Genetic variation in the gene encoding calpain-10 is associated with type 2 diabetes mellitus.

Type 2 or non-insulin-dependent diabetes mellitus (NIDDM) is the most common form of diabetes worldwide, affecting approximately 4% of the world's adult population. It is multifactorial in origin with both genetic and environmental factors contributing to its development. A genome-wide screen for type 2 diabetes genes carried out in Mexican Americans localized a susceptibility gene, designated NIDDM1, to chromosome 2. Here we describe the positional cloning of a gene located in the NIDDM1 region that shows association with type 2 diabetes in Mexican Americans and a Northern European population from the Botnia region of Finland. This putative diabetes-susceptibility gene encodes a ubiquitously expressed member of the calpain-like cysteine protease family, calpain-10 (CAPN10). This finding suggests a novel pathway that may contribute to the development of type 2 diabetes.

Mutations in the hepatocyte nuclear factor-1alpha/MODY3 gene in Japanese subjects with early- and late-onset NIDDM.

Recent studies have shown that mutations in the hepatocyte nuclear factor (HNF)-1alpha gene are the cause of maturity-onset diabetes of the young type 3 (MODY3). We have screened 193 unrelated Japanese subjects with NIDDM for mutations in this gene: 83 with early-onset NIDDM (diagnosis at <30 years of age) and 110 with late-onset NIDDM (diagnosis > or = 30 years of age). All of the members of the latter group also had at least one sibling with NIDDM. The 10 exons, flanking introns, and promoter region were amplified using polymerase chain reaction and were sequenced directly. Mutations were found in 7 of the 83 (8%) unrelated subjects with early-onset NIDDM. The mutations were each different and included four missense mutations (L12H, R131Q, K205Q, and R263C) and three frameshift mutations (P379fsdelCT, T392fsdelA, and L584S585fsinsTC). One of the 110 subjects with late-onset NIDDM was heterozygous for the missense mutation G191D. This subject, who was diagnosed with NIDDM at 64 years of age, also had a brother with NIDDM (age at diagnosis, 54 years) who carried the same mutation, suggesting that this mutation contributed to the development of NIDDM in these two siblings. None of these mutations were present in 50 unrelated subjects with normal glucose tolerance (100 normal chromosomes). Mutations in the HNF-1alpha gene occur in Japanese subjects with NIDDM and appear to be an important cause of early-onset NIDDM in this population. In addition, they are present in about 1% of subjects with late-onset NIDDM.

Beta-cell transcription factors and diabetes: no evidence for diabetes-associated mutations in the hepatocyte nuclear factor-3beta gene (HNF3B) in Japanese patients with maturity-onset diabetes of the young.

Mutations in the transcription factors hepatocyte nuclear factor (HNF)-4alpha and -1alpha, insulin promoter factor-1, and HNF-1beta are the causes of four forms of maturity-onset diabetes of the young (MODY1 and 3-5, respectively). The winged-helix transcription factor HNF-3beta has been implicated in the regulation of expression of each of these MODY genes, suggesting that mutations in the HNF-3beta gene (HNF3B) may also cause MODY. We have tested this hypothesis by screening a panel of 57 unrelated Japanese subjects with a clinical diagnosis of MODY for mutations in HNF3B. This analysis revealed four frequent polymorphisms that were not associated with MODY, including one in the promoter region (-213A/G), two silent mutations in the codons for Ala 97 (291C/T) and Gly 279 (837A/G), and one in the 3'-untranslated region (1424C/T). Two rare substitutions in the 5'-untranslated region, -156C/T and -67A/C, were found in a heterozygous state in two subjects, and two subjects were heterozygous for putative missense mutations, S109N (326G > A) and A328V (983C>T). The two missense mutations were not found in 106 normal chromosomes from nondiabetic subjects. It was not possible to test for co-segregation of these mutations with diabetes and thus, it is unclear whether or not these mutations can cause MODY. The results of our study suggest that mutations in HNF3B are not a common cause of MODY in Japanese subjects.

Genetic variation in the hepatocyte nuclear factor-3beta gene (HNF3B) does not contribute to maturity-onset diabetes of the young in French Caucasians.

