Lack of sensitivity of diagnostic Cushing-scores in Germany: a multicenter validation

OBJECTIVE

Endogenous Cushing's syndrome (CS) is a severe condition, often diagnosed at a late stage. To reduce mortality, early diagnosis plays an important role. Two screening tools for early identification of patients with CS have been developed in multicentric cohorts, but have not yet been validated in cohorts with different geographic backgrounds.

DESIGN

We validated the Spanish score published by Leon-Justel et al. in 2016 and the Italian score by Parasiliti-Caprino et al. published in 2021 in our cohort.

METHODS

In the multicentric German Cushing registry, patients with confirmed and expected but ruled out Cushing's syndrome are prospectively diagnosed and followed up. We validated both scores in a cohort of 458 subjects: 176 patients with confirmed CS and 282 patients with suspected, but finally excluded CS.

RESULTS

Using the Spanish score, 17.5% of our patients with proven CS biochemical screening would not have been recommended. This concerned patients with pituitary CS (22%) and with adrenal CS (10%). On the contrary, only 14% of patients without CS would have received a recommendation for biochemical screening. Using the Italian score, 29% of patients with proven CS were classified into the low-risk classes not recommended for biochemical screening. This mostly affected patients with adrenal (31%) and pituitary CS (30%). About 12% of subjects without CS would have received a biochemical screening recommendation.

CONCLUSIONS

Both scores had limited sensitivity and high specificity in a German validation cohort. Further research is necessary to develop a screening score, which is effective in different healthcare systems and ethnicities.

Improved Diagnostic Accuracy of Clonidine Suppression Testing Using an Age-Related Cutoff for Plasma Normetanephrine

BACKGROUND

Moderately elevated plasma normetanephrine (NMN) levels are frequent among patients with suspected pheochromocytoma and paraganglioma (PPGL). Clonidine suppression testing (CST) is recommended to distinguish patients with from those without PPGL. We aimed at evaluating the diagnostic outcome of CST in patients with moderate NMN elevations.

METHODS

Data from patients participating in the PMT study (Prospective Monoamine-Producing Tumor) and the ENSAT (European Network for the Study of Adrenal Tumours) registry in 6 European reference centers were analyzed retrospectively. Eighty-nine patients with suspected PPGL and moderate NMN elevations upon screening were included. During follow-up, PPGL was confirmed in 16 and excluded in 73 cases. Plasma NMN was measured by liquid chromatography tandem mass spectrometry before and 180 minutes after oral clonidine. Receiver operating characteristic analysis was performed to identify optimal cutoffs.

RESULTS

If published diagnostic criteria for CST (ie, NMN ≥112 ng/L and NMN suppression <40%) were applied, a sensitivity of 88% (CI, 61%-98%) and a specificity of 97% (CI, 90%-100%) were observed. An improved cutoff for plasma NMN 180 minutes after clonidine was established at 80% of the age-related upper limit of normal, resulting in a sensitivity of 94% and a specificity of 97%. False-negative CST results occurred in 2 patients with small PPGL.

CONCLUSIONS

This study, involving one of the largest cohorts of patients with suspected PPGL and moderately elevated NMN, confirmed the diagnostic accuracy of CST. The application of an adapted cutoff further improved sensitivity.

Plasma Steroid Profiling in Patients With Adrenal Incidentaloma

CONTEXT

Most patients with adrenal incidentaloma have nonfunctional lesions that do not require treatment, while others have functional or malignant tumors that require intervention. The plasma steroid metabolome may be useful to assess therapeutic need.

OBJECTIVE

This work aimed to establish the utility of plasma steroid profiling combined with metanephrines and adrenal tumor size for the differential diagnosis of patients with adrenal incidentaloma.

METHODS

This retrospective cross-sectional study, which took place at 7 European tertiary-care centers, comprised 577 patients with adrenal incidentaloma, including 19, 77, 65, 104 and 312 respective patients with adrenocortical carcinoma (ACC), pheochromocytoma (PHEO), primary aldosteronism (PA), autonomous cortisol secretion (ACS), and nonfunctional adrenal incidentaloma (NFAI). Mesaures of diagnostic performance were assessed (with [95% CIs]) for discriminating different subgroups of patients with adrenal incidentaloma.

