High permanent plasma adrenaline levels: a marker of adrenal medullary disease in medullary thyroid carcinoma

Beta-adrenergic-AMPK pathway phosphorylates acetyl-CoA carboxylase in a high-epinephrine rat model, SPORTS

We established a new animal model called SPORTS (Spontaneously-Running Tokushima-Shikoku) rats, which show high-epinephrine (Epi) levels. Recent reports show that Epi activates adenosine monophosphate (AMP)-activated protein kinase (AMPK) in adipocytes. Acetyl-CoA carboxylase (ACC) is the rate-limiting enzyme in fatty acid synthesis, and the enzymatic activity is suppressed when its Ser-79 is phosphorylated by AMPK. The aim of this study was to investigate the in vivo effect of Epi on ACC and abdominal visceral fat accumulation. We divided both 6-week male control and SPORTS rats into two groups, which were fed either normal diet or high fat and sucrose (HFS) diet for 16 weeks. At the end of diet treatment, retroperitoneal fat was collected for western blotting and histological analysis. Food intake was not different among the groups, but SPORTS rats showed significantly lower weight gain than control rats in both diet groups. After 10 weeks of diet treatment, glucose tolerance tests (GTTs) revealed that SPORTS rats had increased insulin sensitivity. Furthermore, SPORTS rats had lower quantities of both abdominal fat and plasma triglyceride (TG). In abdominal fat, elevated ACC Ser-79 phosphorylation was observed in SPORTS rats and suppressed by an antagonist of beta-adrenergic receptor (AR), propranolol, or an inhibitor of AMPK, Compound C. From these results, high level of Epi induced ACC phosphorylation mediated through beta-AR and AMPK signaling pathways in abdominal visceral fat of SPORTS rats, which may contribute to reduce abdominal visceral fat accumulation and increase insulin sensitivity. Our results suggest that beta-AR-regulated ACC activity would be a target for treating lifestyle-related diseases, such as obesity.

Study of diurnal fluctuations of plasma methoxyamines in healthy volunteers

OBJECTIVE

We studied the diurnal fluctuations of plasma concentrations of methoxyamines (metanephrine and normetanephrine) and of their parent amines (epinephrine and norepinephrine) in normotensive subjects.

DESIGN

Serial blood sampling at 09.00 h, 11.00 h, 12.00 h, 14.00 h, 16.00 h, 18.00 h and 20.00 h in 28 healthy volunteers at rest. Determination of plasma concentrations of free catecholamines and total methoxyamines (free and sulpho-conjugates) was carried out by high-performance liquid chromatography with electrochemical detection.

RESULTS

Mean (+/- SD) plasma concentrations of total metanephrine (MN) and normetanephrine (NMN) were 4.31 +/- 1.73 nmol/l (range: 0.96-9.3 nmol/l) and 8.13 +/- 2.54 nmol/l (range: 3.14-17.0 nmol/l), respectively. The NMN/MN ratio ranged between 0.8 and 7.8 (mean +/- SD 2.1 +/- 1.0). Mean plasma concentrations of free epinephrine and norepinephrine were 0.21 +/- 0.12 nmol/l (range: 0.06-1.39 nmol/l) and 1.61 +/- 0.62 nmol/l (range: 0.47-4.01 nmol/l), respectively. Despite marked intraindividual fluctuations, mean methoxyamine and catecholamine levels remained constant over the entire duration of the experiment.

CONCLUSIONS

The absence of fluctuations of plasma levels of total methoxyamines suggests that their measurement could be carried out at any time within the diurnal time frame. Further investigations, however, remain necessary to validate these findings in patients with hypertension and/or pheochromocytoma, and to explain the ever important intraindividual variation in plasma concentrations of methoxyamines and of their parent compounds.

[The diagnosis of atypical pheochromocytoma: a challenge for the biologist as well]

Biological diagnosis of pheochromocytoma is relatively easy in those cases releasing great amounts of catecholamines with strong clinical features; instead, diagnosis could be more problematic in atypical or asymptomatic familial pheochromocytoma with small tumors secreting low catecholamine amounts. Several plasma and urine adrenergic markers must be used to confirm the clinical suspicion. We have discussed the biological data of three totally asymptomatic pheochromocytomas (cases no 2, 3, 4) and one case with a very discrete clinical manifestation (no 1). Three patients had very small tumors (4, 7 and 25 g) secreting preeminently adrenaline, one patient had a 45 g adrenal incidentaloma without clinical expression. Our study shows that, in these special cases, except for an inconstant increase of adrenaline, plasma and urine catecholamines and urine VMA can be normal. The most useful markers are plasma and urine methoxyamines. However, plasma methoxyamines are the most sensitive because their increase over reference values is by far greater than in urines. Several factors may explain these findings: a low tumoral secretion, the nature of the released amine, the short half-life of catecholamines in plasma and, in some cases, the involvement of intratumoral catecholamine metabolism. Analysis of the ratio NMN/MN in plasma provides an additional diagnosis tool to reveal adrenaline secretion abnormalities.

