Clinical consequences of Cushing’s syndrome

Recent evidence suggests that correction of hypercortisolism in Cushing's syndrome (CS) may not lead to complete remission of the clinical abnormalities associated with this condition. In particular, elevated cardiovascular risk may persist in "cured" CS patients long-term after eucortisolism has been reached. This is believed to be related with the maintenance of visceral obesity and altered adipokine secretory pattern which perpetuate features of metabolic syndrome, including impaired glucose tolerance, hypertension, dyslipidemia, atherosclerosis and hypercoagulability. Nephrolithiasis and incomplete recovery of bone mineral density have also been described in "cured" CS patients. Moreover, previous exposure to excess cortisol may have irreversible effects on the structures of the central nervous system controlling cognitive function and mood. Thus, sustained deterioration of the cardiovascular system, bone remodelling and cognitive function may be associated with high morbidity and poor quality of life in CS patients in remission for many years. Although mortality in "cured" CS patients may not differ from that in the general population, data beyond 20?years follow-up are very scarce, so further studies evaluating larger cohorts for longer follow-up periods are needed to draw definitive conclusions on longevity. Life-long monitoring is mandatory in CS patients in order to control long term complications of previous cortisol excess and, possibly, normalize life expectancy.     

Adipokine levels and cardiovascular risk in patients with adrenal incidentaloma

Adrenal incidentalomas (AIs) have been associated with an increased incidence of several cardiovascular risk factors, similar to overt Cushing syndrome. Data about the involvement of the adipokines in the development of insulin resistance and atherosclerosis in AI are completely lacking. The aim of the present study was to evaluate plasma interleukin 6 (IL-6), adiponectin, resistin, tumor necrosis factor alpha (TNF-alpha), and monocyte chemoattractant protein 1 (MCP-1) levels in patients with AI. Plasma IL-6, adiponectin, resistin, TNF-alpha, and MCP-1 levels were measured in 20 healthy subjects (6 males; 14 females; age, 58.5 +/- 2.2 years; body mass index, 28.1 +/- 0.9 kg/m(2)) and in 20 patients (5 males; 15 females; age, 57.9 +/- 2.0 years; body mass index, 28.0 +/- 0.8 kg/m(2)) with AI and typical computed tomographic features of cortical adenoma, who were not affected by diabetes mellitus, hypertension, or other relevant diseases. All patients underwent anthropometric measurements and determination of basal corticotropin, cortisol, and urinary free cortisol excretion. Overnight dexamethasone test and 250-microg corticotropin test were performed in all cases. A subclinical Cushing syndrome was found in 3 patients, whereas the others had apparently nonfunctioning masses. Plasma IL-6, adiponectin, resistin, TNF-alpha, and MCP-1 levels were higher in patients than in controls (64.4 +/- 2.8 vs 5.5 +/- 0.6 pg/mL, 13.7 +/- 1.3 vs 3.6 +/- 0.5 microg/mL, 12.5 +/- 1.9 vs 5.1 +/- 0.2 ng/mL, 27.0 +/- 1.5 vs 22.2 +/- 1.5 pg/mL, 172.5 +/- 20.0 vs 104.4 +/- 19.5 pg/mL, respectively; P < .05) and apparently not affected by the presence of visceral obesity. Plasma IL-6 levels were negatively correlated with urinary free cortisol (r = -0.461, P < .05), and TNF-alpha levels were positively correlated with cortisol after the administration of 1 mg dexamethasone (r = 0.636, P < .01). In conclusion, patients with AI may show increased levels of adipokines (apparently not related to the presence of diabetes, hypertension, or obesity), which may be affected by the presence of the adrenal adenoma. For some adipokines, a direct production from the adrenal gland may be hypothesized even if other studies are needed to better investigate the role of adipokines in states of altered cortisol secretion.     

