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Eiichi Araki

Publications and source records attributed to Eiichi Araki.

At least 19 recordsLinked to original sources
PubMed2007

Impact of mitochondrial ROS production in the pathogenesis of diabetes mellitus and its complications.

In this review, the impacts of mitochondrial reactive oxygen species (ROS) on diabetes and its complications are described. In endothelial cells, high-glucose treatment increases mitochondrial ROS and normalization of the ROS production by inhibitors of mitochondrial metabolism, or by overexpression of UCP-1 or MnSOD, prevents glucose-induced activation of PKC, formation of AGE, and accumulation of sorbitol, all of which are believed to be the main molecular mechanisms of diabetic complications. Glomerular hyperfiltration, one of the characteristics of early diabetic nephropathy, may be caused by mitochondrial ROS through activation of COX-2 gene transcription, followed by PGE2 overproduction. In pancreatic beta cells, hyperglycemia also increases mitochondrial ROS, which suppresses the first phase of glucose-induced insulin secretion, at least in part, through the suppression of GAPDH activity. In liver cells, similar to that in hyperglycemia, TNF-alpha increases mitochondrial ROS, which in turn activates apoptosis signal-regulating kinase 1 (ASK1) and c-jun NH2-terminal kinases (JNK), increases serine phosphorylation of IRS-1, and decreases insulin-stimulated tyrosine phosphorylation of IRS-1, leading to insulin resistance. These results suggest the importance of mitochondrial ROS in the pathogenesis of diabetes mellitus and its complications through modification of various cellular events in many tissues, including vessels, kidney, pancreatic beta cells, and liver.

AMP-Activated Protein Kinases↗
PubMed2006

Possible relevance of alpha lipoic acid contained in a health supplement in a case of insulin autoimmune syndrome.

The insulin autoimmune syndrome is characterized as producing polyclonal or monoclonal anti-insulin autoantibodies in a patient with no previous history of exposure to exogenous insulin. The patient is 44-year-old Japanese woman and she had symptoms of hypoglycaemia without exposure to exogenous insulin. The patient was considered to have IAS because high titre of anti-insulin autoantibodies (96-98%: bound/total) were found in her serum. Her HLA DR beta1 DNA sequences analysis revealed that she has the DRB1(*)0406 and DRB1(*)0901. Our patient have been taken alpha lipoic acid (ALA) before onset. SH group compounds are known to play an important role in the pathogenesis of IAS, and ALA contains SH. From these data, we propose the possibility of the correlation between pathogenesis of IAS and ALA, and it will be important to pay attention for ALA as a cause of hypoglycemia in such cases.

Adult↗
PubMed2006

Troglitazone inhibits oxidized low-density lipoprotein-induced macrophage proliferation: impact of the suppression of nuclear translocation of ERK1/2.

Thiazolidinediones (TZDs), which were known as novel insulin-sensitizing antidiabetic agents, have been reported to inhibit the acceleration of atherosclerotic lesions. Macrophages play important roles in the development of atherosclerosis. We previously reported that oxidized low-density lipoprotein (Ox-LDL) induces macrophage proliferation through ERK1/2-dependent GM-CSF production. In the present study, we investigated the effects of two TZDs, troglitazone and ciglitazone on Ox-LDL-induced macrophage proliferation. Troglitazone significantly inhibited Ox-LDL-induced increases in [(3)H]thymidine incorporation into and proliferation of mouse peritoneal macrophages, whereas ciglitazone had no effects. Troglitazone and ciglitazone both significantly induced PPARgamma activity, suggesting that the inhibitory effect of troglitazone was not mediated by PPARgamma. Ox-LDL-induced production of GM-CSF was significantly inhibited by troglitazone, but not by ciglitazone. Troglitazone inhibited Ox-LDL-induced production of intracellular reactive oxygen species, whereas ciglitazone had no effect. The antioxidant reagents NAC and NMPG each inhibited phosphorylation of ERK1/2, whereas troglitazone and ciglitazone had no effects. However, troglitazone, NAC and NMPG all inhibited nuclear translocation of ERK1/2. In conclusion, troglitazone inhibited Ox-LDL-induced GM-CSF production by suppressing nuclear translocation of ERK1/2, thereby inhibiting macrophage proliferation. This suppression of macrophage proliferation by troglitazone may, at least in part, explain its antiatherogenic effects.

