Effects of dexamethasone on glucose-induced insulin and proinsulin release in low and high insulin responders

Understanding Insulin in the Age of Precision Medicine and Big Data: Under-Explored Nature of Genomics

Insulin is amongst the human genome's most well-studied genes/proteins due to its connection to metabolic health. Within this article, we review literature and data to build a knowledge base of Insulin (INS) genetics that influence transcription, transcript processing, translation, hormone maturation, secretion, receptor binding, and metabolism while highlighting the future needs of insulin research. The INS gene region has 2076 unique variants from population genetics. Several variants are found near the transcriptional start site, enhancers, and following the INS transcripts that might influence the readthrough fusion transcript INS-IGF2. This INS-IGF2 transcript splice site was confirmed within hundreds of pancreatic RNAseq samples, lacks drift based on human genome sequencing, and has possible elevated expression due to viral regulation within the liver. Moreover, a rare, poorly characterized African population-enriched variant of INS-IGF2 results in a loss of the stop codon. INS transcript UTR variants rs689 and rs3842753, associated with type 1 diabetes, are found in many pancreatic RNAseq datasets with an elevation of the 3'UTR alternatively spliced INS transcript. Finally, by combining literature, evolutionary profiling, and structural biology, we map rare missense variants that influence preproinsulin translation, proinsulin processing, dimer/hexamer secretory storage, receptor activation, and C-peptide detection for quasi-insulin blood measurements.

Medical treatment of Cushing's disease with concurrent diabetes mellitus

Cushing's disease (CD) is a severe endocrine disorder characterized by chronic hypercortisolaemia secondary to an overproduction of adrenocorticotropic hormone (ACTH) by a pituitary adenoma. Cortisol excess impairs normal glucose homeostasis through many pathophysiological mechanisms. The varying degrees of glucose intolerance, including impaired fasting glucose, impaired glucose tolerance, and Diabetes Mellitus (DM) are commonly observed in patients with CD and contribute to significant morbidity and mortality. Although definitive surgical treatment of ACTH-secreting tumors remains the most effective therapy to control both cortisol levels and glucose metabolism, nearly one-third of patients present with persistent or recurrent disease and require additional treatments. In recent years, several medical therapies demonstrated prominent clinical efficacy in the management of patients with CD for whom surgery was non-curative or for those who are ineligible to undergo surgical treatment. Cortisol-lowering medications may have different effects on glucose metabolism, partially independent of their role in normalizing hypercortisolaemia. The expanding therapeutic landscape offers new opportunities for the tailored therapy of patients with CD who present with glucose intolerance or DM, however, additional clinical studies are needed to determine the optimal management strategies. In this article, we discuss the pathophysiology of impaired glucose metabolism caused by cortisol excess and review the clinical efficacy of medical therapies of CD, with particular emphasis on their effects on glucose homeostasis.

Increased uptake of oxLDL does not exert lipotoxic effects in insulin-secreting cells

Modified lipoproteins can negatively affect beta cell function and survival. However, the mechanisms behind interactions of modified lipoproteins with beta cells - and in particular, relationships to increased uptake - are only partly clarified. By over-expressing the scavenger receptor CD36 (Tet-on), we increased the uptake of fluorescent low-density modified lipoprotein (oxLDL) into insulin-secreting INS-1 cells. The magnitude of uptake followed the degree of CD36 over-expression. CD36 over-expression increased concomitant efflux of 3H-cholesterol in proportion to the cellular contents of 3H-cholesterol. Exposure to concentrations of oxLDL from 20 to 100 µg/mL dose-dependently increased toxicity (evaluated by MTT) as well as apoptosis. However, the increased uptake of oxLDL due to CD36 over-expression did not exert additive effects on oxLDL toxicity - neither on viability, nor on glucose-induced insulin release and cellular content. Reciprocally, blocking CD36 receptors by Sulfo-N-Succinimidyl Oleate decreased the uptake of oxLDL but did not diminish the toxicity. Pancreatic islets of CD36-/- mice displayed reduced uptake of 3H-cholesterol-labeled oxLDL vs wild type but similar toxicity to oxLDL. OxLDL was found to increase the expression of CD36 in islets and INS-1 cells. In summary, given the experimental conditions, our results indicate that (1) increased uptake of oxLDL is not responsible for toxicity of oxLDL, (2) increased efflux of the cholesterol moiety of oxLDL counterbalances, at least in part, increased uptake and (3) oxLDL participates in the regulation of CD36 in pancreatic islets and in INS-1 cells.

The effects of short-term fasting on tolerance to (neo) adjuvant chemotherapy in HER2-negative breast cancer patients: a randomized pilot study

BACKGROUND

Preclinical evidence shows that short-term fasting (STF) protects healthy cells against side effects of chemotherapy and makes cancer cells more vulnerable to it. This pilot study examines the feasibility of STF and its effects on tolerance of chemotherapy in a homogeneous patient group with early breast cancer (BC).

METHODS

Eligible patients had HER2-negative, stage II/III BC. Women receiving (neo)-adjuvant TAC (docetaxel/doxorubicin/cyclophosphamide) were randomized to fast 24 h before and after commencing chemotherapy, or to eat according to the guidelines for healthy nutrition. Toxicity in the two groups was compared. Chemotherapy-induced DNA damage in peripheral blood mononuclear cells (PBMCs) was quantified by the level of γ-H2AX analyzed by flow cytometry.

RESULTS

Thirteen patients were included of whom seven were randomized to the STF arm. STF was well tolerated. Mean erythrocyte- and thrombocyte counts 7 days post-chemotherapy were significantly higher (P = 0.007, 95 % CI 0.106-0.638 and P = 0.00007, 95 % CI 38.7-104, respectively) in the STF group compared to the non-STF group. Non-hematological toxicity did not differ between the groups. Levels of γ-H2AX were significantly increased 30 min post-chemotherapy in CD45 + CD3- cells in non-STF, but not in STF patients.

CONCLUSIONS

STF during chemotherapy was well tolerated and reduced hematological toxicity of TAC in HER2-negative BC patients. Moreover, STF may reduce a transient increase in, and/or induce a faster recovery of DNA damage in PBMCs after chemotherapy. Larger studies, investigating a longer fasting period, are required to generate more insight into the possible benefits of STF during chemotherapy.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT01304251 , March 2011.

Psychotic disorder is an independent risk factor for increased fasting glucose and waist circumference

BACKGROUND

Psychosis is associated with excess cardiovascular morbidity and mortality.

AIMS

To determine the prevalence of cardiovascular risk factors in patients with psychotic disorders compared with the population.

METHODS

731 consecutive patients with psychosis recruited from psychiatric outpatient clinics in Stockholm County, Sweden, were compared with 5580 individuals from a population study performed in the same area. The main outcome measures were waist circumference, body mass index (BMI) and fasting glucose.

RESULTS

Mean waist circumference in patients vs. controls was for males 106 and 94 cm, respectively, and for females 97 and 85 cm, respectively (P < 0.001); mean fasting glucose in patients vs. controls was for males 5.8 and 5.2 mmol/l, respectively, and for females 5.6 and 4.8 mmol/l, respectively (P < 0.001). Comparisons were controlled for differences in age and family history of diabetes. Increased waist circumference was more common in psychotic patients compared with controls (OR = 3.99; 95% CI 3.09-5.15), controlling for fasting insulin, differences in gender, blood pressure, fasting glucose, family history of diabetes, age and tobacco use. Increased fasting blood glucose was also more common in psychotic patients (OR = 2.41; 95% CI 1.84-3.14) controlling for the same factors with the exception of fasting glucose and with the addition of increased waist circumference.

CONCLUSION

Our study shows that the psychosis illness per se can be considered as a cardiovascular risk factor, independent of the traditional risk factors such as age and smoking.

Mitogen-activated protein kinases and protein phosphatase 5 mediate glucocorticoid-induced cytotoxicity in pancreatic islets and β-cells

Glucocorticoid excess is associated with glucose intolerance and diabetes. In addition to inducing insulin resistance, glucocorticoids impair β-cell function and cause β-cell apoptosis. In this study we show that dexamethasone activates mitogen-activated protein kinases (MAPKs) signaling in MIN6 β-cells, as evident by enhanced phosphorylation of p38 MAPK and c-Jun N-terminal kinase (JNK). In contrast, the integrated stress response pathway was inhibited by dexamethasone. A p38 MAPK inhibitor attenuated dexamethasone-induced apoptosis in β-cells and isolated islets and decreased glucocorticoid receptor phosphorylation at S220. In contrast, a JNK inhibitor augmented DNA fragmentation and dexamethasone-induced formation of cleaved caspase 3. We also show that inhibition of protein phosphatase 5 (PP5) augments apoptosis in dexamethasone-exposed islets and β-cells, with a concomitant activation of p38 MAPK. In conclusion, our data provide evidence that in islets and β-cells, p38 MAPK and JNK phosphorylation work in concert with PP5 to regulate the cytotoxic effects exerted by glucocorticoids.

