The ATP-binding cassette proteins ABCB1 and ABCC1 as modulators of glucocorticoid action.

Responses to hormones that act through nuclear receptors are controlled by modulating hormone concentrations not only in the circulation but also within target tissues. The role of enzymes that amplify or reduce local hormone concentrations is well established for glucocorticoid and other lipophilic hormones; moreover, transmembrane transporters have proven critical in determining tissue responses to thyroid hormones. However, there has been less consideration of the role of transmembrane transport for steroid hormones. ATP-binding cassette (ABC) proteins were first shown to influence the accumulation of glucocorticoids in cells almost three decades ago, but observations over the past 10 years suggest that differential transport propensities of both exogenous and endogenous glucocorticoids by ABCB1 and ABCC1 transporters provide a mechanism whereby different tissues are preferentially sensitive to different steroids. This Review summarizes this evidence and the new insights provided for the physiology and pharmacology of glucocorticoid action, including new approaches to glucocorticoid replacement.

Stromal Cells Covering Omental Fat-Associated Lymphoid Clusters Trigger Formation of Neutrophil Aggregates to Capture Peritoneal Contaminants.

The omentum is a visceral adipose tissue rich in fat-associated lymphoid clusters (FALCs) that collects peritoneal contaminants and provides a first layer of immunological defense within the abdomen. Here, we investigated the mechanisms that mediate the capture of peritoneal contaminants during peritonitis. Single-cell RNA sequencing and spatial analysis of omental stromal cells revealed that the surface of FALCs were covered by CXCL1+ mesothelial cells, which we termed FALC cover cells. Blockade of CXCL1 inhibited the recruitment and aggregation of neutrophils at FALCs during zymosan-induced peritonitis. Inhibition of protein arginine deiminase 4, an enzyme important for the release of neutrophil extracellular traps, abolished neutrophil aggregation and the capture of peritoneal contaminants by omental FALCs. Analysis of omental samples from patients with acute appendicitis confirmed neutrophil recruitment and bacterial capture at FALCs. Thus, specialized omental mesothelial cells coordinate the recruitment and aggregation of neutrophils to capture peritoneal contaminants.

Sex-specific regulation of stress-induced fetal glucocorticoid surge by the mouse placenta.

Antenatal stress increases the prevalence of diseases in later life, which shows a strong sex-specific effect. However, the underlying mechanisms remain unknown. Maternal glucocorticoids can be elevated by stress and are potential candidates to mediate the effects of stress on the offspring sex-specifically. A comprehensive evaluation of dynamic maternal and placental mechanisms modulating fetal glucocorticoid exposure upon maternal stress was long overdue. Here, we addressed this gap in knowledge by investigating sex-specific responses to midgestational stress in mice. We observed increased levels of maternal corticosterone, the main glucocorticoid in rodents, along with higher corticosteroid-binding globulin levels at midgestation in C57Bl/6 dams exposed to sound stress. This resulted in elevated corticosterone in female fetuses, whereas male offspring were unaffected. We identified that increased placental expression of the glucocorticoid-inactivating enzyme 11ß-hydroxysteroid dehydrogenase type 2 (11ß-HSD2; Hsd11b2 gene) and ATP-binding cassette transporters, which mediate glucocorticoid efflux toward maternal circulation, protect male offspring from maternal glucocorticoid surges. We generated mice with an Hsd11b2 placental-specific disruption (Hsd11b2PKO) and observed moderately elevated corticosterone levels in offspring, along with increased body weight. Subsequently, we assessed downstream glucocorticoid receptors and observed a sex-specific differential modulation of placental Tsc22d3 expression, which encodes the glucocorticoid-induced leucine zipper protein in response to stress. Taken together, our observations highlight the existence of unique and well-orchestrated mechanisms that control glucocorticoid transfer, exposure, and metabolism in the mouse placenta, pinpointing toward the existence of sex-specific fetal glucocorticoid exposure windows during gestation in mice.

Dysregulation of Cortisol Metabolism in Equine Pituitary Pars Intermedia Dysfunction.

