Insulin secretion and sensitivity before and after surgical treatment for aldosterone-producing adenoma.

AIM: Primary aldosteronism, which is usually caused by an aldosterone-producing tumour, affects glucose metabolism. The effects of this condition on insulin secretion and insulin sensitivity have remained unclear, however. To gain insight into the influence of primary aldosteronism on glucose tolerance, various parameters related to insulin secretion or insulin sensitivity in patients with an aldosterone-producing tumour were comprehensively analyzed. METHODS: To assess 14 patients with an aldosterone-producing tumour, hyperglycaemic and hyperinsulinaemic-euglycaemic clamp tests as well as oral glucose tolerance tests (OGTTs) were performed before and after tumour excision. Time between presurgical analysis and surgery was 27-559 (194±132) days, and 14-142 (51±38) days between surgery and postsurgical analysis. Various parameters related to insulin secretion or sensitivity as determined by OGTT as well as hyperglycaemic and hyperinsulinaemic-euglycaemic clamp analyses were evaluated. RESULTS: Surgical treatment of tumours ameliorated hypokalaemia and reduced plasma aldosterone levels. First and second phases of insulin secretion during the hyperglycaemic clamp, as well as the insulinogenic index and total insulin secretion measured during OGTT, were also improved after surgery. In addition, the insulin sensitivity index determined during the hyperinsulinaemic-euglycaemic clamp was reduced after surgery. CONCLUSION: Primary aldosteronism impairs insulin secretion.

AIP mutation identified in a patient with acromegaly caused by pituitary somatotroph adenoma with neuronal choristoma.

Pituitary adenoma with neuronal choristoma (PANCH) is a rare condition that includes ganglion cells and GH-producing tumor that is characterized by sparsely granulated somatotroph cell type. However, the pathophysiology of this condition remains to be elucidated. We report a case of 46-year-old woman with acromegaly caused by PANCH. The patient had a large and invasive macroadenoma that was resistant to preoperative therapy with somatostatin analogue (SSA) and dopamine agonist. Histological examination showed typical diffuse, chromophobe-type adenoma containing ganglion cells, and sparsely granulated somatotroph cell type, which were consistent with PANCH. Genetic analysis showed heterozygous germline missense mutation in the AIP gene that results in Y261X amino acid substitution. The clinical characteristics of acromegaly associated with AIP mutations are reportedly macroadenomas with tumor extension and invasion, lower decreases in GH and IGF-I and less tumor shrinkage with SSA treatment, and sparsely granulated somatotroph cell type, which are comparable with those observed in PANCH. Taken together, the mutation in AIP gene may explain the clinical characteristics and pathogenesis of PANCH.

Growth hormone deficiency in 2 siblings associated with combined GH1 gene polymorphisms.

This study was performed to clarify the pathophysiology of familial short stature with moderate GH deficiency.The siblings showed moderate GH deficiency with short stature. Pedigree analysis revealed an accumulation of the history of short stature in father's relatives, although there was no consanguinity.We performed sequencing analysis of GH1 and GHSR gene in the siblings.We detected SNPs in the GH1 gene in the combination of the - 278G, - 57T, +1169T, and +2103C in one allele from the father and the - 278T, - 57G, +1169 A, and +2103T in the other allele from the mother in the siblings. In the previous report, the -278G and - 57T allele are associated with low serum IGF-I levels in patients with isolated GH deficiency and the haplotype of the - 278T, - 57G, +1169 A, and +2103T allele exhibited an impaired GH secretion in vitro.It is suggested that these haplotypes were responsible at least in part for the GH deficiency and short stature in these siblings.

Novel ultrasonic bone densitometry based on two longitudinal waves: significant correlation with pQCT measurement values and age-related changes in trabecular bone density, cortical thickness, and elastic modulus of trabecular bone in a normal Japanese population.

