DM and periodontitis are both the common, chronic disease [10]. The epidemiological data confirmed that DM was the main risk factor of periodontitis and the susceptibility to periodontitis increases about threefold in people with DM [11]. However, the molecular mechanisms of complex interactions between DM and periodontitis are still unclear. This study was the first research to explore the shared genes and common signatures of DM and periodontitis via bioinformatic analysis. LAPTM5, RAC2 and LYN were determined the hub genes, which were all up-regulated in both DM and periodontitis. Besides, they were associated with phagocytosis, B cell activation and T cell activation.
LAPTM5, a negative regulator of T and B cell receptor and a positive modulator of macrophages, is preferentially expressed in immune cells [12, 13]. T and B cells are the main immunosuppressive cells that maintain immune homeostasis [14]. B cells IgG could protect the host from periodontopathogen infection [15], and CD4 T-cell subset also plays a significant role in periodontitis [16]. Interestingly, healthy controls exhibit a higher CD40 and B cells than DM patients [17]. Because B cells proceed anti-inflammatory cytokines IL-10 to abolish the self- or islet-reactive peptides [17]. A reporter indicated that LAPTM5 was the positive modulator of inflammatory signaling pathways and hence cytokine secretion in macrophages [18]. It's worth noting that DM patients, characterized with hyperglycemia could polarize macrophage toward M1 macrophages to induce inflammatory response, which might take responsibility for aggravated periodontal damage in periodontitis under diabetic condition [19]. Our research determined LAPTM5 as the hub gene, which participate the phagocytosis, B cell activation and T cell activation and play an important in the development of periodontitis and DM.
RAC2 is the member of Ras superfamily of small guanosine triphosphate-metabolizing proteins and the key factor of B cell development and T cell activation [20–22]. The deficiency of RAC2 significant prevent the T-cell and B-cell development [23, 24]. Our results showed that RAC2 was up-regulated in periodontitis and DM groups, which was consistent with the previous reporters [25, 26]. Thiago et al indicated that in diabetic mice, the decreased activation of RAC2 protect the vascular injury in DM [27]. In addition, RAC2 also participated the biological process of insulin-secreting INS-1 cells against cytokine-induced apoptosis [28]. Corneliu et al found the more sever bone loss at the alveolar bone to the periodontal ligament interface in RAC2-null mice compared with WT mice. It explained as the activation of inflammatory macrophages, B and T cell synthesize prostaglandin E2 to generate pro-osteoclastic environments and the absent of RAC2 influence the osteoclast maturation and function [29]. RAC2 was identified the hub gene of DM and periodontitis which involving the activation of B cells and T cells.
LYN gene could encode tyrosine protein kinase Lyn (LynK) which were expressed in B cells, adipose tissue, hematopoietic cells et al [30]. LynK has emerged as one of the most attractive therapeutic targets for DM, which was upregulated under diabetic stress [31, 32]. Continuous intake of green tea could reduce the risk of DM via lowing of fasting blood glucose levels and "Benifuuki" green tea has been shown to the suppression of LynK of cellular protein kinas to prevent the release of histamine [33]. Similar to our results, Li et al. also found that LYN was the identified as the key gene of periodontitis [34]. However, it needed more data to support the role of LYN in the development of periodontitis.
Our study exists some limitations: a. the three hub genes LAPTM5, RAC2, LYN have not been validated by laboratory experiments, although their role in DM and periodontitis have been reflected in some clinical and animal research; b. the results also needed further verified in the patients with DM and periodontitis, which will be conducted when the datasets exist.