The insulin-like growth factor-I/binding protein axis: physiology, pathophysiology and therapeutic manipulation

Glucocorticoid supplementation during ovarian stimulation for IVF or ICSI

BACKGROUND

Ovarian response to stimulation during in-vitro fertilisation (IVF) and intra-cytoplasmic sperm injection (ICSI) plays an important role in determining live birth rates. Adjuvant treatments during ovarian stimulation that have different modes of action have been used to improve ovarian response to stimulation and outcome of IVF. Glucocorticoids (GCs) are a class of steroid hormones that have been used either alone or in combination with other stimulatory regimens in order to improve folliculogenesis and pregnancy rates. However, considerable uncertainty remains over whether administration of glucocorticoid during ovarian stimulation until oocyte recovery is superior to no glucocorticoid in improving live birth rates in women undergoing IVF/ICSI.

OBJECTIVES

To determine the safety and effectiveness of systemic glucocorticoids during ovarian stimulation for IVF and ICSI cycles.

SEARCH METHODS

We searched the Cochrane Gynaecology and Fertility Group Specialised Register, the Cochrane Central Register of Studies Online (CRSO), MEDLINE, Embase, CINAHL and PsycINFO from inception to 10 October 2016. We handsearched reference lists of articles, trial registers and relevant conference proceedings and contacted researchers in the field.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) comparing adjuvant treatment with systemic glucocorticoids during ovarian stimulation for IVF or ICSI cycles versus no adjuvant treatment.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected studies, assessed risk of bias and extracted the data. Our primary outcome was live birth. Secondary outcomes included clinical pregnancy, multiple pregnancy, miscarriage, ovarian hyperstimulation syndrome (OHSS) and side-effects. We calculated odds ratios (ORs) with 95% confidence intervals (CIs) and pooled the data using a fixed-effect model. The quality of the evidence was assessed using GRADE methods.

MAIN RESULTS

Four RCTs were included in the review (416 women). The trials compared glucocorticoid supplementation during IVF stimulation versus placebo. Two of the studies had data in a form that we could not enter into analysis, so results include data from only two trials (310) women. For the outcome of live birth, data were available for only 212 women, as the larger study had data available from only one study centre.One of the studies gave inadequate description of randomisation methods, but the other was at low risk of bias in all domains. The evidence was rated as low or very low quality for all outcomes, mainly due to imprecision, with low sample sizes and few events.There was insufficient evidence to determine whether there was any difference between the groups in live birth rate (OR 1.08, 95% CI 0.45 to 2.58; 2 RCTs, n = 212, I2 = 0%, low-quality evidence). Our findings suggest that if the chance of live birth with placebo is assumed to be 15%, the chance following supplementation would be between 7% and 31%. There was no conclusive evidence of a difference in the clinical pregnancy rate (OR 1.69, 95% CI 0.98 to 2.90; 2 RCTs, n = 310, I2 = 0%, low-quality evidence).The evidence suggests that if the chance of clinical pregnancy with placebo is assumed to be 24%, the chance following treatment with glucocorticoid supplementation would be between 23% and 47%. There was also insufficient evidence to determine whether there was any difference between the groups in multiple-pregnancy rate (OR 3.32 , 95% CI 0.12 to 91.60; 1 RCT , n = 20, very low-quality evidence) or miscarriage rate (OR 1.00, 95% CI 0.05 to 18.57; 1 RCT, n = 20, very low-quality evidence). Neither of the studies reported OHSS or side-effects.

AUTHORS' CONCLUSIONS

The safety and effectiveness of glucocorticoid administration in women undergoing controlled ovarian hyperstimulation for IVF/ICSI cycles (until the day of oocyte retrieval) is unclear due to the small number of studies and low event rates. Whilst glucocorticoids possible increase the clinical pregnancy rate, there may be little or no impact on live birth rate. More research is needed.

Developmental response to hypoxia

Molecular mechanisms underlying fetal growth restriction due to placental insufficiency and in utero hypoxia are not well understood. In the current study, time-dependent (3 h-11 days) changes in fetal tissue gene expression in a rat model of in utero hypoxia compared with normoxic controls were investigated as an initial approach to understand molecular events underlying fetal development in response to hypoxia. Under hypoxic conditions, litter size was reduced and IGFBP-1 was up-regulated in maternal serum and in fetal liver and heart. Tissue-specific, distinct regulatory patterns of gene expression were observed under acute vs. chronic hypoxic conditions. Induction of glycolytic enzymes was an early event in response to hypoxia during organ development; consistently, tissue-specific induction of calcium homeostasis-related genes and suppression of growth-related genes were observed, suggesting mechanisms underlying hypoxia-related fetal growth restriction. Furthermore, induction of inflammation-related genes in placentas exposed to long-term hypoxia (11 days) suggests a mechanism for placental dysfunction and impaired pregnancy outcome accompanying in utero hypoxia.

