The Rotes Of Obestatin In Water Metabolic Abnormalities Of Kidney In Chronic Heart Failure And Their Mechanisms

The sodium and water retention is an important physiopathologic change in subjectswith Chronic heart failure(CHF).Heart and kidney work together to maintain the fluidbalance of our body,there are strong correlation and close interactions between heart andkidney diseases. Very often, physicians confront with patients who have concomitant heartand kidney failure. Relative cardiac output decrease and arterial underfilling in CHF areimportant signals that trigger heart failure related sodium and water retention.Neurohormonal systems such as the renin angiotensin aldosterone system(RAAS), thevasopressin axis activated in the course of heart failure also promote renal sodium andwater retention.The sodium and water retention that observed in heart failure isexaggerated by any decrease in glomerular filtration rate. Once this process has beenstarted, a vicious circle was set up between the heart and kidney, the patients' conditiongradually deteriorated, we often called it "cardio renal syndrome (CRS)". As the end stageof heart failure,the water and sodium retention in CRS will be a prominent conflict.Arginine vasopressin (AVP), considered as one of the important factors to regulatebody fluid volume, strengthens the fluid retention through the kidneys collection duct cellsaquaporin2by short term and long term regulations. However, excessive secretion ofAVP aggravates sodium and water retention by aquaporin2O has adverse effects on CHFand CRS progression by fluid retention and increases the preload and afterload of the heart,is involved in ventricular remodeling and causes hyponatremia associated with poorprognosis in CHF and CRS.Obestatin is a23amino acid peptide hormone.Recent findings suggested that it maybe related to water metabolism.Obestatin is produced in the stomach and a range of othertissues throughout the body. Obestatin is derived from the same gene product as ghrelin, ithas effects simmilar or opposite to those of ghrelin. Studies found that the ghrelin canalleviate the clinical syptoms of heart failure and improve their hymodynamatic indexes.Studies reported that obestatin may act in brain to inhibit water drinking. Obestatininhibited dehydration induced vasopressin secretion, it may be an important contributor tothe physiologic regulation of fluid and electrolyte homeostasis. Our study found that obestatin express in the kidney.All of the above indicated that obestatin may regulate fluidand electrolyte homeostasis by autocrine or paracrine. Obestatin assciated with AVP mayhave a role in the regulation of fluid and electrolyte homeostasis.The perpose of the study is to investigate plasma obestatin and AVP levels inCHF,chronic kidney diseases (CKD) and CRS patients,their relation in CHF,CKD andCRS process and whether obestatin level is associated with AVP, to study the changesof Cardiac function and urine volume,the changes of Aquaporin2and AVP expressionafter obestatin administration. to study the roles of obestatin in short term and long termregulatory mechanism on aquaporin2in collecting duct cells.Therefore we are intent toinvestgate the roles, mechanisms of obestatin in water metabolic abnormalities of kidney inChronic Heart Failure.Part Changes of plasma levels of AVP and obestatin in CHF paientswith CKD and their significanceObjective: To investigate plasma obestatin and AVP levels in patients with CRS,CHF and CKD, and their relationship with the progress of CRS, CHF and CKD andwhether obestatin level is associated with AVP.Methods: Total plasma AVP and obestatin levels were measured by Elisa in34patients with cardiorenal syndrome (CRS),31patients with chronic kidney disease(CKD),41patients with chronic heart failure (CHF) and30healthy subjects. Bodymass index, brain natriuretic peptide, New York Heart Association functional classand other parameters were tested. Statistical methods were used to calculate thecorrelation between obestatin and AVP level.Results: Obestatin levels were significantly higher in patients with CRS(355.8±14.6pg/ml)than those in healthy controls (212.3±37.8pg/ml, P<0.01) and patientswith CKD (246.7±6.2pg/ml, P<0.01) and patients with CHF (258.4±17.5pg/ml, P<0.01);obestatin levels were significantly higher in patients with CHF than those in healthycontrols(258.4±17.5pg/ml vs212.3±6.9pg/ml, P<0.05); obestatin levels were significantlyhigher in patients with CKD than those in healthy controls (246.7±6.2pg/ml vs212.3±6.9pg/ml, P<0.01) there was no significant difference between patients with CHFand patients with CKD Vasopressin (AVP) levels were significantly higher in patientswith CRS (65.1±6.6pg/ml) than those in healthy controls (38.5±3.7pg/ml, P<0.01)andpatients with CKD (50.4±4.5pg/ml, P<0.01) and patients with CHF (54.6±2.5pg/ml, P<0.01)O AVP levels were significantly higher in patients with CHF than those in healthycontrolsO54.6±2.5pg/ml vs38.5±3.7pg/ml, P<0.01)O AVP levels were significantlyhigher in patients with CKD than those in healthy controls O50.4±4.5pg/ml vs38.5±3.7pg/ml, P<0.05)O there was no significant difference between patients with chronicheart failure and patients with chronic kidney diseaseO vPlasma obestatin levels werepositively correlated with AVP levels in the populations studied (r=0.219, P <0.05)Oplasma obestatin levels were positively correlated with BNP levels in the populationsstudied (r=0.220, P <0.05); plasma obestatin levels were positively correlated withcreatinine levels in the populations studied (r=0.176, P <0.05).Conclusion: Both Circulating AVP and obestatin level increased in CRS,CHF andCKD patients; plasma