Direct glucocorticoid inhibition of insulin secretion. An in vitro study of dexamethasone effects in mouse islets

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.

Steroid-induced diabetes: is it just unmasking of type 2 diabetes?

Aims. We compared the demographic profile and clinical characteristics of individuals with new onset steroid-induced diabetes (NOSID) to Type 2 diabetes (T2DM) patients with and without steroid treatment. Methods. The demographic profile and clinical characteristics of 60 individuals who developed NOSID were examined and matched to 60 type 2 diabetes patients receiving steroid therapy (T2DM+S) and 360 diabetic patients not on steroids (T2DM) for age, duration of diabetes, HbA1c, gender, and ethnicity. Results. Patients who developed NOSID had less family history of diabetes (P ≤ 0.05) and were less overweight (P ≤ 0.02). NOSID was more commonly treated with insulin. Despite a matching duration of diabetes and glycaemic control, significantly less retinopathy was found in the group of patients with NOSID (P < 0.03). Conclusions. It appears that steroid treatment primarily precipitated diabetes in a group of individuals otherwise less affected by risk factors of diabetes at that point in time, rather than just opportunistically unmasking preexisting diabetes. Furthermore, the absence of retinopathy suggests that patients with NOSID had not been exposed to long periods of hyperglycaemia. However, the impact of the underlying conditions necessitating steroid treatment and concomitant medications such as immunosuppressants on diabetes development remain to be defined.

Postnatal maternal separation modifies the response to an obesogenic diet in adulthood in rats

An early-life adverse environment has been implicated in the susceptibility to different diseases in adulthood, such as mental disorders, diabetes and obesity. We analyzed the effects of a high-fat sucrose (HFS) diet for 35 days in adult female rats that had experienced 180 minutes daily of maternal separation (MS) during lactancy. Changes in the obesity phenotype, biochemical profile, levels of glucocorticoid metabolism biomarkers, and the expression of different obesity- and glucocorticoid-metabolism-related genes were analyzed in periovaric adipose tissue. HFS intake increased body weight, adiposity and serum leptin levels, whereas MS decreased fat pad masses but only in rats fed an HFS diet. MS reduced insulin resistance markers but only in chow-fed rats. Corticosterone and estradiol serum levels did not change in this experimental model. A multiple gene expression analysis revealed that the expression of adiponutrin (Adpn) was increased owing to MS, and an interaction between HFS diet intake and MS was observed in the mRNA levels of leptin (Lep) and peroxisome proliferator-activated receptor gamma coactivator 1 alpha (Ppargc1a). These results revealed that early-life stress affects the response to an HFS diet later in life, and that this response can lead to phenotype and transcriptomic changes.

Prevalence of endocrine disorders in morbidly obese patients and the effects of bariatric surgery on endocrine and metabolic parameters

BACKGROUND

Several endocrine abnormalities, including hypothyroidism and Cushing's syndrome (CS), are considered as causative factors of obesity. The aim of this study was to evaluate the prevalence of endocrine disorders and obesity-associated co-morbidities, as well as the impact of substantial weight loss.

METHODS

Screening was performed in 433 consecutive morbidly obese patients (age 41 ± 12 years; BMI 47 ± 6.9 kg/m(2); women 76%). A 1-mg dexamethasone suppression test (1-mg DST) was conducted to exclude CS, and thyrotropin (TSH) was measured to exclude hypothyroidism. Insulin sensitivity was estimated from oral glucose tolerance tests employing the Clamp-like index. Examinations were carried out at baseline, as well as at 6 and 12 months postoperatively.

RESULTS

The prevalence of CS was below 0.6%. Before surgery, TSH was elevated compared to an age- and sex-matched normal weight control group (2.4 ± 1.2 vs. 1.5 ± 0.7 μU/ml; p < 0.001). The NCEP criteria of metabolic syndrome (MetS) were fulfilled by 39.5% of the patients. Impaired glucose tolerance and diabetes mellitus were observed in 23.5% and 22.6%, respectively. Seventy-two percent were insulin resistant. During follow-up, weight (BMI 47 ± 6.9 vs. 36 ± 6.4 vs. 32 ± 6.6 kg/m(2); p < 0.001) and TSH decreased significantly (2.4 ± 1.2 vs. 1.8 ± 1.0 vs. 1.8 ± 1.0 μU/ml; p < 0.001). Serum cortisol was higher in the MetS(+)-group compared to the MetS(-)-group (15.0 ± 6.3 vs. 13.5 ± 6.3 μg/dl; p = 0.003).

CONCLUSIONS

CS appears to be a rare cause of morbid obesity. Normalization of slightly elevated thyrotropin after weight loss suggests that obesity causes TSH elevation rather than the reverse.

Depression and type 2 diabetes: cortisol pathway implication and investigational needs

Depression and type 2 diabetes (T2D) are clinically associated and the causes of the association are still under investigation. We aimed at identifying what is known about the stress response and cortisol pathway and the clinical association of depression and T2D, and at hypothesizing the link of the association. In this review, we report independent studies on stress response, cortisol pathway, depression, T2D, and independent studies on stress and cortisol pathway in depression, and in T2D. We focus and integrate the stress and cortisol pathway hypothesis to explain the clinical association of depression and T2D. We hypothesize that the corticotropin-releasing hormone receptors are one of the missing linking factor of the cortisol pathway underlying the clinical association of depression and T2D. We state what studies are still needed to confirm or rule out our hypothesis.

Involvement of thioredoxin-interacting protein (TXNIP) in glucocorticoid-mediated beta cell death

AIM/HYPOTHESIS

Glucocorticoid hormones (GCs) are widely used to treat a variety of inflammatory and immune diseases. However, their long-term administration is associated with adverse metabolic effects, including glucose intolerance and diabetes. Our objective was to elucidate the mechanisms by which GCs affect beta cell survival with a specific emphasis on the role of the thioredoxin-interacting protein (TXNIP) in beta cell apoptosis.

METHODS

Human and mouse islets, together with MIN6 beta cells, were exposed to dexamethasone (Dex) and apoptosis was assessed by measuring the percentage of sub-G1 cells, the appearance of cleaved caspase-3 or by using a TUNEL assay. Dex-upregulated expression of Txnip mRNA was analysed by real-time PCR, and GC-modulated production and modification of proteins were determined by western blotting.

RESULTS

We provide evidence that TXNIP, a negative regulator of the antioxidant thioredoxin (TRX), is strongly induced in beta cells by GCs and that its induction is dependent on p38 mitogen-activated protein kinase (MAPK) activation. TXNIP downregulation by RNA interference, overexpression of the radical scavenger TRX1 or elevation of intracellular cAMP levels attenuated the Dex-mediated apoptosis. Dex-induced Txnip expression and beta cell apoptosis are mediated by the glucocorticoid receptor (GR), as the GR antagonist RU486 fully abolishes these effects.

CONCLUSIONS/INTERPRETATION

Altogether, our data suggest TXNIP as a novel mediator of GC-induced apoptosis in beta cells and further contribute to our understanding of beta cell death pathways.

Progressively increased patterns of subclinical cortisol hypersecretion in adrenal incidentalomas differently predict major metabolic and cardiovascular outcomes: a large cross-sectional study

BACKGROUND

Subclinical Cushing's syndrome (SCS) is defined as alterations in hypothalamic-pituitary-adrenal axis without classic signs/symptoms of glucocorticoid excess. Whether SCS leads to metabolic and cardiovascular diseases is still controversial.

AIM

To evaluate the prevalence of hypertension, type 2 diabetes (T2D), coronary heart disease (CHD), ischemic stroke, osteoporosis, and fractures, and their relationship to increasing patterns of subclinical hypercortisolism, in patients with nonsecreting adrenal adenomas (NSA) and SCS.

