The Effect Of Glucose Abnormality On Brain Injury And Related Mechanisms

BACKGROUDClinical studies confirm that there is a close correlation between abnormal blood glucose(including hypoglycemia,hyperglycemia,and glycemic fluctuations)and brain damage.Glucose is the brain's main source of energy,the increasing,decreasing or fluctuations of its level will influence the function of nerve,resulting in different degrees of brain damage.The acute severe hypoglycemia can directly lead to brain damage.Hyperglycemia and glucose fluctuation will aggravate ischemic brain injury.Meanwhile,hyperglycemia and glucose fluctuation are clinically recognized as a risk factor for ischemic stroke.The following will explain the three kinds of abnormal blood glucose and brain damage related:1.Hypoglycemia is a common complication of intensive hypoglycemic regimen in diabetic patients,most likely to lead to brain damage.The concept of "glucose reperfusion brain injury" put people's cognition on the pathogenesis of hypoglycemic brain injury and reflect on the traditional treatment of hypoglycemia.Hypoglycemic brain edema is the first step in the development of hypoglycemic brain injury.Studying the pathological mechanism of hypoglycemic brain edema may provide new targets and strategis for clinical treatment of hypoglycemic brain injury.2.Hyperglycemia is an independent risk factor for ischemic brain injury.The data show that 15%-30% of patients with ischemic brain damage have diabetes.Patients with hyperglycemia have higher rates of post-stroke mortality,worse neurological recovery,more complications,and greater risk of recurrence than patients with normal glucose.Therefore,exploring the molecular mechanism of hyperglycemia aggravating ischemic brain injury provides a new theoretical basis for the clinical treatment of ischemic brain injury associated with diabetes.3.Glycemic fluctuations,not only present in patients with diabetes,but also be found in individuals with normal glucose metabolism.In emergency states such as ischemic stroke,patients without diabetes mellitus previously may still have abnormally elevated blood glucose levels.When hypoglycemic therapy was given at this time,and blood glucose levels may plummet,leading to acute glycemic fluctuations.Previous studies suggest that certain concentrations of hyperglycemia may have a protective effect on ischemic brain injury,however,in clinical practice found that after acute cerebral ischemia,the patient's blood glucose levels fluctuate greatly,can not objectively reflect the influence of changes in blood glucose on ischemic effects of brain damage.At the same time clinical studies have confirmed that acute fluctuations in blood glucose can aggravate ischemic brain injury.So far,there are few studies focus on the impact of acute blood glucose fluctuation on ischemic brain injury and the related mechanisms.Therefore,to explore and study the impact of acute blood glucose fluctuations on ischemic brain injury and the related mechanisms will provide a new theoretical basis for clinical treatment.OBJECTIVES1.To explore the molecular mechanism of hypoglycemic cerebral edema and to find new targets for clinical treatment;2.To study the mechanism of abnormal blood glucose in aggravating ischemic brain injury and try to provide new stratigies for the clinical treatment of ischemic stroke patients with abnormal glucose metabolism.METHODS1.AQP4 knockout mice were selected as the research object,the model of acute hypoglycemia was established by intraperitoneal injection of insulin.First,the effect of AQP4 knockdown on the blood-brain barrier was assessed by measuring water content of brain,evans blue(EB)infiltration,and the expression of Claudin.The expression of inflammatory cytokines in brain tissue was detected by real-time fluorescence quantitative polymerase chain reaction to prove that AQP4 is involved in the regulation of inflammatory response.Then a non-contact co-culture model of astrocytes and brain microvascular endothelial cells was established in vitro.AQP4 was silenced by siRNA interference on astrocytes to assess the influence of silencing astrocytes on the function of endothelial cells.The expression of inflammatory cytokines in co-culture system was detected by enzymelinked immunosorbent assay.The expression of PPAR-? in astrocytes was assessed by Western blotting.Finally,PPAR-? inhibitors