How gum disease may cause metabolic syndrome

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Gum disease is known to be a big risk factor of metabolic syndrome, a group of health conditions increasing the risk for heart disease and diabetes.

In a new study, researchers found that infection with Porphyromonas gingivalis, the bacterium causing gum disease, causes muscle metabolic dysfunction, the precursor to metabolic syndrome, by altering the composition of the gut microbiome.

The research was conducted by a team from Tokyo Medical and Dental University (TMDU).

Periodontal bacteria have long been known to cause inflammation within the oral cavity, but also increase inflammatory mediators.

As a result, sustained infection with periodontal bacteria can lead to increases in body weight and lead to insulin resistance, a hallmark of type 2 diabetes.

The function of insulin is to help shuttle glucose from the blood into tissues, most importantly to muscle, where one-quarter of all glucose in stored.

Unsurprisingly, insulin resistance plays a key role in the development of metabolic syndrome, a group of conditions including obesity, altered lipid metabolism, high blood pressure, high blood glucose levels, and systemic inflammation.

Although muscle plays a key role in decreasing blood glucose levels, a direct connection between periodontal bacterial infection and the metabolic function of skeletal muscle has not been established yet.

In the study, the team examined antibody titers to Porphyromonas gingivalis in the blood of patients with metabolic syndrome and found a positive correlation between antibody titers and increased insulin resistance.

These results showed that patients with metabolic syndrome were likely to have undergone infection with Porphyromonas gingivalis and thus have mounted an immune response yielding antibodies against the germ.

But how was this bacterium capable of causing systemic inflammation and metabolic syndrome?

To answer this question, the researchers focused on the gut microbiome, the network of bacteria present in the gut, and with which the organism co-exists symbiotically.

They found that in mice administered with Porphyromonas gingivalis the gut microbiome was strongly altered, which might decrease insulin sensitivity.

These are striking results that provide a mechanism underlying the link between infection with the periodontal bacterium and the development of the metabolic syndrome and metabolic dysfunction, the team says.

One author of the study is Professor Sayaka Katagiri.

The study is published in The FASEB Journal.

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