METHODS

Using the 1 mg dexamethasone suppression test (DST), 348 patients were classified as follows: 203 were defined as NSA and 19 SCS, using the most stringent cutoff values (<50 and >138 nmol/l respectively). Patients with cortisol post-DST (50-138 nmol/l) were considered as intermediate phenotypes and classified as minor (n=71) and major (n=55) using plasma ACTH and/or urinary free cortisol as additional diagnostic tools.

RESULTS

SCS patients showed higher prevalence of T2D, CHD, osteoporosis, and fractures with respect to NSA. Intermediate phenotypes also showed higher prevalence of CHD and T2D with respect to NSA. The prevalence of all clinical outcomes was not different between intermediate phenotype patients, which were therefore considered as a single group (IP) for multivariate logistic regression analysis: both IP and SCS-secreting patterns showed a significant association with CHD (odds ratio (OR), 4.09; 95% confidence interval (CI), 1.47-11.38 and OR, 6.10; 95% CI, 1.41-26.49 respectively), independently of other potential risk factors. SCS was also independently associated with osteoporosis (OR, 5.94; 95% CI, 1.79-19.68).

CONCLUSIONS

Patterns of increasing subclinical hypercortisolism in adrenal adenomas are associated with increased prevalence of adverse metabolic and cardiovascular outcomes, independently of other potential risk factors.

Stress-induced hyperglycemia in healthy bungee jumpers without diabetes due to decreased pancreatic β-cell function and increased insulin resistance

BACKGROUND

Acute diseases are associated with increased stress and immune responses. Both of these responses are associated with disturbances of glucose metabolism, and it is therefore difficult to ascertain whether these disturbances are related to increased stress alone or a result of the systemic inflammatory response. We investigated the effects that acute stress has on glucose metabolism in an acute stress model that is not accompanied by an increased immune response.

SUBJECTS AND METHODS

Glucose levels as well as pancreatic β-cell function, insulin resistance, and parameters of stress and immune responses were assessed in healthy bungee jumpers 2 h before, immediately before, and after the jump.

RESULTS

Glucose levels and stress hormones were increased, right before and after the jump, whereas the immune response was decreased. Pancreatic β-cell function was decreased right before the jump, and insulin resistance was increased right after the jump. Higher levels of cortisol correlated with increased insulin resistance after the jump. Furthermore, larger increments of cortisol before and of epinephrine after the jump were associated with decreased pancreatic β-cell function.

CONCLUSIONS

Acute stress in healthy bungee jumpers induces acute disturbances of glucose metabolism that are independent from a systemic inflammatory response.

Influence of tail versus cardiac sampling on blood glucose and lipid profiles in mice

Blood is collected during animal experimentation to measure haematological and metabolic parameters. It cannot be assumed that circulating blood has the same composition irrespective of its location, and indeed, differences in the composition of blood sampled from the arterial and venous compartments have been reported. Here we investigated whether blood collected by cardiac puncture (CP) versus that collected following removal of the distal 1 mm of the tail tip (TT) differs with respect to glucose and lipid profiles in male C57BL/6J mice at 4, 7, 20 and 28 weeks of age. Blood was first collected from the TT of unanaesthetized mice, which were then immediately anaesthetized using ketamine/xylazine, and a second blood sample was collected by CP. The CP glucose concentration was significantly higher than TT glucose by a positive bias averaging +80% (P < 0.01), irrespective of the age of the mice. Conversely, the concentrations of the CP lipids, including total cholesterol, high-density lipoprotein cholesterol and triglyceride were lower than TT lipids by a negative bias averaging -25% (P < 0.05). These observations highlight the difficulty in measuring and comparing metabolic parameters such as glucose and lipid between one blood compartment and another. They illustrate the need to standardize sampling sites, especially when repeated blood sampling is required.

Optimal elevation of β-cell 11β-hydroxysteroid dehydrogenase type 1 is a compensatory mechanism that prevents high-fat diet-induced β-cell failure

Type 2 diabetes ultimately results from pancreatic β-cell failure. Abnormally elevated intracellular regeneration of glucocorticoids by the enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) in fat or liver may underlie pathophysiological aspects of the metabolic syndrome. Elevated 11β-HSD1 is also found in pancreatic islets of obese/diabetic rodents and is hypothesized to suppress insulin secretion and promote diabetes. To define the direct impact of elevated pancreatic β-cell 11β-HSD1 on insulin secretion, we generated β-cell-specific, 11β-HSD1-overexpressing (MIP-HSD1) mice on a strain background prone to β-cell failure. Unexpectedly, MIP-HSD1(tg/+) mice exhibited a reversal of high fat-induced β-cell failure through augmentation of the number and intrinsic function of small islets in association with induction of heat shock, protein kinase A, and extracellular signal-related kinase and p21 signaling pathways. 11β-HSD1(-/-) mice showed mild β-cell impairment that was offset by improved glucose tolerance. The benefit of higher β-cell 11β-HSD1 exhibited a threshold because homozygous MIP-HSD1(tg/tg) mice and diabetic Lep(db/db) mice with markedly elevated β-cell 11β-HSD1 levels had impaired basal β-cell function. Optimal elevation of β-cell 11β-HSD1 represents a novel biological mechanism supporting compensatory insulin hypersecretion rather than exacerbating metabolic disease. These findings have immediate significance for current therapeutic strategies for type 2 diabetes.

[Corticosteroids and diabetes mellitus]

During corticosteroid prescriptions, diabetes mellitus may be completely deregulated or may be revealed as such. Predisposition to diabetes mellitus could be because of latent β Langerhans cell deregulation or because enhancement of tissue sensitivity by glucocorticosteroids. However, epidemiologic data concerning predisposing factors and frequency of cortico-induced diabetes are not well known. Detection, treatment and prevention are the same as for type II diabetes. Glycemia should be monitored throughout long-term treatments.

Association of hyperglycemia, glucocorticoids, and insulin use with morbidity and mortality in the pediatric intensive care unit

BACKGROUND

Studies of pediatric intensive care unit (PICU) patients have shown a significant association of morbidity and mortality with hyperglycemia. We retrospectively evaluated the degree of hyperglycemia as well as its correlation with glucocorticoid and insulin use and assessed its association with hospital length of stay (LOS) and mortality. This study preceded the initiation of a standard glycemic control protocol.

METHODS

We examined medical records at Kosair Children's Hospital for all PICU admissions from 2008 of patients without diabetes mellitus. Critical illness hyperglycemia (CIH) was defined by having three or more peak glucose values greater than thresholds of 110, 140, 180, and 200 mg/dl. These patients were evaluated for glucocorticoid, insulin use, and outcome measures.

RESULTS

We evaluated the eligible 1173 admissions, where 10.5% of these patients reached the highest threshold (200 mg/dl) of CIH. Glucocorticoids were used in 43% of these patients, with dexamethasone being the most common (58%). There was a significant correlation between glucocorticoids and higher peak glucose values, where 81% of the patients who were above the 200 mg/dl cutoff level were treated with glucocorticoids. Only 36.8% in that group were also treated with insulin. Patients at the 200 mg/dl cutoff had the highest median PICU and total hospital length of stays (4 and 10 days, respectfully). Mortality was associated with increasing glucose levels, reaching 18.7% among patients above the 200 mg/dl cutoff.

CONCLUSION

Hyperglycemia was prevalent in the PICU and was associated with increased morbidity, as characterized by increased LOS and increased mortality. Glucocorticoid use was prevalent among patients exhibiting hyperglycemia. Insulin use was uncommon.

