Regulation of insulin-like growth factor binding protein-1 (IGFBP-1) in insulin-dependent diabetes mellitus. Effects of hyperglycaemia and insulin

Our Scientific Journey through the Ups and Downs of Blood Glucose Control in the ICU

This article tells the story of our long search for the answer to one question: Is stress hyperglycemia in critically ill patients adaptive or maladaptive? Our earlier work had suggested the lack of hepatic insulin effect and hyperglycemia as jointly predicting poor outcome. Therefore, we hypothesized that insulin infusion to reach normoglycemia, tight glucose control, improves outcome. In three randomized controlled trials (RCTs), we found morbidity and mortality benefit with tight glucose control. Moving from the bed to the bench, we attributed benefits to the prevention of glucose toxicity in cells taking up glucose in an insulin-independent, glucose concentration gradient-dependent manner, counteracted rather than synergized by insulin. Several subsequent RCTs did not confirm benefit, and the large Normoglycemia in Intensive Care Evaluation-Survival Using Glucose Algorithm Regulation, or "NICE-SUGAR," trial found increased mortality with tight glucose control associated with severe hypoglycemia. Our subsequent clinical and mechanistic research revealed that early use of parenteral nutrition, the context of our initial RCTs, had been a confounder. Early parenteral nutrition (early-PN) aggravated hyperglycemia, suppressed vital cell damage removal, and hampered recovery. Therefore, in our next and largest "TGC-fast" RCT, we retested our hypothesis, without the use of early-PN and with a computer algorithm for tight glucose control that avoided severe hypoglycemia. In this trial, tight glucose control prevented kidney and liver damage, though with much smaller effect sizes than in our initial RCTs without affecting mortality. Our quest ends with the strong recommendation to omit early-PN for patients in the ICU, as this reduces need of blood glucose control and allows cellular housekeeping systems to play evolutionary selected roles in the recovery process. Once again, less is more in critical care.

Dysregulated growth hormone-insulin-like growth factor-1 axis in adult type 1 diabetes with long duration

CONTEXT

In type 1 diabetes (T1D), dysregulation of the GH-IGF-1 axis has been reported. Whether this is related to upper extremity impairments (UEI) is unknown.

OBJECTIVE

Examine differences in GH-IGF-1 axis between T1D on subcutaneous insulin treatment and matched controls without diabetes and possible associations between GH-IGF-1 axis and UEI.

DESIGN

Cross-sectional population-based study. Patients with T1D, onset <35 years, duration ≥ 20 years, <67 years old and controls were invited to answer questionnaires and take blood samples.

SUBJECTS

A total of 605 patients with T1D and 533 controls accepted to participate.

OUTCOMES

Fasting levels of IGF-1, IGF-1 Z-score, IGFBP-1, IGFBP-3, C-peptide, GH and UEI.

RESULTS

Patients with T1D had lower IGF-1 and IGFBP-3 and higher IGFBP-1 and GH than controls. The difference in IGF-1 persisted with age. Insulin dose was associated with increasing IGF-1 Z-score but even at a very high insulin dose (>1U/kg) IGF-1 Z-score was subnormal compared to controls. IGF-1 Z-score was unaffected by glycaemic control (HbA1c) but increased with residual insulin secretion, (C-peptide 1-99 pmol/L). IGFBP-1 was associated with fasting blood glucose, negatively in controls and positively in patients with T1D probably reflecting insulin resistance and insulin deficiency, respectively. There was no association between lower IGF-1 Z-score and UEI in T1D.

CONCLUSION

In adult T1D with fair glycaemic control, the GH-IGF-1 axis is dysregulated exhibiting GH resistance, low IGF-1 and elevated IGFBP-1. Subcutaneous insulin cannot normalize these changes while endogenous insulin secretion has marked effects on IGF-1 pointing to a role of portal insulin.

Short-term effects of NPH insulin, insulin detemir, and insulin glargine on the GH-IGF1-IGFBP axis in patients with type 1 diabetes

OBJECTIVE

Insulin regulates the GH-IGF1 axis. Insulin analogs differ from human insulin in receptor affinity and possibly liver accessibility. Therefore, we compared the GH-IGF1 axis response with human NPH insulin, insulin detemir, and insulin glargine in patients with type 1 diabetes (T1D).

METHODS

A total of 17 patients (seven were women) with T1D (age of 42 (24-63) years (mean and range), BMI of 24.7 (19.5-28.3) kg/m(2), HbA1c of 7.2 (6.3-8.0) % (55 (45-64) mmol/mol), T1D duration of 26 (8-45) years) were studied using a randomized, three-period crossover design. Patients received s.c. injections of equal, individual doses of NPH, detemir, and glargine at 1800 h. Plasma glucose, serum total IGF1, bioactive IGF, IGF-binding protein (IGFBPs), and GH were measured hourly for 14 h post-injection.

RESULTS

When compared with the area under the curve (AUC) following NPH and glargine, detemir resulted in the lowest 6-14 h AUC (mean and range) of IGFBP1 (1518 (1280-1800)) vs 1621 (1367-1922) vs 1020 (860-1210) μg/l×h) and GH (17.1 (14.1-20.6) vs 15.4 (12.7-18.6) vs 10.2 (8.5-12.3) μg/l×h), but in the highest AUC of bioactive IGF (3.8 (3.5-4.2) vs 3.7 (3.4-4.0) vs 4.4 (4.1-4.8) μg/l×h) (all P<0.01). These differences were unrelated to plasma glucose. By contrast, profiles of total IGF1, IGFBP2, and IGFBP3 were comparable.

