Tolbutamide stimulates fructose-2, 6-bisphosphate formation in perfused rat liver.

Effect of tolbutamide on liver fructose-2,6-bisphosphate (F-2,6-P2) was examined in isolated perfused rat liver in situ with a flow-through method. Tolbutamide (1 mM) gradually increased liver F-2,6-P2 level from 7.4 +/- 1.6 to 21.2 +/- 1.6 pmol/mg wet wt for 20 min perfusion. The increase of liver F-2,6-P2 induced by tolbutamide was dose dependent and was significantly observed at 10 min perfusion. The maximum plateau level of F-2,6-P2 induced by 16.7 mM glucose was further increased with 1 mM tolbutamide. Glucagon (10(-11) M) decreased the elevated level induced by 16.7 mM glucose, but this effect was completely inhibited with 2 mM tolbutamide. Cyclic AMP level of the liver throughout the perfusion with tolbutamide did not change. Carboxytolbutamide or gliclazide perfusion did not change significantly the liver F-2,6-P2 level; however, the results suggest that tolbutamide may increase the liver F-2,6-P2 level by affecting the phosphorylation state of fructose-6-phosphate, 2-kinase/fructose-2,6-bisphosphatase through cyclic AMP-dependent protein kinase, resulting in the stimulation of glycolysis and the inhibition of gluconeogenesis in the liver. Thus, the extrapancreatic action and the mechanism of action of different sulfonylureas may differ.

Linkage analysis of GLUT1 (HepG2) and GLUT2 (liver/islet) genes in familial NIDDM.

Familial NIDDM probably results from combined inherited defects of insulin secretion and action. Members of the facilitative glucose transporter family are strong candidates for both defects, and RFLPs for both GLUT1 (erythrocyte) and GLUT2 (liver/islet) genes have been associated with NIDDM in some populations. To test the hypothesis that GLUT1 and GLUT2 mutations contribute to the inherited predisposition to NIDDM, we examined linkage of these loci with NIDDM in 18 large Utah white pedigrees (two and three generation) ascertained for > or = 2 NIDDM siblings. We used two RFLPs detected with Xba1 and Stu1 for the GLUT1 transporter. For the GLUT2 (liver/beta-cell) transporter gene, we used an RFLP detected with EcoR1 and a highly polymorphic (6-allele) dinucleotide (microsatellite) repeat. Analysis was performed with the MLINK program of the LINKAGE package. We tested four models for each locus: dominant and recessive, with IGT alternately considered as unknown affection status, or affected if IGT was diagnosed < or = 45 yr of age and unknown if > 45 yr. Disease gene frequencies were chosen to give approximate disease prevalence in American whites (q = 0.03, dominant; q = 0.25, recessive). Linkage of GLUT1 and NIDDM was strongly and significantly rejected under all models, with total (pooled) LOD scores of -5.7 to -8.9, indicating > 500,000:1 odds against linkage. Pooled LOD scores were significantly negative (< -2.0, or 100:1 odds against linkage) to a recombination fraction of > 5%. No heterogeneity was apparent. Analysis of GLUT2 gave similar results, with LOD scores of < -4.0 under each model, indicating at least 10,000:1 odds against linkage.(ABSTRACT TRUNCATED AT 250 WORDS)

Tolbutamide inhibits cAMP-dependent phosphorylation of liver 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase.

The activity of a bifunctional enzyme, liver 6-phosphofructo-2-kinase (PFK-2)/fructose-2,6-bisphosphatase (F-2,6-Pase), which regulates the level of liver fructose-2,6-bisphosphate (F-2,6-P2), the most potent activator of PFK, is modulated by its phosphorylation rate mainly catalyzed by cAMP-dependent protein kinase A (PKA). To elucidate the action mechanism of sulfonylurea on liver F-2,6-P2 production, effects of tolbutamide on PKA-dependent phosphorylation of purified liver PFK-2/F-2,6-Phase protein and on kinase and phosphatase activities of the purified enzyme were examined in vitro. The purified enzyme was phosphorylated in the presence of the catalytic subunit of PKA, and tolbutamide inhibited the enzyme phosphorylation catalyzed by PKA in a dose-dependent manner. By adding the same dosages of tolbutamide used in the phosphorylation experiment, reduced activity of PFK-2 and increased activity of F-2,6-Pase in the presence of PKA were restored to the levels observed in the absence of PKA. On the other hand, carboxytolbutamide, an inactive metabolite of tolbutamide, had little effect on enzyme phosphorylation and activity. Our results indicate that tolbutamide inhibits a phosphorylation of the liver PFK-2/F-2,6-Pase catalyzed by PKA along with an activation of PFK-2 and an inactivation of F-2,6-Pase, leading to liver F-2,6-P2 production.