The insulin-like growth axis in patients with autoimmune thyrotoxicosis: effect of antithyroid drug treatment

OBJECTIVE

Hyperthyroidism is associated with altered growth hormone (GH) secretion. Many patients with thyroid dysfunction experience several poorly described complications such as symptoms and signs also seen in patients with growth hormone deficiency (GHD). We have therefore prospectively evaluated a possible relationship between the thyroid function, body composition, leptin levels and insulin-like growth factor (IGF) related peptides in patients with Graves' disease. DESIGN, PATIENTS, AND MEASUREMENTS: In a prospective group of 24 fasting female patients with Graves' disease (mean age (CI 95%): 40 years (33-47)), we measured serum thyroxine, triiodothyronine, thyrotropine (TSH), TSH receptor antibodies, anti-thyroid peroxidase, leptin, body composition, body mass index (BMI) and IGF-related peptides at diagnosis and after 12 months of treatment with thiamazol (ATD).

RESULTS

In thyrotoxic patients IGF-I plus IGF-II correlated positively with IGFBP-3 at baseline (r = 0.90, p < 0.1 x 10(16)) and after 12 months follow-up (r = 0.87, p < 0.1 x 10(-16)). In the thyrotoxic state total IGF-I, IGF-II, IGF binding protein 3 (IGFBP-3) and acid-labile subunit (ALS) but not free IGF-I decreased significantly from 223 microg/L (189-260) (mean (CI 95%), 877 microg/L (801-953), 4165 microg/L (3772-4577) and 22 mg/L (18-26)) to 198 microg/L (172-226), 788 microg/L (711-865), 3431 microg/L (3135-3741) and 19 mg/L (16-26) (p <0.006), respectively, after 12 months of ATD despite an increase in BMI from 22 (21-23) to 23 kg/m(2) (22-25) (p < 0.0004) but no significant changes in leptin.

CONCLUSIONS

The complex IGF systems seemed intact in thyrotoxic patients but change in body composition and the regulation of leptin and insulin secretion during treatment of autoimmune thyroid disease influence IGF-related peptides leaving the patient in a state somewhat similar to partial GHD, but the mechanism behind these alterations remains unclear.

Frailty and the biochemical effects of recombinant human growth hormone in women after surgery for hip fracture

We report a randomised double blind controlled trial investigating the short-term biochemical and adverse clinical responses to recombinant human growth hormone (r-hGH) after surgery for hip fracture. Hip fractures are common, dangerous and expensive, typically affecting frail women with osteoporosis and reduced muscle mass and strength, factors also associated with poor clinical outcomes. Growth hormone therapy increases IGF-I levels, promotes anabolism and increases muscle strength in well older people and selected patient groups and therefore has therapeutic potential to assist recovery of frail patients.Thirty-one women, mean age 86 years, received 14 nightly subcutaneous injections of r-hGH 0.05 mg/kg/day (high dose) or 0.025 mg/kg/day (low dose), or placebo from the 4th post-operative day. There were several serious adverse clinical events but no excess number of adverse events in the r-hGH treatment groups. The r-hGH treatment groups had similar serum IGF-I and IGFBP-3 responses, both significantly different from placebo. The large inter-individual variation of IGF-I responses were inversely correlated with pre-treatment indicators of frailty (body composition and functional abilities).

The effects of acute administration of ethanol on jejunal protein synthesis and circulating insulin-like growth factor (IGF)-1 and IGF binding proteins in ad libitum fed and nutritionally restricted rats

The effects of acute ethanol administration (75 mmol/kg body weight) to male Wistar rats (either ad libitum fed or nutritionally restricted) on fractional rates of protein synthesis in the jejunum was assessed together with the changes in IGF-1 and IGF binding protein concentrations. Acute administration of ethanol resulted in significant decreases in fractional rates of protein synthesis in the whole jejunum and jejunal seromuscular layers of both the ad libitum fed and nutritionally restricted animals. The synthesis rate per unit RNA (k(RNA), mg protein/day/mg RNA) in whole jejunum was reduced by 29% and 24% in the nutritionally restricted and ad libitum fed animals, respectively. Mean IGF-1 levels were lower in the nutritionally restricted group (871 +/- 36.9 microg/l) than the ad libitum animals (960 +/- 27.3 microg/l) although this did not reach significance. In contrast, administration of alcohol to both groups markedly reduced circulating IGF-1 levels (ad libitum: 518 +/- 19.8 microg/l, nutritionally restricted: 417 +/- 33.7 microg/l). Furthermore, ethanol treatment resulted in a three-fold increase in the intensity of a 30 kDa IGF binding protein (IGFBP) in the ad libitum fed animals and a fourfold increase in both 30 and 32 kDa IGFBP bands in the nutritionally restricted group as visualized by Western ligand blotting. Decreases in levels of IGF-1 allied with increased circulating small molecular weight IGFBPs may contribute to the reduction in fractional rates of protein synthesis in the gastrointestinal tract of ethanol-treated rats.

