Activated volcanism of Mount Fuji by the 2011 Japanese large earthquakes.

The relation between earthquakes and volcanic eruptions, each of which is manifested by large-scale tectonic plate and mantle motions, has been widely discussed. Mount Fuji, in Japan, last erupted in 1707, paired with a magnitude (M)-9-class earthquake 49 days prior. Motivated by this pairing, previous studies investigated its effect on Mount Fuji after both the 2011 M9 Tohoku megaquake and a triggered M5.9 Shizuoka earthquake 4 days later at the foot of the volcano, but reported no potential to erupt. More than 300 years have already passed since the 1707 eruption, and even though consequences to society caused by the next eruption are already being considered, the implications for future volcanism remain uncertain. This study shows how volcanic low-frequency earthquakes (LFEs) in the deep part of the volcano revealed unrecognized activation after the Shizuoka earthquake. Our analyses also show that despite an increase in the rate of occurrence of LFEs, these did not return to pre-earthquake levels, indicating a change in the magma system. Our results demonstrate that the volcanism of Mount Fuji was reactivated by the Shizuoka earthquake, implying that this volcano is sufficiently sensitive to external events that are considered to be enough to trigger eruptions.

Were changes in stress state responsible for the 2019 Ridgecrest, California, earthquakes?

Monitoring the Earth's stress state plays a role in our understanding of an earthquake's mechanism and in the distribution of hazards. Crustal deformation due to the July 2019 earthquake sequence in Ridgecrest (California) that culminated in a preceding quake of magnitude (M) 6.4 and a subsequent M7.1 quake caused stress perturbation in a nearby region, but implications of future seismicity are still uncertain. Here, the occurrence of small earthquakes is compared to larger ones, using b-values, showing that the rupture initiation from an area of low b-values, indicative of high stress, was common to both M6.4 and M7.1 quakes. The post-M7.1-quake sequence reveals that another low-b-value zone, which avoided its ruptured area, fell into an area near the Garlock fault that hosted past large earthquakes. If this area were more stressed, there would be a high-likelihood of further activation of seismicity that might influence the Garlock fault.

A b map implying the first eastern rupture of the Nankai Trough earthquakes.

The Nankai Trough megathrust earthquakes inflicted catastrophic damage on Japanese society and more widely. Most research is aimed at identifying strongly coupled regions that are considered as a major source of future disastrous earthquakes. Here we present a b-value map for the entire Nankai Trough zone. The b value, which represents the rate of occurrence of small earthquakes relative to larger ones, is inversely dependent on differential stresses, and has been used to detect highly stressed areas on fault planes in various tectonic situations. A remarkable finding is that the b value is inversely correlated with the slip-deficit rate (SDR). Moreover, the b value for the areas of high SDR in the eastern part is lower than that in the western part, indicating that differential stress on asperities in the eastern part is higher than that in the western part. This may explain the history of the Nankai Trough earthquakes, in which the eastern part tends to rupture first.

A mitochondrial DNA variant at position 16189 is associated with type 2 diabetes mellitus in Asians.

AIMS/HYPOTHESIS: This multinational study was conducted to investigate the association between a mitochondrial DNA (mtDNA) T16189C polymorphism and type 2 diabetes in Asians. The mtDNA 16189C variant has been reported to be associated with insulin resistance and type 2 diabetes. However, a recent meta-analysis concluded that it is negatively associated with type 2 diabetes in Europids. Since the phenotype of an mtDNA mutant may be influenced by environmental factors and ethnic differences in the nuclear and mitochondrial genomes, we investigated the association between the 16189C variant and type 2 diabetes in Asians. METHODS: The presence of the mtDNA 16189C variant was determined in 2,469 patients with type 2 diabetes and 1,205 non-diabetic individuals from Korea, Japan, Taiwan, Hong Kong and China. An additional meta-analysis including previously published Asian studies was performed. Since mtDNA nucleotide position 16189 is very close to the mtDNA origin of replication, we performed DNA-linked affinity chromatography and reverse-phase liquid chromatography/tandem mass spectrometry and chromatin immunoprecipitation to identify protein bound to the 16189 region. RESULTS: Analysis of participants from five Asian countries confirmed the association between the 16189C variant and type 2 diabetes [odds ratio (OR) 1.256, 95% CI 1.08-1.46, p=0.003]. Inclusion of data from three previously published Asian studies (type 2 diabetes n=3,283, controls n=2,176) in a meta-analysis showed similar results (OR 1.335, 95% CI 1.18-1.51, p=0.000003). Mitochondrial single-stranded DNA-binding protein (mtSSB) was identified as a candidate protein bound to the 16189 region. Chromatin immunoprecipitation in cybrid cells showed that mtSSB has a lower binding affinity for the 16189C variant than the wild-type sequence. CONCLUSIONS/INTERPRETATION: The mtDNA 16189C variant is associated with an increased risk of type 2 diabetes in Asians.

