Molecular and Clinical Characteristics of Pituitary Adenoma Predisposition (PAP)

Pituitary adenomas are common benign neoplasms. Although most of them are sporadic, a minority occurs in familial settings. Heterozygous germline mutations in the aryl hydrocarbon receptor interacting protein (AIP) gene were found to underlie familial pituitary adenomas, a condition designated as pituitary adenoma predisposition (PAP). PAP confers incomplete penetrance of mostly growth hormone (GH) secreting adenomas in young patients, who often lack a family history of pituitary adenomas. This thesis work aimed to clarify the molecular and clinical characteristics of PAP. Applying the multiplex ligation-dependent probe amplification assay (MLPA), we found large genomic AIP deletions to account for a subset of PAP. Therefore, MLPA could be considered in PAP suspected patients with no AIP mutations found with conventional sequencing. We generated an Aip mouse model to examine pituitary tumorigenesis in vivo. The heterozygous Aip mutation conferred complete penetrance of pituitary adenomas that were mostly GH-secreting, rendering the phenotype of the Aip mouse similar to that of PAP patients. We suggest that AIP may function as a candidate gatekeeper gene in somatotrophs. To clarify molecular mechanisms of tumorigenesis, we elucidated the expression of AIP-related molecules in human and mouse pituitary tumors. The expression of aryl hydrocarbon receptor nuclear translocator (ARNT) was reduced in mouse Aip-deficient adenomas, and similar ARNT reduction was also evident in human AIP mutation positive adenomas. This suggests that in addition to participating in the hypoxia pathway, estrogen receptor signaling and xenobiotic response pathways, ARNT may play a role in AIP-related tumorigenesis. We also studied the characteristics and the response to therapy of PAP patients and found them to have an aggressive disease phenotype with young age at onset. Therefore, improvement in treatment outcomes of PAP patients would require their efficient identification and earlier diagnosis of the pituitary adenomas. The possible role of the RET proto-oncogene in tumorigenesis of familial AIP mutation negative pituitary adenomas was evaluated, but none of the found RET germline variants were considered pathogenic. Surprisingly, RET immunohistochemistry suggested possible underexpression of RET in AIP mutation positive pituitary adenomas an observation that merits further investigation.Aivolisäkkeen hyvänlaatuiset kasvaimet eli adenoomat ovat väestössä hyvin yleisiä kallonsisäisiä kasvaimia. Valtaosa niistä ilmaantuu sattumanvaraisesti, mutta pieni osa adenoomista esiintyy suvuttain. Äskettäin tunnistettiin pohjoissuomalaisissa suvuissa uusi ituradan geenivirhe, AIP-geenin mutaatio, joka aiheutti perinnöllistä alttiutta aivolisäkekasvaimiin (pituitary adenoma predisposition, PAP). Valtaosa PAP-potilaista on nuoria, ja heillä todetaan erityisesti kasvuhormonia erittäviä aivolisäkeadenoomia. Kuitenkaan kaikki AIP-mutaation perineet henkilöt eivät saa aivolisäkekasvainta, ja perinnöllisen kasvaintaipumuksen tunnistaminen voi tämän vuoksi olla vaikeaa. PAP-potilaiden parempi tunnistaminen voisi parantaa varhaisemman diagnostiikan kautta näiden potilaiden ennustetta. AIP-geenivirheeseen liittyvien molekyylitason mekanismien selvittäminen voisi myös selkeyttää näiden kasvainten syntyä sekä mahdollistaa uusien hoitomuotojen kehittämistä. Tässä väitöskirjatyössä selvitettiin PAP:n molekyylitason mekanismeja sekä kliinisiä piirteitä. Ensimmäistä kertaa todettiin, että PAP voi kehittyä ituradan laajojen AIP-geenin alueella tapahtuvien deleetioiden pohjalta. Tämä havainto antaa uuden tavan tunnistaa PAP-potilaita käyttäen deleetioita tunnistavaa MLPA-menetelmää. Luomassamme Aip-poistogeenisessä hiirimallissa kaikki Aip-heterotsygootit hiiret saivat 15kk ikään mennessä aivolisäkeadenooman. Nämä kasvaimet olivat valtaosin kasvuhormonia tuottavia, joten Aip-poistogeenisten hiirten ja PAP-potilaiden ilmiasu on hyvin samankaltainen. AIP-mutaation solutason mekanismien kartoituksessa todettiin AIP-proteiinin kanssa samassa solun signaaliketjussa olevan ARNT-proteiinin alentunut ilmentyminen AIP-mutatoituneissa ihmisen ja hiiren aivolisäkeadenoomissa. Tämä viittaa siihen, että ARNT voisi liittyä AIP-mutaatioiden aiheuttamaan kasvainten syntyyn. PAP-potilaiden kliinisiä piirteitä tutkittaessa havaittiin, että heidän aivolisäkeadenoomansa ilmenivät nuoremmalla iällä, olivat suurempia ja huonommin hoidolle reagoivia kuin kontrollipotilaiden kasvaimet. Tämä korostaa varhaisen diagnoosin ja tehokkaan hoidon tärkeyttä PAP-potilailla. RET-proto-onkogeenin ituratamutaatioiden ei voitu osoittaa liittyvän aivolisäkeadenooma-alttiuteen, mutta havaitsimme RET-ilmentymisen vähenemistä AIP-mutatoituneissa aivolisäkeadenoomissa

