 1.8 years) with subclinical hypothyroidism and 30 patients (mean age 44.3 ± 2.4 years) with subclinical hyperthyroidism. A group of 37 euthyroid healthy subjects were studied as controls. Serum concentrations of TSH, FT4, FT3, GH, insulin, IGF-I, and IGFBP-3 were measured in all patients before starting therapy and after normalization of thyroid function. The dosage of levothyroxine (LT4) and antithyroid drugs was adjusted in attempt to keep the serum-free thyroxine (FT4) and thyrotropin (TSH) concentrations within the normal range.Main outcomeBaseline growth hormone levels were similar with hypothyroid group and hyperthyroid group in relation to euthyroid control subjects. Fasting serum IGF-I levels were significantly lower in the subclinical hypothyroid group compared with the control group. On the other hand, IGF-I levels of subclinical hyperthyroid patients and control group were similar. After normalization of thyroid function tests, IGF-I concentrations were increased in subclinical hypothyroid subjects, but unchanged in subclinical hyperthyroid subjects. Patients with subclinical hyperthyroidism showed slightly lower mean serum IGFBP-3 concentrations than those found in control group, but the difference was not statistically significant. Serum GH and IGFBP-3 levels were unaltered by treatment.ConclusionsIn this study, it was shown that GH–IGF axis was not affected in patients with subclinical hyperthyroidism, while it was affected in patients with subclinical hypothyroidism. That is, investigation of the axis in subclinical hyperthyroidism would not bring any extra advantages, but LT4 replacement therapy could prevent abnormalities related to GH–IGF axis in patients with subclinical hypothyroidism.     

Inflammation is a modulator of the insulin-like growth factor (IGF)/IGF-binding protein system inducing reduced bioactivity of IGFs in cystic fibrosis

OBJECTIVE: In inflammatory bowel diseases, increased serum interleukin (IL)-6 levels are associated with high serum insulin-like growth factor-binding protein 2 (IGFBP-2) levels, and cytokines modify the insulin-like growth factor (IGF)/IGFBP system in models in vitro. In cystic fibrosis (CF) the IGF/IGFBP system has not been extensively studied, and relationships with proinflammatory cytokines have not been explored. The aim of this study was to investigate the IGF/IGFBP system and verify changes dependent on IL-1beta, IL-6, tumour necrosis factor alpha (TNFalpha), and insulin. METHODS: Eighteen subjects with CF (mean age 26.6 +/- 1.1 years) and 18 controls, comparable for age, sex, and body mass index, were enrolled. Serum IGF-I, IGF-II, IGFBP-2, IGFBP-3, IL-1beta, IL-6, TNFalpha, insulin and C-peptide were measured. Different molecular forms of IGFBP-2 and IGFBP-3 were investigated by Western immunoblotting. The patients were analysed as a whole and as two subgroups depending on established clinical criteria (Swachman-Kulczycki score). RESULTS: Patients had higher serum concentrations of IL-1beta, IL-6, TNFalpha and IGFBP-2 than controls. Serum concentrations of IGF-I and IGF-II were significantly lower and insulin and C-peptide levels significantly increased in CF compared with healthy controls whereas IGFBP-3 serum concentrations were similar, with comparable IGF-I/IGFBP-3 and decreased IGF-I/IGFBP-2 and IGF-II/IGFBP-2 molar ratios. From correlation analysis we detected a significant positive correlation between IGFBP-2 and IL-6 and a negative correlation between IGFBP-2 and IGFBP-3. CONCLUSIONS: Our findings suggest that inflammation is an important modulator of the IGF/IGFBP system with an overall reduction in IGF bioactivity in CF.     