RESULTS

Patients with ACC were characterized by elevated plasma concentrations of 11-deoxycortisol, 11-deoxycorticosterone, 17-hydroxyprogesterone, androstenedione, and dehydroepiandrosterone-sulfate, whereas patients with PA had elevations of aldosterone, 18-oxocortisol, and 18-hydroxycortisol. A selection of those 8 steroids, combined with 3 others (cortisol, corticosterone, and dehydroepiandrosterone) and plasma metanephrines, proved optimal for identifying patients with ACC, PA, and PHEO at respective sensitivities of 83.3% (66.1%-100%), 90.8% (83.7%-97.8%), and 94.8% (89.8%-99.8%); and specificities of 98.0% (96.9%-99.2%), 92.0% (89.6%-94.3%), and 98.6% (97.6%-99.6%). With the addition of tumor size, discrimination improved further, particularly for ACC (100% [100%-100%] sensitivity, 99.5% [98.9%-100%] specificity). In contrast, discrimination of ACS and NFAI remained suboptimal (70%-71% sensitivity, 89%-90% specificity).

CONCLUSION

Among patients with adrenal incidentaloma, the combination of plasma steroid metabolomics with routinely available plasma free metanephrines and data from imaging studies may facilitate the identification of almost all clinically relevant adrenal tumors.

[Practical recommendations for screening and management of functional disorders of the adrenal cortex in cases of SARS-CoV-2 infections]

Diseases of the adrenal cortex require particular attention during the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic. Firstly, SARS-CoV‑2 infections can give rise to extrapulmonary manifestations and cause endocrine disorders, particularly in the adrenal cortex. Furthermore, patients with pre-existing insufficiency of the adrenal cortex or hypercortisonism are particularly at risk from a severe infection such as SARS-CoV‑2, to suffer from additional complications or a more severe course of a SARS-CoV‑2 infection with a higher mortality. Especially in hemodynamically unstable patients with a SARS-CoV‑2 infection, diseases of the adrenal glands should also be considered in the differential diagnostics and if necessary clarified, if this is not already known. Prolonged treatment of patients with a SARS-CoV‑2 infection with regimens containing high doses of glucocorticoids can also result in a secondary adrenal insufficiency. In order to address these special aspects, some practical recommendations for the diagnostic and therapeutic management of functional disorders of the adrenal glands in patients with a SARS-CoV‑2 infection are therefore presented.

Mass spectrometry-based steroid profiling in primary bilateral macronodular adrenocortical hyperplasia

Biochemical characterization of primary bilateral macronodular adrenocortical hyperplasia (PBMAH) by distinct plasma steroid profiles and its putative correlation to disease has not been previously studied. LC-MS/MS-based steroid profiling of 16 plasma steroids was applied to 36 subjects (22 females, 14 males) with PBMAH, 19 subjects (16 females, 3 males) with other forms of adrenal Cushing's syndrome (ACS), and an age and sex-matched control group. Germline ARMC5 sequencing was performed in all PBMAH cases. Compared to controls, PBMAH showed increased plasma 11-deoxycortisol, corticosterone, 11-deoxycorticosterone, 18-hydroxycortisol, and aldosterone, but lower progesterone, DHEA, and DHEA-S with distinct differences in subjects with and without pathogenic variants in ARMC5. Steroids that showed isolated differences included cortisol and 18-oxocortisol with higher (P < 0.05) concentrations in ACS than in controls and aldosterone with higher concentrations in PBMAH when compared to controls. Larger differences in PBMAH than with ACS were most clear for corticosterone, but there were also trends in this direction for 18-hydroxycortisol and aldosterone. Logistic regression analysis indicated four steroids - DHEA, 11-deoxycortisol, 18-oxocortisol, and corticosterone - with the most power for distinguishing the groups. Discriminant analyses with step-wise variable selection indicated correct classification of 95.2% of all subjects of the four groups using a panel of nine steroids; correct classification of subjects with and without germline variants in ARMC5 was achieved in 91.7% of subjects with PBMAH. Subjects with PBMAH show distinctive plasma steroid profiles that may offer a supplementary single-test alternative for screening purposes.

Plasma Steroid Profiles in Subclinical Compared With Overt Adrenal Cushing Syndrome

CONTEXT

Diagnosis of subclinical adrenal hypercortisolism is based on several tests of the hypothalamic-pituitary-adrenal axis to establish mild alterations of cortisol secretion and dysregulated cortisol physiology.

OBJECTIVE

We assessed whether plasma steroid profiles might assist diagnosis of subclinical Cushing syndrome (SC).

DESIGN

Retrospective cross-sectional study.

SETTING

Two tertiary medical centers.

PATIENTS

Of 208 patients tested for hypercortisolism, disease was excluded in 152 and confirmed in 21 with overt adrenal Cushing syndrome (AC) compared to 35 with SC. Another 277 age- and sex-matched hypertensive and normotensive volunteers were included for reference.

MAIN OUTCOME MEASURES

A panel of 15 plasma steroids was measured by mass spectrometry, with classification by discriminant analysis.