Liraglutide counteracts obesity and glucose intolerance in a mouse model of glucocorticoid-induced metabolic syndrome

BACKGROUND

Glucocorticoid excess is commonly associated with diabetogenic effects, including insulin resistance and glucose intolerance. The effects of the long-term glucagon-like peptide 1 receptor agonist treatment on the metabolic syndrome-like conditions are not yet fully elucidated. Thus, we aimed to test whether long-term liraglutide treatment could be effective as a therapy to counteract the metabolic dysfunctions induced by chronic glucocorticoid exposure.

METHODS

Mice were given corticosterone or vehicle via their drinking water for five consecutive weeks. In addition, mice were treated with once-daily injections of either PBS or liraglutide.

RESULTS

Liraglutide treatment slowed progression towards obesity and ectopic fat deposition in liver that otherwise occurred in corticosterone-treated mice. The drug reduced the increment in serum insulin caused by corticosterone, but did not affect the reduction of insulin sensitivity. Furthermore, liraglutide improved glucose control in mice exposed to corticosterone as evident by a delay in the progression towards post-prandial hyperglycemia and enhanced glucose clearance during a glucose tolerance test. Glucose-stimulated C-peptide levels were higher in those mice that had received liraglutide and corticosterone compared to mice that had been treated with corticosterone alone, indicating a positive role of liraglutide for beta-cell function. Morphometric analysis revealed increased beta- and alpha-cell masses that were associated with more Ki67-positive islet cells in corticosterone-treated mice irrespective of whether they were co-treated with liraglutide or not. Liraglutide had no discernible effect on alpha-cell mass.

CONCLUSION

Liraglutide can be beneficial for subjects at risk of developing metabolic complications as a result of glucocorticoid excess.

Glucocorticoid-induced hyperglycemia

Corticosteroid-induced hyperglycemia is a common medical problem that can lead to frequent emergency room visits, hospital admissions and prolonged hospital stay, in addition to the well known morbidity associated with hyperglycemia. However, the diagnosis and treatment of corticosteroid-induced hyperglycemia is surprisingly undervalued by most professionals, probably because of the lack of quality studies to determine specific strategies of action. In the present review, we discuss the pathophysiology of corticosteroid-induced hyperglycemia, focusing on diverse patterns of hyperglycemia induced by the different formulations, and provide clues for diagnosis based on the duration of treatment and the administration schedule of corticosteroids. We propose a treatment strategy based on both the pathophysiology of the process and the mechanism of action of different corticosteroids, and take into account dosing and administration timing to predict the duration of therapy. Finally, we propose treatment goals that differ slightly between the transient and continuous use of corticosteroids based on evidence from clinical practice guidelines of diabetes care both in ambulatory and hospital settings.

Increased DNA methylation levels of the insulin-like growth factor binding protein 1 gene are associated with type 2 diabetes in Swedish men

Background

Prospective studies have shown that low levels of circulating insulin-like growth factor binding protein-1 (IGFBP-1) are associated with the risk of type 2 diabetes. In the present study, we investigated DNA methylation in the IGFBP1 gene to evaluate its changes in relation to serum IGFBP-1 levels in type 2 diabetes.

Results

A total of 406 Swedish men, including age-matched normal glucose tolerance subjects and type 2 diabetes patients either newly diagnosed or undergoing treatment, were selected from the Stockholm Diabetes Prevention Program. IGFBP1 methylation levels in genomic DNA extracted from peripheral blood were analysed by bisulfite pyrosequencing. Serum IGFBP-1 levels were measured by radio-immunoassay. We found that IGFBP1 DNA methylation levels were higher in both newly diagnosed and treated type 2 diabetes patients with a mean diabetes duration of 3 years compared with subjects with normal glucose tolerance (19.8% and 20.2% vs. 16.9%, P < 0.001 for both). Serum levels of IGFBP-1 in newly diagnosed and in treated type 2 diabetes patients were lower compared with healthy individuals (18 μg/l both vs. 24 μg/l, P = 0.011, P < 0.001). IGFBP1 methylation levels but not serum IGFBP-1 levels in type 2 diabetes patients were independent of body mass index. Newly diagnosed patients with a family history of diabetes (FHD) had higher IGFBP1 methylation levels than those without FHD (20.3% vs. 18.6%, P = 0.017).

Conclusions

This study provides the first evidence that changes in DNA methylation of the IGFBP1 gene are associated with type 2 diabetes in Swedish men and suggests that increased IGFBP1 DNA methylation and decreased IGFBP-1 serum levels are features of type 2 diabetes with a short duration.

Gynostemma pentaphyllum Tea Improves Insulin Sensitivity in Type 2 Diabetic Patients

Aims. To evaluate the effect of the traditional Vietnamese herb Gynostemma pentaphyllum tea on insulin sensitivity in drug-naïve type 2 diabetic patients. Methods. Patients received GP or placebo tea 6 g daily for four weeks and vice versa with a 2-week wash-out period. At the end of each period, a somatostatin-insulin-glucose infusion test (SIGIT) was performed to evaluate the insulin sensitivity. Fasting plasma glucose (FPG), HbA(1C), and oral glucose tolerance tests and insulin levels were measured before, during, and after the treatment. Results. FPG and steady-state plasma glucose (SIGIT mean) were lower after GP treatment compared to placebo treatment (P < 0.001). The levels of FPG in the control group were slightly reduced to 0.2 ± 1.5 versus 1.9 ± 1.0 mmol/L in GP group (P < 0.001), and the effect on FPG was reversed after exchanging treatments. The glycometabolic improvements were achieved without any major change of circulating insulin levels. There were no changes in lipids, body measurements, blood pressure, and no reported hypoglycemias or acute adverse effects regarding kidney and liver parameters. Conclusion. The results of this study suggested that the GP tea exerted antidiabetic effect by improving insulin sensitivity.

Improved Insulin Sensitivity during Pioglitazone Treatment Is Associated with Changes in IGF-I and Cortisol Secretion in Type 2 Diabetes and Impaired Glucose Tolerance

Background. Hypercortisolism and type 2 diabetes (T2D) share clinical characteristics. We examined pioglitazone's effects on the GH-IGF-I and HPA axes in men with varying glucose intolerance. Methods. 10 men with T2D and 10 with IGT received pioglitazone 30–45 mg for 12 weeks. OGTT with microdialysis in subcutaneous adipose tissue and 1 μg ACTH-stimulation test were performed before and after. Glucose, insulin, IGF-I, IGFBP1, and interstitial measurements were analyzed during the OGTT. Insulin sensitivity was estimated using HOMA-IR. Results. HOMA-IR improved in both groups. IGF-I was initially lower in T2D subjects (P = 0.004) and increased during treatment (−1.4 ± 0.5 to −0.5 ± 0.4 SD; P = 0.007); no change was seen in IGT (0.4 ± 39 SD before and during treatment). Fasting glycerol decreased in T2D (P = 0.038), indicating reduced lipolysis. Fasting cortisol decreased in T2D (400 ± 30 to 312 ± 25 nmol/L; P = 0.041) but increased in IGT (402 ± 21 to 461 ± 35 nmol/L; P = 0.044). Peak cortisol was lower in T2D during treatment (599 ± 32 to 511 ± 43, versus 643 ± 0.3 to 713 ± 37 nmol/L in IGT; P = 0.007). Conclusions. Pioglitazone improved adipose tissue and liver insulin sensitivity in both groups. This may explain increased IGF-I in T2D. Pioglitazone affected cortisol levels in both groups but differently, suggesting different mechanisms for improving insulin sensitivity between T2D and IGT.

Twenty-four-hour profiles of plasma glucose, insulin, C-peptide and free fatty acid in subjects with varying degrees of glucose tolerance following short-term, medium-dose prednisone (20 mg/day) treatment: evidence for differing effects on insulin secretion and action

OBJECTIVE

To determine the time course and prandial effects of short-term, medium-dose prednisone on 24-h metabolic patterns under standardized conditions.

CONTEXT

Glucocorticoids (GCs) adversely affect glucose homoeostasis but 24-h profiles of glucose, insulin, C-peptide and free fatty acids (FFAs) following short-term, medium-dose prednisone treatment in persons with varying degrees of glucose tolerance are not well defined.

DESIGN

An open-label cross-sectional interventional study.

SUBJECTS

Three groups were prospectively studied: persons with type 2 diabetes (T2DM; n = 7), persons 'at risk' for T2DM (AR; n = 8) and persons with normal glucose tolerance (NGT; n = 5).

METHODS

Before and after 3-day treatment with prednisone 20 mg each morning, subjects underwent 24-h frequent blood sampling. Eucaloric mixed meals were provided at 08:00, 12:00 and 18:00 h. Insulin/glucose ratio provided an estimate of β-cell response to meal stimuli.

MEASUREMENTS

Plasma glucose, insulin, C-peptide, haemoglobin A1c and FFA.

