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P Bang

Publications and source records attributed to P Bang.

At least 37 records · Page 2Linked to original sources
PubMed1997

Hypoxia-induced changes in insulin-like growth factors and their binding proteins in pregnant rats.

Pregnancy is associated with important changes in the insulin-like growth factor (IGF)-insulin-like growth factor binding protein (IGFBP) axis, but the importance of these growth factors for fetal growth is not well understood. We have recently established a maternal hypoxia model that results in significant intrauterine growth retardation in the fetus, and characterized the IGF-IGFBP axis in growth-retarded fetuses. To determine if maternal IGFs and their binding proteins are similarly regulated by hypoxia, we examined their expression in 6 hypoxic dams (13% oxygen, days 14-21 of gestation) and 6 control dams (21% oxygen). There was no significant difference in the food intake between the groups. The mean body weight of hypoxic dams, however, was 20% less than that of controls. Of all the organs, the lungs were most affected by hypoxia, weighing 17% more in the hypoxic dams than in the control dams; placental weight was reduced by 10% in the hypoxic dams. Liver and brain weights were not changed significantly by hypoxia. The mean concentration ofimmunoreactive IGF-I was 123 +/- 11 ng/ml in the hypoxic dams and 130 +/- 18 ng/ml in the control dams (nonsignificant). Similarly, there was no significant difference in hepatic IGF-I mRNA levels determined by solution hybridization nuclease-protection assay. An increase in IGFBP-1, IGFBP-2 and IGFBP-4 concentrations, however, could be observed by Western ligand blotting of the sera of hypoxic dams, compared to control dams. As assessed by Northern blot analysis, there was a 2.8-fold increase in IGFBP-1 mRNA expression in the livers of hypoxic dams compared to controls. Hepatic IGFBP-4 expression was also slightly increased (1.25-fold) in the hypoxic dams. No difference in hepatic IGFBP-2 or IGFBP-3 mRNA was found. Our results show parallel patterns in fetal and maternal IGF and IGFBP responses to hypoxia. This suggests that hypoxia may inhibit fetal growth by both directly affecting the fetus and via inhibition of placental growth.

Actins↗
PubMed1997

Human pregnancy serum contains at least two distinct proteolytic activities with the ability to degrade insulin-like growth factor binding protein-3.

The presence of a proteolytic activity in sera from pregnant humans and rodents capable of degrading insulin-like growth factor binding protein-3 (IGFBP-3) has been known for some time. However, the identity of this activity has remained elusive. We have attempted to purify the IGFBP-3 protease activity from pregnant human serum (PHS) using the degradation of 125I-IGFBP-3 as a marker. Following ammonium sulfate precipitation of PHS and further enrichment of active fractions by ion-exchange, protein-A Sepharose, and size-exclusion chromatography, a protease of approximately 70-90 kDa was isolated and subjected to N-terminal analysis. The N-terminal sequence was consistent with plasminogen, a known fibrinolytic enzyme. To further characterize the IGFBP-3 protease activities in both PHS and nonpregnant human serum (NHS), aliquots of serum were first enriched by polyethylene glycol-precipitation and subjected to size-exclusion chromatography. The size-separated fractions were then incubated with 125I-IGFBP-3, and proteolytic activity was measured. PHS contained two separate proteases (>150 kDa and 70-90 kDa), whereas NHS contained only one (70-90 kDa) that had a inhibitor profile similar to plasmin. However, inhibitors of plasmin had no effect on the activity of the >150-kDa protease. Plasminogen activators (PAs) greatly increased the activity of the 70- to 90-kDa protease, but had little effect on the >150-kDa protease activity. Addition of PAs greatly increased the ability of NHS to proteolyze IGFBP-3. In contrast, the ability of plasminogen-depleted plasma to degrade 125I-IGFBP-3 was not affected by the addition of PAs. Both urokinase and tissue-type PA had the ability to proteolyze IGFBP-3 and were, in contrast to the >150-kDa protease activity, inhibited by the specific PA inhibitor D-PHE-PRO-ARG chloromethyl ketone. The present data suggest that sera has the ability to proteolyze IGFBP-3, and that this ability, as demonstrated by NHS, can be regulated by protease inhibitors and PAs. In addition, PHS does indeed contain an unique IGFBP-3 protease activity that is not present in NHS, and its identity is unknown at this time.