Equine Cushing disease [pituitary pars intermedia dysfunction (PPID)] is a common condition of older horses, but its pathophysiology is complex and poorly understood. In contrast to pituitary-dependent hyperadrenocorticism in other species, PPID is characterized by elevated plasma ACTH but not elevated plasma cortisol. In this study, we address this paradox and the hypothesis that PPID is a syndrome of ACTH excess in which there is dysregulation of peripheral glucocorticoid metabolism and binding. In 14 horses with PPID compared with 15 healthy controls, we show that in plasma, cortisol levels and cortisol binding to corticosteroid binding globulin were not different; in urine, glucocorticoid and androgen metabolites were increased up to fourfold; in liver, 11ß-hydroxysteroid dehydrogenase type 1 (11ß-HSD1) expression was reduced; in perirenal adipose tissue, 11ß-HSD1 and carbonyl reductase 1 expression was increased; and tissue cortisol levels were not measurably different. The combination of normal plasma cortisol with markedly enhanced urinary cortisol metabolite excretion and dysregulated tissue-specific steroid-metabolizing enzymes suggests that cortisol clearance is increased in horses with PPID. We infer that the ACTH excess may be compensatory and pituitary pathology and autonomous secretion may be a secondary rather than primary pathology. It is possible that successful therapy in PPID may be targeted either at lowering ACTH or, paradoxically, at reducing cortisol clearance.

Heterotopic Triplet Pregnancy in Gonadotropin Stimulation Cycle: A Case Report.

Background: Heterotopic pregnancy is defined as the simultaneous presence of 2 or more pregnancies at different implantation sites, most commonly one intrauterine and one ectopic. Triplet heterotopic pregnancy refers to the presence of specifically 3 concurrent gestations with at least 1 being abnormally implanted. Heterotopic pregnancy is a potentially life-threatening condition that requires thorough diagnostic workup and prompt intervention. Case: We report the fourth case of triplet heterotopic pregnancy after ovarian stimulation with gonadotropins. A 24-year-old woman, G0, presented at 6 weeks of gestation with bilateral tubal ectopic pregnancies and a nonviable intrauterine pregnancy (IUP) after gonadotropin stimulation cycle. Bilateral tubal pregnancies were removed laparoscopically and the nonviable IUP via dilation and curettage. Conclusion: Although rare, heterotopic pregnancy of 2 or more gestations must be kept in mind when managing patients undergoing treatment with ART. Careful examination of bilateral adnexa and consideration of uterine sampling at the time of surgery for ectopic pregnancy is advisable, even for patients with few or no risk factors.

ABCC1 confers tissue-specific sensitivity to cortisol versus corticosterone: A rationale for safer glucocorticoid replacement therapy.

The aim of treatment in congenital adrenal hyperplasia is to suppress excess adrenal androgens while achieving physiological glucocorticoid replacement. However, current glucocorticoid replacement regimes are inadequate because doses sufficient to suppress excess androgens almost invariably induce adverse metabolic effects. Although both cortisol and corticosterone are glucocorticoids that circulate in human plasma, any physiological role for corticosterone has been neglected. In the brain, the adenosine 5'-triphosphate-binding cassette transporter ABCB1 exports cortisol but not corticosterone. Conversely, ABCC1 exports corticosterone but not cortisol. We show that ABCC1, but not ABCB1, is expressed in human adipose and that ABCC1 inhibition increases intracellular corticosterone, but not cortisol, and induces glucocorticoid-responsive gene transcription in human adipocytes. Both C57Bl/6 mice treated with the ABCC1 inhibitor probenecid and FVB mice with deletion of Abcc1 accumulated more corticosterone than cortisol in adipose after adrenalectomy and corticosteroid infusion. This accumulation was sufficient to increase glucocorticoid-responsive adipose transcript expression. In human adipose tissue, tissue corticosterone concentrations were consistently low, and ABCC1 mRNA was up-regulated in obesity. To test the hypothesis that corticosterone effectively suppresses adrenocorticotropic hormone (ACTH) without the metabolic adverse effects of cortisol, we infused cortisol or corticosterone in patients with Addison's disease. ACTH suppression was similar, but subcutaneous adipose transcripts of glucocorticoid-responsive genes were higher after infusion with cortisol rather than with corticosterone. These data indicate that corticosterone may be a metabolically favorable alternative to cortisol for glucocorticoid replacement therapy when ACTH suppression is desirable, as in congenital adrenal hyperplasia, and justify development of a pharmaceutical preparation.

Glucocorticoids Acutely Increase Brown Adipose Tissue Activity in Humans, Revealing Species-Specific Differences in UCP-1 Regulation.