Gipr is essential for adrenocortical steroidogenesis; however, corticosterone deficiency does not mediate the favorable metabolic phenotype of Gipr(-/-) mice

Glucose-dependent insulinotropic polypeptide (GIP) promotes glucose-dependent insulin secretion. However, GIP also enhances glucocorticoid secretion and promotes adiposity. Because obesity and diabetes are glucocorticoid dependent, we examined whether the effects of GIP on energy balance and glycemia are regulated by glucocorticoids using pharmacological activation of GIP receptor (GIPR) signaling with [d-Ala(2)]GIP in mice and in Y1 adrenocortical cells. Genetic elimination of GIPR activity was also studied in normal- and high-fat (HF)-fed Gipr-deficient (Gipr(-/-)) mice. [d-Ala(2)]GIP increased murine corticosterone levels in a GIPR-dependent manner. Conversely, basal corticosterone levels were reduced, whereas food deprivation resulted in significantly enhanced plasma corticosterone levels in Gipr(-/-) mice. [d-Ala(2)]GIP increased cAMP levels, activated extracellular signal\x{2013}related kinase (ERK)1/2, increased expression of steroidogenic genes, and increased neutral lipid storage in Y1GIPR cells. Gipr(-/-) adrenal glands demonstrated a twofold upregulation of the ACTH receptor mRNA and increased sensitivity to ACTH ex vivo. Although HF-fed Gipr(-/-) mice exhibited significantly lower plasma corticosterone, glucocorticoid-treated HF-fed Gipr(-/-) mice had similar energy balance and glycemia compared with Gipr(+)(/+) controls. Hence, although the Gipr is essential for adrenal steroidogenesis and links HF feeding to increased levels of corticosterone, reduced glucocorticoid levels do not significantly contribute to the enhanced metabolic phenotypes in HF-fed Gipr(-/-) mice.

N-acetylcysteine protects pancreatic islet against glucocorticoid toxicity

OBJECTIVES

Reactive oxygen species (ROS) are involved in many physiological and pathological processes. In the present study, we analysed whether the synthetic glucocorticoid dexamethasone induces oxidative stress in cultured pancreatic islets and whether the effects of dexamethasone on insulin secretion, gene expression, and viability can be counteracted by concomitant incubation with N-acetylcysteine (NAC).

METHODS

ROS production was measured by dichlorofluorescein (DCFH-DA) assay, insulin secretion by radioimmunoassay, intracellular calcium dynamics by fura-2-based fluorescence, gene expression by real-time polymerase chain reaction analyses and cell viability by the MTS assay.

RESULTS

Dexamethasone (Dexa) increased ROS production and decreased glucose-stimulated insulin secretion after 72 hours incubation. Intracellular ROS levels were decreased and the insulin secretion capacity was recovered by concomitant treatment with Dexa+NAC. The total insulin content and intracellular Ca2+ levels were not modulated in either Dexa or Dexa+NAC groups. There was a decrease in the NAD(P)H production, used as an indicator of viability, after dexamethasone treatment. Concomitant incubation with NAC returned viability to control levels. Dexa also decreased synaptotagmin VII (SYT VII) gene expression. In contrast, the Dexa+NAC group demonstrated an increased expression of SYT VII compared to controls. Surprisingly, treatment with NAC decreased the gene expression of the antioxidant enzyme copper zinc superoxide dismutase soluble.

DISCUSSION

Our results indicate that dexamethasone increases ROS production, decreases viability, and impairs insulin secretion in pancreatic rat islets. These effects can be counteracted by NAC, which not only decreases ROS levels but also modulates the expression of genes involved in the secretory pathway and those coding for antioxidant enzymes.

Prevention and management of transplant-associated diabetes

INTRODUCTION

New-onset diabetes after transplantation (NODAT) is considered to be a major cause of cardiovascular disease and death among patients with a functioning allograft. A major challenge is to reduce the incidence of NODAT and to treat it optimally once it has occurred.

AREAS COVERED

This review presents current data on how to prevent NODAT in patients at risk, with a focus on modifications in the immunosuppressive regimen. Current suggestions for detection and treatment of NODAT are also presented.

EXPERT OPINION

Prevention of NODAT is possible by assessing the patient's glycemic risk prior to transplantation and tailoring the treatment (e.g., choice and dosage of immunosuppressive agents) after transplantation. An oral glucose tolerance test is still the gold standard to detect NODAT in patients at risk (prediabetes) but algorithms can be used to select those who should be tested. The treatment of NODAT involves a broad approach on risk factors for cardiovascular events and graft loss. Future studies on the use of oral hypoglycemic agents in NODAT are still needed.

Impairment of rat fetal beta-cell development by maternal exposure to dexamethasone during different time-windows

Aim

Glucocorticoids (GCs) take part in the direct control of cell lineage during the late phase of pancreas development when endocrine and exocrine cell differentiation occurs. However, other tissues such as the vasculature exert a critical role before that phase. This study aims to investigate the consequences of overexposure to exogenous glucocorticoids during different time-windows of gestation for the development of the fetal endocrine pancreas.

Methods

Pregnant Wistar rats received dexamethasone acetate in their drinking water (1 µg/ml) during the last week or throughout gestation. Fetuses and their pancreases were analyzed at day 15 and 21 of gestation. Morphometrical analysis was performed on pancreatic sections after immunohistochemistry techniques and insulin secretion was evaluated on fetal islets collected in vitro.

Results

Dexamethasone given the last week or throughout gestation reduced the beta-cell mass in 21-day-old fetuses by respectively 18% or 62%. This was accompanied by a defect in insulin secretion. The alpha-cell mass was reduced similarly. Neither islet vascularization nor beta-cell proliferation was affected when dexamethasone was administered during the last week, which was however the case when given throughout gestation. When given from the beginning of gestation, dexamethasone reduced the number of cells expressing the early marker of endocrine lineage neurogenin-3 when analyzed at 15 days of fetal age.

Conclusions

GCs reduce the beta- and alpha-cell mass by different mechanisms according to the stage of development during which the treatment was applied. In fetuses exposed to glucocorticoids the last week of gestation only, beta-cell mass is reduced due to impairment of beta-cell commitment, whereas in fetuses exposed throughout gestation, islet vascularization and lower beta-cell proliferation are involved as well, amplifying the reduction of the endocrine mass.

Management of the hyperglycemic inpatient: tips, tools, and protocols for the clinician

Inpatient hyperglycemia is increasingly recognized as a contributor to in-hospital complications and prolonged hospital stays. Protocols to assist in management of hyperglycemia are becoming more widely used and have been shown to improve outcomes for hyperglycemic patients. In this article, several evidence-based protocols are reviewed for use by hospital-based clinicians, both for subcutaneous and intravenous insulin. Clinicians should consider implementing protocols for hyperglycemia management in the inpatient setting.

Clinical outcome of subclinical Cushing's syndrome after surgical and conservative treatment

Subclinical Cushing's syndrome (SCS), a subtle cortisol hypersecretion from an adrenal tumor, may be a common adrenal disease. However, the cardiovascular prognosis and the optimal surgical and conservative treatment in SCS remain elusive. The present study was undertaken to evaluate the prevalence of cardiovascular risk factors in 16 SCS cases, their relationships to cortisol secretory activities, and the clinical outcome after surgical and medical treatment. The prevalence of hypertension, impaired glucose tolerance (IGT), diabetes mellitus (DM), dyslipidemia and obesity in our SCS cases were 56%, 50%, 50%, and 19%, respectively, and 75% of cases were associated with two or more cardiovascular risk factors. In our series, 24-h urinary free-cortisol excretion showed a significant positive correlation with HbA1c and a negative correlation with high-density lipoprotein-cholesterol, but no correlation with age, body mass index, blood pressure or glycemic and lipid profile was found. Eight cases underwent unilateral adrenalectomy (operated (OP) group); the remaining eight cases were a conservative-treatment group (non-OP group). The number of cardiovascular risk factors decreased significantly in the OP group, but not in the non-OP group. In terms of differential changes in risk factors between the groups, more significant improvements of hypertension, dyslipidemia and IGT/DM were observed in the OP group than in the non-OP group. In conclusion, the present study showed the increased prevalence of cardiovascular risk factors in SCS patients with mild hypercortisolism related to impaired glucose/lipid metabolism. Adrenalectomy decreased accumulated cardiovascular risk factors in certain SCS patients, suggesting the possible involvement of mild hypercortisolism in the development of cardiovascular risk factors in SCS.