were added to the co-culture system to investigate whether PPAR-? is involved in the protective effect of AQP4 knockout on hypoglycemic brain edema by retesting the expression of inflammatory cytokines in the co-culture system.2.Type 2 diabetic mice were chosed as the experimental animals,and the models were established by middle cerebral artery occlusion.Firstly,we examined the expression of neutrophils and NETs in the penumbra by immunofluorescence and evaluated the association between diabetes and NETs formation.Secondly,NETs inhibitor was injected intraperitoneally,and the correlation between NETs and ischemic brain damage in diabetic mice were evaluated by neurological function score,TTC staining and brain water content test.Finally,whether hyperglycemia aggravates ischemic brain injury through NETs-mediated inflammatory reaction was examined by detecting the expression of inflammatory cytokines in mice brain tissue.3.C57 / BL mice were selected as the research object,middle cerebral artery occlusion model was established by electrocoagulation and then simulate acute blood glucose fluctuation by intermittent injection of 50% glucose intraperitoneally.Firstly,the expression of neutrophils and NETs in the penumbra was detected by immunofluorescence to assess the correlation between blood glucose fluctuations and NETs formation.Secondly,Neisseria gonorrhoeae were then injected intraperitoneally.Neuro-function score,TTC staining and brain water content were used to evaluate whether acute blood glucose fluctuation aggravate ischemic brain injury by NETs.Finally,whether the acute blood glucose fluctuations aggravate ischemic brain injury through NETs-mediated inflammatory reaction was examined by detecting the expression of inflammatory cytokines in mouse brain tissue.RESULTS1.In the hypoglycemic models,AQP4 knockdown has protective effects on hypoglycemic brain injury.(1)In vivo experiments: AQP4 knockdown relieved hypoglycemic brain edema and alleviated the damage of bloodbrain barrier by hypoglycemia.Hypoglycemia up-regulated inflammatory cytokines while AQP4 knockdown inhibited the up-regulation of inflammatory cytokines by hypoglycemia.In the meantime,hypoglycemia inhibits PPAR-? activity,whereas AQP4 knockdown activates PPAR-? activity.(2)In vitro experiments: the release of inflammatory cytokines in primary cultured astrocytes under hypoglycemic conditions were decreased after silencing AQP4,at the meantime the expression of PPAR-? was increased.What's more,the down-regulation of tight junction proteins under hypoglycemic conditions was inhibited after the co-culture between astrocytes which silencing AQP4 with endothelial cells.2.In a diabetic ischemic brain injury model,hyperglycemia induces NETs and increases ischemic brain damage by upregulating the inflammatory response.(1)Hyperglycemia leads to an increase in the number of neutrophils after cerebral ischemia.(2)Hyperglycemia promotes the formation of NETs.(3)Inhibition of NETs production can relieve the neurological damage after cerebral ischemia,reduce the volume of cerebral infarction,and alleviate the cerebral edema.(4)The formation of NETs aggravates the inflammatory response.3.In acute blood glucose fluctuation models,acute fluctuations in blood glucose induce the production of NETs and aggravate ischemic brain injury by upregulating the inflammatory response.(1)Acute glycemic excursions increase the number of neutrophils after cerebral ischemia.(2)Acute glycemic excursions promote the formation of NETs.(3)Inhibiting the production of NETs can alleviate the neurological impairment after cerebral ischemia increased by glycemic excursions.(4)The formation of NETs aggravates the inflammatory response.CONCLUSION1.In acute cerebral edema,AQP4 knockdown can inhibit the inflammatory reaction by activating PPAR-?,reduce hypoglycemic brain edema and reduce the damage of blood-brain barrier by hypoglycemia.2.In diabetic ischemic brain injury,diabetes aggravated ischemic brain injury,affecting nerve function recovery.Diabetes-induced NETs aggravate ischemic brain damage by upregulating the inflammatory response.3.When cerebral ischemia complicated by glycemic excursions,ischemic brain injury will increase,affecting nerve function recovery.NETs participate in the process of ischemic brain injury which is aggravated by glycemic excursions by regulating the inflammatory.