Growth and insulin-like growth factors (IGFs) in children with insulin-dependent diabetes mellitus at the onset of disease: evidence for normal growth, age dependency of the IGF system alterations, and presence of a small (approximately 18-kilodalton) IGF-binding protein-3 fragment in serum

Data on growth of children with insulin-dependent diabetes mellitus (IDDM) before the onset of disease are conflicting, and although the insulin-like growth factor (IGF) system has almost invariably been found altered at diagnosis, most of previous studies are affected by the small number of patients investigated. We studied 60 IDDM children at the onset of disease, comparing their stature with target height, normal growth standards, and height of 102 sex- and age-matched controls. Furthermore, we assessed serum IGF-I, IGF-II, and IGF-binding protein-3 (IGFBP-3) levels and IGFBP-3 circulating forms. IDDM children were subdivided into 2 groups according to an age above (n = 26) or below (n = 34) 6 yr. The values of endocrine variables of diabetics older than 6 yr were compared with those of 34 age-matched controls. Although the height of diabetics was higher than growth reference values (mean height +/- SD, 0.64+/-1.4 z-score) and their target height (mean target height +/- SD, 0.1+/-0.84 z-score; P < 0.005), no significant difference in height was found between IDDM children and controls (mean height +/- SD, 0.64+/-0.95 z-score) even analyzing the 2 age groups separately. Overall, IDDM children showed reduced levels of IGF-I (mean +/- SD, -0.65+/-1.9 z-score) and normal levels of IGF-II (mean +/- SD, -0.05+/-1.2 z-score) and IGFBP-3 (mean +/- SD, -0.06+/-1.2 z-score). However, whereas patients younger than 6 yr showed normal values of IGF-I, IGF-II, and IGFBP-3, these peptides were significantly reduced in older subjects compared with either younger IDDM children or controls (P < 0.01). IGFBP-3 immunoblot analysis revealed the presence of an approximately 18-kDa fragment of IGFBP-3 in addition to the major approximately 29-kDa fragment and the intact form (approximately 42-39 kDa) in 46 of 60 IDDM patients, whereas the approximately 18-kDa band was absent in all 34 control sera. No relationship was found between the endocrine variables and stature at diagnosis. In conclusion, our results indicate that IDDM children at the onset of disease are not taller than healthy peers and have increased IGFBP-3 proteolytic activity. Finally, although the IGF system is normal in younger IDDM children, older patients have reduced IGF levels.     

Growth hormone, IGF-I and its binding proteins (IGFBP-1 and -3) in adult uraemic patients undergoing peritoneal dialysis and haemodialysis

OBJECTIVE: The GH/IGF axis is altered in chronic renal failure (CRF). CRF patients usually show normal or high serum concentrations of GH and IGF-I, whereas all IGF binding proteins (IGFBP-1 to -6), except IGFBP-5, considerably increase with declining renal function. The aims of the present study were to quantify serum concentrations of GH, IGF-I, IGFBP-1 and IGFBP-3 in a group of patients with CRF, and determine whether there were differences according to the type of dialysis, that is, peritoneal dialysis (PD) and haemodialysis (HD). DESIGN: A cross-sectional study in the setting of a dialysis unit of a general hospital. PATIENTS AND MEASUREMENTS: We studied 108 dialysis patients treated by PD (n = 54, 32 males and 22 females, mean age 61.0 +/- 1.4 years) or HD (n = 54, 31 males and 23 females, age 62.6 +/- 1.5 years). A group of 42 healthy subjects of similar age, sex and body mass index (BMI) served as the control group. Baseline serum concentrations of GH, insulin, IGF-I, IGFBP-1 and IGFBP-3 were measured in all patients and control subjects. RESULTS: Fasting serum concentrations of IGF-I and its binding proteins (IGFBP-1 and IGFBP-3) were significantly higher in dialysis patients than in subjects with normal renal function. IGF-I (248.9 +/- 23.4 vs. 205.5 +/- 15.5 micro g/l, NS), IGFBP-3 (5.6 +/- 0.4 vs. 5.5 +/- 0.2 mg/l, NS) and IGFBP-1 (36.1 +/- 5.9 vs. 44.1 +/- 6.5 micro g/l, NS) concentrations were similar in both groups of dialysis (PD vs. HD) patients. However, GH (2.3 +/- 0.3 vs. 1.1 +/- 0.1 micro g/l, P < 0.001) and insulin (40.4 +/- 4.5 vs. 30.1 +/- 3.1 micro U/ml, P < 0.05) levels were significantly higher in the PD group than in the HD group. Both groups of dialysis patients showed significantly higher levels of insulin than healthy subjects (14.7 +/- 1.9 micro U/ml, P < 0.0001 and P < 0.01 for PD and HD, respectively). In both groups of dialysis patients, IGF-I correlated inversely with IGFBP-1 (PD group r = -0.46, P = 0.0006; HD group r = -0.57, P = 0.0001) and directly with IGFBP-3 (PD group r = 0.44, P = 0.001; HD group r = 0.73, P = 0.001). No correlation between insulin and IGFBP-1 was found in any of the groups studied. CONCLUSIONS: These findings demonstrate that adult dialysis patients have elevated IGF-I, IGFBP-1 and IGFBP-3 serum concentrations compared with subjects with normal renal function. Only GH and insulin show statistically significant differences in relation to type of dialysis. Finally, the negative correlation between IGF-I and IGFBP-1 and the positive correlation between IGF-I and IGFBP-3 are maintained in both groups of adult dialysis patients.     