Mutations in genes encoding hepatocyte nuclear factor (HNF) are responsible for three of the five subtypes of maturity-onset diabetes of the young (MODY). This observation and molecular studies indicate that the HNF network is required for normal function of pancreatic beta-cells. This suggests that transcription factors involved in this complex network are candidates for genetic defects in MODY. Because the HNF-3beta gene is implicated in this network, we screened it for mutations in 21 probands of French ancestry with clinical diagnosis of MODY and early-onset type 2 diabetes. All of the five known MODY genes, HNF-4alpha, glucokinase, HNF-1alpha, HNF-1beta, and IPF1, were previously excluded as being the cause of diabetes in these families. By direct sequencing, we identified two transitions, an A-to-G at position -213 and a C-to-T at position -63 in the promoter and exon 1, respectively, of the HNF-3beta gene. A G-to-C transversion at position +32 in the intron 1 and three transitions, C-to-T at position 291, A-to-G at position 837, and G-to-A at position 1188 in the exon 3, resulting in noncoding mutations Ala97Ala, Gly279Gly, and Gln396Gln, respectively, were also identified. The allele frequencies were not significantly different between a control group and MODY probands. Familial segregation studies and linkage analysis showed that genetic variation in the HNF-3beta gene is unlikely to be the cause of early-onset type 2 diabetes in these Caucasian families.

Organization and partial sequence of the hepatocyte nuclear factor-4 alpha/MODY1 gene and identification of a missense mutation, R127W, in a Japanese family with MODY.

Hepatocyte nuclear factor-4 alpha (HNF-4 alpha) is a member of the nuclear receptor superfamily, a class of ligand-activated transcription factors. A nonsense mutation in the gene encoding this transcription factor was recently found in a white family with one form of maturity-onset diabetes of the young, MODY1. Here, we report the exon-intron organization and partial sequence of the human HNF-4 alpha gene. In addition, we have screened the 12 exons, flanking introns and minimal promoter region for mutations in a group of 57 unrelated Japanese subjects with early-onset NIDDM/MODY of unknown cause. Eight nucleotide substitutions were noted, of which one resulted in the mutation of a conserved arginine residue, Arg127 (CGG)-->Trp (TGG) (designated R127W), located in the T-box, a region of the protein that may play a role in HNF-4 alpha dimerization and DNA binding. This mutation was not found in 214 unrelated nondiabetic subjects (53 Japanese, 53 Chinese, 51 white, and 57 African-American). The R127W mutation was only present in three of five diabetic members in this family, indicating that it is not the only cause of diabetes in this family. The remaining seven nucleotide substitutions were located in the proximal promoter region and introns. They are not predicted to affect the transcription of the gene or mRNA processing and represent polymorphisms and rare variants. The results suggest that mutations in the HNF-4 alpha gene may cause early-onset NIDDM/MODY in Japanese but they are less common than mutations in the HNF-1 alpha/MODY3 gene. The information on the sequence of the HNF-4 alpha gene and its promoter region will facilitate the search for mutations in other populations and studies of the role of this gene in determining normal pancreatic beta-cell function.

Diabetes associated with a novel 3264 mitochondrial tRNA(Leu)(UUR) mutation.

OBJECTIVE: To present a novel mitochondrial DNA mutation in a diabetic family RESEARCH DESIGN AND METHODS: The proband was a 64-year-old man. In the family, diabetes was maternally inherited. He had diabetes, cerebellar ataxia, cervical lipoma, hearing loss, olfactory dysfunction, ophthalmoplegia, and facial nerve bilateral palsy. On examination, early insulin secretion was blunted, and the M value on glucose clamp test was low. In muscle, ragged red fibers were not found. T-to-C mutation at position 3264 was detected in the proband (0.5% mutant DNAs in leukocyte and 30% in muscle), but was not detected in 201 normal individuals. RESULTS: Heteroplasmy of mutation, maternal inheritance of diabetes, and symptoms related to mitochondrial dysfunction suggest the pathogenecity of this 3264 mutation. As for diabetes etiology, both impaired insulin secretion and decreased insulin sensitivity seem to be important. In phenotypic characteristics, the combination of cerebellar ataxia and lipoma is a symptom sometimes found in myoclonic epilepsy and ragged red fibers (MERRFs). Ophthamoplegia is a symptom of chronic progressive external ophthalmoplegia (CPEO). These suggest that our proband had phenotypic overlap with MERRF and CPEO. Conversely, facial nerve bilateral palsy is a rare finding. The pictures that focused on his cranial nerves were thus unique, suggesting the heterogeneity of mitochondrial DNA (mtDNA)-related diabetes. CONCLUSIONS: A novel 3264 mitochondrial DNA mutation in diabetes gives new insight to the etiology of mitochondrial diabetes. Its pathogenecity supports the belief that the tRNA(Leu)(UUR) gene is an etiological hot spot of mitochondrial diseases.

