| Background Perioperative hyperglycemia is a serious perioperative complication which could contribute to higher morbidity and mortality.Many factors such as preoperative underlying diseases,surgery procedure and perioperative drug administration are involved in the occurrence of perioperative hyperglycemia.However,an increasing number of both fundamental and clinical researches discovered that anaesthetics participate into the initiation of perioperative hyperglycemia.Inhalation anesthetics isoflurane and sevoflurane could lead to glucose utilization disorder,impaired glucose tolerance,insulin secretion decreasing and insulin resistance.Hypothalamus which sits right above the brain stem and regulates a variety of functions,including sleep,body temperature,thirst,hunger as well as energy metabolism,while Adenosine Monophosphate Activated Protein Kinase(AMPK)plays an important in hypothalamus' function of energy metabolism.Nonetheless,there are few study of what the role of hypothalamus in inhalation anesthetics and blood glucose metabolism.Metformin is one of the most common hypolycemic agent with satisfactory hypoglycemic effect and security.This research will study the effect of isoflurane on the blood glucose of health mice and whether metformin could prevent perioperative hyperglycemia.What's more,the AMPK mRNA level in hypothalamus was also tested.Methods The mice used in this study is male C57BL/6 mice at 8 weeks,which would be anesthetized by isoflurane.Blood glucose would be tested by blooding at caudal vein.Metformin was dissolved in normal saline(NS)and administrated intraperitoneally 1 hour before anesthesia.Blood glucose would be tested 0.5 hours before anesthesia and 0.5,1,2,3,4,6 hours after anesthesia initiation as well as after 2 and 4 hours after the end of anesthesia.This study mainly include three parts:In the first parts of the study,mice were randomly divided into the non-fasted group and 12 h-fasted group,and each group was randomly divided into two subgroups,which are non-fasted control group(group Cn),non-fasted anesthesia group(group An),fasted control group(group Cf)and fasted anesthesia group(group Af).Mice in group An and group Af would be anesthetized by isoflurane at a concentration of 1.2%or 1.8%.Blood glucose of mice in each group would be tested at corresponding timepoint.In the second parts of the study,the isoflurane concentration caused obviously blood glucose increasing would be selected for following study.Mice were randomly divided into the non-fasted group and 12 h-fasted group,and each group was randomly divided into four subgroups,which are non-fasted control group(group Cn),non-fasted anesthesia group(group An),non-fasted metformin group(group Mn),non-fasted metformin plus anesthesia group(group MAn),fasted control group(group Cf),fasted anesthesia group(group Af),fasted metformin group(group Mf)and fasted metformin plus anesthesia group(group MAf).Mice in rroup Mn,group Mf,group MAn and group MAf underwent metformin administration 1 hour before anesthesia at dose of 20 mg/kg or 40 mg/kg and then mice in group An,group Af,group MAn and group MAf underwent isoflurane anesthesia.The blood glucose would be test by blooding at caudal vein at corresponding timepoint.In the third parts of the study,the metformin dose prevented blood glucose from increasing would be selected for following study.The parallel treatment groups would be set for hypothalamus harvest,and the AMPK mRNA level in hypothalamus would be tested by Q-PCR.Results In the first.part of the study,we find that the fundamental blood glucose of mice in each subgroup are at the same level,but the fundamental blood glucose in non-fasted group(8.3±1.0 mmol/L)is higher than 12 h-fasted group(6.5±0.7 mmol/L),P<0.05.What's more,comparing to group Cn,1.2%isoflurane contributes to blood glucose in group An rising from 0.5-4 hour after anesthesia initiation(P<0.05),while 1.8%isoflurane just lifts the BG in group An at 0.5 and 2 hour after the anesthesia beginning(P<0.05).In addition,comparing to group Cf,1.2%isoflurane contributes to blood glucose in group Af rising at 0.5,3 and 4 hour after anesthesia initiation(P<0.05),while 1.8%isoflurane-e causes not BG increasing in group Af but BG decreasing at 4 and 6 hour after anesthesia beginning(P<0.05).In the second part of the study,we chose 1.2%isoflurane concentration for following study due to its obviously BG increasing effect.The BG influenced by 1.2%isoflurane is similar as that in the first part,and without isoflurane metformin at 20 mg/kg and 40 mg/kg both cause no obvious effect on BG(P>0.05).Isoflurane anesthesia raise the BG of group An at 0.5,1 and 2 hour after anesthesia initiation and the BG of group Af at 1,2 and 3 hour after anesthesia initiation(P<0.05),then decrease occurred.After anesthesia,BG in group An decrease until 3 hour after anesthesia ending(P<0.05),while BG in group Af decrease until 4 hour after anesthesia ending(P<0.05).When anesthetized by 1.2%isoflurane,20 mg/kg metformin failed to prevent BG from increasing.Comparing to group Cn,mice in group An showed lifted BG 3 h after anesthesia initiation(P<0.05),then decreased to control level(P>0.05),while mice in group MAn showed lifted BG 1-2 h after anesthesia initiation(P<0.05),then decreased to control level too(P>0.05).Comparing to group Cf,mice in group Af showed lifted BG 0.5-2 h after anesthesia initiation(P<0.05),and showed reduced BG at 2 h after anesthesia ending(P<0.05),then went back to control level 3 h after the ending(P>0.05).While mice in group MAf showed lifted BG 0.5-1 h after anesthesia initiation(P<0.05),and showed reduced BG from anesthesia ending to 2 h after the ending(P<0.05),then went back to control leve 3 h after the ending(P>0.05).But at same condition,40 mg/kg reduced BG of group MAn from 2 h after anesthesia initiation to 4 h after anesthesia ending(P<0.05),and reduced BG of group MAf from 2 h after anesthesia initiation to 1 h after anesthesia ending(P<0.05).In the third part of the study,40 mg/kg metformin which successfully prevent BG from increasing after isoflurane anesthesia was chosen for following study.The level of hypothalamus AMPK mRNA:1 h:Compared with group Cf,the AMPK?1 and AMPKa2 mRNA level decreased in group MAf(P<0.05).4 h:Compared with group Cn and group Cf,the AMPKal mRNA level decreased in group An,group MAn and in group Af,while AMPKa2 mRNA level in group MAn decreased(P<0.05).6 h:Compared with group Cn and group Cf,AMPKal and AMPKa2 mRNA level decreased in group An,,group MAn and in group Af,group MAf(P<0.05).Conclusion Under long-term isoflurane anesthesia the blood glucose of mice increased at first and then decreased,while metformin combined with anesthesia induced persistent hypoglycemia,and this process has no obvious correlation with the the transcription activity of AMPK in the hypothalamus. |
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