The dawn phenomenon is related to overnight growth hormone release in adolescent diabetics

Dual-basal-insulin regimen for the management of dawn phenomenon in children with type 1 diabetes: a retrospective cohort study

Background

Handling of the dawn phenomenon (DP) with multiple daily insulin injection (MDII) regimen is a real challenge.

Objective

We aimed to demonstrate the effectiveness of a dual-basal-insulin (a long-acting glargine and an intermediate-acting neutral protamine Hagedorn (NPH)) regimen for the management of DP in children with type 1 diabetes mellitus (T1DM). The primary efficacy outcome was to overcome morning hyperglycemia without causing hypoglycemia during the non-DP period of the night.

Design

Retrospective cohort study.

Method

Charts of 28 children with T1DM (12 female; 42.8%, mean age 13.7 ± 2.1 years) treated with MDII were retrospectively reviewed. The median duration of diabetes was 4.5 years (range 2-13.5 years). DP was diagnosed using a threshold difference of 20 mg/dL (0.1 mmol/L) between fasting capillary blood glucose at 3 a.m. and prebreakfast. NPH was administered at midnight in addition to daily bedtime (08.00-09.00 p.m.) glargine (dual-basal-insulin regimen). Midnight, 03:00 a.m., prebreakfast and postprandial capillary blood glucose readings, insulin-carbohydrate ratios, and basal-bolus insulin doses were recorded the day before the dual-basal-insulin regimen was started and the day after the titration of the insulin doses was complete. Body mass index standard deviation scores (BMI SDS) at the onset-3rd-12th month of treatment were noted.

Results

Before using dual basal insulin, prebreakfast capillary blood glucose levels were greater than those at midnight and at 03:00 a.m. (F = 64.985, p < 0.01). After titration of the dual-basal-insulin doses, there were significant improvements such that there were no statistically significant differences in the capillary blood glucose measurements at the three crucial time points (midnight, 03.00 a.m., and prebreakfast; F = 1.827, p = 0.172). No instances of hypoglycemia were reported, and the total daily insulin per kilogram of body weight did not change. The BMI SDS remained steady over the course of the 1-year follow-up.

Conclusion

In this retrospective cohort study, the dual-basal-insulin regimen, using a long-acting glargine and an intermediate-acting NPH, was effective in overcoming early morning hyperglycemia due to insulin resistance in the DP. However, the effectiveness of the dual-basal-insulin regimen needs to be verified by prospective controlled studies using continuous glucose monitoring metrics or frequent blood glucose monitoring.

The Effect of High-Intensity Interval Exercise on Short-Term Glycaemic Control, Serum Level of Key Mediator in Hypoxia and Pro-Inflammatory Cytokines in Patients with Type 1 Diabetes-An Exploratory Case Study

Type 1 diabetes (T1D) is associated with hyperglycaemia-induced hypoxia and inflammation. This study assessed the effects of a single bout of high-intensity interval exercise (HIIE) on glycaemia (BG) and serum level of pro-inflammatory cytokines, and an essential mediator of adaptive response to hypoxia in T1D patients. The macronutrient intake was also evaluated. Nine patients suffering from T1D for about 12 years and nine healthy individuals (CG) were enrolled and completed one session of HIIE at the intensity of 120% lactate threshold with a duration of 4 × 5 min intermittent with 5 min rests after each bout of exercise. Capillary and venous blood were withdrawn at rest, immediately after and at 24 h post-HIIE for analysis of BG, hypoxia-inducible factor alpha (HIF-1α), tumour necrosis factor alpha (TNF-α) and vascular-endothelial growth factor (VEGF). Pre-exercise BG was significantly higher in the T1D patients compared to the CG (p = 0.043). HIIE led to a significant decline in T1D patients' BG (p = 0.027) and a tendency for a lower BG at 24 h post-HIIE vs. pre-HIIE. HIF-1α was significantly elevated in the T1D patients compared to CG and there was a trend for HIF-1α to decline, and for VEGF and TNF-α to increase in response to HIIE in the T1D group. Both groups consumed more and less than the recommended amounts of protein and fat, respectively. In the T1D group, a tendency for a higher digestible carbohydrate intake and more frequent hyperglycaemic episodes on the day after HIIE were observed. HIIE was effective in reducing T1D patients' glycaemia and improving short-term glycaemic control. HIIE has the potential to improve adaptive response to hypoxia by elevating the serum level of VEGF. Patients' diet and level of physical activity should be screened on a regular basis, and they should be educated on the glycaemic effects of digestible carbohydrates.

Reassessing the evidence: prandial state dictates glycaemic responses to exercise in individuals with type 1 diabetes to a greater extent than intensity

Recent guidelines suggest that adding anaerobic (high intensity or resistance) activity to an exercise session can prevent blood glucose declines that occur during aerobic exercise in individuals with type 1 diabetes. This theory evolved from earlier study data showing that sustained, anaerobic activity (high intensity cycling) increases blood glucose levels in these participants. However, studies involving protocols where anaerobic (high intensity interval) and aerobic exercise are combined have extremely variable glycaemic outcomes, as do resistance exercise studies. Scrutinising earlier studies will reveal that, in addition to high intensity activity (intervals or weight lifting), these protocols had another common feature: participants were performing exercise after an overnight fast. Based on these findings, and data from recent exercise studies, it can be argued that participant prandial state may be a more dominant factor than exercise intensity where glycaemic changes in individuals with type 1 diabetes are concerned. As such, a reassessment of study outcomes and an update to exercise recommendations for those with type 1 diabetes may be warranted.

Fasting May Alter Blood Glucose Responses to High-Intensity Interval Exercise in Adults With Type 1 Diabetes: A Randomized, Acute Crossover Study

OBJECTIVES

In individuals with type 1 diabetes (T1D), changes in blood glucose (BG) during high-intensity interval exercise (HIIE) are smaller than those observed during aerobic exercise. Study outcomes, however, have been variable, with some demonstrating significant BG decreases and others showing BG increases. This study compared BG outcomes between fasting (AME) and postprandial (PME) HIIE in T1D to test the hypothesis that AME would produce a BG increase, yet PME would cause BG to decline.

METHODS

Twelve (6 men and 6 women) physically active individuals with T1D performed two 45-minute exercise sessions (AME at 7:00 AM, PME at 5:00 PM) in random order, separated by at least 48 hours. Sessions consisted of a 10-minute warmup (50%VO_2peak), followed by 10-second sprints every 2 minutes for 24 minutes, and then an 11-minute cooldown. Capillary glucose was measured pre- and postexercise, and then 60 minutes postexercise. Interstitial glucose was recorded for 24 hours postexercise using continuous glucose monitoring.

RESULTS

AME caused capillary glucose to increase (from 7.6±1.4 to 9.2±2.9 mmol/L during exercise, and 9.9±2.8 mmol/L in recovery), whereas PME produced a decline in capillary glucose (from 9.9±3.1 to 9.5±3.4 mmol/L during exercise and 8.9±2.7 mmol/L during recovery; time × treatment interaction, p=0.014). PME was associated with a higher frequency of hyperglycemic events in the 6 hours and overnight (midnight to 6:00 AM) after exercise.

CONCLUSIONS

Fasting HIIE results in a different BG trajectory than postprandial exercise in T1D, and may be beneficial for hypoglycemia avoidance during exercise.

Carbohydrate Intake in the Context of Exercise in People with Type 1 Diabetes

Although the benefits of regular exercise on cardiovascular risk factors are well established for people with type 1 diabetes (T1D), glycemic control remains a challenge during exercise. Carbohydrate consumption to fuel the exercise bout and/or for hypoglycemia prevention is an important cornerstone to maintain performance and avoid hypoglycemia. The main strategies pertinent to carbohydrate supplementation in the context of exercise cover three aspects: the amount of carbohydrates ingested (i.e., quantity in relation to demands to fuel exercise and avoid hypoglycemia), the timing of the intake (before, during and after the exercise, as well as circadian factors), and the quality of the carbohydrates (encompassing differing carbohydrate types, as well as the context within a meal and the associated macronutrients). The aim of this review is to comprehensively summarize the literature on carbohydrate intake in the context of exercise in people with T1D.

