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

Glucocorticoid Metabolism in Obesity and Following Weight Loss

Glucocorticoids are steroid hormones produced by the adrenal cortex and are essential for the maintenance of various metabolic and homeostatic functions. Their function is regulated at the tissue level by 11β-hydroxysteroid dehydrogenases and they signal through the glucocorticoid receptor, a ligand-dependent transcription factor. Clinical observations have linked excess glucocorticoid levels with profound metabolic disturbances of intermediate metabolism resulting in abdominal obesity, insulin resistance and dyslipidaemia. In this review, we discuss the physiological mechanisms of glucocorticoid secretion, regulation and function, and survey the metabolic consequences of excess glucocorticoid action resulting from elevated release and activation or up-regulated signaling. Finally, we summarize the reported impact of weight loss by diet, exercise, or bariatric surgery on circulating and tissue-specific glucocorticoid levels and examine the therapeutic possibility of reversing glucocorticoid-associated metabolic disorders.

Chronic Stress and Diabetes Mellitus: Interwoven Pathologies

Stress threatens the homeostasis and mobilizes a plethora of adaptive physiological and behavioral changes via the hypothalamic-pituitary-adrenal (HPA) axis and the sympathetic nervous system. The HPA axis influences the pituitary gland, hypothalamus and adrenal gland via a complex set of positive and negative feedback system. The feedback system operates in a well regulated neuroendocrine manner to reestablish the threatened body equilibrium. The HPA axis secreted major product is a glucocorticoid (cortisol) which is kept within a physiologically optimal range and serves to accomplish the various physiological functions crucial for survival. In chronically stressed individuals dishabituation of HPA axis is followed by increased release of glucocorticoids and catecholamines. Higher secretion of glucocorticoids influences glucose metabolism by promoting gluconeogenesis in the liver, suppressing glucose uptake (adipocytes and skeletal muscles), promoting lipolysis in adipocytes, suppressing insulin secretion, inflicting insulin resistance and inflammation. These biological changes alter neuroendocrine mechanisms and lead to maladaptive congregation of events that form the underlying cause of development of Type 2 diabetes (T2D). The currently reviewed evidences advocate that targeting stress mediated hypersecretion of glucocorticoids may be a viable approach for the treatment of T2D and to reinstate glucose homeostasis.

Glucose stimulates somatostatin secretion in pancreatic δ-cells by cAMP-dependent intracellular Ca2+ release

Somatostatin secretion from pancreatic islet δ-cells is stimulated by elevated glucose levels, but the underlying mechanisms have only partially been elucidated. Here we show that glucose-induced somatostatin secretion (GISS) involves both membrane potential-dependent and -independent pathways. Although glucose-induced electrical activity triggers somatostatin release, the sugar also stimulates GISS via a cAMP-dependent stimulation of CICR and exocytosis of somatostatin. The latter effect is more quantitatively important and in mouse islets depolarized by 70 mM extracellular K+ , increasing glucose from 1 mM to 20 mM produced an ∼3.5-fold stimulation of somatostatin secretion, an effect that was mimicked by the application of the adenylyl cyclase activator forskolin. Inhibiting cAMP-dependent pathways with PKI or ESI-05, which inhibit PKA and exchange protein directly activated by cAMP 2 (Epac2), respectively, reduced glucose/forskolin-induced somatostatin secretion. Ryanodine produced a similar effect that was not additive to that of the PKA or Epac2 inhibitors. Intracellular application of cAMP produced a concentration-dependent stimulation of somatostatin exocytosis and elevation of cytoplasmic Ca2+ ([Ca2+]i). Both effects were inhibited by ESI-05 and thapsigargin (an inhibitor of SERCA). By contrast, inhibition of PKA suppressed δ-cell exocytosis without affecting [Ca2+]i Simultaneous recordings of electrical activity and [Ca2+]i in δ-cells expressing the genetically encoded Ca2+ indicator GCaMP3 revealed that the majority of glucose-induced [Ca2+]i spikes did not correlate with δ-cell electrical activity but instead reflected Ca2+ release from the ER. These spontaneous [Ca2+]i spikes are resistant to PKI but sensitive to ESI-05 or thapsigargin. We propose that cAMP links an increase in plasma glucose to stimulation of somatostatin secretion by promoting CICR, thus evoking exocytosis of somatostatin-containing secretory vesicles in the δ-cell.

Predictive factors for the development of diabetes in cancer patients treated with phosphatidylinositol 3-kinase inhibitors

PURPOSE

Targeted therapy using phosphatidylinositol 3-kinase (PI3K) inhibitors is used to treat cancer such as lymphoma. In animal studies, its use raised concern about alteration of glucose metabolism. To date, clinical data are inconclusive; therefore, we investigated the incidence and clinical manifestations of diabetes in cancer patients treated with PI3K inhibitors.

METHODS

In a retrospective review of diabetes-free patients with advanced solid tumors treated with PI3K inhibitor, we performed Cox regression to identify independent predictors for the development of diabetes.

RESULTS

Of 38 patients (mean age: 54.5 years, 23.7% female) having a mean duration of follow-up of 238.5 days who initiated PI3K inhibitors, 55.3% developed diabetes during treatment (mean 29.1 days); among these, 28.6% experienced remission of diabetes after discontinuing PI3K inhibitors (mean 72.1 days). Patients with incident diabetes had higher anti-hypertensive medication use, higher HbA1c levels and fasting glucose at baseline, and longer duration of PI3K inhibitor use (P = 0.024, P = 0.005, P = 0.008, and P = 0.023, respectively). Previous steroid use and lower baseline HbA1c level were significantly associated with development of diabetes (HR = 8.41, 95% CI 1.89-37.33; HR = 2.16, 95% CI 1.09-4.25, respectively). Patients whose diabetes remitted after discontinuing PI3K inhibitors were younger (P = 0.035) and had lower fasting glucose levels during PI3K inhibitor treatment (P = 0.001) compared to those non-remitters.

CONCLUSIONS

Previous steroid use and lower baseline HbA1c level may be important predictors for developing diabetes in patients with advanced solid tumors treated with PI3K inhibitors, warranting close observation and careful intervention.

Associations among tourist camp management, high and low tourist seasons, and welfare factors in female Asian elephants in Thailand

This study investigated how camp management and tourist activities affect body condition, adrenocortical function, lipid profiles and metabolic status in female tourist elephants. We compared twice monthly serum insulin, glucose, fructosamine, total cholesterol (TC), triglyceride (TG), low density lipoprotein (LDL), high density lipoprotein (HDL), and fecal glucocorticoid metabolite (FGM) concentrations to body condition scores (BCS) at five camps with different management styles (e.g., tourist activities, work type, diet) between the High (November–February) and Low (March–October) tourist seasons. There were significant camp effects on health parameters, with BCS, TC, HDL, insulin and glucose being among the highest, and G:I being the lowest (less heathy) in elephants at an observation camp compared to those at camps where elephants received exercise by providing rides to tourists. Differences between High and Low tourist season months also were found for all measures, except TG and FGM concentrations. Both work time and walking distance were negatively correlated to glucose, fructosamine and insulin, while walking distance was negatively related to FGM concentrations. By contrast, positive associations were found between tourist number and BCS, TG, and insulin, perhaps related to tourists feeding elephants. Quantity of supplementary diet items (e.g., bananas, sugar cane, pumpkin) were positively correlated with FGM concentrations, glucose, fructosamine, and insulin. This study provides evidence that body condition, adrenal activity, metabolic markers, and lipid profiles in captive elephants may be affected by visitor numbers, work activities, and the amount of supplementary foods offered by tourists. Some activities appear to have negative (e.g., feeding), while others (e.g., exercise) may have positive effects on health and welfare. We conclude that camps adopting a more hands-off approach to tourism need to ensure elephants remain healthy by providing environments that encourage activity and rely on more natural diets or foraging.

