Sangmee Ahn Jo

Nitric Oxide Production and Regulation of Endothelial Nitric-oxide Synthase Phosphorylation by Prolonged Treatment with Troglitazone EVIDENCE FOR INVOLVEMENT OF PEROXISOME PROLIFERATOR-ACTIVATED RECEPTOR (PPAR) γ-DEPENDENT AND PPARγ-INDEPENDENT SIGNALING PATHWAYS

Recently, peroxisome proliferator-activated receptor γ (PPARγ) ligands have been reported to increase endothelial NO, but the signaling mechanisms involved are unknown. Using troglitazone, a PPARγ ligand known as an antidiabetic compound, we investigated the molecular mechanism of its effect on NO production in bovine aortic endothelial cells. Troglitazone increased endothelial NO production in a dose- and time-dependent manner with no alteration in endothelial nitric-oxide synthase (eNOS) expression. The maximal increase (∼3.1-fold) was achieved with 20 μm troglitazone treatment for 12 h, and this increase was accompanied by increases in the expression of vascular endothelial growth factor (VEGF) and its receptor, KDR/Flk-1, and in Akt phosphorylation. Analysis with antibodies specific for each phosphorylated site demonstrated that troglitazone (20 μm treatment for 12 h) significantly increased both the phosphorylation of Ser1179 of eNOS (eNOS-Ser1179) and the dephosphorylation of eNOS-Ser116 but did not alter eNOS-Thr497 phosphorylation. Treatment with anti-VEGF antibody to scavenge the increased VEGF induced by troglitazone partially inhibited troglitazone-stimulated NO production. This was accompanied by the attenuation of troglitazone-stimulated increases in the phosphorylation of Akt and eNOS-Ser1179 with no alteration in eNOS-Ser116 dephosphorylation. We also found that bisphenol A diglycidyl ether, a PPARγ antagonist, partially inhibited troglitazone-stimulated NO production with a concomitant reduction in VEGF-KDR/Flk-1-Akt-mediated eNOS-Ser1179 phosphorylation but with no alteration in eNOS-Ser116 dephosphorylation induced by troglitazone. Taken together, our results demonstrate that prolonged treatment with troglitazone increases endothelial NO production by at least two independent signaling pathways: PPARγ-dependent, VEGF-KDR/Flk-1-Akt-mediated eNOS-Ser1179 phosphorylation and PPARγ-independent, eNOS-Ser116 dephosphorylation.

Validation of the Patient Health Questionnaire-9 Korean version in the elderly population: the Ansan Geriatric study

OBJECTIVE We evaluated the diagnostic validity of the 9-item depression module of the Patient Health Questionnaire-9 (PHQ-9) in elderly Korean patients and suggest an optimal cutoff score to screen for major depressive disorders. METHOD The PHQ-9 and an elderly health questionnaire were administered to 1060 subjects older than 60 years, chosen using a stratified random sample of the community. The PHQ-9 was measured and compared with the Geriatric Depression Scale, Center for Epidemiological Studies Depression Scale, and Beck Depression Inventory scores. Reliability and validity tests, factor analysis, and receiver operating characteristic curve analysis were performed. RESULTS The PHQ-9 indicated that 175 subjects had depressive disorders, and 885 subjects were rated as healthy. The PHQ-9 showed significant positive internal consistency (r = 0.88) and test-retest reliability (r = 0.60). The convergent validity with Geriatric Depression Scale and Center for Epidemiological Studies Depression Scale was significantly positive (r = 0.74 and 0.66, respectively). We suggest a score of 5 as the optimal cutoff point when screening for depressive disorders using the PHQ-9. CONCLUSIONS The Korean version of the PHQ-9 is an appropriate diagnostic tool for depression, and a score of 5 is the optimal cutoff for Korean elderly subjects. Screening for depression in the elderly population using the PHQ-9 would be valuable when medically ill patients show depressive symptoms in a primary health care setting.

