Tingwei Su

Activating Hotspot L205R Mutation in PRKACA and Adrenal Cushing's Syndrome

Adrenal Cushing’s syndrome is caused by excess production of glucocorticoid from adrenocortical tumors and hyperplasias, which leads to metabolic disorders. We performed whole-exome sequencing of 49 blood-tumor pairs and RNA sequencing of 44 tumors from cortisol-producing adrenocortical adenomas (ACAs), adrenocorticotropic hormone–independent macronodular adrenocortical hyperplasias (AIMAHs), and adrenocortical oncocytomas (ADOs). We identified a hotspot in the PRKACA gene with a L205R mutation in 69.2% (27 out of 39) of ACAs and validated in 65.5% of a total of 87 ACAs. Our data revealed that the activating L205R mutation, which locates in the P+1 loop of the protein kinase A (PKA) catalytic subunit, promoted PKA substrate phosphorylation and target gene expression. Moreover, we discovered the recurrently mutated gene DOT1L in AIMAHs and CLASP2 in ADOs. Collectively, these data highlight potentially functional mutated genes in adrenal Cushing’s syndrome. Adrenal Cushing’s syndrome involves recurrent mutations in a key signal transduction pathway [Also see Perspective by Kirschner] Candidate Cushings culprit identified Cushings syndrome is a rare condition resulting from the excess production of cortisol. About 15% of Cushings syndrome cases are associated with an adrenocortical tumor. However, the genetic etiology of these adrenocortical tumors is ill defined (see the Perspective by Kirschner). Cao et al. and Sato et al. both performed whole-exome sequencing of tumors from individuals with adrenal Cushings syndrome and compared it with the patients own matched non-tumor DNA and identified recurrent mutations in the protein kinase A catalytic subunit alpha (PRKACA) gene, as well as less frequent mutations in other putative pathological genes. The most common recurrent mutation activated the kinase, which may suggest a potential therapeutic target. Science, this issue p. 913, p. 917; see also p. 804

Brown Adipose Tissue in Humans Is Activated by Elevated Plasma Catecholamines Levels and Is Inversely Related to Central Obesity

Background Recent studies have shown that adult human possess active brown adipose tissue (BAT), which might be important in controlling obesity. It is known that ß-adrenoceptor-UCP1 system regulates BAT in rodent, but its influence in adult humans remains to be shown. The present study is to determine whether BAT activity can be independently stimulated by elevated catecholamines levels in adult human, and whether it is associated with their adiposity. Methodology/Principal Findings We studied 14 patients with pheochromocytoma and 14 normal subjects who had performed both 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) and plasma total metanephrine (TMN) measurements during 2007–2010. The BAT detection rate and the mean BAT activity were significantly higher in patients with elevated TMN levels (Group A: 6/8 and 6.7±2.1 SUVmean· g/ml) than patients with normal TMN concentrations (Group B: 0/6 and 0.4±0.04 SUVmean· g/ml) and normal subjects (Group C: 0/14 and 0.4±0.03 SUVmean·g/ml). BAT activities were positively correlated with TMN levels (R = 0.83, p<0.0001) and were inversely related to body mass index (R = −0.47, p = 0.010), visceral fat areas (R = −0.39, p = 0.044), visceral/total fat areas (R = −0.52, p = 0.0043) and waist circumferences (R = −0.43, p = 0.019). Robust regression revealed that TMN (R = 0.81, p<0.0001) and waist circumferences (R = −0.009, p = 0.009) were the two independent predictors of BAT activities. Conclusions/Significance Brown adipose tissue activity in adult human can be activated by elevated plasma TMN levels, such as in the case of patients with pheochromocytoma, and is negatively associated with central adiposity.

Mutation analysis of SCNN1B in a family with Liddle's syndrome

Liddles syndrome has been known as a disorder associated with abnormal sodium reabsorption in the distal tubule and transmitted as a rare autosomal dominant trait. It is caused by mutations in the SCNN1B or SCNN1C gene, which truncate the cytoplasmic carboxyl terminus of the β and γ subunit of the epithelial sodium channel (ENaC). Genetic analysis of ENaC in a Chinese family with Liddles syndrome revealed P616H of SCNN1B coaggregated with the phenotype, while this variant was not detected in 100 unrelated subjects. No mutation at γ ENaC could be detected in all members of the family. P616H is located in the conserved proline-rich PY motif of the βENaC. The PY motif can interact with the WW domain in Nedd4 and affect the activity of ENaC. Structural bioinformatics analysis confirmed that the functional interaction between Nedd4 and ENaC reduces in Liddle-ENaC (P616H) when compared with wild-type ENaC. In summary, P616H may be an underlying mechanism for the signs and symptoms of this family.