Making sense of gut feelings in the traumatic brain injury pathogenesis

Traumatic brain injury (TBI) is a devastating condition which often initiates a sequel of neurological disorders that can last throughout lifespan. From metabolic perspective, TBI also compromises systemic physiology including the function of body organs with subsequent malfunctions in metabolism. The emerging panorama is that the effects of TBI on the periphery strike back on the brain and exacerbate the overall TBI pathogenesis. An increasing number of clinical reports are alarming to show that metabolic dysfunction is associated with incidence of long-term neurological and psychiatric disorders. The autonomic nervous system, associated hypothalamic-pituitary axis, and the immune system are at the center of the interface between brain and body and are central to the regulation of overall homeostasis and disease. We review the strong association between mechanisms that regulate cell metabolism and inflammation which has important clinical implications for the communication between body and brain. We also discuss the integrative actions of lifestyle interventions such as diet and exercise on promoting brain and body health and cognition after TBI.

Prenatal Betamethasone interferes with immune system development and alters target cells in autoimmune diabetes

Non-genetic factors are crucial in the pathogenesis of type 1 diabetes (T1D), a disease caused by autoimmunity against insulin-producing β-cells. Exposure to medications in the prenatal period may influence the immune system maturation, thus altering self-tolerance. Prenatal administration of betamethasone –a synthetic glucocorticoid given to women at risk of preterm delivery– may affect the development of T1D. It has been previously demonstrated that prenatal betamethasone administration protects offspring from T1D development in nonobese diabetic (NOD) mice. The direct effect of betamethasone on the immature and mature immune system of NOD mice and on target β-cells is analysed in this paper. In vitro, betamethasone decreased lymphocyte viability and induced maturation-resistant dendritic cells, which in turn impaired γδ T cell proliferation and decreased IL-17 production. Prenatal betamethasone exposure caused thymus hypotrophy in newborn mice as well as alterations in immune cells subsets. Furthermore, betamethasone decreased β-cell growth, reduced C-peptide secretion and altered the expression of genes related to autoimmunity, metabolism and islet mass in T1D target tissue. These results support the protection against T1D in the betamethasone-treated offspring and demonstrate that this drug alters the developing immune system and β-cells. Understanding how betamethasone generates self-tolerance could have potential clinical relevance in T1D.

Adaptive β-Cell Neogenesis in the Adult Mouse in Response to Glucocorticoid-Induced Insulin Resistance

Both type 1 and type 2 diabetes are characterized by deficient insulin secretion and decreased β-cell mass. Thus, regenerative strategies to increase β-cell mass need to be developed. To characterize mechanisms of β-cell plasticity, we studied a model of severe insulin resistance in the adult mouse and defined how β-cells adapt. Chronic corticosterone (CORT) treatment was given to adult mice and led to rapid insulin resistance and adaptive increased insulin secretion. Adaptive and massive increase of β-cell mass was observed during treatment up to 8 weeks. β-Cell mass increase was partially reversible upon treatment cessation and reinduced upon subsequent treatment. β-Cell neogenesis was suggested by an increased number of islets, mainly close to ducts, and increased Sox9 and Ngn3 mRNA levels in islets, but lineage-tracing experiments revealed that neoformed β-cells did not derive from Sox9- or Ngn3-expressing cells. CORT treatment after β-cell depletion partially restored β-cells. Finally, β-cell neogenesis was shown to be indirectly stimulated by CORT because serum from CORT-treated mice increased β-cell differentiation in in vitro cultures of pancreatic buds. Altogether, the results present a novel model of β-cell neogenesis in the adult mouse and identify the presence of neogenic factors in the serum of CORT-treated mice.

Body condition and adrenal glucocorticoid activity affects metabolic marker and lipid profiles in captive female elephants in Thailand

Studies in western zoo elephants have found relationships between body condition and physiological function, and identified mitigating management strategies to optimize health and welfare. A similar methodological approach was used in this study, which evaluated a body condition score (BCS; 1 = thinnest, 5 = fattest) every other month and fecal glucocorticoid metabolite (FGM) concentrations twice monthly in 33 tourist camp elephants in Thailand for a 1-year period to assess seasonal variations, and determine how lipid profiles [total cholesterol (TC), low density lipoproteins (LDL), high density lipoproteins (HDL), triglycerides (TG)] and metabolic parameters [insulin, glucose, fructosamine, glucose to insulin ratio (G:I)] related to measures of body condition and adrenal function. The most prevalent BCS was 3-3.5 (60.6%), with 27.3% at BCS = 4 (overweight) and 12.1% at BCS = 4.5-5 (very overweight); no elephants had a BCS <2. BCSs were higher in rainy and winter seasons compared to summer, with FGM, TG, HDL, LDL, and insulin also higher in the rainy and/or winter seasons (p<0.05). By contrast, TC and glucose were lowest in the rainy season. FGM measures were negatively associated with two environmental factors: temperature and rainfall, but not humidity. Positive correlations were found between BCS and TC, LDL, and HDL, and between FGM and TC, HDL, glucose, and insulin (p<0.05), whereas BCS and FGM were both negatively associated with the G:I (p<0.05). However, there was no relationship between BCS and FGM among the camp elephants. Using BCS and FGM measures as outcome variables in separate regression models, this study found high BCS and elevated FGM concentrations were associated with altered lipid profiles and metabolic status in elephants. Furthermore, more work hours/day was associated with better body condition and health measures. Thus, being overweight and exposed to factors that increase adrenal activity could adversely affect health status, requiring alterations in management for some individuals, whereas exercise appears to have a protective effect.

Evidence for a Coupled Oscillator Model of Endocrine Ultradian Rhythms

Whereas long-period temporal structures in endocrine dynamics have been well studied, endocrine rhythms on the scale of hours are relatively unexplored. The study of these ultradian rhythms (URs) has remained nascent, in part, because a theoretical framework unifying ultradian patterns across systems has not been established. The present overview proposes a conceptual coupled oscillator network model of URs in which oscillating hormonal outputs, or nodes, are connected by edges representing the strength of node-node coupling. We propose that variable-strength coupling exists both within and across classic hormonal axes. Because coupled oscillators synchronize, such a model implies that changes across hormonal systems could be inferred by surveying accessible nodes in the network. This implication would at once simplify the study of URs and open new avenues of exploration into conditions affecting coupling. In support of this proposed framework, we review mammalian evidence for (1) URs of the gut-brain axis and the hypothalamo-pituitary-thyroid, -adrenal, and -gonadal axes, (2) UR coupling within and across these axes; and (3) the relation of these URs to body temperature. URs across these systems exhibit behavior broadly consistent with a coupled oscillator network, maintaining both consistent URs and coupling within and across axes. This model may aid the exploration of mammalian physiology at high temporal resolution and improve the understanding of endocrine system dynamics within individuals.

Steroid-induced hyperglycemia: An underdiagnosed problem or clinical inertia? A narrative review

Corticosteroids are widely diffused drugs. An important side effect is the impairment of glycemic control both in patients with known diabetes and in normoglycemic ones potentially leading to steroid-induced diabetes mellitus (SIDM). In this review based on papers released on PubMed, MEDLINE, and EMBASE from January 2015 to October 2017, we summarized and discussed main updates about the definition, the diagnosis, and the pathophysiology of steroid-induced hyperglycemia (SIH), with a look to new therapies. Main alterations responsible for the diabetogenic effect of corticosteroids are a negative impact on insulin sensitivity along with a derangement on insulin secretion, explaining the typical post-prandial hyperglycemia linked to the promotion of gluconeogenesis. An early and precise diagnosis of SIH and/or SIDM is necessary, but current criteria do not seem sensible enough. As an afterthought, the treatment should be reasoned and tailored according to proposed glycemic thresholds and patient comorbidities, choosing between antidiabetic oral drugs and insulin, the latter being preferable among hospitalized patients. SIDM and SIH are frequent problems, but often underdiagnosed due to old diagnostic criteria. Dedicated guidelines universally shared are mandatory in order to harmonize the treatment of these conditions, thus overtaking single therapeutic strategies mostly arising from literature.