The cutoff values of visceral fat area and waist circumference for identifying subjects at risk for metabolic syndrome in elderly Korean: Ansan Geriatric (AGE) cohort study.

BackgroundIn Korea, the cutoff values of waist circumference (WC) for the identification of metabolic syndrome (MetS) were suggested to be 90 cm for men and 85 cm for women based on the analysis mainly in middle-aged adults. As aging is associated with increased fat, especially abdominal visceral fat, the cutoff value of WC may differ according to age. In addition, the usefulness of visceral abdominal fat area (VFA) to predict MetS in the elderly has not been studied yet. We aimed to suggest WC and VFA criteria and to compare the predictability of WC and VFA to identify people at risk for MetS.MethodsA total of 689 elderly subjects aged ≥63 years (308 men, 381 women) were chosen in this cross-sectional study from an ongoing, prospective, population-based study, the Ansan Geriatric (AGE) cohort study. VFA was measured by single slice abdominal computed tomography scanning. The metabolic risk factors except WC (plasma glucose, blood pressure, serum triglycerides and HDL cholesterol levels) were defined using modified NCEP-ATP III criteria. We estimated the accuracy of VFA and WC for identifying at least two of these factors by receiver operating characteristic (ROC) curve analysis.ResultsTwo hundred three of 308 men and 280 of 381 women had ≥2 metabolic risk factors. The area under the ROC curve (AUC) value for VFA to predict the presence of ≥2 metabolic risk factors was not significantly different from that for WC (men, 0.735 and 0.750; women, 0.715 and 0.682; AUC values for VFA and WC, respectively). The optimal cutoff points for VFA and WC for predicting the presence of ≥2 metabolic risk factors were 92.6 cm2 and 86.5 cm for men and 88.9 cm2 and 86.5 cm for women.ConclusionWC had comparable power with VFA to identify elderly people who are at risk for MetS. Elderly Korean men and women had very similar cutoff points for both VFA and WC measurements for estimating the risk of MetS. Age-specific cutoff point for WC might be considered to identify subjects at risk for MetS.

Lack of evidence for contribution of Glu298Asp (G894T) polymorphism of endothelial nitric oxide synthase gene to plasma nitric oxide levels

INTRODUCTION Both positive and negative associations between a rare allele of 27-bp repeat polymorphism in intron 4 of endothelial nitric oxide synthase and plasma nitric oxide (NO) levels were previously reported, and further, these conflicting results were suggested to be partly accounted for smoking status of subjects. However, the genetic contribution of Glu298Asp (G894T) polymorphism to plasma NO levels with respect to smoking status has not been published. METHODS In a group of 411 healthy Korean subjects aged 19-81 years, the end product of NO (NO(x): nitrite plus nitrate) as an index of plasma NO levels was measured by the Griess method. The genotypes of G894T polymorphism were determined by the banding patterns on gel electrophoresis after restriction enzyme digestion. RESULTS Comparison of plasma NO(x) levels revealed no significant differences across the genotypes and alleles of G894T polymorphism, which is independently of smoking status. However, significant differences in plasma NO(x) levels between nonsmokers and smokers were observed (P = 0.0040). Furthermore, only the common G allele was found to be responsible for these differences. Multiple regression analysis showed that the most independent contributing factor for plasma NO(x) levels was smoking (P = 0.0119) and followed by triglycerides (P = 0.0384). CONCLUSIONS Our results indicate no substantial effect of G894T polymorphism on the variance of plasma NO(x) levels in healthy Korean population.