The combination of insulin-like growth factor I and insulin-like growth factor-binding protein-3 reduces insulin requirements in insulin-dependent type 1 diabetes: evidence for in vivo biological activity

Insulin-like growth factor-I (IGF-I) enhances insulin action in normal subjects and in patients with both type 1 and 2 diabetes; however, its administration is associated with significant side effects in a high percentage of patients. The coadministration of IGF binding protein-3 (IGFBP-3, the predominant IGF binding protein in serum) with IGF-I limits IGF-I inducible side effects, but it does not attenuate the ability of IGF-I to enhance protein synthesis and bone accretion; therefore, we determined whether IGF-I/IGFBP-3 would retain biological activity in type 1 DM and limit side effects associated with free IGF-I administration. Twelve patients received recombinant human IGF-I plus IGFBP-3 (2 mg/kg-day) by continuous sc infusion for 2 weeks. Each subject served as his own control; and, during a paired 2-week period, each received a placebo infusion. The order of the treatments was randomized. Subjects were placed on a constant caloric intake but were allowed to adjust insulin doses to maintain appropriate levels of glycemic control. Subjects measured blood glucose four times per day at home and kept a log of their insulin use. Frequent sampling for glucose, insulin, and GH was conducted during four inpatient study periods, one at the beginning and one at the end of each 2-week study interval. During IGF-I/IGFBP-3, insulin doses were reduced by 49%, and mean serum glucose was reduced by 23%. Free insulin levels obtained during frequent sampling in hospital fell 47% on IGF-I/IGFBP-3, compared with control, but showed no change with placebo. Concomitant glucose measurements did not differ in the two treatment groups. There was no change in body weight. Fructosamine levels decreased by 12%, but this was not significant (P < 0.1). Fasting triglyceride was unchanged, but cholesterol declined from 170 +/- 24 to 149 +/- 31 mg/dL (P < 0.05). IGFBP-2 (an IGF-I-dependent responsive variable) rose from 141 +/- 56 to 251 +/- 98 ng/mL (P < 0.01) on IGF-I/IGFBP-3. To analyze the mechanism by which IGF-I/IGFBP-3 might reduce insulin requirements, the change in serum GH was quantified. Mean GH levels were reduced by 72%, from 2.48 to 0.55 ng/mL (P < 0.001). An equal number (40%) of drug- and placebo-treated subjects had minor hypoglycemic episodes at home that required adjustment of insulin doses. No episode was classified as severe. In contrast to previous studies with free IGF-I, there were no cases of edema, headache, jaw pain, retinal edema, or Bell's palsy. No subject withdrew because of drug complications. These findings indicate that IGF-I/IGFBP-3 is biologically active on carbohydrate metabolism, as measured by a decrease in insulin requirements in patients with type 1 diabetes. Further studies will be required to determine the long-term safety and efficacy of this combination in patients with insulin resistance and diabetes.     

