The Role of the Oral Microbiome in Diabetes
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By Dr. Diana Kessler
In my previous post, “The Other Microbiome – The Microbes Living in Our Mouth“, I describe the oral microbiome and the processes that lead from eubiosis (normal composition of oral microbes) in the mouth to dysbiosis (altered composition). First gingivitis develops, later periodontitis. Depending on the severity and the number of teeth in the mouth, this chronic inflammatory disease presents a wound on our body up to the size of a palm, through which bacteria and other germs can enter the bloodstream. For over 32 years, my daily work has been to heal this wound by periodontal treatment and to maintain the eubiotic condition by dental prophylaxis.
“…depending on the severity and the number of teeth in the mouth, this chronic inflammatory disease presents a wound on our body up to the size of a palm, through which bacteria and other germs can enter the bloodstream…”
Like periodontitis, type II diabetes is also a widespread disease. Worldwide, the number of people affected by diabetes is estimated at 463 million, and 4.21 million die each year.
Until the 1920s, a diagnosis of diabetes was a death sentence. This changed with the discovery of insulin, one of the greatest breakthroughs in modern medicine. But what actually is this miracle drug insulin? It is a very small protein that is produced in our pancreas. Insulin helps to keep our blood sugar continuously in balance. A molecule like this only survives for about 5 to 15 minutes, so we need a lot of it in our lives.
The balance between high and low blood sugar is very sensitive: too little sugar in the blood is particularly dangerous for our brain, which depends on it as an energy source. Severe hypoglycemia is even life-threatening. Too much sugar, in turn, slowly damages blood vessels and nerves, and this affects important organs of our body, especially the cardiovascular system, the eyes, the kidneys and the nervous system. And also the periodontium, as we will see in the following.
“While simple carbohydrates we eat (such as bread, pasta and rice and fruits) are broken down into glucose which in turn is absorbed via special transporters in the lining of the first part of our gut, more complex carbohydrates (such as contained in most vegetables, wild rice and whole wheat bread) cannot be absorbed by our intestine directly…”
How does this small molecule insulin manage to be so important in our body? When we eat something, our food is broken down into smaller building blocks as it continues its journey through our small intestine. These are absorbed into the blood via the mucous membrane of our small intestine. The surface area of our small intestinal mucosa is enormous due to its primary and secondary (“microvilli”) foldings. It has been calculated to be about 2,000 square meters, about the size of a basketball field. While simple carbohydrates we eat (such as bread, pasta and rice and fruits) are broken down into glucose which in turn is absorbed via special transporters in the lining of the first part of our gut, more complex carbohydrates (such as contained in most vegetables, wild rice and whole wheat bread) cannot be absorbed by our intestine directly, but require breakdown by our gut microbes into smaller molecules, such as short chain fatty acids before absorption. These complex carbohydrates are also called Microbe Accessible Carbohydrates or MACs.
Glucose is distributed throughout our body via the blood; It is the fuel for our cells. Our brain alone uses around ten tablespoons of glucose a day. The brain is dependent on glucose as a primary energy substrate, but is capable of utilizing ketones such as β-hydroxybutyrate (βHB) and acetoacetate (AcAc), as occurs with fasting, prolonged starvation or chronic feeding of a high fat/low carbohydrate diet (ketogenic diet). Normally, there are about 80 to 120 milligrams of glucose in 100 milliliters of blood at any given time, which is about one to two teaspoons extrapolated to our entire body.
Insulin is a hormone. Hormones are all those substances in our body that are formed in one place, transported in the bloodstream throughout the body, and whose effects are felt in other parts of us. They are, so to speak, message carriers or messengers. The task of insulin is to open the door, like a key, to the cells where glucose is to be absorbed. To do this, it docks onto the so-called insulin receptors. In this way, it transports glucose primarily to the cells of the muscles, liver, kidneys and fatty tissue. Only our brain can absorb glucose directly, i.e. without the help of insulin. Therefore, as already discussed, a drop in blood glucose is a state of alarm, especially for our brain. If too much glucose flows through our blood, insulin ensures that it is stored in the form of glycogen in the liver and in our muscles.
If our body needs energy again, even though we haven’t eaten for a while, it falls back on these glycogen stores. To do this, however, they have to be converted into ketone bodies or glucose again by the liver. In addition, the liver can produce glucose itself – up to 500 grams a day – which it releases into the bloodstream. Although there are other hormones and mechanisms in these regulatory circuits, which I will not go into here, insulin is the only substance that can lower blood glucose, by facilitating the uptake into cells.