Morning (Fasting) vs Afternoon Resistance Exercise in Individuals With Type 1 Diabetes: A Randomized Crossover Study

OBJECTIVE

To determine the effect of morning exercise in the fasting condition vs afternoon exercise on blood glucose responses to resistance exercise (RE).

RESEARCH DESIGN AND METHODS

For this randomized crossover design, 12 participants with type 1 diabetes mellitus [nine females; aged 31 ± 8.9 years; diabetes duration, 19.1 ± 8.3 years; HbA1c, 7.4% ± 0.8% (57.4 ± 8.5 mmol/mol)] performed ∼40 minutes of RE (three sets of eight repetitions, seven exercises, at the individual's predetermined eight repetition maximum) at either 7 am (fasting) or 5 pm. Sessions were performed at least 48 hours apart. Venous blood samples were collected immediately preexercise, immediately postexercise, and 60 minutes postexercise. Interstitial glucose was monitored overnight postexercise by continuous glucose monitoring (CGM).

RESULTS

Data are presented as mean ± SD. Blood glucose rose during fasting morning exercise (9.5 ± 3.0 to 10.4 ± 3.0 mmol/L), whereas it declined with afternoon exercise (8.2 ± 2.5 to 7.4 ± 2.6 mmol/L; P = 0.031 for time-by-treatment interaction). Sixty minutes postexercise, blood glucose concentration was significantly higher after fasting morning exercise than after afternoon exercise (10.9 ± 3.2 vs 7.9 ± 2.9 mmol/L; P = 0.019). CGM data indicated more glucose variability (2.7 ± 1.1 vs 2.0 ± 0.7 mmol/L; P = 0.019) and more frequent hyperglycemia (12 events vs five events; P = 0.025) after morning RE than after afternoon RE.

CONCLUSIONS

Compared with afternoon RE, morning (fasting) RE was associated with distinctly different blood glucose responses and postexercise profiles.

Analysis of Prevalence, Magnitude and Timing of the Dawn Phenomenon in Adults and Adolescents With Type 1 Diabetes: Descriptive Analysis of 2 Insulin Pump Trials

OBJECTIVES

To better understand the dawn phenomenon in type 1 diabetes, we sought to determine its prevalence, timing and magnitude in studies specifically designed to assess basal insulin requirements in patients using insulin pumps.

METHODS

Thirty-three participants from 2 sensor-augmented insulin pump studies were analyzed. Twenty participants were obtained from a methodologically ideal semiautomated basal analysis trial in which basal rates were determined from repeated fasting tests (the derivation set) and 13 from an artificial pancreas trial in which duration of fasting was variable (the "confirmation" set). Prevalence was determined for the total cohort and for individual trials using the standard definition of an increase in insulin exceeding 20% and lasting ≥90 minutes. Among cases, time of onset and percent change in the magnitude of basal delivery were determined.

RESULTS

Seventeen participants (52%) experienced the dawn phenomenon (11 of 20 [55%] in the derivation set and 6 of 13 [46%] in the confirmation set). Time of onset was 3 AM (interquartile range [IQR], 3 to 4:15 AM) in the derivation set and 3 AM (IQR, 3 to 4 AM) in the confirmation set. The magnitude of the dawn phenomenon was a 58.1% (IQR, 28.8% to 110.6%) increase in insulin requirements in the derivation set and 65.5% (IQR, 45.6% to 87.4%) in the confirmation set.

CONCLUSIONS

The dawn phenomenon occurs in approximately half of patients with type 1 diabetes; when present, it has predictable timing of onset (generally 3 AM) and a substantial, but highly variable, magnitude. These findings imply that optimization of glycemic control requires clinical emphasis on fasted overnight basal insulin assessment.

Carbohydrate Restriction in Type 1 Diabetes: A Realistic Therapy for Improved Glycaemic Control and Athletic Performance?

Around 80% of individuals with Type 1 diabetes (T1D) in the United States do not achieve glycaemic targets and the prevalence of comorbidities suggests that novel therapeutic strategies, including lifestyle modification, are needed. Current nutrition guidelines suggest a flexible approach to carbohydrate intake matched with intensive insulin therapy. These guidelines are designed to facilitate greater freedom around nutritional choices but they may lead to higher caloric intakes and potentially unhealthy eating patterns that are contributing to the high prevalence of obesity and metabolic syndrome in people with T1D. Low carbohydrate diets (LCD; <130 g/day) may represent a means to improve glycaemic control and metabolic health in people with T1D. Regular recreational exercise or achieving a high level of athletic performance is important for many living with T1D. Research conducted on people without T1D suggests that training with reduced carbohydrate availability (often termed "train low") enhances metabolic adaptation compared to training with normal or high carbohydrate availability. However, these "train low" practices have not been tested in athletes with T1D. This review aims to investigate the known pros and cons of LCDs as a potentially effective, achievable, and safe therapy to improve glycaemic control and metabolic health in people with T1D. Secondly, we discuss the potential for low, restricted, or periodised carbohydrate diets in athletes with T1D.

The Effectiveness and Risks of Programming an Insulin Pump to Counteract the Dawn Phenomenon in Type 1 Diabetes

OBJECTIVE

Continuous subcutaneous insulin infusion (CSII) programming for an early morning increase in insulin delivery is frequently recommended to counteract the rise in glucose prior to breakfast (dawn phenomenon). However, both the effectiveness and safety of this approach have not been tested in the ambulatory setting. Using continuous glucose monitoring, we investigated the safety and effectiveness of early morning CSII programming for management of the dawn phenomenon in subjects with type 1 diabetes.

METHODS

We conducted a controlled, observational eight-month longitudinal study of type 1 diabetic patients (n=40). Reproducibility of the dawn phenomenon was determined in subjects treated with multiple daily injections of insulin (MDI, n=12) and those on CSII who did not program an early morning increase in insulin delivery (CSII non-programmers, n=8). The effects of early morning CSII programming were determined by comparing rates of the dawn phenomenon and hypoglycemia in CSII non-programmers versus CSII-users who programmed an early morning increase in insulin delivery (CSII programmers, n=20).

RESULTS

The dawn phenomenon occurred in all tested subjects to a variable extent (median rate 56% of nights). CSII programming was not associated with a reduction in the occurrence of the dawn phenomenon (42%) compared to non-programmers (48%) (P=0.47) nor in the magnitude of the dawn phenomenon. Hypoglycemia occurred more frequently in the CSII programmers (37%) compared to non-programmers (18%) (P=0.001).

CONCLUSION

The dawn phenomenon occurs unpredictably; therefore, early morning CSII programming for a fixed increase in early morning insulin delivery is ineffective and may be hazardous to the patient.