Insulin-like growth factor binding protein 1 response to acute insulin induced hypoglycaemia in Type 1 diabetes

OBJECTIVES Insulin Is believed to be the prime regulator of Insulin-like growth factor binding protein 1 (IGFBP-1) secretion, and In normal subjects acute insulin Induced hypoglycaemla exerts a rapid effect on concentrations of IGFBP-1, and may also Influence Insulin-like growth factor I (IGF-I) concentrations. The rise In IGFBP-1 concentrations in normal subjects following hypoglycaemia has been suggested to be due to suppression of endogenous insulin secretion. We have examined this further by studying diabetics with no endogenous Insulin secretion. DESIGN We have compared the IGFBP-1 response to acute insulin Induced hypoglycaemia in normal subjects and patients with Type 1 (insulin dependent) diabetes mellitus. METHODS Insulin tolerance test8 were performed using a bolus of Insulin (0·15 U/kg), in six control subjects and six patients with Type 1 diabetes. MEASUREMENTS Serum levels of IGFBP-1, insulin, glucose, and IGF-I were measured at regular Intervals during the insulin tolerance test. RESULTS Blood glucose fell to a nadir which coincided with the onset of the acute autonomic reaction ‘R’ In both groups. The basal concentration of IGF-I was significantly lower In the diabetic group at 0·4 ± 0·1 kU/l, compared to 0·9 ± 0·1 kU/l In the control group, but there was no significant change In IGF-I concentrations In response to hypoglycaemia In either group. Hypoglycaemia provoked a fall In IGFBP-1 In patients with Type 1 diabetes, from 38 ± 9 μg/l basally to 17 ± 3 μg/l at R + 120 minutes, with a return to basal values of 45 ± 11 μg/l at R + 180 minutes. In the control subjects there was no fall In IGFBP-1, but a significant Increase to 71 ± 14 μg/l at R + 180 minutes. CONCLUSION This difference In the IGFBP-1 response In the presence of a similar glucose response suggests that In Type 1 diabetes there may be different sensitivities to the actions of exogenous Insulin on IGFBP-1 regulation.     

Effects of pure ethanol and alcopops on glucose, insulin, and the insulin-like growth factor system in healthy subjects.

INTRODUCTION: Alcohol induces disturbances in insulin-like growth factor-I (IGF-I) and IGF binding protein-1 (IGFBP-1) levels. The aim of the present study was to compare pure ethanol and alcopop effects on total and free IGF-I, IGFBP-1, IGF-I:IGFBP-1 complex, insulin and plasma glucose levels in healthy subjects. METHODS: Five males and seven females (21-51 years) consumed pure ethanol and alcopops with identical alcohol content in a cross-over design after 6h fasting. Blood samples were obtained for determination of serum ethanol and plasma glucose at 0, 30, 60, 90, 120 and 180 min. Serum total and free IGF-I, IGFBP-1, IGF-I:IGFBP-1 complex, and insulin were measured at 0, 60 and 180 min. RESULTS: Area under the curve for serum ethanol concentration was significantly less following alcopop compared to pure ethanol (1124+/-201 vs. 1691+/-359 mmol/Lh, P<0.01). Serum insulin and glucose levels were unchanged by ethanol while alcopop intake was followed by a transient increase in glucose and insulin levels (P<0.05). Pure ethanol and alcopop reduced free IGF-I levels by the end of the study period (P=0.05). IGFBP-1 and the IGF-I:IGFBP-1 complex increased following ethanol intake (P<0.05) while only a small transient IGFBP-1 increase was observed following alcopop intake. No change in total IGF-I was observed. CONCLUSION: Both drinks resulted in reduced free IGF-I levels, however, only pure ethanol increased IGFBP-1 and the IGF-I:IGFBP-1 complex. Alcopop intake was associated with a transient increase in IGFBP-1 and unchanged IGF-I:IGFBP-1 complex levels probably due to marked changes in insulin and glucose levels.     