Polymorphisms of HepG2/erythrocyte glucose-transporter gene. Linkage relationships and implications for genetic analysis of NIDDM.

To assess the contribution of the HepG2/erythrocyte glucose-transporter (HepG2 GT) gene to the inherited susceptibility to non-insulin-dependent diabetes mellitus (NIDDM), cDNA and genomic probes were used to search for restriction-endonuclease polymorphisms at this locus. Analysis of DNA from 16 unrelated Black American individuals with 19 enzymes and as many as six different probes, defined four polymorphisms over a 45-kilobase region. Nucleotide diversity (pi = 0.006) was low relative to that at other loci, with an average of 1 in 1700 base pairs different between two chromosomes at this locus. The observed combined heterozygosity for these four sites was 0.69, which indicates that the markers at this locus could be useful for linkage analysis in families. Linkage-disequilibrium values between the four polymorphisms were evaluated by pairwise analysis and extended haplotypes. Calculating pairwise associations by the disequilibrium statistic delta or by another measure of disequilibrium, D' (the maximum likelihood of disequilibrium, which is less dependent on frequency), significant linkage disequilibrium could not be demonstrated. However, the frequencies of the observed extended haplotypes were shown to differ (chi 2 = 9.1, df = 2, P less than 0.025) from predicted frequencies if the sites were in linkage equilibrium in Blacks. The frequencies of these four polymorphisms were determined in Black nondiabetic (n = 44) and NIDDM (n = 63) subjects. Neither the allelic nor genotypic frequencies of the polymorphisms differed between the two groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Polymorphisms of GLUT2 and GLUT4 genes. Use in evaluation of genetic susceptibility to NIDDM in blacks.

The liver/islet (GLUT2) and muscle/adipose tissue (GLUT4) glucose-transporter gene products, membrane proteins that facilitate glucose uptake into cells, are important molecules for normal carbohydrate metabolism. Recent isolation of the genes encoding these proteins provides a means to assess the role of possible defects that might contribute to impaired glucose-stimulated insulin secretion or impaired insulin-mediated glucose uptake, both prominent phenotypic features of non-insulin-dependent diabetes (NIDDM). A GLUT2 cDNA clone was isolated from a human liver cDNA library to search for polymorphisms at this locus in American Blacks. Three highly polymorphic sites were identified, one of which (EcoRI-Hae III) appears to be due to an insertion and/or deletion of 200 base pairs of DNA. Significant linkage disequilibrium between these sites over approximately 30 kilobases of genomic DNA suggested that these polymorphisms could be in linkage disequilibrium with mutations at this locus if they exist. A GLUT4 cDNA clone was also utilized to search for polymorphisms at this locus, but only one previously described polymorphism was observed. GLUT2 and GLUT4 cDNA probes were used to evaluate DNA polymorphisms in genomic DNA from American Blacks with NIDDM. The allelic, genotypic, and haplotypic frequencies of the DNA polymorphisms at these loci did not differ from the frequencies in nondiabetic subjects. Because no associations with NIDDM were found, it appears unlikely that mutations at these loci contribute in a major way to the genetic susceptibility to NIDDM observed in American Blacks.

Polymorphic microsatellite repeat markers at the glucokinase gene locus are positively associated with NIDDM in Japanese.

To assess the possible role of glucokinase defects contributing to a genetic susceptibility to NIDDM in Japanese, allelic frequencies of two microsatellite repeat polymorphisms, one in the 3'-flanking region (GCK1) and the other in the 5'-flanking region (GCK2) of the human glucokinase gene, were analyzed in subjects with NIDDM and in nondiabetic control subjects. After typing 107 diabetic and 74 nondiabetic subjects, we found four GCK1 alleles (Z, Z2, Z4, Z6) and six GCK2 alleles (0, -4, -2, 2, 4, 8). The frequency distribution of GCK1 alleles was different between the two groups (P = 0.005), although not significant after correction for multiple comparisons. The Z4 allele was found more frequently in diabetic than in nondiabetic subjects (23 vs. 10%, P = 0.002). This was still significant after correction for multiple comparisons (P < 0.05). The frequency distribution of GCK2 alleles was not different between the two groups. However, the -2 allele was more common in diabetic than in nondiabetic subjects (P = 0.044), although not significant after adjusting for multiple comparisons. Clinical characteristics were compared between the diabetic subjects with Z4 and/or -2 allele and those without either of these two alleles. No differences were found in the age of diagnosis, positive family history, mode of therapy, current HbA1c, or daily urinary C-peptide immunoreactivity excretion between the two groups. We demonstrated a significant association between GCK1 and GCK2 alleles and NIDDM. The results indicate that the polymorphic alleles GCK1 and GCK2 could be genetic markers in NIDDM in Japanese, suggesting a relationship between glucokinase defects and the susceptibility to NIDDM in this population.

