Insulin and insulin-like growth factors in diabetes mellitus

Acromegaly presenting with low insulin-like growth factor-1 levels and diabetes: a case report

Introduction

Acromegaly is an endocrine disorder arising from excessive serum growth hormone levels in adulthood and is characterized by progressive somatic enlargement. Biochemical confirmation is achieved by demonstration of elevated baseline serum growth hormone levels which are not suppressed during an oral glucose tolerance test, and by increased levels of serum insulin-like growth factor-1. The serum insulin-like growth factor-1 level provides an assessment of integrated growth hormone secretion and is recommended for diagnosis, monitoring, and screening of acromegaly. We report a case of a patient with acromegaly secondary to a pituitary microadenoma who presented with low insulin-like growth factor-1.

Case presentation

An 83-year-old Sinhalese woman presented to our hospital with an enlarging multinodular goiter. She was observed to have macroglossia, thickened coarse skin, acral enlargement, and newly detected, uncontrolled diabetes. A diagnosis of acromegaly was suspected. She did not complain of recent headaches, vomiting, visual difficulties, or galactorrhea and was clinically euthyroid. Her pulse rate was 84 beats/min, and her blood pressure was 150/90 mmHg. A visual field assessment did not reveal a defect. Her random growth hormone levels were 149 mU/L (<10 mU/L), and her oral glucose tolerance test was supportive of acromegaly with a paradoxical rise of growth hormone. Her serum age-specific insulin-like growth factor-1 level was below normal at 124.7 ng/ml (normal range 150–350 ng/ml). Her serum insulin-like growth factor-1 level, measured after glycemic control was achieved with metformin and insulin, was elevated, which is characteristic of acromegaly. Magnetic resonance imaging of her pituitary revealed a pituitary microadenoma. Acromegaly secondary to a growth hormone–secreting pituitary microadenoma was confirmed.

Conclusions

Systemic illnesses, including catabolic states, hepatic or renal failure, malnutrition, and diabetes mellitus, are known to decrease insulin-like growth factor-1 levels and may result in false-negative values in patients with acromegaly A low insulin-like growth factor-1 level does not exclude acromegaly in a patient with supportive clinical features and poorly controlled diabetes.

Growth abnormalities in children with type 1 diabetes, juvenile chronic arthritis, and asthma

Children and adolescents with chronic diseases are commonly affected by a variable degree of growth failure, leading to an impaired final height. Of note, the peculiar onset during childhood and adolescence of some chronic diseases, such as type 1 diabetes, juvenile idiopathic arthritis, and asthma, underlines the relevant role of healthcare planners and providers in detecting and preventing growth abnormalities in these high risk populations. In this review article, the most relevant common and disease-specific mechanisms by which these major chronic diseases affect growth in youth are analyzed. In addition, the available and potential targeting strategies to restore the physiological, hormonal, and inflammatory pattern are described.

Intensive insulin therapy during cardiovascular surgery

Recent evidence in the fields of surgery, emergency and critical care medicine indicates that strict glycemic control results in lower mortality. Hyperglycemia occurs frequently in patients with and without diabetes during cardiovascular surgery, especially during cardiopulmonary bypass. However, strict glucose control is difficult to achieve during cardiovascular procedures. To establish effective intensive insulin therapy during cardiovascular surgery, we conduct continuous blood glucose monitoring and employ automatic control by using an artificial endocrine pancreas (the STG-22, Nikkiso, Tokyo, Japan). In this review, we will outline the present status and problems of conventional glycemic control for perioperative cardiovascular surgery and introduce the new perioperative blood glucose management method that we are testing now. We will also discuss the importance of perioperative glycemic control for cardiovascular surgery as well as future prospects.

Problems associated with glucose toxicity: Role of hyperglycemia-induced oxidative stress

Glucose homeostasis deficiency leads to a chronic increase in blood glucose concentration. In contrast to physiological glucose concentration, chronic superphysiological glucose concentration negatively affects a large number of organs and tissues. Glucose toxicity means a decrease in insulin secretion and an increase in insulin resistance due to chronic hyperglycemia. It is now generally accepted that glucose toxicity is involved in the worsening of diabetes by affecting the secretion of β-cells. Several mechanisms have been proposed to explain the adverse effects of hyperglycemia. It was found that persistent hyperglycemia caused the functional decline of neutrophils. Infection is thus the main problem resulting from glucose toxicity in the acute phase. In other words, continued hyperglycemia is a life-threatening risk factor, not only in the chronic but also the acute phase, and it becomes a risk factor for infection, particularly in the perioperative period.

Anti-insulin-like growth factor-1 autoantibodies in type 1 diabetes

Insulin-like growth factor-1 (IGF-1) reportedly suppresses the development of type 1 diabetes in NOD mice, suggesting that IGF-1 is possibly a candidate for the autoantigens in type 1 diabetes. We therefore examined the anti-IGF-1 autoantibodies (IGF-1 Ab) in sera from patients with type 1 diabetes using radioimmunoassay. However, we were unable to demonstrate the existence of anti-IGF-1 autoantibodies in type 1 diabetes with our method. Further study is necessary to clarify whether anti-IGF-1 autoantibodies are existent in human type 1 diabetes and to determine the significance of IGF-1 in the pathogensesis of type 1 diabetes.