CONCLUSIONS

Independent of plasma glucose, a single dose of detemir caused larger suppression in serum IGFBP1 than NPH and glargine, whereas bioactive IGF was higher, thereby explaining the lower GH levels. Thus, detemir appears to be more liver specific than NPH insulin and glargine.

Sleeping during the day: effects on the 24-h patterns of IGF-binding protein 1, insulin, glucose, cortisol, and growth hormone

BACKGROUND

Disturbed sleep is a major risk factor for metabolic disturbances, including type 2 diabetes, but the involved mechanisms are still poorly understood. We investigated how an acute shift of sleep to the daytime affected IGF-binding protein 1 (IGFBP1), which is a risk factor for diabetes.

METHODS

Seven healthy men (age, 22-32 years) participated in a night sleep condition (sleep 2300-0700 h) and a day sleep condition (0700-1500 h) with hourly blood samples taken for 25 h (starting at 1900 h) and isocaloric meals every 4th hour awake. The blood samples were analyzed for IGFBP1, insulin, GH, glucose, and cortisol.

RESULT

The acute shift of sleep and meal timing (to 8 h) shifted the 24-h patterns of IGFBP1, glucose, insulin, and GH to a similar degree. However, the day sleep condition also resulted in elevated levels of IGFBP1 (area under curve (AUC)+22%, P<0.05), and reduced glucose levels (AUC-7%, P<0.05) compared with nocturnal sleep. Sleeping during the day resulted in elevated cortisol levels during early sleep and reduced levels in late sleep, but also in increased levels the subsequent evening (P's<0.05).

CONCLUSION

Sleep-fasting seems to be the primary cause for the elevation of IGFBP1, irrespective of sleep timing. However, sleeping during the day resulted in higher levels of IGFBP1 than nocturnal sleep, suggesting altered metabolism among healthy individuals, which may have implications for other groups with altered sleep/eating habits such as shift workers. Moreover, sleep and meal times should be accounted for while interpreting IGFBP1 samples.

Residual beta-cell function more than glycemic control determines abnormalities of the insulin-like growth factor system in type 1 diabetes

The GH-IGF-I axis is disturbed in patients with type 1 diabetes. Our aim was to investigate whether abnormalities are found in patients in very good glycemic control and, if so, to estimate the role of residual beta-cell function. Patients with hemoglobin A1c (HbA1c) less than 6% (reference range, 3.6-5.4%) were selected for the study. Twenty-two men and 24 women, aged 41.3 +/- 13.8 yr (mean +/- SD), with a diabetes duration of 17.8 +/- 14.6 yr participated. Healthy controls (15 women and nine men), aged 41.3 +/- 13.0 yr, were also studied. Overnight fasting serum samples were analyzed for HbA1c, C peptide, free and total IGFs, IGF-binding proteins (IGFBPs), GH-binding protein, and IGFBP-3 proteolysis. HbA1c was 5.6 +/- 0.5% in patients and 4.4 +/- 0.3% in controls. Total IGF-I was 148 +/- 7 microg/liter in patients and 178 +/- 9 microg/liter in controls (P < 0.001). Free IGF-I, total IGF-II, IGFBP-3, and GH-binding protein were lower, whereas IGFBP-1, IGFBP-1-bound IGF-I, and IGFBP-2 were elevated compared with control values. Patients with detectable C peptide (> or =100 pmol/liter) had higher levels of total IGF-I, free IGF-I, and total IGF-II and lower levels of IGFBP-1 and IGFBP-2 than those with an undetectable C peptide level despite having identical average HbA1c. IGFBP-3 proteolysis did not differ between patients and controls. Despite very good glycemic control, patients with type 1 diabetes and no endogenous insulin production have low free and total IGF-I. Residual beta-cell function, therefore, seems more important for the disturbances in the IGF system than good metabolic control per se, suggesting that portal insulin delivery is needed to normalize the IGF system.

Splanchnic exchange of insulin-like growth factor binding protein-1 (IGFBP-1), IGF-I and acid-labile subunit (ALS) during normo- and hyper-insulinaemia in healthy subjects

OBJECTIVE

The main source of circulating IGF-I, insulin like growth factor binding protein-1 (IGFBP-1) and acid-labile subunit (ALS) is considered to be the liver, but their production rates have not been determined in healthy individuals. Thus, the splanchnic exchange of IGFBP-1, IGF-I, ALS and glucose were studied.

STUDY DESIGN

In five overnight fasting healthy, normal weight men (mean age 29 +/- 1 years) blood samples were taken from a hepatic vein, a brachial artery and a peripheral vein in the basal state and during 3 h i.v. infusion of insulin (1.0 mU/kg/min). Normoglycaemia was maintained with a variable glucose infusion and splanchnic blood flow was determined using a constant rate indicator infusion technique.

RESULTS

The basal net splanchnic glucose output amounted 0.96 +/- 0. 09 mmol/min and the splanchnic production of IGFBP-1 was 7 +/- 2 microg/min. There was a net splanchnic uptake of IGF-I (7 +/- 2 microg/min) in the basal state, while no significant splanchnic exchange of ALS was found. During the insulin infusion, insulin concentration increased from 78 +/- 12 to 660 +/- 30 pmol/l, resulting in a complete inhibition of splanchnic glucose production after 40 min of infusion. Splanchnic IGFBP-1 production rose initially to 13 +/- 4 microg/min (P < 0.05) and then gradually decreased and was completely inhibited at 180 min (P < 0.05). Insulin infusion influenced neither ALS nor IGF-I splanchnic exchange.

CONCLUSION

Splanchnic production of IGFBP-1 in the basal state was demonstrated and it is completely inhibited after 180 min of hyperinsulinaemia. In contrast to what is generally held, there was no net splanchnic production of IGF-I in the basal state or during insulin stimulation.