Diabetes with mitochondrial gene tRNALYS mutation.

OBJECTIVE: To solve a possible relationship between mtDNA mutation of tRNALYS(8344) and diabetes, we have surveyed the tRNALYS mutation, glucose intolerance, and insulin secretory capacity in a Japanese family with diabetes and myoclonic epilepsy with ragged-red fiber disease. Several lines of evidence suggested possible linkage between mtDNA mutation and diabetes (1-4). RESEARCH DESIGN AND METHODS: DNA was isolated from peripheral lymphocytes. The polymerase chain reaction analysis for the tRNA(LYS)(8344) mutation of the mtDNA was conducted as described by Larsson (5). Insulin secretory capacity was assessed by 24-h urinary C-peptide immunoreactivity response (CPR) excretion and plasma CPR to glucagon administration. RESULTS: We identified seven subjects with the tRNA(LYS) mutation as well as seven non-mutated members in the pedigrees. Oral glucose tolerance tests in the pedigree indicated that five of the mutated subjects were diabetic, one had impaired glucose tolerance, and one had normal glucose tolerance (NGT), whereas all nonmutated family members had NGT. The pedigree shows maternal transmission of diabetes and the tRNA(LYS) mutation over three generations. Twenty-four-hour urinary excretion of CPR was significantly reduced in the mutant subjects (mean +/- SD, 67.8 +/- 79.2 nmol/day, n = 6, P < 0.001) compared with the nonmutant members (276.6 +/- 41.8 nmol/day, n = 5) and the age-matched normal control subjects (263 +/- 64.3 nmol/day, n = 12). Plasma CPR 6 min after glucagon injection demonstrated a marked reduction in the mutant subjects (3.68 +/- 3.45 nmol/l, n = 5, P < 0.001) compared with the nonmutant members (19.4 +/- 1.17 nmol/l, n = 5) and the normal control subjects (15.8 +/- 3.81 nmol/l, n = 12). Bilateral neurosensory deafness was demonstrated in five of seven (71.4%) mutant subjects (five of five [100%] mutated diabetic patients), but not detected in six nonmutant members. CONCLUSIONS: This observation is the first report of association of diabetes with the mitochondrial tRNA(LYS) mutation. Insulin secretory capacity was significantly lower in the mutant members than in the nonmutated members. These findings suggest that the pancreatic beta-cell secretory defect of insulin might be one of the phenotypes of the mitochondrial tRNA(LYS) mutation.

Urinary chiro-inositol excretion is an index marker of insulin sensitivity in Japanese type II diabetes.

OBJECTIVE: To determine the relationship between urinary chiro-inositol excretion and insulin sensitivity in Japanese type II diabetic patients. RESEARCH DESIGN AND METHODS: Eighteen subjects were age-matched, nonobese, type II diabetic patients. Eight subjects had impaired glucose tolerance (IGT), and 10 had normal glucose tolerance (NGT). We quantified urinary chiro-inositol excretion using gas chromatography-mass spectrometry and the insulin sensitivity index (SI), and glucose effectiveness (SG) using Bergman's modified minimal model method. RESULTS: The urinary excretion of chiro-inositol was much lower in the diabetic patients (32.3 +/- 16.0 mumol/day, means +/- SD) than in the NGT subjects (96.0 +/- 17.6; P < 0.0001) and IGT subjects (58.9 +/- 11.6; P < 0.0001). SI was much lower in the diabetic patients (3.81 +/- 1.49) than in the NGT subjects 6.30 +/- 1.59, P < 0.0005). SG was much lower in the diabetic patients (2.14 +/- 0.56) than in the NGT subjects (3.07 +/- 0.38, P < 0.0001). There was a significant correlation between urinary chiro-inositol excretion and SI (r = 0.766), as well as a significant correlation between urinary chiro-inositol excretion and SG (r = 0.747).