UNLABELLED: A reference database for trabecular bone density, cortical thickness, and elastic modulus of trabecular bone for a novel ultrasonic bone densitometry system (LD-100) based on two longitudinal waves (fast and slow) was determined over a wide age range in a normal Japanese population. INTRODUCTION: A novel ultrasonic bone densitometry system (LD-100 system) was applied to create a reference database for trabecular bone density (TBD), cortical thickness (CoTh), and elastic modulus of trabecular bone (EMTb) for this device over a wide age range in a normal Japanese population. METHODS: In a comparative study between LD-100 and peripheral quantitative computed tomography (pQCT) systems, 52 individuals were examined by both systems at the same radius simultaneously. To create a reference database, a total of 2,380 healthy subjects (1,179 men, 1,201 women), ages 18-99 years, were examined using the LD-100 system. RESULTS: Highly significant correlations between the LD-100 and pQCT systems were found in TBD (r = 0.877, p < 0.001) and CoTh (r = 0.723, p < 0.001). For the reference database, peak values of TBD, CoTh, and EMTb were observed at 30-34 years (255.09 mg/cm(3)), 20-24 years (5.23 mm), and 20-24 years (4.09 GPa) in men, and at 25-29 years (209.24 mg/cm(3)), 25-29 years (3.98 mm), and 20-24 years (3.33 GPa) in women, respectively. The TBD fell significantly (p < 0.05) beginning at 55-59 years in both sexes, with a relatively rapid decrease in women. The CoTh showed a significant decrease beginning at 40-44 years in men and 50-54 years in women. The EMTb showed a significant decrease beginning at 40-44 years in men and 55-59 years in women. CONCLUSIONS: The LD-100 system is a useful bone densitometry device and the database of age-related changes in TBD, CoTh, and EMTb established in this study will provide fundamental data for future studies related to bone status.

A novel splice site mutation of the thiazide-sensitive NaCl cotransporter gene in a Japanese patient with Gitelman syndrome.

Gitelman syndrome (GS, MIM 263800) is an inherited disorder characterized by metabolic alkalosis with hypokalemia, hypomagnesemia, and hypocalciuria. The genetic abnormalities causing GS are known to lie in the thiazide-sensitive NaCl cotransporter (TSC), which is expressed in the distal tubule of the kidney. The TSC gene, located at chromosome 16, consists of 26 exons and encodes the protein containing 12 putative transmembrane domains with long intracellular amino and carboxy termini. Most of the abnormalities identified in GS were missense mutations, distributed throughout the TSC gene without a hot spot. A 42-year-old Japanese man was introduced for close examination of hypokalemia. In renal clearance studies using furosemide or thiazide, chloride clearance was increased after furosemide but not after thiazide administration. Furthermore, the distal fractional chloride reabsorption was dramatically decreased by furosemide but not thiazide administration, suggesting a defect in the distal tubule. We then analyzed the TSC gene to confirm the diagnosis of GS, and identified a novel G to T mutation at the acceptor splice site preceding exon 14, resulting in disruption of a conventional 3'AG consensus splice site. Abnormal splicing by this mutation is predicted to cause the formation of truncated TSC with a partial deletion of the transmembrane domain, which will loose the function of transporter. In conclusion, we have identified a unique novel splice site mutation of the TSC gene in GS. The predicted structure of this mutant TSC can conceivably cause an impairment of the transporter activity and thereby be responsible for the development of GS in our patient.

Hormonal regulation of the human ghrelin receptor gene transcription.

The aim of this study is to clarify the hormonal regulation of the human ghrelin receptor gene expression in GH(3) cells transfected with our previously cloned 5'-flanking region inserted into a luciferase reporter vector. Phorbor 12-tetradecanoate 13-acetate (TPA) with simultaneous addition of Bay K8644 mimicking ghrelin action caused a significant inhibition of the luciferase activity through the ghrelin receptor gene upstream proximal to -669 but not to -608 base pairs (bp). Glucocorticoid caused a weak but significant inhibition of the luciferase activity through the ghrelin receptor gene upstream proximal to -531 but not to -475 bp. Electrophoretic mobility shift assay resulted in binding of oligonucleotides between -669 and -640 bp, and between -520 and -491 bp to GH(3) cell nuclear proteins unlike AP(2) or glucocorticoid receptor. These results suggest that both TPA/Bay K8644 and glucocorticoid downregulate human ghrelin receptor gene expression through the transcriptional mechanism involving some nuclear factors.

Cloning and characterization of the 5'-flanking region of the human prolactin-releasing peptide receptor gene.