In addition to this “key” function, insulin also has other tasks. For example, it affects our appetite or inhibits the breakdown of fatty tissue. All this, which works together so wonderfully in a healthy person without us ever having to think about it, becomes unbalanced in diabetes.
While type 1 diabetes is considered an autoimmune disease in which heredity plays an important role, the much more common type 2 diabetes is a “civilization disease“ associated with our Western lifestyle.
Like high blood pressure and high blood lipids, diabetes does not show any symptoms at an early stage. It is currently estimated that six to seven years pass between the onset of the disease and diagnosis. The preliminary stage of the disease is called glucose tolerance disorder. In this case, the so-called glycemic parameters – blood glucose levels – are already above normal, but do not yet reach the threshold value defined for the disease. Here, too, the number of cases is increasing worldwide year after year. 5 to 10 percent of people with a glucose tolerance disorder develop diabetes every year.
The phase between onset and diagnosis is, of course, particularly dangerous, as there is too much sugar in the blood here, at least temporarily. The longer this phase lasts, the greater the potential damage to the eyes, kidneys, blood vessels, nerves and heart.
“…The two chronic diseases – diabetes and periodontitis – are interrelated, and they are intricately connected to our modern lifestyle, in particular our Western diet.”
The two chronic diseases – diabetes and periodontitis – are interrelated, and they are intricately connected to our modern lifestyle, in particular our Western diet. On the one hand, the inflammation in periodontitis affects blood glucose levels. This is because inflammatory molecules are produced that disrupt the mechanism by which insulin binds to the insulin receptors in the individual cells. The key therefore no longer fits properly, and insulin resistance develops. This prevents the uptake of glucose into the cells and blood glucose remains elevated. If diabetes is already present, periodontitis makes blood glucose control more difficult and thus increases the risk of concomitant diseases.
But conversely, diabetes can also lead to a worsening of periodontitis. That means, that the relationship between the two diseases is bidirectional. If the increase in blood glucose continues, other protein molecules combine with the glucose circulating in the blood and so-called AGEs (advanced glycated end products) are formed, which promote inflammatory diseases such as periodontitis in different ways. If these AGEs are recognized by body cells – for example by white blood cells or cells of the vascular wall – this triggers the formation of pro-inflammatory molecules. On the one hand, these messenger substances summon further inflammatory cells, and on the other hand, they worsen wound healing. Both accelerate the destruction of the periodontium. There are other mechanisms that are being discussed in this context and research into them is continuing.
Clinical studies have shown that diabetics with periodontitis have higher HbA1c levels than periodontally healthy individuals and that the severity of periodontal disease correlates with glycemic control.
“…in type 2 diabetics with severe periodontitis, mortality due to coronary heart disease was 2.3-fold higher compared to periodontally healthy or mildly periodontally diseased diabetics, and mortality due to diabetic nephropathy (kidney disease) was 8.5-fold higher in patients with severe periodontitis than in those with periodontally healthy or mildly periodontally diseased mouths.”
An interdisciplinary approach thus achieves success in two directions. On the one hand, effective periodontal treatment has a favorable effect on the blood glucose of diabetics. On the other hand, good glycemic control ensures the long-term success of periodontal therapy. Further studies have shown that periodontitis increases the risk of diabetes-associated complications. In type 2 diabetics with severe periodontitis, mortality due to coronary heart disease was 2.3-fold higher compared to periodontally healthy or mildly periodontally diseased diabetics, and mortality due to diabetic nephropathy (kidney disease) was 8.5-fold higher in patients with severe periodontitis than in those with periodontally healthy or mildly periodontally diseased mouths.
Periodontitis is not only linked to diabetes, but also to cardiovascular, kidney and lung diseases, Alzheimer’s disease, rheumatoid arthritis, cancer and more. All these chronic diseases seem somehow intertwined through the maladaptive engagement of the immune system. And they are all connected to our civilization-related dietary and exercise habits. Our bodies, once created in the society of hunter-gatherers to cope with long distance running and the accumulation of vital fat deposits to overcome periods of hunger, suffer from too much food and too little exercise. In the fight against these diseases, we should not only focus on nutrition and exercise, but also on our oral hygiene.
Dr. Diana Kessler studied dentistry at the University of Heidelberg in Germany and has worked as a dentist in private practice since 1991, Dr. Kessler has seen patients at the diabetes outpatient clinic at the St. Josef Hospital in Heidelberg since 2012, and has lectured on the topic of oral and general health, and on the role of the oral microbiome in chronic disease. She is the author of the book, Gesund durch den Mund