Effect of dexamethasone on insulin secretion: examination of underlying mechanisms

OBJECTIVE

To study the mechanism of increased insulin secretion in response to short-term administration of dexamethasone.

METHODS

Male Wistar rats were injected intraperitoneally with dexamethasone (dexamethasone; 200 mcg/kg body weight per day) or saline for 3 consecutive days. Insulin secretion in response to glucose, ionomycin, and KCl was quantified in islets isolated from the animals, and the amount of glucokinase was measured by Western blot.

RESULTS

Dexamethasone-treated animals had 1.18-fold higher fasting blood glucose concentration and 6.5-fold increase in fasting serum insulin concentration compared with findings from animals injected with saline. Compared with islets isolated from control rats, islets from dexamethasone-treated rats secreted more insulin at 60 minutes in response to 5.5 mM glucose (416.4 vs 115.6 fmoles/10 islets, P = .011) and in response to 16.6 mM glucose (985.5 vs 520.6 fmoles/10 islets, P = .014); no change in insulin secretion was observed at 10 minutes. Insulin secretion from islets of dexamethasone-treated rats and control rats was not differentially augmented in response to either ionomycin or potassium chloride. Glucokinase expression was not altered by treatment with dexamethasone.

CONCLUSIONS

Augmentation of insulin secretion in response to glucose in the pancreatic islets from dexamethasone-treated rats is preserved in islets studied in vitro. The increase in glucose-stimulated insulin secretion appears to be mediated by steps upstream to β-cell membrane depolarization and the attended increase in intracellular calcium in the signaling pathway of insulin secretion.

5'AMP-activated protein kinase activity is increased in adipose tissue of northern elephant seal pups during prolonged fasting-induced insulin resistance

Northern elephant seals endure a 2- to 3-month fast characterized by sustained hyperglycemia, hypoinsulinemia, and increased plasma cortisol and free fatty acids, conditions often seen in insulin-resistant humans. We had previously shown that adipose Glut4 expression and 5'AMP-activated protein kinase (AMPK) activity increase and plasma glucose decreases in fasting seals suggesting that AMPK activity contributes to glucose regulation during insulin-resistant conditions. To address the hypothesis that AMPK activity increases during fasting-induced insulin resistance, we performed glucose tolerance tests (GTT) on early (n=5) and late (n=8)-fasted seal pups and compared adipose tissue expression of insulin signaling proteins, peroxisome proliferator-activated receptor γ (PPARγ), and AMPK, in addition to plasma adiponectin, leptin, cortisol, insulin, and non-esterified fatty acid (NEFA) levels. Fasting was associated with decreased glucose clearance, plasma insulin and adiponectin, and intracellular insulin signaling, as well as increased plasma cortisol and NEFAs, supporting the suggestion that seals develop insulin resistance late in the fast. The expression of Glut4 and VAMP2 increased (52 and 63% respectively) with fasting but did not change significantly during the GTT. PPARγ and phosphorylated AMPK did not change in the early fasted seals, but increased significantly (73 and 50% respectively) in the late-fasted seals during the GTT. Increased AMPK activity along with the reduction in the activity of insulin-signaling proteins supports our hypothesis that AMPK activity is increased following the onset of insulin resistance. The association between increased AMPK activity and Glut4 expression suggests that AMPK plays a greater role in regulating glucose metabolism in mammals adapted to prolonged fasting than in non-fasting mammals.

The liver receptor homolog-1 (LRH-1) is expressed in human islets and protects {beta}-cells against stress-induced apoptosis

Liver receptor homolog (LRH-1) is an orphan nuclear receptor (NR5A2) that regulates cholesterol homeostasis and cell plasticity in endodermal-derived tissues. Estrogen increases LRH-1 expression conveying cell protection and proliferation. Independently, estrogen also protects isolated human islets against cytokine-induced apoptosis. Herein, we demonstrate that LRH-1 is expressed in islets, including β-cells, and that transcript levels are modulated by 17β-estradiol through the estrogen receptor (ER)α but not ERβ signaling pathway. Repression of LRH-1 by siRNA abrogated the protective effect conveyed by estrogen on rat islets against cytokines. Adenoviral-mediated overexpression of LRH-1 in human islets did not alter proliferation but conferred protection against cytokines and streptozotocin-induced apoptosis. Expression levels of the cell cycle genes cyclin D1 and cyclin E1 as well as the antiapoptotic gene bcl-xl were unaltered in LRH-1 expressing islets. In contrast, the steroidogenic enzymes CYP11A1 and CYP11B1 involved in glucocorticoid biosynthesis were both stimulated in transduced islets. In parallel, graded overexpression of LRH-1 dose-dependently impaired glucose-induced insulin secretion. Our results demonstrate the crucial role of the estrogen target gene nr5a2 in protecting human islets against-stressed-induced apoptosis. We postulate that this effect is mediated through increased glucocorticoid production that blunts the pro-inflammatory response of islets.

Impact of glucocorticoids on insulin resistance in the critically ill

Glucocorticoids (GCs) have been shown to reduce insulin sensitivity in healthy individuals. Widely used in critical care to treat a variety of inflammatory and allergic disorders, they may inadvertently exacerbate stress-hyperglycaemia. This research uses model-based methods to quantify the reduction in insulin sensitivity from GCs in critically ill patients, and thus their impact on glycaemic control. A model-based measure of insulin sensitivity (S(I)) was used to quantify changes between two matched cohorts of 40 intensive care unit (ICU) patients. Patients in one cohort received GC treatment, while patients in the control cohort did not. All patients were admitted to the Christchurch hospital ICU between 2005 and 2007 and spent at least 24h on the SPRINT glycaemic control protocol. A 31% reduction in whole-cohort median insulin sensitivity was seen between the control cohort and patients receiving glucocorticoids with a median dose equivalent to 200mg/d of hydrocortisone per patient. Comparing percentile patients as a surrogate for matched patients, reductions in median insulin sensitivity of 20%, 25%, and 21% were observed for the 25th-, 50th- and 75th-percentile patients, respectively. These cohort and percentile patient reductions are less than or equivalent to the 30-62% reductions reported in healthy subjects especially when considering the fact that the GC doses in this study are 1.3-4.0 times larger than those in studies of healthy subjects. This reduced suppression of insulin sensitivity in critically ill patients could be a result of saturation due to already increased levels of catecholamines and cortisol common in critically illness. Virtual trial simulation showed that reductions in insulin sensitivity of 20-30% associated with glucocorticoid treatment in the ICU have limited impact on glycaemic control levels within the context of the SPRINT protocol.

Glucagon-like peptide-1 receptor agonist treatment prevents glucocorticoid-induced glucose intolerance and islet-cell dysfunction in humans

OBJECTIVE

Glucocorticoids (GCs) are regarded as diabetogenic because they impair insulin sensitivity and islet-cell function. This study assessed whether treatment with the glucagon-like peptide receptor agonist (GLP-1 RA) exenatide (EXE) could prevent GC-induced glucose intolerance.