Amino Acid Sequence↗
PubMed1995

[Insulin-like growth factors. Future treatment in catabolism?].

Growth is the result of complex interactions between nutrition, stimulating and inhibiting signal substances, and target cell response to these substances. The insulin-like growth factors, IGF-I and IGF-II, are important growth factors throughout life, and function both as endocrine and paracrine hormones. Their anabolic and growth promoting actions are mediated via the IGF-I receptor, present in all cells apart from liver and adipose cells, which contains the homologous insulin receptor. IGF-I expression is regulated both by nutrition and by other hormones such as insulin and growth hormone (GH), though GH regulation of IGF-I first starts after birth when growth becomes GH- dependent. Treatment with recombinant IGF-I has been shown to normalise growth in children with GH receptor deficiency. IGF peptides in serum and other fluids are always associated with binding proteins (IGFBPs). A family of six polypeptides have been characterised. The various IGFBPs have been suggested to function as storage or transport proteins, or modulators of IGF action on target cells. Proteases which cleave IGFBPs are assumed to increase the bioavailability of IGFs. Most of the IGFs in serum are bound to the GH-dependent IGFBP-3 in ternary complexes which cannot leave the circulation. The serum IGF-I concentration manifests an age-dependent pattern, mainly owing to the age-dependent level of GH production. After increasing during puberty, IGF-I levels then decrease with increasing age.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed1995

Serum proteolysis of IGFBP-3.

Insulin-like growth factor (IGF) bioavailability is modulated by a family of six IGF binding proteins (IGFBPs) that binds IGF with affinities similar to that of the type 1 IGF receptor. Proteolytic degradation of IGFBP-3, the major serum IGFBP, was first reported in pregnancy serum and suggested to be an additional mechanism involved in the regulation of IGF bioavailability. In this paper, the presence of serum IGFBP-3 proteolysis and its potential role in the regulation of IGF bioavailability is discussed partly in view of our recent finding of IGFBP-3 proteolysis by the tissue plasminogen activator (tPA)-plasminogen-plasmin system in human serum.

Biological Availability↗
PubMed1995

Serum levels of insulin-like growth factor (IGF)-binding protein-3 (IGFBP-3) in healthy infants, children, and adolescents: the relation to IGF-I, IGF-II, IGFBP-1, IGFBP-2, age, sex, body mass index, and pubertal maturation.

Circulating IGF-I and -II are bound to specific insulin-like growth factor (IGF)-binding proteins (IGFBPs), of which IGFBP-3 binds the majority of the IGFs. IGFBP-3 levels are regulated by GH and have been suggested to provide additional information on GH secretory capacity compared to IGF-I. However, the diagnostic value of IGFBP-3 is still controversial, perhaps because the quality of the available normative data for IGFBP-3 varies. It has recently been shown that a large number of individuals is required to establish reference ranges for IGF-I that take into account age, sex, body mass index (BMI), and pubertal stage. Therefore, we measured IGFBP-3, IGF-I, IGF-II, IGFBP-1, and IGFBP-2 levels by RIA in 907 healthy children to establish well characterized normative data on IGFBP-3 according to age, sex, and pubertal stage and to study the complex relationship between IGFs and their BPs in puberty. We found that IGFBP-3 levels increase with age in children, with maximal levels in puberty; girls experience peak values approximately 1 yr earlier than boys. Age, sex, height, BMI, and pubertal maturation were all important factors in determining the circulating levels of IGFBP-3, whereas IGF-I levels were unaffected by BMI. Comparison of IGFBP-3 with IGF-1 concentrations revealed that they did not exhibit the same developmental pattern in puberty. IGF-I levels increased to relatively higher levels than IGFBP-3, leading to an increasing molar ratio between IGF-I and IGFBP-3 in puberty, when growth velocity is high. Concomitantly, IGF-II and IGFBP-2 levels were unchanged throughout puberty, whereas IGFBP-1 levels declined with age in prepubertal children, with lowest values in puberty. There was a highly significant correlation between IGF-I and -II and IGFBP-3 on a molar basis (r = 0.84; P < 0.0001). Thus, we speculate that IGFBP-3 is pivotal for circulating IGF bioactivity and that the increase in the molar ratio between IGF-I and IGFBP-3 reflects an increase in free, biologically active IGF-I. In conclusion, we have provided normative data on a large group of healthy individuals and conclude that age, sex, height, BMI, and pubertal maturation have to be taken into account before a single IGFBP-3 value in a growth-retarded child can be evaluated properly.

