BackgroundThe functional changes of the default mode network （DMN） are closely related to the onset of major depressive disorders. However， the relationship between the DMN subsystem （core subsystem， dorsomedial prefrontal cortex subsystem， medial temporal lobe subsystem） and symptoms of first-episode major depressive disorder remains unclear. ObjectiveTo investigate abnormal functional connectivity between DMN subsystems and the whole brain in first-episode major depressive disorder patients during the resting-state， and to analyse the correlations between these functional connectivity patterns and clinical symptoms， so as to reveal the potential neural mechanisms from the perspective of DMN subsystem. MethodsFrom September 2020 to September 2023， a total of 64 first-episode outpatients and inpatients meeting the diagnostic criteria for major depressive disorder in the Diagnostic and Statistical Manual of Mental Disorders， fourth edition （DSM-IV） were enrolled at the Inner Mongolia Autonomous Region Mental Health Center as the study group. During the same period， 54 healthy volunteers matched for age， gender， and years of education were recruited from the community as the control group. Both groups were assessed using the Hamilton Depression Scale-24 item （HAMD-24）. Resting-state functional magnetic resonance images （rs-fMRI） of the two groups were acquired using a Siemens 3.0 T scanner， and differences in functional connectivity between DMN subsystems （core subsystem， dorsomedial prefrontal cortex subsystem， medial temporal lobe subsystem） and the whole brain were compared. The functional connectivity values of brain regions with statistically significant differences between the two groups were extracted. Spearman's rank correlation coefficient analysis was used to investigate the correlation between these functional connectivity values and HAMD-24 scores of the study group. ResultsUltimately， 46 patients and 43 controls completed the study. Compared with the control group， the study group exhibited significantly stronger functional connectivity in the following pathways： between the right superior parietal lobule （core subsystem） and right cerebellar lobule VIII （t=3.954， P<0.05， GRF-corrected）， between the right lateral temporal cortex （dorsomedial prefrontal cortex subsystem） and right cerebellar lobule VIII， right and left hippocampi， right medial， and paracingulate gyrus （t=4.595， 4.208， 5.200， 4.038， P<0.05， GRF-corrected）， and between the temporoparietal junction （dorsomedial prefrontal cortex subsystem） and left lingual gyrus and right cerebellar lobule VIII （t=3.557， 4.274， P<0.05， GRF-corrected）. Conversely， weaker functional connectivity was observed between the right inferior frontal gyrus and left gyrus rectus （t=-3.824， P<0.05， GRF-corrected）. Furthermore， within the study group， the functional connectivity values between the right lateral temporal cortex and right hippocampus， as well as between the temporoparietal junction and right cerebellar lobule VIII， were both negatively correlated with the HAMD-24 cognitive impairment factor score （r=-0.306， -0.318， P<0.05）. ConclusionIncreased functional connectivity between the DMN （specifically its core and dorsomedial prefrontal cortex subsystems） and cerebellum， partial limbic system， and lingual gyrus may be associated with the neuropathology of first-episode major depressive disorder. Furthermore， alterations in functional connectivity between the dorsomedial prefrontal cortex subsystem and both the cerebellum and hippocampus in these patients may be related to cognitive function. ［Funded by 2019 Annual Inner Mongolia Autonomous Region Natural Science Foundation Project （number， 2019MS03038）； 2023 Annual Inner Mongolia Autonomous Region Natural Science Foundation Project （number， 2023MS08028）］

[ ABSTRACT] AIM:To observe the effect of high glucose on the protein expression of calreticulin ( CRT) and its association with cell apoptosis and mitochondrial dysfunction in the cardiomyocytes.METHODS: AC-16 cardiomyocytes were randomly divided into normal glucose group, high glucose group, high glucose+CRT siRNA group and isotonic con-trol group.The cell apoptotic rate, reactive oxygen species (ROS), mitochondrial membrane potential level, respiratory enzyme activity, and protein expression of CRT were observed.RESULTS: Compared with the cardiomyocytes in normal glucose group, the apoptotic rate and ROS production of cardiomyocytes increased in high glucose group, accompanying with the decreases in the mitochondrial membrane potential level and enzyme activitiy of the respiratory chain.The protein expression of CRT was significantly increased in high glucose group.However, compared with high glucose group, high glucose+CRT siRNA decreased the expression of CRT and attenuated the damage of mitochondria, but CRT siRNA did not reduce the ROS level in cardiomyocytes.CONCLUSION:High glucose brings about CRT over-expression to induce mito-chondrial injury, thus increasing myocardial apoptosis.

OBJECTIVETo observe the effect of angiotensin II (Ang II) on calreticulin (CRT) expression and its association with mitochondrial dysfunction in cardiomyocytes.

METHODSPrimary neonatal rat cardiomyocytes were randomly divided into CRT siRNA group, control siRNA group, control group, Ang II+ CRT siRNA group, Ang II+ control siRNA group and Ang II group. The cell surface area, protein synthesis rate, mitochondrial membrane potential level, enzyme activities, and CRT expression were observed.

RESULTSCompared with those in the control group, the cell surface area and protein synthesis rate were both increased and mitochondrial membrane potential level and enzyme activities decreased in Ang II groups. CRT expression was significantly down-regulated in Ang II+ CRT siRNA group with increased cell surface area, protein synthesis rate, mitochondrial membrane potential level and enzyme activities as compared with those in Ang II+ control siRNA group.

CONCLUSIONAng II up-regulates CRT expression to induce mitochondrial injury, which may be an important mechanism of myocardial hypertrophy.

Angiotensin II ; pharmacology ; Animals ; Calreticulin ; metabolism ; Cardiomegaly ; Cells, Cultured ; Membrane Potential, Mitochondrial ; Mitochondria ; pathology ; Myocytes, Cardiac ; pathology ; Protein Biosynthesis ; RNA, Small Interfering ; Rats