Gloria Appolloni

Pathophysiology of dyslipidemia in Cushing's syndrome.

Dyslipidemia seems to be less frequent than other metabolic comorbidities in human Cushing’s syndrome. Nevertheless, it plays an important role in determining the global cardiovascular risk in overt and subclinical Cushing’s syndrome. In Cushing’s syndrome, there is an increase of triglyceride and total cholesterol levels whereas HDL can be at variable levels. Overt and subclinical Cushing’s syndrome share many features with metabolic syndrome including insulin resistance, abnormal fasting glucose levels, hypertension, obesity and dyslipidemia. The pathogenetic mechanisms are multifactorial, including direct and indirect cortisol action on lipolysis, free fatty acid production and turnover, very-low-density lipoprotein synthesis and fatty accumulation in the liver. AMP-activated protein kinase mediates many of glucocorticoid-induced metabolic changes. Insulin resistance plays a key role in determining lipid abnormalities. Other hormonal changes are involved including growth hormone, testosterone in men and estrogen in women, catecholamines and cytokines. In vitro, cortisol increases lipoprotein lipase in adipose tissues and particularly in visceral fat where lipolysis is activated, resulting in the release of free fatty acids into the circulation. The increase of free fatty acids may enhance the accumulation of hepatic lipids reducing glucose uptake and activating various serine kinases which results in decreased insulin signaling. Moreover, mice with a liver-specific disruption of the glucocorticoid receptor had diminished hepatic triglycerides levels. In humans, a high prevalence (up to 20%) of hepatic steatosis was also reported in patients with Cushing’s syndrome. Genetic variations in the glucocorticoid receptors may also affect the activity of cortisol, lipid metabolism and cardiovascular risk.

Coagulopathy in Cushing’s Syndrome

A hypercoagulable state and its consequent increased incidence of thromboembolic complications are reported in patients with Cushing’s syndrome (CS). These alterations are related to cortisol excess that induces prothrombotic changes in blood by several and complex mechanisms including increased levels of clotting factors, mainly factor VIII and von Willebrand factor (VWF) and impaired fibrinolytic capacity. However, it has recently been observed that the increase in VWF levels is not a constant feature of CS and that VWF response to glucocorticoids is genetically determined and depends on the presence of particular polymorphisms in the VWF gene promoter. The risk of venous thromboembolism is moreover enhanced in patients with CS by additional endogenous and exogenous risk factors such as obesity, bed rest, surgery and invasive diagnostic procedures like inferior petrosal sinus (IPS) sampling. In line with all these data, patients with active CS should be treated as having a prothrombotic disorder and undergo antithrombotic prophylaxis during IPS sampling. Special care should be taken in the immediate perioperative period in order to avoid thromboembolic events. In the absence of prospective randomized trials, preventive antithrombotic treatment (best with heparin) during IPS sampling and low-dose heparin treatment early after surgery should be suggested.

Association of glucocorticoid receptor polymorphism A3669G with decreased risk of developing diabetes in patients with Cushing's syndrome.

OBJECTIVE Glucocorticoid receptor (GR) polymorphisms alter glucocorticoid (GC) sensitivity and have been associated with altered metabolic profiles. We evaluate the prevalence of the four GR (NR3C1) polymorphisms BclI, N363S, ER22/23EK, and A3669G in patients with Cushings syndrome (CS) compared with healthy controls (HC) and we investigate their role in the development of metabolic abnormalities in patients with CS according to their hormonal profile. PATIENTS AND METHODS Sixty-one patients with CS and 71 sex- and age-matched HC were genotyped. RESULTS BclI variant was markedly higher in patients with CS compared with HC (62 vs 41%, P<0.05) while no significant differences were found among other polymorphisms. A very low frequency of N363S and the ER22/23EK was observed. In CS patients, despite the significantly increased levels of morning serum cortisol in BclI carriers compared with wild type no clinical or metabolic differences were found. In contrast, A3669G GR carriers showed a significantly reduced prevalence of type 2 diabetes mellitus compared with wild type (19 vs 68%, P=0.001) despite the higher levels of both serum morning (21.7±6 vs 27.3±8.6 μg/dl, P=0.009) and midnight cortisol (18.8±5.8 vs 24.0±8.0 μg/dl, P=0.01). The negative association between diabetes and A3669G GR polymorphism remained significant when data were adjusted for potential confounding factors. CONCLUSIONS The A3669G polymorphism of the GR gene plays a protective role in patients with CS, attenuating the effects of GC excess on glucose metabolism as shown by their reduced risk of diabetes.

