Study of the involvement of pancreastatin in the physiopathology of diabetes mellitus associated with nonsecreting pituitary adenomas

Pancreastatin, derived from chromogranin A, inhibits insulin and stimulates glucagon secretion in rodents. Immunohistochemistry localised pancreastatin in human pancreatic islet cells and gonadotroph pituitary cells. Nonsecreting pituitary adenomas, frequently associated with diabetes mellitus, arise quasi-constantly from gonadotroph cells. We evaluated the possible involvement of pancreastatin in the physiopathology of diabetes mellitus associated with nonsecreting pituitary adenomas. Plasma pancreastatin levels were measured by radioimmunoassay in 5 groups of subjects: 10 patients with nonsecreting pituitary adenomas associated with diabetes mellitus (group I), 10 patients with nonsecreting pituitary adenomas without diabetes (Group II), 10 patients with ACTH or GH-secreting pituitary adenomas and diabetes mellitus (Group III), 10 diabetic patients without pituitary adenomas (Group IV), and 10 healthy controls (Group V). Kidney and liver functions were normal in all of them and no patient was treated with a proton pump inhibitor. All pituitary adenomas were trans-sphenoidally removed. Immunohistochemistry against pancreastatin was performed in 5 patients of each of the 3 groups of pituitary adenomas. Plasma pancreastatin levels were not different between the different groups: 182±46 pg/ml (Group I), 195±57 pg/ml (Group II), 239±42 pg/ml (Group III), 134±31 pg/ml, (Group IV), and 122±29 pg/ml (Group V). In contrast, they were significantly (p<0.05) higher before (391±65 pg/ml) than after trans-sphenoidal surgery (149±18 pg/ml) without post-surgical change in diabetes. An immunostaining against pancreastatin was found in a majority of pituitary adenomas, associated or not with diabetes mellitus. These results argue against a role of pancreastatin in the pathogenesis of diabetes mellitus associated with nonsecreting pituitary adenomas.

Ectopic expression of serotonin7 receptors in an adrenocortical carcinoma co-secreting renin and cortisol

Abnormal expression of membrane receptors has been previously described in benign adrenocortical neoplasms causing Cushing's syndrome. In particular, we have observed that, in some adreno corticotropic hormone (ACTH)-independent macronodular adrenal hyperplasia tissues, cortisol secretion is controlled by ectopic serotonin(7) (5-HT(7)) receptors. The objective of the present study was to investigate in vitro the effect of serotonin (5-hydroxy tryptamine; 5-HT) on cortisol and renin production by a left adrenocortical carcinoma removed from a 48-year-old female patient with severe Cushing's syndrome and elevated plasma renin levels. Tumor explants were obtained at surgery and processed for immunohistochemistry, in situ hybridization and cell culture studies. 5-HT-like immunoreactivity was observed in mast cells and steroidogenic cells disseminated in the tissue. 5-HT stimulated cortisol release by cultured cells. The stimulatory effect of 5-HT on cortisol secretion was suppressed by the 5-HT(7) receptor antagonist SB269970. In addition, immunohistochemistry showed the occurrence of 5-HT(7) receptor-like immunoreactivity in carcinoma cells. mRNAs encoding renin as well as renin-like immunoreactivity were detected in endothelial and tumor cells. Cell incubation studies revealed that the adrenocortical tissue also released renin. Renin production was inhibited by 5-HT but was not influenced by ACTH and angiotensin II (Ang II). In conclusion, the present report provides the first demonstration of ectopic serotonin receptors, i.e. 5-HT(7) receptors, in an adrenocortical carcinoma. Our results also indicate that 5-HT can influence the secretory activity of malignant adrenocortical tumors in an autocrine/paracrine manner. The effects of 5-HT on adrenocortical tumor cells included a paradoxical inhibitory action on renin production and a stimulatory action on cortisol secretion involving 5-HT(7) receptors.

Simultaneous suprasellar and pineal germ cell tumors in five late stage adolescents: endocrinological studies and prolonged follow-up

Primary germ cell tumors (PGCT) of the central nervous system usually develop in the third ventricle area, and most frequently in the pineal region. The suprasellar region is the second preferential site for development of these tumors which are rarely simultaneously present in these two sites. We report five new cases of PGCT with pineal and suprasellar localizations, which appeared in late puberty in four boys and one girl aged 17-19 years. The clinical picture associated signs of intracranial hypertension, convergence and verticality palsies, diabetes insipidus and pituitary deficiency. Encephalic MRI revealed a double localization. Endocrine tests revealed a particular pattern associating central diabetes insipidus and a hypothalamic-pituitary disconnection syndrome. Following identification of the pathological type of lesions via a neurosurgical approach, treatment was based on a combined method using chemotherapy, radiotherapy and hormone replacement. Based on this treatment, prolonged remissions were obtained with a good quality of life.

