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Canadian Medical Alliance for the Preservation of the Lower Extremity
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What is Diabetes?
The subject of this website is ulcers. We discuss how they occur, how they're treated, and a
host of other related topics. But as the most common cause of foot ulcers is diabetes,
we should spend a moment to discuss what diabetes actually is.
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Of course, many of you visiting this website are doing so because you have
a diabetic ulceration and already know all too well what diabetes is.
So, to entertain you as we review a topic you may already know
a lot about, we will also review the difference between sugars
and starches, and we'll discuss why we need to breathe.
We'll also touch on the quirk in our primordial evolution
that allows multicellular organisms like us to exist. We
will point out how you share a special bond with your
great-great-great-great-great-great-great grandmother,
and we'll show you how scientists are able to follow ancient
migration patterns across enormously long stretches of time.
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Diabetes mellitus (which is what most people are talking about when
they're talking about diabetes, as opposed to diabetes insipidus, which
is an entirely unrelated condition) refers to a disease that affects your
body's ability to process sugar.
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There are a number of different types of sugar, but no matter the sugar
eaten, once in the body, it's all broken down into sugar's simplest form
--glucose. Glucose is a single six-sided ring structure that looks like this
figure to the right.
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Being able to process glucose is important because glucose is the main
source of energy for our cells, and when the metabolism of glucose is
disrupted, the body has significant trouble functioning.
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With Type 1 diabetes, the immune system destroys the cells in the pancreas that make insulin. So with Type 1 diabetes, the patient has no insulin. Type 1 diabetes can develop at any age, but tends to develop at younger ages, such as children.
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In Type 2 diabetes, the pancreas produces insulin, but the body doesn't respond to insulin well. And eventually, the body may not be able to make enough insulin. Type 2 diabetes can develop at any age, too, but it is more common after the age of 40. There are more Type 2 diabetics than Type 1.
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There are other forms of diabetes mellitus as well, such as gestational diabetes, which can develop during pregnancy, but the main point for this page is that diabetes is problem with the metabolism of sugar.
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What are the symptoms of diabetes?
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The classic symptoms of diabetes are increased thirst and frequent urination. In fact, the name of diabetes comes to us from the 2nd Century Greek physician, Areteus of Cappadocia, with the term 'diabainein,' meaning to pass through. So the name refers to the fluid passing through the body. For more on this history of diabetes, click here.
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Diabetics may often note weight loss, extreme hunger, fatigue, and irritability. They may feel shaky, weak and develop blurred vision. And diabetics may develop infections and slow-healing sores, particularly on the feet.
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How is our digestive system supposed to deal with sugar?
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When we eat, we need to digest the food, to put it in a usable form. When it comes to simple sugars--like candy bars, donuts, ice cream, cookies, and sugary drinks--the sugar enters our body in a simple form,
like sucrose or fructose--a molecule of just one or two of those six-sided sugar rings discussed above.
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These simple sugars are the simplest forms of carbohydrates, and it takes very little effort for our bodies to convert simple sugars like these into glucose, so they are absorbed extremely quickly into our blood stream. So when you eat or drink these super-sweet foods, your blood sugar goes up very quickly. That's not good for diabetes.
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Starch
A more complex form of carbohydrate is starch. Starches like bread,
rice, pasta, and potatoes, are really just long strings of glucose
molecules. The strings range in size from 1 to 100 microns
(millionths of a meter). To put this into context, the
human eye can see about 40 microns in size,
and a human hair is about 50 microns
in width.
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Starches are made up of chains of
glucose. These molecules may be
very long, ranging from a couple
thousand to 200,000 glucose units
long. The ratio will vary based on
the specific starch, but about 20%
of starch is composed of long,
unbranched, single-stranded
chains of glucose (as seen in
the structure below). This is
known as amylose.
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The majority of starch, however, approximately 80%, is composed of highly-branched chains of glucose known as amylopectin, as seen in the structure below.
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The words "amylose" and "amylopectin"
are derived from the Greek word
"amylon" which refers to a finely-
ground grain or "meal." "Myl "
is the origin of the"meal" in
cornmeal or oatmeal, and
it is the origin of the
word "mill," where
a grain is ground
into a powdery
meal.
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"Pectin" originates
in the Greek "Pektos,"
meaning "congealed," as
amylopectin does not dissolve
and remains solid when exposed to
water.
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When you see the structures of starch, you can probably see what happens when they are digested. Enzymes in our body cut up these strings of starch into very large numbers of glucose molecules. This raises your blood sugar level. Often times, as with amylose (the single, unbranched string of glucose), this occurs very quickly. In fact, the first enzyme that dissolves carbohydrates is alpha-amylase, which is found in your saliva. (The ending "-ase" refers to an enzyme, so the name amylase refers to an enzyme that breaks down amylose.) In any event, the take home point is that simple carbohydrates are so easy for your body to digest--you're already beginning to digest them before you even swallow.
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However, not all carbohydrates are digested at the same speed. The more numerous and complicated the strings of glucose (complex carbohydrates) the more time it takes the body to break apart the units of glucose. Because these starches are a bit slower to digest, and raise blood sugar more
slowly. But they still raise your blood sugar, especially the worse
your diabetes.
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Foods are given a number based on the speed with which they
cause blood sugar to spike upwards. This is called the glycemic
index.
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So what happens to the glucose next?
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The pancreas, an organ just beneath the stomach, monitors
blood glucose levels closely. In response to the elevated
sugar in our blood, it sends out a hormone called insulin.
Insulin travels through the bloodstream to help direct the
glucose into our cells.
