Study The Effects Of High Altitude Environment On Metformin Pharmacokinetics And Pharmacodynamics In T2DM Rats

Type 2 diabetes mellitus（T2DM）is a high-incidence chronic disease characterized by insulin resistance and impaired isletβ-cell function.The treatment of T2DM is mainly through drug intervention,and the common drugs include biguanides,sulfonylureas,glinides,thiazolidinediones andα-glucosidase inhibitors.Among them,metformin is the first-line drug for the treatment of type 2 diabetes mellitus recommended by authoritative guidelines at home and abroad.Previous studies by our research group have found that plateau environment affects the biotransformation process of drugs in the body,and then affects the efficacy of drugs.However,the effect of high altitude environment on the pharmacokinetics and pharmacodynamics of metformin in T2DM rats has not been reported.In this study,T2DM rats were used as the research objects to explore the effects of high altitude environment on the pharmacokinetic parameters and pharmacodynamics of metformin in T2DM rats.In this study,the T2DM rat model was established by feeding with high-sugar and high-fat diet combined with intraperitoneal injection of streptozotocin（STZ）.Firstly,the effect of high altitude environment on the pharmacokinetics of metformin in T2DM rats was studied.The T2DM rats were randomly divided into the plain group and the high altitude group.Blood samples were collected from the ophthalmic venous plexus,and the plasma drug concentration was measured by LC-MS/MS.Western Blot was used to detect the expression of OCT2 and MATE1 protein in renal tissue of the two groups,and biochemical analyzer was used to determine the serum creatinine and urea concentrations to investigate the effect of high altitude environment on the expression of proteins mediating metformin transport in renal tissue and renal function.Secondly,the effect of plateau environment on the pharmacodynamics of metformin was explored.The rats in the plain group and the plateau group were given the same dose of metformin by gavage for 7 consecutive days,once a day.Fasting blood glucose（FBG）,insulin resistance index（HOMA-IR）,glucagon-like peptide-1（GLP-1）,malondialdehyde（MDA）,superoxide dismutase（SOD）,reduced glutathione（GSH）in liver and kidney tissues,and interleukin-6（IL-6）,interleukin-1β（IL-1β）in liver tissues were detected The concentrations of metformin in liver tissue,glycogen content in liver muscle,pyruvate（PA）and lactate（LA）content and lactate dehydrogenase（LDH）activity in serum were measured.Finally,in order to improve the hypoglycemic effect of metformin in high altitude environment,we used the anti-hypoxia drug betelnut polyphenols combined with metformin to investigate the effect of high altitude environment on the pharmacodynamics of metformin when the body’s anti-hypoxia ability was improved,and measured the related pharmacodynamic indexes.The results were as follows:（1）Compared with the plain group,the AUC and t_1/2z of metformin in the high altitude group significantly increased by 22.82%and21.56%,and Cl_z/F decreased by 19.38%;The expression levels of OCT2 and MATE1,which mediate metformin transport,were decreased in the renal tissue of rats,and the serum urea and creatinine concentrations were increased.It is suggested that the clearance of metformin in the body is slowed down at high altitude,which may be caused by the down-regulation of proteins that mediate metformin transport and the reduction of renal function.After multiple administration,compared with the plain group,the AUC,MRT,and T_max of metformin in the high altitude group significantly increased by 46.23%,44.93%,and 29.46%,respectively,and Cl_z/Fdecreased by32.91%.（2）After metformin treatment for 7 days,the body weight,GLP-1 and muscle liver glycogen content were increased（P<0.05）,and fasting blood glucose and HOMA-IR were decreased（P<0.05）in the plain group.There was no significant difference in body weight,fasting blood glucose and GLP-1 levels,but HOMA-IR was increased and muscle liver glycogen content was decreased in the high altitude group（P<0.01）.Compared with the plain group,the MDA content in liver and kidney tissues of the high altitude group increased（P<0.05）,SOD activity and GSH content decreased,the contents of inflammatory factors IL-6,IL-1β,MCP-1 and TNF-αin liver tissues increased significantly（P<0.05）,and the concentration of metformin in liver tissues decreased（P<0.05）.The contents of PA and LA and the activity of LDH in serum were increased（P<0.05）,suggesting that the hypoglycemic effect of metformin was inhibited under high altitude environment,which may be related to oxidative stress induced by high altitude environment.（3）At high altitude,compared with the metformin alone group,the body weight,GLP-1 concentration and muscle liver glycogen content were increased（P<0.05）,and fasting blood glucose and HOMA-IR were decreased（P<0.05）in the betelnut-polyphenol combined with metformin group.The content of MDA in liver and kidney tissues was significantly decreased（P<0.05）,while the activity of SOD and GSH content were increased.The contents of inflammatory factors IL-6,IL-1β,MCP-1 and TNF-αin liver tissues were significantly decreased（P<0.05）,and the concentration of metformin in liver tissues was increased（P<0.01）.The levels of PA and LA and the activity of LDH in serum were decreased（P<0.05）,indicating that combined administration of metformin can improve the anti-hypoxia ability of the body and improve the hypoglycemic effect of metformin at high altitude.Conclusions:The absorption of metformin are increased and the excretion of metformin is slowed down in T2DM rats at high altitude,which may be responsible for the down-regulation of the expression of OCT2 and MATE1 proteins that mediate metformin transport and the reduction of renal function.The hypoglycemic effect of the same dose of metformin in T2DM rats at high altitude is weaker than that in the plain group,which may be caused by the increase of oxidative stress and inflammatory damage in the body,which reduces the concentration of metformin in liver tissue,aggravates liver glycogenolysis,and increases the production of PA and LA,the raw materials of gluconeogenesis.Betelnut polyphenols combined with metformin in high altitude environment can improve the anti-hypoxia ability of the body and improve the hypoglycemic effect of metformin.