Glucocorticoids Reprogram β-Cell Signaling to Preserve Insulin Secretion

Excessive glucocorticoid exposure has been shown to be deleterious for pancreatic β-cell function and insulin release. However, glucocorticoids at physiological levels are essential for many homeostatic processes, including glycemic control. We show that corticosterone and cortisol and their less active precursors 11-dehydrocorticosterone (11-DHC) and cortisone suppress voltage-dependent Ca²⁺ channel function and Ca²⁺ fluxes in rodent as well as in human β-cells. However, insulin secretion, maximal ATP/ADP responses to glucose, and β-cell identity were all unaffected. Further examination revealed the upregulation of parallel amplifying cAMP signals and an increase in the number of membrane-docked insulin secretory granules. Effects of 11-DHC could be prevented by lipotoxicity and were associated with paracrine regulation of glucocorticoid activity because global deletion of 11β-hydroxysteroid dehydrogenase type 1 normalized Ca²⁺ and cAMP responses. Thus, we have identified an enzymatically amplified feedback loop whereby glucocorticoids boost cAMP to maintain insulin secretion in the face of perturbed ionic signals. Failure of this protective mechanism may contribute to diabetes in states of glucocorticoid excess, such as Cushing syndrome, which are associated with frank dyslipidemia.

The Effects of Mitiglinide and Repaglinide on Postprandial Hyperglycemia in Patients Undergoing Methylprednisolone Pulse Therapy

One adverse effect of methylprednisolone (MP) pulse therapy is an acute dose-dependent increase in the blood glucose level. Five patients with thyroid ophthalmopathy but normal glucose tolerance received MP pulse therapy (3 cycles, 3 days/week) and were assessed by continuous glucose monitoring. Steroid therapy increased the mean sensor glucose level, and all patients developed steroid-induced diabetes. The patients were treated alternately with mitiglinide (30 mg/day) and repaglinide (1.5 mg/day) during the second or third MP pulse therapy. The sensor glucose levels before lunch and dinner were more favorable during treatment with repaglinide than during treatment with mitiglinide. Repaglinide may be more clinically appropriate than mitiglinide.

Glucocorticoid receptor activation selectively influence performance of Wistar rats in Y-maze

Glucocorticoid receptors (GR) are ubiquitously expressed in metazoans. Different and contrasting phenotypes have been reported upon their activation. This study investigated the behavioral phenotypes characteristic of GR stimulation in male Wistar rats. Rats in each of the four groups of rats received one of the following treatments: distilled water (control) or one of three doses of dexamethasone (treatment) injected intraperitoneally for 7 days. The Rats were afterwards subjected to the Y maze, the elevated plus maze (EPM), the Morris water maze (MWM), and the novel object recognition (NOR) test. At the end of the study, the animals were anesthetized and neural activity from the prefrontal cortex recorded. Blood was collected via cardiac puncture to evaluate the levels of plasma insulin and glucose, and the prefrontal cortexes excised to determine the levels of insulin, markers of oxidative stress, and calcium in the homogenate. This study showed that treatment with dexamethasone significantly reduced the total and percentage alternation in the Y maze, but had no significant effect on object recognition in the NOR test, long-term and short-term spatial memory in the MWM, or anxiety-like behavior in the EPM. Plasma and brain insulin and calcium levels were elevated moderately following treatment with the lowest dose of dexamethasone. All doses of dexamethasone decreased brain superoxide dismutase and increased lactate dehydrogenase levels. No significant change in neural activity was observed. This study shows that activation of glucocorticoid receptors differentially affects different behavioral paradigms and provides evidence for a role for glucocorticoids in mediating insulin function in the brain.

Dominance of the hypothalamus-pituitary-adrenal axis over the renin-angiotensin-aldosterone system is a risk factor for decreased insulin secretion

How the association between the hypothalamus-pituitary-adrenal (HPA) axis and the renin-angiotensin-aldosterone system (RAAS) affects glucose metabolism were not well examined in a general population. Participants of the population-based 2015 Iwaki study were enrolled (n: 1,016; age: 54.4 ± 15.1 years). Principal component (PC) analysis identified two PCs: PC1 represented levels of the HPA axis (serum cortisol) and the RAAS (plasma aldosterone) as a whole, and PC2 represented the HPA axis relative to the RAAS (HPA axis dominance). We examined the association between these PCs and glucose metabolism using homeostasis model assessment indices of reduced insulin sensitivity (HOMA-R) and secretion (HOMA-β). Univariate linear regression analyses showed a correlation between PC2 and HOMA-β (β = −0.248, p < 0.0001), but not between PC1 and HOMA-β (β = −0.004, p = 0.9048). The correration between PC2 and HOMA-β persisted after adjustment for multiple factors (β = −0.101, p = 0.0003). No correlations were found between the PCs and HOMA-R. When subjects were tertiled based on PC2, the highest tertile was at greater risk of decreased insulin secretion (defined as the lower one third of HOMA-β (≤68.9)) than the lowest tertile after adjustment for multiple factors (odds ratio, 2.00; 95% confidence interval, 1.35–2.97). The HPA axis dominance is associated with decreased insulin secretion in a Japanese population.

Shared Dysregulation of Homeostatic Brain-Body Pathways in Depression and Type 2 Diabetes

PURPOSE OF REVIEW

The purpose of this review is to provide an overview of shared dysregulation of the hypothalamic-pituitary-adrenal (HPA) and brain-gut-microbiome (BGM) axes associated with depression and type 2 diabetes (T2D). Clinical implications and future research are also discussed.

RECENT FINDINGS

Both depression and T2D are associated with dysregulation of the HPA and BGM axes. These pathways regulate immune function, glucose metabolism, and sleep, which are altered in both illnesses. Dysregulation of homeostatic brain-body pathways may be positively influenced through different therapeutic actions, including psychotherapy, healthy eating, physical activity, sleep promotion, and certain anti-inflammatory or antidepressant medications. While the causal nature of the relationship between depression and T2D remains unclear, these conditions share dysregulation of homeostatic brain-body pathways that are central to mental and physical health. Better understanding of this dysregulation may provide opportunities for interventions that could benefit both conditions. Future research should examine the additive burden of depression and T2D on HPA and BGM dysregulation and better differentiate depression from emotional distress.

Can agent-based simulation be used as a tool to support polypharmacy prescribing practice?

Objective

We sought to develop a simulation modelling method to help better understand the complex interplay of factors that lead to people with type 2 diabetes and asthma not taking all of their medication as prescribed when faced with multiple medications (polypharmacy).

Research design and methods

In collaboration with polypharmacy patients, general practitioners, pharmacists and polypharmacy researchers, we developed a map of factors that directly and indirectly affect somebody’s decision to take their medication as prescribed when faced with multiple type 2 diabetes and asthma medications. We then translated these behavioural influences into logical rules using data from the literature and developed a proof-of-concept agent-based simulation model that captures the medicine-taking behaviours of those with type 2 diabetes and asthma taking multiple medications and which predicts both the clinical effectiveness and rates of adherence for different combinations of medications.