Adolescent↗
PubMed1994

Inverse correlation between insulin-like growth factor binding protein-1 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 GH 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 1800 h 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 micrograms/l (mean +/- SEM) on day 8, and 28.3 +/- 3.2 vs 19.9 +/- 1.6 micrograms/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.

Acromegaly↗
PubMed1994

Maternal hypoxia as a model for intrauterine growth retardation: effects on insulin-like growth factors and their binding proteins.

Evidence suggests that IGF and their binding proteins play a role in fetal growth, but more knowledge concerning their regulation is essential. We examined the expression of IGF and their binding proteins in experimental intrauterine growth-retarded (IUGR) rat fetuses of hypoxic dams (13-14% oxygen, d 14-21 of gestation). The mean body weight of the fetuses (d 21 of gestation, n = 72) of the six hypoxic dams was 24% lower (p < 0.0001) than the mean weight of the fetuses of six control dams (n = 82). Wet liver weights demonstrated a 20% decrease (p < 0.0001) and placentas a 10% decrease (p < 0.01) compared with control fetuses. The mean serum concentrations of immunoreactive IGF-I in both groups were low but did not differ significantly. The mean serum concentrations of immunoreactive IGF-II, however, were higher in IUGR fetuses. As assessed by Northern blot analysis, there was a 4-fold increase in insulin-like growth factor binding protein-1 (IGFBP-1) mRNA expression in the livers of the IUGR fetuses compared with controls. IGFBP-2 mRNA expression was 6-fold increased in IUGR fetal livers. No difference was found in IGFBP-4 mRNA. An increase in IGFBP-1, -2, and -4 concentrations could be seen by Western ligand blotting in the serum of growth-retarded fetuses compared with control fetuses. This finding was verified by immunoprecipitation with specific antibodies, which demonstrated increases in IGFBP-1 and IGFBP-2. Our results validate the use of maternal hypoxia as an experimental model of intrauterine growth retardation and indicate that increased IGFBP-1 and -2 expression may be of importance in the etiology of fetal growth retardation caused by maternal hypoxia.

Animals↗
PubMed1994

Ontogeny of insulin-like growth factor-binding protein-1, -2, and -3: quantitative measurements by radioimmunoassay in human fetal serum.

There is evidence for a role for IGF-I in the endocrine control of human fetal growth despite the low serum IGF-I concentrations. The formation in serum of binary complexes between IGF-I or -II and either of six IGF binding proteins (IGFBP-1 to -6) and, in particular, of long-lived ternary complexes between IGF-I or -II, IGFBP-3, and acid-labile subunit is thought to regulate IGF-I bioavailability by increasing its serum half-life. The present study assesses the bioavailability of circulating IGF-I in 19- to 35-wk gestation human fetuses in utero 1) by quantitative RIA measurements of IGF and IGFBP in serum and 2) by examining whether serum proteolysis of IGFBP-3 may further increase IGF-I bioavailability. Fetal serum concentrations of IGFBP-3, IGF-I, and IGF-II were low with marked or only modest increases with gestational age (p < 0.001, p < 0.005, and p < 0.05, respectively). The mean molar ratio between IGF-I plus -II and IGFBP-3 demonstrated a molar excess of IGF (50%) similar to that in adolescents but in contrast to the 1:1 molar ratio in adults. The median IGFBP-2 concentration was 3-fold elevated to a molar concentration similar to that of IGFBP-3 (adult serum displays 10-fold higher IGFBP-3 concentrations). The median serum IGFBP-1 concentration was not elevated as previously reported in newborns. IGFBP-3 protease activity was not increased in fetal serum, in contrast to pregnancy serum and amniotic fluid.(ABSTRACT TRUNCATED AT 250 WORDS)