RESULTS

Patients with SC had lower plasma concentrations of dehydroepiandrosterone and dehydroepiandrosterone-sulfate than subjects without SC (P < 0.05). The largest increases (P < 0.001) in plasma steroids among patients with SC were observed for 11-deoxycortisol and 11-deoxycorticosterone. Nevertheless, concentrations of 11-deoxycorticosterone, 11-deoxycortisol, and pregnenolone in patients with AC were higher (P < 0.05) than in those with SC. Patients with SC or AC could be distinguished from subjects without disease using this combination of steroids as precisely as with use of measurements of serum cortisol after administration of dexamethasone. The steroid combination provided superior diagnostic performance compared with each of the other routine biochemical tests.

CONCLUSION

Distinct plasma steroid profiles in patients with SC may provide a simple and reliable screening method for establishing the diagnosis.

Pheochromocytoma and paraganglioma: clinical feature-based disease probability in relation to catecholamine biochemistry and reason for disease suspicion

OBJECTIVE

Hypertension and symptoms of catecholamine excess are features of pheochromocytomas and paragangliomas (PPGLs). This prospective observational cohort study assessed whether differences in presenting features in patients tested for PPGLs might assist establishing likelihood of disease.

DESIGN AND METHODS

Patients were tested for PPGLs because of signs and symptoms, an incidental mass on imaging or routine surveillance due to previous history or hereditary risk. Patients with (n = 245) compared to without (n = 1820) PPGLs were identified on follow-up. Differences in presenting features were then examined to assess the probability of disease and relationships to catecholamine excess.

RESULTS

Hyperhidrosis, palpitations, pallor, tremor and nausea were 30-90% more prevalent (P < 0.001) among patients with than without PPGLs, whereas headache, flushing and other symptoms showed little or no differences. Although heart rates were higher (P < 0.0001) in patients with than without PPGLs, blood pressures were not higher and were positively correlated to BMI, which was lower (P < 0.0001) in patients with than without PPGLs. From these differences in clinical features, a score system was established that indicated a 5.8-fold higher probability of PPGLs in patients with high than low scores. Higher scores among patients with PPGLs were associated, independently of tumor size, with higher biochemical indices of catecholamine excess.

CONCLUSIONS

This study identifies a complex of five signs and symptoms combined with lower BMI and elevated heart rate as key features in patients with PPGLs. Prevalences of these features, which reflect variable tumoral catecholamine production, may be used to triage patients according to likelihood of disease.

OR29-2 Mild Autonomous Cortisol Excess (MACE) in Adrenal Incidentalomas - Metabolic Risk Profile and Urinary Steroid Metabolome Analysis in 1208 Prospectively Recruited Patients

BACKGROUND: Adrenal incidentalomas (AI) are frequently associated with mild autonomous cortisol excess (MACE). The 1mg-dexamethasone suppression test (1mg-DST) differentiates MACE into MACE-1 (possible MACE; post-Dex cortisol 50-138 nmol/L) and MACE-2 (definitive MACE; post-Dex cortisol >138 nmol/L). MACE patients do not show clinically overt signs of hypercortisolism but are thought to carry a higher metabolic risk than nonfunctioning (NF) AIs. However, large-scale data about the metabolic impact of MACE are lacking. METHODS: We included 1208 patients with benign AIs and 1mg-DST results prospectively recruited as part of the ENSAT EURINE-ACT study. Clinical information and 24-h urines were available for all patients. Results of mass spectrometry-based urinary steroid profiling were compared to 162 healthy controls and 56 patients with overt adrenal Cushing’s syndrome (CUSH), using a sex- and age-adjusted linear regression model. RESULTS: MACE was found in 48% of adrenal incidentaloma patients (MACE-1 37%, MACE-2 11%), predominantly affecting women (NF 64%, MACE-1 67%, MACE-2 77%). MACE patients were significantly older than those with NF (p<0.001). MACE AIs were larger (median 32mm vs. 22mm in NF) and more often bilateral (31% vs. 17% in NF). The presence and grade of MACE were significantly linked to metabolic risk as assessed by prevalence of hypertension (NF 64%, MACE-1 75%, MACE-2 78%), type 2 diabetes (NF 20%, MACE-1 27%, MACE-2 30%), use of lipid-lowering medications (NF 40%, MACE-1 54%, MACE-2 52%), and osteopenia/osteoporosis (NF 37%, MACE-1 50%, MACE-2 56%) (all p<0.01 by Fisher’s exact test). Patients with MACE and type 2 diabetes more frequently required insulin treatment (31% vs. 15% in NF; p<0.01), and those with hypertension more often needed ≥3 medications (42% vs. 35% in NF; p<0.01). Urinary steroid metabolome analysis of MACE urines revealed a profile characterized by decreased androgen metabolites and increased glucocorticoid metabolites, resembling the profile of CUSH patients, with the latter also showing significantly increased mineralocorticoid precursor excretion (corticosterone and 11- deoxycorticosterone metabolites) (all p<0.001 vs. controls). CONCLUSIONS: MACE is highly prevalent in AIs and associated with an increased burden of metabolic co-morbidities. In addition, the similarities between the MACE and CUSH steroid metabolomes suggests that MACE is both a highly relevant clinical and biochemical entity.