Animals↗
PubMed2006

AMPK and cell proliferation--AMPK as a therapeutic target for atherosclerosis and cancer.

AMPK is a serine/threonine protein kinase, which serves as an energy sensor in all eukaryotic cell types. Published studies indicate that AMPK activation strongly suppresses cell proliferation in non-malignant cells as well as in tumour cells. These actions of AMPK appear to be mediated through multiple mechanisms including regulation of the cell cycle and inhibition of protein synthesis, de novo fatty acid synthesis, specifically the generation of mevalonate as well as other products downstream of mevalonate in the cholesterol synthesis pathway. Cell cycle regulation by AMPK is mediated by up-regulation of the p53-p21 axis as well as regulation of TSC2-mTOR (mammalian target of rapamycin) pathway. The AMPK signalling network contains a number of tumour suppressor genes including LKB1, p53, TSC1 and TSC2, and overcomes growth factor signalling from a variety of stimuli (via growth factors and by abnormal regulation of cellular proto-oncogenes including PI3K, Akt and ERK). These observations suggest that AMPK activation is a logical therapeutic target for diseases rooted in cellular proliferation, including atherosclerosis and cancer. In this review, we discuss about exciting recent advances indicating that AMPK functions as a suppressor of cell proliferation by controlling a variety of cellular events in normal cells as well as in tumour cells.

AMP-Activated Protein Kinases↗
PubMed2006

A case of slowly progressive type 1 diabetes with unstable glycemic control caused by unusual insulin antibody and successfully treated with steroid therapy.

A 75-year-old man with type 1 diabetes and history of insulin therapy for previous 3 years using only human recombinant ones was suffering from unstable glycemic control. He had a high level of total insulin and a high titer of insulin antibodies (IA) (bound/total ratio: 89.8%). Low affinity constant (k(1): 0.0312 x 10(8) M(-1)) and high binding capacity (b(1): 51.8 x 10(-8) M) of IA in the patient detected by the Scatchard analysis were not compatible with those of IA associated with exogenous insulin injections in the diabetic patients, but compatible with those of the insulin autoantibodies found in patients with insulin autoimmune syndrome (IAS), although he had DRB1*0405, which may have protection against IAS development. The glucose infusion rate during hyperinsulinemic euglycemic clamp was 2.84 mg/kg/min, suggesting a high level of insulin resistance. Steroid pulse therapy (1000 mg for 3 days) aimed at reducing the possible effect of the IA on his insulin resistance and glycemic instability successfully decreased IA titer (from 89.8 to 58.3%), lowered its binding capacity (51.8-9.8 x 10(-8) M), increased glucose infusion rate (from 2.84 to 5.55 mg/kg/min) and improved glycemic control (HbA(1c): from 10.0 to 7.4%) with reduced blood glucose excursion. In conclusion, the alteration in insulin pharmacokinetics induced by IA seemed to be the cause of the brittle diabetes of the present case. Steroid treatment might be useful for the improvement of glycamic control in such patients with high IA levels and unstable blood glucose.

Administration, Oral↗
PubMed2006

Development of a highly responsive needle-type glucose sensor using polyimide for a wearable artificial endocrine pancreas.

To produce a long-life, stable, miniature glucose sensor for a wearable artificial endocrine pancreas (WAEP), we developed a novel microneedle-type glucose sensor using polyimide, designated the PI sensor (outer diameter, 0.3 mm; length, 16 mm), and investigated its characteristics in vitro and in vivo. In the in vitro study, we tested the sensor in 0.9% NaCl solution with varying glucose concentrations and observed an excellent linear relationship between the sensor output and glucose concentration (range: 0-500 mg/100 ml). In in vivo experiments, the PI sensor was inserted into the abdominal subcutaneous tissue of beagle dogs (n = 5), and interstitial fluid glucose concentrations were monitored after sensor calibration. Simultaneously, blood glucose concentrations were also monitored continuously with another PI sensor placed intravenously. The correlation and time delay between subcutaneous tissue glucose (Y) and blood glucose concentrations (X: 30-350 mg/100 ml) were Y = 1.03X + 7.98 (r = 0.969) and 6.6 +/- 1.2 min, respectively. We applied the new WAEP system/PI sensor and an intravenous insulin infusion algorithm developed previously for glycemic control in diabetic dogs. The use of the WAEP system resulted in excellent glycemic control after an oral glucose challenge of 1.5 g/kg (post-challenge blood glucose levels: 176 +/- 18 mg/100 ml at 65 min and 93 +/- 23 mg/100 ml at 240 min), without any hypoglycemia. Thus, we confirmed that our new PI sensor has excellent sensor characteristics in vitro and in vivo. The new WAEP using this sensor is potentially suitable for clinical application.