RESEARCH DESIGN AND METHODS

A randomized, placebo-controlled, double-blind, crossover study in eight healthy men (age: 23.5 [20.0-28.3] years; BMI: 26.4 [24.3-28.0] kg/m(2)) was conducted. Participants received three therapeutic regimens for 2 consecutive days: 1) 80 mg of oral prednisolone (PRED) every day (q.d.) and intravenous (IV) EXE infusion (PRED+EXE); 2) 80 mg of oral PRED q.d. and IV saline infusion (PRED+SAL); and 3) oral placebo-PRED q.d. and intravenous saline infusion (PLB+SAL). On day 1, glucose tolerance was assessed during a meal challenge test. On day 2, participants underwent a clamp procedure to measure insulin secretion and insulin sensitivity.

RESULTS

PRED+SAL treatment increased postprandial glucose levels (vs. PLB+SAL, P = 0.012), which was prevented by concomitant EXE (vs. PLB+SAL, P = NS). EXE reduced PRED-induced hyperglucagonemia during the meal challenge (P = 0.018) and decreased gastric emptying (vs. PRED+SAL, P = 0.028; vs. PLB+SAL, P = 0.046). PRED+SAL decreased first-phase glucose- and arginine-stimulated C-peptide secretion (vs. PLB+SAL, P = 0.017 and P = 0.05, respectively), whereas PRED+EXE improved first- and second-phase glucose- and arginine-stimulated C-peptide secretion (vs. PLB+SAL; P = 0.017, 0.012, and 0.093, respectively).

CONCLUSIONS

The GLP-1 RA EXE prevented PRED-induced glucose intolerance and islet-cell dysfunction in healthy humans. Incretin-based therapies should be explored as a potential strategy to prevent steroid diabetes.

Beta-cell dysfunction and insulin resistance after subarachnoid haemorrhage

BACKGROUND

Hyperglycaemia is a common finding and an independent risk factor for increased morbidity and mortality in aneurysmal subarachnoid haemorrhage (SAH). Although in these patients hyperglycaemia is commonly ascribed to insulin resistance, there is little understanding of underlying mechanisms.

AIMS

To prospectively study temporal disturbances of glucose metabolism after aneurysmal SAH in patients without known abnormalities of glucose metabolism and to explore possible correlations with markers of stress.

METHODS

In consecutive aneurysmal SAH patients not subjected to insulin therapy, in-hospital and follow-up oral glucose tolerance tests (OGTTs) and assessments of insulin resistance, pancreatic β-cell function, free fatty acids (FFA) and cortisol were performed and compared with reference values.

RESULTS

We included 13 patients. In the first 2 weeks of admission, median fasting glucose and FFA levels were elevated while insulin levels were not. OGTTs were indicative of glucose intolerance in all patients at days 3 and 7, while on follow-up 1 patient had glucose intolerance and all patients had normal fasting glucose levels. Pancreatic β-cell function was impaired throughout the first week and insulin resistance from day 4 to 10. Levels of cortisol correlated with higher fasting glucose and increased FFA. FFA in turn correlated with pancreatic β-cell dysfunction.

CONCLUSIONS

Aneurysmal SAH patients have transient abnormalities of glucose metabolism. During the first week, it appears to result predominantly from transient pancreatic β-cell dysfunction, in combination with insulin resistance.

Disturbance of glucose homeostasis after pediatric cardiac surgery

This study aimed to evaluate the time course of perioperative blood glucose levels of children undergoing cardiac surgery for congenital heart disease in relation to endogenous stress hormones, inflammatory mediators, and exogenous factors such as caloric intake and glucocorticoid use. The study prospectively included 49 children undergoing cardiac surgery. Blood glucose levels, hormonal alterations, and inflammatory responses were investigated before and at the end of surgery, then 12 and 24 h afterward. In general, blood glucose levels were highest at the end of surgery. Hyperglycemia, defined as a glucose level higher than 8.3 mmol/l (>150 mg/dl) was present in 52% of the children at the end of surgery. Spontaneous normalization of blood glucose occurred in 94% of the children within 24 h. During surgery, glucocorticoids were administered to 65% of the children, and this was the main factor associated with hyperglycemia at the end of surgery (determined by univariate analysis of variance). Hyperglycemia disappeared spontaneously without insulin therapy after 12-24 h for the majority of the children. Postoperative morbidity was low in the study group, so the presumed positive effects of glucocorticoids seemed to outweigh the adverse effects of iatrogenic hyperglycemia.

Glucocorticoids differentially regulate the expression of CRFR1 and CRFR2α in MIN6 insulinoma cells and rodent islets

Urocortin 3 (Ucn 3), member of the corticotropin-releasing factor (CRF) family of peptide hormones, is released from β-cells to potentiate insulin secretion. Ucn 3 activates the CRF type-2 receptor (CRFR2) but does not activate the type-1 receptor (CRFR1), which was recently demonstrated on β-cells. While the direct actions of Ucn 3 on insulin secretion suggest the presence of cognate receptors within the islet microenvironment, this has not been established. Here we demonstrate that CRFR2α is expressed by MIN6 insulinoma cells and by primary mouse and human islets, with no detectable expression of CRFR2β. Furthermore, stimulation of MIN6 cells or primary mouse islets in vitro or in vivo with glucocorticoids (GCs) robustly and dose-dependently increases the expression of CRFR2α, while simultaneously inhibiting the expression of CRFR1 and incretin receptors. Luciferase reporters driven by the mouse CRFR1 or CRFR2α promoter in MIN6 cells confirm these differential effects of GCs. In contrast, GCs inhibit CRFR2α promoter activity in HEK293 cells and inhibit the expression of CRFR2β in A7r5 rat aortic smooth muscle cells and differentiated C2C12 myotubes. These findings suggest that the GC-mediated increase of CRFR2α depends on the cellular context of the islet and deviates from the GC-mediated suppression of CRFR1 and incretin receptors. Furthermore, GC-induced increases in CRFR2α expression coincide with increased Ucn 3-dependent activation of cAMP and MAPK pathways. We postulate that differential effect of GCs on the expression of CRFR1 and CRFR2α in the endocrine pancreas represent a mechanism to shift sensitivity from CRFR1 to CRFR2 ligands.

Emodin, a natural product, selectively inhibits 11beta-hydroxysteroid dehydrogenase type 1 and ameliorates metabolic disorder in diet-induced obese mice

BACKGROUND AND PURPOSE

11beta-Hydroxysteroid dehydrogenase type 1 (11beta-HSD1) is an attractive therapeutic target of type 2 diabetes and metabolic syndrome. Emodin, a natural product and active ingredient of various Chinese herbs, has been demonstrated to possess multiple biological activities. Here, we investigated the effects of emodin on 11beta-HSD1 and its ability to ameliorate metabolic disorders in diet-induced obese (DIO) mice.

EXPERIMENTAL APPROACH

Scintillation proximity assay was performed to evaluate inhibition of emodin against recombinant human and mouse 11beta-HSDs. The ability of emodin to inhibit prednisone- or dexamethasone-induced insulin resistance was investigated in C57BL/6J mice and its effect on metabolic abnormalities was observed in DIO mice.

KEY RESULTS

Emodin is a potent and selective 11beta-HSD1 inhibitor with the IC(50) of 186 and 86 nM for human and mouse 11beta-HSD1, respectively. Single oral administration of emodin inhibited 11beta-HSD1 activity of liver and fat significantly in mice. Emodin reversed prednisone-induced insulin resistance in mice, whereas it did not affect dexamethasone-induced insulin resistance, which confirmed its inhibitory effect on 11beta-HSD1 in vivo. In DIO mice, oral administration of emodin improved insulin sensitivity and lipid metabolism, and lowered blood glucose and hepatic PEPCK, and glucose-6-phosphatase mRNA.