OR02-6 Mass Spectrometry-Based Steroid Profiling Inprimary Bilateral Macronodular Adrenocortical Hyperplasia

Background: Biochemical characterization of primary bilateral macronodular adrenocortical hyperplasia (PBMAH) by distinct plasma steroid profiles and its putative correlation to disease has not been previously studied. Methods: LC-MS/MS-based steroid profiling of 16 plasma steroids was applied to 36 subjects (22 females, 14 males) with PBMAH, 19 subjects (16 females, 3 males) with other forms of adrenal CS (ACS), and an age and sex-matched control group. Germline ARMC5 sequencing was performed in all PBMAH cases. Results: The steroids showing the most dramatic differences between subject groups included 11-deoxycortisol, corticosterone, 11-deoxycorticosterone, 18-hydroxycortisol, progesterone and DHEA/DHEA-S. Steroids that showed isolated differences included cortisol and 18-oxocortisol with higher (P<0·05) concentrations in ACS than in controls, and aldosterone with higher concentrations in PBMAH when compared to controls. Larger differences in PBMAH than with ACS were most clear for corticosterone, but there were also trends in this direction for 18-hydroxycortisol and aldosterone. Logistic regression analysis indicated four steroids - DHEA, 11-deoxycortisol, 18-oxocortisol, and corticosterone - with the most power for distinguishing the groups. Discriminant analyses with step-wise variable selection indicated correct classification of 95·2% of all subjects of the four groups using a panel of nine steroids; correct classification of subjects with and without germline variants in ARMC5 was achieved in 91·7% of subjects with PBMAH. Conclusion: Subjects with PBMAH show distinctive plasma steroid profiles that may offer a supplementary single-test alternative for screening purposes.

Reference intervals for LC-MS/MS measurements of plasma free, urinary free and urinary acid-hydrolyzed deconjugated normetanephrine, metanephrine and methoxytyramine

BACKGROUND

Plasma or urinary metanephrines are recommended for screening of pheochromocytomas and paragangliomas (PPGLs). Measurements of urinary free rather than deconjugated metanephrines and additional measurements of methoxytyramine represent other developments. For all measurements there is need for reference intervals.

METHODS

Plasma free, urinary free and urinary deconjugated O-methylated catecholamine metabolites were measured by LC-MS/MS in specimens from 590 hypertensives and normotensives. Reference intervals were optimized using data from 2,056 patients tested for PPGLs.

RESULTS

Multivariate analyses, correcting for age and body surface area, indicated higher plasma and urinary metanephrine in males than females and sex differences in urinary normetanephrine and free methoxytyramine that largely reflected body size variation. There were positive associations of age with plasma metabolites, but negative relationships with urinary free metanephrine and methoxytyramine. Plasma and urinary normetanephrine were higher in hypertensives than normotensives, but differences were small. Optimization of reference intervals using the data from patients tested for PPGLs indicated that age was the most important consideration for plasma normetanephrine and sex most practical for urinary metabolites.

CONCLUSION

This study clarifies impacts of demographic and anthropometric variables on catecholamine metabolites, verifies use of age-specific reference intervals for plasma normetanephrine and establishes sex-specific reference intervals for urinary metabolites.

Biochemical Diagnosis of Chromaffin Cell Tumors in Patients at High and Low Risk of Disease: Plasma versus Urinary Free or Deconjugated O-Methylated Catecholamine Metabolites

BACKGROUND

Measurements of plasma or urinary metanephrines are recommended for diagnosis of pheochromocytoma and paraganglioma (PPGL). What test offers optimal diagnostic accuracy for patients at high and low risk of disease, whether urinary free metanephrines offer advantages over deconjugated metanephrines, and what advantages are offered by including methoxytyramine in panels all remain unclear.

METHODS

A population of 2056 patients with suspected PPGLs underwent prospective screening for disease using mass spectrometric-based measurements of plasma free, urinary deconjugated, and urinary free metanephrines and methoxytyramine. PPGLs were confirmed in 236 patients and were excluded in others on follow-up evaluation.