Blotting, Western↗
PubMed1994

Serum insulin-like growth factor-I in 1030 healthy children, adolescents, and adults: relation to age, sex, stage of puberty, testicular size, and body mass index.

Serum levels of insulin-like growth factor-I (IGF-I) increase with age and pubertal development. The large variation in circulating IGF-I levels in adolescence makes it difficult to use the IGF-I value of a single child in the assessment of his growth status. In addition, the interference of IGF-binding proteins in many IGF-I assays contributes to this problem. We measured IGF-I in acid-ethanol-extracted serum from 1030 healthy children, adolescents, and adults, employing a RIA that reduces interference of IGF-binding proteins by using monoiodinated Tyr31-[125I]des-(1-3)IGF-I as radioligand. Mean serum IGF-I concentrations increased slowly in prepubertal children from 80-200 micrograms/L with a further steep increase during puberty to approximately 500 micrograms/L. After puberty, a subsequent continuous fall in circulating IGF-I levels was apparent throughout adulthood to a mean of 100 micrograms/L at the age of 80 yr (P < 0.0001). Girls had maximal IGF-I levels at 14.5 yr of age, whereas boys had peak IGF-I levels 1 yr later. This is almost 2 yr later than average peak height velocity. The large variation in serum IGF-I levels during puberty was diminished when data were separated according to sex and Tanner stage of puberty. Interestingly, we found a significant variation with age within the Tanner stages; there was an increase in serum IGF-I concentrations with age in the early pubertal stages and a decrease in the late stages (P < 0.05). Serum IGF-I increased concomitantly with increasing testicular volume. Multiple regression analysis revealed that serum IGF-I levels predicted height velocity in the following year (r = 0.33; P < 0.0001). Body mass index did not correlate significantly with serum IGF-I in prepubertal children in a multiple regression analysis. In conclusion, there was a significant variation in serum IGF-I levels with age within a given Tanner stage of puberty in addition to the well known increase with increasing age or pubertal stage. Accordingly, the effects of sex, age, and puberty on serum IGF-I cannot be separated into simple additive components when studying 1030 children in a cross-sectional design. Thus, the age-, sex-, and puberty-corrected IGF-I values may, in fact, improve the use of serum IGF-I as a diagnostic tool to distinguish between a child with retarded puberty and a GH-deficient individual.

Adolescent↗
PubMed1994

Fasting affects serum insulin-like growth factors (IGFs) and IGF-binding proteins differently in patients with noninsulin-dependent diabetes mellitus versus healthy nonobese and obese subjects.

