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Pendred syndrome (PS) is an autosomal recessive disease that is characterized by congenital sensorineural hearing loss, goiter, and a partial iodine organification defect. In this study, we characterized the thyroid status and identified mutations in the SLC26A4 gene in Chinese subjects with PS. We evaluated 7 unrelated Chinese subjects who had PS. Biochemical analysis, formal audiogram, ultrasonography of the thyroid gland, perchlorate discharge test, computerized tomography scan of the vestibular aqueducts, and DNA sequence analysis of SLC26A4 were performed. Levels of thyroid hormones were essentially normal in all patients: 2 patients had goiters and/or elevated serum thyroglobulin levels, whereas 2 other patients had positive thyroid antibodies and a positive perchlorate discharge test. We identified SLC26A4 gene mutations in 6 of 7 probands and their affected relatives. The affected subjects in family I was compound heterozygous for 2 missense mutations: a mutation in exon 9 (1079C>T) that resulted in the replacement of alanine by valine at codon 360 (A360V) and a mutation in exon 19 (2168A>G) that resulted in the replacement of histidine by arginine at codon 723 (H723R). The affected subjects in families II and III all were homozygous for a mutation in intron 7. The probands IV and V were compound heterozygotes for the mutation in intron 7 and in exon 19, and the proband VI was compound heterozygous for the intron 7 mutation and a missense mutation in exon 12 (1343C>T) that resulted in the replacement of serine by leucine at codon 448 (S448L). One novel mutation was identified (A360V). We identified biallelic mutations in the SLC26A4 gene in 6 of 7 probands with PS in Taiwan, including a novel missense mutation. The mild thyroid dysfunction in these patients suggests that PS should be considered in all patients with congenital or early-onset hearing impairment.

The selective intra-arterial calcium stimulation test has greatly facilitated the precise regionalization of insulinomas smaller than 2 cm, which noninvasive techniques (ultrasound [US], computed tomography [CT], magnetic resonance imaging [MRI]) often fail to localize. This study examined not only the role of the test in the localization of insulinomas, but also the responsiveness of 3 beta-cell peptides (insulin, C peptide, and proinsulin) and their relationship to the degree of differentiation of the tumor cells, using percentage decrease of both proinsulin/insulin (P/I) and proinsulin/C peptide (P/C) ratios after stimulation as indices. Ten consecutive surgically proven insulinoma patients each received an injection of calcium into the arteries supplying the pancreas after standard selective angiography and beta-cell peptide levels were measured in samples taken from the right hepatic vein before and 30, 60, 90, 120, and 180 seconds after each injection prior to operation. After surgery, the expressions of the calcium sensing receptor (CaSR) on the resected tumors were assessed by immunohistochemistry. Intra-arterial calcium stimulation with sampling either for insulin or for C peptide correctly predicted the site of insulinoma in 8 of 9 patients or in 7 of 8 patients if the 2 big malignant insulinomas were excluded; thus, the detection rate of this test was 89% and 88%, respectively. Calcium administration stimulated a marked and prompt release of insulin and C peptide simultaneously. Both peaked within 30 to 60 seconds, then declined gradually thereafter, remaining above the baseline at 180 seconds. The magnitude of increase correlated well with the corresponding percentage decrease of P/I and P/C ratios. The response of proinsulin was much less. Immunohistochemistry demonstrated variable membraneous staining for CaSR in normal pancreatic islets and in about 9% of the total normal beta cells, whereas staining in tumor cells was only minimally detectable. We conclude that selective intra-arterial calcium stimulation with hepatic venous sampling either for insulin or for C peptide is a highly sensitive method for the preoperative localization of small insulinomas. Calcium injection stimulates a brisk response of insulin, C peptide, and proinsulin simultaneously and the magnitude of increase of both insulin and C peptide appears to be correlated well with the degree of differentiation of the tumor cells. The exact mechanism by which calcium provokes the release of beta-cell peptides is less clear and whether the CaSR is involved in the mechanism of its action requires further study.

The exchange of cholesterol ester (CE) between lipoproteins occurs through the action of cholesterol ester transfer protein (CETP). The human CETP gene is composed of 16 exons encompassing 25 kbp on chromosome 16q13. The objective of this study was to determine whether a mutation in the CETP gene accounted for severe hyperalphalipoproteinemia in an 80-year-old subject. As a secondary objective, we also investigated the allelic frequency of D442G and Int14A mutation in 224 random Han Chinese subjects. DNA sequence analysis of the CETP gene in the patient revealed a peculiar nucleotide pattern in intron 1. To determine whether this peculiarity results in abnormally spliced mRNA, we used reverse-transcriptase polymerase chain reaction (RT-PCR) to amplify and sequence the patient's cDNA using CETP-specific primers that spanned this splice junction. Both the wild-type and mutant cDNA were detected, and the mutant cDNA showed that its 5'-splice site shifted 4 nucleotides upstream. This change results in a frame-shift and premature termination at amino acid residue 22, and thus predicts a markedly truncated protein product. Although this patient did not have either the D442G or Int14A allele, we found that the allelic frequency of D442G in 224 subjects was 4.46%. No subjects had the Int14A allele. In conclusion, a novel intron 1 splice site mutation in the CETP gene in 1 patient with hyperalphalipoproteinemia and D442G allelic frequency of 4.46% was found among a normal population in Taiwan.