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Akiyo Tanabe, Mitsuhide Naruse, Taro Wasada, Kiyoko Naruse, Takanobu Yoshimoto, Yasue Omori and Hiroshi Demura

Tanabe A, Naruse M. Wasada T, Naruse K, Yoshimoto T, Omori Y, Demura H. Effects of acute hyperinsulinemia on plasma atrial and brain natriuretic peptide concentrations. Eur J Endocrinol 1995;132:693–8. ISSN 0804–4643

Impaired renal sodium excretion and increased plasma atrial natriuretic peptide (ANP) levels have been reported in patients with hypertension associated with insulin resistance and hyperinsulinemia. To clarify the interrelationship between hyperinsulinemia and plasma natriuretic peptides, we investigated the effects of physiological and non-physiological hyperinsulinemia on the plasma ANP and brain natriuretic peptide (BNP) levels. Plasma immunoreactive insulin (IRI), ANP and BNP levels were determined by a euglycemic–hyperinsulinemic glucose clamp in 20 patients with non-insulin-dependent diabetes mellitus, by a glucose challenge test in 22 normal subjects and by an insulin challenge test in six normal subjects. Both in the glucose clamp and the glucose challenge test, plasma ANP showed a significant increase in association with increased plasma IRI and plasma volume. However, there was no significant correlation between the changes in plasma ANP levels and plasma IRI levels in view of the peak values and the area under the curve of their responses. In addition, the plasma ANP did not show any significant change despite the marked elevation of plasma IRI in the insulin challenge test. There was no significant change in plasma BNP under any of the hyperinsulinemic conditions. These findings provide in vivo evidence for the lack of a direct effect of acute hyperinsulinemia on natriuretic peptides, although the chronic effects of hyperinsulinemia remain to be elucidated.

Akiyo Tanabe, Department of Medicine, Institute of Clinical Endocrinology, Tokyo Women's Medical College, 8-1 Kawada-cho, Shinjuku-ku, Tokyo 162, Japan

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Toru Tateno, Hajime Izumiyama, Masaru Doi, Takanobu Yoshimoto, Masayoshi Shichiri, Naoko Inoshita, Kenichi Oyama, Shozo Yamada and Yukio Hirata

Objective

Differential expression of several genes between ACTH-secreting pituitary tumors causing Cushing' disease (CD), silent corticotroph adenoma (SCA), and non-functioning pituitary tumors (NFT) was investigated.

Design and methods

We used tissue specimens from 35 pituitary tumors (12 CD, 8 SCA, and 15 NFT). Steady-state mRNA levels of the genes related to proopiomelanocortin (POMC) transcription, synthesis, processing, and secretion, such as neurogenic differentiation 1 (NeuroD1), T-box 19 (Tpit), corticotropin releasing hormone receptor (CRHR), vasopressin receptor 1b (V1bR), prohormone convertase (PC) 1/3 and PC2, 11β-hydroxysteroid dehydrogenase (11β-HSD) type 1 and type 2, glucocorticoid receptor α (GRα), annexin A1, histone deacetylase 2 (HDAC2), and BRM/SWI2-related gene 1, were determined by real-time RT-PCR.

Results and conclusion

POMC and Tpit mRNA levels were greater in CD and SCA than those in NFT. NeuroD1 mRNA levels were less in CD than those in NFT, but almost comparable between SCA and NFT. PC1/3 mRNA levels were greater in CD, but less in SCA than those in NFT. PC2 mRNA levels in CD and SCA were less than those in NFT. CRHR, V1bR, and 11β-HSD2 mRNA levels in CD were greater than those in SCA and NFT. HDAC2 mRNA levels in CD and SCA were lower than those in NFT. In conclusion, our study demonstrated that the genes related to transcription, synthesis, processing, and secretion of POMC are differentially regulated in ACTH-secreting pituitary tumors causing CD and SCA compared with those in NFT. This may partly explain the development of clinically active and inactive CD.

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Masanori Murakami, Takanobu Yoshimoto, Kazuhiko Nakabayashi, Kyoichiro Tsuchiya, Isao Minami, Ryotaro Bouchi, Hajime Izumiyama, Yasuhisa Fujii, Kosei Abe, Chiharu Tayama, Koshi Hashimoto, Takayoshi Suganami, Ken-ichiro Hata, Kazunori Kihara and Yoshihiro Ogawa

Objective

The pathophysiology of aldosterone-producing adenomas (APA) has been investigated intensively through genetic and genomic approaches. However, the role of epigenetics in APA is not fully understood. In the present study, we explored the relationship between gene expression and DNA methylation status in APA.