RESULTS

Measurements of plasma free metabolites offered higher (P &lt; 0.01) diagnostic sensitivity (97.9%) than urinary free (93.4%) and deconjugated (92.9%) metabolites at identical specificities for plasma and urinary free metabolites (94.2%) but at a lower (P &lt; 0.005) specificity for deconjugated metabolites (92.1%). The addition of methoxytyramine offered little value for urinary panels but provided higher (P &lt; 0.005) diagnostic performance for plasma measurements than either urinary panel according to areas under ROC curves (0.991 vs 0.972 and 0.964). Diagnostic performance of urinary and plasma tests was similar for patients at low risk of disease, whereas plasma measurements were superior to both urinary panels for high-risk patients.

CONCLUSIONS

Diagnosis of PPGLs using plasma or urinary free metabolites provides advantages of fewer false-positive results compared with commonly measured deconjugated metabolites. The plasma panel offers better diagnostic performance than either urinary panel for patients at high risk of disease and, with appropriate preanalytics, provides the test of choice. Measurements of methoxytyramine in urine show limited diagnostic utility compared with plasma.

Streptozotocin-induced β-cell damage, high fat diet, and metformin administration regulate Hes3 expression in the adult mouse brain

Diabetes mellitus is a group of disorders characterized by prolonged high levels of circulating blood glucose. Type 1 diabetes is caused by decreased insulin production in the pancreas whereas type 2 diabetes may develop due to obesity and lack of exercise; it begins with insulin resistance whereby cells fail to respond properly to insulin and it may also progress to decreased insulin levels. The brain is an important target for insulin, and there is great interest in understanding how diabetes affects the brain. In addition to the direct effects of insulin on the brain, diabetes may also impact the brain through modulation of the inflammatory system. Here we investigate how perturbation of circulating insulin levels affects the expression of Hes3, a transcription factor expressed in neural stem and progenitor cells that is involved in tissue regeneration. Our data show that streptozotocin-induced β-cell damage, high fat diet, as well as metformin, a common type 2 diabetes medication, regulate Hes3 levels in the brain. This work suggests that Hes3 is a valuable biomarker helping to monitor the state of endogenous neural stem and progenitor cells in the context of diabetes mellitus.

Adrenomedullary function, obesity and permissive influences of catecholamines on body mass in patients with chromaffin cell tumours

BACKGROUND

Obesity-associated activation of sympathetic nervous outflow is well documented, whereas involvement of dysregulated adrenomedullary hormonal function in obesity is less clear. This study assessed relationships of sympathoadrenal function with indices of obesity and influences of circulating catecholamines on body mass.

METHODS

Anthropometric and clinical data along with plasma and 24-h urine samples were collected from 590 volunteers and 1368 patients tested for phaeochromocytoma and paraganglioma (PPGL), among whom tumours were diagnosed in 210 individuals.

RESULTS

Among patients tested for PPGL, those with tumours less often had a body mass index (BMI) above 30 kg/m² (12 vs. 31%) and more often a BMI under 25 kg/m² (56 vs. 32%) than those without tumours (P < 0.0001). Urinary outputs of catecholamines in patients with PPGL were negatively related to BMI (r = -0.175, P = 0.0133). Post-operative weight gain (P < 0.0001) after resection of PPGL was positively related to presurgical tumoural catecholamine output (r = 0.257, P = 0.0101). Higher BMI in men and women and percent body fat in women of the volunteer group were associated with lower plasma concentrations and urinary outputs of adrenaline and metanephrine, the former indicating obesity-related reduced adrenaline secretion and the latter obesity-related reduced adrenomedullary adrenaline stores. Daytime activity was associated with substantial increases in urinary adrenaline and noradrenaline excretion, with blunted responses in obese subjects.

CONCLUSIONS

The findings in patients with PPGL support an influence of high circulating catecholamines on body weight. Additional associations of adrenomedullary dysfunction with obesity raise the possibility of a permissive influence of the adrenal medulla on the regulation of body weight.

Hypertensive crisis in pregnancy due to a metamorphosing pheochromocytoma with postdelivery Cushing's syndrome

Pheochromocytomas in pregnancy are rare but potentially lethal. Even rarer is the combination of pheochromocytoma in pregnancy with subsequent development of ectopic Cushing's syndrome. We report a 36-year-old woman, previously diagnosed with essential hypertension, who developed severe hypertension in pregnancy complicated by insulin-dependent gestational diabetes. A cesarean section was performed at 32 weeks following a hypertensive crisis after routine administration of betamethasone. Postnatal persistence of signs and symptoms of catecholamine excess led to the diagnosis of a left adrenal pheochromocytoma. Between diagnosis and planned tumor removal, the patient developed signs and symptoms of Cushing's syndrome (facial edema and hirsutism, myopathy and fatigue). Biochemical testing confirmed hypercortisolism with extremely elevated levels of plasma adrenocorticotropin, urinary cortisol and multiple steroids of a plasma panel that were all normal at previous testing. The previously noradrenergic tumor also started producing epinephrine. Histopathological examination confirmed the pheochromocytoma, which was also immunohistochemically positive for adrenocorticotropin. Full post-surgical recovery was sustained with normal blood pressure and biochemical findings after one year. This report not only underlines the chameleon behavior of pheochromocytoma but also illustrates its potential for a metamorphosing presentation. Corticosteroid administration in pregnancy requires a cautious approach in patients with hypertension.