Insulin therapy in children and adolescents with type 1 diabetes

Treatment of type 1 diabetes mellitus (T1DM) requires lifelong administration of exogenous insulin. The primary goal of treatment of T1DM in children and adolescents is to maintain near-normoglycemia through intensive insulin therapy, avoid acute complications, and prevent long-term microvascular and macrovascular complications, while facilitating as close to a normal life as possible. Effective insulin therapy must, therefore, be provided on the basis of the needs, preferences, and resources of the individual and the family for optimal management of T1DM. To achieve target glycemic control, the best therapeutic option for patients with T1DM is basal-bolus therapy either with multiple daily injections (MDI) or continuous subcutaneous insulin infusion (CSII). Many formulations of insulin are available to help simulate endogenous insulin secretion as closely as possible in an effort to eliminate the symptoms and complications of hyperglycemia, while minimizing the risk of hypoglycemia secondary to therapy. When using MDI, basal insulin requirements are given as an injection of long- or intermediate-acting insulin analogs, while meal-related glucose excursions are controlled with bolus injections of rapid-acting insulin analogs. Alternatively, CSII can be used, which provides a 24-h preselected but adjustable basal rate of rapid-acting insulin, along with patient-activated mealtime bolus doses, eliminating the need for periodic injections. Both MDI treatment and CSII therapy must be supported by comprehensive education that is appropriate for the individual needs of the patient and family before and after initiation. Current therapies still do not match the endogenous insulin profile of pancreatic β-cells, and all still pose risks of suboptimal control, hypoglycemia, and ketosis in children and adolescents. The safety and success of a prescribed insulin regimen is, therefore, dependent on self-monitoring of blood glucose and/or a continuous glucose monitoring system to avoid critical hypoglycemia and glucose variability. Regardless of the mode of insulin therapy, doses should be adapted on the basis of the daily pattern of blood glucose, through regular review and reassessment, and patient factors such as exercise and pubertal status. New therapy options such as sensor-augmented insulin pump therapy, which integrates CSII with a continuous glucose sensor, along with emerging therapies such as the artificial pancreas, will likely continue to improve safe insulin therapy in the near future.

Short-term administration of pegvisomant improves hepatic insulin sensitivity and reduces soleus muscle intramyocellular lipid content in young adults with type 1 diabetes

CONTEXT

Data on the metabolic effects of GH derived from studies using GH suppression by pharmacological agents may not reflect selective actions.

OBJECTIVE

The purpose of this study was to evaluate the effects of GH antagonism on glucose and lipid metabolism using pegvisomant, a selective GH receptor antagonist in patients with type 1 diabetes (T1D).

DESIGN AND PARTICIPANTS

In a randomized, placebo-controlled, crossover study, 10 young adults with T1D were evaluated at baseline and after 4 weeks of treatment with either 10 mg of pegvisomant or placebo. The assessments included an overnight euglycemic steady state followed by a hyperinsulinemic euglycemic clamp and used glucose and glycerol cold stable isotopes.

OUTCOME MEASURES

Hepatic and peripheral insulin sensitivity (IS), lipid turnover, and intramyocellular lipid (IMCL) were measured.

RESULTS

Compared with placebo, pegvisomant treatment resulted in lower IGF-I levels (P < .001). During the overnight steady state, insulin requirements for euglycemia (P = .019), insulin levels (P = .008), and glucose production rates (Ra) (P = .033) were reduced. During the clamp study, glucose infusion rates (P = .031) increased and glucose Ra (P = .015) decreased whereas glucose disposal rates were unchanged. Free fatty acid levels were similar during the steady state but were lower during the clamp (P = .040) after pegvisomant. Soleus muscle IMCL decreased after treatment (P = .024); however, no change in tibialis anterior muscle was observed.

CONCLUSIONS

The study demonstrates that GH antagonism in T1D results in improved hepatic insulin sensitivity. Lack of consistent changes in free fatty acid levels may suggest a direct effect of GH on IS. Unchanged peripheral IS despite reductions in IMCL indicate that GH-induced alterations in IMCL may not be causally linked to glucose metabolism.

Nonalcoholic fatty liver disease is associated with increased GHBP and reduced GH/IGF-I levels

INTRODUCTION

Nonalcoholic fatty liver disease (NAFLD) has been described in adult GH deficiency syndrome. Furthermore, chronic liver disease can be associated with significant changes in levels of IGF-I, GH-binding protein (GHBP), IGF-binding proteins (IGFBPs) and acid-labile subunit (ALS). However, the effect of liver steatosis on the GHBP production has not been investigated yet.

AIM OF THE STUDY

To explore whether GH secretion and/or levels of IGF-I, IGFBP-3, ALS and GHBP could be altered in obese patients in relation to the presence of liver steatosis.

MATERIALS AND METHODS

A total of 115 obese patients (BMI > 30) were enrolled in the protocol (65 patients with liver steatosis and 50 age- and BMI-matched controls). In all patients, the following parameters were studied: serum levels of glucose, insulin, the HOMA index, IGF-I, GHBP, IGFBP-3, ALS and GH after GHRH and arginine stimulation test.

RESULTS

As expected, patients with NAFLD had blood glucose, insulin, HOMA-R significantly higher than controls, indicating a more severe insulin-resistance state in NAFLD. Furthermore, patients with NAFLD had higher levels of GHBP and IGFBP-3 and lower GH peak and IGF-I levels as compared to controls. No difference was found in ALS levels between the groups. In a multivariate analysis, GHBP was positively associated with hepatic steatosis while IGF-1 was negatively associated with hepatic steatosis.

CONCLUSIONS

This study demonstrates that in patients with NAFLD, the GHBP levels are increased, and that the GH/IGF-I axis is significantly altered probably leading to reduced IGF-I bioavailability at tissue level.

Insulin doses before and one year after pump start: children have a reversed dawn phenomenon

OBJECTIVE

We aimed to investigate the basal rate and bolus doses in children and adolescents at the start of insulin pump therapy and after 1 year of use.

PATIENTS AND METHODS

Case records from 29 children and adolescents were examined. All pumps were started with rapid-acting insulin (Humalog). Patients were aged 13.1 ± 3.9 years, with a diabetes duration of 5.4 ± 4.1 years at pump start. Sixteen pumps were started for high hemoglobin A1c (HbA1c; >8.8%, 73 mmol/mol) and 13 for other reasons.

RESULTS

Basal rates declined in both groups by 20% at 3 days after pump start. The bolus doses were reduced by 25-30% when the indication was high HbA1c and by 15% in the others. After 1 year, there was a significant difference in the basal rate between age groups. The 3-9-year-old age group had higher basal rates during the late evening (10:00 PM-12:00 AM), while the 15-21-year-old age group had higher basal rates in the early morning (3:00 AM-7:00 AM).

CONCLUSIONS

Insulin doses are reduced considerably when starting with a pump in pediatric practice. Younger children needed higher basal rates late in the evening (reversed dawn phenomenon), while older teenagers seem to need an increase in the morning, which may correspond to a true dawn phenomenon.

Effects of growth hormone and free fatty acids on insulin sensitivity in patients with type 1 diabetes

CONTEXT

Because GH stimulates lipolysis, an increase in circulating free fatty acid levels, as opposed to a direct effect of high GH levels, could underlie the development of insulin resistance in type 1 diabetes (T1D). Our aim was to explore the relative contributions of GH and free fatty acids to the development of insulin resistance in patients with T1D.

PATIENTS

Seven (four females, three males) nonobese patients with T1D aged 21-30 yr were studied on four occasions in random order. On each visit, overnight endogenous GH production was suppressed by octreotide. Three 1-h pulses of recombinant human GH (rhGH) or placebo were administered on two visits each. Acipimox, an antilipolytic drug, or a placebo were ingested every 4 h on two visits each. Stable glucose and glycerol isotopes were used to assess glucose and glycerol turnover. The overnight protocol was concluded by a two-step hyperinsulinemic euglycemic clamp on each visit.

MAIN OUTCOME

rhGH administration led to increases in the insulin infusion rate required to maintain euglycemia overnight (P = 0.008), elevated basal endogenous glucose production (P = 0.007), decreased basal peripheral glucose uptake (P = 0.03), and reduced glucose uptake during step 1 of the clamp (P < 0.0001). Coadministration of rhGH and acipimox reversed these effects and suppression of lipolysis in the absence of GH replacement led to further increases in insulin sensitivity.

RESULTS

GH pulses were associated with an increase in endogenous glucose production and decreased rates of peripheral glucose uptake, which was entirely reversed by acipimox. Therefore, GH-driven decreases in insulin sensitivity are mainly determined by the effect of GH on lipolysis.

