Relationship Between Serum Leptin Level And RAAS, Insulin Sensitivity In Patients With Obesity-related Hypertension

The incidence rate of obesity and hypertension appears obvious up-trend in our country. Hypertension, obesity, hyperinsulinemia and dyslipidemia have common heredity background, and often occur concomitantly, are called " metabolic syndrome" . Current, the pathogenesis of essential hypertension is still notfully elucidated, and obesity is one of leading risk factors for it. Leptin, the product of ob gene and predominantly produced by adipose tissue, is a hormone that regulates body weight, food intake and energy expenditure. In recent years, medical investigators attach great importance to the role of leptin in essential hypertension. The importance of the renin-angiotensin-aldosterone system ( RAAS) in the regulation of either sodium and water excretion or blood pressure is well known. The present study is undertaken to determine serum leptin level in patients with obesity-related hypertension, hypertension, obesity and controls, aim at clarify the relationship between RAAS, insulin sensitivity and serum leptin level, as well as understand the pathophysiologic mechanism of leptin for the development of hypertension and obesity.SUBJECTS AND METHORDSSubjects We studied 38 patients with obesity-related hypertension, 32 patients with hypertension, 33 patients with obesity and 33 controls. All groups matched mutually for sex, age and FPG.Measurements All subjects normally ate food three days before drawing blood. 5-milliliter blood samples were taken after an overnight fast in supine position. At the same time, the height and weight were measured for each subject, then body mass index (BMI) was calculated as BMI = weight (kg)/height (m)2. Leptin, FINS, PRA, AngII and ALD were measured with radio-immunoassay. FPG was determined with routine clinical laboratory test. Insulin sensitivity index (ISI) was calculated as simple formula ( ISI = ln [ 1/ ( FPGmmol/1 x FINSuIU/ml) ] ) raising by Li Guangwei et al.Statistical analysis All data were expressed as the mean + SD. ONE-WAY ANOVA was used to compare differences. Simple and multiple step-wise regression analysis were used to evaluate the correlation between variables. All statistical tests were two-tailed and a p value <0.05 was regarded as statistically significant.RESULTS1. ISI in patients with obesity-related hypertension, hypertension or obesity was significantly lower than that in control.2. Serum leptin level in patients with obesity-related hypertension or obesity was significandy higher than that in controls. Serum leptin level in patients with obesity-related hypertension was significandy higher than that in patients with obesity. Leptin concentration in female subjects was significandy higher than that in male subjects in all four groups.3. There was not significandy difference between groups for PRA, AngII or ALD respectively.4. In a multiple linear step-wise regression analysis, widi serum leptin level as dependent variable and other correlated variables as independent variables, we found that the gender, BMI, SBP, ISI and PRA were main determinants for serum leptin level.5. There was significandy negative correlation between serum leptin level and ISI in all four groups.6. Simple correlation analysis showed that there was significandy positive correlation between serum leptin level and PRA, ALD in patients with obesity-related hypertension, significandy positive correlation between serum leptin level and Ang II in patients with hypertension and significandy positive correlation between serum leptin level and ALD in patients with obesity.7. There was not significantly correlation between ISI and PRA, Ang II or ALD in all four groups.8. Patients with obesity-related hypertension and patients with hypertension were combined into one group, in order to be divided into other two groups according to PRA. We found serum leptin level of group B was significantly higher than that of group A.DISCUSSIONObesity usually associated with cardiovascular diseases such as hypertension, Diabetes and art...