Plasma Steroid Metabolome Profiling for Diagnosis and Subtyping Patients with Cushing Syndrome

BACKGROUND

Diagnosis of Cushing syndrome requires a multistep process that includes verification of hypercortisolism followed by identification of the cause of adrenocortical hyperfunction. This study assessed whether pituitary, ectopic, and adrenal subtypes of Cushing syndrome were characterized by distinct plasma steroid profiles that might assist diagnosis.

METHODS

In this retrospective cross-sectional study, mass spectrometric measurements of a panel of 15 plasma steroids were applied to 222 patient samples tested for Cushing syndrome. Disease was excluded in 138 and confirmed in 51 patients with pituitary Cushing syndrome, 12 with ectopic adrenocorticotropin secretion, and 21 with adrenal disease. Another 277 age- and sex-matched hypertensive and normotensive volunteers were included for comparison.

RESULTS

Compared with patients without disease, the largest increases in plasma steroids among patients with Cushing syndrome were observed for 11-deoxycortisol (289%), 21-deoxycortisol (150%), 11-deoxycorticosterone (133%), corticosterone (124%), and cortisol (122%). Patients with ectopic disease showed the most prominent increases, but there was considerable variation for other steroids according to subtype. Patients with adrenal disease had the lowest concentrations of androgens, whereas those with ectopic and pituitary disease showed the lowest concentrations of aldosterone. Plasma 18-oxocortisol was particularly low in ectopic disease. With the use of 10 selected steroids, subjects with and without different Cushing syndrome subtypes could be discriminated nearly as closely as with the use of salivary and urinary free cortisol, dexamethasone-suppressed cortisol, and plasma adrenocorticotropin (9.5% vs 5.8% misclassification).

CONCLUSIONS

Patients with different subtypes of Cushing syndrome show distinctive plasma steroid profiles that may offer a supplementary single-test alternative for screening purposes.

Endocrine Pancreas Development and Regeneration: Noncanonical Ideas From Neural Stem Cell Biology

Loss of insulin-producing pancreatic islet β-cells is a hallmark of type 1 diabetes. Several experimental paradigms demonstrate that these cells can, in principle, be regenerated from multiple endogenous sources using signaling pathways that are also used during pancreas development. A thorough understanding of these pathways will provide improved opportunities for therapeutic intervention. It is now appreciated that signaling pathways should not be seen as "on" or "off" but that the degree of activity may result in wildly different cellular outcomes. In addition to the degree of operation of a signaling pathway, noncanonical branches also play important roles. Thus, a pathway, once considered as "off" or "low" may actually be highly operational but may be using noncanonical branches. Such branches are only now revealing themselves as new tools to assay them are being generated. A formidable source of noncanonical signal transduction concepts is neural stem cells because these cells appear to have acquired unusual signaling interpretations to allow them to maintain their unique dual properties (self-renewal and multipotency). We discuss how such findings from the neural field can provide a blueprint for the identification of new molecular mechanisms regulating pancreatic biology, with a focus on Notch, Hes/Hey, and hedgehog pathways.

STAT3-Ser/Hes3 Signaling: A New Molecular Component of the Neuroendocrine System?

The endocrine system involves communication among different tissues in distinct organs, including the pancreas and components of the Hypothalamic-Pituitary-Adrenal Axis. The molecular mechanisms underlying these complex interactions are a subject of intense study as they may hold clues for the progression and treatment of a variety of metabolic and degenerative diseases. A plethora of signaling pathways, activated by hormones and other endocrine factors have been implicated in this communication. Recent advances in the stem cell field introduce a new level of complexity: adult progenitor cells appear to utilize distinct signaling pathways than the more mature cells in the tissue they co-reside. It is therefore important to elucidate the signal transduction requirements of adult progenitor cells in addition to those of mature cells. Recent evidence suggests that a common non-canonical signaling pathway regulates adult progenitors in several different tissues, rendering it as a potentially valuable starting point to explore their biology. The STAT3-Ser/Hes3 Signaling Axis was first identified as a major regulator of neural stem cells and, subsequently, cancer stem cells. In the endocrine/neuroendocrine system, this pathway operates on several levels, regulating other types of plastic cells: (a) it regulates pancreatic islet cell function and insulin release; (b) insulin in turn activates the pathway in broadly distributed neural progenitors and possibly also hypothalamic tanycytes, cells with important roles in the control of the adrenal gland; (c) adrenal progenitors themselves operate this pathway. The STAT3-Ser/Hes3 Signaling Axis therefore deserves additional research in the context of endocrinology.

