The Study Of Ghrelin And Obestatin System In Patients With Essential Hypetrension

Background and purposeBased on the current medical development and exam method, can find theexact causes leading to hypertension, which is called secondary hypertension,otherwise known as essential hypertension (EH). EH account for90percent of thehypertension patients. The prevalence of EH has been rising at an alarming speed.Pathogenic mechanisms for EH have not been completely explained yet. A Japanesescientist named Kojima found a28-amino-acid polypeptide from the endocrine cellof stomach in human and rats. This polypeptide was named ghrelin. Ghrelin is astimulant of appetite and promote gastric emptying, peristalsis, digestion andabsorption. These could lead to weight gain. Obestatin is expressed by homologousgene. It is another23-amino-acid polypeptide released from stomach. The biologicalactivity of obestatin appears to be the opposite of that of ghrelin. Obestatin increasesatiety and inhibit gastric emptying, peristalsis, food digestion and absorption. Theseresult in weight loss. Studies show that plasma ghrelin and obestatin decreaseobviously in obese. So the two hormones may have a crucial effect on weightregulation. Ghrelin have some degree of anti-inflammatory actions and a protectiveeffect on endothelial function. Peripheral blood ghrelin decreases in hypertensivepatients and this may be an important factor leading to elevated blood pressure.Obestatin also has anti-inflammatory actions, indicating an important function inregulation of blood pressure. Researches about the ghrelin gene Leu72Metpolymorphism and obesity, insulin resistance, hyperlipidemia, diabete mellitus andcoronary heart disease suggested that mutations in this gene could be protectiveagainst cardiovascular disease and related risk factors. So far, there’s few report onthe susceptibility relations of the ghrelin gene polymorphism and EH. Our study wasto measure the fasting plasma ghrelin and obestatin concentrations in normotensive obese patients and EH patients with obesity, and to observe their relationship withclassical cardiovascular risk factors, including blood pressure, obesity indexinsulin resistance and blood glucose. The study also observed the Leu72Met singlenucleotide polymorphism (SNP) of ghrelin gene and the relationship with EH andrelated classical risk factors. The aim is to further clarify if this gene mutation is aprotective factor for EH.MethodsThe experiment was divided into two parts.68hypertensive obese patients,60normotensive obese patients and65healthy controls were included in the first study.All subjects were measured for height, weight, waist circumference (WC),waist-to-hip ratio (HC), blood pressure (SBP, DBP) and had body mass index (BMI)and waist to hip ratio (WHR) calculated. The fasting glucose concentrations weredetermined by glucose hexokinase enzymatic assay and the levels of fasting plasmaobestatin and ghrelin were measured using an enzyme-linked immunoadsorbentassay (ELISA) method. The fasting insulin (FINS) was determined usingelectrochemiluminescence assay (ECLIA). The fasting ghrelin/obestatin ratio andthe homeostasis model assessment-IR (HOMA-IR) were calculated. The serum lipidincluding total cholesterol (TC), triglycerides (TG), low density lipoproteincholesterol (LDL-C) and high density lipoprotein cholesterol (HDL-C) weremeasured by automatic biochemical analyzer. Polymerase ChainReaction-Restriction Fragment Length Polymorphism (PCR-RFLP) is used to detectthe Leu72Met SNP of ghrelin gene in210EH patients and220healthy controls insecond experiment. The plasma ghrelin was detected using ELISA method collectedfrom all subjects. The general clinical indexes including BMI, SBP, DBP, FINS, FPG,HOMA-IR, TC, TG, LDL-C and HDL-C were collected. Data management andstatistical analysis was performed using the statistical software SPSS15.0. Themeasurement data were expressed as mean±SD. The normal distribution andhomogeneity of variances test were conducted. Difference between groups wasdetermined using Student’s t-test for continuous data (or rank sum test in non- normal distribution data). Moreover, Pearson′linear correlation analysis was used toestimate the correlation between two variable measures. The difference betweencount data was determined using Pearson x2test. Hardy-Weinberg equilibrium testwas performed. The multivariable non-conditional logistic regression model wasused for the multivariate analysis and the interaction analysis.Results1. Hypertensive obese patients had lower plasma ghrelin and obestatincompared with normotensive obese patients and controls (P＜0.05). Normotensiveobese patients had lower plasma ghrelin and obestatin compared with controls (P＜0.05).2. Hypertensive obese patients had higher ghrelin/obestatin ratio than controls(P＜0.05). There was no significant difference between hypertensive obese patientsand normotensive obese patients. The ghrelin/obestatin ratio in normotensive obesepatients was higher than controls (P＜0.05).3. In hypertensive obese group, the plasma ghrelin and obestatin werenegatively associated with BMI, SBP, DBP, and the HOMA-IR (P＜0.05). Fasting ghrelin and obestatin concentrations were significantly andpositively correlated (P＜0.05).4. In normotensive obese group, ghrelin, obestatin and ghrelin/obestatin ratiowere all negatively associated with BMI and the HOMA-IR (P＜0.05).5. No significant association was observed between plasma ghrelin, obestatin orghrelin/obestatin ratio and TC, TG, LDL-C, HDL-C, WC, HC, WHR, FPG, FINS inthree groups.6. There’re three types of polymorphism of ghrelin gene at the base siteLeu72Met. There is a big difference in the genotypes (CC, CA, AA) and alleles (C,A) between the EH patients and the controls (P＜0.05).7. In EH group, the plasma ghrelin level in subjects who are homozygous CCwithout mutant is not only significantly lower than those who are heterozygous CAbut also lower than those who are nucleotide homozygous mutant AA (P＜0.05). The patients with CC genotype have higher SBP and lower HDL-C (P＜0.05). Thepatients with A allete have lower plasma ghrelin, HDL-C and higher SBP, DBP, andLDL-C (P＜0.05).8. The multivariable logistic regression showed that BMI, HOMA-IR, LDL-Cand HDL-C were risk factors of EH. The interation analysis indicated that there wasa negative plus interation between Leu72Met SNP and LDL-C (P＜0.05).Conclusions1. The peripheral blood ghrelin, obestatin and ghrelin/obestatin ratio wassignificantly correlated with EH, obesity and IR.2. No correlation was observed between ghrelin/obestatin system and bloodlipid or blood glucose.3. The Leu72Met SNP of ghrelin gene is significantly related to thesusceptibility of EH. Base mutation C to A reduced the incidence of EH.4. The Leu72Met polymorphism of ghrelin gene is related to the plasma ghrelin,blood pressure and blood lipid metabolism. Base mutation C to A elevated plasmaghrelin, and lower blood pressure and blood lipid.5. Obesity, IR, hyperglycemia and disorder of lipid metabolism were riskfactors of EH.6. There was an antagonism between Leu72Met SNP and LDL-C ondeveloping EH.7. No association was found between Leu72Met polymorphism of ghrelin geneand obesity or hyperglycemia.