Identification of peripheral inflammatory markers between normal control and Alzheimer's disease

BackgroundMultiple pathogenic factors may contribute to the pathophysiology of Alzheimers disease (AD). Peripheral blood markers have been used to assess biochemical changes associated with AD and mild cognitive impairment (MCI) and involved in their pathophysiology.MethodsPlasma samples and clinical data were obtained from participants in the Ansan Geriatric Study (AGE study). Plasma concentrations of four candidate biomarkers were measured in the normal control (NC), MCI, and AD group: interleukin-8 (IL-8), IL-10, monocyte chemoattractant protein-1 (MCP-1), and tumor necrosis factor-α (TNF-α).Body mass index (BMI), MMSE (Mini Mental State Examination), CDR(Clinical Dementia Rating) score and homocystein level were recorded with social and demographic information.ResultsTotal of 59 subjects were randomly selected for this analysis [NC (n = 21), MCI(n = 20) and AD(n = 18)]. In demographic data, educational year was correlated with the diagnosis states (p< 0.0001). No significant differences in cardiovascular disease, BMI and use of NSAIDs were found in MCI or AD group compared with NC group, respectively. The involvement of inflammatory illness or conditions in subjects, WBC count, fibrinogen and homocystein of the three groups, but no significant differences were found in each groups. The plasma IL-8 level was lower in MCI and AD patients compared with the normal control group (respectively, p < 0.0001). The MCI and AD patients had similar MCP-1, IL-10, and TNF-α level.ConclusionsOur study suggests the existence of an independent and negative relationship between plasma IL-8 levels and functional status in MCI and AD patients.

Smoking status-dependent association of the 27-bp repeat polymorphism in intron 4 of endothelial nitric oxide synthase gene with plasma nitric oxide concentrations.

BACKGROUND Both positive and negative associations between a rare allele of 27-bp repeat polymorphism (eNOS4b/a polymorphism) in intron 4 of endothelial nitric oxide synthase and plasma nitric oxide (NO) concentrations were previously reported. Although these conflicting results were suggested to be partly accounted for smoking status of subjects, no further studies have been accomplished. METHODS We analyzed eNOS4b/a polymorphism in a group of 393 healthy Korean subjects and measured their plasma nitrite and nitrate (NO(x)) concentrations. NO(x) concentrations were measured by the Griess method and the genotypes of eNOS4b/a polymorphism determined by the banding pattern on gel electrophoresis. RESULTS The frequency of eNOS4a allele in this study was 11.6%. The plasma NO(x) concentrations (in micromol/l) in subjects with eNOS4a allele was found to be significantly higher relative to those in eNOS4b allele (49.68 +/- 18.62 and 55.25 +/- 20.87, respectively, P < 0.05), which was valid only in smokers. Multiple regression analysis revealed that the most predictive contributing factor for plasma NO(x) concentrations was eNOS4a allele (P < 0.01), followed by smoking (P < 0.05), total cholesterol (P < 0.05), and triglycerides (P < 0.05). CONCLUSION Our data indicate that there is substantial effect of eNOS4b/a polymorphism on the variance of plasma NO(x) concentrations in Korean population and that this effect is dependent on smoking status.

SUMO1 modulates Aβ generation via BACE1 accumulation

Accumulation of disease-related proteins is a characteristic event observed in the pathogenesis of neurodegenerative diseases. β-secretase (BACE)-1, which initiates generation of β-amyloid (Aβ), is increased in the Alzheimers diseased brain. However, the mechanisms of BACE1 accumulation in Alzheimers disease are largely unknown. In this report, we found that small ubiquitin-like modifier (SUMO)-1 interacts with the dileucine motif of BACE1 and regulates the level of BACE1 protein. This was proved by the coimmunoprecipitation, and gain or loss of function experiments. Altering 3 SUMO isoforms affects BACE1 protein levels, and consequently results in altered amyloid precursor protein processing and Aβ generation. BACE1 levels were increased in response to Aβ or apoptosis, but not in cells lacking SUMO1. Aβ increased SUMO1 protein levels in rat cortical neurons. Moreover, SUMO1 immunoreactivity was increased in the amyloid precursor protein transgenic mice. Furthermore, the C-terminus fragments of BACE1 containing dileucine motif reduced Aβ generation by SUMO1 overexpression. Our study indicates SUMO1 is not only a novel and potent regulator of BACE1 accumulation and Aβ generation but also a potential therapeutic target for Alzheimers disease.