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Once inside a cell, the glucose can be used immediately,
or it can be put into storage in a form known as glycogen.
(Glycogen looks a lot like amylopectin, the multi-branched
carbohydrate.)
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As the glucose enters our cells, the amount of glucose in our
bloodstream goes down, and the pancreas cuts back on the
insulin it sends out.
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How does our body turn sugar into energy?
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Inside each cell, we have tiny organs called mitochondria. Most cells have hundreds of mitochondria; some have thousands. (Red blood cells, which carry oxygen through the blood, are unique in that they have no mitochondria.)
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Mitochondria take the glucose and convert it into energy through a process known as the Krebs Cycle. The Krebs Cycle requires oxygen to function, as oxygen absorbs the electrons the Krebs cycle produces. (This is why we need to breathe. We need oxygen to go to each cell and absorb extra electrons. If we didn't breathe in oxygen, the electrons produced by energy production in the mitochondria would build up, with nowhere to go. The Krebs Cycle would come to a halt, we could not produce any energy to carry out life functions, and we would die.)
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So what happens to sugar if you have diabetes?
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If you produce no insulin (Type 1) or don't process it properly (Type 2), the glucose is not brought to your cells. Instead, the glucose builds up in your blood. This is known as hyperglycemia.
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Your body tries to get rid of the extra sugar through the urine. So urine production rises, and you lose fluid in the process. This explains the increased frequency of urination with diabetes. It also explains why diabetics often feel thirsty, because they are urinating away the body's water while trying to get rid of the sugar in the blood.
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Because the mitochondria in the patient's cells have no glucose to use to create energy, the patient may feel weak, shaky, and irritable. And as the patient cannot process the sugar being ingested, he may be hungry, yet lose weight.
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How does diabetes lead to foot ulcers?
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The blood in our body flows to all our tissues. This includes nerves. When the blood sugar is high, more glucose enters the nerves. Inside the nerve, the glucose is converted into a different sugar, and it gets stuck there. Even when the blood sugar returns to normal, the increased sugar concentration in the nerve tends to remain. This increased sugar content inside the nerve draws fluid into the nerve cell through a process called osmosis.
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The increased water content in the nerves causes the nerve to function poorly. This is called neuropathy. Neuropathy can lead to a variety of neurological effects, including an inability to feel pain. It is this, the loss of the nerve's ability to feel pain, that leads to foot ulcers. We have a page with more on neuropathy here, along with some of the effects it has on our body here.
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Cell Nucleus
Mitochondria
A Short Side Commentary on Mitochondria
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1. We mentioned earlier that most cells have hundreds ore even thousands of mitochondria. But red blood cells have none. The reason for this is that if the red blood cells had mitochondria, the oxygen they carry would absorb the electrons produced in the red blood cells' Krebs Cycle, and they wouldn't be able to absorb electrons produced by other more distant cells. So we want the red blood cells to serve simply as transport vehicles.
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2. Mitochondria have their own DNA separate from the DNA in the nucleus of our cells. And unlike the DNA in the nucleus, which you inherit from both your mother and father, mitochondrial DNA is inherited exclusively from your mother. And your mother received her mitochondrial DNA from her mother.
So your mitochondrial DNA came from your mother's mother's mother's mother's mother. (There's an equivalent for men. Men receive their Y-chromosome from their father's father's father's father's father.)
The DNA in the nucleus of our cells mixes every generation, with each parent contributing 50% of the DNA. So you have 50% of your nuclear DNA from your father. But six generations later, there is less than 1% of his DNA left.
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This is not true for your mitochondrial DNA. It can change very slowly over time because of genetic mutations, but overall it is quite consistent over dozens and dozens of generations. And because of this stability, mitochondrial DNA can be taken from different population groups to examine how closely related different those populations are. And it can be used to study the migration patterns of our ancestors over thousands of years.
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2. Mitochondrial DNA shares many characteristics with bacterial DNA, and it's believed that back in the age where our ancestors were single-celled organisms, one once tried to ingest a mitochondrion (the singular for the plural mitochondria).
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However, our cell was unable to digest the tough, double membrane of the mitochondrion, and the cell couldn't get rid of the mitochondrion either. Instead, we developed a symbiotic relationship, where the mitochondrion produced all the cell's energy, and our cell carries out nearly all the other cellular functions. This huge increase in energy produced an advantage for
the cells with the mitochondria, and they was able to thrive and out-compete cells with less energy production.
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3. Irrespective of its origin, mitochondria produce all the energy large, multi-cellular organisms need to function. Without that energy, we would cease to be. We owe our very existence to mitochondria.
Above is a photo of a
mitochondrion from an
electron microscope.
"Mitochondria seem to be able to exist, in the form of free-living bacteria, without our help. But without them, we die in a matter of seconds."
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Lifetide: a Biology of the Unconscious (1979)
Above is a photo of multiple skin cells as seen with a microscope, We've highlighted the border of one cell with the arrows. The nucleus of the cell is indicated by the white arrow.
Above we see a nerve cell under higher power magnification. The nucleus is stained purple. The mitochondria, over 100 of which are visible in this slide, have been stained light blue. This gives an indication of the relative size and number of mitochondria.
Glucose Molecule
Pancreas
Sucrose (table sugar) Fructose
Nucleus
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This page written by Dr. S A Schumacher
Podiatric Surgeon
Surrey, British Columbia Canada
All clinical photographs owned and provided
by Dr. S A Schumacher. They may be reproduced
for educational purposes with attribution to:
Dr. S A Schumacher, Surrey, BC Canada