RESULTS

Prednisone induced greater increases in glucose levels from midday (P = 0·001) to midnight (P = 0·02) in the T2DM than the AR and NGT groups. In contrast, insulin (P = 0·03) and C-peptide (P = 0·04) levels decreased postbreakfast in the T2DM group, whereas no changes in the morning but higher C-peptide levels (P = 0·03) from midday to midnight were observed in the AR group. In the T2DM group, insulin/glucose ratio decreased postbreakfast (P = 0·04) and increased postdinner (P = 0·03). Fasting glucose, insulin and C-peptide levels were unchanged in all groups, and FFA levels modestly increased postdinner (P = 0·03) in the NGT group.

CONCLUSION

Short-term, medium-dose prednisone treatment induces postprandial hyperglycaemia in T2DM and AR predominantly from midday to midnight because of suppression of insulin secretion followed by decreased insulin action that dissipates overnight. Effective treatment of prednisone-induced hyperglycaemia should target both rapid onset relative insulin deficiency and a less than 24-h total duration of effect.

Hypertension and other morbidities with Cushing's syndrome associated with corticosteroids: a review

Corticosteroids constitute an ideal treatment for various inflammatory and autoimmune disorders due to their anti-inflammatory and immunomodulatory actions. However, corticosteroids have a considerable number of side effects, including hypertension, diabetes, lipid disorders, sleep apnea, osteoporosis, myopathy, and disorders of coagulation and fibrinolysis, which are components of Cushing’s syndrome (CS). Corticosteroid-induced side effects are dependent on the formulation, route, dose, and time of exposure. However, the underlying pathogenetic mechanisms have not been clearly defined. A large body of evidence supports the role of an imbalance between vasoconstriction and vasodilation with possible links to nitric oxide, prostanoids, angiotensin II, arginine vasopressin, endothelins, catecholamines, neuropeptide Y, and atrial natriuretic peptide. Increased oxidative stress, renin–angiotensin system activation, increased pressor response, metabolic syndrome, and sleep apnea appear to be pathogenetically involved as well. The ideal treatment is the withdrawal of corticosteroids, which is most often impossible due to the exacerbation of the underlying disease. Alternatively, a careful plan, including the proper selection of the formulation, time, and route, should be made, and each side effect should be treated properly. The focus of the research should be to develop synthetic corticosteroids with anti-inflammatory effects but fewer metabolic effects, which so far has been unsuccessful.

Insulin-glucose infusion given before hemodialysis increases IGF-I in type 2 diabetes patients with chronic kidney disease

OBJECTIVE

Hemodialysis is associated with catabolism and one contributing factor could be decreased bioavailable IGF-I. The aim of this investigation was to study the response of IGF-I and IGFBP-1 to a euglycemic hyperinsulinemic clamp before hemodialysis in type 2 diabetes (T2D) with chronic kidney disease on hemodialysis (CKD5D). Stage 5 (Stages 0-5 according to renal function) indicates a GFR less than 15 mL/min/1.73 m², D indicates hemodialysis. The response was compared with that in type 1 diabetes (T1D) with normal renal function.

DESIGN

Five overnight fasted patients with T2D with CKD5D were subjected to an insulin infusion (1.6 mU/kg/h) for 4 h after which they had lunch followed by a four hour hemodialysis session. The results were compared with results from a previous study in seven T1D patients with normal renal function who had received a similar clamp the same insulin dose with the addition of an initial bolus dose. Blood samples were drawn at 15 to 30 min intervals for analysis of IGFBP-1, IGF-I and insulin and at 5 min intervals to determine blood glucose.

RESULTS

There was no significant change between pre- and postdialysis values of IGF-I but there was a significant 29% increase (p<0.05) at the end of hemodialysis compared with the basal levels before insulin infusion in the T2D patients with CKD5D. The fasting mean levels of IGFBP-1 were increased in both T1D with normal renal function (geometric mean: 216 μg/l, range 169-275 μg/l) and in T2D with CKD5D (geometric mean: 112 μg/l , range 78-162 μg/l, p=0.15 compared with T1D patients) in spite of a high mean insulin level (32±5 mU/l). Insulin caused a similar decrease (p<0.05 all groups) in IGFBP-1 mean levels for the first 90 min in the T2D patients with CKD5D (73±7% of basal IGFBP-1 values) and the T1D patients (69±6%) with normal renal function. After 90 min there was a blunted response in the T2D patients with CKD5D whereas IGFBP-1 in the T1D patients with normal renal function continued to decline. After hemodialysis the IGFBP-1 serum levels increased compared with the levels at the end of insulin infusion but the predialysis values remained significantly lower than before the insulin infusion.

CONCLUSION

Type 2 diabetes patients with chronic kidney disease requiring hemodialysis (CKD5D) have a high mean basal level of IGFBP-1 in spite of increased insulin levels. The first 90 min response of IGFBP-1 to insulin infusion is similar in T2D patients with CKD5D and T1D patients with normal renal function. After 90 min of insulin infusion a blunted decrease in IGFBP-1 was seen in T2D patients with CKD5D compared with type \1 diabetes with normal renal function. Insulin infusion before hemodialysis reduced the earlier reported increase in IGFBP-1 and increased IGF-I levels. Insulin infusion before dialysis in patients with CKD5D should be further studied since it could contribute to an anabolic effect with more bioavaialable IGF-I thus reducing the catabolic effect of hemodialysis.

Cortisol is negatively associated with insulin sensitivity in overweight Latino youth

CONTEXT AND OBJECTIVE

The purpose of the present study was to investigate the cross-sectional and longitudinal associations of serum morning cortisol and aspects of insulin action in Latino children and adolescents (8-13 yr) at risk for type 2 diabetes.

DESIGN AND PARTICIPANTS

The present study includes a cross-sectional analysis in 211 participants and a longitudinal analysis in a subset of 143 participants.

RESULTS

At baseline, cortisol was negatively associated with fasting glucose (r = 0.23; P < 0.01), β-cell function (disposition index, r = -0.24; P < 0.05), and acute insulin response to glucose (r = -0.27; P < 0.05). Baseline cortisol was also significantly related to the change in insulin sensitivity over 1 yr (r = -0.23; P < 0.05). These results did not differ by Tanner stage or sex.

CONCLUSIONS

Cortisol contributes to the reduction in insulin sensitivity at an early age in Latino children and adolescents. Specifically, cortisol is negatively associated with potential compensatory mechanisms for insulin resistance, such as increased β-cell function and increased insulin release to a glucose challenge, by exacerbating the progression toward insulin resistance in this population. The results underline the relevance of glucocorticoid reduction for the prevention of metabolic disease in Latino children and adolescents.

Acute and 2-week exposure to prednisolone impair different aspects of beta-cell function in healthy men

OBJECTIVE

Glucocorticoids (GCs), such as prednisolone, are associated with adverse metabolic effects, including glucose intolerance and diabetes. In contrast to the well known GC-induced insulin resistance, the effects of GCs on beta-cell function are less well established. We assessed the acute and short-term effects of prednisolone treatment on beta-cell function in healthy men.

RESEARCH DESIGN AND METHODS

A randomised, double-blind, placebo-controlled trial consisting of two protocols was conducted. In protocol 1 (n=6), placebo and a single dose of 75 mg of prednisolone were administered. In protocol 2 (n=23), participants received 30 mg of prednisolone daily or placebo for 15 days. Both empirical and model-based parameters of beta-cell function were calculated from glucose, insulin and C-peptide concentrations obtained during standardised meal tests before and during prednisolone treatment (protocols 1 and 2), and 1 day after cessation of treatment (protocol 2).

RESULTS

Seventy-five milligrams of prednisolone acutely increased the area under the postprandial glucose curve (AUC(gluc); P=0.005), and inhibited several parameters of beta-cell function, including AUC(c-pep)/AUC(gluc) ratio (P=0.004), insulinogenic index (P=0.007), glucose sensitivity (P=0.02) and potentiation factor ratio (PFR; P=0.04). A 15-day treatment with prednisolone increased AUC(gluc) (P<0.001), despite augmented C-peptide secretion (P=0.05). beta-cell function parameters were impaired, including the fasting insulin secretory tone (P=0.02) and PFR (P=0.007).

CONCLUSIONS

Acute and short-term exposure to prednisolone impairs different aspects of beta-cell function, which contribute to its diabetogenic effects.

Prospective short-term effects of glucocorticoid treatment on glucose and lipid metabolism in Japanese

OBJECTIVE

Glucocorticoid (GC) causes various metabolic abnormalities; however, few prospective studies have examined the changes in glucose and lipid metabolism in newly GC-treated patients.

METHODS AND PATIENTS

The present study was therefore performed to analyze markers of glucose and lipid metabolism on days 0, 3, 7, 14, 28 and at month 3 of treatment in patients starting GC therapy. Then, we analyzed the relationships between the changes in these parameters and the initial dose of prednisolone (PSL), separating groups into different regimens by the GC dose.