Two-year stability of NT-proBNP in frozen samples using the Roche Elecsys system

Background

The in vitro stability of N-terminal (NT)-proBNP (brain natriuretic peptide) at room temperature and at 4°C is excellent and has been well studied. However, less is known concerning its stability after a long-term frozen storage. This notion could be of major interest in the context of clinical evaluations.

Methods

NT-proBNP was measured on 97 heparinized samples before and after a two-year frozen storage (−20°C) using the Roche Elecsys system.

Results

There is a slight but significant decrease of NT-proBNP concentration after frozen storage. However, this decrease is <10% for more than 90% of the samples and the maximum decrease is 16%. Moreover, values on frozen samples are well correlated with values on fresh samples ( r = 0.99) using the following equation: NT-proBNPstored sample = 0.93 NT-proBNPfresh sample + 81. A similar equation was found in lower concentrations (NT-proBNP ≤ 2000 ng/L).

Conclusions

These data show that NT-proBNP can be stored for at least two years at −20°C before measurement without a substantial loss of immunoreactivity.

[NT-proBNP measurement on Immulite 2500 (DPC): analytical performance and comparison with Roche Diagnostics and Dade-Behring NT-proBNP immunoassays]

The measurement of the N-terminal part of the proBNP (NT-proBNP) may be used to assess the secretion of the B-type natriuretic peptide (BNP), a marker of heart failure. In this study, we have evaluated the NT-proBNP immunoassay proposed by DPC Company for the Immulite 2500 analyzer and compared the results with those obtained with the two other immunoassays respectively commercialized by Roche Diagnostics (Elecsys 2010 analyzer) and Dade-Behring (Dimension RXL). The obtained results show very good general performance of the DPC's technique with a CV inferior to 8% for the values superior to 40 ng/L. The within run CVs are 3.1, 3.5 and 3.5% and the between run CVs are 3.8, 4.7 and 4.8% for the NT-proBNP levels of 151, 1601 and 5255 ng/L, respectively. We found a very good correlation between DPC's and Roche Diagnostics's assays (regression analysis: y = 0.88 x + 25.2 ; r = 0.998) and DPC's and Dade-Behring assays (regression analysis: y = 0.93 x + 16.4 ; r = 0.997). Although a small bias appeared between these assays, similar cut-points may be used to exclude both heart failure in ambulatory patients and cardiac origin in acute dyspnea.

[Macromolecular complex of cardiac troponin I: differences of reactivity with DPC and Dade-Behring assays]

We have recently identified a macromolecular 440-kDa cardiac troponin I (cTnI) complex after successful percutaneous transluminal coronary angioplasty (PTCA) (Clin Chem 2003; 49: 505-7). The aim of the work was to confirm the existence of such a complex by using another cTnI assay (Dimension RXL, Dade-Behring). We have first studied the correlation between the two assays by using heparinized samples [cTnI(Immulite) = 2.00 cTnI(Dimension) - 0.01 (n = 176; r = 0,987)]. Then, cTnI taken 120 minutes after PTCA for two patients was measured with the two assays after fractionation by FPLC. The obtained results confirmed the existence of the 440-kDa cTnI complex and showed that the reactivity between the assays (DPC/Dade-Behring ratio) depended on the nature of the complex: the ratio increased from 0.7 (440-kDa cTnI complex) to 3 (80-kDa cTnI complex) therefore suggesting caution in the comparison between the different cTnI assays in the context of reperfusion therapy.

[Brain natriuretic peptide: physiological, biological and clinical aspects]

Brain natriuretic peptide is one member of the natriuretic peptide family, including also ANP, CNP, DNP and urodilatin. In human, brain natriuretic peptide is mainly secreted by the cardiac ventricles. BNP is synthetized as pre-proBNP form, secondary cleaved in proBNP, itself equimolarly cleaved in BNP and NT-proBNP. The biological action of BNP is mediated by the NPR-A receptor. This peptide is eliminated from the systemic circulation by a neutral endopeptidase and by a clearance receptor (NPR-C). The BNP and NT-proBNP concentrations are measured using automated rapid immunoassay techniques. Plasma concentrations of the two peptides physiologically increase with age and are found to be higher in women than in men. The action of BNP against fluid expansion is explained by its vascular (vasodilatation), renal (diuretic and natriuretic) and cerebral activities. The measurement of these two peptides contributes to the diagnosis of heart failure. These peptides are prognostic markers both in heart failure and in acute coronary syndromes. In renal insufficiency, the interpretation of the increase in these two peptide concentrations may be difficult, particularly with the NT-proBNP which is mainly excreted by the kidneys.