Lack of physiological suppression of circulating IGFBP-1 in puberty in patients with insulin-dependent diabetes mellitus

OBJECTIVE: To evaluate the interaction between serum free insulin, insulin-like binding protein (IGFBP)-1 and leptin concentrations during puberty in insulin-dependent diabetes mellitus (IDDM). DESIGN: Adolescent patients with IDDM (n=101, age >9 years, duration >2 years) from the Outpatient Clinic of the Department of Pediatrics at Oulu University Hospital, and non-diabetic controls, were recruited to the study. Free insulin, IGFBP-1, leptin and insulin antibody concentrations were measured from a fasting serum sample. RESULTS: Free insulin concentrations were lower in the patients than in the controls (4.3+/-2.3 mU/l compared with 6.5+/-3.1 mU/l, P<0.001), and there was an inverse correlation between free insulin and fasting blood glucose in the boys with diabetes (r=-0.53, P<0.001), whereas a positive correlation was observed between free insulin and leptin concentrations in the girls with diabetes (r=0.30, P=0.020). The IGFBP-1 concentrations were greater in the patients than in the controls (16.5+/-10.6 microg/l compared with 4.0+/-3.3, P<0.001), and they correlated significantly with blood glucose (r=0.63, P<0.001) and free insulin (r=-0.35, P<0.001). No significant difference was observed in the leptin concentrations between the patients and controls overall, despite greater total body fat in the girls with diabetes compared with the control girls. CONCLUSIONS: Adolescents with IDDM are characterised by morning hypoinsulinaemia and high circulating IGFBP-1 concentrations, which may contribute to insulin resistance and impaired metabolic control during puberty. The mechanism behind the increased total body fat in the postpubertal female patients remains to be determined.     

Use of the ligand immunofunctional assay for human insulin-like growth factor ((IGF) binding protein-3 (IGFBP-3) to analyze IGFBP-3 proteolysis and igf-i bioavailability in healthy adults, GH-deficient and acromegalic patients, and diabetics