RESULTS

The fasting plasma glucose (FPG) level transiently increased on day 3 of PSL administration but was restored by day 7. The immunoreactive insulin (IRI) level and HOMA-R transiently increased on day 3 and then fell, although remaining significantly higher than each basal level by day 7. A transient elevation in FPG level on day 3 was observed only in groups with a PSL dose >or=40 mg. On the other hand, total cholesterol and low-density lipoprotein cholesterol levels increased on day 3 of PSL administration and similar levels were maintained after day 7. High density-lipoprotein cholesterol levels were significantly increased on day 3; subsequently then gradually increased from days 3 to day 28. Triglyceride levels did not change during treatment. No relationship was apparent between the GC dose and the changes in each lipid parameter.

CONCLUSION

GC treatment induced changes in FPG, IRI, LDL-CHOL and HDL-CHOL levels from day 3 after start of GC. The dose of GC seemed to influence glucose metabolism, but not lipid metabolism.

Factors determining normalization of glucose intolerance in middle-aged Swedish men and women: a 8-10-year follow-up

AIMS

To examine factors in middle-aged Swedish men and women predicting the conversion from a state of abnormal glucose regulation to normal glucose tolerance (NGT) after 8-10 years.

METHODS

At baseline 3128 men and 4821 women, aged 35-56 years, without previously diagnosed diabetes underwent an oral glucose tolerance test and completed a questionnaire. At follow-up, 2383 men and 3329 women were re-examined. The study group consisted of 156 men and 124 women with impaired fasting glucose (IFG), impaired glucose tolerance (IGT), or both at baseline.

RESULTS

The rate of reversal to NGT from IFG or IGT was similar regardless of gender. In participants having IFG or IGT, reversal to NGT was predicted by low fasting and 2-h insulin, homeostasis model assessment of insulin resistance and of pancreatic beta cell function, body mass index and waist circumference without differences between gender and baseline glucose tolerance group. Low 2-h glucose, however, predicted reversal to NGT in men with IFG at baseline, but not in men with IGT at baseline, or in women with either IFG or IGT at baseline. Men reverting to NGT had higher coffee consumption and women had higher baseline leisure-time physical activity. In multiple logistic regression, including all participants, low fasting and 2-h glucose remained independent predictors of reverting to NGT.

CONCLUSIONS

Factors predicting reversal to NGT were measures correlated with low insulin resistance, but also lower insulin secretion, perhaps indicating a lower pancreatic beta cell workload in those who reverted. In men, but not in women, low 2-h glucose was of predictive value.

Novel insights into glucocorticoid-mediated diabetogenic effects: towards expansion of therapeutic options?

At pharmacological concentrations, glucocorticoids (GCs) display potent anti-inflammatory effects, and are therefore frequently prescribed by physicians to treat a wide variety of diseases. Despite excellent efficacy, GC therapy is hampered by their notorious metabolic side effect profile. Chronic exposure to increased levels of circulating GCs is associated with central adiposity, dyslipidaemia, skeletal muscle wasting, insulin resistance, glucose intolerance and overt diabetes. Remarkably, many of these side-effects of GC treatment resemble the various components of the metabolic syndrome (MetS), in which indeed subtle disturbances in the hypothalamic-pituitary-adrenal (HPA) axis and/or increased tissue sensitivity to GCs have been reported. Recent developments have led to renewed interest in the mechanisms of GC's diabetogenic effects. First, 'selective dissociating glucocorticoid receptor (GR) ligands', which aim to segregate GC's anti-inflammatory and metabolic actions, are currently being developed. Second, at present, selective 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1) inhibitors, which may reduce local GC concentrations by inhibiting cortisone to cortisol conversion, are evaluated in clinical trials as a novel treatment modality for the MetS. In this review, we provide an update of the current knowledge on the mechanisms that underlie GC-induced dysmetabolic effects. In particular, recent progress in research into the role of GCs in the pathogenesis of insulin resistance and beta-cell dysfunction will be discussed.

Insulin stimulated glucose disposal in peripheral tissues studied with microdialysis and stable isotope tracers

BACKGROUND & AIMS

Methods to study glucose kinetics in vivo in specific tissues or tissue beds in humans are often not feasible due to invasiveness or costs of equipment needed. Here we investigate whether the loss (fractional extraction) of 2H7-glucose infused via a microdialysis catheter can be used to study glucose disposal in skeletal muscle and subcutaneous adipose tissue.

METHODS AND RESULTS

A perfusion period of 2 h was needed to ensure an isotopic steady state in the microdialysis catheters in skeletal muscle and adipose tissue. In six healthy volunteers the fractional extraction increased during a hyperinsulinemic euglycemic clamp in both skeletal muscle and adipose tissue. Following 48 h of starvation in the same subjects, insulin was not able to increase the fractional extraction of 2H7-glucose from the microdialysis in comparison with a baseline measurement.

CONCLUSIONS

In response to insulin infusion, the fractional extraction of 2H7-glucose from a microdialysis catheter increases in skeletal muscle and subcutaneous adipose tissue and this increase is blunted during insulin resistance induced by starvation. These results validate that the fractional extraction of a glucose tracers infused via microdialysis can be used as an index of glucose disposal in peripheral tissues or tissue beds.

IGFBP-1 levels in adult women born small for gestational age suggest insulin resistance in spite of normal BMI

OBJECTIVE

Impaired fetal development may contribute to decreased insulin sensitivity. This study was designed to characterize serum markers of insulin resistance in adults born small for date or born prematurely.

STUDY DESIGN

Fifty subjects, all women, were evaluated at a mean age +/- SD of 26 +/- 2 years (range: 23-30 years). They were allocated to three groups: (i) born fullterm with birth weight <2600 g (n = 18) (small for gestational age, SGA), (ii) born before gestational week 32 (n = 15) (ex-preterm), and (iii) controls, born fullterm with appropriate birth weight (n = 17). Anthropometric data as well as fasting serum samples of plasma B-glucose, serum lipids, insulin, insulin-like growth factor-I (IGF-I) and insulin-like growth factor binding protein-1 (IGFBP-1) levels were determined.

RESULTS

In the SGA group final height was lower and they weighed less compared with the controls. Fasting insulin and glucose levels did not differ amongst the groups. Triglycerides were lower in the SGA group and in the ex-preterm group compared with the controls (P < 0.05). The SGA group showed lower IGFBP-1 levels compared with the controls median 17 (range 3-121) vs. 26 (7-67) microg L-1; P < 0.05]. The IGF-I levels in the SGA, ex-preterm and control groups were 212 +/- 58, 259 +/- 37 and 216 +/- 32 microg L-1, respectively, corresponding to a mean SD score of -0.8 +/- 1.0, 0.1 +/- 0.6 and -0.6 +/- 0.6.

CONCLUSION

As IGFBP-1 is a marker of insulin sensitivity, the low levels observed in adult women with normal BMI, born small for date, suggest relative insulin resistance in spite of normal BMI.

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

OBJECTIVES

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

DESIGN

Randomized clinical study.

SETTING

University hospital.

PARTICIPANTS

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

INTERVENTIONS

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

Glucagon-like peptide-1 analogue LY315902: effect on intestinal motility and release of insulin and somatostatin

LY315902 is an analogue of GLP-1 that yields a reduced clearance and longer half-life. The aim of the study is to assess the effect of LY315902 on fasting gastrointestinal motility, somatostatin and insulin release. Sprague-Dawley rats were fitted with three bipolar electrodes, 15, 25 and 35 cm distal to the pylorus. The effect of LY315902 and GLP-1 on migrating myoelectric complex (MMC) cycle length, duration and propagating velocity of activity fronts was studied for 60 min in conscious animals. The effect of LY315902 and GLP-1 on fasting small bowel motility was dose-dependent and treatment with exendin (9-39)amide, a GLP-1 receptor antagonist, together with LY315902 and GLP-1 completely antagonised the inhibitory effect of LY315902 and GLP-1 on fasting small bowel motility. Pretreatment with the nitric oxide (NO) synthase inhibitor N(omega)-nitro-L-arginine (L-NNA) partly blocked the action of both LY315902 and GLP-1. Plasma insulin concentrations were not different from controls during infusion of LY315902 or GLP-1, while somatostatin concentrations were significantly higher during LY315902 and GLP-1 compared to saline. LY315902 has a longer duration of inhibitory action on the MMC than GLP-1, albeit similar effects on plasma insulin and somatostatin concentrations. The effect of LY315902 on motor control is mediated through the GLP-1 receptor and seems partly dependent on the L-arginine/NO pathway.