[Cardiac troponin I and T: specific biomarkers of cardiomyocyte]

PURPOSE

Cardiac troponin I and troponin T have replaced creatine kinase MB (CK-MB) for the diagnosis of cardiomyocyte necrosis. Cardiac specificity of these new markers leads to a change in our practice.

CURRENT KNOWLEDGE AND KEY POINTS

Following necrosis, intracellular proteins are released into blood. This easy concept overlaps a biological complexity since troponins are released as complexes leading to various cut-off values depending on the assay used, as least for cardiac troponin I. The increase in both specificity and analytical sensitivity of these markers reached to propose a new definition of myocardial infarction. The diagnosis of acute coronary syndrome is a clinical based diagnosis, the use of troponin contributing to their classification. Finally, pathological processes leading to cardiac injury may induce an increase in the cardiac troponin level.

FUTURE PROSPECTS AND PROJECTS

Troponin standardization is a challenge for the near future leading to better follow-up of patients and comparison between cohorts.

[Cardiac troponin I and CK-MB mass after cardiac surgery with cardiopulmonary bypass]

Cardiac troponin I (cTnI) assay is used in the diagnosis of myocardial infarction after cardiac surgery. Variations in the cut-off value have been reported even with the same assay method. The aim of this work is to investigate the release profile of cTnI and CK-MB mass after cardiac surgery and to determine the cut-off value of cTnI and CK-MB mass allowing the diagnosis of perioperative myocardial infarction. In patients without postoperative cardiac complication, the cTnI peak was observed 24 hours after surgery both in coronary artery bypass grafting and in valve replacement. Moreover, the amount of cTnI released within the three hours after surgery is 2.5 fold higher in valve replacement than in coronary artery bypass grafting. The CK-MB peak was observed 3 hours after surgery in the two surgical procedures. In these patients, cTnI and CK-MB concentrations increased with the cross clamp time duration. In patients with postoperative myocardial infarction, the cTnI and CK-MB peaks were observed 24 hours after surgery. Diagnosis of perioperative myocardial infarction can be performed with a sensitivity of 100% at 24 hours with cut-off values of 32 and 7 microg/L for CK-MB and cTnI, respectively, both with Stratus (Dade Behring) and Immulite (DPC) analysers.

Evidence for nasal carriage of methicillin-resistant staphylococci colonizing intravascular devices

Nasal surveillance cultures were performed for 54 patients exhibiting >/=10(3) CFU of methicillin-resistant coagulase-negative staphylococci per ml in central venous catheter (CVC) rinse cultures over a 6-month period. Forty-two of the nasal cultures yielded growth of methicillin-resistant coagulase-negative staphylococci, and 33 of the 42 cultures contained organisms that belonged to the same species as the CVC isolates. Of the 33 same-species isolates, 20 appeared to be identical strains by pulsed-field gel electrophoresis analysis. These data suggest that measures should be taken to reduce cross-contamination between the respiratory tract and intravascular devices. However, the potential interest in detecting methicillin-resistant coagulase-negative staphylococcus carriage in high-risk patients is hampered by the lack of sensitivity of nasal surveillance cultures.

[Assay of cardiac troponin T on Elecsys 2010: comparison with cardiac troponin I]

Cardiac troponin T (troponin Tc) of second generation has been measured on the Boehringer Elecsys 2010 analyzer. Cardiac specificity has been studied in patients presenting a rhabdomyolysis syndrome and the results compared with those obtained for cardiac troponin I (troponin Ic) measured on the Dade-Behring Stratus analyzer. The results clearly demonstrated that both troponin Tc and Ic showed similar cardiac specificity. Moreover, troponin Tc and troponin Ic can be indifferently used for the biological diagnostic of myocardial infarction or to asses reperfusion after percutaneous transluminal coronary angioplasty for acute myocardial infarction. In renal disease, troponin Tc was upper the reference limit (0.10 microgram/l) in 25% of the patients studied (20 patients). By contrast, troponin Ic was upper the reference limit (0.6 microgram/l) in only one patient.

[Determination of cardiac troponin I on Stratus analyzer: prospective evaluation in unstable angina]

Cardiac troponin I (troponin lc) has been measured on the Dade Stratus analyzer. Cardiac specificity has been studied in patients presenting a rhabdomyolysis syndrome. The obtained results clearly demonstrated that this parameter may be used as a specific marker of myocardial injury, in contrast to total creatine kinase- or mass CK-MB measurements. In unstable angina, two groups of patients may be defined: one group with elevated troponin lc (> 0.60 microgram/L; 31 patients, group I), one other with normal troponin lc (< 0.35 microgram/L; 49 patients; group II). Quantitative angiographic analysis was performed on 50 patients including 18 patients from group I. Group I showed a more severe culprit lesion than group II. All the results suggested that troponin Ic might be an indicator of severity in unstable angina.