Feasibility of continuous subcutaneous insulin infusion and daily supplemental insulin glargine injection in children with type 1 diabetes

BACKGROUND

Continuous subcutaneous insulin infusion (CSII) is an effective method of insulin substitution with increased risk of hypoglycemia and diabetic ketoacidosis (DKA) in rare situations. The lack of subcutaneous long-acting insulin and short half-life of serum insulin increases the risk of ketosis and DKA following CSII failure. We evaluated the metabolic effects of CSII with and without daily supplemental long-acting insulin glargine in a group of young children switched to CSII from multiple daily insulin (premeal aspart + glargine) to either CSII plus daily glargine (CSII + G) or CSII therapy.

METHODS

From retrospective clinic data, self-monitored blood glucose (SMBG), hemoglobin A1c (HbA(1c)), hypoglycemic episodes, and body mass index (BMI) were obtained from 12 patients (five girls, seven boys; 7.7 +/- 1.8 years) on CSII + G and 12 age- and gender-matched patients (five girls, seven boys; 7.7 +/- 2.1 years) on CSII with similar baseline HbA(1c) and BMI were reviewed over a 1.0-year period.

RESULTS

The insulin glargine dose in the CSII + G group was 30.6 +/- 12.4% (range, 13.9-53.3%) of daily basal insulin dose. Both groups had similar total daily insulin and bolus:basal insulin at baseline and at 1.0 year. Glycemic control improved in the CSII + G (SMBG, 195.5 +/- 47.3 vs. 156.8 +/- 36.8 mg/dL, P < 0.05; HbA(1c), 8.1 +/- 0.9% vs. 7.4 +/- 0.4%, P < 0.02) and CSII (SMBG, 198.7 +/- 45.7 vs. 161.4 +/- 30.9 mg/dL, P < 0.05; HbA(1c), 8.2 +/- 0.4% vs. 7.7 +/- 0.5%, P < 0.01) groups without significant changes in hypoglycemic episodes and BMI. There were no DKA episodes despite three emergency room visits for hyperglycemia and ketosis due to catheter dislodgement only in the CSII group.

CONCLUSIONS

CSII therapy with or without daily insulin glargine improved glycemic control without changes in the rate of hypoglycemia and DKA, suggesting that this treatment regimen is feasible and may also prevent development of hyperglycemia and ketosis or even DKA.

Normalization of the IGF-IGFBP axis by sustained nightly insulinization in type 1 diabetes

OBJECTIVE

We sought to test the hypothesis that start of insulin glargine with sustained nightly insulin action results in changes in circulating concentrations of IGF-I and IGF binding proteins (IGFBPs) in adolescents with type 1 diabetes-changes that may support improvement of A1C.

RESEARCH DESIGN AND METHODS

Twelve pubertal adolescents with type 1 diabetes and initially on NPH insulin were studied during 12 weeks of intensified treatment with glargine.

RESULTS

Subnormal IGF-I SD scores on NPH (-1.8 +/- 0.4) rapidly increased and remained 54 +/- 9% elevated (P < 0.001) after 12 weeks on glargine. A1C decreased from 8.3 +/- 0.6% to a nadir of 6.9 +/- 0.3% (P = 0.002) at 6 weeks and correlated with changes in IGF-I (r = -0.64, P < 0.05). The increase in IGF-I did not suppress the mean overnight growth hormone (GH) secretion at 6 weeks. The mean overnight IGFBP-1 levels decreased (P = 0.035), supporting the hypothesis that the nightly hepatic insulin action was increased. Circulating IGF-I increased in the absence of changes in both GH secretion and GH receptor numbers (assessed by growth hormone binding protein), indicating that postreceptor mechanisms are involved. IGFBP-3 proteolysis was decreased.

CONCLUSIONS

Increased hepatic insulin action after start of glargine was evident from a decrease in night time IGFBP-1 concentrations. This may improve GH postreceptor signaling, resulting in increased circulating IGF-I. We suggest that even in the absence of changes in GH, increased IGF-I and decreased IGFBP-1 support the improvement of metabolic control.

Growth hormone hypothesis and development of diabetic nephropathy in Type 1 diabetes

In Type 1 diabetes, poor glycemic control is the key predictor for the development of microalbuminuria, an established early marker of overt nephropathy. However, the role of other pathways in the development of diabetic nephropathy may also be important. The growth hormone (GH) hypothesis suggests that the GH-insulin-like growth factor (IGF)-1 axis may play an important role in this disease process. In Type 1 diabetes, the characteristic pattern of GH hypersecretion and low circulating IGF-1 levels results from hepatic GH resistance owing to the lack of portal insulin. Clinical data indicate that high GH and low IGF-1 levels reduce insulin sensitivity and worsen glycemic control. Furthermore, despite hepatic GH resistance, GH receptors at the kidney remain intact. Experimental data show that excess GH stimulates renal GH receptors and, through paracrine IGF-1 production, results in pathophysiological changes consistent with diabetic nephropathy, namely nephromegaly, glomerular hyperfiltration and eventual proteinuria. These abnormalities are reversed by intervention to block or normalize the local effects of GH and IGF-1. Although such data in humans are limited, preliminary trials show that interventions to increase IGF-1 levels and reduce GH hypersecretion improve glycemic control and insulin sensitivity in the short term. However, their effects on early nephropathy and end points, such as the prevalence of end stage renal disease, have yet to be determined.

Increasing urine albumin excretion is associated with growth hormone hypersecretion and reduced clearance of insulin in adolescents and young adults with type 1 diabetes: the Oxford Regional Prospective Study

HYPOTHESIS

We previously described lower insulin-like growth factor I (IGF-I) levels in association with increased microalbuminuria (MA) risk in type 1 diabetic subjects followed from diabetes diagnosis through puberty into adulthood. By inference lower IGF-I levels may be associated with higher GH levels and changes in insulin sensitivity.

METHODS

To test this hypothesis, microalbuminuric subjects (MA+, n = 14) from the same cohort had overnight GH levels measured during euglycaemia (5 mmol/l, 01:00-07:30 h) maintained by a variable rate insulin infusion followed by a 2-step hyperinsulinaemic, euglycaemic clamp study using [6.6 2H2] glucose, and were compared to MA- controls (MA-, n = 14), matched for age (median 19.3 years, range 15.8-30.5), sex, duration of diabetes (11.1 years, range 5.1-16.4).

RESULTS

In MA+ cases GH levels, measured by the Pulsar programme, were higher (baseline; 1.8 +/- 1.4 vs. 0.7 +/- 0.5 ng/ml, P = 0.02, mean; 3.8 +/- 1.3 vs. 2.6 +/- 1.6 ng/ml, P = 0.03, maximum; 16.7 +/- 7.0 vs. 12.3 +/- 5.4, P = 0.02), despite similar HbA1(c) levels (9.8%vs. 9.6%, P = 0.6) and body or truncal fat mass. Fourier transform revealed increased GH pulse amplitude at all periodicities and overnight insulin clearance was reduced (11.7 +/- 6.9 vs. 20.1 +/- 6.5 ml/kg/min, P < 0.02). In multiple regression analysis, urine albumin excretion was associated with higher GH levels and reduced insulin clearance, independent of HbA1(c) and body composition. In female cases (n = 9), dextrose requirements were reduced during the first step of the euglycaemic clamp (1.7 +/- 0.8 vs. 2.7 +/- 1.4, P < 0.05) but no such differences existed in males or in the rate of glucose production or disposal.

CONCLUSION

The development of MA during puberty and young adulthood is associated with higher GH levels and abnormalities in insulin metabolism, particularly in females. These data extend support for our previous findings indicating a role for the GH/IGF-I axis in the pathogenesis of MA.

The Dawn Phenomenon Revisited: Implications for Diabetes Therapy

OBJECTIVE

To summarize current data on the magnitude, prevalence, variability, pathogenesis, and management of the dawn phenomenon in patients with diabetes mellitus.

METHODS

On the basis of the pertinent available literature and clinical experience, we propose a quantitative definition of the dawn phenomenon, discuss potential pathogenic mechanisms, and suggest management options.