The influence of glucose-insulin-potassium (GIK) on the GH/IGF-1/IGFBP-1 axis during elective coronary artery bypass surgery

OBJECTIVES

To investigate the influence of glucose-insulin-potassium (GIK) on the growth hormone/insulin-like growth factor-1 axis.

DESIGN

Randomized clinical study.

SETTING

University hospital.

PARTICIPANTS

Twenty patients, without metabolic disorders, admitted for elective aortocoronary bypass surgery.

INTERVENTIONS

GIK therapy. Measurements and main results Blood samples were taken repeatedly during the day of surgery. Ejection fraction (EF) was determined by transesophageal echocardiography before and at the end of surgery. Blood samples were taken on the first postoperative day and at discharge (8 am and 8 pm). During coronary artery bypass graft (CABG) surgery, a rapid decrease (44%) in total IGF-1 occurred in both groups. Directly after cessation of extracorporeal circulation, there was a prompt rise in IGFBP-1. The mean peak value in the control group was more than 3 times higher than in the GIK group. GH secretion was stimulated by surgery in both groups and was enhanced by GIK. B-glucose was significantly higher in the control group during surgery. EF ( approximately 55% at baseline) was unchanged in both groups. Postoperatively, there were no differences between the groups (all parameters). At discharge, IGFBP-1 was unchanged, but insulin was elevated compared with preoperative levels. This was seen in both groups, reflecting a hepatic insulin resistance. Conclusions The authors conclude that GIK blunts the rise of IGFBP-1 and thereby increases the bioavailability of IGF-1. GIK also seems to speed up the return of IGF-1 to baseline. Both mechanisms could be of importance to catabolic high-risk patients with low IGF-1. Hence, GIK has favorable effects on the GH/IGF-1 axis during CABG surgery.

A longitudinal analysis of maternal serum insulin-like growth factor I (IGF-I) and total and nonphosphorylated IGF-binding protein-1 in human pregnancies complicated by intrauterine growth restriction

In cord blood and late gestation maternal serum, IGF-I is positively correlated with birth weight, whereas IGF-binding protein-1 (IGFBP-1) is inversely correlated with birth weight. Our goal was to determine whether maternal serum or amniotic fluid concentrations of IGF-I, IGFBP-1, or nonphosphorylated IGFBP-1 (npIGFBP-1) in early gestation predict later fetal growth abnormalities. Maternal serum was collected prospectively across gestation (5-40 wk) from 749 pregnant subjects. Amniotic fluid was collected after amniocentesis during wk 15-26 from 207 subjects. We compared median serum concentrations of IGF-I, IGFBP-1, and npIGFBP-1 in 38 subjects who delivered growth-restricted infants with the control group of 236 subjects with normal weight infants for each gestational age grouping, wk 5-12, 13-23, and 24-34. In the control group median IGF-I concentrations were 14.8, 11, and 15.6 nmol/liter for wk 5-12, 13-23, and 24-34, respectively, compared with 13.7, 14.3, and 10.6 nmol/liter in the intrauterine growth restriction (IUGR) group. Median IGFBP-1 concentrations were 8.5, 30.4, and 24.4 nmol/liter, respectively, in controls, compared with 11.4, 28.6, and 25.5 nmol/liter in the IUGR group. Median npIGFBP-1 concentrations were 6.9, 22, and 17.4 nmol/liter, respectively, in controls, compared with 5.0, 32.1, and 24.2 nmol/liter in the IUGR group. In the control group the median amniotic fluid IGFBP-1 level was 13,160 nmol/liter, and the median npIGFBP-1 level was 15,970 nmol/liter; in the IUGR group these levels were 13,440 and 18,440 nmol/liter, respectively. No clinically useful differences were found between the IUGR and control groups. Our results do not support the use of maternal serum IGF-I or IGFBP-1 or amniotic fluid IGFBP-1 or npIGFBP-1 early in gestation to predict later fetal growth restriction.

The acid-labile subunit of the ternary insulin-like growth factor complex in cirrhosis: relation to liver dysfunction

BACKGROUND/AIMS

In the circulation, insulin-like growth factor-I (IGF-I) is bound in a trimeric complex of 150 kDa with IGF binding protein-3 (IGFBP-3) and the acid-labile subunit (ALS). Whereas circulating IGF-I and IGFBP-3 are reported to be low in patients with chronic liver failure, the level of ALS has not been described in relation to hepatic dysfunction. The aim of the present study was therefore to measure circulating and hepatic venous concentrations of ALS in relation to hepatic function and the IGF axis.