Mutations in the genes for hepatocyte nuclear factor (HNF)-1alpha, -4alpha, -1beta, and -3beta; the dimerization cofactor of HNF-1; and insulin promoter factor 1 are not common causes of early-onset type 2 diabetes in Pima Indians.

OBJECTIVE: Maturity-onset diabetes of the young (MODY) is a genetically heterogeneous subtype of type 2 diabetes characterized by an early age at onset and autosomal dominant inheritance. MODY can result from heterozygous mutations in at least five genes. The purpose of this study was to determine whether alterations in known MODY genes and two MODY candidate genes contribute to the development of early-onset type 2 diabetes in Pima Indians. RESEARCH DESIGN AND METHODS: The coding regions of the known MODY genes hepatocyte nuclear factor (HNF)-1alpha, HNF-4alpha, HNF-1beta, and insulin promoter factor 1 and the coding regions of two MODY candidate genes, HNF-3beta and the dimerization cofactor of HNF-1, were sequenced in genomic DNA from Pima Indians. The primary "affected" study population consisted of 46 Pima Indians whose age at onset of type 2 diabetes was < or =20 years. DNA sequence variants identified in the affected group were then analyzed in a group of 80 "unaffected" Pima Indians who were at least 40 years old and had normal glucose tolerance. RESULTS: A total of 11 polymorphisms were detected in these genes. However, none of the polymorphisms differed in frequency among Pima Indians with an early age at onset of diabetes compared with older Pima Indians with normal glucose tolerance. CONCLUSIONS: Mutations in these known MODY or MODY candidate genes are not a common cause of early-onset diabetes in Pima Indians.

Variations in vitamin D-binding protein (group-specific component protein) are associated with fasting plasma insulin levels in Japanese with normal glucose tolerance.

The locus of the vitamin D-binding protein (DBP; also known as group-specific component protein or Gc) gene, chromosome 4q12, has been reported to be associated with glucose metabolism in several ethnic groups, including Pima Indians. We have recently reported the association of the DBP genotype with type 2 diabetes mellitus in Japan. The aim of this study was to investigate whether genetic variations of DBP have any influence on glucose metabolism without secondary effects of hyperglycemia or diabetes mellitus using 82 Japanese with normal glucose tolerance. The variations of the DBP gene (Gc 1F, 1S, and 2) were determined by PCR-restriction fragment length polymorphism. Fasting plasma insulin concentration and homeostasis model assessment, an index of insulin resistance, were significantly different based on the DBP genotype (P < 0.01 and P < 0.05, respectively). The people with Gc 1S-2 (5.73 +/- 2.57 microU/mL) and 1S-1S (5.30 +/- 3.46 microU/mL) had significantly higher fasting plasma concentrations than those with 1F-1F (2.84 +/- 1.67 microU/mL) (P < 0.01 and P < 0.03, respectively). There was no significant difference in plasma glucose concentration, body mass index, total cholesterol, triglyceride, and blood pressure. In conclusion, genetic variations of DBP are associated with insulin resistance in Japanese with normal glucose tolerance, which might contribute to the development of type 2 diabetes.

Mitochondrial deoxyribonucleic acid 3256C-T mutation in a Japanese family with noninsulin-dependent diabetes mellitus.

Accumulating reports indicate a relationship between mitochondrial DNA mutation and impaired glucose-induced insulin secretion leading to a subtype of noninsulin-dependent diabetes mellitus. DNA from a 45-yr-old Japanese woman with noninsulin-dependent diabetes mellitus and muscle atrophy was isolated and studied for mitochondrial DNA mutations. We identified a mitochondrial DNA C-T heteroplasmic mutation at nucleotide position 3256. The mutation was located in the transfer ribonucleic acidLeu in a region conserved in evolution. Eight other members of her family were examined for the mutation. Six of them had the same mutation together with noninsulin-dependent diabetes mellitus, and one teenage boy had the mutation and impaired glucose tolerance. The other family member who did not have this mutation had normal glucose tolerance. The enzyme activity of the mitochondrial oxidative phosphorylation pathway in the muscle of the proband was measured. The enzyme activity was decreased in the proband, especially in complex I. This mutation might be responsible for the abnormal glucose metabolism.