RESULTS

The "dawn phenomenon" is a term used to describe hyperglycemia or an increase in the amount of insulin needed to maintain normoglycemia, occurring in the absence of antecedent hypoglycemia or waning insulin levels, during the early morning hours. To be clinically relevant, the magnitude of the dawn increase in blood glucose level should be more than 10 mg/dL or the increase in insulin requirement should be at least 20% from the overnight nadir. Controversy exists regarding the frequency, reproducibility, and pathogenesis of the dawn phenomenon. Approximately 54% of patients with type 1 diabetes and 55% of patients with type 2 diabetes experience the dawn phenomenon when the foregoing quantitative definition is used. The most likely pathogenic mechanism underlying the dawn phenomenon is growth hormone-mediated impairment of insulin sensitivity at the liver and muscles. The exact biochemical pathways involved are unknown. Therapeutic decisions aimed at correcting fasting hyperglycemia should take into account the variability and magnitude of the dawn phenomenon within individual patients. Successful insulinization appears to minimize the effects of the dawn phenomenon. Currently, no subcutaneous depot preparation of insulin exists that is capable of mimicking the basal insulinsecretion of the healthy pancreas.

CONCLUSION

Increases in the bedtime doses of hypoglycemic agents with nighttime peaks in action may correct early morning hyperglycemia but be associated with undesirable nocturnal hypoglycemia. Targeted continuous subcutaneous insulin infusion programming can facilitate the prevention of early morning hyperglycemia in selected patients.

Insulin treatment in children and adolescents

The management of diabetes in children presents a number of challenges. The ideal is to achieve optimal glycaemic control using an insulin regimen that is acceptable to the child and family, which improves glycaemic control, whilst avoiding hypoglycaemia. The paediatric population differ from their adult counterparts in several ways, such as variability of exercise and eating patterns, and the hormonal influences of puberty, which means that the insulin regimen must be tailored to suit an individual child and their family.

CONCLUSION

This review will focus on the particular difficulties of managing diabetes in children and, in particular, the problem of avoiding hypoglycaemia while maintaining adequate glycaemic control.

Frequency of the dawn phenomenon in type 2 diabetes: implications for diabetes therapy

This study was designed to assess the frequency of the dawn phenomenon in patients with type 2 diabetes. A secondary aim was to examine the influence of varying treatment regimens on the frequency of the dawn phenomenon. The dawn phenomenon was defined as a rise in plasma glucose levels of > or = 0.5 mmol/L (10 mg/dL) between 0500 and 0900 h occurring after a growth hormone surge of > or = 5 microg/L. Sixteen subjects (six men, 10 women) with type 2 diabetes were studied overnight on their current mode of therapy in the General Clinical Research Center. Additionally, six of these subjects were restudied in random order after each of the following three therapeutic regimens: (1) 6 weeks of glipizide, (2) 6 weeks of bedtime NPH insulin, and (3) 3 days of intensive insulin therapy with multiple injections of regular insulin followed by assessment during overnight intravenous infusion of insulin. Thus, a total of 34 overnight studies were performed under various treatment conditions to provide an approximate frequency of the dawn phenomenon in type 2 diabetes. Blood was drawn every 30 min between midnight and 0800 h for measurement of glucose, insulin, C-peptide, and growth hormone levels. Additional counterregulatory hormone levels were determined during 24 of the studies, and the integrity of growth hormone secretion in response to insulin-induced hypoglycemia was assessed in 12 of the 16 patients. The subjects were aged 51 +/- 15 years with a body mass index of 31 +/- 5 kg/m(2) and a mean glycosylated hemoglobin of 8.1 +/- 1.2%. The dawn phenomenon occurred in only one of 34 (3%) studies. Moreover, the four different treatment regimens did not affect the frequency of occurrence of the dawn phenomenon. Ten of the 12 patients tested failed to secrete growth hormone in response to insulin-induced hypoglycemia. These data suggest that the dawn phenomenon is unusual in type 2 diabetes. Previously reported high prevalence rates in studies using similar sample size may be attributable to a Biostator-induced artifact. Decisions regarding therapies for type 2 diabetes should not be based on the assumption that the dawn phenomenon routinely causes early morning hyperglycemia.

Therapeutic Potential of Insulin-Like Growth Factor-1 in Patients with Diabetes Mellitus

Insulin-like growth factor-1 (IGF-1) and its receptors share considerable homology with insulin and insulin receptors, and their respective signaling pathways interact at the post receptor level. While the growth hormone (GH)-IGF-1 axis principally regulates tissue growth and differentiation, insulin exerts it primary effects on fuel metabolism. However, these two endocrine systems interact at multiple levels and in diabetes mellitus the GH-IGF-1 axis is grossly disturbed, with increased secretion of GH, reduced plasma levels of IGF-1, and complex tissue-specific changes in IGF binding proteins (IGFBPs). These observations have given rise to the view that GH-IGF-1 axis dysfunction, particularly low plasma levels of circulating IGF-1, probably play a significant role in several aspects of the pathophysiology of diabetes mellitus, including insulin resistance and poor glycemic control, and may also influence the development of microvascular complications. The availability of recombinant human IGF-1 (rhIGF-1; mecasermin), used either alone or in combination with insulin, has led to experimental studies and clinical trials in humans testing these hypotheses. These studies have examined the impact of subcutaneous rhIGF-1 injections on sensitivity and metabolic parameters. In patients with type 1 and 2 diabetes mellitus, insulin sensitivity is significantly improved, insulin requirements are reduced, and glycemic control of dyslipidemia is generally improved in short-term studies. rhIGF-1 is a particularly attractive possibility in patients with type 2 diabetes mellitus, where insulin resistance is the fundamental problem. Some patients with genetic syndromes of severe insulin resistance also benefit from treatment with rhIGF-1, which can bypass blocks in the insulin signaling pathway. The common adverse effects reported for rhIGF-1 are dose-related and include edema, jaw pain, arthralgia, myalgia, hypotension, injection site pain, and less commonly, Bell's palsy and raised intracranial pressure. Although disturbance of the GH-IGF-1 axis participates in the development of diabetic complications, the functional consequences of the complex changes in IGFBP expression at the tissue level are uncertain, and it is not known whether systemic IGF-1 therapy or other manipulations of the GH-IGF-1 axis would be helpful or harmful. Experimentally, IGF-1 has a protective effect on neuropathy, and could find an application in the healing of neuropathic ulcers. The potential benefits of IGF-1 therapy in diabetes mellitus have yet to be realised.

Effects of low-dose recombinant human insulin-like growth factor-I on insulin sensitivity, growth hormone and glucagon levels in young adults with insulin-dependent diabetes mellitus