METHODS

Twenty-five patients with cirrhosis (Child class A/B/C:5/10/10) and 30 controls with normal liver function were studied. During a haemodynamic investigation, blood samples were collected from the hepatic vein and femoral artery, and the plasma concentrations of ALS, IGF-I and IGFBP-3 were determined.

RESULTS

Hepatic venous and arterial concentrations of ALS were significantly decreased in the cirrhotic patients compared with the controls (-69% and -68%, respectively, both p<0.001). IGF-I and IGFBP-3 were similarly decreased in the cirrhotic patients (-51%,p<0.001). A significant hepatic extraction of ALS was found in the controls (6%, p<0.01) and in the cirrhotic patients (8%, p=0.08). ALS correlated significantly with indicators of liver dysfunction, including the Child-Turcotte score (r=-0.69, p<0.0001), IGF-I (r=0.82, p<0.0001) and IGFBP-3 (r=0.74, p<0.0001).

CONCLUSIONS

Circulating and hepatic venous ALS are decreased in patients with cirrhosis with significant relations to liver dysfunction and other components of the IGF complex. A small hepatic extraction was found in controls, which suggests extrahepatic production of ALS. Future studies should focus on organ-specific removal of ALS.

A longitudinal study of bone gain in pubertal girls: anthropometric and biochemical correlates

The aim of this longitudinal study was to investigate the factors associated with bone mineral acquisition in pubertal girls. Subjects were 37 healthy, Caucasian girls aged 12.1 years (SD 0.3). Measurements were made at 6-month intervals over a period of 18 months and included total body bone mineral content (TBBMC), total body bone mineral density (TBBMD), lean mass, and fat mass by dual-energy X-ray absorptiometry, anthropometry, lifestyle factors, four biochemical markers of bone turnover, hormonal status, and fractional calcium absorption. In multiple regression analysis, correlates of relative gain in TBBMC were gain in lean mass (p < 0.001) and estradiol (p = 0.008). For TBBMD, correlates were gain in lean (p < 0.001) and fat mass (p = 0.003), estradiol (p < 0.001), dietary energy intake (p = 0.003), and parathyroid hormone (p = 0.023). Statural growth and gain in bone mass were unrelated; both height velocity and bone turnover peaked approximately 20 months prior to menarche, whereas gain in bone mass peaked at menarche. Bone turnover markers correlated with height velocity (0.40 < r < 0.62), but not with bone gain. Estradiol was independently and negatively associated with all markers of bone turnover (-0.67 < r < -0.80). We conclude that estradiol is an important determinant of bone mineral gain in pubertal girls and is probably responsible for the reduction in bone turnover in late puberty; lean mass was the body composition parameter most closely associated with bone gain; height gain and bone gain are dissociated during the period of rapid growth at puberty; and bone turnover markers are modestly related to height gain, but are not predictive of bone gain.

Selective increase in cardiac IGF-1 in a rat model of ventricular hypertrophy

There is evidence that insulin-like growth factor-1 (IGF-1) plays a role in the development of left ventricular hypertrophy, but it is uncertain whether cardiac IGF-1 changes before or after hypertension is established, and whether circulating IGF-1 are involved in cardiac hypertrophy. We have investigated changes in circulating and left ventricular IGF-1 and in the expression of the IGF-1 gene in the left ventricles of rats during the development of hypertensive left ventricular hypertrophy (Goldblatt model; 2 kidney-1 clamped). Our results show that the left ventricular contents of IGF-1 and its mRNA were increased at one and four weeks of hypertension and hypertrophy, and that both returned to control values after nine weeks. These changes were unrelated to the seric concentration of IGF-1 in the blood. These results show that local rather than circulating IGF-1 levels contributed to the development of renovascular hypertensive left ventricular hypertrophy.

Growth hormone secretion in the elderly: ageing and the somatopause

The syndrome associated with lack of growth hormone (GH) in adults can be reversed by treatment with recombinant human GH (rhGH) with apparently beneficial clinical effects. This syndrome is strikingly similar to the characteristics of normal older adults which are known as the somatopause. GH secretion and insulin-like growth factor I levels are reduced in healthy older people and it has been suggested that the somatopause is an age-related GH deficiency state. This review describes the physiological control of GH secretion in adults and seeks an explanation for the age-related decline, considering the impact of other factors such as nutrition and mobility, and particularly whether exercise offers a physiological approach to changing both the GH decline and the somatopause. The benefits and side-effects of treatment with rhGH for normal older people or older patients facing catabolic stresses are reviewed together with alternative approaches to stimulate GH such as GH-releasing hormone and the new pharmaceutical GH secretagogues.

