Glucose Oxidative Metabolism And Myosin Changes In Hypoxia-tolerant Hearts Of Gansu Zokor

Eospalax cansus lives in underground caves all their lives and is a typical subterranean rodents,widely distributed in northwest China.The oxygen concentration in the tunnel where underground rats live can be as low as 6%,and it changes dynamically with the seasons.The long-term underground life of Eospalax cansus has allowed them to evolve many adaptive characteristics,which are different from ground mice in morphology and physiological metabolism.In a long-term hypoxic living environment,the balance of metabolic demand and energy supply is the key to survive.Energy generation mainly depends on oxidative phosphorylation,which requires a large amount of oxygen to maintain the process,and Eospalax cansus live in a hypoxic environment,which poses a serious challenge to its survival.However,the Eospalax cansus survived in this harsh environment,indicating that it has a strong tolerance to hypoxia.This study selects the left ventricular tissue of the heart,analyzes the energy metabolism process of Eospalax cansus myocardial tissue from multiple perspectives,explores the adaptive changes of the heart,and enriches the hypoxia tolerance physiology of underground rats,which can provide ideas for the study of myocardial diseases induced by insufficient oxygen supply.The experiment was divided into 3 groups,each group had 4 Eospalax cansus and 4 SD rats,treated with 21%,10.5 and 6.5%oxygen concentration,respectively,to study the changes of cardiac energy metabolism under different oxygen concentration conditions.Protein fluorescence staining was used to detect changes in MHC and ssTnI proteins,which are important components of myofibrils in the left ventricle.The content of ATP and CrP was measured,and the energy state of the heart under hypoxia was observed.Real-time PCR was used to semi-quantify the mRNA levels of glucoseoxidative metabolism-related genes(PDK4,ME1,and PC),and Western blot technology was used to semi-quantitate the related proteins(PDK4,PDH,and ME1).PK and ME1 were measured by spectrophotometer.The main results obtained from this study as follow:1.The contents of ? and ?-MHC in the left ventricle,we found that the expression of?-MHC protein in Eospalax cansus was significantly higher than that of ?-MHC protein,which was about three times of ?-MHC protein.It was obviously different from SD rats,where ?-MHC protein was highly expressed.Because ?-MHC has lower ATPase activity,a higher percentage of ?-MHC consumes less ATP,which is beneficial to Eospalax cansus adaptation to hypoxic environment.Western blot results of ssTnI protein found no evidence of its expression in the left ventricle of the heart.2.The contents of ATP and CrP in the left ventricle:Eospalax cansus heart decreased significantly during hypoxia treatment,but the decrease was small.SD rats experienced a very large decline,especially at a 6.5%oxygen concentration.This shows that the energy system of Eospalax cansus is not affected greatly during hypoxia.3.The results of PK enzyme activity:Under hypoxic conditions,PK enzyme activity in the left ventricle of the heart of Eospalax cansus and SD rats decreased,but did not decrease further at 6.5%oxygen concentration,indicating that the glycolytic level only had slightly affected by hypoxia There was a slight decrease.The PK enzyme activity in the three groups of Eospalax cansus was less than that of SD rats,indicating that the glycolysis in the heart of Eospalax cansus was weaker than that of SD rats.4.Quantified the mRNA levels of glucose oxidation-related genes in Eospalax cansus,and found that PDK4 expression was significantly increased at 6.5%oxygen concentration.Although PDK4 expression was also increased in SD rats,it was far less than that in Eospalax cansus.It is implied that PDK4 responds to changes in oxygen concentration,and there is a shift in transcription levels at very low oxygen concentrations.The mRNA expression levels of ME1 and PC both showed a downward trend at 6.5%oxygen concentration,and the specific changes required further analysis at the protein levels.5.The protein levels of glucose oxidation-related genes:the expression of PDK4 protein of Eospalax cansus increased significantly at 6.5%oxygen concentration,which was consistent with the mRNA results.The PDK4 expression in SD rats was lower than that in Eospalax cansus,and the difference was significant at 6.5%oxygen concentration.The results show that PDK4 up-regulates mRNA expression,which in turn increases PDK4 protein expression.PDK4 phosphorylates PDH,resulting in an increased degree of PDH phosphorylation.Western blot results of PDH phosphorylation confirmed this.ME1 participates in anaplerosis,bypassing the glucose oxidation process.It was found that the expression of ME1 protein was up-regulated at 6.5%hypoxia.At the same time,the results of ME1 enzyme activity support this.Upregulation of ME1 further weakens glucose oxidation levels.In summary,a high percentage of ?-MHC in Eospalax cansus heart saves energy expenditure,and up-regulates PDK4 expression during hypoxia,which phosphorylated PDH to inhibit glucose oxidation and glucose consumption.The expression of ME1 is upregulated,which further reduces the oxidative phosphorylation of glucose and maintains the stability of TCA intermediates through the anaplerosis.This method of Eospalax cansus heart to cope with hypoxia stress can maintain stable heart function.