Conclusions

The model we have developed could be used as a prescription support tool or a way of estimating medicine-taking behaviour in cost-effectiveness analyses.

Maternal and Early-Life Circadian Disruption Have Long-Lasting Negative Consequences on Offspring Development and Adult Behavior in Mice

Modern life involves chronic circadian disruption through artificial light and these disruptions are associated with numerous mental and physical health maladies. Because the developing nervous system is particularly vulnerable to perturbation, we hypothesized that early-life circadian disruption would negatively impact offspring development and adult function. Pregnant mice were subjected to chronic circadian disruption from the time of uterine implantation through weaning. To dissociate in utero from postnatal effects, a subset of litters was cross-fostered at birth from disrupted dams to control dams and vice versa. Postnatal circadian disruption was associated with reduced adult body mass, social avoidance, and hyperactivity. In utero disruption resulted in more pronounced social avoidance and hyperactivity, phenotypes not abrogated by cross-fostering to control mothers. To examine whether circadian disruption affects development by acting as an early life stressor, we examined birthweight, litter size, maternal cannibalism, and epigenetic modifications. None of these variables differed between control and disrupted dams, or resembled patterns seen following early-life stress. Our findings indicate that developmental chronic circadian disruption permanently affects somatic and behavioral development in a stage-of-life-dependent manner, independent of early life stress mechanisms, underscoring the importance of temporal structure during development, both in utero and early postnatal life.

Molecular mechanisms redirecting the GLP-1 receptor signalling profile in pancreatic β-cells during type 2 diabetes

Treatments with β-cell preserving properties are essential for the management of type 2 diabetes (T2D), and the new therapeutic avenues, developed over the last years, rely on the physiological role of glucagon-like peptide-1 (GLP-1). Sustained pharmacological levels of GLP-1 are achieved by subcutaneous administration of GLP-1 analogues, while transient and lower physiological levels of GLP-1 are attained following treatment with inhibitors of dipeptidylpeptidase 4 (DPP4), an endoprotease which degrades the peptide. Both therapeutic classes display a sustained and durable hypoglycaemic action in patients with T2D. However, the GLP-1 incretin effect is known to be reduced in patients with T2D, and GLP-1 analogues and DPP4 inhibitors were shown to lose their effectiveness over time in some patients. The pathological mechanisms behind these observations can be either a decrease in GLP-1 secretion from intestinal L-cells and, as a consequence, a reduction in GLP-1 plasma concentrations, combined or not with a reduced action of GLP-1 in the β-cell, the so-called GLP-1 resistance. Much evidence for a GLP-1 resistance of the β-cell in subjects with T2D have emerged. Here, we review the potential roles of the genetic background, the hyperglycaemia, the hyperlipidaemia, the prostaglandin E receptor 3, the nuclear glucocorticoid receptor, the GLP-1R desensitization and internalisation processes, and the β-arrestin-1 expression levels on GLP-1 resistance in β-cells during T2D.

Sex differences in variability across timescales in BALB/c mice

BACKGROUND

Females are markedly underinvestigated in the biological and behavioral sciences due to the presumption that cyclic hormonal changes across the ovulatory cycle introduce excess variability to measures of interest in comparison to males. However, recent analyses indicate that male and female mice and rats exhibit comparable variability across numerous physiological and behavioral measures, even when the stage of the estrous cycle is not considered. Hormonal changes across the ovulatory cycle likely contribute cyclic, intra-individual variability in females, but the source(s) of male variability has, to our knowledge, not been investigated. It is unclear whether male variability, like that of females, is temporally structured and, therefore, quantifiable and predictable. Finally, whether males and females exhibit variability on similar time scales has not been explored.

METHODS

These questions were addressed by collecting chronic, high temporal resolution locomotor activity (LA) and core body temperature (CBT) data from male and female BALB/c mice.

RESULTS

Contrary to expectation, males are more variable than females over the course of the day (diel variability) and exhibit higher intra-individual daily range than females in both LA and CBT. Between mice of a given sex, variability is comparable for LA but the inter-individual daily range in CBT is greater for males. To identify potential rhythmic processes contributing to these sex differences, we employed wavelet transformations across a range of periodicities (1-39 h).

CONCLUSIONS

Although variability in circadian power is comparable between the sexes for both LA and CBT, infradian variability is greater in females and ultradian variability is greater in males. Thus, exclusion of female mice from studies because of estrous cycle variability may increase variance in investigations where only male measures are collected over a span of several hours and limit generalization of findings from males to females.

Lactoferrin ameliorates corticosterone-related acute stress and hyperglycemia in rats

We aimed to assess the effects of lactoferrin (Lf) on glycemic regulatory responses under restraint stress (RS) in rats. Bovine Lf (bLf, 100 mg/kg) was intraperitoneally administered to rats before oral saline administration or oral glucose tolerance test (OGTT) following 60 min of RS load. In the case of oral saline administration, RS significantly raised plasma glucose, but bLf did not affect the level. Plasma glucose in OGTT showed an overall lower transition in the bLf group, and the levels at 30 and 180 min or the area under the curve (AUC) were significantly decreased. Although bLf suppressed an increase in plasma corticosterone during RS, the levels of plasma insulin, epinephrine and glucagon were not changed by the bLf treatment.

Association between Higher Serum Cortisol Levels and Decreased Insulin Secretion in a General Population

Glucocorticoids (GCs) are well known to induce insulin resistance. However, the effect of GCs on insulin secretion has not been well characterized under physiological conditions in human. We here evaluated the effect of GCs on insulin secretion/ß-cell function precisely in a physiological condition. A population-based study of 1,071 Japanese individuals enrolled in the 2014 Iwaki study (390 men, 681 women; aged 54.1 ± 15.1 years), those excluded individuals taking medication for diabetes or steroid treatment, were enrolled in the present study. Association between serum cortisol levels and insulin resistance/secretion assessed by homeostasis model assessment using fasting blood glucose and insulin levels (HOMA-R and HOMA-ß, respectively) were examined. Univariate linear regression analyses showed correlation of serum cortisol levels with HOMA-ß (ß = -0.134, p <0.001) but not with HOMA-R (ß = 0.042, p = 0.172). Adjustments for age, gender, and the multiple clinical characteristics correlated with HOMA indices showed similar results (HOMA-ß: ß = -0.062, p = 0.025; HOMA-R: ß = -0.023, p = 0.394). The correlation between serum cortisol levels and HOMA-ß remained significant after adjustment for HOMA- R (ß = -0.057, p = 0.034). When subjects were tertiled based on serum cortisol levels, the highest tertile was at greater risk of decreased insulin secretion (defined as lower one third of HOMA-ß (≤70)) than the lowest tertile, after adjustment for multiple factors including HOMA- R (odds ratio 1.26, 95% confidence interval 1.03–1.54). In conclusion, higher serum cortisol levels are significantly associated with decreased insulin secretion in the physiological cortisol range in a Japanese population.

Glucose enhances rat islet function via stimulating CART expression

Cocaine- and amphetamine-regulated transcript (CART) is an anorexigenic peptide widely expressed in the central and peripheral nervous systems, as well as in endocrine cells. CART is markedly upregulated in the β-cells of several rodent models of type-2 diabetes. The stimulatory effect of exogenous CART peptide on insulin secretion is cAMP dependent. Glucose is the most important regulator of islet function. However, the role of CART in glucose-potentiated insulin secretion remains unclear. Here, our results showed that glucose time- and dose-dependently elicited CART mRNA expression in rat islets. Both the glucokinase agonist GKA50 and the long-acting GLP-1 analogue exendin-4 increased CART mRNA expression. The protein kinase A (PKA) inhibitor H89 and the inactivation of cAMP response element-binding protein (CREB) suppressed forskolin-stimulated CART mRNA expression. Furthermore, CART overexpression amplified insulin secretion from rat islets in response to glucose and forskolin, and ameliorated dexamethasone-impaired insulin secretion. These findings suggest that islet-derived CART is involved, at least in part, in high glucose-potentiated pancreatic β-cell function.