Despite recent interest in the therapeutic potential of recombinant human insulin-like growth factor-I (rhIGF-I) in the treatment of diabetes mellitus, its mechanism of action is still not defined. We have studied the effects of low-dose bolus subcutaneous rhIGF-I (40 microg/kg and 20 microg/kg) on insulin sensitivity, growth hormone (GH) and glucagon levels in seven young adults with insulin-dependent diabetes mellitus (IDDM) using a randomized double-blind placebo-controlled crossover study design. Each was subjected to a euglycemic clamp (5 mmol/L) protocol consisting of a variable-rate insulin infusion clamp (6:00 PM to 8:00 AM) followed by a two-dose hyperinsulinemic clamp (insulin infusion of 0.75 mU x kg(-1) x min(-1) from 8 to 10 AM and 1.5 mU x kg(-1) x min(-1) from 10 AM to 12 noon) incorporating [6,6 2H2]glucose tracer for determination of glucose production/utilization rates. Following rhIGF-I administration, the serum IGF-I level (mean +/- SEM) increased (40 microg/kg, 655 +/- 90 ng/mL, P < .001; 20 microg/kg, 472 +/- 67 ng/mL, P < .001; placebo, 258 +/- 51 ng/mL). Dose-related reductions in insulin were observed during the period of steady-state euglycemia (1 AM to 8 AM) (40 microg/kg, 48 +/- 5 pmol/L, P = .01; 20 microg/kg, 58 +/- 8 pmol/L, P = .03; placebo, 72 +/- 8 pmol/L). The mean overnight GH level (40 microg/kg, 9.1 +/- 1.4 mU/L, P = .04; 20 microg/kg, 9.6 +/- 2.0 mU/L, P = .12; placebo, 11.3 +/- 1.7 mU/L) and GH pulse amplitude (40 microg/kg, 18.8 +/- 2.9 mU/L, P = .04; 20 microg/kg, 17.0 +/- 3.4 mU/L, P > .05; placebo, 23.0 +/- 3.7 mU/L) were also reduced. No differences in glucagon, IGF binding protein-1 (IGFBP-1), acetoacetate, or beta-hydroxybutyrate levels were found. During the hyperinsulinemic clamp conditions, no differences in glucose utilization were noted, whereas hepatic glucose production was reduced by rhIGF-I 40 microg/kg (P = .05). Our data demonstrate that in subjects with IDDM, low-dose subcutaneous rhIGF-I leads to a dose-dependent reduction in the insulin level for euglycemia overnight that parallels the decrease in overnight GH levels, but glucagon and IGFBP-1 levels remain unchanged. The decreases in hepatic glucose production during the hyperinsulinemic clamp study observed the following day are likely related to GH suppression, although a direct effect by rhIGF-I cannot be entirely discounted.

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.

Recombinant human insulin-like growth factor-I abolishes changes in insulin requirements consequent upon growth hormone pulsatility in young adults with type I diabetes mellitus

To investigate whether recombinant human insulin-like growth factor-I (rhIGF-I) has direct effects on the insulin requirement to maintain euglycemia independent of the growth hormone (GH) level, nine subjects with insulin-dependent diabetes mellitus ([IDDM] seven females; median (range) age, duration of diabetes, and hemoglobin A1C [HbA1C], 16.9 (12.5 to 21.9) years, 11.8 (4.6 to 16.8) years, and 9.8% (7.9% to 14.1%), respectively) underwent two euglycemic studies (6:00 PM to 8:00 AM) after double-blind subcutaneous administration of rhIGF-I/placebo (40 microg/kg). Octreotide infusion (300 ng/kg/h) suppressed endogenous GH, and three identical discrete GH pulses were infused on both nights. Variable-rate insulin infusion maintained euglycemia. Samples were taken every 15 minutes (glucose and GH), 30 minutes (insulin and intermediate metabolites), and 60 minutes (IGF-I and nonesterified fatty acids [NEFA]). Variables were analyzed during the steady-state period of euglycemia (4:00 to 8:00 AM). Data are expressed as the mean +/- SEM. The insulin infusion rate and free-insulin level were both significantly reduced after rhIGF-I administration (0.13 +/- 0.03 v placebo 0.23 +/- 0.05 mU/kg/min, P = .04, and 8.4 +/- 1.3 v placebo 12.1 +/- 1.4 mU/L, P = .03, respectively). GH pulse-related changes in the insulin requirement observed after placebo were not present after rhIGF-I. Glucagon levels were equally suppressed on both nights. Insulin clearance was not altered after rhIGF-I administration. NEFA and ketone levels also were not different on the 2 nights. In conclusion, in adolescents and young adults with diabetes, rhIGF-I administration directly affected insulin requirements independent of GH levels, but had no effect on fatty acid or ketone levels. This difference is related to the abolition of changes in the insulin requirement after GH pulses, and would suggest a complex interaction between GH and IGF-I on insulin action.

Effects of cholinergic blockade on nocturnal thyrotropin and growth hormone (GH) secretion in type I diabetes mellitus: further evidence supporting somatostatin's involvement in GH suppression

To investigate the influence of cholinergic pathways on somatostatin (SS) tone in type I diabetes mellitus, we studied the effect of the muscarinic receptor antagonist pirenzepine ([PZP] 100 mg orally) on spontaneous nocturnal growth hormone (GH) and thyrotropin (TSH) secretion and on their response to GH-releasing hormone (GHRH) in the morning in a group of nine insulin-dependent diabetic patients with poor diabetic control. When the nocturnal period was divided into two phases (11:00 PM to 2:30 AM and 3:00 AM to 6:00 AM), both GH and TSH mean concentrations during the first phase were higher than those seen in the second half of the night following placebo administration (GH, 13.4 +/- 1.1 v 4.15 +/- 0.9 ng/mL, P < .001; TSH, 1.9 +/- 0.21 v 1.57 +/- 0.1 microU/mL, P < .05). Pretreatment with PZP induced a significant reduction of GH secretion (3.17 +/- 1.1 v 13.4 +/- 1.1 ng/mL, P < .001) and TSH secretion (1.61 +/- 0.21 microU/mL, P < .05) in the first phase of the night, accounting for a 64% and 11% reduction in the GH and TSH nocturnal peak, respectively. PZP reduced the GH response to GHRH in the morning (17.9 +/- 2.7 v 36.7 +/- 6.3 ng/mL, P < .05), but did not induce any change in TSH values at that time. A positive relationship (r = .73, P < .01) was observed between the percent reduction of the GH response to GHRH and that of the nocturnal GH peak following PZP administration. PZP caused a significant reduction in glucose levels during the second phase of the night (6.4 +/- 0.92 v 9.81 +/- 0.85 mmol/L, P < .05). These results demonstrate that administration of PZP reduces GH and TSH secretion, providing further support for the involvement of SS in the inhibition of GH secretion induced by cholinergic antagonists in type I diabetics. The inhibitory effect of PZP on GHRH-induced GH secretion may help to predict nocturnal GH behavior following administration of the drug.

Insulin-like growth factor-I in man enhances lipid mobilization and oxidation induced by a growth hormone pulse

Growth hormone (GH) secretion is suppressed during insulin-like growth factor-I (IGF-I) administration. The aim of the study was to examine whether IGF-I alters the metabolic response to a GH pulse. Seven healthy male subjects (age 27 +/- 4 years, BMI 21.8 +/- 1.7 kg/m2) were treated with NaCl 0.9% (saline) or IGF-I (8 micrograms.kg-1.h-1) for 5 days by continuous subcutaneous infusion in a randomized, crossover fashion while receiving an isocaloric diet (30 kcal.kg-1.day-1). On the third treatment day an intravenous bolus of 0.5 U GH was administered. Forearm muscle metabolism was examined by measuring arterialized and deep venous blood samples, forearm blood flow by occlusion plethysmography and substrate oxidation by indirect calorimetry. IGF-I treatment significantly reduced insulin concentrations by 80% (p < 0.02) and C-peptide levels by 78% (p < 0.02), as assessed by area under the curve. Non-esterified fatty acid (NEFA), glycerol and 3-OH-butyrate levels were elevated and alanine concentration decreased. Forearm blood flow rose from 2.10 +/- 0.43 (saline) to 2.79 +/- 0.37 ml.100ml-1. min-1 (IGF-I) (p < 0.02). GH-pulse: 10 h after i.v. GH injection serum GH peaked at 40.9 +/- 7.4 ng/ml. GH did not influence circulating levels of total IGF-I, C-peptide, insulin or glucose, but caused a further increase in NEFA, glycerol and 3-OH-butyrate levels, indicating enhanced lipolysis and ketogenesis. This effect of GH was much more pronounced during IGF-I: NEFA rose from 702 +/- 267 (saline) and 885 +/- 236 (IGF-I) to 963 +/- 215 (saline) (p < 0.05) and 1815 +/- 586 mumol/l (IGF-I) (p < 0.02), respectively; after 5 h, 3-OH-butyrate rose from 242 +/- 234 (saline) and 340 +/- 280 (IGF-I) to 678 +/- 638 (saline) (p < 0.02) and 1115 +/- 578 mumol/l (IGF-I) (p < 0.02) respectively. After injection of GH, forearm uptake of 3-OH-butyrate was markedly elevated only in the subjects treated with IGF-I: from 44 +/- 195 to 300 +/- 370 after 20 min (p < 0.03) and to 287 +/- 91 nmol.100 ml-1. min-1 after 120 min (p < 0.02). In conclusion, the lipolytic and ketogenic response to GH was grossly enhanced during IGF-I treatment, and utilization of ketone bodies by skeletal muscle was increased.

