Sözmen B, Delen Y, Girgin F K, Sözmen E Y
Department of Internal Medicine, Atatürk State Hospital, Izmir, Turkey.
Clin Biochem. 1999 Aug;32(6):423-7. doi: 10.1016/s0009-9120(99)00034-x.
Type 2 diabetes mellitus (DM) is well recognized as being associated with increased prevalence of hypertension. Experimental and epidemiologic studies have shown that oxygen-free radicals are elevated because antioxidant enzyme activities are altered both in uncontrolled essential hypertension and DM itself. Recently paraoxonase (PON) has been recognized as an antioxidant enzyme that hydrolyzes lipid peroxides. The aim of this study is to evaluate simultaneously PON activities and antioxidant status in hypertensive type 2 DM cases and to establish any possible relationship between these parameters and duration of hypertension or diabetes, hemoglobin (Hb) A1c levels, and lipid parameters.
Nineteen normotensive subjects with type 2 DM, 37 hypertensive (diastolic blood pressure 90 mm Hg or more) subjects with type 2 DM, and 25 normotensive control subjects with normal glucose tolerance were selected for this study. Superoxide dismutase (SOD), catalase, and basal-stimulated PON activities were measured by the methods of Sun et al.; Goth; and Eckerson, Wyte, and La Du, respectively; other lipid parameters were determined using an autoanalyzer.
Catalase activities of either hypertensive patients with type 2 DM or type 2 DM patients without complication were found to be higher than controls (p<0.01), although no significant difference in SOD and basal-stimulated PON activities was observed between these groups. A significant elevation in catalase activity (p = 0.004) of patients with high HbA1c levels (>7.0%) (n = 37) compared with patients with low HbA1c levels (<7.0%) (n = 19) was detected. There was also a positive correlation between the catalase activities and fasting glucose levels and HbA1c concentrations in hypertensive patients with type 2 DM (r = 0.4567, p<0.05 and r = 0.3686, p<0.05, respectively). An increase in catalase activity of patients with B and/or AB phenotype compared with patients with A phenotype was also noted.
Poor glycemic control in diabetes is strongly associated with an increase in free radicals and consequent diabetic complications. Uncontrolled glucose metabolism may also be the cause of alterations in antioxidant enzymes. Among these, catalase correlates best with poor glycemic control. The current data reveal that B allele carriers of PON are more susceptible to oxidant stress.
2型糖尿病（DM）与高血压患病率增加密切相关，这一点已得到广泛认可。实验和流行病学研究表明，在未控制的原发性高血压以及DM本身中，由于抗氧化酶活性发生改变，导致氧自由基水平升高。最近，对氧磷酶（PON）被认为是一种可水解脂质过氧化物的抗氧化酶。本研究旨在同时评估2型DM高血压患者的PON活性和抗氧化状态，并确定这些参数与高血压或糖尿病病程、糖化血红蛋白（Hb）A1c水平以及血脂参数之间是否存在任何可能的关系。
本研究选取了19名2型DM血压正常的受试者、37名2型DM高血压患者（舒张压90mmHg或更高）以及25名糖耐量正常的血压正常对照受试者。超氧化物歧化酶（SOD）、过氧化氢酶以及基础刺激下的PON活性分别采用Sun等人、Goth以及Eckerson、Wyte和La Du的方法进行测定；其他血脂参数则使用自动分析仪进行测定。
尽管在这些组之间未观察到SOD和基础刺激下的PON活性存在显著差异，但发现2型DM高血压患者或无并发症的2型DM患者的过氧化氢酶活性均高于对照组（p<0.01）。与糖化血红蛋白水平低（<7.0%）（n = 19）的患者相比，糖化血红蛋白水平高（>7.0%）（n = 37）的患者的过氧化氢酶活性显著升高（p = 0.004）。在2型DM高血压患者中，过氧化氢酶活性与空腹血糖水平以及糖化血红蛋白浓度之间也存在正相关（分别为r = 0.4567，p<0.05和r = 0.3686，p<0.05）。还注意到与A型表型患者相比，B和/或AB型表型患者的过氧化氢酶活性增加。
糖尿病患者血糖控制不佳与自由基增加以及随之而来的糖尿病并发症密切相关。未控制的糖代谢也可能是抗氧化酶改变的原因。其中，过氧化氢酶与血糖控制不佳的相关性最佳。目前的数据表明，PON的B等位基因携带者更容易受到氧化应激的影响。