Concise Review: Reprogramming, Behind the Scenes: Noncanonical Neural Stem Cell Signaling Pathways Reveal New, Unseen Regulators of Tissue Plasticity With Therapeutic Implications

Interest is great in the new molecular concepts that explain, at the level of signal transduction, the process of reprogramming. Usually, transcription factors with developmental importance are used, but these approaches give limited information on the signaling networks involved, which could reveal new therapeutic opportunities. Recent findings involving reprogramming by genetic means and soluble factors with well-studied downstream signaling mechanisms, including signal transducer and activator of transcription 3 (STAT3) and hairy and enhancer of split 3 (Hes3), shed new light into the molecular mechanisms that might be involved. We examine the appropriateness of common culture systems and their ability to reveal unusual (noncanonical) signal transduction pathways that actually operate in vivo. We then discuss such novel pathways and their importance in various plastic cell types, culminating in their emerging roles in reprogramming mechanisms. We also discuss a number of reprogramming paradigms (mouse induced pluripotent stem cells, direct conversion to neural stem cells, and in vivo conversion of acinar cells to β-like cells). Specifically for acinar-to-β-cell reprogramming paradigms, we discuss the common view of the underlying mechanism (involving the Janus kinase-STAT pathway that leads to STAT3-tyrosine phosphorylation) and present alternative interpretations that implicate STAT3-serine phosphorylation alone or serine and tyrosine phosphorylation occurring in sequential order. The implications for drug design and therapy are important given that different phosphorylation sites on STAT3 intercept different signaling pathways. We introduce a new molecular perspective in the field of reprogramming with broad implications in basic, biotechnological, and translational research.

SIGNIFICANCE

Reprogramming is a powerful approach to change cell identity, with implications in both basic and applied biology. Most efforts involve the forced expression of key transcription factors, but recently, success has been reported with manipulating signal transduction pathways that might intercept them. It is important to start connecting the function of the classic reprogramming genes to signaling pathways that also mediate reprogramming, unifying the sciences of signal transduction, stem cell biology, and epigenetics. Neural stem cell studies have revealed the operation of noncanonical signaling pathways that are now appreciated to also operate during reprogramming, offering new mechanistic explanations.

Hes3 is expressed in the adult pancreatic islet and regulates gene expression, cell growth, and insulin release

The transcription factor Hes3 is a component of a signaling pathway that supports the growth of neural stem cells with profound consequences in neurodegenerative disease models. Here we explored whether Hes3 also regulates pancreatic islet cells. We showed that Hes3 is expressed in human and rodent pancreatic islets. In mouse islets it co-localizes with alpha and beta cell markers. We employed the mouse insulinoma cell line MIN6 to perform in vitro characterization and functional studies in conditions known to modulate Hes3 based upon our previous work using neural stem cell cultures. In these conditions, cells showed elevated Hes3 expression and nuclear localization, grew efficiently, and showed higher evoked insulin release responses, compared with serum-containing conditions. They also exhibited higher expression of the transcription factor Pdx1 and insulin. Furthermore, they were responsive to pharmacological treatments with the GLP-1 analog Exendin-4, which increased nuclear Hes3 localization. We employed a transfection approach to address specific functions of Hes3. Hes3 RNA interference opposed cell growth and affected gene expression as revealed by DNA microarrays. Western blotting and PCR approaches specifically showed that Hes3 RNA interference opposes the expression of Pdx1 and insulin. Hes3 overexpression (using a Hes3-GFP fusion construct) confirmed a role of Hes3 in regulating Pdx1 expression. Hes3 RNA interference reduced evoked insulin release. Mice lacking Hes3 exhibited increased islet damage by streptozotocin. These data suggest roles of Hes3 in pancreatic islet function.