Induction of brain-derived neurotrophic factor by leptin in the ventromedial hypothalamus.

Leptin, an adipocyte-derived hormone, reduces food intake by regulating orexigenic and anorexigenic factors in the hypothalamus. Although brain-derived neurotrophic factor is an important anorexigenic factor in the hypothalamus, little is known about the regulation of brain-derived neurotrophic factor expression by leptin in the hypothalamus. In the present study, we examined the effect of leptin on the expression of brain-derived neurotrophic factor in the hypothalamus. I.V. administration of leptin (10 microg/g) led to the increase in the expression of brain-derived neurotrophic factor mRNA, which was observed in the dorsomedial part of the ventromedial hypothalamic nucleus. The increased expression of brain-derived neurotrophic factor mRNA was detected in phosphorylated signal transducer and activator of transcription 3-positive neurons, suggesting that leptin induced brain-derived neurotrophic factor expression in neurons of the dorsomedial part of the ventromedial hypothalamic nucleus. In addition, the expression of brain-derived neurotrophic factor was increased at the protein level in the ventromedial hypothalamic nucleus of leptin-injected mice. Interestingly, brain-derived neurotrophic factor-positive fibers also increased in the ventromedial hypothalamic nucleus and dorsomedial hypothalamic nucleus of leptin-injected mice, which were in close apposition to tyrosine kinase receptor B-immunoreactive neurons and colocalized with synaptophysin, a marker of presynaptic terminals. These results suggest that leptin induces brain-derived neurotrophic factor expression in the dorsomedial part of the ventromedial hypothalamic nucleus and brain-derived neurotrophic factor may exert as anorexigenic factors possibly through the activation of tyrosine kinase receptor B in the ventromedial hypothalamic nucleus and dorsomedial hypothalamic nucleus.

A case of novel de novo paired box gene 6 (PAX6) mutation with early-onset diabetes mellitus and aniridia.

BACKGROUND: Paired box gene 6 (PAX6) is a transcription factor involved in eye development. Mutations of PAX6 cause congenital eye anomalies, such as aniridia. PAX6 is also involved in the development of the endocrine pancreas, and reported to be a genetic factor common to aniridia and glucose intolerance, although the latter is usually mild. Here, we describe a case of PAX6 mutation with early-onset diabetes mellitus. CASE REPORT: A 27-year-old woman was referred to our clinic. She was diagnosed having diabetes at the age of 15 with negative glutamic acid decarboxylase (GAD) antibody. Insulin treatment was started at age 24. Because she had aniridia, PAX6 gene mutation was investigated and a heterozygous 2-bp deletion (c.402del2) was identified. Her parents did not have aniridia and PAX6 mutations. Heterozygous PAX6 mutation may cause glucose intolerance. However, cases of early-onset diabetes mellitus have not been reported. Her parents did not have diabetes, but their insulinogenic indices were low (0.25 and 0.3, respectively). We thought her early-onset diabetes was partly as a result of PAX6 mutation and partly because of an unknown insulin secretory defect inherited from her parents. We could not find any mutations in HNF-1alpha, -1beta, -4alpha, IPF-1, ISL-1, BEAT2/NeuroD1, PAX4, and amylin genes. CONCLUSIONS: We report a case of PAX6 gene mutation with early-onset diabetes mellitus and aniridia. Low insulin secretory capacity in her parents suggested that her insulin secretory defect is as a result of not only PAX6 mutation but other genetic factors inherited from her parents.

Sequence analysis of the pro-opiomelanocortin (POMC) gene in obese/diabetic Japanese.

