Analysis of glucose metabolism of 18F-FDG in major depression patients using PET imaging: Correlation of salivary cortisol and α-amylase

• MDD patients showed higher salivary cortisol, sAA and decreased glucose metabolism of 18F-FDG in several brain regions.
• The study evaluated the relationship between measurements of depression, PET imaging, cortisol and sAA in MDD patients.
• Cortisol, sAA, glucose metabolism of superior frontal gyrus and rectal gyrus may serve as biomarkers for diagnosis of MDD.

Current diagnosis of Major depressive disorder (MDD) depends on its clinical symptoms, not on the results of any laboratory examinations. Establishing biological markers for diagnosis of MDD is one of the most important problems to be solved in psychiatry practice. MDD patients (n = 8) and a healthy control group (n = 8) were recruited in this study. Hamilton Depression Rating Scale (HAM-D) assessments were completed and saliva samples were collected for assessments of salivary cortisol and salivary α-amylase (sAA). PET examination was performed. Salivary cortisol and sAA in the MDD patients group were significantly higher than the healthy control group (P < 0.001). MDD patients showed lower glucose metabolism of 18F-FDG in Cingulate Gyrus (BA24), Superior Frontal Gyrus (BA6), Rectal Gyrus (BA11) and Orbital Gyrus (BA11/47) compared with the healthy control group. The severity of depression, salivary cortisol and sAA correlated negatively with regional glucose metabolism in Cingulate Gyrus (BA 24), Superior Frontal Gyrus (BA 6), Rectal Gyrus (BA 11) and Orbital Gyrus (BA 11/47). The combination of salivary cortisol, sAA, superior frontal gyrus and rectal gyrus was the potential predictor of depression for MDD patients (ΔR2 = 0.981, p < 0.001). The present study showed that, MDD patients group showed higher salivary cortisol, sAA levels and lower glucose metabolism of 18F-FDG in several brain areas compared with the healthy control group. The combination of salivary cortisol, sAA, glucose metabolism of 18F-FDG of superior frontal gyrus and rectal gyrus may serve as a simple clinical tool for the early diagnosis of MDD.