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T Ogihara

Publications and source records attributed to T Ogihara.

At least 91 records · Page 5Linked to original sources
PubMed2001

Contribution of Bcl-2, but not Bcl-xL and Bax, to antiapoptotic actions of hepatocyte growth factor in hypoxia-conditioned human endothelial cells.

Angiogenic growth factors play important roles in angiogenic responses, such as vasculogenesis and angiogenesis in response to hypoxia. A novel angiogenic growth factor, hepatocyte growth factor (HGF), has been reported to inhibit endothelial cell death. However, its molecular mechanisms are largely unknown. Thus, we studied (1) the effects of HGF on hypoxia-induced endothelial apoptosis and (2) the molecular mechanisms of the antiapoptotic actions of HGF in endothelial cells. Severe hypoxia increased the cell death rate in human aortic endothelial cells, whereas HGF significantly attenuated cell death. In addition, hypoxic treatment resulted in a significant increase in apoptotic cells, whereas HGF could attenuate apoptosis, accompanied by attenuation of the increase in caspase-3-like activity (P<0.01). Of importance, HGF significantly increased Bcl-2, an inhibitor of apoptosis, in a dose-dependent manner under normoxic and hypoxic conditions (P<0.01), whereas hypoxic conditions resulted in a significant decrease in Bcl-2. In contrast, HGF failed to affect Bcl-xL, which is also well known as an inhibitor of apoptosis under both normoxic and hypoxic conditions, whereas Bcl-xL was significantly decreased in endothelial cells exposed to hypoxia (P<0.01). No significant change in Bax, a promoter of apoptosis, was also observed in endothelial cells under hypoxia, whereas HGF did not affect BAX: Overall, this study demonstrated that HGF prevented endothelial cell death induced by hypoxia through its antiapoptotic action. The antiapoptotic mechanisms of HGF in hypoxia-induced endothelial cell death largely depend on Bcl-2, but not Bcl-xL and BAX:

Apoptosis↗
PubMed2001

Endothelial apoptosis induced by oxidative stress through activation of NF-kappaB: antiapoptotic effect of antioxidant agents on endothelial cells.

Injury of endothelial cells has been assumed to be an initial trigger of the development of atherosclerosis. In this study, we investigated the molecular mechanisms of endothelial cell death induced by hypoxia, which leads to oxidative stress. To study the relation between hypoxia-induced cell death and activation of nuclear factor-kappaB (NF-kappaB) in a hypoxic state, we evaluated the effect of 2 antioxidant drugs, probucol and pyrrolidine dithiocarbamate (PDTC), on human endothelial apoptosis. Although hypoxic treatment of human aortic endothelial cells resulted in a significant decrease in cell number and a significant increase in apoptotic cells compared with that of cells under normoxia (P<0.01), treatment with probucol (50 micromol/L) or PDTC (100 micromol/L) significantly attenuated the decrease in cell number (P<0.01) and was accompanied by inhibition of NF-kappaB activation. Furthermore, downregulation of bcl-2 caused by hypoxia was inhibited by these drugs. We further investigated the translocation of bax protein from the cytoplasm to the mitochondrial heavy fraction membrane, as translocation of bax protein is considered to be a determinant of apoptosis. Interestingly, we found that antioxidant treatment inhibited the translocation of bax protein caused by hypoxia. Moreover, upregulation of p53, a proapoptotic molecule, was observed in hypoxia, whereas treatment with probucol attenuated the expression of p53 accompanied by suppression of NF-kappaB activation. These data suggest functional links between p53 and endothelial apoptosis through the activation of NF-kappaB. Overall, the current study demonstrated that oxidative stress induced apoptosis in human aortic endothelial cells through the downregulation of bcl-2, translocation of bax, and upregulation of p53, probably through NF-kappaB activation. Oxidative stress may play an important role in endothelial apoptosis mediated by hypoxia, through the activation of NF-kappaB.

Anticholesteremic Agents↗
PubMed2001

Association of sodium channel gamma-subunit promoter variant with blood pressure.