Troglitazone treatment increases plasma vascular endothelial growth factor in diabetic patients and its mRNA in 3T3-L1 adipocytes.

Troglitazone is one of the thiazolidinediones, a new class of oral antidiabetic compounds that are ligands of peroxisome proliferator-activated receptor-gamma. This study on vascular endothelial growth factor (VEGF), also known as vascular permeability factor, was prompted by our clinical observation that the characteristics of troglitazone-induced edema were very similar to those caused by vascular hyperpermeability. When Japanese diabetic patients were screened for plasma VEGF, we found levels to be significantly (P < 0.001) increased in troglitazone-treated subjects (120.1 +/- 135.0 pg/ml, n = 30) compared with those treated with diet alone (29.2 +/- 36.1 pg/ml, n = 10), sulfonylurea (25.8 +/- 22.2 pg/ml, n = 10), or insulin (24.6 +/- 19.0 pg/ml, n = 10). Involvement of troglitazone in increased VEGF levels was further supported by the plasma VEGF levels in five patients before treatment (20.2 +/- 7.0 pg/ml), after 3 months of troglitazone treatment (83.6 +/- 65.9 pg/ml), and 3 months after discontinuation (28.0 +/- 11.6 pg/ml). We further demonstrated that troglitazone, as well as rosiglitazone, at the plasma concentrations observed in patients, increased VEGF mRNA levels in 3T3-L1 adipocytes. VEGF is an angiogenic and mitogenic factor and is currently considered the most likely cause of neovascularization and hyperpermeability in diabetic proliferative retinopathy. Although increased VEGF may be beneficial for subjects with macroangiopathy and troglitazone is currently not available for clinical use, vascular complications, especially diabetic retinopathy, must be followed with great caution in subjects treated with thiazolidinediones.

Identification and functional analysis of sulfonylurea receptor 1 variants in Japanese patients with NIDDM.

The sulfonylurea receptor 1 (SUR1) is an essential regulatory subunit of the beta-cell ATP-sensitive K+ channel (K[ATP]). The possible role of SUR1 gene mutation(s) in the development of NIDDM remains controversial as both a positive association and negative linkage results have been reported. Therefore, we examined the SUR1 gene at the single nucleotide level with single strand conformation polymorphism analysis in 100 Japanese NIDDM patients. We identified a total of five amino acid substitutions and 17 silent mutations by examining all 39 exons of this gene. Two rare novel mutations, D811N in exon 20 and R835C in exon 21, were identified in the first nucleotide-binding fold (NBF), a functionally important region of SUR1, in one patient each, both heterozygotes. To analyze possible functional alterations, we reconstituted the mutant K(ATP) by coexpressing beta-cell inward rectifier (BIR) (Kir 6.2), a channel subunit of K(ATP), and mutant SUR1 in HEK293T and COS-7 cells. As demonstrated by the patch clamp technique and rubidium (Rb+) efflux studies, neither mutation alters the properties of channel activities. Two other rare missense mutations, R275Q in exon 6 and V560M in exon 12, were also identified. The R275Q substitution was not found in 67 control subjects, and V560M was present in three control subjects. Neither of these substitutions appeared to cosegregate with NIDDM in the probands' families. A previously reported S1370A substitution located in the second NBF was also common in the Japanese subjects (allelic frequency 0.37), and was found at an equal frequency in nondiabetic control subjects. In conclusion, SUR1 mutations impairing K(ATP) function do not appear to be major determinants of NIDDM susceptibility in Japanese.

The Pro12 -->Ala substitution in PPAR-gamma is associated with resistance to development of diabetes in the general population: possible involvement in impairment of insulin secretion in individuals with type 2 diabetes.

