Chapter 4 Homeostatic Mechanisms • MHR 123Type 1 Diabetes
Type 1 diabetes has also been called juvenile
diabetes. The cause of this disease is not well
understood, but evidence shows that Type 1
diabetes is an autoimmune disorder, in common
with lupus and some forms of arthritis. In this type
of disease, the body’s own immune system mounts
an attack on parts of the body. In the case of Type 1
diabetes, the immune system attacks the pancreas,
because it no longer recognizes certain cells of the
pancreas as being “self.” The immune system
functions by knowing the difference between “self”
and “non-self,” as you shall see in the next section.
The ability to detect “non-self” cells and other
materials allows the body to recognize and attack
infections and abnormal growths such as cancer. In
Type 1 diabetes, the immune system seems to
attack the insulin-producing beta cells without
warning. Some scientists postulate that a viral
infection of the beta cells may change them enough
to trigger an attack by the immune system.
Regardless, the body loses its ability to produce
insulin almost overnight.
Type 2 Diabetes
Type 2 is a more common form of diabetes, affecting
six percent of the population. It is also referred to
as adult onset diabetes, as it typically occurs in
adults over the age of 40. Ninety percent of
diabetics are Type 2. In these cases, while the
body produces insulin, it is either in insufficient
quantities or the body cells neither recognize nor
respond to the insulin. This form of diabetes is
often successfully treated by means of changes in
diet and exercise. However, patients may require
medication or even insulin shots to control
increased blood sugar levels. Both forms of
diabetes can cause rapid weight loss, blindness,
and/or circulatory disorders that may have serious
consequences.
Partial evidence of a genetic component to
diabetes lies in the fact that the disease occurs
more commonly in certain ethnic groups. It is
believed that over thousands of years, the people
in these groups developed very efficient metabolic
processes to deal with all too frequent occasions
when food was scarce. Consequently, their body
systems are thought to have adapted to move any
excess glucose rapidly out of the bloodstream and
into cells. The relatively recent shift for these
people to a diet of processed foods high in sugars
overloads the systems of some of their members,
leaving them susceptible to a diabetic-type disorder.What Causes Diabetes
As previously mentioned, the actual cause(s) of
diabetes are not well understood. Some researchers
believe the destruction of beta cells associated with
Type 1 diabetes is consistent with a viral infection,
while others link the disease to specific genes.
Type 2 diabetes may have a genetic link, but it is
also affected by body chemistry related to age,
activity level, and obesity. Both forms of diabetes
illustrate that homeostatic mechanisms of the body
are influenced by internal as well as external
factors. Many North Americans consume a diet
containing high levels of sugar while maintaining a
relatively sedentary lifestyle. For these people, the
high level of blood sugar created by their lifestyle
may affect the homeostatic mechanisms meant to
keep blood sugar stable. For other people, the
problems may be largely genetic. A person’s genes
influence his or her metabolism — the rate at
which food is broken down, and the rate at which
cells absorb materials such as sugars. Genetics may
also determine the body’s normal blood sugarhttp://www.mcgrawhill.ca/links/biology12
Clinical trials involve volunteers participating in controlled
studies designed to evaluate the effectiveness and safety of
new types of pharmaceutical products, diagnostic procedures,
and treatment “protocols.”
To access a discussion of a clinical trial involving a new
procedure for taking insulin orally rather than by needle, go
to the web site above, and click on Web Links. Compare and
contrast the various methods of taking insulin. How does a
person with diabetes qualify for this clinical trial? Describe the
role of a patient who participates in the trial. Discuss the
potential risks and benefits for patients taking part in the trial.
Compare the goals and procedures of this clinical trial with
others described in the reference web sites.WEB LINK
Is Type 2 diabetes genetic? Consider the following
statistics.- The siblings of a person with Type 2 diabetes have almost
a 40 percent chance of developing Type 2 diabetes or
glucose intolerance (near-diabetes). - The children of a person with Type 2 diabetes have a
33 percent chance of developing Type 2 diabetes or
glucose intolerance. - The identical twin of a person with Type 2 diabetes has a
70 to 80 percent chance of developing Type 2 diabetes.