Impact of increased adipose tissue mass on inflammation, insulin resistance, and dyslipidemia

Obesity is associated with increased prevalence of metabolic disorders, such as inflammation, insulin resistance, and dyslipidemia, which can predispose an individual to develop diabetes and cardiovascular disease. Adipose tissue (AT) is now recognized as a metabolically active organ that controls plasma free fatty acid levels and contributes to systemic metabolic homeostasis by secreting adipokines. In obesity, the recruitment of immune cells, such as T cells and macrophages, to AT causes inflammation, which is thought to contribute to local insulin resistance. This loss of insulin sensitivity within AT can lead to uncontrolled release of fatty acids, secretion of inflammatory cytokines, and alterations in the balance of adipokines, which ultimately impact lipoprotein metabolism and insulin sensitivity systemically. Thus, AT itself plays an important role in the increased risk of diabetes and cardiovascular disease that is associated with obesity.     

Adipokine dysregulation,adipose tissue inflammation and metabolic syndrome

Obesity plays a causative role in the pathogenesis of the metabolic syndrome. Adipokines may link obesity to its co-morbidities. Most adipokines with pro-inflammatory properties are overproduced with increasing adiposity, while some adipokines with anti-inflammatory or insulin-sensitizing properties, like adiponectin are decreased. This dysregulation of adipokine production may promote obesity-linked metabolic disorders and cardiovascular disease. Besides considering adipokines, this review will also highlight the cellular key players and molecular mechanisms involved in adipose inflammation. Targeting the changes in the cellular composition of adipose tissue, the underlying molecular mechanisms, and the altered production of adipokines may have therapeutic potential in the management of the metabolic syndrome.     

Cushing's syndrome in pregnancy: an overview

Cushing's syndrome (CS) during pregnancy is a rare condition with fewer than 150 cases reported in the literature. Adrenal adenomas were found to be the commonest cause, followed by Cushing's disease. The gestation dramatically affects the maternal hypothalamic-pituitary-adrenal axis, resulting in increased hepatic production of corticosteroid-binding globulin (CBG), increased levels of serum, salivary and urinary free cortisol, lack of suppression of cortisol levels after dexamethasone administration and placental production of CRH and ACTH. Moreover, a blunted response of ACTH and cortisol to exogenous CRH may also occur. Therefore, the diagnosis of CS during pregnancy is much more difficult. Misdiagnosis of CS is also common, as the syndrome may be easily confused with preeclampsia or gestational diabetes. Because CS during pregnancy is usually associated with severe maternal and fetal complications, its early diagnosis and treatment are critical. Surgery is the treatment of choice for CS in pregnancy, except perhaps in the late third trimester, with medical therapy being a second choice. There does not seem to be a rationale for supportive treatment alone.     

Emerging role of adipokines as mediators in atherosclerosis

Atherosclerotic cardiovascular disease is a major health problem around the world. Obesity is a primary risk factor for atherosclerosis and is associated with increased morbidity and mortality of cardiovascular diseases. However, the precise molecular pathways underlying this close association remain poorly understood. Adipokines are cytokines, chemokines and hormones secreted by adipose tissue that couple the regulation of lipid accumulation, inflammation, and atherogenesis, and therefore serve to link obesity with cardiovascular disorders. Obesity-related disorders including metabolic syndrome, diabetes, atherosclerosis, hypertension, and coronary artery disease are associated with dysregulated adipokine(s) expression. Recent studies demonstrate the proinflammatory effects as well as atherogenic properties of adipokines. Adipokines also participate in the regulation of endothelial function, which is an early event in atherosclerosis. By contrast, adiponectin, an adipocyte-derived hormone, exerts anti-inflammatory, anti-atherogenic and vascular protective effects. Furthermore, there is an interactive association among adipokines, by which adipokines reciprocally regulate each other's expression. Understanding this interplay may reveal plausible mechanisms for treating atherosclerosis and coronary heart disease by modulating adipokine(s) expression. In this review, we discuss insights into the role and the therapeutic potential of adipokines as mediators of atherosclerosis.     