A carbohydrate-rich drink reduces preoperative discomfort in elective surgery patients

We studied the effects of different preoperative oral fluid protocols on preoperative discomfort, residual gastric fluid volumes, and gastric acidity. Two-hundred-fifty-two elective abdominal surgery patients (ASA physical status I-II) were randomized to preparation with a 12.5% carbohydrate drink (CHO), placebo (flavored water), or overnight fasting. The CHO and Placebo groups were double-blinded and were given 800 mL to drink on the evening before and 400 mL on the morning of surgery. Visual analog scales were used to score 11 different discomfort variables. CHO did not increase gastric fluid volumes or affect acidity, and there were no adverse events. The visual analog scale scores in a control situation were not different between groups. During the waiting period before surgery, the CHO-treated group was less hungry and less anxious than both the other groups (P < or = 0.05). CHO reduced thirst as effectively as placebo (P < 0.0001 versus Fasted). Trend analysis showed consistently decreasing thirst, hunger, anxiety, malaise, and unfitness in the CHO group (P < 0.05). The Placebo group experienced decreasing unfitness and malaise, whereas nausea, tiredness, and inability to concentrate increased (P < 0.05). In the Fasted group, hunger, thirst, tiredness, weakness, and inability to concentrate increased (P < 0.05). In conclusion, CHO significantly reduces preoperative discomfort without adversely affecting gastric contents.

IMPLICATIONS

Discomfort during the period of waiting before elective surgery can be reduced if patients are prepared with a carbohydrate-rich drink, compared with preoperative oral intake of water or overnight fasting. Visual analog scales can provide useful information about preoperative discomfort in elective surgery patients.

Insulin infusion increases levels of free IGF-I and IGFBP-3 proteolytic activity in patients after surgery

We have studied the effects of insulin on the bioavailability of insulin-like growth factor (IGF) I in insulin-resistant patients after surgery. Serum levels of total IGF-I (tIGF-I), free IGF (fIGF)-I, fIGF-II, and IGF-binding protein (IGFBP) 1 and IGFBP-3 proteolytic activity (IGFBP-3-PA), determined on the day before surgery and on the 1st postoperative day, were related to insulin sensitivity measured by a hyperinsulinemic, normoglycemic clamp. Before surgery, the decreased tIGF-I (P < 0.05) in response to insulin infusion was accompanied by an 18% reduction of IGFBP-1 (P < 0.001), while IGFBP-3-PA remained unchanged. Levels of fIGF-I and fIGF-II were not changed by insulin infusions. After surgery, IGFBP-3-PA increased (P < 0.05) during insulin infusion, and this was associated with an increase in tIGF-I (P < 0.001) and fIGF-I (P < 0.01), while no significant change was found in fIGF-II. The reduction in IGFBP-1 in response to insulin infusion was not affected by surgery. The change in IGFBP-3-PA during insulin infusion after surgery was related to the corresponding change in fIGF-I (r(2) = 0.26, P < 0.05) and postoperative insulin sensitivity (r(2) = -0.22, P < 0.05). These data suggest that increased IGFBP-3-PA during insulin infusion after surgery governs the increased levels of fIGF-I, while insulin-induced suppression of IGFBP-1 was not affected by surgery. We propose that, in catabolic, postoperative patients, increased levels of insulin from exogenous or, possibly, endogenous sources (nutritionally induced) may be a signal to increase IGF-I bioavailability by increased expression of IGFBP-3-PA to counteract further deterioration in glucose metabolism.

Preoperative oral carbohydrate treatment attenuates immediate postoperative insulin resistance

Postoperative insulin resistance is a well-characterized metabolic state that has been shown to correlate with the length of postoperative stay in hospital. Preoperative intravenous or oral carbohydrate treatment has been shown to attenuate the development of postoperative insulin resistance measured 1 day after surgery. To study the effects of preoperative oral carbohydrate treatment on postoperative changes in insulin resistance and substrate utilization, in the absence of postoperative confounding factors, 15 patients were double-blindly treated with either a carbohydrate-rich beverage (12.5%) (n = 8) or placebo (n = 7) before undergoing total hip replacement surgery. Insulin sensitivity, endogenous glucose release, and substrate oxidation rates were measured before and immediately after surgery. Whole body insulin sensitivity decreased by 18% in the treatment group vs. 43% in the placebo group (P < 0.05, Student's t-test for unpaired data). In both groups, the major mechanism of insulin resistance was an inhibition of insulin-induced nonoxidative glucose disposal after surgery. The better preservation of insulin sensitivity in the treatment group was attributable to a less reduced glucose disposal in peripheral tissues and increased glucose oxidation rates.

Stimulation of human albumin synthesis and gene expression by growth hormone treatment

BACKGROUND AND AIMS

In this study the effects of acute (5 h) and short-term (5 days) GH treatment on albumin synthesis rates in man were investigated and related to changes in the availability of hepatic albumin mRNA.

METHODS

30 patients undergoing elective laparoscopic cholecystectomy were randomized into controls (n=10) or GH-treatment (12 U/dose) for 5 h or 5 days (n=10 in each group). Albumin mRNA levels (in liver biopsy specimens) were measured employing a quantitative polymerase chain reaction assay developed specifically for this purpose, whereas albumin synthesis was measured using [(2)H(5)]phenylalanine.

RESULTS

The fractional synthesis rate of albumin was 6.0+/-0.9 %/day in the control group and 8.0+/-1.8 %/day and 8.3+/-1.7 %/day in the GH-treated groups, respectively (P<0.05 vs controls in both cases). The corresponding values for the concentration of albumin mRNA were 2.6+/-1.1 ng/microg total RNA, 2.9+/-0.8 ng/microg total RNA (NS) and 4.7+/-1.8 ng/microg total RNA in the "GH 5" group (P<0.01 vs controls). The changes in albumin synthesis were only partly explained by the differences in hepatic albumin mRNA levels (r=0.5, P<0.01).

CONCLUSION

These results suggest that GH may induce a quick, gene expression-independent increase in albumin synthesis, which is sustained by a later-occurring increase in albumin gene expression.

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.

Surgery-induced insulin resistance in human patients: relation to glucose transport and utilization

To investigate the underlying molecular mechanisms for surgery-induced insulin resistance in skeletal muscle, six otherwise healthy patients undergoing total hip replacement were studied before, during, and after surgery. Patients were studied under basal conditions and during physiological hyperinsulinemia (60 microU/ml). Biopsies of vastus lateralis muscle were used to measure GLUT-4 translocation, glucose transport, and glycogen synthase activities. Surgery reduced insulin-stimulated glucose disposal (P < 0.05) without altering the insulin-stimulated increase in glucose oxidation or suppression of endogenous glucose production. Preoperatively, insulin infusion increased plasma membrane GLUT-4 in all six subjects (P < 0.05), whereas insulin-stimulated GLUT-4 translocation only occurred in three patients postoperatively (not significant). Moreover, nonoxidative glucose disposal rates and basal levels of glycogen synthase activities in muscle were reduced postoperatively (P < 0.05). These findings demonstrate that peripheral insulin resistance develops immediately postoperatively and that this condition might be associated with perturbations in insulin-stimulated GLUT-4 translocation as well as nonoxidative glucose disposal, presumably at the level of glycogen synthesis.

Depression of liver protein synthesis during surgery is prevented by growth hormone

This study was undertaken to elucidate the specific effects of growth hormone (GH) on liver protein metabolism in humans during surgery. Otherwise healthy patients scheduled for elective laparoscopic cholecystectomy were randomized into controls (n = 9) or pretreatment with 12 units of GH for 1 day (GH 1, n = 9) or daily for 5 days (GH 5, n = 10). The fractional synthesis rate of liver proteins, as assessed by flooding with [2H5]phenylalanine, was higher in the GH 5 group (22.0 +/- 6.9%/day, mean +/- SD, P < 0.05) than in the control (16.1 +/- 3.1%/day) and GH 1 (16.5 +/- 5.5%/day) groups. During surgery, the fraction of polyribosomes in the liver, as assessed by ribosome analysis, decreased in the control group by approximately 12% (P < 0.01) but did not decrease in the GH-treated groups. In addition, the concentrations of the essential amino acids and aspartate in the liver decreased in response to GH treatment. In conclusion, GH pretreatment decreases hepatic free amino acid concentrations and preserves liver protein synthesis during surgery.

Acute and short-term effects of growth hormone on insulin-like growth factors and their binding proteins: serum levels and hepatic messenger ribonucleic acid responses in humans

We investigated the acute (4-5 h) and short-term (5 days) effects of GH treatment on hepatic messenger RNA (mRNA) levels of the genes for the insulin-like growth factors (IGFs), insulin-like growth factor binding protein-1, -2, and -3 (IGFBPs), and the acid labile subunit (ALS), as well as serum levels of these proteins in humans. At the mRNA level, we observed an increase in IGF-1 transcription (+173%) following GH treatment in the acute group, which remained elevated in the short-term treatment group. IGFBP-2 mRNA decreased after short-term GH treatment, without changes in IGFBP-1 or -3 expression. The ALS transcript level increased after 5 days. In serum, we found increased levels of IGF-I and insulin, and decreased levels of IGF-II, in the short-term treatment group. IGFBP-1 decreased in both treatment groups, whereas IGFBP-2 was reduced after 5 days treatment. ALS increased in the short-term group. We observed increased IGFBP-3 serum levels after 5 days of GH treatment, likely due to increased formation of the ternary complex. Our results show that the metabolic effects by GH on the IGF axis are complex. In addition to a direct stimulation of IGF-I and ALS expression, GH inhibits IGFBP-1 serum levels and IGFBP-2 expression in an indirect manner, possibly facilitating enhanced IGF bioavailability to target tissues.