Administration, Oral↗
PubMed2006

Impact of mitochondrial reactive oxygen species and apoptosis signal-regulating kinase 1 on insulin signaling.

Tumor necrosis factor (TNF)-alpha inhibits insulin action; however, the precise mechanisms are unknown. It was reported that TNF-alpha could increase mitochondrial reactive oxygen species (ROS) production, and apoptosis signal-regulating kinase 1 (ASK1) was reported to be required for TNF-alpha-induced apoptosis. Here, we examined roles of mitochondrial ROS and ASK1 in TNF-alpha-induced impaired insulin signaling in cultured human hepatoma (Huh7) cells. Using reduced MitoTracker Red probe, we confirmed that TNF-alpha increased mitochondrial ROS production, which was suppressed by overexpression of either uncoupling protein-1 (UCP)-1 or manganese superoxide dismutase (MnSOD). TNF-alpha significantly activated ASK1, increased serine phosphorylation of insulin receptor substrate (IRS)-1, and decreased insulin-stimulated tyrosine phosphorylation of IRS-1 and serine phosphorylation of Akt, and all of these effects were inhibited by overexpression of either UCP-1 or MnSOD. Similar to TNF-alpha, overexpression of wild-type ASK1 increased serine phosphorylation of IRS-1 and decreased insulin-stimulated tyrosine phosphorylation of IRS-1, whereas overexpression of dominant-negative ASK1 ameliorated these TNF-alpha-induced events. In addition, TNF-alpha activated c-jun NH(2)-terminal kinases (JNKs), and this observation was partially inhibited by overexpression of UCP-1, MnSOD, or dominant-negative ASK1. These results suggest that TNF-alpha increases mitochondrial ROS and activates ASK1 in Huh7 cells and that these TNF-alpha-induced phenomena contribute, at least in part, to impaired insulin signaling.

Animals↗
PubMed2006

Activation of AMP-activated protein kinase reduces hyperglycemia-induced mitochondrial reactive oxygen species production and promotes mitochondrial biogenesis in human umbilical vein endothelial cells.

We previously proposed that the production of hyperglycemia-induced mitochondrial reactive oxygen species (mtROS) is a key event in the development of diabetes complications. The association between the pathogenesis of diabetes and its complications and mitochondrial biogenesis has been recently reported. Because metformin has been reported to exert a possible additional benefit in preventing diabetes complications, we investigated the effect of metformin and 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR) on mtROS production and mitochondrial biogenesis in cultured human umbilical vein endothelial cells. Treatment with metformin and AICAR inhibited hyperglycemia-induced intracellular and mtROS production, stimulated AMP-activated protein kinase (AMPK) activity, and increased the expression of peroxisome proliferator-activated response-gamma coactivator-1alpha (PGC-1alpha) and manganese superoxide dismutase (MnSOD) mRNAs. The dominant negative form of AMPKalpha1 diminished the effects of metformin and AICAR on these events, and an overexpression of PGC-1alpha completely blocked the hyperglycemia-induced mtROS production. In addition, metformin and AICAR increased the mRNA expression of nuclear respiratory factor-1 and mitochondrial DNA transcription factor A (mtTFA) and stimulated the mitochondrial proliferation. Dominant negative-AMPK also reduced the effects of metformin and AICAR on these observations. These results suggest that metformin normalizes hyperglycemia-induced mtROS production by induction of MnSOD and promotion of mitochondrial biogenesis through the activation of AMPK-PGC-1alpha pathway.

AMP-Activated Protein Kinases↗
PubMed2006

[Strategies for the prevention of elderly-onset type 2 diabetes mellitus].

The recent medical statistics have revealed that the incidence of type 2 diabetes increased more rapidly in elderly people than that of manhood. Several randomized clinical trials to evaluate the strategies for preventing type 2 diabetes such as Diabetes Prevention Program (DPP), The Finnish Diabetes Prevention Study, The STOP-NIDDM, have been conducted. These studies suggested that a lifestyle intervention and treatment with antihyperglycemic agent inhibit the onset of diabetes in elderly people as well as manhood. However, the evidence for elderly people is not sufficient. The social and physical features of elderly persons should also been taken into account for the strategies to prevent the elderly-onset type 2 diabetes.