A new germline point mutation in Ret exon 8 (Cys515Ser) in a family with medullary thyroid carcinoma

BACKGROUND A novel Cys-Ser Ret germline point mutation in a 58-year-old woman with bilateral medullary thyroid carcinoma (MTC) prompted us to perform genetic analysis of the family and evaluate the biological consequences of such a mutation. METHODS Ret analysis by direct sequencing was performed in five family members. The biological activity and biochemical properties of the Ret- Cys515Ser mutant were analyzed in NIH-3T3 cells. RESULTS The probands son, age 35, had the Ret- Cys515Ser mutation and the L769 CTT/CTG exon 13 polymorphic variant, which was also found in his father. Clinical evaluation of the son also revealed bilateral multifocal microscopic MTC and papillary thyroid carcinoma (PTC). In vitro and in vivo analysis indicated ligand-independent activation of the Ret-Cys515Ser mutant due to aberrant disulfide homodimerization, increased mitogenic activity, and ability to induce anchorage-independent growth in NIH-3T3 cells in comparison to wild-type Ret, suggesting a possible role of Cys515Ser in tumor development. CONCLUSIONS The Cys515Ser mutation adds to cysteine substitution groups that have been described in association with MTC. Our data also highlight the importance of performing a complete genetic analysis in patients who present with MTC.

Bone complications in patients with Cushing's syndrome: looking for clinical, biochemical, and genetic determinants.

SummaryThis is the first study examining the impact of both clinical, biochemical, and genetic determinants in the occurrence of bone complications in patients with overt Cushing’s syndrome (CS). It demonstrates that the degree and duration of hypercortisolism seem to play a major role in bone loss and fractures development in these patients.IntroductionBone loss and fractures are a common complication of CS. We investigate the role of gender, disease etiology, duration, and degree of hypercortisolism as well as the impact of glucocorticoid receptor (GR) polymorphisms on the development of bone complications in CS.MethodsFifty-two patients with active CS (38 Cushing’s disease and 14 with cortisol-secreting adrenal adenoma) were genotyped for GR polymorphisms (BclI, N363S, ER22/23EK, and A3669G). In all patients, clinical, hormonal, and biochemical markers of bone turnover, densitometric parameters [lumbar spine and left femur bone mineral density (BMD), T-score, Z-score] as well as the prevalence of bone demineralization and both vertebral and peripheral fractures were assessed.ResultsNo differences were found in bone complications according to gender, disease etiology, and genetic variants distribution. Fractured patients compared to non-fractured ones showed increased levels of urinary free cortisol (UFC) and a more compromised densitometric profile. UFC levels correlated with the occurrence of vertebral fractures (r = 0.43, p = 0.009) while midnight serum cortisol correlated with L1–L4 BMD values (r = −0.35, p = 0.04). Disease duration correlated with the presence of peripheral fractures (r = 0.36, p = 0.04).ConclusionsWhile GR gene variants as well as gender and disease etiology seem not to play a role, the degree and duration of hypercortisolism seem to be the major determinants of bone loss and fractures in this group of patients. More investigations are needed to understand the real impact of these determinants on the development of bone complications in patients with hypercortisolism.

Aldosterone, mineralocorticoid receptor and the metabolic syndrome: role of the mineralocorticoid receptor antagonists.

Several lines of evidence suggest a detrimental effect of aldosterone excess on the development of metabolic alterations. Glucose metabolism derangements due to aldosterone action are frequently observed not only in patients with primary aldosteronism but also in patients with obesity. A contribution to the hyperaldosteronism observed in obese subjects can be attributed, at least in part, to the action of still unidentified adipocyte-derived factor. Aldosterone, through genomic and non-genomic actions contributes to induce several abnormalities: pancreatic fibrosis, impaired beta cell function, as well as reduced skeletal muscle and adipose tissue insulin sensitivity. Oxidative stress, systemic inflammation, together with these metabolic alterations may explain the appearance of the cardiometabolic syndrome and the progression of cardiovascular and renal diseases, in the presence of inappropriate aldosterone levels. The biological actions of aldosterone are mediated by mineralocorticoid receptor (MR), although MR can be activated through an aldosterone independent fashion. Besides salt-water homeostasis, MR activation promotes inflammation, endothelial dysfunction, cardiovascular remodelling and affects adipose tissue differentiation and function. Clinical and experimental studies have shown that MR blockade is able to suppress inflammation, to improve endothelium- dependent vasorelaxation, but most interestingly, to improve pancreatic insulin release as well as insulin-mediated glucose utilization. These actions indicate MR antagonists as a useful therapeutic tool able not only to reduce cardiovascular risk and renal damage, but also to improve metabolic sequaelae.

Expression of growth hormone-releasing hormone receptor splicing variants in human primary adrenocortical tumours.

Objective Several splice variants (SVs) of GHRH receptor (GHRH‐R) have been identified in various human cancers through which GHRH antagonists may exert their IGF‐II‐mediated antiproliferative action. Because the overexpression of the IGF‐II gene is a frequent feature of adrenal carcinoma, we searched for the presence of GHRH‐R SVs in these tumours.