Recently a novel peptide which specifically stimulates the secretion of prolactin (PRL) was found and named PRL-releasing peptide (PrRP). To evaluate the regulation of human (h) PrRP-receptor (PrRP-R) gene expression, we cloned the 5'-flanking region of the hPrRP-R gene and determined the nucleotide sequence of 4.0 kilobase pairs (kb) upstream from the translation start site. Analysis of the hPrRP-R transcripts by means of 5'-rapid amplification of cDNA ends suggested that the hPrRP-R gene had multiple transcription start sites between -429 and -365 from the translation start site. There is no typical TATA or CAAT but a GC box and putative binding sites for several transcription factors including Pit-1 and pituitary homeobox 1 (Ptx1). However, transient transfection studies using a luciferase reporter gene demonstrated that 5'-flanking region exerts promoter activity in several non-pituitary cell lines as well as in GH(3) cells. The GC box located from -467 to -457 was identified as an important region for the basal expression of the hPrRP-R gene. Knowledge of the promoter region of the hPrRP-R gene, which was obtained in the present study, will facilitate the clarification of its transcriptional regulation.

Multifocal fibrosclerosis as a possible cause of panhypopituitarism with central diabetes insipidus.

Multifocal fibrosclerosis denotes a combination of similar fibrous disorders occurring at different anatomical sites. We encountered a 53-year-old male patient with orbital pseudotumor, chronic paranasal sinusitis, fibrous nodules of the lungs, intracranial pachymeningitis, and panhypopituitarism with central diabetes insipidus (DI) as a possible manifestation of multifocal fibrosclerosis. It has been reported that intracranial pachymeningitis or orbital pseudotumor associated with multifocal fibrosclerosis could invade the sella turcica causing a variety of anterior and/or posterior pituitary dysfunctions. In our case, intracranial pachymeningitis apparently involved the pituitary stalk and gland. Isolated gonadotropin deficiency, in addition to central DI, preceded panhypopituitarism. Although panhypopituitarism with central DI due to multifocal fibrosclerosis is quite rare and only one case has ever been reported, this systemic fibrotic disorder can be a possible cause of panhypopituitarism with central DI.

Cloning and characterization of the 5'-flanking region of the human growth hormone-releasing hormone receptor gene.

We cloned the 5'-flanking region of the human growth hormone-releasing hormone receptor (GHRH-R) gene and determined the nucleotide sequence of 2.7 kilobases upstream from the translation start site. RNase protection analysis showed the major transcription start site is 122 base pairs upstream from the translation start site. The 5'-end of the longest product of 5'-rapid amplification of cDNA ends was close to the site. There were no typical TATA homologies but several putative regulatory elements including Pit-1-binding site-like element. Transient transfection studies using a luciferase reporter gene demonstrated that 5'-flanking region had promoter activity in GH3 cells (derived from rat pituitary tumor) but not in nonpituitary cells, BeWo and HeLa cells. However, co-transfection of Pit-1 expression vector increased luciferase activity in BeWo cells. Deletion study showed that the regions from -310 to -130 and from -130 to -120 were important for the GHRH-R gene expression in GH3 cells, although the latter contributed less to the gene expression. In BeWo cells co-transfected with Pit-1 expression vector, the region from -310 to -130 was essential for the Pit-1-dependent expression of GHRH-R gene. The region from -310 to -120 has two putative Pit-1-binding sites, P1 and P2, located from -129 to -123 and from -171 to -160, respectively. Both mobility shift assay and DNase-I footprint analysis showed that P2 had much higher Pit-1 binding affinity than P1. Mutation of P2 decreased GHRH-R gene expression in GH3 cells. These findings were consistent with the results that the region from -310 to -130 is an important element for Pit-1-dependent expression of GHRH-R gene.

Cloning and characterization of the 5'-flanking region of the human growth hormone secretagogue receptor gene.

Recently, the growth hormone secretagogue receptor (GHS-R) cDNA has been isolated from the pituitary and hypothalamus. To evaluate the regulation of human (h) GHS-R gene expression, we cloned the hGHS-R gene containing the 5'-flanking region of 0.6-2.9 kilobase pairs. Analysis of the hGHS-R transcripts with 5'-rapid amplification of cDNA ends suggested that the putative transcription initiation site was approximately -453 base pairs upstream of the translation initiation site (+1). There is no typical TATA, CAAT, or GC box but an initiator-like sequence and putative binding sites for several transcription factors around the putative transcription start site. The 5'-flanking region inserted into a luciferase reporter vector had promoter activity in GH3 cells but had activity indistinguishable from background in HeLa or EP1 cells. The hGHS-R promoter activity in GH3 cells increased by deletion of nucleotides from -1224 to -734, whereas it was decreased by further deletion from -734 to -608. Knowledge of the promoter region of the hGHS-R gene will facilitate elucidation of its transcriptional control.