CONCLUSIONS AND IMPLICATIONS

This study demonstrated a new role for emodin as a potent and selective inhibitor of 11beta-HSD1 and its beneficial effects on metabolic disorders in DIO mice. This highlights the potential value of analogues of emodin as a new class of compounds for the treatment of metabolic syndrome or type 2 diabetes.

Emodin, a natural product, selectively inhibits 11beta-hydroxysteroid dehydrogenase type 1 and ameliorates metabolic disorder in diet-induced obese mice

BACKGROUND AND PURPOSE

11beta-Hydroxysteroid dehydrogenase type 1 (11beta-HSD1) is an attractive therapeutic target of type 2 diabetes and metabolic syndrome. Emodin, a natural product and active ingredient of various Chinese herbs, has been demonstrated to possess multiple biological activities. Here, we investigated the effects of emodin on 11beta-HSD1 and its ability to ameliorate metabolic disorders in diet-induced obese (DIO) mice.

EXPERIMENTAL APPROACH

Scintillation proximity assay was performed to evaluate inhibition of emodin against recombinant human and mouse 11beta-HSDs. The ability of emodin to inhibit prednisone- or dexamethasone-induced insulin resistance was investigated in C57BL/6J mice and its effect on metabolic abnormalities was observed in DIO mice.

KEY RESULTS

Emodin is a potent and selective 11beta-HSD1 inhibitor with the IC(50) of 186 and 86 nM for human and mouse 11beta-HSD1, respectively. Single oral administration of emodin inhibited 11beta-HSD1 activity of liver and fat significantly in mice. Emodin reversed prednisone-induced insulin resistance in mice, whereas it did not affect dexamethasone-induced insulin resistance, which confirmed its inhibitory effect on 11beta-HSD1 in vivo. In DIO mice, oral administration of emodin improved insulin sensitivity and lipid metabolism, and lowered blood glucose and hepatic PEPCK, and glucose-6-phosphatase mRNA.

CONCLUSIONS AND IMPLICATIONS

This study demonstrated a new role for emodin as a potent and selective inhibitor of 11beta-HSD1 and its beneficial effects on metabolic disorders in DIO mice. This highlights the potential value of analogues of emodin as a new class of compounds for the treatment of metabolic syndrome or type 2 diabetes.

Subthreshold α₂-adrenergic activation counteracts glucagon-like peptide-1 potentiation of glucose-stimulated insulin secretion

The pancreatic β cell harbors α₂-adrenergic and glucagon-like peptide-1 (GLP-1) receptors on its plasma membrane to sense the corresponding ligands adrenaline/noradrenaline and GLP-1 to govern glucose-stimulated insulin secretion. However, it is not known whether these two signaling systems interact to gain the adequate and timely control of insulin release in response to glucose. The present work shows that the α₂-adrenergic agonist clonidine concentration-dependently depresses glucose-stimulated insulin secretion from INS-1 cells. On the contrary, GLP-1 concentration-dependently potentiates insulin secretory response to glucose. Importantly, the present work reveals that subthreshold α₂-adrenergic activation with clonidine counteracts GLP-1 potentiation of glucose-induced insulin secretion. This counteractory process relies on pertussis toxin- (PTX-) sensitive Gi proteins since it no longer occurs following PTX-mediated inactivation of Gi proteins. The counteraction of GLP-1 potentiation of glucose-stimulated insulin secretion by subthreshold α₂-adrenergic activation is likely to serve as a molecular mechanism for the delicate regulation of insulin release.

Glut4 is upregulated despite decreased insulin signaling during prolonged fasting in northern elephant seal pups

Postprandial cellular glucose uptake is dependent on an insulin-signaling cascade in muscle and adipose tissue, resulting in the translocation of the insulin-dependent glucose transporter 4 (Glut4) into the plasma membrane. Additionally, extended food deprivation is characterized by suppressed insulin signaling and decreased Glut4 expression. Northern elephant seals are adapted to prolonged fasts characterized by high levels of plasma glucose. To address the hypothesis that the fasting-induced decrease in insulin is associated with reduced insulin signaling in prolonged fasted seals, we compared the adipose protein levels of the cellular insulin-signaling pathway, Glut4 and plasma glucose, insulin, cortisol, and adiponectin concentrations between Early (n = 9; 2-3 wks postweaning) and Late (n = 8; 6-8 wks postweaning) fasted seals. Plasma adiponectin (230 ± 13 vs. 177 ± 11 ng/ml), insulin (2.7 ± 0.4 vs. 1.0 ± 0.1 μU/ml), and glucose (9.8 ± 0.5 vs. 8.0 ± 0.3 mM) decreased, while cortisol (124 ± 6 vs. 257 ± 30 nM) doubled with fasting. Glut4 increased (31%) with fasting despite the significant decreases in the cellular content of phosphatidylinositol 3-kinase as well as phosphorylated insulin receptor, insulin receptor substrate-1, and Akt2. Increased Glut4 may have contributed to the decrease in plasma glucose, but the decrease in insulin and insulin signaling suggests that Glut4 is not insulin-dependent in adipose tissue during prolonged fasting in elephant seals. The reduction of plasma glucose independent of insulin may make these animals an ideal model for the study of insulin resistance.

Targeting the pre-receptor metabolism of cortisol as a novel therapy in obesity and diabetes

Due to its impact upon health and the economy, the mechanisms that contribute to the pathogenesis of obesity and the metabolic syndrome are under intense scrutiny. In addition to understanding the pathogenesis of disease it is important to design and trial novel therapies. Patients with cortisol excess, Cushing's syndrome, have a phenotype similar to that of the metabolic syndrome and as a result there is much interest the manipulation of glucocorticoid (GC) action as a therapeutic strategy. Intracellular GC levels are regulated by 11β-hydroxysteroid dehydrogenase (11β-HSD1) which converts inactive cortisone to cortisol, thereby increasing local GC action. There is an abundance of data implicating 11β-HSD1 in the pathogenesis of obesity, type 2 diabetes and the metabolic syndrome and 11β-HSD1 is an attractive therapeutic target. Selective 11β-HSD1 inhibitors, which do not act upon 11β-HSD2 (which inactivates cortisol to cortisone) are in development. So far studies have primarily been carried out in rodents, with results showing improvements in metabolic profile. Data are now beginning to emerge from human studies and the results are promising.

Role of glucocorticoids and the glucocorticoid receptor in metabolism: insights from genetic manipulations

Since the discovery of the beneficial effects of adrenocortical extracts for treating adrenal insufficiency more than 80 years ago, glucocorticoids and their cognate, intracellular receptor, the glucocorticoid receptor have been characterized as critical checkpoints in the delicate hormonal control of energy homeostasis in mammals. Whereas physiological levels of glucocorticoids are required for proper metabolic control, aberrant glucocorticoid action has been linked to a variety of pandemic metabolic diseases, such as type II diabetes and obesity. Based on its importance for human health, studies of the molecular mechanisms of within the glucocorticoid signaling axis have become a major focus in biomedical research. In particular, the understanding of tissue-specific functions of the glucocorticoid receptor pathway has been proven to be of substantial value for the development of novel therapies in the treatment of chronic metabolic disorders. Therefore, this review focuses on the consequences of endogenous and experimental modulation of glucocorticoid receptor expression for metabolic homeostasis and dysregulation, particularly emphasizing tissue-specific contributions of the glucocorticoid pathway to the control of energy metabolism.

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.