Adaptive response of rat pancreatic β-cells to insulin resistance induced by monocrotophos: Biochemical evidence

Our previous findings clearly suggested the role of duration of exposure to monocrotophos (MCP) in the development of insulin resistance. Rats exposed chronically to MCP developed insulin resistance with hyperinsulinemia without overt diabetes. In continuation of this vital observation, we sought to delineate the biochemical mechanisms that mediate heightened pancreatic β-cell response in the wake of MCP-induced insulin resistance in rats. Adult rats were orally administered (0.9 and 1.8mg/kgb.w/d) MCP for 180days. Terminally, MCP-treated rats exhibited glucose intolerance, hyperinsulinemia, and potentiation of glucose-induced insulin secretion along with elevated levels of circulating IGF1, free fatty acids, corticosterone, and paraoxonase activity. Biochemical analysis of islet extracts revealed increased levels of insulin, malate, pyruvate and ATP with a concomitant increase in activities of cytosolic and mitochondrial enzymes that are known to facilitate insulin secretion and enhanced shuttle activities. Interestingly, islets from MCP-treated rats exhibited increased insulin secretory potential ex vivo compared to those isolated from control rats. Further, MCP-induced islet hypertrophy was associated with increased insulin-positive cells. Our study demonstrates the impact of the biological interaction between MCP and components of metabolic homeostasis on pancreatic beta cell function/s. We speculate that the heightened pancreatic beta cell function evidenced may be mediated by increased IGF1 and paraoxonase activity, which effectively counters insulin resistance induced by chronic exposure to MCP. Our findings emphasize the need for focused research to understand the confounding environmental risk factors which may modulate heightened beta cell functions in the case of organophosphorus insecticide-induced insulin resistance. Such an approach may help us to explain the sharp increase in the prevalence of type II diabetes worldwide.

G6PC2 Modulates the Effects of Dexamethasone on Fasting Blood Glucose and Glucose Tolerance

The glucose-6-phosphatase catalytic subunit 2 (G6PC2) gene encodes an islet-specific glucose-6-phosphatase catalytic subunit. G6PC2 forms a substrate cycle with glucokinase that determines the glucose sensitivity of insulin secretion. Consequently, deletion of G6pc2 lowers fasting blood glucose (FBG) without affecting fasting plasma insulin. Although chronic elevation of FBG is detrimental to health, glucocorticoids induce G6PC2 expression, suggesting that G6PC2 evolved to transiently modulate FBG under conditions of glucocorticoid-related stress. We show, using competition and mutagenesis experiments, that the synthetic glucocorticoid dexamethasone (Dex) induces G6PC2 promoter activity through a mechanism involving displacement of the islet-enriched transcription factor MafA by the glucocorticoid receptor. The induction of G6PC2 promoter activity by Dex is modulated by a single nucleotide polymorphism, previously linked to altered FBG in humans, that affects FOXA2 binding. A 5-day repeated injection paradigm was used to examine the chronic effect of Dex on FBG and glucose tolerance in wild-type (WT) and G6pc2 knockout mice. Acute Dex treatment only induces G6pc2 expression in 129SvEv but not C57BL/6J mice, but this chronic treatment induced G6pc2 expression in both. In 6-hour fasted C57BL/6J WT mice, Dex treatment lowered FBG and improved glucose tolerance, with G6pc2 deletion exacerbating the decrease in FBG and enhancing the improvement in glucose tolerance. In contrast, in 24-hour fasted C57BL/6J WT mice, Dex treatment raised FBG but still improved glucose tolerance, with G6pc2 deletion limiting the increase in FBG and enhancing the improvement in glucose tolerance. These observations demonstrate that G6pc2 modulates the complex effects of Dex on both FBG and glucose tolerance.

Impact of Glucocorticoid Excess on Glucose Tolerance: Clinical and Preclinical Evidence

Glucocorticoids (GCs) are steroid hormones that exert important physiological actions on metabolism. Given that GCs also exert potent immunosuppressive and anti-inflammatory actions, synthetic GCs such as prednisolone and dexamethasone were developed for the treatment of autoimmune- and inflammatory-related diseases. The synthetic GCs are undoubtedly efficient in terms of their therapeutic effects, but are accompanied by significant adverse effects on metabolism, specifically glucose metabolism. Glucose intolerance and reductions in insulin sensitivity are among the major concerns related to GC metabolic side effects, which may ultimately progress to type 2 diabetes mellitus. A number of pre-clinical and clinical studies have aimed to understand the repercussions of GCs on glucose metabolism and the possible mechanisms of GC action. This review intends to summarize the main alterations that occur in liver, skeletal muscle, adipose tissue, and pancreatic islets in the context of GC-induced glucose intolerance. For this, both experimental (animals) and clinical studies were selected and, whenever possible, the main cellular mechanisms involved in such GC-side effects were discussed.

Stressing diabetes? The hidden links between insulinotropic peptides and the HPA axis

Diabetes mellitus exerts metabolic stress on cells and it provokes a chronic increase in the long-term activity of the hypothalamus-pituitary-adrenocortical (HPA) axis, perhaps thereby contributing to insulin resistance. GLP-1 receptor (GLP-1R) agonists are pleiotropic hormones that not only affect glycaemic and metabolic control, but they also produce many other effects including activation of the HPA axis. In fact, several of the most relevant effects of GLP-1 might involve, at least in part, the modulation of the HPA axis. Thus, the anorectic activity of GLP-1 could be mediated by increasing CRF at the hypothalamic level, while its lipolytic effects could imply a local increase in glucocorticoids and glucocorticoid receptor (GC-R) expression in adipose tissue. Indeed, the potent activation of the HPA axis by GLP-1R agonists occurs within the range of therapeutic doses and with a short latency. Interestingly, the interactions of GLP-1 with the HPA axis may underlie most of the effects of GLP-1 on food intake control, glycaemic metabolism, adipose tissue biology and the responses to stress. Moreover, such activity has been observed in animal models (mice and rats), as well as in normal humans and in type I or type II diabetic patients. Accordingly, better understanding of how GLP-1R agonists modulate the activity of the HPA axis in diabetic subjects, especially obese individuals, will be crucial to design new and more efficient therapies for these patients.

Association between Glucose Metabolism and Sleep-disordered Breathing during REM Sleep

RATIONALE

Sleep-disordered breathing (SDB) has been associated with impaired glucose metabolism. It is possible that the association between SDB and glucose metabolism is distinct for non-REM versus REM sleep because of differences in sleep-state-dependent sympathetic activation and/or degree of hypoxemia.

OBJECTIVES

To characterize the association between REM-related SDB, glucose intolerance, and insulin resistance in a community-based sample.

METHODS

A cross-sectional analysis that included 3,310 participants from the Sleep Heart Health Study was undertaken (53% female; mean age, 66.1 yr). Full montage home-polysomnography and fasting glucose were available on all participants. SDB severity during REM and non-REM sleep was quantified using the apnea-hypopnea index in REM (AHIREM) and non-REM sleep (AHINREM), respectively. Fasting and 2-hour post-challenge glucose levels were assessed during a glucose tolerance test (n = 2,264). The homeostatic model assessment index for insulin resistance (HOMA-IR) was calculated (n = 1,543). Linear regression was used to assess the associations of AHIREM and AHINREM with fasting and post-prandial glucose levels and HOMA-IR.