obestatin levels were positively correlated with AVPO BNP andcreatinine levels in the populations studied.Part II Influence of obestatin on cardiac function and watermetabolic of CHF ratsObjective: To investigate the effect of obestatin on the changes of cardiac functionand urine volume,and its regulatory effects on the expression of AQP2and AVP inplasma and kidney collecting duct in post infarction CHF rats.Methods:30rat models of myocardial infarction were set up by ligating leftanterior descending arteryO LADO whereas sham group rats undergo chest operationwithout LAD ligation. The sham group (n=6) and the heart failure group (n=30) weregiven normal diet. The sham group was given saline100l/kg/d (n=6), the heart failuregroup (n=30) was divided into5subgroups. These five subgroups were given saline100l/kg/d (n=6) O AVP2g/kg/d (n=6) O ghrelin100g/kg/d (n=6) O obestatin50g/kg/d(n=6) O obestatin100g/kg/d(n=6), respectively. After4weeks ofintraperitoneal injection, left ventricular ejection fraction (LVEF) was measured byechocardiography, urine was collected to measure urine volume, urine AQP2, plasmaAVP and AQP2were measured by elisa, kidney collecting duct AVP and AQP2expression were measured by western blot in all sham and CHF rats.Results:1.Compared with the level before the treatment, after4weeks treatment/Obestatin100(g/kg/d) treatment group demonstrated a significant increase in leftventricular ejection fraction (LVEF)O57.9±6.9vs53.7±6.5O P<0.05O;a significantincreased urine volumeO19.3±1.7ml vs18.3±1.1mlOP<0.05O; a decreased expression of urine AQP2O0.966±0.056pg/ml vs1.046±0.049pg/mlOP<0.01O; an increased expressionof plama obestatin level (155.77±6.22pg/ml vs138.06±10.37pg/ml,P<0.01); while nosignificant change of the plasma AVP level;<AVP treatment group demonstrated asignificant decrease in LVEFO57.0±2.7%vs59.9±2.8%O P<0.01O; a significantdecreased urine volumeO17.7±0.3ml vs18.7±0.9mlOP<0.05O; a significant increasedexpression of urine AQP2O1.285±0.079pg/ml vs1.171±0.055pg/mlOP<0.05O; asignificant increased expression of urine AQP2O3.688±0.308pg/ml vs3.074±0.264pg/mlO P<0.01O Oa significant increased expression of obestatinO152.49±8.44pg/mlvs141.94±7.85pg/mlO P<0.01O O Ghrelin treatment group demonstrated a significantincrease in LVEFO57.9±6.9%vs53.7±6.5%O P<0.01O and no significant changes ofurine volume,urine AQP2and the levels of plasma obestatin and AVP; I There were nosignificant changes of LVEF,urine volume,urine AQP2, the level of plasma obestatin andAVP in the sham group given saline,the heart failure group given salin and the heartfailure group given obestatin (50g/kg/d) demonstrated.2./Compared with the thesham group given salineOAVP treatment group demonstrated a significant increase in thelevels of kidney AQP2and AVP expression; obestatin(100g/kg/d) treatment groupdemonstrated a significant decrease in the level of kidney collecting duct AQP2expression; while no significant changes were observed in the heart failure rats givensalineO ghrelin and obestatin(50g/kg/d) groups;<Compared with the heart failure givensaline groupO AVP treatment group had a significant increase in the levels of kidneycollecting duct AQP2and AVP expression; obestatin(100g/kg/d) treatment groupdemonstrated a significant increase in the level of kidney collecting duct AQP2expression; while no significant changes were observed in the heart failure rats givenghrelin and obestatin(50g/kg/d).Conclusions: High dose obestatin intraperitoneal injection can improve cardiacfunction and urine volumeO can decrease expression of urine volume, AQP2andexpression of AQP2in kidney collecting ductObut has no effect on the expression of AVPin plasma and kidney collecting duct.Part III Effect of obestatin on aquaporin2in collecting duct cellsof kidneyObjective: To investigate weather regulatory effects of obestatin on aquaporin2ininner medullary collecting duct3(IMCD3) cells is carried out via AVP route. Methods: After IMCD3cells had been cultivated with different concentrations ofobestatin (108,107mol/L) and AVP(108,107mol/L) for15minutes,30minutes,1hours,6hours,24hours, the cells were collected for detecting AVP and AQP2expressions bywestern blot. The expression of cAMP was also tested in IMCD3cells by elisa.Results:1. x Compared with the level before the cultivation, expressions ofcAMP, AVP and AQP2were not significantly changed in IMCD3cells cultivated with thelower concentrations of obestatin (108mol/L) for15minutes,30minutes,1hours,6hours and24hours;<Compared with the level before the cultivation, the expressions ofcAMP and AVP were not significantly changedO and AQP2was significantly decreased(P<0.05) in IMCD3cells cultivated with the high concentrations of obestatin (107mol/L)for6hours and24hours.2. x Compared with the level before the cultivation, theexpressions of cAMP and AQP2were not significantly changed in IMCD3cellscultivated with the lower concentration of AVP (108mol/L) for15minutes,30minutes,1hours,6hours and24hours;<Compared with the level before the cultivation, theexpression of cAMP was significantly increased in IMCD3cells cultivated with the highconcentration of AVP (107mol/L) for30minutes,1hour,6hours and24hours, but not inthe cells cultivated for15minutes. The expression of AQP2was significantly increasedonly in IMCD3cells cultivated with the high concentrations of AVP (107mol/L) for6hours and24hours.Conclusions: The obestatin intervention can not affect AVP and cAMPexpression in IMCD3cells, but can reduce AQP2expression. The result indicated that theobestatin may take part in water regulation of the kidney via long term regulatorymechanism of the AQP2,and not by the AVP route.