The “Gum–Gut” Axis in Inflammatory Bowel Diseases: A Hypothesis-Driven Review of Associations and Advances

Abstract

In modern medicine, the oral cavity has often been viewed as a passive conduit to the upper airways and gastrointestinal tract; however, its connection to the rest of the body has been increasingly explored over the last 40 years. For several diseases, the periodontium and gingiva are at the center of this oral-systemic link. Over 50 systemic conditions have been specifically associated with gingival and periodontal inflammation, including inflammatory bowel diseases (IBD), which have recently been elevated from simple “associations” to elegant, mechanistic investigations. IBD and periodontitis have been reported to impact each other’s progression via a bidirectional relationship whereby chronic oral or intestinal inflammation can impact the other; however, the precise mechanisms for how this occurs remain unclear. Classically, the etiology of gingival inflammation (gingivitis) is oral microbial dysbiosis in the subgingival crevice that can lead to destructive periodontal disease (periodontitis); however, the current understanding of gingival involvement in IBD is that it may represent a separate disease entity from classical gingivitis, arising from mechanisms related to systemic inflammatory activation of niche-resident immune cells. Synthesizing available evidence, we hypothesize that once established, IBD can be driven by microbiomial and inflammatory changes originating specifically from the gingival niche through saliva, thereby worsening IBD outcomes and thus perpetuating a vicious cycle. In this review, we introduce the concept of the “gum–gut axis” as a framework for examining this reciprocal relationship between the periodontium and the gastrointestinal tract. To support and explore this gum–gut axis, we 1) provide a narrative review of historical studies reporting gingival and periodontal manifestations in IBD, 2) describe the current understanding and advances for the gum–gut axis, and 3) underscore the importance of collaborative treatment and research plans between oral and GI practitioners to benefit this patient population.

Rumen Bacterial Community of Grazing Lactating Yaks (Poephagus grunniens) Supplemented with Concentrate Feed and/or Rumen-Protected Lysine and Methionine

“…The relative abundance of the genus uncultured_o_Absconditabacteriales (SR1) was lesser in yaks with supplementary concentrate feed than those without. Absconditabacteriales was linked with inflammatory bowel diseases [ 40 , 41 ] and periodontal diseases in humans [ 42 ]. In addition, Absconditabacteriales was associated with an unhealthy udder, and it was suggested that this genus could be used as a biomarker to assess mastitis in dairy cows [ 43 , 44 ].…”

Immunological Traits of Patients with Coexistent Inflammatory Bowel Disease and Periodontal Disease: A Systematic Review

“…These Th17 cells of oral origin can be activated by translocated oral pathobionts and cause the development of colitis when in the gut through IL-1β [22]. Indeed, Byrd et al [14] have hypothesized that IBD can be driven by microbiomial and inflammatory changes originating specifically from the gingival niche through saliva, thereby worsening IBD outcomes and thus perpetuating a vicious cycle. In fact, a recent scoping review has found that periodontitis and IBD patients share similarities in their microbiological and immunological patterns [23].…”

“…The persistence and dysregulation of the host immune and inflammatory responses are mainly responsible for the tissue destruction in both IBD and periodontal disease [12,13], and the inflammatory response activation might be the link between them [14]. In fact, the activity of IBD influences the inflammatory response not only in the intestinal tissue but also causes systemic inflammation as demonstrated by the higher levels of TNF-α and IL-17 in the blood of patients with IBD in comparison to patients without IBD or those in disease remission [15][16][17].…”

Oral Versus Gastrointestinal Mucosal Immune Niches in Homeostasis and Allostasis

“…The idea of a bidirectional axis between the mouth and the gastrointestinal tract (GI) is not recent. In fact, possible relationships between the occurrence of pathologies of infectious origin in the oral cavity and inflammatory bowel disorders have been explored for decades ( 1 ). Both the oral tract and the GI tract deal with the external environment because of their vital epithelial barrier function in the digestive system, and such function depends on the interrelation between the host and the microorganisms to regulate either homeostatic balance or pathological instability.…”