Fat free mass and obesity in relation to educational level

© 2009 Seppänen-Nuijten et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution Licens

New genetic loci link adipose and insulin biology to body fat distribution.

Body fat distribution is a heritable trait and a well-established predictor of adverse metabolic outcomes, independent of overall adiposity. To increase our understanding of the genetic basis of body fat distribution and its molecular links to cardiometabolic traits, here we conduct genome-wide association meta-analyses of traits related to waist and hip circumferences in up to 224,459 individuals. We identify 49 loci (33 new) associated with waist-to-hip ratio adjusted for body mass index (BMI), and an additional 19 loci newly associated with related waist and hip circumference measures (P < 5 × 10(-8)). In total, 20 of the 49 waist-to-hip ratio adjusted for BMI loci show significant sexual dimorphism, 19 of which display a stronger effect in women. The identified loci were enriched for genes expressed in adipose tissue and for putative regulatory elements in adipocytes. Pathway analyses implicated adipogenesis, angiogenesis, transcriptional regulation and insulin resistance as processes affecting fat distribution, providing insight into potential pathophysiological mechanisms

Unilateral Cleft Lip and Palate Has Asymmetry of Bony Orbits: A Retrospective Study

Facial asymmetry is common in unilateral clefts. Since virtual surgical planning (VSP) is becoming more common and automated segmentation is utilized more often, the position and asymmetry of the orbits can affect the design outcome. The aim of this study is to evaluate whether non-syndromic unilateral cleft lip and palate (UCLP) patients requiring orthognathic surgery have asymmetry of the bony orbits. Retrospectively, we analyzed the preoperative cone-beam computed tomography (CBCT) or computed tomography (CT) data of UCLP (n = 15) patients scheduled for a Le Fort 1 (n = 10) or bimaxillary osteotomy (n = 5) with VSP at the Cleft Palate and Craniofacial Center, Helsinki University Hospital. The width, height, and depth of the bony orbit and the distance between the sella turcica and infraorbital canal were measured. A volumetric analysis of the orbits was also performed. The measurements were tested for distribution, and the cleft side and the contralateral side were compared statistically with a two-sided paired t-test. To assess asymmetry in the non-cleft population, we performed the same measurements of skeletal class III patients undergoing orthognathic surgery at Päijät-Häme Central Hospital (n = 16). The volume of bony orbit was statistically significantly smaller (p = 0.014), the distance from the infraorbital canal to sella turcica was shorter (p = 0.019), and the anatomical location of the orbit was more medio-posterior on the cleft side than on the contralateral side. The non-cleft group showed no statistically significant asymmetry in any measurements. According to these preliminary results, UCLP patients undergoing orthognathic surgery show asymmetry of the bony orbit not seen in skeletal class III patients without a cleft. This should be considered in VSP for the correction of maxillary hypoplasia and facial asymmetry in patients with UCLP