A defined, controlled culture system for primary bovine chromaffin progenitors reveals novel biomarkers and modulators

We present a method to efficiently culture primary chromaffin progenitors from the adult bovine adrenal medulla in a defined, serum-free monolayer system. Tissue is dissociated and plated for expansion under support by the mitogen basic fibroblast growth factor (bFGF). The cultures, although not homogenous, contain a subpopulation of cells expressing the neural stem cell marker Hes3 that also propagate. In addition, Hes3 is also expressed in the adult adrenal medulla from where the tissue is taken. Differentiation is induced by bFGF withdrawal and switching to Neurobasal medium containing B27. Following differentiation, Hes3 expression is lost, and cells acquire morphologies and biomarker expression patterns of chromaffin cells and dopaminergic neurons. We tested the effect of different treatments that we previously showed regulate Hes3 expression and cell number in cultures of fetal and adult rodent neural stem cells. Treatment of the cultures with a combination of Delta4, Angiopoietin2, and a Janus kinase inhibitor increases cell number during the expansion phase without significantly affecting catecholamine content levels. Treatment with cholera toxin does not significantly affect cell number but reduces the ratio of epinephrine to norepinephrine content and increases the dopamine content relative to total catecholamines. These data suggest that this defined culture system can be used for target identification in drug discovery programs and that the transcription factor Hes3 may serve as a new biomarker of putative adrenomedullary chromaffin progenitor cells.

Neurovascular signals suggest a propagation mechanism for endogenous stem cell activation along blood vessels

Stem cell – based therapies for central nervous system disorders are intensely pursued. Such approaches can be divided into two categories: Transplantation-based, and those that aim to pharmacologically target the endogenous stem cell population in the tissue. Endogenous stem cell – based strategies avoid the problem of immune incompatibility between the host and the grafted cells. They also avoid the placement of a large amount of cells in confined areas, a manipulation which alters the characteristics of the neurovascular microenvironment. We show here that massive pharmacological activation (increase in cell numbers) of the endogenous neural stem cell population in the adult rodent brain maintains the cytoarchitecture of the neurovascular niche. Distances between adjacent stem cells (identified by expression of Hes3) are maintained above a minimum. Hes3+ cells maintain their physical association with blood vessels. These results also suggest a mechanism by which the activation signal from the lateral ventricle can be propagated to areas a long distance away from the lateral ventricles, through autocrine/paracrine actions between adjacent Hes3+ cells, along blood vessels. Finally, powerful effects of angiopoietin 2 on Hes3+ cells help explain the prevalence of proliferating endogenous neural stem cells close to the subventricular zone (an area of high angiopoietin 2 concentration) and the quiescent state of stem cells away from the ventricles and their tight physical association with blood vessels (which express high levels of angiopoietin 1, a cytokine that opposes angiopoietin 2 functions).

PTBP1 is required for embryonic development before gastrulation

Polypyrimidine-tract binding protein 1 (PTBP1) is an important cellular regulator of messenger RNAs influencing the alternative splicing profile of a cell as well as its mRNA stability, location and translation. In addition, it is diverted by some viruses to facilitate their replication. Here, we used a novel PTBP1 knockout mouse to analyse the tissue expression pattern of PTBP1 as well as the effect of its complete removal during development. We found evidence of strong PTBP1 expression in embryonic stem cells and throughout embryonic development, especially in the developing brain and spinal cord, the olfactory and auditory systems, the heart, the liver, the kidney, the brown fat and cartilage primordia. This widespread distribution points towards a role of PTBP1 during embryonic development. Homozygous offspring, identified by PCR and immunofluorescence, were able to implant but were arrested or retarded in growth. At day 7.5 of embryonic development (E7.5) the null mutants were about 5x smaller than the control littermates and the gap in body size widened with time. At mid-gestation, all homozygous embryos were resorbed/degraded. No homozygous mice were genotyped at E12 and the age of weaning. Embryos lacking PTBP1 did not display differentiation into the 3 germ layers and cavitation of the epiblast, which are hallmarks of gastrulation. In addition, homozygous mutants displayed malformed ectoplacental cones and yolk sacs, both early supportive structure of the embryo proper. We conclude that PTBP1 is not required for the earliest isovolumetric divisions and differentiation steps of the zygote up to the formation of the blastocyst. However, further post-implantation development requires PTBP1 and stalls in homozygous null animals with a phenotype of dramatically reduced size and aberration in embryonic and extra-embryonic structures.

Tamoxifen-independent recombination in the RIP-CreER mouse

BACKGROUND

The inducible Cre-lox system is a valuable tool to study gene function in a spatial and time restricted fashion in mouse models. This strategy relies on the limited background activity of the modified Cre recombinase (CreER) in the absence of its inducer, the competitive estrogen receptor ligand, tamoxifen. The RIP-CreER mouse (Tg (Ins2-cre/Esr1) 1Dam) is among the few available β-cell specific CreER mouse lines and thus it has been often used to manipulate gene expression in the insulin-producing cells of the endocrine pancreas.

PRINCIPAL FINDINGS

Here, we report the detection of tamoxifen-independent Cre activity as early as 2 months of age in RIP-CreER mice crossed with three distinct reporter strains.

SIGNIFICANCE

Evidence of Cre-mediated recombination of floxed alleles even in the absence of tamoxifen administration should warrant cautious use of this mouse for the study of pancreatic β-cells.