Changes in growth hormone, insulin, insulinlike growth factors (IGFs), and IGF-binding protein-1 in chronic fatigue syndrome

Chronic fatigue syndrome (CFS) is characterized by severe physical and mental fatigue of central origin. Similar clinical features may occur in disorders of the hypothalamopituitary axis. The aim of the study was to determine whether patients with CFS have abnormalities of the growth hormone/insulinlike growth factor (GH-IGF) axis basally or following hypothalamic stimulation with insulin-induced hypoglycemia. We compared levels of GH, IGF-I, IGF-II, IGF-binding protein-1 (IGFBP-1), insulin, and C-peptide in nondepressed CFS patients and normal controls. We found attenuated basal levels of IGF-I (214 +/- 17 vs. 263.4 +/- 13.4 micrograms/L, p = .036) and IGF-II (420 +/- 19.8 vs. 536 +/- 24.3 micrograms/L, p = .02) in CFS patients and a reduced GH response to hypoglycemia (peak GH; 41.9 +/- 11.5 vs. 106.0 +/- 25.6 mU/L, p = .017). Insulin levels were higher (7.6 +/- 1.0 vs. 4.3 +/- 0.8 mU/L, p = .02) and IGFBP-1 levels were lower (19.7 +/- 4.6 vs. 43.2 +/- 2.7 mg/L, p = .004) in CFS patients compared with controls. This study provides preliminary data abnormalities of the GH-IGF axis in CFS. It is not apparent whether these changes are components of a primary pathological process or are acquired secondary to behavioral aspects of CFS such as reduced physical activity.

Growth characteristics in laboratory animals fed zinc-deficient, copper-deficient, of histidine-supplemented diets

The effects of growth in male Wistar rats and female Swiss Random mice were studied during dietary zinc (Zn) deficiency, copper (Cu) deficiency, and during the feeding of a histidine (His) supplement Growth was analyzed by comparing the characteristics of the decreasing exponential growth curve plotted for the experimental period. When the animals were pair-fed the experimental diets, the growth pattern in the animals remained unaltered. The growth rate decreased during Zn deficiency by a factor of 0.64 over a period of 10 d (male young adult rats) and by a factor of 0.76 over a period of 28 d (female weaning mice). On the other hand, a supplement of His increased the growth rate by a factor of 1.11 (in the mice). The effect of Cu deficiency on the growth rate was not statistically significant (in the rats). However, Cu deficiency causes effects in the Zn status that may over-compensate minor growth retardation during Cu deficiency. The effect of the His supplement is explained by its having an effect on the Zn-absorption (His enhancing Zn transport over the gut) and by a stimulating effect of this amino acid on the thickness of the growth plate in bone.

Is diabetes mellitus a risk factor for ovarian cancer? A case-control study in Utah and Washington (United States)

Insulin resistance characterizes non-insulin dependent diabetes (NIDDM). Insulin resistance may coexist in clinical syndromes with hyperestrogenism and hyperandrogenism, suggesting that the ovary may be sensitive to effects of insulin. In addition, insulin-like growth factor-I receptors, which are capable of binding insulin, have been identified in ovarian cancer tissue and are proposed to regulate cell growth. We evaluated the association between a history of diabetes mellitus and ovarian cancer in a case-control study in seven counties in Washington and in Utah (United States) during the years 1975-87. Cases included women newly diagnosed with ovarian cancer over a five-year period who were identified through population-based cancer reporting. Controls similar to cases with regard to age and county of residence were identified via household surveys or random digit dialing. The study included 595 cases and 1,587 controls. Twenty-seven cases (4.5 percent) and 72 controls (4.5 percent) reported a history of diabetes. Logistic regression analysis of the association between diabetes and ovarian cancer controlling for age, body mass index, and race resulted in an odds ratio (OR) of 0.9 (95 percent confidence interval [CI] = 0.6-1.5). The OR was not changed with further controlling for prior oral contraceptive use or prior pregnancy. None of the 20 women with nonepithelial tumors (15 of which were stromal tumors) had a history of diabetes (upper CI = 4.0). These results, together with findings of two earlier cohort studies, do not support the hypothesis that diabetes is a risk factor for epithelial ovarian cancer.

Lack of evidence for a circadian rhythm of IGFBP-1 in the mother and fetus during labour

OBJECTIVE

To determine whether the circadian rhythm of circulating levels of insulin-like growth factor binding protein-1 (IGFBP-1) is evident at the time of delivery.

DESIGN

Prospective observational study in six pregnant women and cross-sectional study in 65 women at the time of delivery.

SUBJECTS

Six pregnant women sampled over a period of 24 hours, 23 women sampled at the time of elective caesarean section, and 42 women sampled at the time of vaginal delivery.

RESULTS

In the women sampled serially over a 24 hour period there was an obvious circadian rhythm of IGFBP-1 with a peak between 01.00 and 09.00 hours. In the women sampled at the time of delivery there was no evidence for any relationship between the time of delivery and maternal or fetal levels of IGFBP-1.