Chromosomal mapping of pancreatic islet morphological features and regulatory hormones in the spontaneously diabetic (Type 2) Goto-Kakizaki rat

Insulin resistance and altered endocrine pancreas function are central pathophysiological features of type 2 diabetes mellitus (T2DM). The Goto-Kakizaki (GK) rat is a model of spontaneous T2DM characterised by reduced beta cell mass and genetically determined glucose intolerance and altered insulin secretion. To identify genetic determinants of endocrine pancreas histopathology, we carried out quantitative trait locus (QTL) mapping of histological phenotypes (beta cell mass -BCM and insulin-positive cell area -IPCA) and plasma concentration of hormones and growth factors in a F2 cohort derived from GK and normoglycemic Brown Norway rats. Although IPCA and BCM in the duodenal region of the pancreas were highly positively correlated (P < 10⁻⁶), and similarly in the splenic region, both measures were poorly correlated when comparing duodenal and splenic phenotypes. Strongest evidence of linkage to pancreas morphological traits was obtained between BCM and chromosome 10 (LOD 3.2). Evidence of significant linkage (LOD 4.2) to plasma corticosterone was detected in a region of chromosome 1 distal to other QTLs previously identified in the GK. Male-specific genetic effects were detected, including linkages (LOD > 4) to growth hormome (GH) on chromosome 6 and prolactin on chromosome 17. These data suggest independent genetic control of the structure and function of ontologically different regions of the endocrine pancreas. Novel QTLs for corticosterone, prolactin and GH may contribute to diabetes in the GK. The QTLs that we have identified in this, and previous genetic studies collectively underline the complex and multiple mechanisms involved in diabetes in the GK strain.

Bench-to-bedside review: Glucose and stress conditions in the intensive care unit

The physiological response to blood glucose elevation is the pancreatic release of insulin, which blocks hepatic glucose production and release, and stimulates glucose uptake and storage in insulin-dependent tissues. When this first regulatory level is overwhelmed (that is, by exogenous glucose supplementation), persistent hyperglycaemia occurs with intricate consequences related to the glucose acting as a metabolic substrate and as an intracellular mediator. It is thus very important to unravel the glucose metabolic pathways that come into play during stress as well as the consequences of these on cellular functions. During acute injuries, activation of serial hormonal and humoral responses inducing hyperglycaemia is called the 'stress response'. Central activation of the nervous system and of the neuroendocrine axes is involved, releasing hormones that in most cases act to worsen the hyperglycaemia. These hormones in turn induce profound modifications of the inflammatory response, such as cytokine and mediator profiles. The hallmarks of stress-induced hyperglycaemia include 'insulin resistance' associated with an increase in hepatic glucose output and insufficient release of insulin with regard to glycaemia. Although both acute and chronic hyperglycaemia may induce deleterious effects on cells and organs, the initial acute endogenous hyperglycaemia appears to be adaptive. This acute hyperglycaemia participates in the maintenance of an adequate inflammatory response and consequently should not be treated aggressively. Hyperglycaemia induced by an exogenous glucose supply may, in turn, amplify the inflammatory response such that it becomes a disproportionate response. Since chronic exposure to glucose metabolites, as encountered in diabetes, induces adverse effects, the proper roles of these metabolites during acute conditions need further elucidation.

Small-Molecule Suppressors of Cytokine-Induced beta-Cell Apoptosis

Pancreatic beta-cell apoptosis is a critical event during the development of type-1 diabetes. The identification of small molecules capable of preventing cytokine-induced apoptosis could lead to avenues for therapeutic intervention. We developed a set of phenotypic cell-based assays designed to identify such small-molecule suppressors. Rat INS-1E cells were simultaneously treated with a cocktail of inflammatory cytokines and a collection of 2,240 diverse small molecules and screened using an assay for cellular ATP levels. Forty-nine top-scoring compounds included glucocorticoids, several pyrazole derivatives, and known inhibitors of glycogen synthase kinase-3beta. Two compounds were able to increase cellular ATP levels, reduce caspase-3 activity and nitrite production, and increase glucose-stimulated insulin secretion in the presence of cytokines. These results indicate that small molecules identified by this screening approach may protect beta cells from autoimmune attack and may be good candidates for therapeutic intervention in early stages of type-1 diabetes.

Increased glucocorticoid receptor expression and activity mediate the LPS resistance of SPRET/EI mice

SPRET/Ei mice are extremely resistant to acute LPS-induced lethal inflammation when compared with C57BL/6. We found that in vivo SPRET/Ei mice exhibit strongly reduced expression levels of cytokines and chemokines. To investigate the role of the potent anti-inflammatory glucocorticoid receptor (GR) in the SPRET/Ei phenotype, mice were treated with the GR antagonist RU486 or bilateral adrenalectomy. Under such conditions, both C57BL/6 and SPRET/Ei mice were strongly sensitized to LPS, and the differences in LPS response between SPRET/Ei and C57BL/6 mice were completely gone. These results underscore the central role of GR in the LPS hyporesponsiveness of SPRET/Ei mice. Compared with C57BL/6, SPRET/Ei mice were found to express higher GR levels, which were reflected in increased GR transactivation. Using a backcross mapping strategy, we demonstrate that the high GR transcription levels are linked to the Nr3c1 (GR) locus on chromosome 18 itself. Unexpectedly, SPRET/Ei mice exhibit a basal overactivation of the hypothalamic-pituitary-adrenal axis, namely strongly increased corticosterone levels, ACTH levels, and adrenocortical size. As a consequence of the excess of circulating glucocorticoids (GCs), levels of hepatic gluconeogenic enzymes are increased, and insulin secretion from pancreatic β-cells is impaired, both of which result in hyperglycemia and glucose intolerance in SPRET/Ei mice. We conclude that SPRET/Ei mice are unique as they display an unusual combination of elevated GR expression and increased endogenous GC levels. Hence, these mice provide a new and powerful tool for the study of GR- and GC-mediated mechanisms, including immune repressive functions, neuroendocrine regulation, insulin secretion, and carbohydrate metabolism.

Type 2 diabetes mellitus and the cardiometabolic syndrome: impact of incretin-based therapies

The rates of type 2 diabetes mellitus, obesity, and cardiovascular disease (CVD) continue to increase at epidemic proportions. It has become clear that these disease states are not independent but are frequently interrelated. By addressing conditions such as obesity, insulin resistance, stress hyperglycemia, impaired glucose tolerance, and diabetes mellitus, with its micro- and macrovascular complications, a specific treatment strategy can be developed. These conditions can be addressed by early identification of patients at high risk for type 2 diabetes, prompt and aggressive treatment of their hyperglycemia, recognition of the pleiotropic and synergistic benefits of certain antidiabetes agents on CVD, and thus, avoiding potential complications including hypoglycemia and weight gain. Incretin-based therapies, which include glucagon-like peptide-1 (GLP-1) receptor agonists and dipeptidyl peptidase-IV (DPP-IV) inhibitors, have the potential to alter the course of type 2 diabetes and associated CVD complications. Advantages of these therapies include glucose-dependent enhancement of insulin secretion, infrequent instances of hypoglycemia, weight loss with GLP-1 receptor agonists, weight maintenance with DPP-IV inhibitors, decreased blood pressure, improvements in dyslipidemia, and potential beneficial effects on CV function.

Regulation of islet beta-cell pyruvate metabolism: interactions of prolactin, glucose, and dexamethasone

Prolactin (PRL) induces beta-cell proliferation and glucose-stimulated insulin secretion (GSIS) and counteracts the effects of glucocorticoids on insulin production. The mechanisms by which PRL up-regulates GSIS are unknown. We used rat islets and insulinoma (INS-1) cells to explore the interactions of PRL, glucose, and dexamethasone (DEX) in the regulation of beta-cell pyruvate carboxylase (PC), pyruvate dehydrogenase (PDH), and the pyruvate dehydrogenase kinases (PDKs), which catalyze the phosphorylation and inactivation of PDH. PRL increased GSIS by 37% (P < 0.001) in rat islets. Glucose at supraphysiological concentrations (11 mm) increased PC mRNA in islets; in contrast, PRL suppressed PC mRNA levels in islets and INS-1 cells, whereas DEX was without effect. Neither PRL nor DEX altered PC protein or activity levels. In INS-1 cells, PRL increased PDH activity 1.4- to 2-fold (P < 0.05-0.001) at glucose concentrations ranging from 2.5-11 mm. DEX reduced PDH activity; this effect was reversed by PRL. PDK1, -2, -3, and -4 mRNAs were detected in both islets and insulinoma cells, but the latter expressed trivial amounts of PDK4. PRL reduced PDK2 mRNA and protein levels in rat islets and INS-1 cells and PDK4 mRNA in islets; DEX increased PDK2 mRNA in islets and INS-1 cells; this effect was reversed by PRL. Our findings suggest that PRL induction of GSIS is mediated by increases in beta-cell PDH activity; this is facilitated by suppression of PDKs. PRL counteracts the effects of DEX on PDH and PDK expression, suggesting novel roles for the lactogens in the defense against diabetes.