The SCNN1G gene, located on human chromosome 16p12, encodes the gamma subunit of the amiloride-sensitive epithelial sodium channel, and mutations in SCNN1G can result in Liddle's syndrome or pseudohypoaldosteronism type I. We identified sequence variations in the promoter region of SCNN1G and examined the association between this polymorphism and blood pressure in a large cohort (n=4075) representing the general population in Japan. We found T(-1290)C, T(-501)G, G(-173)A, and G(-104)T polymorphisms in the promoter region of SCNN1G and confirmed the existence of T387C and T474C polymorphisms in exon 3 and the C1947G polymorphism in exon 13. Because the genotypes of the T(-1290)C, T(-501)G, G(-104)T, and T474C polymorphisms were in tight linkage disequilibrium, we selected the T474C and G(-173)A polymorphisms for an association study. The G(-173)A polymorphism of SCNN1G had a significant effect on systolic pressure (P=0.0050) and pulse pressure (P=0.0050). The AA genotype was associated with an 11 mm Hg drop in systolic pressure and an 8 mm Hg drop in pulse pressure and with a higher prevalence of hypotension (P=0.0195). A transient transfection assay using MDCK cells and human renal epithelial cells indicated that the promoter activity of the G(-173) allele was higher than that of the A(-173) allele. Although the effects of the A(-173) allele were recessive and although the AA genotype was found in just 0.7% of our study population, we observed that this variation of human SCNN1G had significant effects on blood pressure.

Adult↗
PubMed2001

Low potentiality of angiotensin-converting enzyme gene insertion/deletion polymorphism as a useful predictive marker for carotid atherogenesis in a large general population of a Japanese city: the Suita study.

BACKGROUND AND PURPOSE: Some previous studies, almost all western, have investigated whether there is a relationship between the insertion/deletion (I/D) polymorphism of the angiotensin-converting enzyme (ACE) and carotid atherosclerosis. The results, however, have not been consistently positive. Further, there have been few investigations based on a large, general population. Therefore, the present study aimed to clarify whether ACE gene deletion polymorphism was associated with carotid atherosclerosis in a large Japanese general population with a more homogeneous genetic background than Caucasian populations. METHODS: Subjects aged 30 to 86 years were randomly selected from Suita City, located in Osaka, the second largest urban area of Japan, and included 1894 men and 2137 women. With the aid of high-resolution ultrasonography, carotid atherosclerosis was evaluated using our atherosclerotic indexes of intimal-medial thickness (IMT), plaque number (PN), plaque score (PS), and percentage of stenosis of the carotid artery assessed using high-resolution B-mode ultrasonography. ACE gene I/D polymorphism was detected by polymerase chain reaction. RESULTS: There were no significant differences among the ACE genotypes for age and conventional cardiovascular risk factors, except for systolic blood pressure (SBP) and the percentage of hypertension in men. The values of IMT, PN, and PS as carotid atherosclerotic indexes were not significantly different among genotypes for either sex. After adjusting for age, body mass index, smoking habit, high-density lipoprotein cholesterol, triglycerides, presence of hypertension, presence of diabetes mellitus, and presence of hyperlipidemia, the estimated ORs for the presence of IMT >/=1.10 mm (defined as thickened IMT), according to ACE genotype (DD versus II, DD+ID versus II, and DD versus ID+II), for men were 0.80 (95% CI 0.60 to 1.23), 0.89 (0.62 to 1.29), and 0.89 (0.70 to 1.28), respectively. On the other hand, the ORs for women after the same adjustment were 0.92 (95% CI 0.58 to 1.35), 0.93 (0.59 to 1.45), and 0.91 (0.59 to 1.27), respectively. CONCLUSIONS: Our present data suggest that ACE I/D polymorphism is not potentially a useful predictive marker for carotid atherogenesis when investigated in a large and homogeneous general Japanese population of 4031 subjects, a finding similar to that in a Caucasian population study, the Perth Carotid Ultrasound Disease Assessment Study, an Australian study based on a general population using 1111 subjects.

Adult↗
PubMed2001

Regulation of phosphoinositide metabolism, Akt phosphorylation, and glucose transport by PTEN (phosphatase and tensin homolog deleted on chromosome 10) in 3T3-L1 adipocytes.

