TNF and periodontitis: These are chronically overexpressed in advanced periodontitis and can be released into the blood to affect other organs and exacerbate metabolic diseases (Kashiwagi et al., 2021); however, several reports have shown that the levels of serum TNF-α and other pro-inflammatory cytokines in periodontitis patients are not elevated compared with those of healthy subjects (Yamazaki et al., 2005).