Experimental Periodontitis Results in Prediabetes and Metabolic Alterations in Brain, Liver and Heart: Global Untargeted Metabolomic Analyses

Abstract

Results from epidemiological studies suggest that there is an association between periodontitis and prediabetes, however, causality is not known. The results from our previous studies suggest that induction of periodontitis leads to hyperinsulinemia glucose intolerance and insulin resistance, all hallmarks of prediabetes. However, global effects of periodontitis on critical organs in terms of metabolic alterations are unknown. We determined the metabolic effects of periodontitis on brain, liver, heart and plasma resulting from Porphyromonas gingivalis induced periodontitis in mice. Periodontitis was induced by oral application of the periodontal pathogen, Porphyromonas gingivalis for 22 weeks. Global untargeted biochemical profiles in samples from these organs/plasma were determined by liquid and gas chromatography/mass spectrometry and compared between controls and animals with periodontitis. Oral application of Porphyromonas gingivalis induced chronic periodontitis and hallmarks of prediabetes. The results of sample analyses indicated a number of changes in metabolic readouts, including changes in metabolites related to glucose and arginine metabolism, inflammation and redox homeostasis. Changes in biochemicals suggested subtle systemic effects related to periodontal disease, with increases in markers of inflammation and oxidative stress most prominent in the liver. Signs of changes in redox homeostasis were also seen in the brain and heart. Elevated bile acids in liver were suggestive of increased biosynthesis, which may reflect changes in liver function. Interestingly, signs of decreasing glucose availability were seen in the brain. In all three organs and plasma, there was a significant increase in the microbiome-derived bioactive metabolite 4-ethylphenylsulfate sulfate in animals with periodontitis. The results of metabolic profiling suggest that periodontitis/bacterial products alter metabolomic signatures of brain, heart, liver, and plasma in the prediabetic state. These data provide scientific community valuable metabolic signatures that become the basis for understanding the impact of periodontitis on a systemic disease and potentially targets for therapeutic intervention.

Chronic oral application of a periodontal pathogen results in brain inflammation, neurodegeneration and amyloid beta production in wild type mice

“…Oral application of Pg is frequently used in the field of periodontal research with various durations of application [ 15 , 16 , 17 , 18 , 19 ]. It is important to note that in our chronic model system, we confirmed the development of periodontitis by assessing bone loss around teeth and there were no differences in body weight and food consumption between control and experimental groups [ 20 ].…”

“…Pg (strain W83) was grown anaerobically as described in our previous study [ 20 ]. Cell density was determined by spectrophotometry at an optical density of 550 nm based on a standard curve established using colony forming units (CFU).…”

“…Supernatants were discarded and the pellets were re-suspended in 4 o C PBS, and then re-pelleted by centrifugation. Supernatants were removed, and bacteria re-suspended in 100 μl of 2% carboxymethyl cellulose (CMC) in PBS and tubes immediately placed on ice until administered to mice as described [ 20 ].…”

“…Mice were sacrificed using isoflurane anesthesia followed by cervical dislocation and decapitation at the 23rd week and the brains were removed quickly with one hemisphere fixed in paraformaldehyde to be embedded in paraffin (formalin fixed paraffin embedded, FFPE samples) for immunofluorescence/histochemical analyses and the other half snap frozen and used for metabolomics analysis. The results of this metabolomic study have been published [ 20 ].…”

“…To test this hypothesis, we subjected 8-week old C57BL/6 WT mice to experimental chronic periodontitis by repeated oral application of the periodontal pathogen, Pg, for 22 weeks [ 20 ] and examined the hippocampi of mice administered Pg (experimental group) or vehicle alone (control group) for the development of neuropathology. As mentioned, we documented that these mice developed periodontitis as assessed by loss of tooth supporting bone.…”