Pro-opiomelanocortin (POMC)-derived peptides play a critical role in body weight regulation in the central nervous system. Mice deficient in POMC developed obesity. We sought mutations in the POMC gene in 50 morbidly obese (body mass index 35-60 kg/m(2)) Japanese subjects with diabetes by direct sequencing. Apart from two silent mutations (C6982T and C7285T), no other mutations were detected. Frequencies of these mutations were not significantly different between 100 obese subjects and 100 controls. Also, the frequencies did not differ in the subjects with or without diabetes. These results suggest that mutations in the POMC gene are unlikely to be a major factor of obesity or diabetes in Japanese subjects.

Postural tachycardia syndrome in a 28-year-old Japanese woman.

Postural tachycardia syndrome is defined as the development of orthostatic symptoms without orthostatic hypotension. We report a 28-year-old female patient with postural tachycardia syndrome who exhibited palpitation, low-grade fever and weight loss. Evaluation of autonomic nervous system functions showed that cardiovagal function was normal. Sweat response to acetylcholine was decreased. Excessive blood pressure elevation was seen in phase IV of the Valsalva maneuver. Pathophysiologic factors in this case were considered to be alpha adrenergic denervation and beta adrenergic hyperresponsiveness. It is important that this syndrome be widely recognized and properly diagnosed.

A missense mutation of Pax4 gene (R121W) is associated with type 2 diabetes in Japanese.

Pax4 is one of the transcription factors that play an important role in the differentiation of islet beta-cells. We scanned the Pax4 gene in 200 unrelated Japanese type 2 diabetic patients and found a missense mutation (R121W) in 6 heterozygous patients and 1 homozygous patient (mutant allele frequency 2.0%). The mutation was not found in 161 nondiabetic subjects. The R121W mutation was located in the paired domain and was thought to affect its transcription activity through lack of DNA binding. Six of seven patients had family history of diabetes or impaired glucose tolerance, and four of seven had transient insulin therapy at the onset. One of them, a homozygous carrier, had relatively early onset diabetes and slowly fell into an insulin-dependent state without an autoimmune-mediated process. This is the first report of a Pax4 gene mutation that exhibits loss of function and seems to be associated with type 2 diabetes. This work provides significant implications for the Pax4 gene as one of the predisposing genes for type 2 diabetes in the Japanese.

Single nucleotide polymorphism (D68D, T to C) in the syntaxin 1A gene correlates to age at onset and insulin requirement in Type II diabetic patients.

AIM/HYPOTHESIS: Syntaxin 1A is a candidate gene for Type II (non-insulin-dependent) diabetes mellitus, because it plays an important role in insulin secretion from the islet beta cells. We aimed to scan this gene for mutations or genetic markers that correlate with Type II diabetes. METHODS: We identified and characterized coding exons of the syntaxin 1A gene and scanned the newly identified 10 exons using direct sequencing. RESULTS: In the single nucleotide polymorphism (SNP) of exon 3 (D68D, T to C) among three newly identified SNPs, genotype frequency of the homozygote of C allele (CC) occurred more frequently in a Type II diabetic group than in a non-diabetic group (16.48 %, n = 182, vs 11.05 %, n = 181, p = 0.0499). Among the diabetic patients, age of onset in patients with CC genotype was lower than that in patients with the TT and TC genotypes [40.10 +/- 1.50 years old (means +/- SEM) vs 44.20 +/- 0.58, p = 0.005]. Patients with the CC genotype had a higher frequency of insulin treatment (78.30 % vs 46.80 %, p = 0.006) with a duration equal to, or longer than, 10 years. Multiple regression analysis confirmed that the genotype was significantly and independently associated with age at onset and mode of treatment, respectively. CONCLUSION/INTERPRETATION: These data indicate that the SNP in the syntaxin 1A gene (D68D, T to C) correlates to the age of onset and insulin requirements of Type II diabetic Japanese patients.

A suspected case of proximal diabetic neuropathy predominantly presenting with scapulohumeral muscle weakness and deep aching pain.