Reduced growth hormone secretion improves insulin sensitivity in adolescent girls with type 1 diabetes

The aims of the present study were to compare nocturnal growth hormone (GH) secretion, insulin requirements and insulin sensitivity on two occasions in six adolescent girls with type 1 diabetes when the GH secretion was reduced one night by an oral dose of 100 mg of pirenzepine at bedtime. The mean nocturnal intravenous insulin infusion required to maintain a normal constant blood glucose concentration between 24:00 and 07:00 was 53% higher during the night on placebo (p = 0.0212). During the night on pirenzepine, the serum GH area under the curve (AUC) was reduced in all patients to a mean concentration which was 50.1% (15-78%) of that during the night without pirenzepine (p = 0.0036). The nocturnal urinary GH excretion was also reduced in all of the investigated patients (p = 0.0229). Insulin sensitivity in the morning, measured by the euglycaemic hyperinsulinaemic glucose clamp, increased significantly from 115 +/- 51 mg m-2 min-1 after the night on placebo to 205 +/- 67 mg m-2 min-1 after the night on pirenzepine (p = 0.0161). No side-effects were observed during the pirenzepine night. Negative correlations were found between the nocturnal serum GH AUC and the insulin-stimulated glucose metabolism (r = -0.65, p = 0.0241) and between the nocturnal urinary GH excretion and the insulin-stimulated glucose metabolism (r = -0.77, p = 0.0054). In conclusion, the present study shows a relation between GH secretion and insulin resistance in adolescent girls with type 1 diabetes. The administration of pirenzepine acutely reduces GH secretion and improves insulin sensitivity.

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 < 4-8 ml) 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 +/- 0.99) and daily 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 IGF-I at 0700 h. 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 +/- 9 micrograms/l at 0700 h; study B, from 10 +/- 1 at 2100 to 64 +/- 14 micrograms/l at 0700 h) whilst insulin levels fell from 47 +/- 5 at 2200 to 16 +/- 2 mU/l at 0700 h (study A) and from 45 +/- 5 at 2000 to 14 +/- 2 mU/l at 0700 h (study B). Glucose levels fell from 16.0 +/- 1.0 to 9.3 +/- 0.9 mmol/l at 0400 h, 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/l; 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 +/- 90.3 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/l; group 3, 15.3 +/- 1.2 mU/l). Serum IGF-I levels were not different (study A, 203 +/- 12 micrograms/l; study B, 218 +/- 13 micrograms/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.

The effects of repeated daily recombinant human insulin-like growth factor I administration in adolescents with type 1 diabetes

Reduced insulin-like growth factor bioactivity has been linked to poor metabolic control and growth hormone hypersecretion in adolescents with Type 1 diabetes. The safety and efficacy of recombinant human insulin-like growth factor I administered subcutaneously in a dose of 40 micrograms kg-1 for 28 days was studied in a group of 6 adolescent male subjects with Type 1 diabetes (aged 13.6-19.4 years, puberty stage 3-5). After a 4-week run-in period (week -4 day 0) recombinant human insulin-like growth factor I was administered for 4 weeks (day 0 to week +4) before a run-out of a further 4 weeks duration (week +4 to +8). HbA1c levels were measured throughout the study and overnight profiles were undertaken to study levels of insulin-like growth factor 1, insulin-like growth factor binding protein-3, and growth hormone concentrations (week -1, day 0, and week +4). The injections were well tolerated and hypoglycaemia was not problematic at any stage of the study. Recombinant insulin-like growth factor I administration appeared to lead to a sustained increase in insulin-like growth factor I levels (week -1; 198 +/- 16 ng ml-1, week +4; 422 +/- 18 ng ml-1, mean +/- SEM; p = 0.03). Insulin-like growth factor binding protein-3 concentrations (n = 6) increased in 5 subjects (week -1; 4.5 +/- 0.3 micrograms ml-1, week +4; 5.1 +/- 0.4 micrograms ml-1) and mean overnight growth hormone decreased (week -1; 14.0 +/- 3.1 mUI-1, week +4; 7.6 +/- 1.7 mUI-1) during the period of study but these differences were not statistically significant. HbA1c levels fell significantly at the time of rhIGF-I administration (day 0; 10.4 +/- 1.9% vs week +4; 9.4 +/- 1.9%; p = 0.03) despite a reduction in subcutaneous isophane insulin dose from 0.50 +/- 0.02 U kg-1 to 0.41 +/- 0.02 U kg-1 (p = 0.03). There was no significant change in biochemical and haematological indices, glomerular filtration rate or urinary albumin excretion. The restoration of IGF-I levels in adolescents with Type 1 diabetes may have a beneficial impact on glycaemic control.

Insulin-like growth factors (IGFs) and IGF-I treatment in the adolescent with insulin-dependent diabetes mellitus

Insulin-dependent diabetes mellitus (IDDM) during adolescence is associated with complex derangements of the growth hormone (GH)/insulin-like growth factor (IGF) axis. Despite GH hypersecretion, IGF-I levels and IGF bioactivity are reduced. The diabetogenic effects of GH are well established, and GH hypersecretion has been implicated in the deterioration in glycemic control during adolescence and in the development of microangiopathy. Insulin deficiency or reduced portal delivery of insulin plays a central role in the development of these abnormalities, and although continuous subcutaneous insulin delivery may improve plasma IGF-I levels, it does not necessarily suppress GH levels. Recombinant IGF-I has been proposed as an adjunct to conventional insulin therapy, as restoring circulating IGF-I levels might lead to GH suppression. Placebo-controlled studies have shown a consistent reduction in GH secretion and related improvements in insulin sensitivity following a single subcutaneous IGF-I injection (40 micrograms/kg). Repeated daily subcutaneous IGF-I administration for 1 month resulted in a sustained increase in IGF-I levels, as well as a reduction in GH secretion and insulin requirements. There was no increase in hypoglycemia or other adverse effects. Recombinant IGF-I used in conjunction with insulin may therefore provide an additional approach to the management of IDDM during adolescence, allowing correction of abnormalities in the GH/IGF axis and leading to improved control and, hence, reduced risk of long-term complications. However, this hypothesis needs to be rigorously tested in long-term placebo-controlled studies.

Menstrual irregularities are more common in adolescents with type 1 diabetes: association with poor glycaemic control and weight gain

Ovarian function in post-menarchal girls with Type 1 diabetes was evaluated. Menstrual histories from 24 adolescents with Type 1 diabetes were compared with those from 24 age and sex matched controls. A fasting blood sample was obtained from subjects with Type 1 diabetes for the measurement of ovarian and adrenal sex hormones, LH and FSH, glucose and insulin, insulin-like growth factor-I (IGF-I), and insulin-like growth factor binding protein-1 (IGFBP-1); and an ovarian ultrasound scan was performed. Menstrual irregularity was more prevalent in patients with Type 1 diabetes than controls (54% vs 21%, p < 0.01) and their mean body mass index (BMI) was greater (22.3 +/- 0.5 (+/- SEM) vs 20.7 +/- 0.6 kg m-2, p < 0.05). Subjects with Type 1 diabetes with irregular menses (when compared with diabetic subjects with a regular cycle) had a significantly higher HbA1 (12.8 +/- 0.4 vs 10.5 +/- 0.5%, p < 0.01) and BMI (23.2 +/- 0.6 vs 21.4 +/- 0.6 kg m-2, p < 0.05) associated with a lower sex hormone binding globulin (SHBG) (37.2 +/- 4.0 vs 52.6 +/- 4.0 nmol l-1, p < 0.025) and IGF-I (1.4 +/- 0.2 vs 2.2 +/- 0.2 mUI-1, p < 0.025) and a higher LH:FSH ratio (2.6 +/- 0.5 vs 1.4 +/- 0.2, p < 0.05). Polycystic ovarian changes were identified in 10/13 (77%) of these patients with an irregular cycle. Menstrual irregularity is common in post-menarchal girls with Type 1 diabetes and is associated with poor glycaemic control and weight gain. The apparent high incidence of polycystic ovarian change requires further investigation.