Inhibitory effect of glucagon-like peptide-1 on small bowel motility. Fasting but not fed motility inhibited via nitric oxide independently of insulin and somatostatin

Effects of glucagon-like peptide-1 (GLP-1)(7-36)amide on fasted and fed motility in the rat small intestine were investigated in relation to its dependence on nitric oxide (NO), insulin, and somatostatin. Small bowel electromyography was performed using bipolar electrodes implanted 15, 25, and 35 cm distal to pylorus, and transit was studied with a radioactive marker. In the fasted state, GLP-1 (5-20 pmol kg-1min-1), reaching physiological plasma levels, prolonged the migrating myoelectric complex (MMC) cycle length along with slowed transit. This effect was antagonized by exendin(9-39)amide. The NO synthase inhibitor Nomega-nitro- L-arginine (L-NNA) also blocked the response to GLP-1, whereas L-arginine restored the response. Insulin (80-200 pmol kg-1min-1) induced irregular spiking, whereas somatostatin (100-500 pmol kg-1min-1) increased the MMC cycle length, independently of NO. In the fed state, GLP-1 (20-40 pmol kg-1min-1) reduced motility, an inhibition unaffected by L-NNA, whereas motility was stimulated by exendin(9-39)amide. Infusion of GLP-1 (20-100 pmol kg-1min-1) did not affect plasma insulin, but somatostatin was increased. In conclusion, GLP-1 seems to inhibit small bowel motility directly via the GLP-1 receptor. Inhibition of fasting motility is dependent of NO and not mediated via insulin or somatostatin, whereas inhibition of fed motility is independent of NO.

Perioperative insulin and glucose infusion maintains normal insulin sensitivity after surgery

Elective surgery was performed after overnight fasting, a routine that may affect the metabolic response to surgery. We investigated the effects of insulin and glucose infusions before and during surgery on postoperative substrate utilization and insulin sensitivity. Seven patients were given insulin and glucose infusions 3 h before and during surgery (insulin group), and a control group of six patients underwent surgery after fasting overnight. Insulin sensitivity and glucose kinetics (D-[6,6-2H2]glucose) were measured before and immediately after surgery using a hyperinsulinemic, normoglycemic clamp. Glucose infusion rates and whole body glucose disposal decreased after surgery in the control group (-40 and -29%, respectively), whereas no significant change was found in the insulin group (+16 and +25%). Endogenous glucose production remained unchanged in both groups. Postoperative changes in cortisol, glucagon, fat oxidation, and free fatty acids were attenuated in the insulin group (vs. control). We conclude that perioperative insulin and glucose infusions minimize the endocrine stress response and normalize postoperative insulin sensitivity and substrate utilization.

Preoperative oral carbohydrate administration reduces postoperative insulin resistance

Infusions of carbohydrates before surgery reduce postoperative insulin resistance. We in-vestigated the effects of a carbohydrate drink, given shortly before surgery, on postoperative metabolism.

METHOD

Insulin sensitivity, glucose turnover ([6,6, 2H2]-D-glucose) and substrate utilization were measured using hyperinsulinemic normoglycemic clamps and indirect calorimetry in two matched groups of patients before and after elective colorectal surgery. The drink group (n = 7) received 800 ml of an isoosmolar carbohydrate rich beverage the evening before the operation (100 g carbohydrates), as well as another 400 ml (50 g carbohydrates) 2 h before the initiation of anesthesia. The fasted group (n = 7) was operated after an overnight fast.

RESULTS

After surgery, energy expenditure increased in both groups. Endogenous glucose production was higher after surgery and the difference was significant during low insulin infusion rates in both groups (P < 0.05). The supressibility of endogenous glucose production by the two step insulin infusion was similar pre-and postoperatively in both groups. At the high insulin infusion rate postoperatively, whole body glucose disposal was more reduced in the fasted group (-49 +/- 6% vs -26 +/- 8%, P < 0.05 vs drink). Furthermore, during high insulin infusion rates, glucose oxidation decreased postoperatively only in the fasted group (P < 0. 05) and postoperative levels of fat oxidation were greater in the fasted group (P < 0.05 vs drink). Only minor postoperative changes in cortisol and glucagon were found and no differences were found between the treatment groups.

CONCLUSIONS

Patients given a carbohydrate drink shortly before elective colorectal surgery displayed less reduced insulin sensitivity after surgery as compared to patients who were operated after an overnight fast.

Short-term hypocaloric nutrition but not bed rest decrease insulin sensitivity and IGF-I bioavailability in healthy subjects: the importance of glucagon

Hyperinsulinemic, normoglycemic clamps were performed before and after 24 h of either hypocaloric nutrition or bed rest in healthy subjects. Decreased insulin sensitivity and insulin-like growth factor-I (IGF-I) bioavalibility, as measured by the serum IGF-I/insulin-like growth factor binding protein-1 (IGFBP-1) ratio, was found after fasting, whereas no metabolic changes were found after bed rest. Glucagon seems to be a key regulator of IGFBP-1 after brief hypocaloric nutrition. Hypocaloric nutrition and immobilization may add to the catabolic response to surgery and other trauma. Presently, six healthy subjects were studied before and after a 24-h period of hypocaloric nutrition (200 kcal/24 h, fast) or immobilization (bed rest) using the hyperinsulinemic (0.8 mU.kg-1.min-1), normoglycemic (4.5 mmol/L) clamp, indirect calorimetry, and circulating levels of substrates and hormones. After fast, body weight decreased (P < 0.05), and nitrogen balance was negative (-10 +/- 1 g urea nitrogen/24 h). Basal levels of free fatty acids, glucagon, and IGFBP-1 increased (P < 0.05), whereas c-peptide levels and the IGF-I/IGFBP-1 ratio decreased (P < 0.05). However, no change was found in basal levels of IGF-1 or substrate oxidation. Furthermore, changes (%) in basal levels of glucagon after fast correlated to IGFBP-1 (r = 1.0, P < 0.05), whereas the suppressibility of IGFBP-1 by insulin was maintained at normal levels. During clamps, glucose infusion rates (GIR) decreased after fast (-43 +/- 13%, mean +/- SEM, P < 0.001). Although not significantly, clamp levels of fat oxidation tended to increase and glucose oxidation tended to decrease. Levels of IGFBP-1 during clamps were higher as compared with the control clamp (P < 0.05). No adverse metabolic changes were seen after bed rest, and no change in GIR during clamps were seen as compared with the control measurement (0 +/- 14%). After brief hypocaloric nutrition, insulin sensitivity is reduced, whereas IGF-I bioavalibility is reduced by an increase in levels of IGFBP-1. Glucagon seems to contribute to the increase in IGFBP-1 during these conditions.

Pancreas size and insulin secretion: lack of association in non-diabetic subjects

Both type 1 and type 2 diabetes mellitus are associated with reduced pancreatic size. This could be caused by insulinopenia with loss of a trophic insulin effect and/or other factors associated with a diabetic state. To investigate the role of long-term moderate insulinemia per se, we compared the pancreatic size in healthy subjects with documented low (n = 5) and high (n = 5) insulin secretion. Insulin responses to a glucose clamp (11 mM) procedure were threefold higher in the high insulin responders (HIR) than low insulin responders (LIR). Age, body mass index (BMI), and blood glucose were similar between groups. Computed tomography showed no difference in total pancreatic size (total pancreas volume 84.8 +/- 29.4 ml in LIR, 79.8 +/- 8.4 ml in HIR; NS) nor in the size of various parts (caput, corpus, or cauda). We conclude that moderate hypoinsulinemia of long duration does not affect the pancreatic size.

Impact of nicotinic acid treatment on insulin secretion and insulin sensitivity in low and high insulin responders

The aim of the study was to evaluate the effect of nicotinic acid (NA) on glucose tolerance, insulin secretion and sensitivity in relation to perturbations of non-esterified fatty acids (NEFA) and previously characterized insulin responses. Healthy subjects (n = 12) were treated for 14 days with incremental doses of NA reaching 2 g day-1. Before NA and on day 14 a hyperglycaemic clamp (11 mmol l-1) was performed with arginine (5 g i.v.) stimulation before and during the clamp. Fasting serum levels of NEFA were evanescently decreased on day 3 (-38%; p < 0.01) and day 7 (-33%; p < 0.05), but not on day 14 (-14%; NS). NA treatment did not significantly affect levels of fasting blood glucose, insulin, C-peptide, proinsulin or glucagon. NA treatment lowered the amount of infused glucose necessary to achieve clamp levels 48 (8) vs. 61 (10) mumol kg-1 min-1 (p < 0.01). Incremental increases in fasting NEFA levels correlated (r = -0.72) with decreased insulin sensitivity as reflected by M/I ratios (the amount of glucose infused, minus glucosuria, divided by the mean insulin level) (p < 0.01). Insulin and glucagon responses to arginine and glucose were similar before and after NA in subgroups with initially low and high insulin responses to glucose. NA-induced insulin resistance in this study is (a) less than previously reported; (b) not associated with changes in insulin secretory responsiveness, but is (c) influenced by an individually variable NA effect on fasting NEFA levels. Our results do not indicate that NA treatment can be used to test the capacity of B cells to cope with insulin resistance.