A 48-year-old man with a 14-year history of type 2 diabetes with proliferative diabetic retinopathy and distal symmetrical diabetic polyneuropathy visited our hospital. Eight months later, he subacutely developed difficulty in both shoulder movement and trouble standing up from a squatting position. This was accompanied by severe bilateral shoulder and thigh pain. Magnetic resonance imaging of the brain, cervical and lumbar spine, computed tomography of the shoulder and X-ray films of the cervical spine and shoulder revealed no abnormality. Cerebrospinal fluid showed a mild elevation of protein (0.93 g/l) without cell infiltration. Antiganglioside antibodies and point mutation of mitochondrial DNA at position 3243 were not found. Neuropathology of the sural nerve showed a moderate myelinated fiber loss, active axonal degeneration, but onion-bulb formation, endoneurial or epineurial vasculitis were not observed. Electromyography revealed neurogenic changes in the proximal upper limb muscles. Nerve conduction studies revealed mild bilateral slowing in nerve conduction velocity in both of the upper and lower limbs. The diagnosis of this patients was suspected to be a proximal diabetic neuropathy (diabetic amyotrophy). The pain and muscle weakness had persisted more severely in the shoulder than in the thigh throughout the clinical course. His unbearable symptoms could be partially alleviated by an administration of a selective serotonin reuptake inhibitor, fluvoxamine maleate. Proximal diabetic neuropathy is a rare disabling type of neuropathy, which is characterized with subacute bilateral muscle weakness and wasting in the proximal part of the lower limbs. The involvement of the scapulohumeral region observed in this case is very unusual in proximal diabetic neuropathy.

Analysis of 825C/T polymorphism of G proteinbeta3 subunit in obese/diabetic Japanese.

The GNB3 825C/T polymorphism, which is common worldwide, is associated with enhanced G-protein activation. The frequency of 825-T allele was increased with body mass index (BMI) and finally had a high frequency in relatively mild obese (BMI >27 kg/m(2)) subjects in some populations. In the present study, we investigated 208 severely obese [BMI >or=30 kg/m(2) (97th percentile)] Japanese subjects including 146 probands with diabetes. No increase in the 825-T allele frequency was observed in the 208 severely obese and even in a subgroup of the 55 most obese [BMI >or=35 kg/m(2) (99.7th percentile)] subjects compared with that in 150 controls (BMI <25 kg/m(2)) (0.48 and 0.48 vs 0.51, respectively). Also, the frequency was not increased in the 146 obese subjects with diabetes (0.48). We concluded that the 825-T allele is not associated with obesity or diabetes associated with obesity at least in the Japanese population.

The renal metabolism of insulin: urinary insulin excretion in patients with mutant insulin syndrome (insulin Wakayama).

Many studies have shown that the kidney plays an important role in the metabolism of many proteins and small peptides. To understand insulin handling in the kidney, we examined urinary insulin excretion under several conditions in patients with mutant insulin syndrome (MIS; insulin Wakayama). Urinary excretion of insulin was studied using high-performance liquid chromatography analysis in patients with MIS. In these patients, most of the insulin extracted from a 24-hour urine collection and from urine collected after stimulation of insulin secretion by glucose or glucagon was normal insulin, whereas 90% of serum insulin is structurally abnormal (Leu-A3 insulin). On the other hand, arginine, which is known as an inhibitor of renal tubular reabsorption, increased urinary excretion of Leu-A3 insulin. The ratio of Leu-A3 and normal insulin in urine after arginine was similar to that in serum. A large amount of Leu-A3 insulin is excreted in urine when reabsorption of insulin at renal tubules is inhibited by arginine. These data indicate that normal and Leu-A3 insulin are filtered through the glomerulus with relatively little restriction. Using the fact that basal urine has a high concentration of normal insulin and an extremely low concentration of Leu-A3 insulin, which has less receptor-binding affinity, we speculated some possibilities. One possibility is that both forms of insulin are reabsorbed by the tubular cells, but with different efficiencies. Leu-A3 insulin absorption in more complete, and this suggests differences in the uptake pathways that may account for the differences in response to arginine infusions. Another possibility is that only normal insulin is secreted from tubules into urine which is mediated by receptors. Our results provide new insight into renal metabolism of insulin and showed that MIS is a useful model for studying it.

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.

Enhanced in vitro production of amyloid-like fibrils from mutant (S20G) islet amyloid polypeptide.