Obesity as the common soil of non‐alcoholic fatty liver disease and diabetes: Role of adipokines

Non‐alcoholic fatty liver disease (NAFLD) describes a spectrum of liver conditions from simple steatosis, steatohepatitis to end‐stage liver disease. The prevalence of NAFLD has been on the rise in many parts of the world, including Asia, and NAFLD is now the liver disease associated with the highest mortality, consequent to the increased risk of cardiovascular diseases and hepatocellular carcinoma. Whereas NAFLD is an independent risk factor for type 2 diabetes, increased hepatic and peripheral insulin resistance contribute to the pathogenesis of both NAFLD and diabetes, which are associated with enhanced cardiovascular risk. Studies in humans and animal models have suggested obesity as the common link of these two diseases, likely mediated by adipose tissue inflammation and dysregulated adipokine production in obesity. In the present review, we discuss recent advances in our understanding of the role of several novel adipokines (adiponectin, adipocyte fatty acid binding protein and fibroblast growth factor‐21) in the pathophysiology of NAFLD and diabetes, as well as their use as potential biomarkers and therapeutic targets for dysglycemia in NAFLD patients.     

Steroid metabolism in metabolic syndrome X

Preceding chapters in this volume describe relatively rare conditions associated with qualitative rather than quantitative changes in enzymes involved in steroid synthesis and metabolism. In this chapter, several examples show how more subtle variations in activities of the same enzymes may be important in the pathophysiology of common diseases of complex aetiology. This chapter reviews evidence for deranged steroid metabolism in patients with the 'insulin resistance syndrome'. In summary, patients with essential hypertension may have subtle 11beta-hydroxylase or 11beta-hydroxysteroid dehydrogenase type 2 deficiency resulting in mild mineralocorticoid excess. Patients with obesity, and/or associated hirsutism or hyperglycaemia, have evidence of altered peripheral metabolism of androgens (increased 5alpha-reductase) and glucocorticoids (altered 11beta-hydroxysteroid dehydrogenase type 1, resulting in enhanced cortisol levels in adipose tissue). Some of these changes in steroid metabolism lend themselves to therapeutic manipulation which may provide novel strategies to reduce cardiovascular risk.     

The hypothalamic-pituitary-adrenal axis in pregnancy: challenges in disease detection and treatment

Pregnancy dramatically affects the hypothalamic-pituitary-adrenal axis leading to increased circulating cortisol and ACTH levels during gestation, reaching values in the range seen in Cushing's syndrome (CS). The cause(s) of increased ACTH may include placental synthesis and release of biologically active CRH and ACTH, pituitary desensitization to cortisol feedback, or enhanced pituitary responses to corticotropin-releasing factors. In this context, challenges in diagnosis and management of disorders of the hypothalamic-pituitary-adrenal axis in pregnancy are discussed. CS in pregnancy is uncommon and is associated with fetal morbidity and mortality. The diagnosis may be missed because of overlapping clinical and biochemical features in pregnancy. The proportion of patients with primary adrenal causes of CS is increased in pregnancy. CRH stimulation testing and inferior petrosal sinus sampling can identify patients with Cushing's disease. Surgery is a safe option for treatment in the second trimester; otherwise medical therapy may be used. Women with known adrenal insufficiency that is appropriately treated can expect to have uneventful pregnancies. Whereas a fetal/placental source of cortisol may mitigate crisis during gestation, unrecognized adrenal insufficiency may lead to maternal or fetal demise either during gestation or in the puerperium. Appropriate treatment and management of labor are reviewed.     

The link between abdominal obesity and the metabolic syndrome

The clustering of cardiovascular risk factors associated with abdominal obesity is well established. Although currently lacking a universal definition, the metabolic syndrome describes a constellation of metabolic abnormalities, including abdominal obesity, and was originally introduced to characterize a population at high cardiovascular risk. Adipose tissue is a dynamic endocrine organ that secretes several inflammatory and immune mediators known as adipokines. Dysregulation of adipokine secretion, free fatty acid toxicity, and the site-specific differences in abdominal (visceral) versus subcutaneous fat support abdominal obesity as a causal factor mediating the insulin resistance, increased risk of diabetes, and cardiovascular disease in the metabolic syndrome.     