Nitric oxide donor SIN-1 inhibits insulin release

Preceding the onset of insulin-dependent diabetes mellitus, pancreatic islets are infiltrated by macrophages secreting interleukin-1 beta, which exerts cytotoxic and inhibitory actions on islet beta-cell insulin secretion through induction of nitric oxide (NO) synthesis. The influence of the NO donor 3-morpholinosydnonimine (SIN-1) on insulin secretion from isolated pancreatic islets in response to various secretagogues was investigated. Stimulation of insulin release evoked by glucose, phospholipase C activation with carbachol, and protein kinase C activation with phorbol ester were obtained by SIN-1, whereas the response to adenylyl cyclase activation or K(+)-induced depolarization was not affected. It is concluded that enzymes involved in glucose catabolism, phospholipase C or protein kinase C, may be targeted by NO. Reversal of SIN-1 inhibition of glucose-stimulated insulin release by dithiothreitol suggests that NO may inhibit insulin secretion partly by S-nitrosylation of thiol residues in key proteins in the stimulus-secretion coupling. These adverse effects of NO on the beta-cell stimulus-secretion coupling may be of importance for the development of the impaired insulin secretion characterizing diabetes mellitus.

Effects of transforming growth factor beta, tumor necrosis factor alpha and interferon gamma on pancreatic islet beta-cell responsiveness to transforming growth factor alpha

The insulin-producing pancreatic islet beta-cell, characterized by low proliferative potential, is normally not responsive to the polypeptide epidermal growth factor (EGF) or its homolog transforming growth factor alpha (TGF-alpha). Since EGF receptors in other tissues can be up-regulated by other growth factors and by cytokines, we have in this paper investigated whether such a beta-cell responsiveness to TGF-alpha, or EGF, can be conferred by co-culture with interferon gamma (IFN-gamma), tumor necrosis factor alpha (TNF-alpha) or transforming growth factor beta (TGF-beta) in various combinations. To this end, fetal rat pancreatic islets enriched in beta-cells were isolated and cultured for 3 days with or without 200 pM or 20 nM TGF-alpha. It was found that neither of these TGF-alpha concentrations affected beta-cell mitogenesis, insulin content or insulin secretion. However, IFN-gamma (1000 U/ml) evoked a modest stimulation of beta-cell replication, while suppressing insulin secretion and leaving the islet insulin content unaltered. TNF-alpha (1000 U/ml), on the other hand, affected none of these parameters either alone or in any combination with TGF-alpha or IFN-gamma. However, when TNF-alpha or IFN-gamma, either alone or in combination, were combined with the cytokine interleukin-1 beta, this resulted in islet disintegration, whereas the latter cytokine alone did not exert any gross necrotic changes evident by light microscopy. TGF-beta (500 pM) stimulated insulin secretion but did not influence islet insulin content or beta-cell mitogenesis either alone or in combination with TGF-alpha (200 pM or 20 nM). In no instance could any mitogenic or secretory response to low or high concentrations of TGF-alpha be conferred by IFN-gamma. TNF-alpha or TGF-beta whether used alone or in combinations. Hence, responsiveness to TGF-alpha or EGF in the beta-cell obviously cannot be achieved by any of these peptides.

Prostaglandins inhibit pancreatic beta-cell replication and long-term insulin secretion by pertussis toxin-insensitive mechanisms but do not mediate the actions of interleukin-1 beta

The effects of exogenous prostaglandins, inflammatory mediators known to be increased in pancreatic beta-cells by IL-1 beta, on the replication and long-term insulin secretion by beta-cells were investigated. Prostaglandins E1, E2, and F2 alpha suppressed beta-cell proliferation and long-term insulin secretion, thus mimicking the effects of IL-1 beta. The actions of prostaglandins were not prevented by pertussis toxin pretreatment. Additionally, the cyclooxygenase inhibitor indomethacin could not prevent the effects of IL-1 beta. It is concluded that prostaglandins suppress beta-cell growth and long-term insulin secretion without participation of pertussis-toxin sensitive GTP-binding proteins. In addition, although their synthesis is increased by IL-1 beta, prostaglandins seemingly do not convey the inhibitory actions of this cytokine in the beta-cell.

Identification of the human insulin negative regulatory element as a negative glucocorticoid response element

Insulin gene transcription in adults is restricted to pancreatic beta cells. Studies with both transgenic mice and islet cell lines have demonstrated that beta cell specific expression is conferred by the 5' flanking region of the insulin gene. Transfection analysis has shown that cell specific expression involved an interaction between both positive and negative promoter cis elements. An upstream region (between -258 and -279) of the human insulin promoter served as a site of negative regulation. Transfection analysis in the pancreatic cell line HIT T-15 M 2.2.2 revealed that a DNA fragment containing this region causes a 45% reduction in promoter activity when linked to the native insulin promoter and a 72% reduction when linked to a heterologous tk promoter. Electrophoretic mobility shift analysis of this negative regulatory region (NRE) reveals a complex pattern of binding, wherein two major and several minor complexes are observed. Competition experiments demonstrated that formation of the fastest mobility complex is completely inhibited with excess cold glucocorticoid responsive element (GRE) consensus oligonucleotide. Purified glucocorticoid receptor binding domain (T7X556) demonstrated binding to the NRE oligonucleotide. Functional studies showed that dexamethasone treatment of HIT T-15 M 2.2.2 cells containing an NRE-tk CAT plasmid decreased CAT gene expression by 48%. Analysis of the NRE revealed 73% homology with the negative GRE consensus sequence. These data show that the human insulin NRE is a negative glucocorticoid response element.

Disturbed anabolic hormonal patterns in burned patients: the relation to glucagon

OBJECTIVE

Complex changes in the anabolic regulators of metabolism occur after major injury. We have studied the time course for IGF-I and IGFBP-1 after burn injury and their relations to circulating levels of other anabolic and catabolic hormones. The hormonal patterns during the onset of sepsis were also investigated.

PATIENTS

Eight patients (age 36 (6) years, mean (SEM)) with major burn injury (burn area 42 (6) %) were studied. The first 2 days since the burn were used for rehydration therapy (rehydration period), after which a complete total parenteral nutrition (TPN) period was initiated. Seven positive blood cultures, during the study period. Six of the eight survived.

MEASUREMENTS

The hormonal changes determined in the morning during the first 7 days after the burn and from day 22 to 24 were investigated. The superimposed effects of sepsis were studied by normalizing all data to the day of positive blood cultures and clinical onset of sepsis.

RESULTS

On admission, plasma levels of glucagon, IGFBP-1 and GH were elevated while levels of IGF-I were low. During the first week after the burn, morning levels of glucagon and insulin increased while levels of GH and IGF-I decreased. GH levels were still elevated compared to healthy subjects. Despite the increase in insulin levels, IGFBP-1 remained elevated. Three weeks after the burn injury, IGF-I levels were increased but still markedly below normal, while IGFBP-1 levels remained unchanged. Persistent elevations of insulin levels were combined with reductions in glucagon levels. Admission levels of IGFBP-1 correlated to nitrogen loss (negative nitrogen balance) during the first 24 hours after the burn (r = 0.84, P < 0.05). A correlation between negative nitrogen balance and glucagon levels was found during early catabolic period in the rehydration period (i.e. days 2-3, r = 0.84, P < 0.01). The relative change in IGFBP-1 levels in the rehydration period correlated to changes in glucagon levels (days 2-3 vs admission, r = 0.85, P < 0.05). The insulin/glucagon molar ratio correlated to the IGF-I/IGFBP-1 ratio during both the rehydration period (days 2-3, r = 0.77, P < 0.05) and the third week after the burn (r = 0.77, P < 0.05). During the most catabolic phase in the first week after the burn (TPN period) there was an inverse relation between IGF-I and IGFBP-I and glucagon (r = 0.83, P < 0.05). During the less catabolic third week after the burn, an inverse correlation was found between IGF-I and glucagon (r = -0.83, P < 0.05). Sepsis, superimposed upon the burn trauma, was associated with transient elevations in IGFBP-1 and reductions in insulin despite elevated levels of glucose and a further 50% increase in nitrogen losses.

