Da-Jun Chai

Fujian Medical University, Min-hou, Fujian, China

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Publications (6)12.44 Total impact

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    ABSTRACT: Retinoid X receptor (RXR) has been demonstrated to play an important role in cardiac development and has been implicated in cardiovascular diseases. This study aimed to examine the effects of RXRα agonist bexarotene on pathological left ventricular hypertrophy (LVH) in a spontaneously hypertensive rat (SHR) model and the underlying mechanism. WKY rats served as controls. SHRs were randomized into 3 groups at the age of 4 weeks and were treated (once daily for 12 weeks) with either bexarotene (30 or 100mg/kg body weight) or vehicle alone. Echocardiography was performed to determine cardiac structure and function. Neonatal cardiomyocytes were treated with AngII (10(-7) mmol/L) with or without the indicated concentration of RXRα ligand 9-cis-RA. The protein abundances of β-actin, RXRα, LKB1, phospho-LKB1, AMPK, phospho-AMPK, P70S6K, phospho-P70S6K, ACE, and AT1 receptor were measured along with blood pressure, body weight and angiotensin II (Ang II) levels. The effects of LKB1 downregulation by LKB1 small, interfering RNA were examined. Treatment of SHRs with bexarotene resulted in significant inhibition of LVH without eliminating hypertension. Immunoblot with heart tissue homogenates from SHRs revealed that bexarotene activated the LKB1/AMPK signaling pathway and inhibited p70S6K. However, the increased Ang II levels in SHR serum and heart tissue were not reduced by bexarotene treatment. Treatment of cardiomyocytes with Ang II resulted in significantly reduced LKB1/AMPK activity and increased p70S6K activity. 9-cis-RA antagonized Ang II-induced LKB1/AMPK and p70S6K activation changes in vitro. RXR agonists prevent the inhibition of the LKB1/AMPK/p70S6K pathway and regulate protein synthesis to reduce LVH. This antihypertrophic effect of bexarotene is independent of blood pressure.
    American Journal of Hypertension 03/2014; 27(8). DOI:10.1093/ajh/hpu017 · 2.85 Impact Factor
  • Ting-Xing Zhang · Jun-Xia Xu · Feng Peng · Da-Jun Chai · Jin-Xiu Lin ·
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    ABSTRACT: Background: To investigate the effects of a single dose of metformin (MF) on endothelium-dependent vasodilatation and serum antioxidant and free fatty acid levels in patients with primary hypertension (PH) after an acute glucose load. Materials and methods: Patients with untreated PH were randomized to a no-metformin group (PH, n = 34) and a metformin group (PH+ MF, n = 28) who received a single dose of 500 mg metformin before testing. Healthy volunteers (n = 31) served as a control group. Brachial artery endothelium-dependent flow-mediated vasodilatation (FMD) was determined at 0, 1, 2 and 3 h after glucose load. Levels of serum superoxide dismutase (SOD), total antioxidant capacity (T-AOC), anti-superoxide anion free radical (AntiO2) and free fatty acids (FFA) were measured. Results: The FMD in the PH group decreased significantly 1 h after glucose load (PH: 10.9 ± 2.9% vs 13.67 ± 3.42% before glucose load). Metformin inhibited the effects of glucose load on FMD. At 1 h after acute glucose load, the concentrations of SOD, T-AOC and AntiO2 in the PH group decreased significantly compared with their fasting levels, and metformin inhibited the acute glucose load-induced decline in SOD and T-AOC levels. Conclusions: Metformin can prevent transient endothelial dysfunction caused by acute glucose load in patients with PH.
    Blood pressure 11/2012; 22(2). DOI:10.3109/08037051.2012.732761 · 1.81 Impact Factor
  • Ting-Xing Zhang · Feng Peng · Da-Jun Chai · Jin-Xiu Lin ·
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    ABSTRACT: INTRODUCTION: This study investigated the effects of combined glucose and fat load on glucose and lipid metabolism, as well as on vascular endothelial function, in hypertensive patients. METHODS AND RESULTS: A total of 98 hypertensive patients were randomly divided into 3 groups that received an oral fat tolerance test (OFTT), an oral glucose tolerance test (OGTT) or a combined oral glucose and fat tolerance test (OGFTT). Endothelium-dependent flow-mediated brachial artery dilation (FMD) was measured by vascular ultrasound and was used as an indicator of vascular endothelial function. There were no significant differences in demographics or clinical characteristics among the 3 groups before the study. Immediately after the OGFTT, the serum triglyceride levels and the area under the curve for serum glucose in the OGFTT group were not significantly different from those in the other 2 groups. However, the 1-hour FMD in the OGFTT group was significantly reduced compared with that of the OGTT group (5.45 ± 0.75 versus 9.46 ± 1.32, P < 0.05), and the 4-hour FMD in the OGFTT group was also significantly reduced compared with the OFTT group (8.56 ± 1.09 versus 9.76 ± 2.00, P < 0.05). CONCLUSION: A combined glucose and fat load has a cumulative effect on vascular endothelial dysfunction in hypertensive patients.
