| Objective: Recent studies in both humans and experimental animals have led to renewed interest in uric acid and its association with vascular function. The uric acid,as an anti-oxidant have the effect of anti-oxidative stress, it's a protective factor. But much more studies show that the ascension of the blood uric acid has an adverse effect on vascular function, it relates to many vascular diseases'process of generation and development. Myeloperoxidase(MPO) is a peroxydase which is excreted by activated heterophil granulocyte when the blood vessel is impaired. After the impairment of blood vessel by some factors, the heterophil granulocytes are activated, and they can excret more MPO into blood. MPO could amplify the effect of oxidative stress, so contributes to the impairment of blood vessel and atherosclerosis. It is one of the indexes of oxidative stress and the impairment of vascular endothelial. Endothelin(ET) is a 21polypeptide which is excreted and released by vascular endothelial cell. It has been confirmed that ET play an important role in ischemia, hypoxia, ischemical reperfusion injury and many other pathologic process that vascular endothelial cell is injured. The stable express of ET which is dependent on endothelial cell is very important to maintain the basic tension. It has been found that ET's level or activity is increased in the diseases which are correlated to functional disorder of endothelial cell, as hypertension, heart failure and artherosclerosis. The functional disturbance of vascular endothelial cell is an early appearance of artherosclerosis. Measuring the carotid intima-media thickness (IMT) by vascular ultrasound is a clinical method that we usually used to detect the degree of atherosclerosis . So far, we put much more attention to the relationship between high level of the blood uric acid and arteriosclerosis, but there are little researches on the relationship between low or normal level of uric acid and vascular endothelial function, as well as the carotid intima-media thickness. This study will make a cross-sectional research on the high risk group of atherosclerosis—metabolic syndrome patients .After correcting risk factors that may affect vascular function, we will detect the level of myeloperoxidase,endothelin and the carotid intima-media thickness in different levels of blood uric acid and study the effect that different levels of blood uric acid make on vascular endothelial function and artherosclerosis.Methods: According to the 2005 IDF criteria for the diagnosis of metabolic syndrome, chosed 90 patients without hematological system disease, hepatic and kidney disease, gout, cancer and thyroid diseases and so on.The blood pressure, body mass index, smoking history and family history of all subjects were collected . Mensurate blood glucose, blood fat, hepatic and renal function and myeloperoxidase with venous blood drawed on an empty stomach. Measure the myeloperoxidase(MPO) by colorimetric method, Measure the endothelin(ET) by radioimmunity method,Measure the carotid intima-media thickness(IMT) by doppler ultrasound. According to the different levels of uric acid ,the subjects were divided into three groups : 30 subjects in each group .Group A ( group low blood uric acid): uric acid<176μmol/l. Including 16 men and 14 women with the age range from 46 to 75(63.80±10.25); Group B(group normal blood uric acid): male 176~416μmol/L and female 176~360μmol/L. Including 17 men and 13 women with the age range from 44 to 79(61.47±12.23); Group C(group high blood uric acid): male>416μmol/l and female>360μmol/L . Including 17 men and 13 women with the age range from 42 to 74(58.90±12.27).Results: After adjustment for possible influencing factors, the results of the comparison of MPO,ET and IMT among the three groups are as follows:①From group A to group C ,the blood MPO has a tendency to increasing gradually . MPO in group C is the highest(101.93±10.25μg/L), in sequence from high to low , MPO of the other two groups in orders is the group B(91.38±15.32μg/L)and group A(42.73±10.25μg/L), MPO in group C and group B are both significantly higher than it in group A (p<0.05), and there is also significant difference between group B and group C(p>0.05).②From group A to group C , ET has a tendency to increasing gradually .ET in group C is the highest(143.95±57.90Pg/ml), in sequence from high to low , ET of the other two groups in orders is the group B(84.90±16.87Pg/ml)and group A(80.31±29.55Pg/ml), ET in group C is significantly higher than it in group A and group B(p<0.05), but there are no significant difference between group A and B(p>0.05).③From group A to group C ,the IMT has a tendency to increasing gradually .The carotid intima-media thickness in group C is the highest(1.07±0.30m/s), in sequence from high to low , IMT of the other three groups in orders is the group B(0.88±0.40m/s)and group A(0.81±0.23 m/s), IMT in group C is significantly higher than it in group A and group B(p<0.01), but there are no significant difference between group A and B(p>0.05).④The incidence rate of carotid artery artherosclerosis in group C is the highest 63.3%(19/30),in sequence are group B 30.0%(9/30)and group A 20.0%(6/30) . After chi square test, we can see the three groups have a significantly different(p<0.05).⑤By doing Pearson correlation analysis to analyze the correlation of uric acid to MPO,ET and IMT, we can see that uric acid both has positive correlation to all of MPO,ET and IMT, their coefficient of correlation are 0.787,0.301 and 0.541 respectively. And MPO also has a positive correlation to IMT, the coefficient is 0.241. Both of them have statistical significance (p<0.05).⑥To analyze the influence factors of MPO in metabolic syndrome patients by stepwise regression, make MPO to be the dependent variable and age,body mass index,fasting plasma glucose and so on which can also affect on MPO to be the independent variable. It is suggested that uric acid is an independent influence factor to the augmentation of MPO in metabolic syndrome patients(p<0.05).⑦Make ET to be the dependent variable and age,body mass index,fasting plasma glucose and so on which can also affect on IMT to be the independent variable. It is suggested that the independent influence factors to the augmentation of ET in metabolic syndrome patients conclude uric acid and HDL-C(p<0.05).⑧Make IMT to be the dependent variable and age,body mass index,fasting plasma glucose and so on which can also affect on IMT to be the independent variable. It is suggested that the independent influence factors to the augmentation of IMT in metabolic syndrome patients conclude uric acid and HDL-C(p<0.05).Conclusion: (1) To the metabolic syndrome patients,from the low level of the blood uric acid to the high level of the blood uric acid, the level of the blood MPO and the blood ET has a tendency to inceasing gradually. And the level of blood uric acid is an independent influence factor of the blood MPO and the blood ET. It is suggested that to the metabolic syndrome patients , the ascension of the blood uric acid is the risk factor to the impairment of vascular function. (2) To the metabolic syndrome patients , from the low level of the blood uric acid to the high level of the blood uric acid, the level of IMT has a tendency to inceasing gradually, and the number of carotid artery sclerosis is also higher. The level of blood uric acid is an independent influence factor of IMT. It is suggested that to the metabolic syndrome patients, the ascension of the blood uric acid is the risk factor of atherosclerosis.
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