TGR5 (Gpbar-1) is a plasma membrane-bound, G protein-coupled receptor for bile acids. TGR5 messenger RNA (mRNA) has been detected in many tissues, including rat cholangiocytes and mouse gallbladder. A role for TGR5 in gallstone formation has been suggested, because TGR5 knockout mice did not develop gallstones when fed a lithogenic diet. In this study, expression and localization of TGR5 was studied in human gallbladders. TGR5 mRNA and protein were detected in all 19 gallbladders. Although TGR5 mRNA was significantly elevated in the presence of gallstones, no such relation was found for TGR5 protein levels. In order to study the localization of TGR5 in human gallbladders, a novel antibody was generated. The receptor was localized in the apical membrane and the rab11-positive recycling endosome of gallbladder epithelial cells.

Primary aldosteronism (PA) is the most common cause of secondary hypertension with a prevalence of 5–10% in unreferred hypertensive patients. Aldosterone producing adenomas (APAs) constitute a large proportion of PA cases and represent a surgically correctable form of the disease. The WNT signaling pathway is activated in APAs. In other tumors, a frequent cause of aberrant WNT signaling is mutation in the CTNNB1 gene coding for β-catenin. Our objective was to screen for CTNNB1 mutations in a well-characterized cohort of 198 APAs. Somatic CTNNB1 mutations were detected in 5.1% of the tumors, occurring mutually exclusive from mutations in KCNJ5, ATP1A1, ATP2B3 and CACNA1D. All of the observed mutations altered serine/threonine residues in the GSK3β binding domain in exon 3. The mutations were associated with stabilized β-catenin and increased AXIN2 expression, suggesting activation of WNT signaling. By CYP11B2 mRNA expression, CYP11B2 protein expression, and direct measurement of aldosterone in tumor tissue, we confirmed the ability for aldosterone production. This report provides compelling evidence that aberrant WNT signaling caused by mutations in CTNNB1 occur in APAs. This also suggests that other mechanisms that constitutively activate the WNT pathway may be important in APA formation.

Adrenal lesions belong to the spectrum of multiple endocrine neoplasia type 1 (MEN-1) syndrome. However, the prevalence of adrenal involvement, the characteristics, and the clinical management of adrenal lesions have not yet been clearly defined. A total of 66 patients with confirmed MEN1 germline mutations and 1 additional patient with typical manifestations in three organ systems were monitored in a regular screening program that included evaluation of the adrenals (median follow-up 96 months; range 12 to 300 months). Age at the diagnosis of MEN-1 and of adrenal tumors and the clinical characteristics, genotype, treatment, and follow-up of adrenal disease were analyzed. Adrenal lesions were identified in 18 of 67 (26.8%) MEN-1 patients and were diagnosed 5 years later than MEN-1. The median tumor diameter at diagnosis was 3.0 cm (range 1.2-15.0 cm), with most tumors being 3 cm or smaller. Eight patients had bilateral tumors. Ten patients had nonfunctional benign tumors, three had benign adrenal Cushing syndrome, and one patient had a pheochromocytoma. Four patients developed adrenocortical carcinomas (ACCs), three of which were functional. Nine adrenalectomies and one subtotal adrenalectomy were performed in six patients. Three patients with ACC died owing to the tumor. Patients with mutations in exons 2 and 10 developed adrenal tumors significantly more often than patients with other mutations (p <0.01). Adrenal tumors are a common feature of MEN-1 but occur later in the course of the disease. The lesions are often small and nonfunctional and can therefore be managed by close surveillance; others have significant malignant potential and should be considered for surgery when they are 3 cm or larger.

BackgroundAldosterone producing lesions are a common cause of hypertension, but genetic alterations for tumorigenesis have been unclear. Recently, either of two recurrent somatic missense mutations (G151R or L168R) was found in the potassium channel KCNJ5 gene in aldosterone producing adenomas. These mutations alter the channel selectivity filter and result in Na+ conductance and cell depolarization, stimulating aldosterone production and cell proliferation. Because a similar mutation occurs in a Mendelian form of primary aldosteronism, these mutations appear to be sufficient for cell proliferation and aldosterone production. The prevalence and spectrum of KCNJ5 mutations in different entities of adrenocortical lesions remain to be defined.Materials and MethodsThe coding region and flanking intronic segments of KCNJ5 were subjected to Sanger DNA sequencing in 351 aldosterone producing lesions, from patients with primary aldosteronism and 130 other adrenocortical lesions. The specimens had been collected from 10 different worldwide referral centers.ResultsG151R or L168R somatic mutations were identified in 47% of aldosterone producing adenomas, each with similar frequency. A previously unreported somatic mutation near the selectivity filter, E145Q, was observed twice. Somatic G151R or L168R mutations were also found in 40% of aldosterone producing adenomas associated with marked hyperplasia, but not in specimens with merely unilateral hyperplasia. Mutations were absent in 130 non-aldosterone secreting lesions. KCNJ5 mutations were overrepresented in aldosterone producing adenomas from female compared to male patients (63 vs. 24%). Males with KCNJ5 mutations were significantly younger than those without (45 vs. 54, respectively; p<0.005) and their APAs with KCNJ5 mutations were larger than those without (27.1 mm vs. 17.1 mm; p<0.005).DiscussionEither of two somatic KCNJ5 mutations are highly prevalent and specific for aldosterone producing lesions. These findings provide new insight into the pathogenesis of primary aldosteronism.