Diagnostic Value of ACTH Stimulation Test in Determining the Subtypes of Primary Aldosteronism

BACKGROUND Adrenal venous sampling is recommended as the golden standard for subtyping primary aldosteronism (PA). However, it is invasive and inconvenient, and seeking a better way to make differential diagnosis of PA is necessary. OBJECTIVE The objective of the study was to evaluate the diagnostic value of ACTH stimulation test under 1 mg dexamethasone suppression test (DST) in determining the subtypes of PA. METHODS Ninety-five patients with PA confirmed by saline infusion test were included in this study. According to adrenal venous sampling and histopathology, 39 patients were diagnosed as bilateral adrenal hyperplasia (BAH), 37 as aldosterone-producing adenoma (APA), and 19 as unilateral adrenal hyperplasia (UAH). An ACTH stimulation test under 1 mg DST was performed in all patients. Plasma aldosterone and cortisol levels were measured every 30 minutes until 120 minutes after the iv injection of 50 IU ACTH. RESULTS During the ACTH stimulation test, aldosterone levels in APA and UAH were similar (P > .05) but higher than those in BAH (P < .001). Furthermore, stimulated aldosterone levels of unilateral PA (APA and UAH) were significantly higher than bilateral PA (BAH) (P < .001). Receiver-operated characteristics curve analyses showed the aldosterone after ACTH stimulation was effective for distinguishing between unilateral PA and bilateral PA. The diagnostic accuracy was highest at 120 minutes after ACTH stimulation, and the optimal cutoff value of the aldosterone was 77.90 ng/dL, with a sensitivity of 76.8%, a specificity of 87.2%, a positive predictive value of 89.6%, and a negative predictive value of 72.3%. CONCLUSIONS The ACTH stimulation test under 1 mg DST is useful to determine the subtypes of PA, especially in unilateral and bilateral PA, and may guide further treatment in PA patients.

Gene expression profiles of thymic neuroendocrine tumors (carcinoids) with ectopic ACTH syndrome reveal novel molecular mechanism

Although there has been increased knowledge about the molecular biology of neuroendocrine tumors (NETs), little is known about thymic carcinoids and even less about those with excessive hormone disorders, such as ectopic ACTH syndrome. This study was designed to gain insights into the molecular networks underlying the tumorigenesis of thymic carcinoids with ACTH secretion. By an approach integrating cDNA microarray and methods of computational biology, we compare gene expression profile between ACTH-producing thymic carcinoids and the normal thymus. In total, there are 63 biological categories increased and 108 decreased in thymic carcinoids. Cell proliferation was stimulated, which may explain the relatively uncontrolled cell growth of the tumor. Dysregulation of the Notch-signaling pathway was likely to be underlying the neuroendocrine features of this type of tumors. Moreover, inhibition of immunity and increased neuropeptide signaling molecules (POMC and its sorting molecule CPE) made the clinical manifestation reasonable and thus validated the array data. In conclusion, thymic carcinoids have a distinct gene expression pattern from the normal thymus, and they are characterized by deregulations of a series of biofunctions, which may be involved in the development of NETs. Hence, this study has provided not only a detailed comprehension of the molecular pathogenesis of thymic carcinoids with ectopic ACTH syndrome, but also a road map to approach thymic NETs at the system level.

Overexpression of ERBB-2 was more frequently detected in malignant than benign pheochromocytomas by multiplex ligation-dependent probe amplification and immunohistochemistry

To analyze the genetic alterations of pheochromocytomas and evaluate the difference among malignant, extra-adrenal, and benign pheochromocytomas. Forty-three tumor samples were tested for genetic changes using multiplex ligation-dependent probe amplification. Among them, 39 samples were available for protein expression analysis by immunohistochemistry (IHC). All 43 patients (24 women and 19 men; mean age 44.6±13.6 years; range 18–75 years; 9 with malignant, 7 extra-adrenal, and 27 benign) showed multiple copy number losses or gains. The average copy number change was 13.10 in malignant, 13.93 in benign, and 13.47 in paraganglioma patients. There is no significant difference among the three groups of pheochromocytomas. However, we discovered that in the malignant pheochromocytomas, 6 of the 9 patients (67%) showed erythroblastic leukemia viral oncogene homolog 2 (ERBB-2) oncogene gain, whereas only 12 of the 34 (35%) identified change in the benign and extra-adrenal pheochromocytomas. Further, IHC confirmed that ERBB-2-positive staining was more frequent and stronger in malignant pheochromocytomas than in benign and extra-adrenal pheochromocytomas. Our study illustrates the chromosomal changes of the whole genome of Chinese pheochromocytoma patients. The results suggest that there may be certain progression of genetic events that involves chromosomes 1p, 3p, 6p, 11q, 12q, 17q, and 19q in the development of pheochromocytomas, and the activation of ERBB-2 located on chromosome 17q is an important and early event in the malignancy development of these tumor types. The overexpression of ERBB-2 identified by IHC suggested that this oncogene could be associated with the malignancy of pheochromocytomas and paragangliomas.