Tyrosine hydroxylase gene microsatellite polymorphism associated with insulin resistance in depressive disorder.

A high association between type 2 diabetes mellitus and depressive illness has been reported. Insulin resistance during depressive illness might contribute to the linkage between depression and type 2 diabetes. To determine whether the genetic polymorphisms of the tyrosine hydroxylase ([TH] HUMTH01) and insulin (INS-VNTR) genes contribute to insulin resistance in depressive illness, we analyzed the association between the polymorphisms and insulin resistance in 41 Japanese patients with depressive disorder, 204 normal control subjects, 161 cohort subjects with normal glucose tolerance (NGT) and without depressive symptomatology, and 59 NGT subjects with depressive symptomatology. The depressive patients had a significantly lower insulin sensitivity index (SI) than the control subjects (P= .016). Depressive NGT subjects had a significantly higher homeostasis model assessment (HOMA) insulin resistance index [HOMA(R)] than the nondepressive NGT subjects (P < .0001). The depressive patients and NGT subjects had more HUMTH01 allele 7 (TH7) than the controls and nondepressive NGT subjects. SI was significantly lower in patients with the TH7/7 homozygote versus patients with the other genotypes and the controls. TH7 was associated with higher HOMA(R) as compared with the other alleles in the NGT subjects. Insulin resistance was associated with depressive disorders. The HUMTH01 and INS-VNTR were associated with insulin resistance and depressive symptoms.

Effect of manidipine and delapril on insulin sensitivity in type 2 diabetic patients with essential hypertension.

The open trial was designed to evaluate the effects of long-term antihypertensive treatment with the calcium-channel blocker, manidipine and the angiotensin converting enzyme (ACE) inhibitor, delapril on insulin sensitivity in Japanese non-insulin dependent diabetes mellitus (NIDDM) patients with essential hypertension. We measured the insulin sensitivity index (SI) and the glucose-effectiveness (SG) by the use of Bergman's minimal model method in 18 hypertensive NIDDM patients before and after administration of manidipine (group A) or delapril (group B) for 3 months. Manidipine treatment for 3 months significantly improved SI in group A from 3.35 +/- 0.61 (x 10(-4) min-1 microU-1 ml-1) to 4.70 +/- 1.34 (P < 0.05). Delapril treatment for 3 months also significantly improved SI in group B from 3.56 +/- 1.04 to 5.00 +/- 0.87 (P < 0.05). Manidipine significantly improved SG in group A from 1.60 +/- 0.64 (x 10(-2) min) to 2.19 +/- 0.38 (P < 0.05). Delapril treatment also significantly improved SG in the group B from 1.41 +/- 0.56 to 1.91 +/- 0.35 (P < 0.05). Manidipine and delapril did not affect urinary C-peptide excretion for 24 h in the hypertensive NIDDM patients. Treatment with manidipine or delapril significantly reduced systolic and diastolic blood pressures in the hypertensive NIDDM patients. There were no differences between plasma glucose, serum total triglycerides, and cholesterol or lipoprotein cholesterol fractions, heart rate and body weight after 3 months on manidipine or delapril. This study confirmed the improving effects on SI and SG by long-term treatment with manidipine or delapril in the hypertensive NIDDM patients.

Oxidative damage to mitochondrial DNA and its relationship to diabetic complications.

Increased oxidative stress induced by hyperglycemia may contribute to the pathogenesis of diabetic complications. Oxidative stress is known to increase the conversion of deoxyguanosine (dG) to 8-hydroxydeoxyguanosine (8-OHdG) in DNA, which is linked to increased mitochondrial DNA (mtDNA) deletions. We investigated mtDNA deletions and 8-OHdG in the muscle DNA of non-insulin-dependent diabetes mellitus (NIDDM) patients. mtDNA deletion of 4977 bp (delta mtDNA4977) and the content of 8-OHdG in the muscle DNA of the NIDDM patients were much higher than those of the control subjects. There was a significant correlation between delta mtDNA4977 and the 8-OHdG content (P < 0.0001). Both delta mtDNA4977 and the 8-OHdG content were also correlated with the duration of diabetes. Delta mtDNA4977 and the 8-OHdG content in muscle DNA increased in proportion to the severity of diabetic nephropathy and retinopathy. This is the first report that an increase in delta mtDNA4977 and 8-OHdG is proportional to the severity of diabetic complications. Oxidative mtDNA damage is speculated to contribute to the pathogenesis of diabetic complications though a defect in mitochondrial oxidative phosphorylation or other mechanisms. 8-OHdG and delta mtDNA4977 are useful markers to evaluate oxidative mtDNA damage in the diabetic patients.

