Effects of glucose on formation of cytotoxic end‐products and proteolytic activity of Prevotella intermedia, Prevotella nigrescens and Porphyromonas gingivalis

Abstract

Black-pigmented bacteria which produce cytotoxic metabolic end-products and cell membrane-associated proteases have been reported to play an important role in the pathogenesis of periodontal diseases. These bacterial virulence factors can be modified by the environmental conditions including nutrients supplied variously into the oral cavity. Although glucose is one of the most essential nutrients for oral bacteria, the exogenous supply of glucose may be discontinuous and the glucose concentration in a periodontal pocket may be influenced by the depth of the periodontal pocket. Therefore, effects of glucose as an environmental factor on the virulence factors of Prevotella intermedia, Prevotella nigrescens and Porphyromonas in the presence o glucose.,bo t P. intermedia and P. nigrescens markedly decreased the production of cytotoxic end-products including succinate.,isobutyrate,isovalerate and ammonia, although their growth was increased. Furthermore, the proteolytic activities such as immunoglobulin- albumin- and casein-degrading activities of these bacteria were decreased in the presence of glucose. On the other hand, no effect of glucose on the metabolic activity of P gingivalis was observed. These results suggest that pathogenicity of P. intermedia P. nigrescens may be decreased by the presence of glucose.

Occurrence of red complex microorganisms and Aggregatibacter actinomycetemcomitans in patients with diabetes

“…The increase of GCF efflux with increasing inflammation provides not only higher levels of glucose, but also various host‐defense proteins that help maintain the host–bacteria balance. For this reason, the pathogenic activity of subgingival bacteria, such as the production of tissue host‐degrading enzymes and toxic end‐products, is linked to their metabolic adaptation for survival in the subgingival area . The lower frequencies of red complex pathogens in diabetic patients in the present study might be related to the high glucose concentration in plasma and GCF .…”

Integrated hypothesis of dental caries and periodontal diseases

“…Continued proteolysis along with acid neutralization by Fusobacterium and Prevotella [32] may help to generate an alkaline environment for the succession of more acid sensitive 'inflammophilic' species, such as Porphyromonas gingivalis [33]. In this scenario, Prevotella intermedia plays an important modulatory role because it can live in both a sugar-rich supragingival environment and in a protein-rich, neutral to weakly alkaline subgingival environment; yet its cytotoxic and proteolytic virulence is increased only when sugar is absent, such as in subgingival sites with restricted access to dietary sugars [34].…”

“…However, excess bacterial proteolytic activity, e.g. due to bacterial accumulation and/or bacterial adaptation to a GCF-rich environment [34] can be cytotoxic and aggravate tissue inflammation by modulating host-immune responses [58] and promoting apoptosis [59].…”

Pathogenic Bacterial Species Associated with Endodontic Infection Evade Innate Immune Control by Disabling Neutrophils

“…P. intermedia also produces a protease, interpain A, that can inactivate complement (37), but this activity is unlikely to cause the extreme damage to neutrophils that occurred in the chambers. Alternatively, both P. intermedia and F. nucleatum can generate succinate during metabolic activity (38,39), and succinate has the ability to suppress neutrophil phagocytosis (40). While this activity may contribute to the toxic activity of the EP, it is unlikely to act alone, since succinate suppresses phagocytosis in neutrophils but does not directly kill them.…”