To investigate the roles of PTEN (phosphatase and tensin homolog deleted on chromosome 10) in the regulation of 3-position phosphorylated phosphoinositide metabolism as well as insulin-induced Akt phosphorylation and glucose metabolism, wild-type PTEN and its phosphatase-dead mutant (C124S) with or without an N-terminal myristoylation tag were overexpressed in Sf-9 cells and 3T3-L1 adipocytes using baculovirus and adenovirus systems, respectively. When expressed in Sf-9 cells together with the p110alpha catalytic subunit of phosphoinositide 3-kinase, myristoylated PTEN markedly reduced the accumulations of both phosphatidylinositol 3,4-bisphosphate and phosphatidylinositol 3,4,5-trisphosphate induced by p110alpha. In contrast, overexpression of the C124S mutants apparently increased these accumulations. In 3T3-L1 adipocytes, insulin-induced accumulations of phosphatidylinositol 3,4-bisphosphate and phosphatidylinositol 3,4,5-trisphosphate were markedly suppressed by overexpression of wild-type PTEN with the N-terminal myristoylation tag, but not by that without the tag. On the contrary, the C124S mutants of PTEN enhanced insulin-induced accumulations of phosphatidylinositol 3,4-bisphosphate and phosphatidylinositol 3,4,5-trisphosphate. Interestingly, the phosphorylation level of Akt at Thr308 (Akt2 at Thr309), but not at Ser473 (Akt2 at Ser474), was revealed to correlate well with the accumulation of phosphatidylinositol 3,4,5-trisphosphate modified by overexpression of these PTEN proteins. Finally, insulin-induced increases in glucose transport activity were significantly inhibited by the overexpression of myristoylated wild-type PTEN, but were not enhanced by expression of the C124S mutant of PTEN. Therefore, in conclusion, 1) PTEN dephosphorylates both phosphatidylinositol 3,4-bisphosphate and phosphatidylinositol 3,4,5-trisphosphate in vivo, and the C124S mutants interrupt endogenous PTEN activity in a dominant-negative manner. 2) The membrane targeting process of PTEN may be important for exerting its function. 3) Phosphorylations of Thr309 and Ser474 of Akt2 are regulated differently, and the former is regulated very sensitively by the function of PTEN. 4) The phosphorylation level of Ser474, but not that of Thr309, in Akt2 correlates well with insulin-stimulated glucose transport activity in 3T3-L1 adipocytes. 5) The activity of endogenous PTEN may not play a major role in the regulation of glucose transport activity in 3T3-L1 adipocytes.

3T3 Cells↗
PubMed2001

Lack of association between genetic polymorphism of CYP11B2 and hypertension in Japanese: the Suita Study.

Aldosterone synthase (CYP11B2) is a key enzyme in the biosynthesis of aldosterone. Recently, a polymorphism in the 5'-flanking region of the CYP11B2 gene [T(-344)C] has been reported to be associated with blood pressure and plasma aldosterone levels. We investigated the association between this polymorphism and hypertension in a large population-based sample of 4,000 Japanese. The genotype distribution in hypertensive subjects (n=1,535) was compared to that in normotensive subjects (n=2,514). In subjects not receiving antihypertensive medication, the influence of the genotype on blood pressure values adjusted for clinical covariates was analyzed. All analyses were performed separately for men and women. The genotype distribution did not differ between hypertensive and normotensive subjects in either men (frequency of C allele: 30.3% vs. 31.4%, p=0.48) or women (31.5% vs. 31.7%, p=0.93). There were no significant differences in systolic blood pressure, diastolic blood pressure, or pulse pressure among the three genotypes in either men or women who had not received hypertensive medication. Our data suggest that the T(-344)C polymorphism of CYP11B2 is unlikely to influence blood pressure status in the Japanese population.

Aged↗
PubMed2001

Lack of correlation between Mbo I restriction fragment length polymorphism of renin gene and essential hypertension in Japanese.

Predisposition to essential hypertension is associated with gene polymorphisms of the renin angiotensin system (RAS). Gene polymorphisms of the angiotensinogen and angiotensin converting enzyme genes are known to be risk factors for hypertension, while few studies concerning the renin gene polymorphism have been published. In the present investigation, we carried out a case control study using a Japanese population to examine the genetic influence of the renin gene on the predisposition to hypertension. Patients (n=235) recruited from outpatients at Osaka University Hospital and diagnosed with essential hypertension or receiving long-term antihypertensive medication participated in the study. Normotensive control subjects (n=510) without a history of hypertension and without diabetes mellitus were recruited from the same population, and were sex-matched with experimental subjects. A polymorphism in intron 9 of the human renin gene was determined as the Mbo I restriction fragment length polymorphism (Mbo I-RFLP). There was no significant association between Mbo I-RFLP of the renin gene and predisposition to essential hypertension in Japanese (p>0.05, chi2=2.1). These results suggest that the Mbo I (+) allele of the renin gene does not increase the risk for hypertension in Japanese.