Oxidative DNA damage in diabetes mellitus: its association with diabetic complications.

AIMS/HYPOTHESIS: Augmented oxidative stress induced by hyperglycaemia possibly contributes to the pathogenesis of diabetic complications. Oxidative stress is known to increase the conversion of deoxyguanosine to 8-oxo, 2'-deoxyguanosine in DNA. To investigate the possible contribution of oxidative DNA damage to the pathogenesis of diabetic complications, we measured the content of 8-oxo, 2'-deoxyguanosine in the urine and the blood mononuclear cells of Type II (non-insulin-dependent) diabetic patients. METHODS: We studied 53 Type II diabetic patients and 39 age-matched healthy control subjects. We assayed 8-oxo, 2'-deoxyguanosine by HPLC-electrochemical detection method. RESULTS: The content of 8-oxo, 2'-deoxyguanosine in the urine and the mononuclear cells of the Type II diabetic patients was much higher than that of the control subjects. Urinary 8-oxo, 2'-deoxyguanosine excretion and the 8-oxo, 2'-deoxyguanosine content in the mononuclear cells from the diabetic patients with complications were higher than those from the diabetic patients without complications. Urinary excretion of 8-oxo, 2'-deoxyguanosine was significantly correlated with the 8-oxo, 2'-deoxyguanosine content in the mononuclear cells. The 8-oxo, 2'-deoxyguanosine content in the urine and mononuclear cells was correlated with the haemoglobin A1c value. CONCLUSIONS/INTERPRETATION: This is the first report of a direct association between oxidative DNA damage and the complications of diabetes. The augmented oxidative DNA damage in diabetes is speculated to contribute to the pathogenesis of diabetic complications.

Urinary excretion of 8-oxo-7, 8-dihydro-2'-deoxyguanosine as a predictor of the development of diabetic nephropathy.

AIMS/HYPOTHESIS: The increased oxidative stress in diabetes is known to contribute to the progression of diabetes and its complications. We have reported a significant relation between the content of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG), a product of oxidative DNA damage in urine or leukocytes and the severity of diabetic nephropathy and retinopathy [1]. We investigated whether 8-oxodG in urine or leukocytes is associated with the progression of diabetic nephropathy. METHODS: We measured urinary 8-oxodG contents at entry and carried out a prospective longitudinal study to assess the progression of nephropathy over 5 years. RESULTS: There was a significant progression of diabetic nephropathy in the patients with higher excretion of 8-oxodG in urine compared with the patients with moderate or lower excretion of 8-oxodG. There was no significant association between the leukocyte 8-oxodG contents and the development of nephropathy. The multivariate logistic regression analysis suggests that the urinary 8-oxodG was the strongest predictor of nephropathy among several known risk factors. CONCLUSION/INTERPRETATION: This study provides evidence that increased oxidative stress has a primary role in the pathogenesis of diabetic nephropathy. A local enhancement of oxidative stress in diabetic kidney might explain the possible linkage between the increased urinary excretion of 8-oxodG and the development of nephropathy. 8-oxodG in urine is a useful clinical marker to predict the development of diabetic nephropathy in diabetic patients.

Tissue distribution and species difference of the brain type glucose transporter (GLUT3).

