A Study of the Relationship between Inflammatory Immune Function and Intestinal Flora in Adolescent Patients with First-Episode Depression

Abstract

Background: Depression has become one of the most common mood disorders in adolescents, with an increasing incidence each year. Abnormal activation of peripheral immunity causes an increase in pro-inflammatory factors, which in turn affects neuroendocrine dysfunction and alters neurobiochemistry, leading to depression. In this study, we aimed to explore the relationship between inflammatory immune function and intestinal flora in adolescents with first-episode depression.

Methods: A total of 170 cases of adolescent patients with first-episode depression who attended our hospital from January 2020 to March 2023 were retrospectively selected as the observation group. Simultaneously, 170 individuals who underwent a healthy physical examination during the same period were chosen as the control group. The enzyme-linked immunosorbent assay (ELISA) was employed to quantify the levels of monoamine neurotransmitters 5-hydroxytryptamine (5-HT), substance P (SP), neuropeptide Y (NPY), serum tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, and IL-6 in the patients. Flow cytometry was utilized to assess the levels of T-lymphocytes CD3⁺, CD4⁺, and CD8⁺ cells. The levels of 16S ribosomal RNA (16SrRNA) method were used to determine the intestinal flora of the subjects in both groups. Inflammatory factor levels, immune function, and intestinal flora expression were observed, and correlation analysis was performed.

Results: The levels of 5-HT and NPY in the observation group were lower than those in the control group. The SP level was significantly higher in the observation group compared to the control group (p < 0.05). The observation group demonstrated significantly higher TNF-α, IL-1β, and IL-6 levels than the control group (p < 0.05). The values of CD3⁺, CD4⁺, CD4⁺/CD8⁺ in the observation group were lower than those in the control group (p < 0.05), whereas the CD8⁺ values were notably higher (p < 0.05). Bifidobacterium, Escherichia coli, Lactobacillus, and Bacteroides in the observation group were less than those in the control group (p < 0.05). The content of Bifidobacterium was negatively correlated with the level of TNF-α (r = –0.358, p < 0.001), positively correlated with the level of CD3⁺, CD4⁺, CD4⁺/CD8⁺ (r = 0.490, 0.169, 0.165, p < 0.05), and negatively correlated with the level of CD8⁺ (r = –0.154, p < 0.05). The level of Escherichia coli content was negatively correlated with the levels of IL-6, CD3⁺, CD4⁺, CD4⁺/CD8⁺ (r = –0.483, –0.548, –0.317, –0.328, p < 0.001), and positively correlated with the levels of CD8⁺ (r = 0.325, p < 0.001). The content of Lactobacillus was positively correlated with the levels of CD3⁺, CD4⁺, CD4⁺/CD8⁺ (r = 0.552, 0.188, 0.194, p < 0.05), and negatively correlated with the level of CD8⁺ (r = –0.186, p < 0.05). The content of Bacteroides was positively correlated with the level of CD3⁺, CD4⁺, CD4⁺/CD8⁺ (r = –0.570, –0.183, –0.193, p < 0.05), and negatively correlated with the level of CD8⁺ levels were positively correlated (r = 0.187, p < 0.05).

Conclusions: The intestinal flora is related to the level of inflammatory factors and immune function. Further study on the relationship between intestinal flora, inflammatory immune function, and depression could offer novel insights for the prevention and treatment of depressive disorders.