Plasma normetanephrine and metanephrine for detecting pheochromocytoma in von Hippel-Lindau disease and multiple endocrine neoplasia type 2

BACKGROUND

The detection of pheochromocytomas in patients at risk for these tumors, such as patients with von Hippel-Lindau disease or multiple endocrine neoplasia type 2 (MEN-2), is hindered by the inadequate sensitivity of commonly available biochemical tests. In this study we evaluated measurements of plasma normetanephrine and metanephrine for detecting pheochromocytomas in patients with von Hippel-Lindau disease or MEN-2.

METHODS

We studied 26 patients with von Hippel-Lindau disease and 9 patients with MEN-2 who had histologically verified pheochromocytomas and 50 patients with von Hippel-Lindau disease or MEN-2 who had no radiologic evidence of pheochromocytoma. Von Hippel-Lindau disease and MEN-2 were diagnosed on the basis of germ-line mutations of the appropriate genes. The plasma concentrations of normetanephrine and metanephrine were compared with the plasma concentrations of catecholamines (norepinephrine and epinephrine) and urinary excretion of catecholamines, metanephrines, and vanillylmandelic acid.

RESULTS

The sensitivity of measurements of plasma normetanephrine and metanephrine for the detection of tumors was 97 percent, whereas the other biochemical tests had a sensitivity of only 47 to 74 percent. All patients with MEN-2 had high plasma concentrations of metanephrine, whereas the patients with von Hippel-Lindau disease had almost exclusively high plasma concentrations of only normetanephrine. One patient with von Hippel-Lindau disease had a normal plasma normetanephrine concentration; this patient had a very small adrenal tumor (<1 cm). The high sensitivity of measurements of plasma normetanephrine and metanephrine was accompanied by a high level of specificity (96 percent).

CONCLUSIONS

Measurements of plasma normetanephrine and metanephrine are useful in screening for pheochromocytomas in patients with a familial predisposition to these tumors.

Screening for adrenal medullary disease in patients with medullary thyroid carcinoma

Adrenal medullary disease (AMD) is clinically silent in most patients with medullary thyroid carcinoma (MTC). It was screened yearly by urinary measurements of catecholamines and derivates, and by abdominal ultrasonography (US) in a series of 174 patients with MTC. In cases with suspicion of AMD, abdominal computerized tomography and scintigraphy with meta-iodobenzylguanidine were also performed. AMD was discovered in 10 patients (one adrenal medullary hyperplasia and 9 pheochromocytomas). Three patients were already known to belong to a type II multiple endocrine neoplasia (MEN-2a) family and two had a MEN-2b syndrome. In 5 patients previously considered as having either a sporadic (4 cases) or a familial type of isolated MTC (one case), the occurrence of AMD led to diagnose a MEN-2a syndrome. The diagnostic values of the tests were evaluated by a case-control study. Urinary metanephrine plus normetanephrine (MN+N) had an acceptable sensitivity (0.8) and specificity (0.8). The other urinary tests had a high specificity (range: 0.8 to 1) but a poor sensitivity (range: 0.1 to 0.5). US had a high sensitivity (0.8) and a specificity of one. MN+N and US performed yearly constitute a simple and efficient strategy to screen for AMD in patients with MTC.

Phaeochromocytoma in multiple endocrine neoplasia type 2 A: survey of 100 cases

OBJECTIVE

We report clinical, biochemical, morphological and histological data of phaeochromocytoma in 40 French families and in apparently sporadic cases of multiple endocrine neoplasia (MEN) type 2 A (medullary thyroid carcinoma, phaeochromocytoma, with or without hyperparathyroidism).

DESIGN

This retrospective study was obtained from cases registered by the 'Groupe d'Etudes des Tumeurs à Calcitonine' from 1968 to 1990. We analysed the cases having sufficiently precise data on phaeochromocytoma with Pigas Software.

PATIENTS

Characteristics of phaeochromocytoma in 100 patients with MEN 2 A were reviewed. Phaeochromocytoma was bilateral in 51%. The disease was inherited in 94 patients from 40 families (40 probands, 54 relatives), and was apparently sporadic in six.

RESULTS

In this series, diagnostic circumstances were highly suggestive of phaeochromocytoma in 39.8% of the cases, whereas in 43.2%, diagnosis was made through systematic investigations of patients, either before (27.3%) or after (13.6%) thyroidectomy, or after discovery of hyperparathyroidism (2.3%). Fifteen per cent of patients were detected by family screening. Sudden death occurred in 8.9%, malignant phaeochromocytoma in 3%, and ectopic tissue in 4% of the cases. Urinary metanephrines appeared to be the most sensitive screening test. The extent of clinical symptoms was not associated with a particular hormonal pattern. Bilateral adrenalectomy was performed in 60% (in one step in 50%, in two steps in 10%). In these patients, bilateral histological lesions were observed in 92.5%. Simultaneous diagnosis for adrenal and thyroid disease was made in 73.4%, but phaeochromocytoma may be diagnosed before (9.6%) or after (17%) medullary thyroid carcinoma, with an interval greater than 2 years in 25 cases.

CONCLUSION

Owing to variable clinical symptoms of phaeochromocytoma in these 100 cases of MEN 2 A, systemic biological adrenal assay is required. The search for phaeochromocytoma in medullary thyroid carcinoma (and vice versa) has to be systematically performed, even in apparently sporadic cases. Screening for phaeochromocytoma must be repeated for years, owing to the frequency of bilateral adrenal disease.