The complementary DNA for the human brain type glucose transporter (GLUT3) was used to determine its tissue specific expression in human, monkey, rabbit, rat, and mouse. Under high stringent conditions, 4.1 and 3.2 kilobase (kb) GLUT3 transcripts in monkey and a single 4.1 kb GLUT3 mRNA in rabbit, rat, and mouse were detected by RNA blot analysis. Although the GLUT3 transcripts were widely distributed, as are the erythrocyte type glucose transporter (GLUT1) transcripts, this mRNA is most abundant in the brain. However, the relative abundance of GLUT3 mRNA in the various regions of the monkey brain shows a different pattern from that of GLUT1 mRNA: GLUT3 is most highly expressed in the frontal lobe of the cerebrum, whereas GLUT1 is most abundant in the basal ganglia and the thalamus. Moderately higher GLUT3 mRNA levels were detected in the parietal lobe of the cerebrum, hippocampus, and cerebellum than the levels of GLUT1 transcripts. We also detected GLUT3 mRNA in adult human psoas major muscle, although it has been reported that the GLUT3 gene is scarcely expressed in adult human skeletal muscle of the thigh. In addition, in the rat and the mouse, no transcripts of the GLUT3 gene were detected in liver, kidney, small intestine, skeletal muscle, or fat besides in brain. Thus, the expression of the GLUT3 gene seems to be restricted to the brain in rodents. These results suggest that the expression of GLUT1 and GLUT3 genes might be regulated by different mechanisms.

Role of urotensin II gene in genetic susceptibility to Type 2 diabetes mellitus in Japanese subjects.

AIM/HYPOTHESIS: Urotensin II is a potent vasoactive hormone and the urotensin II gene (UTS2) is localized to 1p36-p32, one of the regions reported to show possible linkage with Type 2 diabetes in Japanese subjects. The aim of this study is to investigate a possible contribution of SNPs in the UTS2 gene to the development of Type 2 diabetes. METHODS: We surveyed SNPs in the UTS2 gene in 152 Japanese subjects with Type 2 diabetes mellitus and two control Japanese cohorts: one consisting of 122 elderly subjects who met stringent criteria for being non-diabetic, including being older than 60 years of age with no evidence of diabetes (HbA(1c)<5.6%), and another 268 subjects with normal glucose tolerance. RESULTS: We identified two SNPs with amino acid substitutions, designated T21M and S89N. The allele frequency of 89N was higher in Type 2 diabetic patients than in both elderly normal subjects (p=0.0018) and subjects with normal glucose tolerance (p=0.0011), whereas the allele frequency of T21M was essentially identical in these three groups. Furthermore, in the subjects with normal glucose tolerance, 89N was associated with higher insulin concentrations on oral glucose tolerance test, suggesting reduced insulin sensitivity in subjects with 89N. CONCLUSION/INTERPRETATION: These results strongly suggest that the S89N polymorphism in the UTS2 gene is associated with the development of Type 2 diabetes, via insulin sensitivity, in Japanese subjects.

Pancreatic beta-cell secretory defect associated with mitochondrial point mutation of the tRNA(LEU(UUR)) gene: a study in seven families with mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS).

Recent evidence suggests possible linkage between diabetes mellitus and mitochondrial gene mutation. We surveyed mitochondrial tRNA(LEU(UUR)) (3243) mutation in 7 mitochondrial encephalomyopathy, lactic acidosis and stroke-like episode (MELAS) families and identified 24 mutated subjects (7 MELAS probands and 17 non-MELAS relatives) as well as 11 non-mutant family members. An OGTT in the 24 mutant relatives revealed 14 diabetic subjects, 3 with impaired glucose tolerance and 7 with normal glucose tolerance and all non-mutant family members as having normal glucose tolerance. Insulinogenic index was significantly reduced in the mutant diabetic subjects and those with impaired and normal glucose tolerance in comparison with the normal control subjects and the non-mutant members. Urinary 24-h C-peptide immunoreactivity excretion was markedly reduced in the mutant diabetic subjects and those with normal and impaired glucose tolerance, compared with the control subjects and the non-mutant family members. Plasma C-peptide immunoreactivity 6 min after glucagon injection was markedly reduced in the mutant diabetic subjects and those with normal and impaired glucose tolerance compared with the control subjects and the non-mutant family members. Si, an index of insulin sensitivity of the four mutant subjects was within normal range. Islet cell antibodies were negative in sera of eight mutated diabetic subjects, 2 and 6 with impaired and normal glucose tolerance, respectively. Diabetic retinopathy and nephropathy were demonstrated in 7 (50%) and 12 (85.7%) of 14 mutant diabetic subjects, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)