Expression of naturally occurring variants in the muscle glycogen synthase gene.
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Biomedical subjects
Publications and source records attributed to K Nanjo.
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Non-insulin dependent diabetes mellitus (NIDDM) is a heterogeneous disorder and both genetic and nongenetic factors are associated with the development of diabetes. Until now five genes (HNF-4 alpha, glucokinase, HNF-1 alpha, IPF-1 and HNF-1 beta), whose mutation can result in MODY, insulin and insulin receptor genes, and mitochondria DNA have been reported to be responsible for diabetes. Furthermore the mutations in some genes which work for insulin secretion or action also have been reported. This review discusses our current knowledge of these NIDDM susceptibility genes.
Insulin is synthesized in the pancreatic beta cell as a larger precursor molecule proinsulin which is converted to insulin and C-peptide by the concerted action of prohormone convertase 2 (PC2), prohormone convertase 3 (PC3) and carboxypeptidase E (CPE). One of the features of non-insulin-dependent diabetes mellitus (NIDDM) is an elevation in the proinsulin level and/or proinsulin/insulin molar ratio suggesting that mutations in these three proinsulin processing enzymes might contribute to the development of NIDDM. The identification of a mutation in the CPE gene of the fat/fat mouse which leads to marked hyperproinsulinaemia and late-onset obesity and diabetes is consistent with a possible role for mutations in CPE in the development of diabetes and obesity in humans. In order to test this hypothesis, we have isolated and characterized the human CPE gene and screened it for mutations in a group of Japanese subjects with NIDDM and obesity. The human CPE gene consists of 9 exons spanning more than 60 kb. Primer extension analysis identified the transcriptional start site at -141 bp from the translational start site. Single strand conformational polymorphism analysis and nucleotide sequencing of the promoter and entire coding region of the CPE gene in 269 Japanese subjects with NIDDM, 28 nondiabetic obese subjects and 104 nonobese and nondiabetic controls revealed three nucleotide changes, a G-to-T substitution at nucleotide -53, a G-to-A substitution at nucleotide -144 (relative to start of transcription) in the promoter region and a silent G-to-A substitution in codon 219. None of the nucleotide substitutions were associated with NIDDM or obesity. Thus, genetic variation in the CPE gene does not appear to play a major role in the pathogenesis of NIDDM or obesity in Japanese subjects.
Malignant mesothelioma is a clinically aggressive tumor and has a poor prognosis; therefore, the selection of therapeutic strategies is important to improve the prognosis. Two patients with intraperitoneal malignant mesothelioma received combination therapy as follows: (1) case-oriented chemotherapy according to the results of a chemosensitivity test, and (2) adoptive immunotherapy using cytotoxic T lymphocytes (CTL). The chemosensitivity test was assessed by an MTT colorimetric assay. CTL was generated by a mixed culture with autologous tumor cells, and activated by immobilized anti-CD3 monoclonal antibody and interleukin-2. The MTT assay indicated that cisplatin and adriamycin were sensitive drugs in both patients, and they thus received the case-oriented chemotherapy according to the MTT assay. The activated CTL exhibited a high cytotoxicity against autologous malignant mesothelioma cells, and were transferred intraperitoneally. The patients were controllable for ascites, and the tumor masses gradually vanished (partial response). Chemoimmunotherapy is thus considered to be an effective treatment for intraperitoneal malignant mesothelioma, especially to improve the quality of life.
We report a sporadic case of Albright's hereditary osteodystrophy (AHO)-like syndrome with several endocrinopathies. A 37-yr-old woman had an appearance of AHO but did not have renal PTH resistance. Her case was complicated by non-insulin-dependent diabetes mellitus with severe insulin resistance, central diabetes insipidus, and hyposecretion of GH. Most patients with AHO are found in a family of pseudohypoparathyroidism type-Ia and have a heterozygous mutation that inactivates the alpha-subunit of Gs (Gs alpha), the stimulatory regulator of adenylyl cyclase. Some sporadic cases occur in which patients with phenotype similar to AHO have a deletion of chromosome 2q37. However, in this patient, both the Gs alpha gene structure and the biological activity were normal. In addition, chromosome analysis revealed a normal pattern with no visible deletion of chromosome 2q37. Our findings suggest that one or more other factors may be involved in the pathogenesis of AHO-related disease.
Prohormone convertase 2 (PC2) is a member of a family of mammalian subtilisin-like endoproteases that are involved in the processing of prohormones, neuropeptides and many other precursor derived proteins. The expression of PC2 is restricted to neuroendocrine tissues such as pancreatic islets, the pituitary and the brain. To understand the regulation of the PC2 gene, we cloned and characterized the promoter region of the mouse PC2 gene. The transcriptional start site of the mouse PC2 gene is identical to that of the human. There is 79% identity in the sequences of the promoter regions between the mouse and human PC2 genes. The mouse PC2 gene, like the human, does not have a TATA-like motif in the region just upstream of the start of the transcription. Studies with promoter-reporter gene, chloramphenicol acetyltransferase (CAT), constructs showed that the region from -400 to -170 bp was necessary for high level expression of the mouse PC2 gene in the betaTC-3 insulinoma cells.
We report a 31-year-old woman who developed myopathy and neuropathy during pregnancy. She was diagnosed as having mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS). A T-to-C transition mutation at nucleotide position 3271 was detected in the mitochondrial gene. Her symptoms subsided spontaneously and she delivered a male infant at 38 weeks of gestation. Prior reports on mitochondrial diseases with pregnancy are very rare, probably because of the early onset of the disease. The metabolic changes during pregnancy increase the stress on the mitochondrial function, particularly in patients with impaired mitochondrial function. Therefore pregnancy can aggravate mitochondrial diseases.