Age of Onset↗
PubMed2005

Adenosine monophosphate-activated protein kinase suppresses vascular smooth muscle cell proliferation through the inhibition of cell cycle progression.

Vascular smooth muscle cell (VSMC) proliferation is a critical event in the development and progression of vascular diseases, including atherosclerosis. We investigated whether the activation of adenosine monophosphate-activated protein kinase (AMPK) could suppress VSMC proliferation and inhibit cell cycle progression. Treatment of human aortic smooth muscle cells (HASMCs) or isolated rabbit aortas with the AMPK activator 5-Aminoimidazole-4-carboxamide ribonucleoside (AICAR) induced phosphorylation of AMPK and acetyl Co-A carboxylase. AICAR significantly inhibited HASMC proliferation induced by both platelet-derived growth factor-BB (PDGF-BB) and fetal calf serum (FCS). Treatment with AICAR inhibited the phosphorylation of retinoblastoma gene product (Rb) induced by PDGF-BB or FCS, and increased the expression of cyclin-dependent kinase inhibitor p21(CIP) but not that of p27(KIP). Pharmacological inhibition of AMPK or overexpression of dominant negative-AMPK inhibited both the suppressive effect of AICAR on cell proliferation and the phosphorylation of Rb, suggesting that the effect of AICAR is mediated through the activation of AMPK. Cell cycle analysis in HASMCs showed that AICAR significantly increased cell population in G0/G1-phase and reduced that in S- and G2/M-phase, suggesting AICAR induced cell cycle arrest. AICAR increased both p53 protein and Ser-15 phosphorylated p53 in HASMCs, which were blocked by inhibition of AMPK. In isolated rabbit aortas, AICAR also increased Ser-15 phosphorylation and protein expression of p53 and inhibited Rb phosphorylation induced by FCS. These data suggest for the first time that AMPK suppresses VSMC proliferation via cell cycle regulation by p53 upregulation. Therefore, AMPK activation in VSMCs may be a therapoietic target for the prevention of vascular diseases.

AMP-Activated Protein Kinases↗
PubMed2005

AICAR, an activator of AMP-activated protein kinase, down-regulates the insulin receptor expression in HepG2 cells.

The liver is one of the major target organs of insulin in which the expression of insulin receptor is abundant. We analyzed the effect of AICAR, an AMPK activator, on the expression of insulin receptor in a human hepatoma cell line, HepG2 cells. AICAR treatment for 48 h significantly decreased the expression of the insulin receptor protein in a dose-dependent manner, however, this same effect of AICAR was not observed in either 3T3-L1 adipocytes or CHO cells. The expression of insulin receptor mRNA also decreased after AICAR treatment. In addition, the transcriptional activity of the insulin receptor gene promoter investigated with a luciferase assay was down-regulated by AICAR treatment. Dipyridamole, an adenosine transporter inhibitor, and 5'-amino-5'-deoxyadenosine, an adenosine kinase inhibitor, blocked the effect of AICAR on the down-regulation of the insulin receptor protein, mRNA, and promoter activity. Our findings suggest, for the first time, that AMPK activation could reduce the expression of insulin receptor, at least in part, by a down-regulation of the transcriptional level, and this effect may be liver specific.

3T3-L1 Cells↗
PubMed2005

Enhanced expression of PDX-1 and Ngn3 by exendin-4 during beta cell regeneration in STZ-treated mice.

Progenitor cells exist in the adult pancreas and transform to endocrine cells in pathological conditions. To address the mechanism of beta cell regeneration, mice were treated with streptozotocin (STZ group) or streptozotocin and exendin-4 (STZ + Ex-4 group), and the expression of PDX-1, Ngn3, insulin, IRS-2, and Foxo1 was investigated. PDX-1 mRNA was upregulated biphasically and induction of Ngn3 mRNA occurred shortly after the first increase of PDX-1 expression, a pattern similar to that observed during embryogenesis. PDX-1-positive cells appeared only in islet-like cell clusters (ICCs) in STZ group, but they appeared both in ducts and ICCs in STZ + Ex-4 group. Ngn3-positive cells emerged in ICCs but not in ducts. Therefore, regeneration seemed to occur mainly from intra-islet stem/progenitor cells. Exendin-4 upregulated PDX-1 expression which paralleled increased IRS-2 expression and translocation of Foxo1 from nucleus to cytoplasm. Further analysis of beta cell regeneration should help in the design of novel therapy for diabetes.