The allele frequencies for a Pro12-->Ala substitution in peroxisome proliferator-activated receptor-gamma differ among ethnic groups, and its relationship with diabetes and associated diseases is controversial. The prevalence of this polymorphism and its effects on clinical characteristics have now been evaluated with a large number of Japanese individuals with type 2 diabetes (n = 2,201) and normal control subjects (n = 1,212) recruited by 10 institutions located in seven different cities in Japan. The allele frequency for the Ala12 variant was significantly lower in the type 2 diabetic group than in the control group (2.39 vs. 4.13%, P = 0.000054). However, compared with subjects without the Ala12 variant, the diabetic subjects with this variant exhibited a significantly higher serum concentration of total cholesterol (P = 0.001), manifested a reduced capacity for insulin secretion as evaluated by homeostasis model assessment (P = 0.007), and tended to possess a higher level of HbA1c. These data suggest that the Ala12 variant is associated with a reduced risk for the development of diabetes in the general population, but that it may be also a risk factor for insulin deficiency and disease severity in individuals with type 2 diabetes.

Human glucokinase gene: isolation, structural characterization, and identification of a microsatellite repeat polymorphism.

The gene encoding human glucokinase (ATP:D-hexose 6-phosphotransferase, EC 2.7.1.1), a major component of glucose sensing in pancreatic islet beta-cells, was isolated and characterized. The gene was shown by Southern blotting to exist as a single copy in the genome which mapped to chromosome 7p. It contained 12 exons including two tissue-specific first exons, one active in islet beta-cells (1B), and the other active in liver (1H), and one optional cassette exon which was expressed as a minor form in the liver. Thus the three previously reported isoforms of glucokinase mRNA were the result of tissue-specific activation of separate liver and islet promoters and subsequent alternative splicing events. Eleven exons, including 1H and the optional cassette exon 2A, were scattered over 16 kilobase (kb) in the genome, while exon 1B was separated from the rest by at least 20 kb. Although the islet promoter was found to lack a TATA box, a major transcript from the islet promoter was mapped 486 nucleotides upstream of the translation initiation site. The presence in the islet glucokinase promoter of the potential control element GCCACCAG, a homology of the regulatory element present in both human insulin (GCCACCGG) and rat insulin (GCCATCTG) genes, implied a possible tissue-specific regulatory role of this element. The liver promoter was found to contain a TATA box-like sequence, and transcription was initiated predominantly at 168 nucleotides upstream of the translation initiation site of the major isoform. A new highly polymorphic microsatellite, composed of a compound imperfect dinucleotide repeat [GT]15[GA]8CA[GA]7CA[GA]3AA[GA]2, was mapped 6 kb upstream of islet exon 1. A polymerase chain reaction-based assay was developed, and seven different sized alleles were identified in American Blacks. The sequence information reported here, along with the new polymorphic marker, will make it possible to clarify the molecular basis of potential glucokinase defects in noninsulin-dependent diabetes mellitus patients and may further elucidate the nature of genetic susceptibility to the development of this common metabolic disease.

Sequence variations of the pancreatic islet/liver glucose transporter (GLUT2) gene in Japanese subjects with noninsulin dependent diabetes mellitus.

To assess the genetic susceptibility to noninsulin-dependent diabetes mellitus (NIDDM) in Japanese subjects, we investigated the role of GLUT2 gene defects in patients with NIDDM. When the allelic frequency of a simple tandem repeat polymorphism in the GLUT2 gene was compared, the allele with 155 base pairs was more common in NIDDM patients (n = 99) than in controls (n = 89; 5.1% vs. 0.6%; P = 0.0118, by Fisher's exact test), whereas this was not significant after the correction for multiple comparisons. To directly identify mutations, we then analyzed each of 11 exons by the polymerase chain reaction-single strand conformation polymorphism analysis in 60 NIDDM patients. We found 2 missense mutations in exon 3: CCC-->CTC (Pro68-->Leu) in 1 patient and ACT-->ATT (Thr110-->Ile) in 3 patients, all in the heterozygous state. These mutations were not found in 60 control subjects. To evaluate the significance of the Pro68-->Leu mutation, the family members of the proband were studied. The mutation did not appear to be associated with the disease or other clinical parameters including change in immunoreactive insulin/change in plasma glucose or oral glucose load. The other mutation (Thr110-->Ile) is known to be functionally insignificant. We identified 4 additional nucleotide changes, all of which appeared to be silent. We concluded that the mutations in the GLUT2 gene were not major determinants of genetic susceptibility to NIDDM in Japanese.

