Phospholipate Phosphatase Lipin1 Affects Diabetic Encephalopathy By Regulating The Homeostasis Of Mitochondria-Associated Endoplasmic Membranes(MAMs)

Background:Diabetic encephalopathy(DE)is a common central nervous system complication of diabetes mellitus,which is characterized by cognitive dysfunction and related behavioral defects,seriously affecting the quality of life of patients with diabetes mellitus.The prevalence of DE has increased with increasing life expectancy in patients with diabetes.However,the pathogenesis of DE is currently unclear,so there is a lack of effective clinical treatment measures.Exploring the key pathogenesis of DE and using this as an entry point to seek new strategies for clinical drug treatment is one of the key problems that need to be solved in DE research.Mitochondria and the endoplasmic reticulum are important organelles that regulate energy and material metabolism in neurons.They are linked by the mitochondrial associated ER membranes(MAMs).Current studies believe that MAMs homeostasis is an important mechanism of various neurodegenerative diseases,which can induce endoplasmic reticulum and mitochondrial dysfunction,and thus lead to neuron damage.However,the role and mechanism of MAMs homeostasis in the pathogenesis of DE are still unclear.MAMs are tight junctions composed of mitochondrial outer membrane,endoplasmic reticulum and a variety of functional proteins.The stability and integrity of lipid composition and structure are important for maintaining the homeostasis of MAMs.Phospholipid acid phosphatase Lipin1 is currently recognized as a key enzyme in regulating phospholipid metabolism.Altered expression and activity of Lipin1 can affect the function of membranous organelles by affecting phospholipid homeostasis in membrane structure.Although the absence of Lipin1 has been shown to induce significant endoplasmic reticulum stress,whether it can further disturb MAMs homeostasis and ultimately mediate DE remain unclear.Objective:1 To determine whether there is MAMs homeostasis imbalance and Lipin1 deficiency in DE.2 To determine whether Lipin1 deficiency can induce DE through endoplasmic reticulum stress,MAMs homeostasis imbalance and mitophagy.Methods:1 MAMs homeostasis and Lipin1 expression in the hippocampus of DE mice were evaluated.(1)Type 1 diabetes mellitus model was constructed by intraperitoneal injection of STZ,blood glucose and body weight were monitored.After 12 weeks,Morris water maze test was used to evaluate the cognitive function of mice.(2)The expression of BDNF and P-CREB was detected by western blotting.The density and morphology of dendritic spines were evaluated by Golgi staining.(3)The changes of MAMs in the hippocampus were observed by transmission electron microscopy,and the expression of Lipin1 in the hippocampus was detected by western blotting and immunofluorescence.(4)The changes of MAMs and Lipin1 in mouse neurons cultured with high glucose were evaluated by fluorescence staining and western blotting.2 The possible mechanism of Lipin1 regulating MAMs homeostasis and DE development was investigated.Adeno-associated virus that regulated lipinl expression was injected in the hippocampus of mice.Lentivirus infection was used to regulate Lipin1 expression in neuron cells in vitro.(1)Morris water maze,Western blotting and Golgi staining were used to evaluate the changes of cognitive function.(2)The effect of Lipin1 on MAMs was observed by electron microscopy and western blotting.(3)The effects of Lipin1 on endoplasmic reticulum stress and mitochondrial autophagy in the hippocampus and neurons were evaluated by western blotting.Results:(1)The type 1 diabetic mice showed significant cognitive decline at 12 weeks after STZ injection.(2)The expression of Lipin1 in the hippocampus of DE mice was significantly lower than that of control mice.(3)Interference with the expression of Lipin1 can lead to cognitive dysfunction in mice and disturb the homeostasis of MAMs.Meanwhile,the hippocampus of mice and cultured neurons in vitro showed obvious endoplasmic reticulum stress and mitophagy.(4)Upregulation of Lipin1 in hippocampal or neuronal cells can improve cognition and MAMs homeostasis in DE mice,and relieve endoplasmic reticulum stress and mitochondrial autophagy in hippocampal and neuronal cells.Conclusion:1 The imbalanced homeostasis of MAMs in hippocampus caused by Lipin1 deficiency is an important pathological change in diabetic encephalopathy.2 The mechanism of diabetic encephalopathy is related to endoplasmic reticulum stress and mitophagy induced by Lipin1 deletion in hippocampus.