Yuk-Ling Dai

The University of Hong Kong, Hong Kong, Hong Kong

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Publications (5)13.35 Total impact

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    ABSTRACT: Background: Exercise training improves endothelial function in patients with coronary artery disease (CAD) through unclear mechanisms. We hypothesized that mitochondrial dysfunction related to a lower habitual physical activity level (PAL) is associated with endothelial dysfunction. Methods and results: We assessed habitual PAL by a validated International Physical Activity Questionnaire, brachial flow-mediated dilation (FMD) and serum lactate, pyruvate, fasting glucose and lipid profiles in 105 CAD patients (age 68±10; 87% men). As defined by the lactate/pyruvate ratio (LP ratio) ≥75(th) percentile of the age-and sex-matched controls (ie, ≥18), mitochondrial dysfunction was observed in 33/105 (31%) patients. With decreasing PAL tertiles, there were significant linear trends of lower FMD (P=0.004) and higher LP ratio (P=0.009). Multivariate logistic regression found that the lowest compared with the highest PAL tertile (adjusted odds ratio=3.78, P=0.02) had more patients with high LP ratio. After adjustment for cardiovascular risk factors and medications, the lowest compared to the highest PAL tertile had significantly lower FMD (absolute decrease 1.25%, P=0.03); and high LP ratio was associated with impaired FMD (absolute reduction 1.09%, P=0.03). Conclusions: In CAD patients, a lower level of habitual PAL is associated with impaired FMD and increased prevalence of mitochondrial dysfunction as defined by high LP ratio. Moreover, high LP ratio predicts a lower FMD, suggesting that the occurrence of mitochondrial dysfunction with lower habitual PAL is associated with endothelial dysfunction in CAD patients.
    No preview · Article · Jul 2012 · Circulation Journal
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    ABSTRACT: We aim to investigate the effect of exercise training on endothelial function and exercise capacity in patients with coronary artery disease. A randomized, controlled trial was conducted to determine the effects of an 8-week exercise training programme (n = 32) vs. controls (n = 32) on brachial flow-mediated dilation (FMD) in patients with stable CAD. After 8 weeks, patients received exercise training had significant improvements in FMD (1.84%, p = 0.002) and exercise capacity (2.04 metabolic equivalents, p < 0.001) compared with controls. The change in FMD correlated inversely with baseline FMD (r = -0.41, p = 0.001) and positively with the increase in exercise capacity (r = 0.35, p = 0.005). After adjusting for confounders, every 1 metabolic equivalent increase in exercise capacity was associated with 0.55% increase in FMD. Furthermore, patients received exercise training had significantly increased high-density lipoprotein cholesterol and decreased diastolic blood pressure and resting heart rate compared with controls. However, exercise training did not alter high-sensitivity C-reactive protein, oxidative stress measured as superoxide dismutase and 8-isoprostane, and CD34/KDR + endothelial progenitor cell count. Subgroup analysis showed that FMD was significantly improved only in CAD patients with baseline low exercise capacity (<median value of 7.65 metabolic equivalents, p = 0.004) but not in those with normal exercise capacity. Exercise training improved FMD and exercise capacity in stable CAD patients independent of the changes in inflammation, oxidative stress, or endothelial progenitor cells. The beneficial effects of exercise training on FMD and exercise capacity are inter-related, and more pronounced in those with baseline impaired exercise capacity.
    No preview · Article · Jul 2011
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    ABSTRACT: Coronary artery disease (CAD) is associated with endothelial dysfunction and mitochondrial dysfunction (MD). The aim of this study was to investigate whether co-enzyme Q10 (CoQ) supplementation, which is an obligatory coenzyme in the mitochondrial respiratory transport chain, can reverse MD and improve endothelial function in patients with ischaemic left ventricular systolic dysfunction (LVSD). We performed a randomized, double-blind, placebo-controlled trial to determine the effects of CoQ supplement (300 mg/day, n=28) vs. placebo (controls, n=28) for 8 weeks on brachial flow-mediated dilation (FMD) in patients with ischaemic LVSD(left ventricular ejection fraction <45%). Mitochondrial function was determined by plasma lactate/pyruvate ratio (LP ratio). After 8 