A 26-year old man was admitted because of acute abdominal pain. He had received an allogeneic bone marrow transplant (BMT) for aplastic anemia 6 months before. All physical, laboratory, roentgenographic, and ultrasonographic studies were performed but nondiagnostic. On the fourth hospital day the patient developed visual disturbance and on the following day skin eruption appeared. Laboratory findings revealed severe liver dysfunction. We diagnosed this case as varicella-zoster virus (VZV) infection with visceral dissemination. Antiviral therapy with acyclovir was initiated and abdominal pain markedly reduced and visual acuity was recovered after 4 days. In case of VZV infection, acute abdominal pain prior to skin eruptions is rare. However in such cases the patients are highly fatal due to visceral dissemination. Antiviral therapy begun before visceral dissemination of VZV is highly effective in preventing serious disease, whereas it is less effective after dissemination. We consider that early diagnosis and treatment of VZV infection is necessary for BMT recipients who are undergoing immunosuppressive therapy.
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The preventive effects of combined or separate treatment for 10 weeks with an aldose reductase inhibitor, epalrestat (50 mg/kg/day), and a vasodilator, cilostazol (30 mg/kg/day), on nerve conduction deficits and morphometric alterations were examined in streptozotocin-induced diabetic rats. The average motor nerve conduction velocities (MNCV) in the tail nerve of the untreated diabetic (DM) group, the group treated with epalrestat (ES), the group treated with cilostazol (CZ), the group with both agents together (ES&CZ), and the normal control group were 34.7, 37.7, 39.3, 39.0 and 42.1 m/s, respectively. All treatments partially but significantly prevented a reduction in MNCV. The MNCV in the ES&CZ group was almost the same as in the CZ group. In a morphometric study of the sural nerve, the DM group showed a reduction in the average diameter of myelinated fiber and in occupancy (percentage of the fascicular area occupied by myelinated fibers), and a shift in the diameter-frequency histogram to smaller diameters. Only the CZ group showed evidence of a partial but significant preventive effect on the decrease in occupancy. In the CS and ES&CZ groups, there was a significant tendency away from the shift of histograms to smaller diameters. The ES&CZ group did not show any fewer morphometric changes than the CZ group. Thus, there was no synergism between the effects of epalrestat and cilostazol on the development of experimental diabetic neuropathy. This finding may provide a useful clue to the mechanisms of action of ES and CZ in diabetic neuropathy.
Muscle glycogen synthase (GYS1) is a key enzyme of non-oxidative pathway of glucose metabolism that has been reported to be related to insulin resistance in non-insulin-dependent diabetic (NIDDM) patients. We scanned the GYS1 gene for mutation by single strand conformational polymorphism in 244 non-obese Japanese NIDDM patients and 181 non-diabetic control subjects, and found two missense mutations; Met to Val at position 416 in the exon 10 (M416V) and Pro to Ala at position 442 in the exon 11 (P442A). The P442A mutation was found in only one NIDDM patient treated with sulfonylureas. On the other hand, the M416V mutation was widely found in the Japanese population. The mutant allele frequency in the NIDDM patients (13.7%) was slightly higher but not statistically significant compared with that in non-diabetic subjects (9.7%). However, the insulin sensitivity index [SI: x 10(-4) x min(-1) x (microU/ml)(-1)] estimated by Minimal Model analysis in the NIDDM patients carrying the M416V mutation was significantly lower than that in those without the mutation (1.18 +/- 0.27, n = 21 vs 2.20 +/- 0.20, n = 60, mean +/- SEM, p < 0.01). Glucose effectiveness, age, body mass index, and levels of glycated haemoglobin and serum lipids were not significantly different between the two groups. The same trend could be seen in non-diabetic subjects (SI: 3.70 +/- 0.46, 9 subjects with the mutation vs 5.94 +/- 0.66, 19 subjects without the mutation, p < 0.05). These findings indicate that the M416V mutation of the GYS1 gene is one of the factors contributing to the insulin resistance in the Japanese population and may play some role in the pathogenesis of NIDDM.
Islet amyloid polypeptide (IAPP) was isolated from islet amyloid deposits in patients with insulinoma and pancreatic islets of non-insulin-dependent diabetes mellitus (NIDDM) and several reports suggested that it may contribute to the development of NIDDM. IAPP is mainly expressed and synthesized in pancreatic B cells and cosecreted with insulin, so analysis of the transcriptional regulation of the IAPP gene would be helpful for the elucidation of pancreatic B cell specific gene expression. The mouse IAPP gene spans about 5.8 kb and, like the human and rat genes, it consists of three exons, and analysis of the promoter/enhancer activity of mouse IAPP gene reveals the region from -171 to -87 bp to be essential. Within this region, an E-box like sequence, CACCTG (-122 to -117 bp), and a TAAT-box like sequence, TTAATG (-139 to -134 bp), are thought to be important. The disruption of each sequence resulted in a severe decrease in promoter activity, although the decrease was less in the disruption of the E-box than that of TAAT-box like sequence, suggesting the latter is more important for IAPP gene transcription. Like the rat IAPP gene, the CCAAT-box, which does not exist in the human gene, was identified in the mouse gene, indicating the possibility of species difference in the IAPP gene transcriptional mechanism. An enhancer-like activity was also identified within intron 1, although further elucidation is necessary.