Reduced glucose tolerance and insulin resistance induced by steroid treatment, relative physical inactivity, and high-calorie diet impairs the incretin effect in healthy subjects

AIMS/HYPOTHESIS

The loss of incretin effect in patients with type 2 diabetes mellitus may be secondary to impaired glucose homeostasis. We investigated whether reduced glucose tolerance and insulin resistance induced by steroid treatment, relative physical inactivity, and high-calorie diet in healthy young males would impair the incretin effect.

METHODS

The incretin effect was measured using 75 g oral glucose tolerance test (OGTT) and isoglycemic iv glucose infusion (IIGI) in 10 healthy Caucasian normal glucose-tolerant male subjects without any family history of diabetes [age 24 + or - 3 yr (mean + or - sd); body mass index 23 + or - 2 kg/m(2); glycosylated hemoglobin 5.4 + or - 0.1%] before and at the end of a 12-d period with oral administration of prednisolone (37.5 mg once daily), high-calorie diet, and relative physical inactivity.

RESULTS

The 12-d intervention period resulted in significant increases in body weight [79 + or - 5 vs. 80 + or - 6 kg (mean + or - sd), P = 0.03] and fasting plasma glucose (5.1 + or - 0.1 vs. 5.6 + or - 0.2 mm, P = 0.016), whereas insulin sensitivity (Matsuda index 17.6 + or - 1.7 vs. 9.2 + or - 1.0, P = 0.0001) decreased. Glucose tolerance [as assessed by the 120-min plasma glucose value after OGTT (4.9 + or - 1.1 vs. 7.8 + or - 2.5 mm, P < 0.0001) and area under curve (AUC) (152 + or - 45 vs. 384 + or - 53 mm.4 h, P = 0.002)] during the OGTT deteriorated. Also, the incretin effect [incretin effect (percent) = 100% x (AUC(insulin,OGTT) - AUC(insulin,IIGI))/AUC(insulin,OGTT))] deteriorated (72 + or - 5 vs. 43 + or - 7%, P = 0.002). An increase in glucose-dependent insulinotropic polypeptide response during OGTT, but no significant changes in glucagon-like peptide-1 or glucagon responses, was observed after glucose homeostatic dysregulation.

CONCLUSIONS/INTERPRETATION

Impairment of the incretin effect can be elicited by a short period of reduced glucose tolerance and insulin resistance in healthy male subjects not disposed for type 2 diabetes.

Interactions between age, stress and insulin on cognition: implications for Alzheimer's disease

There is much interest in understanding the mechanisms responsible for interactions among stress, aging, memory and Alzheimer's disease. Glucocorticoid secretion associated with early life stress may contribute to the variability of the aging process and to the development of neuro- and psychopathologies. Maternal separation (MS), a model of early life stress in which rats experience 3 h of daily separation from the dam during the first 3 weeks of life, was used to study the interactions between stress and aging. Young (3 months) MS rats showed an altered hypothalamic-pituitary-adrenal (HPA) axis reactivity, depressive-like behavior in the Porsolt swimming test and cognitive impairments in the Morris water maze and new object recognition test that persisted in aged (18 months) rats. Levels of insulin receptor, phosphorylated insulin receptor and markers of downstream signaling pathways (pAkt, pGSK3 beta, pTau, and pERK1 levels) were significantly decreased in aged rats. There was a significant decrease in pERK2 and in the plasticity marker ARC in MS aged rats compared with single MS or aged rats. It is interesting to note that there was a significant increase in the C99 : C83 ratio, A beta levels, and BACE1 levels the hippocampus of MS aged rats, suggesting that in aged rats subjected to early life stress, there was an increase in the amyloidogenic processing of amyloid precursor protein (APP). These results are integrated in a tentative mechanism through which aging interplay with stress to influence cognition as the basis of Alzheimer disease (AD). The present results may provide the proof-of-concept for the use of glucocorticoid-/insulin-related drugs in the treatment of AD.

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.

How to manage perioperative endocrine insufficiency

Patients with endocrinopathies frequently present to the operating room. Although many of these disorders are managed on a chronic basis, patients may have acute changes in the perioperative period that, if left unrecognized, can have a negative effect on perioperative morbidity and mortality. It is imperative that anesthesiologists understand the implications of the surgical stress response on hormonal flux. This article focuses on the 4 most commonly encountered endocrinopathies: diabetes mellitus, hyperthyroidism, hypothyroidism, and adrenal insufficiency. Specific challenges pertaining to patients with pheochromocytoma are also discussed.

Glucocorticoids in vivo induce both insulin hypersecretion and enhanced glucose sensitivity of stimulus-secretion coupling in isolated rat islets

Although glucocorticoids are widely used as antiinflammatory agents in clinical therapies, they may cause serious side effects that include insulin resistance and hyperinsulinemia. To study the potential functional adaptations of the islet of Langerhans to in vivo glucocorticoid treatment, adult Wistar rats received dexamethasone (DEX) for 5 consecutive days, whereas controls (CTL) received only saline. The analysis of insulin release in freshly isolated islets showed an enhanced secretion in response to glucose in DEX-treated rats. The study of Ca(2+) signals by fluorescence microscopy also demonstrated a higher response to glucose in islets from DEX-treated animals. However, no differences in Ca(2+) signals were found between both groups with tolbutamide or KCl, indicating that the alterations were probably related to metabolism. Thus, mitochondrial function was explored by monitoring oxidation of nicotinamide dinucleotide phosphate autofluorescence and mitochondrial membrane potential. Both parameters revealed a higher response to glucose in islets from DEX-treated rats. The mRNA and protein content of glucose transporter-2, glucokinase, and pyruvate kinase was similar in both groups, indicating that changes in these proteins were probably not involved in the increased mitochondrial function. Additionally, we explored the status of Ca(2+)-dependent signaling kinases. Unlike calmodulin kinase II, we found an augmented phosphorylation level of protein kinase C alpha as well as an increased response of the phospholipase C/inositol 1,4,5-triphosphate pathway in DEX-treated rats. Finally, an increased number of docked secretory granules were observed in the beta-cells of DEX animals using transmission electron microscopy. Thus, these results demonstrate that islets from glucocorticoid-treated rats develop several adaptations that lead to an enhanced stimulus-secretion coupling and secretory capacity.

Surgery in the patient with endocrine dysfunction

Patients with preoperative endocrinopathies represent a particular challenge not only to anesthesiologists but also to surgeons and perioperative clinicians. The "endocrine axis" is complex and has multiple feedback loops, some of which are endocrine and paracrine related, and others that are strongly influenced by the surgical stress response. Familiarity with several of the common endocrinopathies facilitates management in the perioperative period. This article focuses on 4 of the most common endocrinopathies: diabetes mellitus, hyperthyroidism, hypothyroidism, and adrenal insufficiency. Perioperative challenges in patients presenting with pheochromocytoma are also discussed.