De-masking oxytocin-deficiency in craniopharyngioma and assessing its link with affective function.

Despite the high prevalence of panhypopituitarism and diabetes insipidus in patients with craniopharyngioma (CP), little is known about the functioning of the neuropeptide oxytocin in these patients. This is of special interest as tumor-associated lesions often impair sites critical for oxytocin production and release, and affective dysfunction in CP links with elsewhere reported prosocial, antidepressant and anxiolytic oxytocin effects. Using a prospective study-design, we tested whether oxytocin is reduced in CP-patients, and whether altered oxytocin levels account for affective and emotional dysfunction. 26 adult CP-patients and 26 healthy controls matched in sex and age underwent physical exercise, a stimulus previously shown to induce oxytocin release. Baseline and stimulated salivary oxytocin levels, as well as empathy, depression and anxiety scores were measured. Results showed that patients overall did not present with lower baseline oxytocin levels than controls (F[1,30]=0.21, p=0.649), but baseline oxytocin levels were indeed reduced in patients with hypothalamic damage, as assessed by MRI-based grading (F[2,9.79]=4.54, p=0.040). In response to exercise-induced stimulation, all CP-patients showed a blunted oxytocin-release compared to controls (F[1,30]=9.36, p=0.005). DI was not associated with oxytocin levels. Regarding affective function, unexpectedly, higher baseline oxytocin was related to higher trait anxiety (b=2.885, t(43)=2.421, p=0.020, CI[.478; 5.292]); the positive link with higher depression failed to reach statistical significance (b=1.928, t(43)=1.949, p=0.058, CI[-0.070; 3.927]). A blunted oxytocin-release was linked with higher state anxiety (b=-0.133, t(43)=-2.797, p=0.008, CI[-0.230; -0.037]). Empathy was not associated with oxytocin measures. In conclusion, we observed reduced baseline oxytocin levels only in CP-patients with hypothalamic damage. Exercise-induced stimulation de-masked an oxytocin-deficiency in all CP-patients. Baseline oxytocin levels and stimulated OT-responses might have different effects on affective function, which should be considered in future substitution paradigms.

Mammalian target of rapamycin inhibitors rapamycin and RAD001 (everolimus) induce anti-proliferative effects in GH-secreting pituitary tumor cells in vitro.

The effect of mammalian target of rapamycin (mTOR) inhibitors on pituitary tumors is unknown. Akt overexpression was demonstrated in pituitary adenomas, which may render them sensitive to the anti-proliferative effects of these drugs. The objective of the study was to evaluate the anti-proliferative efficacy of the mTOR inhibitor, rapamycin, and its orally bioavailable analog RAD001 on the GH-secreting pituitary tumor GH3 and MtT/S cells and in human GH-secreting pituitary adenomas (GH-omas) in primary cell cultures. Treatment with rapamycin or RAD001 significantly decreased the number of viable cells and cell proliferation in a dose- and time-dependent manner. This was reflected by decreased phosphorylation levels of the downstream mTOR target p70S6K. Rapamycin treatment of GH3 cells induced G0/G1 cell cycle arrest. In other tumor cell types, this was attributed to a decrease in cyclin D1 levels. However, rapamycin did not affect cyclin D1 protein levels in GH3 cells. By contrast, it decreased cyclin D3 and p21/CIP, which stabilizes cyclin D/cyclin-dependent kinase 4 (cdk4) complexes. Rapamycin inhibited FCS-induced retinoblastoma phosphorylation and subsequent E2F-transcriptional activity. In response to decreased E2F activity, the expression of the E2F-regulated genes cyclin E and cdk2 was reduced. Our results showed that mTOR inhibitors potently inhibit pituitary cell proliferation, suggesting that mTOR inhibition may be a promising anti-proliferative therapy for pituitary adenomas. This therapeutic manipulation may have beneficial effects particularly for patients harboring invasive pituitary tumors resistant to current treatments.

Requirement of cannabinoid receptor type 1 for the basal modulation of hypothalamic-pituitary-adrenal axis function.

The endocannabinoid system affects the neuroendocrine regulation of hormone secretion, including the activity of the hypothalamus-pituitary-adrenal (HPA) axis. However, the mechanisms by which endocannabinoids regulate HPA axis function have remained unclear. Here we demonstrate that mice lacking cannabinoid receptor type 1 (CB1-/-) display a significant dysregulation of the HPA axis. Although circadian HPA axis responsiveness is preserved, CB1-/- mice are characterized by an enhanced circadian drive on the HPA axis, resulting in elevated plasma corticosterone concentrations at the onset of the dark as compared with wild-type (CB1+/+) littermates. Moreover, CB1-/--derived pituitary cells respond with a significantly higher ACTH secretion to CRH and forskolin challenges as compared with pituitary cells derived from CB1+/+ mice. Both CBL-/- and CB1+/+ mice properly respond to a high-dose dexamethasone test, but response to low-dose dexamethasone is influenced by genotype. In addition, CB1-/- mice show increased CRH mRNA levels in the paraventricular nucleus of the hypothalamus but not in other extrahypothalamic areas, such as the amygdala and piriform cortex, in which CB1 and CRH mRNA have been colocalized. Finally, CB1-/- mice have selective glucocorticoid receptor mRNA down-regulation in the CA1 region of the hippocampus but not in the dentate gyrus or paraventricular nucleus. Conversely, mineralocorticoid receptor mRNA expression levels were found unchanged in these brain areas. In conclusion, our findings indicate that CB1 deficiency enhances the circadian HPA axis activity peak and leads to central impairment of glucocorticoid feedback, thus further outlining the essential role of the endocannabinoid system in the modulation of neuroendocrine functions.

The endogenous cannabinoid system affects energy balance via central orexigenic drive and peripheral lipogenesis.

The cannabinoid receptor type 1 (CB1) and its endogenous ligands, the endocannabinoids, are involved in the regulation of food intake. Here we show that the lack of CB1 in mice with a disrupted CB1 gene causes hypophagia and leanness. As compared with WT (CB1+/+) littermates, mice lacking CB1 (CB1-/-) exhibited reduced spontaneous caloric intake and, as a consequence of reduced total fat mass, decreased body weight. In young CB1-/- mice, the lean phenotype is predominantly caused by decreased caloric intake, whereas in adult CB1-/- mice, metabolic factors appear to contribute to the lean phenotype. No significant differences between genotypes were detected regarding locomotor activity, body temperature, or energy expenditure. Hypothalamic CB1 mRNA was found to be coexpressed with neuropeptides known to modulate food intake, such as corticotropin-releasing hormone (CRH), cocaine-amphetamine-regulated transcript (CART), melanin-concentrating hormone (MCH), and preproorexin, indicating a possible role for endocannabinoid receptors within central networks governing appetite. CB1-/- mice showed significantly increased CRH mRNA levels in the paraventricular nucleus and reduced CART mRNA levels in the dorsomedial and lateral hypothalamic areas. CB1 was also detected in epidydimal mouse adipocytes, and CB1-specific activation enhanced lipogenesis in primary adipocyte cultures. Our results indicate that the cannabinoid system is an essential endogenous regulator of energy homeostasis via central orexigenic as well as peripheral lipogenic mechanisms and might therefore represent a promising target to treat diseases characterized by impaired energy balance.