Insulin-like growth factor binding proteins (IGFBPs) in serum and urine and IGFBP-2 protease activity in patients with insulin-dependent diabetes mellitus

Diabetes mellitus and glucose dysregulation have significant effects on the circulating level of insulin-like growth factor-I (IGF-I) and IGF binding proteins (IGFBPs). In the present study, serum and urine IGFBP (IGFBP-1, -2, and -3) and serum IGF-I and -II levels were measured by radioimmunoassay (RIA) in 27 patients with type 1 diabetes aged 9 to 48 years compared with 9 healthy subjects aged 10 to 28 years. The patients were divided into 3 groups according to the amount of albumin excreted in 24 hours. The macroalbuminuria group (>500 mg/24 h) had elevated serum IGFBP-1 and -2 and decreased IGF-I levels (P < .01 v normal controls). Serum IGFBP-3 and IGF-II were not different among the patient groups and controls (P > .05). The mean urinary IGFBP-1 was decreased in all 3 patient groups compared with the controls (P < .05). Urinary IGFBP-2 and IGFBP-3 were increased in patients with macroalbuminuria. Immunoblot analysis showed increased low-molecular-weight fragments of urinary IGFBP-2 in the poorly controlled diabetics, and direct evidence for increased urinary IGFBP-2 proteolytic activity could be demonstrated in both the microalbuminuric and macroalbuminuric groups. Low-molecular-weight fragments of urinary IGFBP-3 were also increased in both the microalbuminuric and macroalbuminuric groups. In conclusion, alterations of IGFBPs in urine and serum are related to metabolic control in diabetic patients, and there is an increase of urinary IGFBP-2 protease activity in poorly controlled diabetics. The changes in serum IGFBP concentrations (eg, increases in IGFBP-1 and IGFBP-2) may lead to alterations in the availability of IGF-I to peripheral tissues.

Is growth hormone hypersecretion in diabetic adolescent girls also a daytime problem?

OBJECTIVES

Glycaemic control often deteriorates during puberty in girls with insulin dependent diabetes mellitus (IDDM). This may be due in part to the normal psychosocial changes associated with adolescence. Puberty is, however, also characterized by rapid somatic development, orchestrated by hormonal changes. Some of these hormones play a major role in glucose homeostasis. We have examined the insulin-GH-IGF-I axis in 11 adolescent girls with poorly controlled insulin dependent diabetes and compared the data with those of 10 non-diabetic girls matched for age, pubertal stage and body mass index (BMI).

METHODS

Serum profiles of glucose, insulin, GH and IGF binding protein 1 (IGFBP1) were analysed in addition to IGF-I in serum and nocturnal urinary excretion of GH.

MEASUREMENTS

Serum glucose, insulin and IGFBP1 were measured every hour for 24 h, whereas GH in serum was measured every 30 minutes during the same period. Nocturnal urinary GH was analysed as a mean of three consecutive nights.

RESULTS

The insulin profiles of the IDDM patients were flat with low post-prandial peaks, corresponding to only one-third of the peaks of the non-diabetic girls. The integrated insulin levels, both during 24-h sampling and during daytime, were significantly lower in the diabetic group. There were no differences during night-time. The diabetic patients had elevated mean baseline levels of serum GH (IDDM 2.8 +/- 0.5 mU/l, controls 0.7 +/- 0.2; P < 0.001), a higher 24-h mean serum GH level (9.8 +/- 1.7 mU/l vs. 4.4 +/- 0.7; P < 0.001), significantly more peaks and a urinary GH excretion twice as high as in the non-diabetic group. An interesting observation was the finding of marked differences in daytime GH concentrations between the groups, both regarding overall integrated levels (GH AUC 103 +/- 15.8 and 35.9 +/- 7.1 mU/l x 12 h, respectively; P < 0.005) as well as baseline levels (3.8 +/- 0.6 mU/l vs. 0.7 +/- 0.2; P < 0.001). In contrast, during night-time only the mean basal levels of GH differed. The level of IGF-I was reduced in the diabetic group compared with the healthy controls (IDDM 233 +/- 19 micrograms/l vs. controls 327 +/- 21; P < 0.005). In addition, the IDDM patients had significantly increased concentrations of IGFBP 1, but kept a normal diurnal rhythm with a pronounced night peak.

CONCLUSION

Hypoinsulinaemia in adolescent IDDM patients, particularly in the portal hepatic circulation, results in decreased IGF-I and increased IGFBP 1 production in the liver. High levels of IGFBP 1 may, in turn, reduce the bioactivity of IGF-I even further. Low levels of IGF-I will lead to increased GH secretion. Earlier studies on the relationship between GH and diabetic control have focused on elevated GH levels during the night. In this study we have observed markedly elevated levels of GH also during daytime in adolescent IDDM patients. This indicates increased insulin resistance and insulin demand also during the day in diabetic subjects. The increased insulin resistance may result in hyperglycaemia leading to additional insulin resistance. A vicious circle may thus be induced, accelerating metabolic impairment in poorly controlled adolescent IDDM girls.