No evidence of RET germline mutations in familial pituitary adenoma

Pituitary adenomas are common in the general population. Although most of them are sporadic, some occur in a familial setting. In familial pituitary adenoma patients it is common that no germline defects are found after screening of aryl hydrocarbon receptor interacting protein (AIP) and other genes known to underlie the condition, suggesting the existence of yet unknown predisposition genes. Recently, the RET proto-oncogene was found to be a novel in vivo interaction partner of AIP in the pituitary gland. Here, we have screened patients from 16 AIP mutation negative (AIPmut-) pituitary adenoma families for RET germline mutations to assess whether RET could play a role in pituitary adenoma predisposition, similar to AIP. We found five novel germline RET changes: one in RET Exon 4 and the rest in noncoding regions of RET. Two changes, c.1560*G&gt;A and -1285G&gt;A, were segregated in affected family members. We also analyzed the RET region with enhancer element locator (EEL) to identify RET regulatory elements, and to see whether the changes resided in these. None of the variants mapped to the regions predicted by EEL. Expression of RET was examined in ten AIPmut- and seven AIP mutation positive (AIPmut+) somatotropinomas by immunohistochemistry, with a trend showing reduced expression in the latter (P=0.05). We conclude that the RET variants are presumably not related to pituitary adenoma predisposition, although reduced RET expression may play a role in AIP-related genesis of somatotropinomas.</p

Mice with Inactivation of Aryl Hydrocarbon Receptor-Interacting Protein (Aip) Display Complete Penetrance of Pituitary Adenomas with Aberrant ARNT Expression

Mutations in the aryl hydrocarbon receptor-interacting protein (AIP) gene have been shown to predispose to pituitary adenoma predisposition, a condition characterized by growth hormone (GH)-secreting pituitary tumors. To study AIP-mediated tumorigenesis, we generated an Aip mouse model. Heterozygous mice developed normally but were prone to pituitary adenomas, in particular to those secreting GH. A complete loss of AIP was detected in these lesions, and full penetrance was reached at the age of 15 months. No excess of any other tumor type was found. Ki-67 analysis indicated that Aip-deficient tumors have higher proliferation rates compared with Aip-proficient tumors, suggesting a more aggressive disease. Similar to human AIP-deficient pituitary adenomas, immunohistochemical studies showed that expression of aryl hydrocarbon receptor nuclear translocator 1 or 2 (ARNT or ARNT2) protein was lost in the mouse tumors, suggesting that mechanisms of AIP-related tumorigenesis involve aberrant ARNT function. The Aip+/− mouse appears to be an excellent model for the respective human disease phenotype. This model constitutes a tool to further study AIP-associated pituitary tumorigenesis and may be potentially valuable in efforts to develop therapeutic strategies to treat pituitary adenomas

Large genomic deletions in AIP in pituitary adenoma predisposition

Context: Germline mutations in AIP have been recently shown to cause pituitary adenoma predisposition (PAP). Subsequently, many intragenic germline mutations have been reported, both in familial and in sporadic settings. Objective: Our objective was to evaluate the possible contribution of large genomic germline AIP deletions, an important mutation type in tumor predisposition syndromes, in PAP. Design: Here, we applied the multiplex ligation-dependent probe amplification assay to examine whether large genomic AIP or MEN1 alterations account for a subset of PAP cases. Patients: The study was performed on familial and sporadic pituitary adenoma cases of European origin, which had previously tested negative for germline AIP and MEN1 mutations by sequencing. Results: Two of 21 pituitary adenoma families (9.5%) were found to harbor an AIP deletion. No copy number changes were detected among 67 sporadic pituitary adenoma patients. No MEN1 deletions were found. Conclusions: The present study shows that large genomic AIP deletions account for a subset of PAP. Therefore, in suspected PAP cases undergoing counseling and AIP genetic testing, multiplex ligation-dependent probe amplification could be considered if direct sequencing does not identify a mutation.</p

Clinical characteristics and therapeutic responses in patients with Germ-line AIP mutations and pituitary adenomas : An international collaborative study

