Science Update - Gum and Heart Disease

Introduction

Scientists have long noticed a connection between gum disease and heart disease. Now, they’ve found a key piece of the puzzle.

Podcast
Gum and Heart Disease


Transcript

From dental plaque to artery plaque. I’m Bob Hirshon and this is Science Update.

For years, scientists have noticed a link between gum disease and heart disease. Now, researchers at the University of Florida have found the smoking gun. Microbiologist Ann Progulske-Fox and her colleagues found two kinds of oral bacteria in human artery plaque, a sticky substance that clogs blood vessels.

Progulske-Fox:

We’ve never known until now, for sure, that live bacteria from the periodontal area actually can live and invade the cells lining the arteries.

She says it’s not clear how they do it, but suspects only certain strains have the ability to travel from gum to artery tissue. Their goal is to identify these strains, so that dentists and cardiologists can work together on treatments. I’m Bob Hirshon for AAAS, the Science Society.
Making Sense of the Research

Over the past ten years, there have been many studies linking gum disease and hardening of the arteries. At first, there were observations that people with poor oral health were more prone to heart disease. More recently, scientists have found clear links between the total amount of periodontal bacteria in the mouth and blockages in the carotid artery. Fragments of DNA from periodontal bacteria have even been identified in artery plaque.

Sounds like an open and shut case, right? Not so fast. Like lawyers, scientists have to provide concrete, rock-solid evidence to support their claims. The sticking point here has always been the body’s immune system. People with gum disease generally have bleeding gums, and all those little cuts and tears would give the bacteria the opportunity to enter the bloodstream. But once they got there, many scientists have argued, the immune system might quickly kill them off. Given this possibility, those scraps of bacteria DNA in the arteries might have been from dead bacteria that never got to cause any real damage.

This study proves that at least some of the bacteria manage to escape that fate. For the first time, Progulske-Fox and her colleagues actually grew cultures of live periodontal bacteria from samples of artery plaque. Since you can’t grow live bacteria from dead ones, this proves that there were some bacteria living in the plaque when it was still in the donor’s artery.

Progulske-Fox says the bacteria have a couple of secret weapons that allow them to invade the artery tissue. First, their surfaces have “sticky” proteins that allow them to glom on to the lining of the arteries without being flushed away in the bloodstream. Once they’re stuck, these bacteria can quickly “unlock” the artery cells and get inside them. And once they’re inside the artery tissue, the immune system can’t get them.

What’s interesting is that gum tissue and artery tissue aren’t very similar. So why should some bacteria attack both of them? That question remains unanswered, but it’s one of the reasons Progulske-Fox suspects that only certain strains have the potential to do double damage. Identifying those strains is the next step in this ongoing scientific detective story.

Now try and answer these questions:

What was known about gum disease and heart disease prior to this study?

What’s new and important about this study?

Why was this study necessary, given all the other evidence?

If the researchers had NOT been able to grow live periodontal bacteria from artery tissue, what do you think their next move should have been?