Peripheral inflammation is associated with alterations in brain biochemistry and mood: evidence from in vivo proton magnetic resonance spectroscopy study

Abstract

Abstract Tumor necrosis factor (TNF)-α is a protein implicated in the prognosis of psoriatic arthritis (PsA), an autoimmune disease associated with episodes of clinical depression (CD). CD has been linked to abnormalities in the forebrain and subcortical structures, which can be probed noninvasively using proton magnetic resonance spectroscopy (1H-MRS). Thus, this 1H-MRS study assessed biochemical differences between healthy subjects and PsA patients in the frontal and bilateral hippocampal brain regions. Biochemical and mood responses in the anterior cingulate cortex and bilateral hippocampi following the administration of anti-TNF-α medication to the PsA patients were also assessed. Fifteen volunteers in each of the PsA and control groups participated in the study. Patients underwent MRS examination before and after 6–8 weeks of anti-TNF-α medication. Mood was assessed at baseline and after medication using the Beck’s Depression Inventory (BDI). Psychiatric symptoms were ruled out in all volunteers using the 12-item General Health Questionnaire. MRS studies were conducted using the PRESS sequence at 3 T. Spectral and statistical analyses were conducted using the LC Model and Minitab software, respectively. Metabolite levels were expressed as ratios, relative to the creatine peak. The PsA patients showed higher left hippocampal baseline Choline/Creatine ratio than controls (p = 0.014). After medication, decrease in frontal brain Choline/Creatine ratio was associated with decrease in BDI scores (r = 0.628; p = 0.025), while frontal brain NAA/Creatine ratio was significantly lower in the PsA patients compared to the controls (p = 0.023). No other significant differences were found in all comparisons, including metabolite ratios between the left and right hippocampi. The results of this study provide some evidence for biochemical alterations in the mood regulating segments of the brain, which has consequences for mood states of the affected patients.