weeks, CoQ-treated patients had significant increases in plasma CoQ concentration (treatment effect 2.20 μg/mL, P<0.001) and FMD (treatment effect 1.51%, P=0.03); and decrease in LP ratio (treatment effect -2.46, P=0.03) compared with controls. However, CoQ treatment did not alter nitroglycerin-mediated dilation, blood pressure, blood levels of fasting glucose, haemoglobin A1c, lipid profile, high-sensitivity C-reactive protein and oxidative stress as determined by serum superoxide dismutase and 8-isoprostane (all P>0.05). Furthermore, the reduction in LP ratio significantly correlated with improvement in FMD (r=-0.29, P=0.047). In patients with ischaemic LVSD, 8 weeks supplement of CoQ improved mitochondrial function and FMD; and the improvement of FMD correlated with the change in mitochondrial function, suggesting that CoQ improved endothelial function via reversal of mitochondrial dysfunction in patients with ischaemic LVSD.
    No preview · Article · Feb 2011 · Atherosclerosis
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    ABSTRACT: Despite the use of statin therapy, a significant proportion of patients with coronary artery disease (CAD) still develop cardiovascular events. We hypothesized that development of mitochondrial dysfunction (MD) after statin therapy might be linked to endothelial dysfunction and thus limiting its beneficial effects. We studied the effect of MD on endothelial function in 119 patients with CAD on long-term statins (>1 year). Brachial artery flow-mediated dilation (FMD) was assessed by high-resolution ultrasonography and blood levels of lactate, pyruvate, fasting glucose, and lipids were measured. MD (defined by a lactate/pyruvate ratio >75th percentile of the age- and sex-matched normal controls, i.e., > or = 18) was observed in 43/119(36%) patients. There were no significant differences in age, gender, and clinical characteristics between patients with or without MD (all P > 0.05). Patients with MD received higher dose of statin (23.5 +/- 19.3 vs. 17.1 +/- 10.5 mg simvastatin-equivalent dose, P = 0.05) and had lower FMD (2.69 +/- 2.94 vs. 4.33 +/- 2.80%, P = 0.003) than those without MD. Multivariate analysis showed that statin dosage was independently associated with MD (OR:1.03, P = 0.03), and MD significantly predicted an absolute 1.36% decrease in FMD (P = 0.01). In conclusion, a significant proportion of patients with CAD on statin developed MD, which was associated with high-dose statin and with impaired FMD, suggesting that increased statin dosage may induce MD and contribute to endothelial dysfunction in patients with CAD.
    No preview · Article · Apr 2010 · Cardiovascular toxicology
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    ABSTRACT: Exercise training reduces mortality in patients with coronary artery disease (CAD); however, the impact of habitual physical activity level (PAL) on vascular endothelial function and circulating endothelial progenitor cells (EPCs) remain unknown. We assessed habitual PAL using a validated International Physical Activity Questionnaire in 116 patients (67.8+/-9.5 years; 81% male) with stable CAD and preserved left ventricular ejection fraction > or =45%. The number of circulating CD34/KDR+ and CD133/KDR+ EPCs was determined by flow cytometry, and brachial artery flow-mediated dilation (FMD) was measured. The mean PAL of CAD patients with 1644 MET min/week (where MET is metabolic equivalents). With higher habitual PAL tertiles, there were significant linear trends of increased FMD (P = 0.001) and CD133/KDR+ EPCs (P = 0.03), but not of CD34/KDR+ EPCs. Patients with the highest tertile of PAL were associated with an absolute increase of 1.89% in FMD (relative increase 68%, P = 0.003) and 0.12% in CD133/KDR+ EPCs (relative increase 44%, P = 0.01) compared with those in the lowest tertile of PAL, after adjusting for age, sex, presence of hypertension, diabetes mellitus, hypercholesterolemia, smoking, and the use of medications including statins. However, neither CD34/KDR+ nor CD133/KDR+ EPCs significantly correlated with FMD. This study showed that higher habitual PAL in patients with CAD was associated with higher FMD and EPC count. Nonetheless, FMD only significantly correlated with increased PAL, but not EPC, suggesting that increased physical activity improves endothelial function through mechanisms other than increasing EPC count.
    No preview · Article · Aug 2009 · European journal of cardiovascular prevention and rehabilitation: official journal of the European Society of Cardiology, Working Groups on Epidemiology & Prevention and Cardiac Rehabilitation and Exercise Physiology