The role of zinc deficiency-induced changes in the phospholipid-protein balance of blood serum in animal depression model by Raman, FTIR and UV-vis spectroscopy

Depression is a serious mental illness. To study the mechanisms of diseases and search for new, more effective therapies, animal models are used. Unfortunately, none of the available models does reflect all symptoms of depression. Zinc deficiency is proposed as a new animal model of depression. However, it has not been yet validated in a detailed manner. Recently, spectroscopic techniques are increasingly being used both in clinical and preclinical studies.Here we examined the effect of zinc deficiency and amitryptyline treatment on the phospholipid - protein balance in the blood serum of rats using Raman, Fourier Transform Infra Red (FTIR) and UV-vis technique. Male Sprague Dawley rats were fed with a zinc ample diet (ZnA, 50 mg Zn/kg) or a zinc deficient diet (ZnD, 3 mg Zn/kg) for 4 weeks. Then amitriptyline administration (AMI, 10 mg/kg, i.p.) was started. After injecting the drug for 2-weeks, blood samples were collected and analyzed.It was found that zinc deficiency decreases both the level of phospholipids and proteins and also causes structural changes in their structures. In the ZnD group amitriptyline treatment influenced the protein level and structure. UV-vis spectroscopy combined with the second derivative calculated from the FTIR spectra provided information that the proteins in blood serum of rat fed with a low Zn diet regain their intact structure after amitriptyline medication. Simultaneously, the antidepressant therapy did not have any effect on the level of phospholipids in this group of rats. Additionally, our results show, that amitriptyline administration can change the structure of phospholipids in rats subjected to zinc ample diet. This altered structure of phospholipids was identified as shortening of carbon chains.Our findings indicate that the decreased level of zinc may be the cause of depressive disorders, as it leads to changes in the phospholipid-protein balance necessary for the proper functioning of the body. This study also shows possible new applications of spectroscopic techniques in the diagnosis of affective disorders, and maybe even identifies markers of depressive disorders.