MEASUREMENTS AND MAIN RESULTS

AHIREM and AHINREM were associated with fasting glycemia, post-prandial glucose levels, and HOMA-IR in models that adjusted for age, sex, race, and site. However, with additional adjustment for body mass index, waist circumference, and sleep duration, AHIREM was only associated with HOMA-IR (β = 0.04; 95% CI, 0.1-0.07; P = 0.01), whereas AHINREM was only associated with fasting (β = 0.93; 95% CI, 0.14-1.72; P = 0.02) and post-prandial glucose levels (β = 3.0; 95% CI, 0.5-5.5; P = 0.02).

CONCLUSIONS

AHIREM is associated with insulin resistance but not with fasting glycemia or glucose intolerance.

Exposure to early adversity: Points of cross-species translation that can lead to improved understanding of depression

The relationship between developmental exposure to adversity and affective disorders is reviewed. Adversity discussed herein includes physical and sexual abuse, neglect, or loss of a caregiver in humans. While these stressors can occur at any point during development, the unique temporal relationship to specific depressive symptoms was the focus of discussion. Further influences of stress exposure during sensitive periods can vary by gender and duration of abuse as well. Data from animal studies are presented to provide greater translational and causal understanding of how sensitive periods, different types of psychosocial stressors, and sex interact to produce depressive-like behaviors. Findings from maternal separation, isolation rearing, chronic variable stress, and peer-peer rearing paradigms clarify interpretation about how various depressive behaviors are influenced by age of exposure. Depressive behaviors are broken down into the following categories: mood and affect, anhedonia, energy, working memory, sleep-wake, appetite changes, suicide, and general malaise. Cross-species evidence from humans, nonhuman primates, rats, and mice within each of these categories is discussed. In conclusion, sensitive periods for affective-related behaviors (anxiety, mood, and controllability) occur earlier in life, while other aspects of depression are associated with adversity later during adolescence.

Hyper-Variability in Circulating Insulin, High Fat Feeding Outcomes, and Effects of Reducing Ins2 Dosage in Male Ins1-Null Mice in a Specific Pathogen-Free Facility

Insulin is an essential hormone with key roles in energy homeostasis and body composition. Mice and rats, unlike other mammals, have two insulin genes: the rodent-specific Ins1 gene and the ancestral Ins2 gene. The relationships between insulin gene dosage and obesity has previously been explored in male and female Ins2^-/- mice with full or reduced Ins1 dosage, as well as in female Ins1^-/- mice with full or partial Ins2 dosage. We report herein unexpected hyper-variability in Ins1-null male mice, with respect to their circulating insulin levels and to the physiological effects of modulating Ins2 gene dosage. Two large cohorts of Ins1^-/-:Ins2^+/- mice and their Ins1^-/-:Ins2^+/+ littermates were fed chow diet or high fat diet (HFD) from weaning, and housed in specific pathogen-free conditions. Cohort A and cohort B were studied one year apart. Contrary to female mice from the same litters, inactivating one Ins2 allele on the complete Ins1-null background did not consistently cause a reduction of circulating insulin in male mice, on either diet. In cohort A, all HFD-fed males showed an equivalent degree of insulin hypersecretion and weight gain, regardless of Ins2 dosage. In cohort B the effects of HFD appeared generally diminished, and cohort B Ins1^-/-:Ins2^+/- males showed decreased insulin levels and body mass compared to Ins1^-/-:Ins2^+/+ littermates, on both diets. Although experimental conditions were consistent between cohorts, we found that HFD-fed Ins1^-/-:Ins2^+/- mice with lower insulin levels had increased corticosterone. Collectively, these observations highlight the phenotypic characteristics that change in association with differences in circulating insulin and Ins2 gene dosage, particularly in male mice.

Effect of n-3 and n-6 Polyunsaturated Fatty Acids on Microsomal P450 Steroidogenic Enzyme Activities and In Vitro Cortisol Production in Adrenal Tissue From Yorkshire Boars

Dysregulation of adrenal glucocorticoid production is increasingly recognized to play a supportive role in the metabolic syndrome although the mechanism is ill defined. The adrenal cytochrome P450 (CYP) enzymes, CYP17 and CYP21, are essential for glucocorticoid synthesis. The omega-3 and omega-6 polyunsaturated fatty acids (PUFA) may ameliorate metabolic syndrome, but it is unknown whether they have direct actions on adrenal CYP steroidogenic enzymes. The aim of this study was to determine whether PUFA modify adrenal glucocorticoid synthesis using isolated porcine microsomes. The enzyme activities of CYP17, CYP21, 11β-hydroxysteroid dehydrogenase type 1, hexose-6-phosphate dehydrogenase (H6PDH), and CYP2E1 were measured in intact microsomes treated with fatty acids of disparate saturated bonds. Cortisol production was measured in a cell-free in vitro model. Microsomal lipid composition after arachidonic acid (AA) exposure was determined by sequential window acquisition of all theoretical spectra-mass spectrometry. Results showed that adrenal microsomal CYP21 activity was decreased by docosapentaenoic acid (DPA), docosahexaenoic acid (DHA), eicosapentaenoic acid, α-linolenic acid, AA, and linoleic acid, and CYP17 activity was inhibited by DPA, DHA, eicosapentaenoic acid, and AA. Inhibition was associated with the number of the PUFA double bonds. Similarly, cortisol production in vitro was decreased by DPA, DHA, and AA. Endoplasmic enzymes with intraluminal activity were unaffected by PUFA. In microsomes exposed to AA, the level of AA or oxidative metabolites of AA in the membrane was not altered. In conclusion, these observations suggest that omega-3 and omega-6 PUFA, especially those with 2 or more double bonds (DPA, DHA, and AA), impede adrenal glucocorticoid production.

Glucocorticoids Inhibit Basal and Hormone-Induced Serotonin Synthesis in Pancreatic Beta Cells

Diabetes is a major complication of chronic Glucocorticoids (GCs) treatment. GCs induce insulin resistance and also inhibit insulin secretion from pancreatic beta cells. Yet, a full understanding of this negative regulation remains to be deciphered. In the present study, we investigated whether GCs could inhibit serotonin synthesis in beta cell since this neurotransmitter has been shown to be involved in the regulation of insulin secretion. To this aim, serotonin synthesis was evaluated in vitro after treatment with GCs of either islets from CD1 mice or MIN6 cells, a beta-cell line. We also explored the effect of GCs on the stimulation of serotonin synthesis by several hormones such as prolactin and GLP 1. We finally studied this regulation in islet in two in vivo models: mice treated with GCs and with liraglutide, a GLP1 analog, and mice deleted for the glucocorticoid receptor in the pancreas. We showed in isolated islets and MIN6 cells that GCs decreased expression and activity of the two key enzymes of serotonin synthesis, Tryptophan Hydroxylase 1 (Tph1) and 2 (Tph2), leading to reduced serotonin contents. GCs also blocked the induction of serotonin synthesis by prolactin or by a previously unknown serotonin activator, the GLP-1 analog exendin-4. In vivo, activation of the Glucagon-like-Peptide-1 receptor with liraglutide during 4 weeks increased islet serotonin contents and GCs treatment prevented this increase. Finally, islets from mice deleted for the GR in the pancreas displayed an increased expression of Tph1 and Tph2 and a strong increased serotonin content per islet. In conclusion, our results demonstrate an original inhibition of serotonin synthesis by GCs, both in basal condition and after stimulation by prolactin or activators of the GLP-1 receptor. This regulation may contribute to the deleterious effects of GCs on beta cells.