CONCLUSIONS

The present findings show that marked changes is important anabolic regulating factors occur after major burn injury. Uncoupling of the GH-IGF-I axis, and the attenuation of the inhibitory effects of insulin on IGFBP-1, both contribute to the reduction in IGF-I levels and bioavailability, factors which may play an important role in post injury metabolism. Furthermore, these data suggest that the catabolic hormones (catecholamines, cortisol and glucagon), primarily glucagon seem to be involved in the modulation of IGF-I and IGFBP-1 levels following burn injury.

Relationship between insulin responses to D-glucose and to L-arginine in women with a history of gestational diabetes

The relationship between insulin responses to glucose and to arginine was studied in non-obese women with previous gestational diabetes (PGD). One group, n = 10, had normal glucose tolerance (NGT) by WHO criteria and another, n = 8, had impaired glucose tolerance (IGT). A third group of women without PGD, n = 12, was also studied. A hyperglycaemic clamp (blood glucose level 11 mM) and an arginine stimulation test (150 mg/kg L-arginine followed by 10 mg/kg.min) were performed on separate days. The ratios of arginine to glucose responses 0-10 min differed: they were 1.00 for non-PGD, 1.29 for NGT and 1.46 for IGT (P < 0.02 vs non-PGD). A further difference between groups was the ratio between first- and second-phase glucose-induced insulin secretion, which was significantly decreased in IGT, 0.72, compared with NGT, 0.98 (P < 0.01), and non-PGD, 1.05 (P < 0.005). However, within each group insulin responses 0-10 min to glucose and arginine were strongly correlated: for NGT (r = 0.75, P < 0.05), for IGT (r = 0.85, P < 0.01) and for women without PGD (r = 0.69, P < 0.05). Insulin sensitivity, as assessed by the M/I ratio, was non-significantly decreased in IGT (0.18 +/- 0.03 mg/kg.min per mU/l vs 0.26 +/- 0.03 in NGT and 0.28 +/- 0.03 in non-PGD, P < 0.1).(ABSTRACT TRUNCATED AT 250 WORDS)

Insulin propeptides in conditions associated with insulin resistance in humans and their relevance to insulin measurements

Routine insulin assays measure not only biologically active insulin but also the relatively inactive propeptides, proinsulin and desdipeptide proinsulin. Such measurements may be misleading if insulin propeptide levels are increased, as has been reported in patients with non-insulin-dependent diabetes mellitus (NIDDM). Inferences regarding insulin resistance, based on hyperinsulinemia, could thus be invalidated where routine insulin assays have been used. We have measured plasma insulin levels using a routine assay, together with measurements of the major circulating insulin propeptides, intact proinsulin and des 31,32proinsulin, in various clinical situations associated with apparently increased insulin levels and insulin resistance. Major increases of insulin propeptide levels relative to insulin levels were not seen in obese subjects or in patients taking oral contraceptives or danazol, or in obese subjects compared with non-obese controls. Although the insulinemic responses observed with routine radioimmunoassay in these situations associated with insulin resistance are not confounded by major changes in the proportion of circulating insulin propeptides, further studies will be necessary to validate investigations in other insulin-resistant states.

A high-molecular IGF-2 immunoreactive peptide (pro-IGF-2?) in the insulin cells of the islets of Langerhans in pancreas of man and rat

Histopathologically normal pancreatic parenchyma from 12 adult men and women, as well as that from 14 adult rats (Sprague-Dawley and Wistar strains), were investigated immunohistochemically with a mouse monoclonal antibody, raised against recombinant human pro-IGF-2. The antiserum showed no crossreactivity with insulin; IGF-1 had 0.1% of the reactivity of IGF-2. The immunohistochemical observations were checked by means of a radioimmunoassay (RIA), based on the same antibody, of an extract of a sample of one of the human pancreatic glands. Analogous investigations for insulin were made in parallel, using polyclonal insulin antisera. A high-molecular (12 kDa) IGF-2-like peptide was found in the islets of Langerhans, being localized to the insulin cells. These cells were identified as beta-cells by immunohistochemistry with insulin antisera on adjacent paraffin sections. From observations made by means of acid-gel-chromatography, the peptide was tentatively supposed to represent either pro-IGF-2, or a partially processed form of it.

Prednisolone enhances beta-cell function independently of ambient glycemic levels in type II diabetes

This study examined the changes in beta-cell response and insulin sensitivity induced by a single overnight dose of 15 mg prednisolone in eight type II diabetic subjects, seven nondiabetic normal controls, and eight subjects with a first-degree type II diabetic relative who were therefore at risk of developing diabetes. beta-Cell secretion was assessed by use of the hyperglycemic clamp technique, and insulin sensitivity was assessed with the clamp and the Continuous Infusion of Glucose with Model Assessment (CIGMA) technique. Subjects were studied in random order on two occasions, after placebo and after prednisolone administration. Normal subjects showed an increase of median fasting glucose level from 4.7 to 5.2 mmol.L-1 after prednisolone (P < .02) and at-risk subjects showed an increase from 4.8 to 5.5 mmol.L-1 (P < .005), whereas diabetic subjects showed no significant increase in median fasting plasma glucose level (7.0 mmol.L-1 after placebo and 6.3 mmol.L-1 after prednisolone). Six of these eight diabetic subjects showed a paradoxical decrease of fasting plasma glucose level after prednisolone therapy. All three groups showed a significant elevation of clamp steady-state plasma insulin levels following prednisolone, with a median percentage elevation of 46%, 66%, and 31% for normal, at-risk, and diabetic subjects, respectively. All three groups showed significant reduction in insulin sensitivity measured by CIGMA following prednisolone of 51%, 41%, and 25% of pre-prednisolone levels in normal, at-risk, and diabetic subjects, respectively, with a significantly greater reduction in normal subjects than in diabetics (P < .02).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of early hyperlipidemia on graft and patient survival in cyclosporine-treated renal transplant patients

Hyperlipidemia commonly occurs following renal transplantation. As hyperlipidemia has been postulated to contribute to renal dysfunction in animal models, the effect of early hyperlipidemia was studied in a cohort of 43 cyclosporine-treated renal transplant recipients over a 4-year follow-up period. Hypercholesterolemia occurred in 25 patients, with 18 patients remaining normolipidemic during the initial 3 months following transplantation. Prospective follow-up over a 4-year period was available for 16 of the 18 normolipidemic patients and 25 patients who developed hyperlipidemia, as well as 11 other hyperlipidemic patients who were not included in the initial analysis. Graft function was maintained in 11 (69%) of the patients with early normolipidemia and there has been one patient death (7%). Of the hypercholesterolemic group, two patients were lost to follow-up and 23 of the remaining 34 (68%) had persistent graft function. There have been two patient deaths (6%). No deaths from cardiovascular deaths have occurred in either group, all deaths resulting from infection/sepsis. Mean cholesterol values at 4-year follow-up were 202.0 +/- 11.2 mg/dL for the patients with early normolipidemia 282.9 +/- 14.3 mg/dL for the patients with early hyperlipidemia (p < 0.00001). The most recent cholesterol value was not associated with pretransplant cholesterol value, creatinine, or cyclosporine dose, but was associated with cholesterol value at 3 months both by regression analysis (P < 0.0001) and by Pearson R (r = 0.71, P < 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

The diabetogenic effects of glucocorticoids are more pronounced in low- than in high-insulin responders

We investigated in six low- and six high-insulin responders (LIR and HIR) the effect of dexamethasone (Dex, 15 mg orally during 48 hr) on oral glucose tolerance (OGTT), glucose turnover under basal conditions and during glucose infusion of 2 mg.kg-1.min-1, and insulin response during hyperglycemic clamp. Dex increased fasting glucose more in LIR (P less than 0.05). During OGTT, Dex caused a more prominent increment in glucose in LIR, whereas the increment in insulin was less in LIR (P less than 0.05). After Dex, in three LIR but in no HIR, a diabetic OGTT was observed. Dex significantly increased basal hepatic glucose production (turnover measured with [6-3H]glucose), hepatic total glucose output (turnover measured with [2-3H]glucose), and glucose cycling (hepatic total glucose output--hepatic glucose production) only in LIR. Dex decreased basal glucose metabolic clearance to the same extent in LIR and HIR. Hyperglycemic clamp revealed that Dex induced a significant increase (P less than 0.05) in insulin response only in HIR. Dex effects on insulin release during hyperglycemic clamp were negatively correlated with the glucose area during Dex OGTT (P less than 0.01). Thus, the double tracer method provided a new insight into the pathogenesis of the steroid effect on carbohydrate tolerance. Dex increased basal glycemia more in LIR because only in LIR was glucose production increased. During OGTT, the LIR who were not able to counteract the effects of Dex by an appropriate enhancement in insulin secretion developed a decreased OGTT. The evaluation of insulin response after Dex may thus allow differentiation of the subset of LIR that run an increased risk of non-insulin-dependent diabetes mellitus.