脂肪因子与慢性心力衰竭研究进展

慢性心力衰竭的发病率和病死率高。肥胖、高血压和糖尿病等为慢性心力衰竭的传统危险因素,但近期研究表明发现肥胖的慢性心力衰竭患者预后较好,这一现象被人称为“肥胖悖论”。脂肪组织目前被认为是一种内分泌组织,分泌的多种脂肪因子可调控多种心血管功能。现综述可影响心血管功能的脂肪因子。     

Cortisol—cause and cure for metabolic syndrome?

Similarities between the metabolic syndrome and Cushing's syndrome, and reversibility of the features of Cushing's syndrome, suggest that cortisol may contribute to the pathophysiology of both conditions and that reducing cortisol action may provide a novel therapeutic approach in the metabolic syndrome. There is substantial evidence that circulating cortisol concentrations are higher in people with hypertension and glucose intolerance. The basis for this activation of the hypothalamic-pituitary-adrenal axis remains uncertain, but it may be attributable to 'programming' effects of events in early life, since it is associated with low birth weight. In obese people, intracellular cortisol levels within adipose tissue are further amplified by increased local regeneration of cortisol by the enzyme 11beta-HSD type 1. In mice, transgenic manipulations of 11beta-HSD1 have potent effects on obesity and associated features of the metabolic syndrome. Promising preclinical data suggest that novel 11beta-HSD1 inhibitors will have a role in lowering intracellular cortisol levels as a treatment for the metabolic syndrome. In addition to their metabolic effects, glucocorticoids act in the blood vessel wall. Pharmacoepidemiological studies suggest that glucocorticoid excess is an independent risk factor for cardiovascular disease. Recent data suggest that 11beta-HSD1 within the blood vessel wall influences vascular remodelling and angiogenesis, for example in the myocardium following coronary artery occlusion. Thus, glucocorticoid signalling provides a potentially tractable system to influence both risk factors for, and the outcome of, Type 2 diabetes and cardiovascular disease.     

Adipokines and dietary interventions in human obesity

Obesity is a multisystem disorder associated with cardiovascular and metabolic complications. According to recent studies, it is characterized as a condition of low‐grade inflammation with altered adipose tissue function and secretion of various adipokines. One of the strategies in obesity treatment is dietary intervention (DI) that could modulate cytokine levels in a favourable way. The aim of this review was to summarize the results of studies performed in the last 13 years investigating DI programmes accompanied with weight loss in relation to profile of adipokines at different level (adipose tissue mRNA, adipose tissue secretion and circulating level) and identify whether modulations of adipokines are implicated in the positive effects of DIs. The overall finding is that DIs leading to 5–10% weight loss modulate production of certain adipokines and generally induce improvement of clinical parameters, e.g. insulin sensitivity, but the amelioration of obesity complications is not coherent with the pattern of adipokine regulation, except maybe for leptin. Global analysis of the adipose tissue secretome and measurement of panels of adipokines may prove more informative than studies on individual molecules.     

Differences in cortisol concentrations in South Asian and European men living in the United Kingdom

OBJECTIVE: The metabolic syndrome is more prevalent in South Asians in Britain than in the general population. Furthering our understanding of the underlying mechanisms is important because of the increased risk of cardiovascular disease associated with the metabolic syndrome. As it has been proposed that increased activity of the hypothalamic pituitary adrenal axis might underlie the metabolic syndrome, we hypothesized that plasma cortisol levels would be higher in South Asians and that increased cortisol levels would be associated with cardiovascular risk factors comprising the metabolic syndrome. The aim of the study was to examine ethnic differences in cortisol levels and to compare the relationships between cortisol levels and cardiovascular risk factors in men from different ethnic groups. DESIGN: Cross-sectional population-based study, Newcastle upon Tyne, UK. (Newcastle Heart project). Participants One hundred men, 40-67 years old, of European and South Asian (Indian, Pakistani, Bangladeshi) ancestry, with and without cardiovascular risk factors of the metabolic syndrome. MEASUREMENTS: Measurement of plasma cortisol and corticosteroid binding globulin in stored sera. RESULTS: After adjustment for age and the presence of cardiovascular risk factors, mean cortisol was 27% (95% CI, 10%, 40%) lower in South Asians compared to Europeans. Cortisol levels were higher in all men with cardiovascular risk factors than those without. CONCLUSIONS: Cortisol levels are lower in South Asian than in European men resident in the UK. Despite lower cortisol levels in South Asians, the relations between cortisol and cardiovascular risk factors remain strong.     

