Protective effects of Zuogui Jiangtang Jieyu Formula on hippocampal neurons in rats of diabetes complicated with depression via the TRP/KYN metabolic pathway

Objective To explore the protective effects and mechanism of Zuogui Jiangtang Jieyu Formula(左归降糖解郁方,ZGJTJYF)on hippocampal neurons in rats of diabetes complicated with depression(DD)via the TRP/KYN metabolic pathway.Methods(i)In vivo experiments:60 specified pathogen free(SPF)grade male Sprague-Dawley(SD)rats were randomly divided into six groups with 10 rats in each groups:control,DD model,positive(1.8 mg/kg fluoxetine+0.18 g/kg metformin),high-dose ZGJTJYF(ZGJTJYFH,40.500 g/kg ZGJTJYF),middle-dose ZGJTJYF(ZGJTJYF-M,20.250 g/kg ZGJTJYF),and lowdose ZGJTJYF(ZGJTJYF-L,10.125 g/kg ZGJTJYF)groups.Except for the control group,other groups were established DD model by high-fat emulsion intake with single tail vein streptozotocin(STZ)and four weeks of chronic unpredictable mild stress(CUMS).All drug administration groups were treated by gavage during CUMS modeling,and the control and model groups were given equal amount of distilled water.After four weeks,the serum levels of blood glucose and glycosylated hemoglobin were measured to determine the hypoglycemic effect of ZGJTJYF.Moreover,the open field test and Morris water maze test were performed to evaluate the antidepressant effect of ZGJTJYF.Changes in 5-hydroxytryptamine(5-HT)level were detected via high-performance liquid chromatography with electrochemical detection(HPLC-ECD);the levels of tryptophan(TRP),kynurenine(KYN),and indoleamine 2,3-dioxygenase(IDO)in the hippocampus were detected using enzyme-linked immunosorbent assay(ELISA);the protein expression levels of synaptophysin(SYN)and postsynaptic density material-95(PSD-95)were detected via immunohistochemistry(IHC);and the protein expression levels of N-methyl-D-aspartate receptor(NR)2 A and NR2 B were detected using Western blot.(ii)In vitro experiments:five SPF grade SD pregnant rats(E16–18)were used to obtain primary hippocampal neurons(Ne),six SD new-born rats were used to collected primary astrocytes(As)and microglia(MG),and to establish a Ne-As-MG co-culture system.All co-culture systems were divided into six groups:control(PBS),model[150 mmol/L glucose+200μmol/L corticosterone(G&P)+PBS],blank(G&P+blank serum),positive(G&P+positive drug-containing serum),ZGJTJYF(G&P+ZGJTJYF serum),and 1-methyl-D-tryptophan(1-MT,IDO inhibitor)(G&P+1-MT)groups.After 18 h of intervention by corresponding treatment,immunofluorescence was used to analyze the protein expression levels of SYN,PSD-95,NR2 A,and NR2 B;ELISA was performed to measure the levels of interleukin(IL)-1β,IL-6,tumor necrosis factor(TNF)-α,and TRP/KYN metabolic pathway-related factors[TRP,KYN,kynurenine acid(KYNA),quinolinic acid(QUIN)].Results(i)In vivo experimental results showed that ZGJTJYF-M and ZGJTJYF-L significantly improved the elevated blood glucose state of DD rats(P<0.01 and P<0.05,respectively);ZGJTJYF-H,ZGJTJYF-M,and ZGJTJYF-L increased their autonomous activity,learning,and memory ability(P<0.01,P<0.01,and P<0.05,respectively).Moreover,the levels of 5-HT and TRP were significantly increased(P<0.01),and the levels of KYN and IDO were significantly decreased in the hippocampus(P<0.01)of rats after ZGJTJYF-M treatment.The protein expression levels of SYN and PSD-95 were significantly upregulated in hippocampal neurons(P<0.01),while the abnormal activation of NR2A and NR2B was markedly inhibited in hippocampus(P<0.05)of rats after ZGJTJYF-M treatment.(ii)In vitro experimental results showed that ZGJTJYF-containing serum significantly increased the protein expression levels of SYN and PSD-95 in hippocampal neurons(P<0.01),decreased the levels of IL-1β(P<0.01),IL-6(P<0.05),TNF-α(P<0.01),IDO(P<0.05),KYN(P<0.05),and QUIN(P<0.01),and increased the levels of TRP and KYNA(P<0.01)in the simulated DD state.ZGJTJYF also had an significantly inhibitory effect on the abnormal activation of NR2A and NR2B in neurons(P<0.05)in a stimulated DD state.Conclusion ZGJTJYF can effectively improve 5-HT deficiency in the hippocampus of rats by inhibiting IDO expression and regulating the TRP/KYN metabolic pathway,and it has a favorable protective effect on hippocampal neuron injury caused by DD.Therefore,ZGJTJYF is an effective potential therapeutic drug for the prevention and treatment of DD.

Can the management of depression in type 2 diabetes be democratized?

Both type 2 diabetes and depression are common and are projected to increase.There is increasing evidence for a bidirectional relationship between the two.Diabetes is a risk factor for depression;contrariwise,individuals with depression are at greater risk of developing diabetes.They are a burden for both the individual and the society.Co-existent depression worsens diabetic control because of obesity,insulin resistance and the adverse metabolic effects of anti-diabetes medicines.In addition,compliance to lifestyle measures required for diabetes is also compromised such as following a specific diet,taking proper medications on time,getting metabolic parameters assessed and maintaining a sleep cycle.Depression occurs in many grades;mild depression is more common in diabetes than frank or full-blown depression leading to suicide.Unfortunately,there are not enough trained and accessible mental health professionals such as psychologists or psychiatrists to deal with the increasing burden of depression in diabetes.Therefore,alternate models for management of mild to moderate depression are required.There is evidence that a team-approach by employing health care assistants can lower the risk of cardiac risk factors.INtegrating DEPrEssioN and Diabetes treatmENT study was carried out to determine whether the team-approach using non-health care professionals could be effective in managing mild to moderate depression and to study its effects on metabolic parameters among subjects with type 2 diabetes mellitus.The international study,carried out in four independent centers in India assessed the impact of a trained but not qualified non-psychiatrist in coordinating and forming a fulcrum between the patient,the family and the consultant endocrinologist/diabetologist.The interventions were fine-tuned to be culturally appropriate by qualitative interviews before they began.It was shown that the outcomes of both depression and diabetes could be improved by the employment of a clinical care coordinator.It is possible to scale up the studies to wider geographical areas and health-care organizations.