CONCLUSIONS

The circadian rhythm of IGFBP-1 is not observed in women in labour. Therefore, the time of day is not an important confounding variable in studies on IGFBP-1 levels at the time of normal delivery.

IGFBP-3 is a poor parameter for assessment of clinical activity in acromegaly

OBJECTIVE

Elevated serum IGF-I and IGF binding protein-3 (IGFBP-3) levels have been found in patients with active acromegaly. We have studied the relative diagnostic merits of measurements of IGFBP-3 compared with IGF-I as a parameter of disease activity in these patients.

DESIGN/PATIENTS

Thirty untreated patients with acromegaly were compared with 30 healthy adults.

MEASUREMENTS

Twenty-four-hour sampling for serum GH in patients with acromegaly, serum IGF-I and IGFBP-3.

RESULTS

Mean IGF-I levels were 22.0 nmol/l (range 6.5-38.4) in the healthy adults and 118.7 nmol/l (range 67.7-206.0) in patients with acromegaly. Mean IGFBP-3 levels were 3.5 mg/l (range 2.1-4.8) in controls and 5.4 mg/l (range 4.2-6.6) in patients with acromegaly. Mean IGF-I/IGFBP-3 ratios were 6.5 nmol/mg (range 1.9-14.5) in the healthy adults and 22.0 nmol/mg (range 14.3-32.7) in patients with acromegaly. There was a considerable overlap for IGFBP-3 levels but not for IGF-I levels, between normals and acromegalics. The IGF-I/IGFBP-3 ratio also showed overlap between normals and acromegalics. There was a significant correlation between the mean 24-hour GH and IGFBP-3 levels (P = 0.036) and between the IGF-I and IGFBP-3 levels (P < 0.002) in acromegaly. In patients with acromegaly, the IGFBP-3 levels showed a decrement, but the IGF-I/IGFBP-3 ratio did not change significantly with age.

CONCLUSIONS

IGFBP-2 has no additional discriminatory value over IGF-1 measurements for the assessment of clinical activity in acromegaly. In acromegaly, IGFBP-3 decreases with increasing age. In acromegaly, IGFBP-3 levels significantly correlate with mean 24-hour GH levels and IGF-I levels.

Size at birth and plasma insulin-like growth factor-1 concentrations

OBJECTIVE

To test the hypothesis that reduced fetal growth leads to altered plasma insulin-like growth factor-1 (IGF-1) concentrations in childhood.

DESIGN

A follow up study of 4 year old children whose birth weights were recorded, and of 7 year old children whose weight, length, head circumference, and placental weight were measured at birth.

SETTING

Pune, India, and Salisbury, England.

SUBJECTS

200 children born during October 1987 to April 1989 in the King Edward Memorial Hospital, Pune, weighing over 2.0 kg at birth and not requiring special care, and 244 children born during July 1984 to February 1985 in the Salisbury Health District and still living there.

MAIN OUTCOME MEASURE

Plasma IGF-1 concentrations.

RESULTS

In both groups of children, and consistent with findings in other studies, plasma IGF-1 concentrations were higher in taller and heavier children, and higher in girls than boys. Allowing for sex and current size, concentrations were inversely related to birth weight (Pune p = 0.002; Salisbury p = 0.003). Thus at any level of weight or height, children of lower birth weight had higher IGF-1 concentrations. The highest concentrations were in children who were below average birth weight and above average weight or height when studied. Systolic blood pressures were higher in children with higher IGF-1 concentrations (Pune p = 0.01; Salisbury p = 0.04).

CONCLUSIONS

Children of lower birth weight develop higher circulating concentrations of IGF-1 than expected for their height and weight. This is consistent with the hypothesis that under-nutrition in utero leads to reprogramming of the IGF-1 axis. The increase of plasma IGF-1 concentrations in low birthweight children may also be linked to postnatal catch-up growth. High IGF-1 concentrations may be one of the mechanisms linking reduced fetal growth and high blood pressure in later life.

Effects on glucose tolerance, insulin secretion, insulin-like growth factor 1 and its binding protein, IGFBP-1, in a randomized controlled diet and exercise study in healthy, middle-aged men

OBJECTIVES

To study the effects of advice on diet, exercise and their combination on oral glucose tolerance (OGTT), insulin secretion, insulin-like growth factor-1 (IGF-1) and its binding protein, IGFBP-1.

DESIGN

A 6-month, randomized, controlled intervention study.

SETTING

Primary health care centres in Sollentuna, Stockholm and the Department of Medicine, Karolinska Hospital, Stockholm, Sweden.

SUBJECTS

One hundred and fifty-seven normoglycaemic healthy men, mean age 46 years, range 35-60 years, with slightly to moderately raised cardiovascular risk factors.

INTERVENTIONS

Advice on diet (D, n = 40), exercise (E, n = 39) a combination of both (DE, n = 39) and a control group (C, n = 39).