Treatment with Tacrolimus and Sirolimus Reveals No Additional Adverse Effects on Human Islets In Vitro Compared to Each Drug Alone but They Are Reduced by Adding Glucocorticoids

Tacrolimus and sirolimus are important immunosuppressive drugs used in human islet transplantation; however, they are linked to detrimental effects on islets and reduction of long-term graft function. Few studies investigate the direct effects of these drugs combined in parallel with single drug exposure. Human islets were treated with or without tacrolimus (30 μg/L), sirolimus (30 μg/L), or a combination thereof for 24 hrs. Islet function as well as apoptosis was assessed by glucose-stimulated insulin secretion (GSIS) and Cell Death ELISA. Proinflammatory cytokines were analysed by qRT-PCR and Bio-Plex. Islets exposed to the combination of sirolimus and tacrolimus were treated with or without methylprednisolone (1000 μg/L) and the expression of the proinflammatory cytokines was investigated. We found the following: (i) No additive reduction in function and viability in islets existed when tacrolimus and sirolimus were combined compared to the single drug. (ii) Increased expression of proinflammatory cytokines mRNA and protein levels in islets took place. (iii) Methylprednisolone significantly decreased the proinflammatory response in islets induced by the drug combination. Although human islets are prone to direct toxic effect of tacrolimus and sirolimus, we found no additive effects of the drug combination. Short-term exposure of glucocorticoids could effectively reduce the proinflammatory response in human islets induced by the combination of tacrolimus and sirolimus.

Glucocorticoids and Metabolic Control

In response to stress, the central nervous system initiates a signaling cascade, which leads to the production of glucocorticoids (GCs). GCs act through the glucocorticoid receptor (GR) to coordinate the appropriate cellular response with the primary goal of mobilizing the storage forms of carbon precursors to generate a continuous glucose supply for the brain. Although GCs are critical for maintaining energy homeostasis, excessive GC stimulation leads to a number of undesirable side effects, including hyperglycemia, insulin resistance, fatty liver, obesity, and muscle wasting leading to severe metabolic dysfunction. Summarized below are the diverse metabolic roles of glucocorticoids in energy homeostasis and dysregulation, focusing specifically on glucose, lipid, and protein metabolism.

Molecular pathophysiology of hepatic glucose production

Maintaining blood glucose concentration within a relatively narrow range through periods of fasting or excess nutrient availability is essential to the survival of the organism. This is achieved through an intricate balance between glucose uptake and endogenous glucose production to maintain constant glucose concentrations. The liver plays a major role in maintaining normal whole body glucose levels by regulating the processes of de novo glucose production (gluconeogenesis) and glycogen breakdown (glycogenolysis), thus controlling the levels of hepatic glucose release. Aberrant regulation of hepatic glucose production (HGP) can result in deleterious clinical outcomes, and excessive HGP is a major contributor to the hyperglycemia observed in Type 2 diabetes mellitus (T2DM). Indeed, adjusting glycemia as close as possible to a non-diabetic range is the foremost objective in the medical treatment of patients with T2DM and is currently achieved in the clinic primarily through suppression of HGP. Here, we review the molecular mechanisms controlling HGP in response to nutritional and hormonal signals and discuss how these signals are altered in T2DM.

Twenty-four-hour profiles of metabolic and stress hormones in sheep selected for a calm or nervous temperament

Even in the absence of stressors, temperament is associated with changes in the concentration of stress-responsive hormones and, possibly because of such changes, temperament can affect metabolism. We tested whether, in sheep bred for temperament for 14 generations, "nervous" females have greater concentrations of stress-responsive hormones in the absence of stressors than "calm" females, and whether these differences are associated with changes in the concentrations of metabolic hormones. In resting "calm" (n = 8) and "nervous" (n = 8) sheep, concentrations of cortisol, prolactin, leptin, and insulin were measured in blood plasma sampled via jugular catheter every 20 min for 24 h. The animals were individually penned, habituated to their housing and human handling over 7 wk, and fed before sampling began. Diurnal variation was evident for all hormones, but a 24-h cortisol pattern was detected in only 7 individuals. There was no effect of temperament on any aspect of concentrations of cortisol or prolactin, but "calm" animals had greater concentrations of insulin in the early afternoon than "nervous" animals (14.5 ± 1.1 vs 10.0 ± 1.6 μU/mL; P = 0.038), and a similar tendency was seen for leptin (P = 0.092). We conclude that selection for temperament affects the concentration of metabolic hormones in the absence of stressors, but this effect is independent of stress-responsive hormones.

Decreased 11β-Hydroxysteroid Dehydrogenase 1 Level and Activity in Murine Pancreatic Islets Caused by Insulin-Like Growth Factor I Overexpression

We have reported a high expression of IGF-I in pancreatic islet β-cells of transgenic mice under the metallothionein promoter. cDNA microarray analysis of the islets revealed that the expression of 82 genes was significantly altered compared to wild-type mice. Of these, 11β-hydroxysteroid dehydrogenase 1 (11β-HSD1), which is responsible for the conversion of inert cortisone (11-dehydrocorticosterone, DHC in rodents) to active cortisol (corticosterone) in the liver and adipose tissues, has not been identified previously as an IGF-I target in pancreatic islets. We characterized the changes in its protein level, enzyme activity and glucose-stimulated insulin secretion. In freshly isolated islets, the level of 11β-HSD1 protein was significantly lower in MT-IGF mice. Using dual-labeled immunofluorescence, 11β-HSD1 was observed exclusively in glucagon-producing, islet α-cells but at a lower level in transgenic vs. wild-type animals. MT-IGF islets also exhibited reduced enzymatic activities. Dexamethasone (DEX) and DHC inhibited glucose-stimulated insulin secretion from freshly isolated islets of wild-type mice. In the islets of MT-IGF mice, 48-h pre-incubation of DEX caused a significant decrease in insulin release, while the effect of DHC was largely blunted consistent with diminished 11β-HSD1 activity. In order to establish the function of intracrine glucocorticoids, we overexpressed 11β-HSD1 cDNA in MIN6 insulinoma cells, which together with DHC caused apoptosis and a significant decrease in proliferation. Both effects were abolished with the treatment of an 11β-HSD1 inhibitor. Our results demonstrate an inhibitory effect of IGF-I on 11β-HSD1 expression and activity within the pancreatic islets, which may mediate part of the IGF-I effects on cell proliferation, survival and insulin secretion.

The mechanisms by which antidepressants may reduce coronary heart disease risk

BACKGROUND

Depression is known to increase the risk for coronary heart disease (CHD) likely through various pathogenetic actions. Understanding the links between depression and CHD and the effects of mediating these links may prove beneficial in CHD prevention.

METHODS

An integrated model of CHD was used to elucidate pathogenetic pathways of importance between depression and CHD. Using biomarker relative risk data the pathogenetic effects are representable as measurable effects based on changes in biomarkers.

RESULTS

A 'connection graph' presents interactions by illustrating the relationship between depression and the biomarkers of CHD. The use of selective serotonin reuptake inhibitors (SSRIs) is postulated to have potential to decrease CHD risk. Comparing the 'connection graph' of SSRI's to that of depression elucidates the possible actions through which risk reduction may occur.

CONCLUSIONS

The CHD effects of depression appear to be driven by increased inflammation and altered metabolism. These effects might be mediated with the use of SSRI's.