Donor leukocyte transfusions and discontinuation of immunosuppressants to achieve an initial remission after allogeneic bone marrow transplantation in a patient with primary refractory acute leukemia.

We present a female patient who received an allogeneic bone marrow transplantation for primary refractory Philadelphia-positive acute biphenotypic leukemia. Since leukemic blasts were persistently present in peripheral blood and bone marrow, in spite of the evidence for engraftment of male donor hematopoiesis, we performed donor leukocyte transfusions and discontinued immunosuppression. An initial complete remission was obtained 15 weeks after allogeneic bone marrow transplantation, and lasted for 24 weeks. We concluded that the prominent mechanism for the eradication of the refractory leukemic clone in the patient was the graft-versus-leukemia effect.

Effects of tolbutamide on fructose-2,6-bisphosphate formation and ketogenesis in hepatocytes from diabetic rats.

To assess the extrapancreatic action of sulfonylurea directly in the diabetic, effects of tolbutamide on hepatocyte fructose-2,6-bisphosphate (F-2,6-P2) formation and ketone production were investigated using isolated hepatocytes from streptozotocin (STZ)-induced diabetic rats. The basal level of hepatocyte F-2,6-P2 was significantly higher in diabetic rats within 2 weeks after STZ (40 mg/kg body weight) injection compared with that in the nondiabetic control group. Ultimately, a marked decrease in the F-2,6-P2 level was observed at 4 weeks after STZ administration (10% of the control). Although the addition of tolbutamide further increased the hepatocyte F-2,6-P2 level during the first week after STZ injection, no significant effect was observed after the second week and on from the initial STZ. Treatment of diabetes with insulin restored the stimulatory effect of tolbutamide on the hepatocyte F-2,6-P2 formation. Tolbutamide, independently of insulin treatment, lowered the ketone production of hepatocytes from diabetic rats. The present results indicate that insulin is necessary, in advance, for sulfonylurea to stimulate the liver F-2,6-P2 formation, while tolbutamide inhibition of hepatocyte ketone production is independent of insulin. These results provide further support for the role of sulfonylurea in regulating hepatic energy metabolism in the diabetic.

Granulocyte colony-stimulating factor (G-CSF) dependent hematopoiesis with monosomy 7 in a patient with severe aplastic anemia after ATG/CsA/G-CSF combined therapy.

We report a case of secondary myelodysplastic syndrome (MDS) with monosomy 7, which evolved from severe aplastic anemia (SAA) after long-term use of granulocyte colony-stimulating factor (G-CSF). A 36 year old female was admitted for detailed examination and treatment of pancytopenia. SAA was diagnosed based on hypoplastic bone marrow and a normal chromosome study. She was treated with anti-thymocyte globulin (ATG), ciclosporin A (CsA) and G-CSF, which resulted in gradual improvement of not only the myeloid but also the erythroid-megakaryocyte series. However, bone marrow dysplasia with monosomy 7 was observed after 7 months of a combination therapy of immunosuppressant and G-CSF, which prompted the discontinuation of G-CSF administration. Thereafter, bone marrow hypoplasia gradually progressed, resulting in a second aplastic crisis. During this process, the proportion of marrow cells showing monosomy 7 decreased, and the proportion with normal karyotype increased. Re-administration of G-CSF induced a trilineage, though dysplastic, hematological response; but the monosomy 7 positive population increased again. These observations indicated the presence of G-CSF dependent hematopoiesis associated with monosomy 7 in this patient. Although many G-CSF related MDS/AML cases with this leukemia-specific abnormal karyotype have been reported with emphasis on the harmful effects of G-CSF, G-CSF was useful even after the appearance of monosomy 7 as a means of avoiding life-threatening infection in this patient.

Possible mechanism of proteolysis for the extrapancreatic action of tolbutamide.