Methods

We conducted an integrated analysis of transcriptome and methylome data of paired APA-adjacent adrenal gland (AAG) samples from the same patient. The adrenal specimens were obtained from seven Japanese patients with APA who underwent adrenalectomy. Gene expression and genome-wide CpG methylation profiles were obtained from RNA and DNA samples that were extracted from those seven paired tissues.

Results

Methylome analysis showed global CpG hypomethylation in APA relative to AAG. The integration of gene expression and methylation status showed that 34 genes were up-regulated with CpG hypomethylation in APA. Of these, three genes (CYP11B2, MC2R, and HPX) may be related to aldosterone production, and five genes (PRRX1, RAB38, FAP, GCNT2, and ASB4) are potentially involved in tumorigenesis.

Conclusion

The present study is the first methylome analysis to compare APA with AAG in the same patients. Our integrated analysis of transcriptome and methylome revealed DNA hypomethylation in APA and identified several up-regulated genes with DNA hypomethylation that may be involved in aldosterone production and tumorigenesis.

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Yujiro Nakano, Takanobu Yoshimoto, Ryo Watanabe, Masanori Murakami, Tatsuya Fukuda, Kazutaka Saito, Yasuhisa Fujii, Takumi Akashi, Toshihiro Tanaka, Tetsuya Yamada, Mitsuhide Naruse and Yoshihiro Ogawa

Objective

The pathophysiology of aldosterone-producing adenomas (APAs) has been intensively investigated using genetic and epigenetic approaches. However, the role of miRNAs in APA is not fully understood. The present study profiled miRNAs in APAs as an exploratory approach to elucidate their pathophysiological roles in APAs.

Design

Tissues of APAs and other adrenocortical adenomas were obtained from patients who underwent adrenalectomy.

Methods

Candidate miRNAs differentially detected from samples were examined by whole miRNA sequencing. The expression of candidate miRNAs in APA tissues were further validated by real-time quantitative polymerase chain reaction (qPCR). Further, differential miRNA expression between APAs with and without KCNJ5 somatic mutations was examined. Prediction of miRNA target genes was performed by bioinformatics analysis. For specific miRNAs, correlation analysis between the levels of their target genes and CYP11B2 was analyzed in APA tissues.

Results

Our study determined differential expression of six miRNAs in APA or APA with KCNJ5 mutations. We further demonstrated that miR299 levels were negatively correlated with mRNA levels of CACNB2, which encodes the beta-subunit of the L-type calcium channel. Additionally, we found significant correlations among miR299, CACNB2, and CYP11B2 levels in APA tissues.

Conclusions

Our study suggests the possible pathophysiological involvement of specific miRNAs in calcium signaling and aldosterone hypersecretion in APAs. Further studies, including in vitro analyses, are required to clarify these findings.

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Hiroki Kobayashi, Yoshihiro Nakamura, Masanori Abe, Isao Kurihara, Hiroshi Itoh, Takamasa Ichijo, Yoshiyu Takeda, Takashi Yoneda, Takuyuki Katabami, Mika Tsuiki, Norio Wada, Yoshihiro Ogawa, Ryuichi Sakamoto, Junji Kawashima, Masakatsu Sone, Nobuya Inagaki, Takanobu Yoshimoto, Tetsuya Yamada, Ryuji Okamoto, Yuichi Matsuda, Megumi Fujita, Minemori Watanabe, Kouichi Tamura, Akiyo Tanabe, Mitsuhide Naruse and JPAS/JRAS Study Group

Objectives

We investigated the clinical significance of ACTH stimulation during adrenal venous sampling (AVS) by surgical outcome of primary aldosteronism (PA).

Design

Multicenter retrospective study by Japan PA study.

Method

We allocated 314 patients with both basal and ACTH-stimulated AVS data who underwent adrenalectomy to three groups: basal lateralization index (LI) ≥2 with ACTH-stimulated LI ≥4 on the ipsilateral side (Unilateral (U) to U group, n = 245); basal LI <2 with ACTH-stimulated LI ≥4 (Bilateral (B) to U group, n = 15); and basal LI ≥2 with ACTH-stimulated LI <4 (U to B group, n = 54). We compared surgical outcomes among the groups using the Primary Aldosteronism Surgical Outcome (PASO) criteria.

Results

Compared with U to U group, U to B group had poor clinical and biochemical outcomes and low rates of adrenal adenoma as pathological findings (P = 0.044, 0.006, and 0.048, respectively), although there were no significant differences between U to U and B to U groups. All patients in U to B group with clinical and biochemical benefits, however, had adrenal adenoma as pathological findings and could be well differentiated from those with poor surgical outcomes via basal LI (>8.3), but not ACTH-stimulated LI. These results were similar even when we defined each group based on a cut-off value of 4 for basal LI.

Conclusions

Although PA patients in U to B group had worse surgical outcomes than did those in U to U group, basal LI could discriminate among patients with better surgical outcomes in U to B group.