Context: AIP mutations (AIPmut) give rise to a pituitary adenoma predisposition that occurs in familial isolated pituitary adenomas and less often in sporadic cases. The clinical and therapeutic features of AIPmut-associated pituitary adenomas have not been studied comprehensively. Objective: The objective of the study was to assess clinical/therapeutic characteristics of AIPmut pituitary adenomas. Design: This study was an international, multicenter, retrospective case collection/database analysis. Setting: The study was conducted at 36 tertiary referral endocrine and clinical genetics departments. Patients: Patients included 96 patients with germline AIPmut and pituitary adenomas and 232 matched AIPmut-negative acromegaly controls. Results: The AIPmut population was predominantly young and male (63.5%); first symptoms occurred as children/adolescents in 50%. At diagnosis, most tumors were macroadenomas (93.3%); extension and invasion was common. Somatotropinomas comprised 78.1% of the cohort; there were also prolactinomas (n = 13), nonsecreting adenomas (n = 7), and a TSH-secreting adenoma. AIPmut somatotropinomas were larger (P = 0.00026), with higher GH levels (P = 0.00068), more frequent extension (P = 0.018) and prolactin cosecretion (P = 0.00023), and occurred 2 decades before controls (P < 0.000001). Gigantism was more common in the AIPmut group (P < 0.000001). AIPmut somatotropinoma patients underwent more surgical interventions (P = 0.00069) and had lower decreases in GH (P = 0.00037) and IGF-I (P = 0.028) and less tumor shrinkage with somatostatin analogs (P < 0.00001) vs. controls. AIPmut prolactinomas occurred generally in young males and frequently required surgery or radiotherapy. Conclusions: AIPmut pituitary adenomas have clinical features that may negatively impact treatment efficacy. Predisposition for aggressive disease in young patients, often in a familial setting, suggests that earlier diagnosis of AIPmut pituitary adenomas may have clinical utility

Amerindian-specific regions under positive selection harbour new lipid variants in Latinos.

Dyslipidemia and obesity are especially prevalent in populations with Amerindian backgrounds, such as Mexican-Americans, which predispose these populations to cardiovascular disease. Here we design an approach, known as the cross-population allele screen (CPAS), which we conduct prior to a genome-wide association study (GWAS) in 19,273 Europeans and Mexicans, in order to identify Amerindian risk genes in Mexicans. Utilizing CPAS to restrict the GWAS input variants to only those differing in frequency between the two populations, we identify novel Amerindian lipid genes, receptor-related orphan receptor alpha (RORA) and salt-inducible kinase 3 (SIK3), and three loci previously unassociated with dyslipidemia or obesity. We also detect lipoprotein lipase (LPL) and apolipoprotein A5 (APOA5) harbouring specific Amerindian signatures of risk variants and haplotypes. Notably, we observe that SIK3 and one novel lipid locus underwent positive selection in Mexicans. Furthermore, after a high-fat meal, the SIK3 risk variant carriers display high triglyceride levels. These findings suggest that Amerindian-specific genetic architecture leads to a higher incidence of dyslipidemia and obesity in modern Mexicans

Amerindian-specific regions under positive selection harbour new lipid variants in Latinos.

Dyslipidemia and obesity are especially prevalent in populations with Amerindian backgrounds, such as Mexican-Americans, which predispose these populations to cardiovascular disease. Here we design an approach, known as the cross-population allele screen (CPAS), which we conduct prior to a genome-wide association study (GWAS) in 19,273 Europeans and Mexicans, in order to identify Amerindian risk genes in Mexicans. Utilizing CPAS to restrict the GWAS input variants to only those differing in frequency between the two populations, we identify novel Amerindian lipid genes, receptor-related orphan receptor alpha (RORA) and salt-inducible kinase 3 (SIK3), and three loci previously unassociated with dyslipidemia or obesity. We also detect lipoprotein lipase (LPL) and apolipoprotein A5 (APOA5) harbouring specific Amerindian signatures of risk variants and haplotypes. Notably, we observe that SIK3 and one novel lipid locus underwent positive selection in Mexicans. Furthermore, after a high-fat meal, the SIK3 risk variant carriers display high triglyceride levels. These findings suggest that Amerindian-specific genetic architecture leads to a higher incidence of dyslipidemia and obesity in modern Mexicans