In the present study we have 1) assessed how differences in insulin and GH status between obese patients with noninsulin-dependent diabetes mellitus (NIDDM) and healthy obese (OB) and nonobese (NOB) subjects are associated with different responses of insulin-like growth factors (IGFs) and IGF-binding proteins (IGFBPs) to fasting, and 2) determined whether the IGF-I response to fasting in healthy subjects is secondary to changes in IGFBP-3. In patients with NIDDM, there was a lack of response of serum IGF-I concentrations to 4 days of fasting, contrasted with the significant decrease in IGF-I concentrations in NOB subjects (37%; P < 0.001) and the delayed and attenuated decrease in OB subjects (23%; P < 0.01). Insulin and the insulin-regulated IGFBP-1 were also unchanged during fasting in NIDDM, whereas insulin was decreased and IGFBP-1 was increased in both NOB and OB subjects. Insulin-resistant NIDDM patients, with high basal glucose and insulin, normal IGFBP-1, and low GH, had decreased prefasting serum IGF-I concentrations, similar to the values in fasted body mass index- and age-matched OB subjects. IGFBP-3, the major determinant of the IGF-I turnover rate in serum, was unchanged by fasting, as determined by RIA and Western ligand blot analysis. In accordance, no induction of IGFBP-3 proteolytic activity by fasting could be demonstrated. Serum IGF-II concentrations were also unchanged by fasting. Basal immunoreactive IGFBP-3 levels did not differ among the groups, whereas IGFBP-3 by Western ligand blot analysis was decreased in NIDDM in accordance with the finding of increased IGFBP-3 proteolysis in NIDDM. In conclusion, 1) differences in GH status and modulation of GH induction of IGF-I by insulin resistance could contribute to low basal IGF-I levels and lack of a IGF-I response to fasting in patients with NIDDM; and 2) the turnover rate of IGF-I in serum, which is largely determined by IGFBP-3, is not likely to be altered by short term fasting, suggesting that the decrease in serum IGF-I concentrations is a result of decreased IGF-I production.

Adult↗
PubMed1994

Increased proteolysis of insulin-like growth factor-binding protein-3 (IGFBP-3) in noninsulin-dependent diabetes mellitus serum, with elevation of a 29-kilodalton (kDa) glycosylated IGFBP-3 fragment contained in the approximately 130- to 150-kDa ternary complex.

Insulin-like growth factor-I (IGF-I) in serum is predominantly bound in a ternary complex, consisting of IGF peptide, IGF-binding protein-3 (IGFBP-3), and an acid-labile subunit, or a binary complex, consisting of IGF peptide and any of the six IGFBPs. In the binary complex, IGF-I is more bioavailable and has a faster turnover rate. Proteolysis of IGFBP-3 may alter the distribution of IGF-I between these complexes by reducing IGFBP-3 affinity for IGF-I and/or acid-labile subunit and may offer an additional mechanism for regulation of IGF availability. In the present study, sera from patients with noninsulin-dependent diabetes mellitus (NIDDM) were found to have significantly higher IGFBP-3 proteolytic activity than sera from age-matched healthy subjects (188 +/- 12% vs. 104 +/- 6% of a control serum pool; P < 0.001). The mean (+/- SE) of serum IGFBP-3 levels determined by Western ligand blotting was lower in NIDDM patients than in healthy control subjects (61.5 +/- 5% and 79 +/- 5% of a control serum pool, respectively; P < 0.01). However, IGFBP-3 concentrations determined by RIA did not differ. This discrepancy could be explained by IGFBP-3 proteolysis, resulting in IGFBP-3 fragments that are detectable by RIA, but not by Western ligand blotting. Western immunoblotting of sera with or without prior treatment with endoglycosidase-F demonstrated that a glycosylated 29-kilodalton (kDa) IGFBP-3 form with a protein core of 20 kDa was present in sera from healthy controls, and this fragment was increased in NIDDM and term pregnancy sera, suggesting that it is produced by endogenous proteolysis. The presence of the 29-kDa IGFBP-3 proteolytic fragment at about 130-150 kDa after neutral size chromatography of pooled sera may suggest that 29-kDa IGFBP-3 participates in ternary complex formation. Further studies are required to determine whether the avidity of ternary complex formation with the 29-kDa IGFBP-3 fragment is reduced and whether the resulting increased IGF turnover can explain the reduced IGF-I levels (z scores) observed in NIDDM patients compared to healthy subjects (-0.81 +/- 0.32 SD vs. +0.26 +/- 0.17 SD; P < 0.001). Neutral size-chromatography of sera demonstrated that IGFBP-3 protease activity in the approximately 130- to 150-kDa mol wt range is regulated by NIDDM and pregnancy in parallel with that of unfractionated sera.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1994

Decreased ternary complex formation and predominance of a 29 kDa IGFBP-3 fragment in human fetal serum.

