The Relationship Between Gamma-Glutamyl Transpeptidase And Components Of Metabolic Syndrome

Background&Objectives:With the development of social economy, people’s lifestyle has changed. The prevalence of metabolic syndrome which is characterized by obesity and multiple metabolic abnormalities is rising year by year on a global scale. It has become a serious worldwide public health problem threating to human health. A large number of studies at home and abroad show that metabolic syndrome can obviously increase the risk of type2diabetes, cardiovascular disease and some cancers.Despite the current academia has not yet been fully unified definition and diagnostic criteria of the metabolic syndrome, but all the existing definitions include four components:obesity, increased blood pressure, a high blood sugar level, and dyslipidemia(high triglycerides, low HDL cholesterol). As the research moves along, some new components have been successively put forward, such as chronic inflammatory state, thrombosis, oxidative stress status and hyperuricemia, etc. So far, the pathogenesis of the metabolic syndrome has not been fully elucidated. It is generally believed that the metabolic syndrome is an endocrine metabolic disease with obesity and insulin resistance as the core, and moreover genetic and environmental factors are also involved in this process.Oxidative stress is a negative effect produced by free radicals in the body, and is considered to be an important factor leading to aging and disease. It is found that oxidative stress and diseases such as diabetes, atherosclerosis are closely related. Since the oxidative stress have been proposed as a metabolic syndrome component, researches increase gradually which study its role on the pathogenesis of the metabolic syndrome. However, there is still a lack of large population-based epidemiological studies. Recent studies have found that gamma-glutamyl transpeptidase can be used as a sensitive marker of oxidative stress. In this study, according to the available research results about pathophysiology, we constructed a structural equation model to study the relationship between oxidative stress (gamma-glutamyl transpeptidase as markers) and four components of metabolic syndrome. Large sample groups of physical examination data has been collected in the Shengli oilfield central hospital in Dongying to validate this model, which can provide clues to further study on the pathogenesis of metabolic syndrome.Materials&Methods:In this paper, we choose the people who had a medical examination from September2011to September2012in Shengli oilfield central hospital in Dongying as the research object, with the exclusion of people suffering from liver disease, gallbladder disease, familial hyperlipidemia, Type1diabetes. People who drink excessively, or has no complete physical examination data of physical examination were also been excluded. Those who have controlled hypertension, diabetes, dyslipidemia or obesity within normal limits using drugs were also been excluded. Medical information includes gender, age, past medical history, family history, drinking history, body weight, height, blood pressure, fasting blood glucose, triglycerides, high-density lipoprotein cholesterol and gamma glutamyl transpeptidase, etc. All data are analyzed with the application of the SPSS16.0statistical software. Measurement data which conforms to normal distribution was expressed in mean±standard deviation (x±s) and was tested by t test and variance analysis; Measurement data which don’t conform to the normal distribution was expressed in median (lower quartile, upper quartile)[M](QL, QU) and was tested by the rank sum test. Enumeration data was tested by chi-square test. Categorical variables are expressed in frequency (%). Partial correlation analysis was used to study the relationship between gamma-glutamyl transpeptidase and the four components of metabolic syndrome. Mplus7.0software was used to conduct structural equation model analysis. The difference was considered statistically significant when P＜0.05. Results:We have collected12520people (male8277, female4243) which had complete medical data to carry out the cross-sectional study.1. The objects of study have been divided into groups according to whether he had some component of metabolic syndrome respectively. Comparing gamma-glutamyl transpeptidase level between two groups, we have found that the differences were statistically significant (P＜0.001) not only in men but in women. As the superposition of metabolic syndrome components, even if gamma-glutamyl transpeptidase is within the normal range, it has a trend of progressive increase.2. The objects of study have been divided into groups according to the quartile of gamma-glutamyl transpeptidase level. Differences among four groups were statistically significant (P＜0.001) except high density lipoprotein cholesterol in women. With the rising of gamma-glutamyl transpeptidase level, components of metabolic syndrome showed a trend of increase (the level of high density lipoprotein cholesterol in men was falling). Grouping according to the normal range of gamma-glutamyl transpeptidase, we found that the differences between gamma-glutamyl transpeptidase normal group and gamma-glutamyl transpeptidase abnormal group were both statistically significant (P＜0.001) in the level and prevalence rate of metabolic syndrome.3. Partial correlative analyses were conducted to control age. We found that body mass index, fasting blood glucose, systolic blood pressure, diastolic blood pressure, triglyceride and gamma-glutamyl transpeptidase were positively correlated in men. The correlation coefficients were0.217,0.152,0.225,0.173and0.309respectively(P<0.001). High density lipoprotein cholesterol and gamma-glutamyl transpeptidase was negatively correlated in men. The correlation coefficient was-0.029(P=0.009＜0.05).It has also been found that body mass index, fasting blood glucose, systolic blood pressure, diastolic blood pressure, triglyceride and gamma-glutamyl transpeptidase were positively correlated in women. The correlation coefficients were0.200,0.180,0.175,0.195and0.312respectively(P＜0.001). No significant correlation was found between high density lipoprotein cholesterol and gamma-glutamyl transpeptidase.4. The structural equation model was structured according to the existing theory and was matched by collected data. The objects of study have been divided into three group based on age (before the menopause, menopause, after the menopause) both in men and in women. Each group was conducted model fitting and the final model was obtained according to the modified index and professional knowledge. Meanwhile, effect decomposition was conducted in the path having the mediation effect.Conclusions:1. People who have any component of metabolic syndrome have a higher gamma-glutamyl transpeptidase level than those not having that component. As the superposition of metabolic syndrome components, even if gamma-glutamyl transpeptidase is within the normal range, it has a trend of progressive increase.2. Gamma-glutamyl transpeptidase and components of metabolic syndrome are related:fasting blood glucose, body mass index, systolic blood pressure, diastolic blood pressure, triglyceride and gamma-glutamyl transpeptidase were positively correlated in the whole population, while high density lipoprotein cholesterol and gamma-glutamyl transpeptidase were negatively correlated in men with a very small correlation coefficient. No significant correlation was found between high density lipoprotein cholesterol and gamma-glutamyl transpeptidase in women.3. The role of oxidative stress in the pathogenesis of metabolic syndrome was influenced by gender and age. Changes in hormone level after menopause and menopause may affect the role of oxidative stress in the pathogenesis of metabolic syndrome.