In order to assess the mode of the extrapancreatic action of the sulfonylureas, we evaluated the contribution of a proteolytic mechanism for sulfonylurea action by analyzing the effects of a protease inhibitor on insulin- or tolbutamide-stimulated liver fructose-2,6-bisphosphate (F-2,6-P2) formation using isolated rat hepatocytes. The F-2,6-P2 level in hepatocytes was significantly increased by the addition of insulin or tolbutamide. The stimulatory effect of insulin on the F-2,6-P2 formation was most significant when its level was reduced by the addition of 2 microM of forskolin. Insulin action on F-2,6-P2 formation was inhibited by the addition of a protease inhibitor, p-tosyl-L-arginine methyl ester hydrochloride (TAME). Tolbutamide (2 mM) significantly increased hepatocyte F-2,6-P2 level (P less than 0.01 vs the control level). In the presence of TAME, the stimulatory effect of tolbutamide was also suppressed. The present data suggest that a proteolytic mechanism is important in both insulin and tolbutamide action on the F-2,6-P2 formation, and it may be hypothesized that, like insulin, the chemical mediator of tolbutamide action is formed proteolytically.

[Clinical experience of chemotherapy with cefmetazole for severe infections accompanying malignant hematological disorders].

We made an attempt to treat with cefmetazole (CMZ) 25 patients who developed severe infectious diseases while suffering with granulocytopenia associated with the treatment of malignant hematological disorders. 1. Determination of bacteriological efficacy While 20 strains were isolated and identified from 15 patients, no significant bacteria were detected in 9 patients. Isolates obtained were: 5 strains of Enterococcus faecalis, 3 strains of Haemophilus influenzae, 2 strains of Staphylococcus epidermidis, 2 strains of Klebsiella oxytoca, 2 strains of Staphylococcus aureus, and 1 strain each of Neisseria sp., Pseudomonas maltophilia, Enterobacter sp., alpha-Streptococcus, beta-Streptococcus and Gram-positive cocci. Causative organisms were eradicated or markedly in 7 of the 15 patients from whom bacteria were isolated. Clinical findings, including fever, revealed that none of the patients, in whom bacteriological efficacy was determined to be poor, exhibited sufficient clinical response. E. faecalis was isolated from 4 of 6 patients bacteriologically determined to have no response. 2. As for 23 patients, who were found to be evaluable among the 25 patients, 8 (34.8%), 4 (17.4%), 4 (17.4%), and 7 (30.4%) demonstrated excellent, good, fair and poor responses, respectively, showing a 69.6% efficacy rate which indicates a sum of percentages of patients with excellent, good and fair responses. 3. While an efficacy rate of 100% was obtained for 3 patients with number of peripheral neutrophils less than 500/mm3 before the beginning of CMZ administration, only an efficacy rate of 66.7% was obtained for 15 patients with neutrophils more than 500/mm3.(ABSTRACT TRUNCATED AT 250 WORDS)

[Relationship between clinical efficiency of cefoperazone and the value of area under the time concentration curve in infectious diseases].

Clinical efficiency and side effects of cefoperazone (CPZ) against 40 infectious diseases in the field of internal medicine were studied. In addition, relationship between clinical efficiency and the value of area under the time concentration curve (AUC) was evaluated. It was possible to evaluate clinical responses in 36 cases of 40 infections; Responses were excellent in 15, good in 16, fair in 3 and poor in 2. An overall efficacy rate was 86.1%. A high dose of CPZ (2 g X 2/day) produced a higher efficacy rate than a low dose of the drug (1 g X 2/day) [95.8% (23/24 cases) vs. 66.7% (8/12 cases)] but the difference was not statistically significant. It was possible to evaluate bacteriological efficacy in 32 cases. Bacteria were eradicated in 29 (90.6%) and decreased in 3. The value of AUC in the high dose group was significantly higher than that in the low dose group. Values of AUC in cases of excellent or good clinical responses tended to be higher than values in cases of fair or poor responses. Side effects were noted in 4 cases, but they were not serious and improvements were observed without withdrawal of the drug except 1 case.

[Defects of candidate genes in Japanese NIDDM--glucose transporter gene(GLUT1 gene, GLUT4 gene)].

To assess the contribution of GLUT1 and GLUT4 genes to NIDDM susceptibility in Japanese population, we performed population studies using RFLP markers. We found the strong association between XbaI polymorphism at GLUT1 gene and NIDDM, but no association between KpnI polymorphism at GLUT4 gene and NIDDM. Based on these results, molecular scanning of GLUT1 gene was performed using SSCP and direct sequencing in Japanese population, to substantiate the gene defect predisposing to NDDM. Although silent mutations were found, the meaningful mutations within the coding regions were not demonstrated. Thus the positive association observed in population study may be spurious or due to the abnormalities in non-coding regions such as promoter or other regulatory elements at GLUT1 gene.