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Bacteria May Cause Type-2 Diabetes

Study suggests antibacterial therapy, vaccines may help prevent or treat the disease

Bacteria and viruses have an obvious role in causing infectious diseases, but microbes have also been identified as the surprising cause of other illnesses, including cervical cancer (human papillomavirus) and stomach ulcers (Helicobacter pylori bacteria).

A new study by microbiologists at the University of Iowa now suggests that bacteria may also be a cause of type-2 diabetes (T2D).

The researchers found that prolonged exposure to a toxin produced by Staphylococcus aureus (staph) bacteria causes rabbits to develop the hallmark symptoms of T2D, including insulin resistance, glucose intolerance, and systemic inflammation.

“We basically reproduced type-2 diabetes in rabbits simply through chronic exposure to the staph superantigen,” said lead investigator Patrick Schlievert, PhD.

The team’s findings suggest that therapies aimed at eliminating staph bacteria or neutralizing the superantigens might have a potential for preventing or treating T2D.

Obesity is a known risk factor for developing T2D, but obesity also alters a person’s microbiome –– the ecosystem of bacteria that colonize a person’s body and affect his or her health.

“What we are finding is that as people gain weight, they are increasingly likely to be colonized by staph bacteria –– to have large numbers of these bacteria living on the surface of their skin,” Schlievert said. “People who are colonized by staph bacteria are being chronically exposed to the superantigens the bacteria are producing.”

Schlievert’s research has previously shown that superantigens –– toxins produced by all strains of staph bacteria –– disrupt the immune system and are responsible for the potentially deadly effects of various staph infections, such as toxic shock syndrome, sepsis, and endocarditis.

The team’s latest study, published in the journal mBio, shows that superantigens interact with fat cells and the immune system to cause chronic systemic inflammation, and that this inflammation leads to insulin resistance and other symptoms characteristic of T2D. In examining the levels of staph colonization on the skin of four patients with diabetes, Schlievert’s team estimated that exposure to the bacterial superantigens for people who are heavily colonized by staph is proportional to the doses of superantigen that caused the rabbits to develop diabetes symptoms in the team’s experiments.

“I think we have a way to intercede here and alter the course of diabetes,” Schlievert said. “We are working on a vaccine against the superantigens, and we believe that this type of vaccine could prevent the development of type-2 diabetes.”

The team is also investigating the use of a topical gel containing glycerol monolaurate, which kills staph bacteria on contact, as an approach to eliminate staph bacteria from human skin. They plan to test whether this approach will improve blood sugar levels in patients with prediabetes.

Source: EurekAlert; June 1, 2015.

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