Adipose tissue and adipokines: for better or worse

It is now recognized that the white adipose tIssue (WAT) produces a variety of bioactive peptIdes, collectively termed "adipokines". Alteration of WAT mass in obesity or lipoatrophy, affects the production of most adipose secreted factors. Since both conditions are associated with multiple metabolic disorders and increased risk of cardiovascular diseases, the Idea has emerged that WAT could be instrumental in these complications, by virtue of its secreted factors. Several adipokines are increased in the obese state and have been implicated in hypertension (angiotensinogen), impaired fibrinolysis (PAI-1) and insulin resistance (ASP, TNFalpha, IL-6, resistin). Conversely, leptin and adiponectin both exert an insulin-sensitizing effect, at least in part, by favoring tIssue fatty-acId oxIdation through activation of AMP-activated kinase. In obesity, insulin resistance has been linked to leptin resistance and decreased plasma adiponectin. In lipoatrophic mice, where leptin and adiponectin circulating levels are low, administration of the two adipokines synergistically reverses insulin resistance. Leptin and adiponectin also have distinct properties: leptin, as a long-term integrative signal of energy store and adiponectin, as a potent anti-atherogenic agent. The thiazolIdinedione anti-diabetic drugs increase endogenous adiponectin production in rodents and humans, supporting the Idea that the development of new drugs targeting adipokines might represent a promising therapeutic approach to protect obese patients from insulin resistance and atherosclerosis.     

An update on metabolic syndrome: Metabolic risk markers and adipokines in the development of metabolic syndrome

BackgroundMetabolic syndrome is a collection of physiological and biochemical abnormalities about 20–25% of adult population in developing countries is suffering from metabolic syndrome. Previous research demonstrated that adipose tissue plays an important role in energy regulation via endocrine, paracrine and autocrine signals as results of obesity due to accumulation of adipose tissue to excess that by time affects negatively both physical and psychological health and well being, it has been found that adipose tissues produces a variety of factors known as “adipokines” which play a key role in the development and progression of the disease and also hypothesized that adipokines are a possible link between obesity and the other risk components of the Metabolic syndrome. Many of the adipokines exert multiple actions in a variety of cellular processes leading to a complex array of abnormal characteristic of Metabolic syndrome. Abnormal production of these adipokines by expanded visceral fat during Adiposity contributes to a pro-inflammatory state. Increasing evidence suggests that aberrant production/release of adipokine from adipocyte i.e. adiponectin, leptin and resistin etc, may contribute to the health problems associated with Adiposity such as dyslipidemia, insulin resistance and atherosclerosis. This study conclusively have shown a significant role of adipokines secreted by adipose tissue and various metabolic risk markers play a important role in the development of Metabolic syndrome.     