New-Onset Diabetes Mellitus After Transplantation in a Cynomolgus Macaque (Macaca fasicularis)

A 5.5-y-old intact male cynomolgus macaque (Macaca fasicularis) presented with inappetence and weight loss 57 d after heterotopic heart and thymus transplantation while receiving an immunosuppressant regimen consisting of tacrolimus, mycophenolate mofetil, and methylprednisolone to prevent graft rejection. A serum chemistry panel, a glycated hemoglobin test, and urinalysis performed at presentation revealed elevated blood glucose and glycated hemoglobin (HbA1c) levels (727 mg/dL and 10.1%, respectively), glucosuria, and ketonuria. Diabetes mellitus was diagnosed, and insulin therapy was initiated immediately. The macaque was weaned off the immunosuppressive therapy as his clinical condition improved and stabilized. Approximately 74 d after discontinuation of the immunosuppressants, the blood glucose normalized, and the insulin therapy was stopped. The animal's blood glucose and HbA1c values have remained within normal limits since this time. We suspect that our macaque experienced new-onset diabetes mellitus after transplantation, a condition that is commonly observed in human transplant patients but not well described in NHP. To our knowledge, this report represents the first documented case of new-onset diabetes mellitus after transplantation in a cynomolgus macaque.

Thiobenzothiazole-modified Hydrocortisones Display Anti-inflammatory Activity with Reduced Impact on Islet β-Cell Function

Glucocorticoids signal through the glucocorticoid receptor (GR) and are administered clinically for a variety of situations, including inflammatory disorders, specific cancers, rheumatoid arthritis, and organ/tissue transplantation. However, glucocorticoid therapy is also associated with additional complications, including steroid-induced diabetes. We hypothesized that modification of the steroid backbone is one strategy to enhance the therapeutic potential of GR activation. Toward this goal, two commercially unavailable, thiobenzothiazole-containing derivatives of hydrocortisone (termed MS4 and MS6) were examined using 832/13 rat insulinoma cells as well as rodent and human islets. We found that MS4 had transrepression properties but lacked transactivation ability, whereas MS6 retained both transactivation and transrepression activities. In addition, MS4 and MS6 both displayed anti-inflammatory activity. Furthermore, MS4 displayed reduced impact on islet β-cell function in both rodent and human islets. Similar to dexamethasone, MS6 promoted adipocyte development in vitro, whereas MS4 did not. Moreover, neither MS4 nor MS6 activated the Pck1 (Pepck) gene in primary rat hepatocytes. We conclude that modification of the functional groups attached to the D-ring of the hydrocortisone steroid molecule produces compounds with altered structure-function GR agonist activity with decreased impact on insulin secretion and reduced adipogenic potential but with preservation of anti-inflammatory activity.

The obesity-associated transcription factor ETV5 modulates circulating glucocorticoids

The transcription factor E-twenty-six version 5 (ETV5) has been linked with obesity in genome-wide association studies. Moreover, ETV5-deficient mice (knockout; KO) have reduced body weight, lower fat mass, and are resistant to diet-induced obesity, directly linking ETV5 to the regulation of energy balance and metabolism. ETV5 is expressed in hypothalamic brain regions that regulate both metabolism and HPA axis activity, suggesting that ETV5 may also modulate HPA axis function. In order to test this possibility, plasma corticosterone levels were measured in ETV5 KO and wildtype (WT) mice before (pre-stress) and after (post-stress) a mild stressor (intraperitoneal injection). ETV5 deficiency increased both pre- and post-stress plasma corticosterone, suggesting that loss of ETV5 elevated glucocorticoid tone. Consistent with this idea, ETV5 KO mice have reduced thymus weight, suggestive of increased glucocorticoid-induced thymic involution. ETV5 deficiency also decreased the mRNA expression of glucocorticoid receptor (GR), mineralocorticoid receptor (MR), and vasopressin receptor 1A in the hypothalamus, without altering vasopressin, corticotropin-releasing hormone, or oxytocin mRNA expression. In order to test whether reduced MR and GR expression affected glucocorticoid negative feedback, a dexamethasone suppression test was performed. Dexamethasone reduced plasma corticosterone in both ETV5 KO and WT mice, suggesting that glucocorticoid negative feedback was unaltered by ETV5 deficiency. In summary, these data suggest that the obesity-associated transcription factor ETV5 normally acts to diminish circulating glucocorticoids. This might occur directly via ETV5 actions on HPA-regulatory brain circuitry, and/or indirectly via ETV5-induced alterations in metabolic factors that then influence the HPA axis.

THE RATIONALE FOR USE OF INCRETINS IN THE MANAGEMENT OF NEW ONSET DIABETES AFTER TRANSPLANTATION (NODAT)

OBJECTIVE

Owing to advances in transplant science, increasing numbers of patients are receiving solid organ transplantation. New onset diabetes after transplantation (NODAT) frequently develops in transplant patients and requires acute and often ongoing management of hyperglycemia. The metabolic derangements of NODAT are similar to those of classic type 2 diabetes, and treatment has typically followed diabetes standards of care. Best practices for NODAT management remain to be developed.

METHODS

The mechanistic suitability of incretins to treat NODAT pathogenesis has been hitherto underappreciated. This review details the specific mechanistic value of incretins in patients with immunosuppression-associated hyperglycemia.

RESULTS

Corticosteroids have long been known to exert their effects on glucose metabolism by decreasing glucose utilization and enhancing hepatic gluconeogenesis. Corticosteroids also significantly and directly reduce insulin secretion, as do calcineurin inhibitors (CNIs), another commonly used group of immunosuppressive drugs that cause hyperglycemia and NODAT. The ability of incretins to counteract immunosuppressant-induced disruptions in insulin secretion suggest that the insulinotropic, glucagonostatic, and glucose-lowering actions of incretins are well suited to treat immunosuppressant-induced hyperglycemia in NODAT. Additional benefits of incretins include decreased glucagon levels and improved insulin resistance. In the case of glucagon-like peptide-1 (GLP-1) receptor agonists, weight loss is another benefit, countering the weight gain that is a common consequence of both hyperglycemia and transplantation. These benefits make incretins very attractive and deserving of more investigation.

CONCLUSION

Among diabetes treatment options, incretin therapies uniquely counteract immunosuppressant drugs' interference with insulin secretion. We propose an incretin-based treatment paradigm for NODAT management.

Fasting plasma glucose levels predict steroid-induced abnormal glucose metabolism in patients with non-diabetic chronic kidney disease: a prospective cohort study

BACKGROUND/AIMS

Glucocorticoids-induced abnormal glucose metabolism (AGM) is a common medical problem in patients with non-diabetic chronic kidney disease (CKD). However, little information is available regarding the prediction of steroid-induced AGM in this patient population.

METHODS

In this prospective cohort study, we consecutively enrolled 303 non-diabetic CKD patients with fasting plasma glucose (FPG) levels <5.6 mmol/l and normal oral glucose tolerance test (OGTT). OGTT was performed every 3 months during glucocorticoid treatment to identify new-onset AGM, and patients were followed for 12 months post steroid withdrawal.

RESULTS

During 593 person-years, there were 107 incident cases of steroid-induced AGM (18/100 person-year), including 55 (51.4%) diabetes and 52 (48.6%) pre-diabetes. In a multivariate model, each millimole increase per liter in FPG enhanced the risk of AGM by 4.6-fold (hazard ratio 4.58, 95% confidence interval, 2.67-7.83). After adjusting other risk factors, a progressively increased risk of AGM or DM was observed in patients with FPG levels ≥4.8 mmol/l, as compared with those whose levels were ≤4.3 mmol/l (p for trend <0.001). Furthermore, a greater increase in FPG level (≥0.3 mmol/l) during the first 3 months of glucocorticoid treatment was associated with an increased risk for future diabetes. For predicting steroid-induced diabetes, the area under the receiver-operating characteristic curve was 0.90 for the combination of FPG and changes in FPG levels at month 3.

CONCLUSION

Higher-normal FPG and a greater increase in FPG levels during glucocorticoid treatment may help to identify non-diabetic CKD patients at increased risk of steroid-induced AGM or diabetes.