In vitro effects of growth hormone (GH) and insulin-like growth factor I and II (IGF-I and -II) on chromosome fragility and p53 protein expression in human lymphocytes

BACKGROUND

We have reported previously that growth hormone (GH) therapy increases cell radiosensitivity; in this study we tested whether GH itself or IGFs induce chromosome aberrations and investigated the expression of p53 protein in response to DNA damage.

METHODS

Human peripheral blood lymphocytes were incubated with GH [100 and 1000 microg L(-1)], insulin-like growth factor I [IGF-I; 150 and 1000 microg L(-1)] and IGF-II [600 and 1200 microg L(-1)] for 24 h. The radiomimetic agent bleomycin [BLM; 5 microgm L(-1)] was added in the last 3 h. Cytogenetic analysis was performed by assessing the percentages of damaged cells (%DC) and chromosome aberrations (%CA). The expression of p53 was investigated by flow cytometric assay using the monoclonal antibody DO-7, and expressed as percentage positive cells and mean fluorescence intensity.

RESULTS

BLM significantly increased both percentage DC and percentage CA and p53 expression (P < 0.01). The %DC was unaffected by the tested peptides. IGF-I [150 microg L(-1)] increased spontaneous percentage CA (P < 0.01). All peptides further increased the BLM-induced chromosome breakage: GH 100 and 1000 microg L(-1) by 30% and 73% respectively, IGF-I 150 and 1000 microg L(-1) by 41% and 96% respectively and IGF-II 600 and 1200 microg L(-1) by 89% and 45% respectively. The spontaneous and BLM-induced expression of p53 was unaffected by GH, whereas it was significantly increased by IGFs (P < 0001).

CONCLUSIONS

These results indicate that the DNA-damaging effect of BLM is amplified by GH and, more markedly, IGF-I and -II. IGF-I and -II also stimulate p53 protein expression that, taking part in DNA repair, may counteract the IGF action on genome stability.

Randomised placebo-controlled trial of human recombinant insulin-like growth factor I plus intensive insulin therapy in adolescents with insulin-dependent diabetes mellitus

BACKGROUND

Good glycaemic control in insulin-dependent diabetes mellitus (IDDM) to prevent complications may be difficult to achieve during adolescence, because abnormalities in production of growth hormone or insulin-like growth-factor-I (IGF-I) can lead to lower insulin sensitivity. Recombinant human IGF-I (rhIGF-I) given as an adjunct to insulin therapy in IDDM, might improve glycaemic control in adolescents; we investigated the effects of the addition of IGF-I in a randomised, double-blind, placebo-controlled trial.

METHODS

53 patients with IDDM (26 male, 27 female) with a median age of 16.1 years (range 10.8-20.6) and diabetes of more than 2 years' duration were randomly assigned subcutaneous rhIGF-I (20 or 40 microg/kg daily [n=18, n=18, respectively]) or placebo (n=17), both in addition to multiple-injection insulin therapy for 24 weeks. The primary endpoint, glycated haemoglobin (HbA1c) and routine biochemistry were measured every 4 weeks. Retinal photographs and glomerular-filtration rates were assessed at base line and at the end of the study. Data were analysed by intention to treat.

FINDINGS

With a dose of 40 microg/kg rhIGF-I daily, we found significant reductions in HbA1c compared with placebo (p=0.03), without changes in body-mass index, rate of hypoglycaemia, insulin dose, or circulating concentrations of IGF-binding proteins 1 and 3. The greatest median change in HbA1c of -0.6% (range -2.8 to -1.5%) was seen with rhIGF-I 40 microg/kg at week 12, but was not sustained at week 24. The greatest reductions in HbA1c at week 24 were seen among patients with the greatest changes in IGF-I concentrations (r=-0442, p=0.002). Retinal photographs, renal function (glomerular filtration rate and urinary albumin excretion), and routine biochemistry showed no adverse events.

INTERPRETATION

Our data confirm that rhIGF-I as an adjunct to insulin therapy can improve HbA1c values in adolescents with IDDM without overt toxic effects, but they raise questions about whether these effects can be sustained in cases of poor compliance or reduced bioefficacy.

Current and potential therapeutic uses of growth hormone and insulin-like growth factor I

The accepted and potential uses of GH and IGF-I are summarized in Table 1. In general, the research on the therapeutic uses of IGF-I is at a much earlier state of development compared with GH The use of GH in the treatment of children with GH deficiency is well accepted, and its use in the treatment of short stature of renal failure also is widely accepted. The FDA has approved the use of GH in children with short stature caused by GH insufficiency and renal failure. The use of GH in patients with Turner syndrome has not been approved by the FDA, although it has been approved in several other countries. The use of GH for the treatment of adults with GH deficiency is approved in several countries but it is not approved in the Unites States. With the exception of the cases with GHIS, the use of IGF-I as a therapeutic agent cannot yet be regarded as of proven usefulness. The potential uses of GH and IGF-I are an area of active investigation and will continue to enlighten our understanding of human disease and disorders of growth.