PDE4 cyclic nucleotide phosphodiesterases regulate cAMP abundance in cells and thereby regulate numerous processes, including cell growth and differentiation. The rat PDE4A5 isoform (human homologue PDE4A4) interacts with the AIP protein (also called XAP2 or ARA-9). Germline mutations in AIP occur in approximately 20% of patients with Familial Isolated Pituitary Adenoma (FIPA) and 20% of childhood-onset simplex somatotroph adenomas. We therefore examined the protein expression of PDE4A4 and the closely-related isoform PDE4A8 in normal human pituitary tissue and in pituitary adenomas. PDE4A4 had low expression in normal pituitary, but was significantly over-expressed in somatotroph, lactotroph, corticotroph and clinically non-functioning gonadotroph adenomas (P<0.0001 for all subtypes). Likewise, PDE4A8 was expressed in normal pituitary and was also significantly over-expressed in the adenoma subtypes (P<0.0001 for all). Among the different adenoma subtypes, corticotroph and lactotroph adenomas were the highest and lowest expressed for PDE4A4, respectively, whereas the opposite was observed for PDE4A8. Naturally occurring oncogenic variants in AIP were shown by a two-hybrid assay to disrupt the ability of AIP to interact with PDE4A5. A reverse-two-hybrid screen identified numerous additional variants in the TPR region of AIP that also disrupted its ability to interact with PDE4A5. The expression of PDE4A4 and PDE4A8 in normal pituitary, their increased expression in adenomatous pituitary cells where AIP is meant to participate, and the disruption of the PDE4A4-AIP interaction by AIP mutants may play a role in pituitary tumorigenesis.

Conclusion-sTfR appear to be elevated and related to the degree of anaemia and to the inflammatory process in RA. Reduced sTfR levels in patients with RA compared with patients with irondeficiency anaemia may indicate a reduced erythropoietic activity in RA.

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Objective To evaluate whether brown adipose tissue (BAT) activity is altered in women with polycystic ovary syndrome (PCOS), and whether BAT activity correlates with plasma levels of irisin, a myokine that can induce BAT formation. Design We performed a cross-sectional study including women with PCOS (n = 45) and a healthy control group (n = 25) matched by age and body mass index (BMI). Methods BAT activity was measured using 18F-FDG positron emission tomography-computed tomography (PET-CT) and plasma irisin levels were measured by a validated enzyme immunoassay. Results Total BAT activity was significantly reduced in women with PCOS (maximal standardized uptake value (SUVmax): median 7.4 g/mL, interquartile range 0.9–15.4) compared to controls (median 13.0 g/mL, interquartile range 4.7–18.4, P = 0.047). However, this difference was no longer significant after adjustment for waist circumference, a surrogate marker of central adiposity. In the PCOS group, BAT activity correlated negatively with BMI (Spearman’s r = −0.630, P = 0.000) and waist circumference (r = −0.592, P = 0.000) but not with plasma irisin levels. Conclusions BAT activity was reduced in women with PCOS possibly due to increased central adiposity. In PCOS women, BAT activity did not correlate with plasma irisin levels.

Type 4 phosphodiesterases (PDE4s) of the large PDE enzyme superfamily have unique specificity for cAMP and may, therefore, be relevant for somatotroph tumorigenesis. Somatotroph adenomas typically overexpress PDEs probably as part of a compensatory mechanism to reduce cAMP levels. The rat PDE4A5 isoform (human homolog PDE4A4) interacts with the AIP protein, coded by a tumour suppressor gene mutated in a subgroup of familial isolated pituitary adenomas (FIPAs). PDE4A8 is the closest related isoform of PDE4A4. We aimed to evaluate the expression of both PDE4A4 and PDE4A8 in GH cells of AIP-mutated adenomas and compare their expression with that in GH cells from sporadic AIP-mutation negative GH-secreting adenomas, where we had shown previously that both PDE4A4 and PDE4A8 isoforms had been over-expressed. Confocal immunofluorescence analysis showed that both PDE4A8 and PDE4A4 had lower expression in AIP-mutated somatotropinoma samples compared to sporadic GH-secreting tumours (P < 0.0001 for both). Based on the association of low PDE4A4 and PDE4A8 expression with germline AIP-mutations positive samples we suggest that lack of AIP hinders the upregulation of PDE4A8 and PDE4A4 protein seen in sporadic somatotrophinomas. These data point to a unique disturbance of the cAMP-PDE pathway in AIP-mutation positive adenomas, which may help to explain their well-described poor response to somatostatin analogues.