UNLABELLED: Islet amyloid polypeptide (IAPP, "amylin") is the amyloid-fibril-forming polypeptide in the islets of Langerhans associated with type 2 diabetes mellitus. A missense mutation in the IAPP gene associated with early-onset type 2 diabetes has been identified in the Japanese population. This mutation results in a glycine for serine substitution at position 20 of the mature IAPP molecule. Whether or not formation of islet amyloid with resulting destruction of islet tissue is the cause of this diabetes is yet not known. The present in vitro study was performed in order to investigate any influence of the amino acid substitution on the fibril formation capacity. Synthetic full-length wild type (IAPPwt) and mutant (IAPPS20G) as well as corresponding truncated peptides (position 18-29) were dissolved in dimethylsulfoxide (DMSO) or in 10% acetic acid at a concentration of 10 mg/mL and their fibril forming capacity was checked by Congo red staining, electron microscopy, a Congo red affinity assay and Thioflavine Tfluorometric assay. It was found that full-length and truncated IAPPS20G both formed more amyloid-like fibrils and did this faster compared to IAPPwt. The fibril morphology differed slightly between the preparations. CONCLUSION: The amino acid substitution (S20G) is situated close to the region of the IAPP molecule implicated in the IAPP fibrillogenesis. The significantly increased formation of amyloid-like fibrils by IAPPS20G is highly interesting and may be associated with an increased islet amyloid formation in vivo and of fundamental importance in the pathogenesis of this specific form of diabetes.

S20G mutant amylin exhibits increased in vitro amyloidogenicity and increased intracellular cytotoxicity compared to wild-type amylin.

Human amylin, a major constituent of pancreatic amyloid deposits, may be a pathogenetic factor for noninsulin-dependent diabetes mellitus (NIDDM). We demonstrated that the human amylin S20G gene mutation (S20G) was associated with a history of early onset, more severe type of NIDDM, linking the amylin gene to this disease. Also, we demonstrated that expression of human wild-type (WT) amylin in COS-1 cells leads to intracellular amyloidogenesis and induction of apoptosis, suggesting a possible mechanism for disease induction. Therefore we compared the abilities of S20G and WT amylin to induce apoptosis in transfected COS-1 cells and form amyloid in vitro. We transfected the rat (RAT), mutated human (MUT), WT, and S20G amylin genes into COS-1 cells and measured apoptosis using fluorescent-activated cell sorting analysis at 48, 72, and 96 hours. At 96 hours apoptosis increased significantly (P < 0.01) in cells transfected with WT and S20G over RAT or MUT (WT, 19%; S20G, 25%; RAT, 13%; and MUT, 12%) and the difference between WT and S20G was significant (P < 0.05). Synthetic WT and S20G monomeric peptides were used to generate amyloid fibrils in vitro as measured by the thioflavin T binding assay. The S20G amylin formed approximately twofold more amyloid at a rate approximately threefold higher than WT. Electron micrography indicated that the in vitro amyloid generated by WT and S20G amylins were morphologically indistinguishable. The results suggest that increased cytotoxicity by S20G is because of increased amyloidogenicity, which may be a causative factor in the early development of NIDDM, possibly through loss of ss cell mass.

Nonsense mutation of islet-1 gene (Q310X) found in a type 2 diabetic patient with a strong family history.

Islet-1 (Isl-1) is one of the transcription factors that play an important role for the formation of the islet cells. We scanned the Isl-1 gene in 77 Japanese type 2 diabetic patients with a family history and found a heterozygous nonsense mutation (Q310X) in 1 diabetic patient. The mutation was not found in 180 nondiabetic subjects. This mutation is located in the putative transactivation domain and deletes 40 amino acids of the COOH-terminal lesion. The Q310X mutant exhibited a 50% reduction in activity compared with the wild-type when tested for stimulation of transcription of a human amylin promoter-linked luciferase reporter gene in betaTC3 cells. The patient was a 49-year-old nonobese man who was diagnosed as having type 2 diabetes at 32 years of age and has been treated with sulfonylureas. The mutation was found in his mother, who has type 2 diabetes, and in his 14-year-old daughter, who has normal glucose tolerance but a relatively low insulin response. This is the first reported finding of Isl-1 gene mutation in type 2 diabetes. Although Isl-1 is not a common predisposing gene for Japanese type 2 diabetes, the mutation in this gene may be a rare cause of diabetes in isolated families.