Aged↗
PubMed2001

The aldehyde dehydrogenase 2 gene is a risk factor for hypertension in Japanese but does not alter the sensitivity to pressor effects of alcohol: the Suita study.

Excessive alcohol consumption is a potent risk factor for high blood pressure. About half of Japanese show an extremely high sensitivity to alcohol, which is due to a genetic deficiency in an isoenzyme of aldehydede-hydrogenase with a low Km (ALDH2). It is possible that the effects of alcohol consumption on blood pressure differ according to the ALDH2 genotype. The purpose of the present study was to assess the influence of the ALDH2 genotype on the pressor effects of alcohol. The influence of the ALDH2 genotype on blood pressure was investigated in a large cohort (4,000 subjects) representing the general population in Japan. The genotype was determined by the TaqMan method. The genotype was significantly associated with alcohol consumption, gamma-GTP level, and HDL cholesterol level in both males and females. The odds ratio for the presence of hypertension for the Glu/Glu genotype in comparison to other genotypes was 1.67 (p< 0.0001, odds ratio=1.37-2.08, 95% confidence interval) among males. In contrast, the ALDH2 genotype had no significant effects on blood pressure among females. To investigate whether the ALDH2 genotype affected the sensitivity to the pressor effects of alcohol, we analyzed the effects of the ALDH2 genotype (Lys/Lys+Lys/Glu=0, Glu/Glu=1) and the level of alcohol consumption on blood pressure values after adjusting for age and BMI (residuals after adjusting for age and BMI). Among males, while the level of alcohol consumption significantly affected systolic, diastolic and pulse pressure, no significant interaction was observed between the ALDH2 genotype and the level of alcohol consumption in determining blood pressure levels. These results suggest that the Glu/Glu genotype is a potent risk factor for hypertension among males mainly through its association with the level of alcohol consumption, and that the ALDH2 genotype does not affect the sensitivity to the pressor effects of alcohol.

Adult↗
PubMed2001

Differences in mechanisms between weight loss-sensitive and -resistant blood pressure reduction in obese subjects.

This study was conducted to clarify the mechanisms involved in the sensitivity for blood pressure (BP) reduction in response to weight loss. In particular, we focused on the contributions of sympathetic nervous system activity and fasting plasma leptin and insulin levels to BP levels during weight loss in obese subjects with weight loss-sensitive and -resistant BP reduction. Sixty-one young, obese untreated hypertensive men (HT) and 52 obese normotensive men (NT) were enrolled in a weight loss program consisting of a low caloric diet and aerobic exercise over a 24-week period. At entry and at week 24, body mass index (BMI), BP, plasma norepinephrine (NE), leptin and insulin were measured. Successful weight loss and BP reduction were respectively defined as a more than a 10% reduction in BMI or mean BP from baseline at week 24. More than 60% of subjects in either group successfully achieved weight loss by this definition. The percentage of subjects who successfully achieved BP reduction was higher (64%) among those subjects who achieved weight loss than among those who did not (22%). Plasma NE level at entry in subjects who failed to achieve BP reduction despite weight loss was significantly higher than that in subjects who succeeded in BP reduction. Plasma leptin and insulin levels were similar between subjects with and without BP reduction. In addition, the absolute decrement and percent decrement in plasma NE in subjects who succeeded in BP reduction were significantly greater than those in subjects who failed to reduce their BP. Absolute and percent decrements in plasma leptin and insulin were similar in both groups. These results suggest that individuals who are resistant to weight loss-induced BP reduction have more sympathetic overactivity both at the outset of and during weight loss.

Adult↗
PubMed2001

A family with von Hippel-Lindau disease revealed by pheochromocytoma.