The discovery of brown adipose tissue (BAT) in adult humans presents a new therapeutic target for metabolic disease; however, little is known about the regulation of human BAT. Chronic glucocorticoid excess causes obesity in humans, and glucocorticoids suppress BAT activation in rodents. We tested whether glucocorticoids regulate BAT activity in humans. In vivo, the glucocorticoid prednisolone acutely increased (18)fluorodeoxyglucose uptake by BAT (measured using PET/CT) in lean healthy men during mild cold exposure (16°C-17°C). In addition, prednisolone increased supraclavicular skin temperature (measured using infrared thermography) and energy expenditure during cold, but not warm, exposure in lean subjects. In vitro, glucocorticoids increased isoprenaline-stimulated respiration and UCP-1 in human primary brown adipocytes, but substantially decreased isoprenaline-stimulated respiration and UCP-1 in primary murine brown and beige adipocytes. The highly species-specific regulation of BAT function by glucocorticoids may have important implications for the translation of novel treatments to activate BAT to improve metabolic health.

Skeletal muscle salt inducible kinase 1 promotes insulin resistance in obesity.

OBJECTIVE: Insulin resistance causes type 2 diabetes mellitus and hyperglycemia due to excessive hepatic glucose production and inadequate peripheral glucose uptake. Our objectives were to test the hypothesis that the proposed CREB/CRTC2 inhibitor salt inducible kinase 1 (SIK1) contributes to whole body glucose homeostasis in vivo by regulating hepatic transcription of gluconeogenic genes and also to identify novel SIK1 actions on glucose metabolism. METHODS: We created conditional (floxed) SIK1-knockout mice and studied glucose metabolism in animals with global, liver, adipose or skeletal muscle Sik1 deletion. We examined cAMP-dependent regulation of SIK1 and the consequences of SIK1 depletion on primary mouse hepatocytes. We probed metabolic phenotypes in tissue-specific SIK1 knockout mice fed high fat diet through hyperinsulinemic-euglycemic clamps and biochemical analysis of insulin signaling. RESULTS: SIK1 knockout mice are viable and largely normoglycemic on chow diet. On high fat diet, global SIK1 knockout animals are strikingly protected from glucose intolerance, with both increased plasma insulin and enhanced peripheral insulin sensitivity. Surprisingly, liver SIK1 is not required for regulation of CRTC2 and gluconeogenesis, despite contributions of SIK1 to hepatocyte CRTC2 and gluconeogenesis regulation ex vivo. Sik1 mRNA accumulates in skeletal muscle of obese high fat diet-fed mice, and knockout of SIK1 in skeletal muscle, but not liver or adipose tissue, improves insulin sensitivity and muscle glucose uptake on high fat diet. CONCLUSIONS: SIK1 is dispensable for glycemic control on chow diet. SIK1 promotes insulin resistance on high fat diet by a cell-autonomous mechanism in skeletal muscle. Our study establishes SIK1 as a promising therapeutic target to improve skeletal muscle insulin sensitivity in obese individuals without deleterious effects on hepatic glucose production.

Smoking cessation and the risk of cardiovascular disease outcomes predicted from established risk scores: results of the Cardiovascular Risk Assessment among Smokers in Primary Care in Europe (CV-ASPIRE) study.

BACKGROUND: Smoking is a major risk factor for cardiovascular disease (CVD). This multicenter, cross-sectional survey was designed to estimate the cardiovascular (CV) risk attributable to smoking using risk assessment tools, to better understand patient behaviors and characteristics related to smoking, and characterize physician practice patterns. METHODS: 1,439 smokers were recruited from Europe during 2011. Smokers were ≥40 years old, smoked > 10 cigarettes/day and had recent measurements on blood pressure and lipids. CV risk was calculated using the SCORE system, Framingham risk equations, and Progetto CUORE model. The CV risk attributable to smoking was evaluated using a simulated control (hypothetical non-smoker) with identical characteristics as the enrolled smoker. Risks assessed included CV mortality, coronary heart disease (CHD), CVD and hard CHD. Demographics, comorbidities, primary reasons for consultation, behavior towards previous attempts to quit, and interest in smoking cessation was assessed. Dependence on nicotine was evaluated using the Fagerström Test for Nicotine Dependence. GP practice patterns were assessed through a questionnaire. RESULTS: The prediction models consistently demonstrated a high CV risk attributable to smoking. For instance, the SCORE model demonstrated that this study population of smokers have a 100% increased probability of death due to cardiovascular disease in the next 10-years compared to non-smokers. A considerable amount of patients would like to hear from their GP about the different alternatives available to support their quitting attempt. CONCLUSIONS: The findings of this study reinforce the importance of smoking as a significant predictor of long-term cardiovascular events. One of the best gains in health could be obtained by tackling the most important modifiable risk factors; these results suggest smoking is among the most important.