Animals↗
PubMed2005

A case of hyperinsulinemia of undetermined origin, successfully treated with long-acting octreotide.

Major causes of fasting hypoglycemia in adults are insulinoma, factitious hypoglycemia and nesidioblastosis. The primary treatment for insulinoma is surgical removal of the tumor, but there are cases with hyperinsulinemia that cannot undergo surgery. Somatostatin analogue is one of the treatments used in such cases of insulinoma or persistent hyperinsulinemic hypoglycemia. We report here a patient who had undetermined hyperinsulinemia and was successfully treated with a long-acting somatostatin analogue, which had recently become available. The patient, a 72-year-old female, who had previously been diagnosed as insulinoma and undergone partial pancreatectomy, was admitted complaining of the recurrence of hypoglycemic attacks after an interval of ten years. On admission, hypoglycemia (42 mg/dl), hyperinsulinemia (IRI: 79.3 microU/m) and low HbA1c (3.6%) were present. In 75 g-OGTT at 30 min after load, IRI reached 6623 microU/ml, while plasma glucose level was 88 mg/dl. The anti-insulin antibody was not present. Since attempts at tumor localization by imaging techniques failed and the patient refused further examinations or surgical treatment, we recommended her to take a medication with a somatostatin analogue. Insulin suppression test using 50 microg of octreotide improved plasma glucose and IRI levels, suggesting the usefulness of the treatment, and a monthly administration of 20 mg of long-acting octreotide has successfully controlled her symptoms of hypoglycemia for 10 months. Our case demonstrated the utility of the long-acting somatostatin analogue for long-term treatment of undetermined hyperinsulinemia. A preliminary loading test using short-acting octreotide may be useful to determine appropriate medication, especially in cases who cannot receive surgical treatment.

Aged↗
PubMed2005

[Polymorphisms of PPARs and metabolic disorders].

Peroxisome proliferator-activated receptors (PPARs) are a member of transcriptional factor that regulates expression of several genes associated with glucose and lipid metabolisms. Some polymorphisms of PPARs gene have been reported, and the impacts of these polymorphisms are examined in patients with several metabolic disorders. The Pro12Ala polymorphism of the PPARgamma gene is studied extensively, and is known to be associated with increased insulin sensitivity and reduced risk for the development of diabetes. Such studies will help us to elucidate the role of PPARs on the development of metabolic disorders and to find new therapeutic approaches to these disorders.

Animals↗
PubMed2005

[Clinical courses of two male siblings on hemodialysis for Fabry disease ].

Fabry disease is an X-linked recessive disease resulting from a deficiency of the lysosomal hydrolase alpha-galactosidase A. In male patients with the classic hemizygous form, acroparesthesias, hypohidrosis, corneal opacities, and dysfunction of the heart, brain, and kidney are observed. Recently, it was reported that 0.5-1.2% of male chronic hemodialysis (HD) patients were diagnosed as having Fabry disease based on the measurement of alpha-galactosidase A activity. Fabry disease is thought to be an important cause of end-stage renal disease. There are a few reports of patients with Fabry disease on long-term HD. Here we report two male siblings with classical type Fabry disease on HD. They had acroparesthesias, and hypohidrosis. Their mother had severe heart failure due to a heterozygous form of Fabry disease. Case 1 is a 44-year-old male. He had mid-cerebral apoplexy at 30 years of age. He started maintenance HD in 2000. Remarkable left ventricular hypertophy and conduction disorders of the heart were found. In 2004, he collapsed and ventricular-tachycardia and severe hypoxic brain damage were found. Now his consciousness level has been in the range of 100 to 300 on the Japan Coma Scale. Case 2 is a 40-year-old male. He started maintenance HD in 1993. Malnutrition due to chronic diarrhea and severe ischemic change in the brain were found. In 1998, he had severe joint pain of shoulders and fingers with ectopic calcifications detected by X ray. The ectopic calcifications were extended to the whole body. In 2004, his dementia by ischemic change in the brain has rapidly progressed. In conclusion, cardiovascular complications, cerebrovascular manifestations, painful ectopic carcifications, and chronic diarrheas in our patients were considered to be specific symptoms of Fabry disease. Young HD patients with these symptoms will need to be examined for Fabry disease.

Adult↗