Von Hippel-Lindau (VHL) disease is an inherited neoplastic disease characterized by a predisposition to develop retinal angiomas, central nervous system hemangioblastomas, renal cell carcinomas, pancreatic cysts and pheochromocytomas. Recently, we encountered three members of the same family who each had both VHL disease and pheochromocytoma. As in all three patients we suspected pheochromocytoma, the diagnosis of VHL disease should be considered. The possible presence of VHL disease was initially investigated in all three patients based on the presence of pheochromocytoma. A mutational analysis of the VHL gene revealed the presence of a missense mutation, consisting of a G to A transversion, at nucleotide 713 in all three patients. This germline point mutation in the VHL gene is often detected in type 2 VHL disease with pheochromocytoma. Genetic analysis seems to be useful for early detection of VHL disease, even when the formal criteria for diagnosis of this disease are lacking.

Adrenal Gland Neoplasms↗
PubMed2001

Effects of antihypertensive drugs and gene variants in the renin-angiotensin system.

Many genes and environmental factors are involved in the pathogenesis of hypertension, but the exact cause of essential hypertension has not yet been clarified. Gene polymorphism of the renin-angiotensin system (RAS) is one of the candidates. In the current study, we examined whether there was a correlation between the gene polymorphisms in RAS and either the choice of antihypertensive drugs or their efficacy. Subjects with essential hypertension (n=299) were recruited from among the outpatients of Osaka University Hospital and provided their informed consent for genetic analysis. Physicians freely chose the antihypertensive drugs and adjusted its dose until the patient's blood pressure was well controlled. The efficacy of each antihypertensive drug was estimated using the following formula: ABP=BP 1 (before treatment) - BP 2 (after treatment)/BP 1 x 100 (%). Gene variants in RAS were determined using PCR or PCR-RFLP (restriction fragment of polymorphism). The gene polymorphisms of RAS were not associated with delta SBP or ADBP. However, the mean ASBP in subjects with a deletion homozygote of the angiotensin converting enzyme gene (ACE/DD) was significantly lower (p<0.05) than that in patients with an insertion I allele of the ACE gene. The gene polymorphisms of RAS did not significantly affect the choice of antihypertensive drugs. Even though gene polymorphism in the renin angiotensin system was not a major factor in the antihypertensive therapy, the determination of genotype might be of help in the management of essential hypertension.

Antihypertensive Agents↗
PubMed2001

Tolerability and safety of a calcium channel blocker in comparison with a diuretic in the treatment of elderly patients with hypertension: secondary analysis of the NICS-EH.

A randomized prospective controlled study, the National Interventional Cooperative Study in Elderly Hypertensives (NICS-EH), previously demonstrated that the preventive effect of the long-acting calcium channel blocker nicardipine on the cardiovascular endpoint was similar to that of the diuretic, trichlormethiazide. The present report is a sub-analysis in which we compare the tolerability and safety of the calcium channel blocker with that of a diuretic in the long-term treatment of elderly hypertensives. A total of 429 elderly patients with hypertension were assigned to the nicardipine group or the diuretic group by the double-dummy method and were followed up for 5 years. Two hundred four patients in the nicardipine group and 210 patients in the diuretic group were analyzed. The incidences of fatal and nonfatal cardiovascular (CV) events in the two groups were comparable, and there was no significant difference in the cumulative event-free rate. However, the total incidence of adverse reactions, including non-CV events and unfavorable BP changes, was 31 cases (15.2%) in the nicardipine group, which was significantly lower than the 47 cases (22.4%) in the diuretic group (log-rank: p=0.026, G. Wilcoxon: p=0.01). The total number of medical endpoints, including CV events, the withdrawal of the patient from the study, was 52 (25.5%) in the nicardipine group, which was significantly lower than the 65 (31.0%) in the diuretic group (log-rank: p=0.078, G. Wilcoxon: p=0.044). It was concluded that sustained-release nicardipine is better tolerated, as it exhibits a lower incidence of medical-related withdrawals such as adverse drug reactions, non-cardiovascular events and unfavorable BP responses during the treatment.

Aged↗
PubMed2001

Sequence analysis of candidate genes for common susceptibility to type 1 and type 2 diabetes in mice.