Insulin-like growth factor-I (IGF-I) has been proposed to be important in the endocrine control of fetal growth in humans, although serum IGF-I concentrations are 10-fold lower than during rapid pubertal growth. However, the bioavailability of IGF-I in fetal serum may be increased by changes in the specific IGF binding proteins (IGFBPs). We have recently suggested that the bioavailability of circulating IGF-I is increased in the human fetus due to the molar excess of IGF-I plus IGF-II relative to IGFBP-3 as well as the increased concentrations of IGFBP-2, which does not form a long-lived ternary complex. We have presently studied ternary complex formation between IGF, IGFBP-3, and acid labile subunit (ALS) to further assess if IGF-I bioavailability is increased in human fetal serum. In 19-35 week gestation fetal sera, a markedly decreased formation of the ternary complex was demonstrated by the general absence of IGFBP-3 (detected by Western immunoblotting) in the approximately 130-150 kDa ternary complex after neutral size chromatography. The predominant form of IGFBP-3 in fetal serum was a 29 kDa fragment, which, following deglycosylation by Endoglycosidase-F, was demonstrated to consist of a approximately 20 kDa protein core. Despite the predominance of the 29 kDa IGFBP-3 fragment, we have previously demonstrated that the IGFBP-3 protease activity is not increased in fetal serum, in contrast to pregnancy or non-insulin dependent diabetes mellitus (NIDDM) sera.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Insulin-like growth factor (IGF) I and II and IGF binding protein (IGFBP) 1, 2 and 3 in serum from patients with Cushing's syndrome.

In the present study of twenty-two patients with Cushing's syndrome, serum insulin-like growth factor (IGF)-I concentrations were normal to high with an increased mean IGF-I concentration, 40% above that of healthy subjects of the same age (p < 0.001). Serum IGF-II concentrations were normal. The morning serum IGF binding protein (IGFBP)-1 concentrations were within the range of healthy controls. IGFBP-1 was inversely correlated to the IGF-I concentration (p < 0.001) and to the 24 h urinary cortisol excretion (p < 0.005) with a combined R squared value of 0.58. In contrast to IGFBP-1, serum IGFBP-2 and IGFBP-3 concentrations were elevated by 1.89 +/- 1.78 SD and 0.92 +/- 0.78 SD (mean +/- 2 SD), respectively. Although increased, the serum IGFBP-2 concentration was inversely correlated to the IGF-I concentration (r = -0.67, p < 0.001). Immunoreactive IGFBP-3 was increased in proportion to IGF-I and the molar ratio [IGFBP-3]:[IGF-I] + [IGF-II] was close to unity (1.04 +/- 0.14), as that of healthy subjects. In serum from patients with Cushing's syndrome, with increased immunoreactive IGFBP-3, there was a corresponding increase in intact glycosylated 40-43 kDa IGFBP-3 as determined by Western ligand blotting. Neutral size chromatography of serum from patients with Cushing's syndrome showed that IGF-I and IGFBP-3 immunoreactivity were predominantly found at the elution volume of the ternary 150 kDa IGF-I/IGFBP-3/acid labile subunit complex and a similar pattern was displayed by normal serum.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Insulin-like growth factor II stimulates glucose transport in human skeletal muscle.

We investigated the effect of insulin-like growth factor II (IGF-II) and insulin-like growth factor binding protein-1 (IGFBP-1) on 3-O-methylglucose transport in incubated human skeletal muscle strips. Increasing physiological concentrations of IGF-II stimulated glucose transport in a dose-dependent manner. Glucose transport was maximally stimulated in the presence of 100 ng/ml (13.4 nM) of IGF-II, which corresponded to the effect obtained by 100 microU/ml (0.6 nM) of insulin. Exposure of muscle strips to IGFBP-1 (500 ng/ml) inhibited the maximal effect of IGF-II on glucose transport by 40%. Thus, it is conceivable that IGF-II and IGFBP-1 are physiological regulators of the glucose transport process in human skeletal muscle.

Adult↗