    The American Journal of the Medical Sciences 03/2012; 344(6). DOI:10.1097/MAJ.0b013e31824a0164 · 1.39 Impact Factor
  • Xiao-Rong Zheng · Da-Jun Chai · Feng Peng · Jun-Xia Xu · Jin-Xiu Lin ·
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    ABSTRACT: To explore the influence of acute glucose and fat loading on endothelium dependent flow-mediated vasodilation (FMD) in patients with essential hypertension (EH). Patients with EH were randomly divided into three groups: oral glucose loading alone (n = 26), oral standardized fat loading alone (n = 38), combined glucose and fat loading (n = 34). FMD of the brachial artery was assessed by high resolution ultrasound technique respectively. (1) Compared to control group, postprandial abnormal serum triglyceride metabolism was evidenced and FMD was significantly reduced and the lowest FMD occurred at 4 hours and returned to the baseline level at 8 hours post fat loading alone in EH patients. (2) GS-AUC and 1 hour glucose were significantly higher in EH patients than in controls (all P < 0.05), FMD was also significant decreased (-31.4%) at 1 hour and returned to baseline level at 2 hours post oral glucose loading. (3) After combined glucose and fat loading, FMD at 1 hour (5.45 ± 1.93 vs. 9.46 ± 3.33, P < 0.05) was significantly lower than that in glucose loading alone and FMD at 4 hours (7.98 ± 1.64 vs. 9.66 ± 2.26, P < 0.05), was also lower than that in fat loading alone in EH patients. (4) FMD was negatively correlated with SBP, GS-AUC, DBP, TG-AUC (γ = -0.46, -0.44, -0.41, -0.38, respectively, all P < 0.05). Combined glucose and fat loading additively reduced FMD in hypertensive patients.
    Zhonghua xin xue guan bing za zhi [Chinese journal of cardiovascular diseases] 12/2010; 38(12):1085-8.
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    ABSTRACT: Monocyte/macrophage differentiation is an essential process during atherosclerosis development. The retinoid X receptor (RXR) is a member of the nuclear hormone receptor superfamily, which plays an important regulatory role in many metabolic disorders, including atherosclerosis. The purpose of this study was to investigate the effect of RXR agonist on monocyte/macrophage differentiation in vitro. The THP-1 cell line was differentiated into a macrophage-like phenotype by incubation with phorbol-12-myristate-13-acetate (PMA) in the presence or absence of RXR agonist. The viability of adherent differentiated THP-1 cells was determined by MTT assay. Macrophage surface marker CD11b and CD36 was analyzed by flow cytometry. Phagocytosis was measured by fluorescence-labeled latex beads. The production of Cytokine Tunlornecrosisfactor-alpha (TNF-alpha), Interlaken-12p70 (IL-12p70), and Matrix metalloproteinase-9 (MMP-9), each of which was analyzed by ELISA. In the presence of the RXR agonists 9-cis retinoic acid or SR11237, PMA-induced THP-1 cells became less adherent, showed decreased macrophage-like morphological changes, decreased cell surface antigen CD11b and CD36 expression, and down regulated the phagocytosis of latex beads and the production of TNF-alpha and MMP-9. These data suggest that RXR agonists inhibit PMA-induced THP-1 cell differentiation into macrophage-like cells, which may be helpful in understanding the anti-atherosclerotic effect of RXR and its agonists.
    Molecular and Cellular Biochemistry 09/2009; 335(1-2):283-9. DOI:10.1007/s11010-009-0278-z · 2.39 Impact Factor
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    ABSTRACT: Dendtritic cells (DCs) are potent antigen-presenting cells and have an important role in the pathogenesis of atherosclerosis. Recent data suggests oxidized low-density lipoprotein (oxLDL) promotes the transition of a differentiating monocyte to a mature dendritic cell. In this study, we examined whether oxLDL could induce the differentiation of mature macrophages into DCs. After 48 h treatment with oxLDL, RAW264.7 cells increased in cell size and exhibited dendritic morphology. At the optimal oxLDL dose (10 microg/ml), approximately 74% of RAW264.7 cells differentiated into dendritic-like cells. Flow cytometric analysis detected dendritic cell surface markers (CD83, CD40, CD86, MHC Class II, and CD1d), and their expression increased in a dose- and time-dependent manner. Moreover, oxLDL-treated RAW264.7 cells showed functional changes including reduced endocytic activity, increased allostimulatory activity, and IL-12 production. The findings of the present work demonstrate that RAW264.7 cells, incubated with oxLDL, acquire some dendritic cell features.
    Atherosclerosis 02/2008; 199(2):257-64. DOI:10.1016/j.atherosclerosis.2007.12.002 · 3.99 Impact Factor