Cortisol and the metabolic syndrome in South Asians

OBJECTIVE: The cardiovascular risk factors which comprise the metabolic syndrome are associated with increased hypothalamic-pituitary-adrenal axis (HPAA) activity in some Caucasian populations. South Asians have high rates of cardiovascular disease and its risk factors. We have investigated the relationships between HPAA activity, adiposity and the metabolic syndrome in a South Asian population. DESIGN: Cross-sectional cohort study. PARTICIPANTS: A total of 509 men and women born at the Holdsworth Memorial Hospital, Mysore, South India between 1934 and 1954 and still living in the area. MEASUREMENTS: Fasting 09.00 h cortisol and corticosteroid-binding globulin. The cohort had previously been investigated for features of the metabolic syndrome. RESULTS: At 09.00 h, cortisol concentration was strongly associated with systolic and diastolic blood pressure (r = 0.25 and r = 0.24, respectively; P < 0.001), fasting glucose concentration (r = 0.26; P < 0.001), insulin resistance (r = 0.20; P < 0.001) and fasting triglyceride concentration (r = 0.17; P < 0.001). In general, higher cortisol concentrations added to the effect of adiposity in increasing cardiovascular risk factors, but there was evidence of an interaction between cortisol and adiposity in determining fasting glucose concentration (P = 0.045) and insulin resistance (P = 0.006). CONCLUSIONS: Associations between 09.00 h cortisol concentration and cardiovascular risk factors in this South Asian cohort were stronger than those previously shown in Caucasian populations, despite similar mean cortisol concentrations, and were amplified by adiposity. This suggests that increased glucocorticoid action may contribute to ethnic differences in the prevalence of the metabolic syndrome, particularly among men and women with a higher body mass index.     

Adipose tissue dysfunction and hypertriglyceridemia: mechanisms and management

Elevated plasma triglyceride levels, as often seen in obese subjects, are independently associated with an increased risk of cardiovascular diseases. By secreting adipokines (such as adiponectin and leptin) and other proteins (such as lipoprotein lipase and cholesteryl ester transferase protein), adipose tissue affects triglyceride metabolism. In obesity, adipocyte hypertrophy leads to many changes in adipocyte function and production of anti‐ and pro‐inflammatory cytokines. Furthermore, free fatty acids are released into the circulation contributing to insulin resistance. Adipose tissue dysfunction will eventually lead to abnormalities in lipid metabolism, such as hypertriglyceridemia (due to increased hepatic very‐low‐density lipoprotein production and decreased triglyceride hydrolysis), small dense low‐density lipoprotein particles, remnant lipoproteins and low high‐density lipoprotein cholesterol levels, all associated with a higher risk for the development of cardiovascular diseases. The clinical implications of elevated plasma triglycerides are still a matter of debate. Understanding the pathophysiology of adipose tissue dysfunction in obesity, which is becoming a pandemic condition, is essential for designing appropriate therapeutic interventions. Lifestyle changes are important to improve adipose tissue function in obese patients. Pharmacological interventions to improve adipose tissue function need further evaluation. Although statins are not very potent in reducing plasma triglycerides, they remain the mainstay of therapy for cardiovascular risk reduction in high‐risk patients.     

Adipokine levels in Cushing's syndrome; elevated resistin levels in female patients with Cushing's syndrome

BACKGROUND: Cushing's syndrome (CS) is associated with central adiposity, insulin resistance and impaired glucose homeostasis. Adipose tissue is thought to regulates glucose homeostasis via circulating adipokines, such as resistin, leptin and adiponectin, although their role in the insulin resistance associated with CS has not been established. DESIGN: We examined the relationship between insulin resistance and adipokine levels in CS patients. We compared plasma levels of resistin, leptin and adiponectin in 10 women and four men patients with CS, with 14 health subjects matched for age, gender and body mass index. A subgroup of three women and four men with pituitary-dependent CS were re-examined at least 9 months after curative surgery. RESULTS: CS patients had significantly more truncal fat and less lean body mass as assessed by DEXA compared to control subjects. Total cholesterol, triglycerides and insulin resistance, as calculated using the homeostasis model assessment of insulin resistance (HOMA-R), was significantly increased in CS patients. Of the adipokines measured, only resistin was significantly different between female CS patients and female control subjects (5.05 +/- 0.56 vs. 2.91 +/- 0.39 micro g/l, P = 0.015). Curative surgery significantly reduced total body fat and truncal fat, leptin, total and low-density lipoprotein (LDL) cholesterol, glucose and HOMA-R. A reduction in both resistin and adiponectin was also observed but the differences between pre- and post-treatment levels did not achieve statistical significance. CONCLUSION: Here we report for the first time that resistin levels are significantly elevated in CS patients and may be important in the insulin resistance associated with glucocorticoid excess.