Although type 1 and type 2 diabetes are regarded as clinically distinct diseases, several lines of evidence have suggested common genetic factors between the two types of diabetes. The non-obese diabetic (NOD) mouse, an animal model of type 1 diabetes, and the Nagoya-Shibata-Yasuda (NSY) mouse, a model of type 2 diabetes, are derived from the same outbred colony, Jcl:HCR, suggesting a shared susceptibility between the two types of diabetes in mice. Genetic as well as functional studies have supported the possibility that Tcf2, which encodes the transcription factor, hepatocyte nuclear factor 1beta (HNF-1beta), is a candidate gene for the common susceptibility between NSY and NOD mice. Txn, encoding thioredoxin which is a redox (reduction/oxidation)-active protein, is also a positional and functional candidate for a common susceptibility gene. To investigate whether either of these two genes is a common susceptibility gene, the coding nucleotide sequences of these two genes were compared among the NSY, NOD and control C3H strains. The coding sequence of Tcf2 of the NOD mouse was identical to that of the C3H mouse, but was different from that of the NSY mouse. The coding sequence of Txn was identical in the three strains. These data suggest that neither of the two genes is a common susceptiblity gene between type 1 and type 2 diabetes in mice.

Animals↗
PubMed2001

Potential of microvascular reperfusion with adjunctive pharmacological intervention: its impact on myocardial perfusion and functional outcomes in patients with acute myocardial infarction.

One of the major limitations of reperfusion therapy in acute myocardial infarction (AMI) is the presentation of no-reflow phenomenon. In 25 to 30% of patients with AMI. myocardial blood flow is occasionally profoundly reduced, even after coronary recanalisation, because of microvascular dysfunction so-called no-reflow phenomenon. Patients with this phenomenon are regarded as a high risk group among patients with reperfused AMI. Clinical studies using myocardial contrast echocardiography have demonstrated that intracoronary injection of calcium antagonists or potassium channel agonists in conjunction with coronary reperfusion can augment myocardial blood flow and that this was associated with better functional and clinical outcomes than with percutaneous transluminal coronary angioplasty alone. Thus, it is possible to prevent reperfusion injury and improve cardiac function using a adjunctive pharmacological intervention, either intravenously or by infusion directly into the coronary artery.

Angioplasty, Balloon, Coronary↗
PubMed2001

Insulin resistance with enhanced insulin signaling in high-salt diet-fed rats.

Previous clinical studies showed an apparent correlation between hypertension and insulin resistance, and patients with diabetes are known to have increased blood pressure responsiveness to salt loading. To investigate the effect of high salt intake on insulin sensitivity and the insulin signaling pathway, a high-salt diet (8% NaCl) or a normal diet was given to 7-week-old SD rats for 2 weeks. High salt-fed rats developed slightly but significantly higher systolic blood pressure than controls (133 +/- 2 vs. 117 +/- 2 mmHg, P < 0.001), with no change in food intake or body weight. High salt-fed rats were slightly hyperglycemic (108.5 +/- 2.8 vs. 97.8 +/- 2.5 mg/dl, P = 0.01) and slightly hyperinsulinemic (0.86 +/- 0.07 vs. 0.61 +/- 0.06 ng/ml, P = 0.026) in the fasting condition, as compared with controls. Hyperinsulinemic-euglycemic clamp study revealed a 52.7% decrease in the glucose infusion rate and a 196% increase in hepatic glucose production in high salt-fed rats, which also showed a 66.4% decrease in 2-deoxyglucose uptake into isolated skeletal muscle and a 44.5% decrease in insulin-induced glycogen synthase activation in liver, as compared with controls. Interestingly, despite the presence of insulin resistance, high salt-fed rats showed enhanced insulin-induced tyrosine phosphorylation of insulin receptor substrate (IRS)-1, IRS-2 (liver and muscle), and IRS-3 (liver only). Phosphatidylinositol (PI) 3-kinase activities associated with IRS and phosphotyrosine in the insulin-stimulated condition increased 2.1- to 4.1-fold, as compared with controls. Insulin-induced phosphorylation of Ser-473 of Akt and Ser-21 of glycogen synthase kinase-3 also increased 2.9- and 2-fold, respectively, in the liver of the high salt-fed rats. Therefore, in both the liver and muscle of high salt-fed rats, intracellular insulin signaling leading to PI 3-kinase activation is enhanced and insulin action is attenuated. The hyperinsulinemic-euglycemic clamp study showed that decreased insulin sensitivity induced with a high-salt diet was not reversed by administration of pioglitazone. The following can be concluded: 1) a high-salt diet may be a factor promoting insulin resistance, 2) the insulin-signaling step impaired by high salt intake is likely to be downstream from PI 3-kinase or Akt activation, and 3) this unique insulin resistance mechanism may contribute to the development of diabetes in patients with hypertension.