The ligand immunofunctional assay for plasma insulin-like growth factor (IGF) binding protein (IGFBP)-3 developed in our laboratory provides for specific measurement of intact, as opposed to proteolyzed, IGFBP-3. IGFBP-bound IGFs are dissociated and separated by acid pH ultrafiltration; thereafter, intact and proteolyzed IGFBP-3 are captured by a monoclonal antibody in a solid-phase assay and incubated with (125)I-IGF-I, which detects the intact protein but not its proteolytic fragments. This assay was combined with assays for IGF-I (RIA of the ultrafiltrate) and total IGFBP-3 (immunoradiometric assay) to quantify the percentage of proteolyzed IGFBP-3 (percent proteolyzed IGFBP-3) and to calculate the IGF-I/intact IGFBP-3 ratio as an index of the fraction of exchangeable IGF-I bound to IGFBP-3. This fraction represents most of the IGF-I that is bioavailable. Because GH and insulin control the hepatic production and plasma concentrations of IGF-I and IGFBP-3, we set out to determine whether variations in the secretion of the two hormones are involved in the regulation of IGFBP-3 proteolysis. The study included adult populations of 36 healthy subjects, 23 hypopituitary patients untreated with GH, 43 acromegalics (13 untreated), 42 insulin-treated type 1 diabetics [insulin-dependent diabetes mellitus (IDDM)] patients, and 50 type 2 diabetics [non-IDDM (NIDDM)] patients, 22 of whom were insulin-treated and the remaining 28 treated with sulfonylurea and/or metformin). Unlike IGF-I and (to a lesser extent) total IGFBP-3 levels, which decline with age, percent proteolyzed IGFBP-3 seemed relatively stable. In healthy adults, the mean +/- SEM was 29.4 +/- 1.9 for subjects less than 45 yr old and was slightly (but not significantly) lower, 25.7 +/- 3, for those of more than 45 yr. There was no difference between male and female subjects. In GH-deficient patients, despite severely depressed IGF-I levels, percent proteolyzed IGFBP-3 and IGF-I/intact IGFBP-3 ratios were within the normal range. Among acromegalics, percent proteolyzed IGFBP-3 was elevated: 36.6 +/- 3.3 for patients of less than 45 yr, 33.3 +/- 3.2 for patients of more than 45 yr (P = 0.02 vs. healthy subjects). Consequently, the effects of excessive IGF-I synthesis are exacerbated by the enlarged exchangeable fraction of IGFBP-3-bound IGF-I. There was no significant difference in percent proteolyzed IGFBP-3 between GH-deficient patients before and after GH treatment or between treated and untreated acromegalics. In IDDM patients, the means for percent proteolyzed IGFBP-3 were higher than those in healthy adults: 36.7 +/- 3.7 (P = 0.03) and 31.3 +/- 3.3 for subjects of less than 45 and more than 45 yr, respectively. In NIDDM patients, all of whom were more than 45 yr old, the means were 35.2 +/- 2.5 (P = 0.02) for insulin-treated patients and 33 +/- 2.5 for the group treated orally. Among the diabetics, increased IGFBP-3 proteolysis resulted in an IGF-I/intact IGFBP-3 ratio that was normal for IDDM patients of less than 45 yr and above normal (P = 0.01) for the others. Percentage proteolyzed IGFBP-3 and the IGF-I/intact IGFBP-3 ratio were inversely related to body mass index in IDDM patients (r = -0.42, P = 0.008; and r = -0.31, P = 0.05, respectively) and to percentage glycosylated hemoglobin in all insulin-treated diabetics (r = -0.25, P = 0.05; and r = -0.33, P = 0.008, respectively). There was also an inverse relationship between IGF-I/intact IGFBP-3 ratios and IGFBP-1 levels in healthy adults (r = -0.39, P = 0.03) and orally treated NIDDM patients (r = -0.37, P = 0.05). Percentage proteolyzed IGFBP-3 was positively correlated to total IGFBP-3 in healthy adults (r = 0.65, P = 0.0001) and in all the groups of patients. It was negatively correlated to IGF-I/total IGFBP-3 in healthy subjects (r = -0.40, P = 0.02) and diabetics (r = -0.30, P = 0.005). This suggests an autoregulatory mechanism controlling the bioavailability of IGFBP-3-bound IGF-I in the 140-kDa complexes. In the pathological conditions studied here, regulation of IGF-I bioavailability by limited proteolysis of IGFBP-3 contributes toward an appropriate adaptation to insulin deficiency and/or resistance but not to disturbances of GH secretion.     

Effect of octreotide on circulating IGF-I chromatographic profile: evidence for an inhibitory action on the formation of the 150-kDa ternary complex