Exercise ameliorates cognition impairment due to restraint stress-induced oxidative insult and reduced BDNF level.

We assessed whether chronic treadmill exercise attenuated restraint stress-induced cognition impairment. Although serum corticosterone was not significantly altered by exercise, the restraint-induced increases in hippocampal malondialdehyde (MDA) and 4-hydroxynonenal (HNE) were reduced by chronic exercise. The exercise paradigm also reversed stress-induced reductions in brain-derived neurotrophic factor (BDNF), which increased cAMP response element-binding protein (CREB) and AKT activation. We verified the relationship between oxidative stress and BDNF signaling by treating primary hippocampal cultures with hydrogen peroxide (H2O2), which reduced BDNF and phosphorylated CREB and AKT (p-CREB, p-AKT) in a dose-dependent manner. Notably, pretreatment with N-acetylcysteine (NAC) reversed these decreases in a dose-dependent manner. These findings suggest that chronic exercise can ameliorate repeated stress-induced cognitive impairment by detoxifying reactive oxygen species (ROS) in the hippocampus and activating BDNF signaling.

Study design and methods of the Ansan Geriatric Study (AGE study)

BackgroundThe overall objective of the Ansan Geriatric Study (AGE study) was to describe the prevalence, incidence, and related risk factors for geriatric diseases in elderly Koreans.Methods/DesignThe AGE study was designed as a population-based prospective cohort study on health, aging, and common geriatric diseases of elderly Koreans aged 60 to 84 years. The inception cohort was recruited in May 2002. The first-wave and second-wave studies were performed using uniform and structured procedures. At the screening study, 2,767 participants were enrolled. Participants (1391 in the first wave study and 841 in the second wave study) were recruited and completed the evaluation. The prevalence of geriatric disease and related factors in elderly Koreans were estimated.DiscussionHere, we report the design and sampling participants, measurement tools, and characteristics of the AGE study. This cohort study will allow a detailed study of the longitudinal comprehensive data on health information of elderly Koreans, thereby contributing to policy formulation and planning of health, welfare management, and other social services in Korea.

Hypoxia-Induced Endothelial NO Synthase Gene Transcriptional Activation Is Mediated Through the Tax-Responsive Element in Endothelial Cells

Although hypoxia is known to induce upregulation of endothelial NO synthase (eNOS) gene expression, the underlying mechanism is largely unclear. In this study, we show that hypoxia increases eNOS gene expression through the binding of phosphorylated cAMP-responsive element binding (CREB) protein (pCREB) to the eNOS gene promoter. Hypoxia (1% O2) increased both eNOS expression and NO production, peaking at 24 hours, in bovine aortic endothelial cells, and these increases were accompanied by increases in pCREB. Treatment with the protein kinase A inhibitor H-89 or transfection with dominant-negative inhibitor of CREB reversed the hypoxia-induced increases in eNOS expression and NO production, with concomitant inhibition of the phosphorylation of CREB induced by hypoxia, suggesting an involvement of protein kinase A/pCREB-mediated pathway. To map the regulatory elements of the eNOS gene responsible for pCREB binding under hypoxia, we constructed an eNOS gene promoter (−1600 to +22 nucleotides) fused with a luciferase reporter gene [pGL2-eNOS(−1600)]. Hypoxia (for 24-hour incubation) increased the promoter activity by 2.36±0.18-fold in the bovine aortic endothelial cells transfected with pGL2-eNOS(−1600). However, progressive 5′-deletion from −1600 to −873 completely attenuated the hypoxia-induced increase in promoter activity. Electrophoretic mobility shift, anti-pCREB antibody supershift, and site-specific mutation analyses showed that pCREB is bound to the Tax-responsive element (TRE) site, a cAMP-responsive element–like site, located at −924 to −921 of the eNOS promoter. Our data demonstrate that the interaction between pCREB and the Tax-responsive element site within the eNOS promoter may represent a novel mechanism for the mediation of hypoxia-stimulated eNOS gene expression.