MAIN OUTCOME MEASURES

An OGTT, insulin secretion, IGF-1 and its binding protein, IGFBP-1.

RESULTS

The number of pathological OGTTs in the intervention groups decreased from 42/118 to 33/118 whilst the number in the control group did not change. Fasting insulin levels decreased in groups E and DE from 8.8-7.4 mU L-1 (P < 0.01) and from 8.3-6.7 mU L-1 (P < 0.01), respectively. Accordingly, the insulin area under the curve decreased from 5278 to 4828 (P < 0.05) in group E, and from 5482 to 4809 (P < 0.01) in group DE. IGF-1 only increased in group D. The most prominent changes were noted for IGFBP-1, which increased in all three intervention groups and to the highest degree in group DE (from 33.7-42.6 micrograms L-1, P < 0.001).

CONCLUSIONS

A combination of increased exercise and improved diet, as well as increased exercise alone, favourably affect glucose and insulin homeostasis in middle-aged men with moderately elevated cardiovascular risk factors. The most marked changes were noted for IGFBP-1, possibly suggesting a decreased insulin secretion and an enhanced insulin sensitivity.

Hormonal regulation of serum lipoprotein(a) levels. Contrasting effects of growth hormone and insulin-like growth factor-I

In response to treatment with growth hormone, serum levels of lipoprotein(a) increase, while those of LDL cholesterol decrease. To establish if increased levels of insulin-like growth factor-I may be of importance for these changes, we analyzed serum lipoprotein concentrations in 11 male patients with idiopathic osteoporosis who were treated with growth hormone (2 IU.m-2.d-1) or insulin-like growth factor-I (80 micrograms.kg-1.d-1) in a randomized, double-blind, cross-over study. LDL cholesterol was reduced by 0.7 mmol/L (P < .01) during growth hormone treatment but was not affected when the same patients received insulin-like growth factor-I. In contrast, mean lipoprotein(a) levels increased from 519 to 571 mg/L (P < .03) in response to growth hormone but were reduced from 538 to 478 mg/L (P < .04) during treatment with insulin-like growth factor-I. These results indicate that growth hormone exerts its effects on lipoprotein metabolism independent of insulin-like growth factor-I. Furthermore, the results suggest that treatment with insulin-like growth factor-I may reduce lipoprotein(a) levels.

Co-administration of insulin-like growth factor (IGF)-I and IGF-binding protein-1 stimulates wound healing in animal models

The stimulatory effect of recombinant human insulin-like growth factor-I (rhIGF-I) and recombinant human insulin-like growth-factor-binding protein-1 (rhIGFBP-1) on wound healing was assessed using diabetic db/db mice and normal rabbits. Full-thickness wounds of 6 mm diameter were prepared on the backs of diabetic C57BL/KsJ db/db mice and on the inner sides of normal rabbit ears. Various concentrations of rhIGF-I and/or rhIGFBP-1 were applied locally to the open wounds of db/db mice once daily for 5 d and to the covered wounds of normal rabbits once after wounding. Sections of the wounds were evaluated histologically on the seventh or eighth day by measuring re-epithelialization (%), area of granulation tissue (mm2), and capillary numbers. Wound repair was accelerated by each of the treatments in descending order of rhIGF-I plus rhIGFBP-1, rhIGF-I, rhIGFBP-1, and vehicle alone. In db/db mice, the combination of 50 micrograms rhIGF-I and 165 micrograms rhIGFBP-1 (equimolar ratio) significantly stimulated granulation tissue formation (p < 0.01) and capillary numbers (p < 0.05). Doses of rhIGFBP-1 greater than 16.5 micrograms were required for significant acceleration of the healing stimulated by 50 micrograms of rhIGF-I. In normal rabbits, co-administration of 10 micrograms rhIGF-I and 33 micrograms rhIGFBP-1 (equimolar ratio) significantly stimulated all three wound-healing parameters (p < 0.01), with such stimulation being much greater than that induced by rhIGF-I alone. Interestingly, rhIGFBP-1 alone showed a mild stimulatory activity on wound healing in both models despite its lack of mitogenic activity in vitro. These results demonstrate that rhIGFBP-1 enhances the stimulatory activity of rhIGF-I on wound healing and suggest the clinical utility of the co-administration of rhIGF-I and rhIGFBP-1 for wound repair.

Dietary subacute zinc deficiency and potassium metabolism

In a controlled animal experiment the effects of dietary subacute Zn deficiency on growth, Zn concentration, and tissue 42-K distribution were studied. Growth retardation caused lower body weight because both skeletal and heart muscle showed a reduction in cell mass. Zn concentrations were reduced in most tissues, however, they remained unaltered in heart muscle. 42-K activity increased in skeletal muscle and pancreas. We hypothesize the latter reflects the organs rate of metabolism, inducing the exocrine pancreas to increase Zn absorption; in skeletal muscle it may induce also alterations in cell potentiation, causing restless behavior. As suggested by the calculated specific K activity (Bq/mol), the K uptake was highest in liver and bone, high in pancreas and skeletal muscle and low in heart muscle. The latter suggests K retention in heart muscle. Specific activity in plasma and jejunum remained unaltered: K status and absorption seem unaffected. Zn deficiency causes different 42-K activities in the various tissues, that respond by alterations in K metabolism without the induction of K deficiency.

