Calcitonin receptor expression in medullary thyroid carcinoma

Background: Calcitonin expression is a well-established marker for medullary thyroid carcinoma (MTC); yet the role of calcitonin receptor (CTR), its seventransmembrane G-protein coupled receptor, remains to be established in C-cells derived thyroid tumors. The aim of this work was to investigate CTR expression in MTC and to correlate such expression with clinicopathological features in order to evaluate its possible role as a prognostic indicator of disease aggressiveness and outcome. Methods: Calcitonin receptor expression was analyzed in a series of 75 MTCs by immunohistochemistry, and by qPCR mRNA quantification in specimens from four patients. Statistical tests were used to evaluate the correlation between CTR expression and the clinicopathological and molecular characteristics of patients and tumors. Results: Calcitonin receptor expression was detected in 62 out of 75 samples (82.7%), whereas 13 of the 75 samples (17.3%) were completely negative. CTR expression was significantly associated with expression of cytoplasmatic phosphatase and tensin homologue deleted on chromosome 10 and osteopontin, as well as with wild type RET/RAS genes and absence of tumor stroma, suggesting that CTR expression do not associate with clinicopathological signs of worse prognosis. Discussion: Calcitonin receptor expression appears to be associated in MTC with more differentiated status of the neoplastic cells

Involvement of the extracellular-signal regulated kinase 1/2 signaling pathway in amylin's eating inhibitory effect

Peripheral amylin inhibits eating via the area postrema (AP). Because amylin activates the extracellular-signal regulated kinase 1/2 (ERK) pathway in some tissues, and because ERK1/2 phosphorylation (pERK) leads to acute neuronal responses, we postulated that it may be involved in amylin's eating inhibitory effect. Amylin-induced ERK phosphorylation (pERK) was investigated by immunohistochemistry in brain sections containing the AP. pERK-positive AP-neurons were double-stained for the calcitonin 1a/b receptor, which is part of the functional amylin-receptor. AP sections were also phenotyped using dopamine-beta-hydroxylase (DBH) as a marker of noradrenergic neurons. The effect of fourth ventricular administration of the ERK cascade blocker U0126 on amylin's eating inhibitory action was tested in feeding trials. The number of pERK-positive neurons in the AP was highest approximately 10-15 min after amylin treatment; the effect appeared to be dose-dependent (5-20 μg/kg amylin). A portion of pERK-positive neurons in the AP carried the amylin-receptor and 22% of the pERK-positive neurons were noradrenergic. Pre-treatment of rats with U0126 decreased the number of pERK-positive neurons in the AP after amylin injection. U0126 also attenuated the ability of amylin to reduce eating, at least when the animals had been fasted 24h prior to the feeding trial. Overall, our results suggest that amylin directly stimulates pERK in AP neurons in a time- and dose-dependent manner. Part of the AP neurons displaying pERK were noradrenergic. At least under fasting conditions, pERK was shown to be a necessary part in the signaling cascade mediating amylin's anorectic effect

Hindbrain noradrenergic input to the hypothalamic PVN mediates the activation of oxytocinergic neurons induced by the satiety factor oleoylethanolamide

Oleoylethanolamide (OEA) is a gut-derived endogenous lipid that stimulates vagal fibers to induce satiety. Our previous work has shown that peripherally administered OEA activates c-fos transcription in the nucleus of the solitary tract (NST) and in the paraventricular nucleus (PVN), where it enhances oxytocin (OXY) expression. The anorexigenic action of OEA is prevented by the intracerebroventricular administration of a selective OXY receptor antagonist, suggesting a necessary role of OXYergic mediation of OEA's effect. The NST is the source of direct noradrenergic afferent input to hypothalamic OXY neurons, and therefore, we hypothesized that the activation of this pathway might mediate OEA effects on PVN neurons. To test this hypothesis, we subjected rats to intra-PVN administration of the toxin saporin (DSAP) conjugated to an antibody against dopamine-β-hydroxylase (DBH) to destroy hindbrain noradrenergic neurons. In these rats we evaluated the effects of OEA (10 mg/kg, ip) on feeding behavior, on c-Fos and OXY immunoreactivity in the PVN, and on OXY immunoreactivity in the posterior pituitary gland. We found that the DSAP lesion completely prevented OEA's effects on food intake, on Fos and OXY expression in the PVN, and on OXY immunoreactivity of the posterior pituitary gland; all effects were maintained in sham-operated rats. These results support the hypothesis that noradrenergic NST-PVN projections are involved in the activation of the hypothalamic OXY system, which mediates OEA's prosatiety action

Identification of central projections from amylin-activated neurons to the lateral hypothalamus

The ability of the pancreatic hormone amylin to inhibit food intake relies on a direct activation of the area postrema (AP). This activation is synaptically transmitted to the nucleus of the solitary tract (NTS), the lateral parabrachial nucleus (LPB), the central amygdaloid nucleus (Ce) and the lateral bed nucleus of stria terminalis (BSTL). Interestingly, neurons of the rostro-dorsal lateral hypothalamic area (dLHA), which are activated during fasting, are inhibited by peripheral amylin, although they lack amylin receptors. Using the retrograde tracer cholera toxin-B (Ctb) we analyzed whether the dLHA receives neuronal projections from amylin-activated brain areas. The anterograde tracer biotinylated dextran-amine (BDA) was used to confirm the projections and to identify further neuronal pathways potentially involved in amylin signaling. We identified dense projections from the amylin activated neurons in the LPB and sparse projections from the NTS to the dLHA. LPB fiber efferents were found in close proximity to dLHA nuclei activated by 24h of fasting. The AP and the Ce showed no projections to the dLHA. Dense efferents were also observed from the LPB to other hypothalamic areas, namely to the ventromedial, dorsomedial, paraventricular and arcuate nuclei. This study provides neuroanatomical evidence that among the amylin activated areas, the LPB provides the strongest input to the dLHA, thus it may mediate the amylin-induced inhibition of the dLHA