The Relationship Between Plasma DPP4 Activity To BDNF Ratio And Depression In People With Type 2 Diabetes Mellitus

Objective: At present,depression has become one of the most important risk factors leading to lifetime suicide attempt,and its pathogenesis needs further study.In people with Type 2 Diabetes Mellitus(T2DM),the pathogenesis of depression is associated with increased activity of Dipeptidyl peptidase-4(DPP4)and decreased expression of Brain-Derived Neurotrophic Factor(BDNF).Therefore,this study aimed to investigate the relationship between plasma DPP4 study,BDNF and DPP4/BDNF ratio(DBR)and moderate to severe depressive symptoms in type 2 diabetes mellitus.The increase of DPP4 activity and the decrease of BDNF in the peripheral circulation might be involved in the pathophysiology of depression.Methods: A total of 1535 patients with type 2 diabetes aged 41 to 81 years were screened.The personal data of type 2 diabetes patients were collected by questionnaire survey.All subjects underwent physical examination in the Guilin Medical University Affiliated Hospital.The suivey collected personal data including drinking history,leisure time activity,education level,smoking history,previous history,ets.The interleukin 6(IL-6),nitro cheese glycine,C-reactive protein(CRP),8-iso-PGF2 a,DPP4 activity,BDNF level are the corresponding index of blood tests.The Patient Health Questionnaire(PHQ-9)was developed according to the DSM-IV American Diagnostic Criteria for Depression.A cross-sectional study was conducted on the data.All data were analyzed using SPSS 16.0 statistical software(SPSS,Chicago,IL).Analysis of covariance,partial correlation analysis,chi-square test,T test,mediating effect analysis,multiple logistic regression analysis and other statistical methods are included in the main statistical methods.Results: The DPP4 activity is negatively correlated with BDNF level(P<0.001).Oxidative stress partially mediated the negative correlation between DPP4 activity and BDNF level.The levels of nitrotyrosine,8-iso-PGF2 a,interleukin-6,C-reactive protein and PHQ-9 score were significantly increased with the increase of DBR.Patients with the highest DPP4 activity and DBR quartile and the lowest BDNF quartile had higher incidence of moderate and major depressive symptoms than those with the lowest DPP4 activity and DBR quartile and the highest BDNF quartile(P<0.05).As DPP4 activity increased and BDNF levels decreased,the risk of developing moderate to severe depressive symptoms.increased.Conclusions: This study shows that DPP4 activity is inversely correlated with BDNF in both depressed and non-depressed patients with type 2 diabetes,and that oxidative stress,rather than inflammation,may be a mediator in this negative correlation.DBR was positively correlated with moderate and severe depressive symptoms,which could be used as a new biological indicator of depressive symptoms in patients with type 2 diabetes.