The frequency and amplitude of growth hormone secretory episodes as determined by deconvolution analysis are increased in adolescents with insulin dependent diabetes mellitus and are unaffected by short-term euglycaemia

OBJECTIVE

High overnight plasma growth hormone (GH) levels in insulin-dependent diabetes mellitus (IDDM) are reflected in both an increase in the GH pulse amplitude and elevated baseline GH concentrations. To determine whether these are a result of an increase in GH secretory episodes, we undertook deconvolution analysis of overnight GH profiles using previously determined half-life data.

DESIGN

Deconvolution of overnight GH profiles (2000-0800 h) was undertaken from normal and diabetic adolescents (either on their usual insulin regime (n = 15), during overnight euglycaemic clamp using a variable rate insulin infusion (n = 29), or during clamp plus 100 mg pirenzepine to suppress endogenous GH (n = 7)).

PATIENTS

Thirty-five normal and 29 diabetic adolescents of both sexes at all stages of puberty.

MEASUREMENTS

GH secretory rates were calculated from deconvolution analysis, and Fourier transformation was increased mean overnight GH secretion when analysed by sex and by puberty stage compared to normal subjects; overnight GH secretion median (range) of diabetic group 1.88 (0.56-3.81) mU/min; control group 0.62 (0.32-1.92) mU/min (P < 0.001). Fourier transform analysis of these secretory episodes showed greater pulse frequency in the diabetics with dominant pulse periodicity of 90 minutes compared with 135 minutes in normal subjects. During overnight euglycaemia, mean +/- SEM overnight GH secretory rates were comparable to subjects' usual regime night (1.82 +/- 0.33 vs 1.91 +/- 0.37 mU/min) and there was no change in the dominant pulse periodicity of 90 minutes. Pirenzepine administration in diabetic subjects significantly reduced overnight GH secretion from 1.57 +/- 0.19 to 0.71 +/- 0.80 mU/min (P < 0.001) showing a median (range) reduction of 63 (9.3-82.8)% when compared to the subjects' clamp night. However, dominant pulse periodicity was not altered by pirenzepine administration, and remained at 90 minutes.

CONCLUSION

In patients with insulin-dependent diabetes mellitus there is an increase in both the amplitude and frequency of pulsatile GH secretion compared to normal subjects, which is not affected by maintenance of overnight normoglycaemia. The anticholinergic drug pirenzepine appears to suppress the amplitude of GH pulse secretion but has no effect on frequency.

Contrasting metabolic effects of continuous and pulsatile growth hormone administration in young adults with type 1 (insulin-dependent) diabetes mellitus

Plasma growth hormone profiles in adolescents with Type 1 (insulin-dependent) diabetes mellitus are characterized by both increases in pulse amplitude and higher baseline concentrations. To determine which of these abnormalities adversely affect metabolic control, we studied six young adults overnight on three occasions. On each night somatostatin (50-100 micrograms.m2-1.h-1) and glucagon (1 ng.kg-1.min-1) were infused continuously and 18 mU/kg of growth hormone was given as either: three discrete pulses of 6 mU.kg-1.h-1 at 180-min intervals or a 12-h infusion (1.5 mU.kg-1.h-1) or buffer solution only on a control night. Euglycaemia was maintained by an insulin-varying clamp. Blood samples were taken every 15 min for glucose and growth hormone and every hour for intermediate metabolites and non-esterified fatty acids. Comparable normoglycaemic conditions were achieved on all three nights. Growth hormone levels achieved (mean +/- SEM) on study nights were: 32.8 +/- 2.2 mU/l (peak level during growth hormone pulses); 9.8 +/- 0.8 mU/l (continuous growth hormone) and 1.1 +/- 0.3 mU/l (control level). Pulsatile growth hormone administration led to an increase in insulin requirements (mean +/- SEM: 0.17 +/- 0.03 vs control 0.09 +/- 0.01 mU.kg-1.min-1, p less than 0.05) whereas insulin requirements following continuous growth hormone administration were unchanged. Cross-correlation confirmed an increase in insulin requirements occurring 135 min after a growth hormone pulse (r = 0.21, p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Puberty and insulin-dependent diabetes mellitus

Puberty and IDDM interact at many different levels, each affecting the other. Pediatricians, diabetologists, and patients with IDDM must be aware of these interactions and be prepared to adjust their management of IDDM accordingly. Glycemic control in the young prepubertal patient has not been associated with the development of subsequent diabetic microvascular disease. However, extremely tight glycemic control (percent HbA1 in the nondiabetic range) may expose patients to more severe and more frequent hypoglycemic episodes. This may be particularly detrimental for the very young (less than age 3 years) patient whose brain growth and myelinization has not yet been completed. Glycemic control must be maintained in the prepubertal diabetic patient to ensure normal physical and psychological growth, to avoid hospitalizations, and to allow participation in school and other age-appropriate activities. During puberty, health-care professionals and patients should anticipate more difficulty in maintaining glycemic control. Insulin doses commonly need to be increased, sometimes dramatically. Timing of insulin injections will frequently need to be adjusted to blunt the dawn phenomenon. Patients should be allowed to give themselves additional doses of regular insulin (5% to 10% of their total daily dose) when their blood-sugar levels are intermittently elevated to blunt the increased variability in blood-sugar levels seen during puberty. The use of supplemental regular insulin to correct intermittent hyperglycemia is preferable to withholding food in the adolescent patient, since overzealous food restriction can in itself lead to problems with linear growth and pubertal development.(ABSTRACT TRUNCATED AT 250 WORDS)

Impact of increased growth hormone secretion on carbohydrate metabolism in adolescents with diabetes

Growth hormone (GH) and fasting insulin concentrations rise during puberty in normal subjects. Any increase in GH secretion in adolescents with insulin-dependent diabetes mellitus (IDDM) might be expected to lead to further insulin resistance and metabolic disturbance. Despite the high incidence of delayed growth in IDDM, the relationship between GH, insulin-like growth factor I (IGF-I) and IGF binding protein 1 (IGFBP-1) has not been clearly established. Twenty-six adolescents with IDDM and 34 healthy siblings underwent measurement of their overnight GH secretory profiles (20.00-08.00 hours, 15-minute sampling). The diabetic subjects were studied either on their normal insulin regimen (n = 15) or during a euglycaemic clamp (n = 26). A second clamp study was undertaken (n = 7) with addition of pirenzepine to suppress GH secretion. GH profiles in the diabetic subjects were characterized by increases in both pulse amplitude and baseline GH concentrations. Deconvolution analysis also revealed an increase in the frequency of GH secretory episodes. In the subjects with diabetes, a direct link between the dawn rise in insulin requirements, increased concentrations of beta-hydroxybutyrate and the elevated concentrations of GH was established. These abnormalities were reversed by the suppression of GH pulse amplitude following pirenzepine. Serum IGF-I concentrations and IGF-I bioactivity in the diabetic subjects were low and were positively correlated with mean GH concentrations. In conclusion, well controlled adolescents with IDDM show persisting abnormalities of GH, beta-hydroxybutyrate and IGF-I despite normoglycaemia. The role of inappropriate insulin delivery in the development of these abnormalities is discussed.