The pathophysiology of the insulin-like growth factor axis in fetal growth failure: a basis for programming by undernutrition?

Recent evidence suggests that a number of adulthood conditions, including non-insulin dependent diabetes mellitus (NIDDM) and lipid and cardiovascular abnormalities are associated with intra-uterine growth retardation (IUGR). It is possible that this arises from programming of endocrine axes during development as a result of an adverse intra-uterine environment. Insulin-like growth factors (IGFs) are mitogenic polypeptides which stimulate cellular proliferation and differentiation and are important in human fetal development. The functions of IGFs are modulated by specific high affinity binding proteins (IGFBPs). IGFBP-1 is antagonistic to the insulin-like and growth promoting effects of IGF-I, and IGFBP-3 holds IGFs in the circulation by associating with IGFs and an acid labile subunit to form a ternary complex. Using specific radioimmunoassays and fetal serum obtained during diagnostic cordocentesis we have investigated the role of the IGF/IGFBP axis in human fetal development. In a study of 130 singleton pregnancies we have examined levels of immunoreactive IGFs and IGFBPs in normally grown fetuses (AGA), starved small fetuses affected by uteroplacental insufficiency (UPI), and non-starved small fetuses (SGA). IGF-I was significantly lower in the UPI group (n = 14, 7.8 +/- 0.6 micrograms l-1), than in either the SGA group (n = 22, 31.4 +/- 3.5 micrograms l-1, P = 0.0001) or the AGA group (n = 94, 36.3 +/- 1.9 micrograms l-1, P = 0.0001). IGFBP-3 showed similar changes (UPI: 682.6 +/- 50.0 micrograms l-1; SGA: 831.9 +/- 55.5 micrograms l-1; AGA: 847.7 +/- 19.8 micrograms l-1).(ABSTRACT TRUNCATED AT 250 WORDS)

Biochemical markers of bone turnover in girls during puberty

OBJECTIVE

Bone turnover and the rate of bone growth increase dramatically during puberty. A number of new assays for the estimation of bone resorption and formation rates have been developed over recent years, and puberty acts as a convenient model for evaluation of these measurements. The aim of this study was to explore the interrelationships between pubertal development, biochemical markers of bone turnover, insulin-like growth factor I and oestradiol in healthy pubertal girls.

SUBJECTS

Ninety-one healthy girls (ages 11.6-15.5 years) were studied. All subjects were apparently healthy, and were not taking medications known to influence calcium homeostasis. Breast examination was performed to assess pubertal stage according to Tanner. The adult reference range for biochemical markers of bone turnover was obtained from concurrent studies on 42 healthy premenopausal women ranging in age between 20 and 45 years.

DESIGN AND MEASUREMENTS

Blood samples were obtained from subjects between 0800 and 1000 h. Urine samples were collected between 1330 and 1600 h. We measured total and bone specific alkaline phosphatase, osteocalcin, and type I procollagen carboxyterminal propeptide as markers of bone formation. Tartrate resistant acid phosphatase, carboxyterminal pyridinoline cross-linked telopeptide, creatinine corrected urinary deoxypyridinoline, immunoreactive urinary pyridinolines, and urinary galactosyl hydroxylysine were measured as markers of bone resorption.

RESULTS

Bone turnover as reflected by each of the markers was maximal in mid puberty (breast Tanner stages II and III) and decreased towards adult levels in late puberty (P < 0.001). However, the magnitude of the mid-pubertal increase differed between markers. In particular, the pubertal increase in levels of bone specific alkaline phosphatase, osteocalcin and urinary deoxypyridinoline were higher than the increase shown by the other markers. All markers were significantly lower after the menarche. Circulating insulin-like growth factor I and insulin like growth factor binding protein-3 were not important determinants of pubertal changes in bone turnover. In contrast, there was a significant negative correlation between oestradiol and all markers of bone formation and resorption during puberty.

CONCLUSIONS

The greater pubertal increase in levels of bone specific alkaline phosphatase, osteocalcin and urinary deoxypyridinoline suggests that these markers may be relatively more sensitive as indicators of skeletal health during puberty. The differences between markers may reflect differences in the bone specificity of the analytes, or differing mechanisms of production and clearance. The negative correlation between oestradiol and markers of bone resorption and formation suggests that this hormone may be responsible for the reduction in bone turnover in late puberty.