OBJECTIVE The increasing use In clinical practice of octreotide (a somatostatin analogue which inhibits the secretion of GH and other peptide hormones) led us to study the effects of this treatment on GH, Insulin-like growth factors (IGF)-I and II and IGF-binding protein (IGFBP)-3, as well as on circulating IGFBP complexes in acromegalic patients. DESIGN The circulating concentrations of GH, IGF-I, IGF-II and IGFBP-3 were measured In acromegaiic patients before and after 3, 6, 9, and 12 months of treatment with octreotide (group I: n = 5), and compared with those found In a group of patients (group II) treated with bromocriptine (n= 3), cabergoline (n= 7) radiotherapy (n= 3) or surgical therapy (n= 2). In pools of serum obtained from patients treated with octreotide, dopaminergic drugs, surgery and radiation, before and after therapy, immunoreactive IGF-I and IGFBP-3 were also evaluated after Superdex 200 gel filtration in neutral conditions. RESULTS Before treatment, the concentration of IGF-I and IGFBP-3 were above the normal range in all patients, while IGF-II levels were slightly reduced. After treatment with octreotide, IGF-I (P= 0·004), IGF-II (P= 0·02) and IGFBP-3 (P<0·001) were significantly reduced as compared to basal levels. In subjects of group II, only IGF-I concentration was significantly reduced by the treatment (P= 0.02), and a negative correlation between IGF-I and IGF-II concentrations was found (r=?0·58, P < 0·0001). After gel filtration immunoreactive IGF-I and IGFBP-3 were found in the 150-kDa mol.wt. region in serum obtained from untreated patients and from treated patients of group II, while in the serum of octreotide-treated patients the IGF-I and IGFBP-3 peaks were shifted to the 60-kDa mol.wt. region, thus suggesting that the acid-lablle subunit of the 150-kDa complex was drastically reduced. Since the GH concentrations in groups I and II were similar (M ± SEM; 13·8 ± 7·4 and 21·2±10·6mu/l respectively), the marked reduction in acid-labile submit in the octreotide treated patients can be explained by a direct Inhibitory effect of somatostatin on the subunit. CONCLUSIONS Octreotide exerts an Inhibitory effect not only on IGF-I but also on IGF-II. The reduced formation of the 150-kDa complex probably causes an increased metabolic clearance rate of IGF peptides which can account for the reduced concentration of both IGFs after treatment with octreotide.     

Inverse correlation between insulin-like growth factor binding protein-I and insulin in patients with acromegaly during treatment with the somatostatin analogue octreotide

OBJECTIVE Previous reports have shown an inverse relation between IGFBP-1 and Insulin levels In healthy men, patients with insulin dependent diabetes mellitus, and insulinoma. We have investigated whether this inverse relation also exists in acromegaly, before and during treatment with octreotide, and whether changes in IGFBP-1 levels relate to OH and IGF-I levels. DESIGN We studied short-term treatment with octreotide in a double-blind placebo-controlled 14-day clinical trial. PATIENTS Eighteen patients with acromegaly were studied. MEASUREMENTS Plasma GH and serum IGFBP-1 levels were measured at hourly intervals from 0700 to 1800h before randomization (day 0) and on days 4, 6, 8,14 and 20. Serum insulin was determined at 0700, 0800 and 0900 h, and serum IGF-I at 0700 h. RESULTS Octreotide increased the daily mean IGFBP-1 level by 43% on day 8 and by 35% on day 14. The IGFBP-1 levels during octreotide were significantly higher (P < 0·05) compared to placebo, 29·9 ± 3·9 vs 19·9 ± 1·7 μg/l (mean ± SEM) on day 8, and 28·3 ± 3·2 vs 19·.9 ± 1·6 μg/l on day 14. Octreotide treatment significantly suppressed the insulin levels on all observation days by 40–48% compared to placebo. There was a significant inverse correlation between IGFBP-1 levels and insulin levels, both before treatment and on the last day of treatment (r= 0·79, P= 0·04; r=?0·90, P= 0·02, respectively). GH and IGF-I were significantly decreased in the octreotide group compared to the placebo group during the entire treatment period. The mean of age related standard deviation scores of IGF-I In the octreotide group decreased from a pretreatment value of 6·47 ± 0·74 to 3·60 ± 1·20 on day 14. There was no significant correlation between IGFBP-1 levels and levels of GH and IGF-I, either before or during treatment. CONCLUSIONS Octreotide treatment, in addition to reducing GH, IGF-I and insulin levels, is associated with an Increase in IGFBP-1 concentrations in patients with acromegaly, and it is suggested that the rise in serum IGFBP-1 Is a consequence of the decrease In insulin secretion.