Animals↗
PubMed2001

Phosphorylation of p38 mitogen-activated protein kinase downstream of bax-caspase-3 pathway leads to cell death induced by high D-glucose in human endothelial cells.

Because high D-glucose significantly stimulates endothelial cell death, we examined the molecular mechanisms of high D-glucose-induced endothelial apoptosis. Treatment of human aortic endothelial cells with high D-glucose (25 mmol/l), but not mannitol and L-glucose, resulted in a significant decrease in cell number and a significant increase in apoptotic cells as compared with a physiological concentration (5 mmol/l). Interestingly, high D-glucose treatment significantly increased bax protein, accompanied by translocation of bax protein from cytosol to mitochondria-enriched heavy membrane fraction. In contrast, the expression and distribution of bcl-2 protein were not altered by high D-glucose. In addition, the activity of caspase-3 proteases was increased after exposure to high glucose, whereas caspase inhibitors prevented endothelial cell death induced by high D-glucose. On the other hand, p38 mitogen-activated protein kinase (MAPK) was markedly phosphorylated and showed sustained phosphorylation after stimulation. A specific inhibitor of p38 MAPK, SB 203580, and the overexpression of kinase-inactive p38 MAPK significantly attenuated cell death induced by high D-glucose in human aortic endothelial cells, whereas at 6 h after high D-glucose treatment, SB 203580 and overexpression of kinase-inactive p38 MAPK did not attenuate caspase-3 activation induced by high D-glucose. Importantly, caspase inhibitors significantly attenuated the sustained phosphorylation of p38 MAPK induced by high D-glucose. Thus, we finally focused the MAPK kinase (MEK) kinase 1 (MEKK1) to further examine the cross-talk between p38 MAPK and the bax-caspase proteases pathway. High D-glucose treatment induced MEKK1 cleavage, whereas caspase inhibitors significantly attenuated the cleavage. Importantly, kinase-inactive MEKK1 also blocked the phosphorylation of p38 MAPK induced by high D-glucose. Here, we demonstrated that high D-glucose induced apoptosis in human endothelial cells through activation of the bax-caspase proteases pathway and through phosphorylation of p38 MAPK mediated by MEKK1. Phosphorylation of p38 MAPK downstream of the bax-caspase pathway may play a pivotal role in endothelial apoptosis mediated by high D-glucose.

Animals↗
PubMed2001

Antiatherogenic mitochondrial genotype in patients with type 2 diabetes.

OBJECTIVE: To evaluate the significance of a longevity-associated mitochondrial genotype (Mt5178A) derived from a C --> A transversion at nucleotide position 5178 of mitochondrial DNA, which causes a Leu-to-Met substitution within the NADH dehydrogenase subunit 2 gene, in type 2 diabetic subjects. RESEARCH DESIGN AND METHODS: Mt5178 typing was done by polymerase chain reaction-restriction fragment-length polymorphism with the restriction enzyme AluI in 1,148 type 2 diabetic Japanese subjects, and the results were compared with the clinical characteristics. Then, the association of Mt5178 type with early atherosclerotic changes of the bilateral carotid arteries on ultrasonography was assessed in 412 diabetic subjects randomly selected from the original 1,148 type 2 diabetic subjects, while maintaining the same frequency of Mt5178A and Mt5178C. RESULTS: The frequency of Mt5178A in the type 2 diabetic subjects (454 of 1,148; 40%) was not different from that previously found in healthy blood donors (114 of 252; 45%). Clinical characteristics regarding diabetes were not significantly different between the Mt5178A group (n = 454) and the Mt5178C group (n = 694). However, the mean intima-media thickness (IMT) at six sites in the bilateral carotid arteries was significantly smaller in the Mrt5178A group than in the Mt5178C group (0.906 +/- 0.018 vs. 0.995 +/- 0.021 mm, mean +/- SEM, P = 0.022), and the Mt5178 type was significantly correlated with both the mean IMT and the presence of plaque on multiple regression analysis and discriminant analysis. CONCLUSIONS: The Mt5178A genotype may be unrelated to the etiology of type 2 diabetes. However, Mt5178A seems to have an antiatherogenic effect, at least in type 2 diabetic individuals.

Adult↗