Eosinophil inversely associates with type 2 diabetes and insulin resistance in Chinese adults.

Context Limited population-based study focused on relationship between eosinophil and type 2 diabetes (T2D). Objectives We aimed to evaluate the relationship between peripheral eosinophil percentage and glucose metabolism and insulin resistance in a large sample size of Chinese population aged 40 and older. Design and Methods A cross-sectional study was performed among 9,111 Chinese adults including 3,561 men and 5,550 women. The glucose metabolism status was confirmed by 75-g oral glucose tolerance test. Homeostasis model assessment of insulin resistance index and serum insulin levels were used to evaluate insulin resistance. Homeostasis model assessment-B was used to evaluate β cell function. Results The average age of participants was 58.5 years. The prevalence of T2D decreased across the tertiles of eosinophil percentage (21.3%, 18.2% and 16.9%, P<0.0001). Each one tertile increase of eosinophil percentage inversely associated with risk of T2D when referred not only to normal glucose tolerance (NGT) (odds ratio (OR) 0.81, 95% CI 0.76–0.87, P< 0.0001), but also to impaired glucose regulation (OR 0.89, 95% CI 0.83–0.97, P = 0.006), respectively, after adjustment for the confounding factors. Compared with the first tertile, the third tertile of eosinophil percentage associated with a 23% decrease of insulin resistance in NGT participants after full adjustments (P = 0.005). Each 1-standard deviation of increment of eosinophil percentage associated with a 37% decrease of insulin resistance (P = 0.005). Conclusions Higher peripheral eosinophil percentage was associated with decreased risk of T2D. The inverse relation to insulin resistance was detected in NGT participants.

Serum potassium level is associated with metabolic syndrome: A population-based study

BACKGROUND & AIMS Evidence has suggested that low serum potassium concentration or low dietary potassium intake can result in many metabolic disorders. Our objective was to evaluate the association between serum potassium level and risk of prevalent metabolic syndrome. METHODS We conducted a cross-sectional study in 10,341 participants aged 40 years or older. Metabolic syndrome was defined according to guidelines from the National Cholesterol Education Program with modification. RESULTS The prevalence rate of metabolic syndrome was 51.7% in participants with hypokalemia and 37.7% in those with normokalemia. With the reduction of serum potassium quartiles, participants were tended to have higher level of triglycerides and uric acid, lower level of high-density lipoprotein cholesterol (HDL-C), larger waist circumference and more severe insulin resistance. Serum potassium level significantly decreased with the increasing number of metabolic syndrome components. Compared with subjects in the highest quartile of serum potassium level, multivariate adjusted odds ratios for prevalent metabolic syndrome in the lowest quartile was 1.48 (95% confidence interval, 1.16-1.87). Moreover, compared with subjects without central obesity, hypertriglyceridemia, low HDL-C and elevated fasting plasma glucose, those with each of these metabolic syndrome components have lower level of serum potassium after adjusted for age and sex. CONCLUSIONS Low serum potassium level significantly associated with prevalence of metabolic syndrome in middle-aged and elderly Chinese.

Downregulation of miR-375 in aldosterone-producing adenomas promotes tumour cell growth via MTDH.

Previous studies have investigated the genetic and molecular basis of primary aldosteronism (PA), a common cause of human hypertension, but the effects of microRNAs (miRNAs) on the adrenocortical cell proliferation and aldosterone production are largely obscure. Here, we characterized miRNA expression patterns in the subtypes of PA to gain a better understanding of its pathogenesis.

Diagnosis and therapy for Cushing’s disease with negative dynamic MRI finding: a single-centre experience

Objective  Most patients with Cushing’s disease (CD) will have evidence of an adenoma on high‐resolution magnetic resonance imaging (MRI). However, a significant minority of patients with CD and biochemical hypercortisolaemia have no visible adenoma on MRI. The purpose of this study was to evaluate the diagnostic value of preoperative biochemical assessment and accuracy of MRI findings on surgical outcome.