I have patients who are obese or have diabetes with strongly positive
family histories. I know there is a genetic basis for some of this. Is
gene testing suitable for these patients and which tests should I
order (if any)?

Diagnosing obesity or diabetes is not difficult through traditional
methods. Genetic testing is expensive, and no definitive human
"obesity gene" or "diabetes gene" has yet been identified, as far as I
know.

I understand your comment, but how about etiologic diagnoses so that I
can find out a) if there is indeed a familial basis for it and b) so I
can use the information with other (younger or even unborn) family
members?

Unless a clear-cut relationship between a certain genetic marker and a
disease has been demonstrated, I can't see how genetic testing would
be useful as a routine diagnostic tool.

Well, if one of your patients has Maturity Onset Diabetes of the Young
(an autosomal dominant disease), other family members are at risk and
would benefit from early warning and monitoring and management. I know
of at least 5 genes involved in MODY, I was looking for more
information about other genes for more common types of type II
diabetes and for obesity.

zakthehack,

The human obesity gene is mapped on chromosome 7. Leptin is a hormone
that is released to the brain from fat cells telling us when to stop
eating(reduce craving etc..)
When genetic mutation occurs among chromosome 7 the body's ability to
produce Leptin becomes hindered, in return the patient eating more and
more. For a complete updated Obesity Gene Map you can refer to The
Lousiana State University Biomedical Research Center:
http://obesitygene.pbrc.edu/ .

You would need to do DNA testing to compare your obese patients
chromosome 7 to a normal healthy patients chromosome 7, and trace back
several generations if possible to get any answers.

Diabetes is alot more difficult to understand when using genetics.
Diabetes Type 1 is known as a complex trait, meaning it involves
mutations of several genes which contribute to the illness. The
Insulin-dependent Diabetes Mellitus locus on chromosome 6 has been
known to be one of these genes. Roughly 10 loci on have been found
that seem susceptable to Type 1 Diabetes some of which include the
locus IDDM2 on chromosome 11, the gene for glucokinase on chromosome
7(studies have shown many links towards obesity and diabetes as you
must already know), and more so the HLA (human leukocyte antigen)
region of a chromosome.

Completing DNA testing is very expensive but it provides alot of
answers to many people and may bring closure to alot of pain your
patients may go though. Starting in those areas would definitely yield
some answers, but also make sure to look into links between patiens
who are both obese and diabetic.

Try this lab. You will have to contact them and explain exactly what
you want, but they test for several types of diabetes gene markers.
This page lists several:

http://www.genetests.org/servlet/access?id=8888891&testtype=both&testtype=both&qry=diabetes&submit=Search&db=genetests&fcn=b&res=&key=xz5vs9DX-gedM&testtype=both&type=e&ls=c&grp=b&submit=Search&res=nous&res=nointl

This page will let you search by disease and state:

http://www.genetests.org/servlet/access?id=8888891&key=xz5vs9DX-gedM&fcn=y&fw=38qU&filename=/labsearch/searchdztest.html

This article on the SUMO-4 gene may be of interest.
http://www.eurekalert.org/pub_releases/2004-07/bcom-nga072204.php

Be prepared, as Pinkfreud is correct that this is rather expensive
testing, and will likely require a doctor's order, and/or be deemed
medically necessary.

For Type 2:

Beta3-Adrenergic Receptor Gene - Mutation: TRP64ARG  (most common!)

The genetics of Type 2 diabetes is complicated, with many different
genes influencing a person's risk. Because of this array of genes,
Type 2 diabetes is not inherited in a clearly dominant or recessive
manner. Instead, a person may have one gene that increases their risk
and other genes that decrease risk. Together, these genes, along with
environmental factors, determine a person's overall risk for
developing diabetes. With so many variables to consider, the medical
community is a long way from a genetic test for Type 2 diabetes.

Using genetic markers for diagnostic purposes can be very misleading,
and is, in my view, largely unnecessary, except in cases such as
Huntington's Disease, in which testing can give a relatively certain
yea or nay on the presence of a disease. The genetic factors related
to diabetes and obesity are nebulous and poorly understood, and their
predictive power is doubtful.

Here's an interesting article on the subject of routine genetic testing:

http://www.newmobility.com/review_article.cfm?id=346&action=browse

pinkfreud, I agree with you on the basis that diabetic dna testing for
TYPE 2 diabetes is nebulous, however that article you posted a link
to, was written in March 2001. In "genetic years" that is ancient. The
Human Genome Project completed the human genome sequence on April
2003. Many advances have been made since then let alone March 2001. It
can be compared to the technology of a computer built in 2001 as
compared to one built today, three years later. Again, I hope all the
comments on this topic have been helpful to zakthehak.

Is there now a genetic marker for type 2 diabetes that provides
predictive certainty? If so, I am not aware of this.

No there isnt any specific marker for Type 2 yet, that is why I said I
agreed with you about it being nebulous. Specifically all so far from
what I know is the Beta3-Adrenergic Receptor Gene under Mutation:
TRP64ARG.
Got the following from www.genetichealth.com (Has alot more
information on this kind of topic) :

The Beta3-adrenergic receptor gene makes a protein in fat cells that
is involved in determining how much fuel your body burns when you are
resting. A mutation in this gene slows down how quickly a person burns
fat ? increasing their tendency to be obese. One specific mutation in
this gene, called TRP64ARG, is almost four times more common in Pima
Indians than in people of European descent, and is one and a half
times more common in people of African or Mexican descent. The
prevalence of the TRP64ARG gene mutation in these populations probably
accounts at least in part for why these ethnic groups have a higher
rate of Type 2 diabetes.

It is my belief that it's not good medicine to order expensive genetic
testing in order to determine that a patient's relatives might be at
risk for diabetes or obesity. Both diabetes and obesity are
recognizable by their symptoms. Even if it were possible to determine,
years in advance of the appearance of symptoms, that a person might be
likely to develop either condition, how would this help? Such a person
would be told to eat a healthful diet and exercise regularly. This is
advice that applies to virtually all patients, whether or not they
have a family history of diabetes or obesity.

I believe susk-ga has given me the answer. How do we finish this
transaction so that susk-ga gets the $10? According to Google these
are all comments but not answers and yet, I feel that I have had my
question answered.

-Zak

Susk-ga is not a Google Answers Researcher, and thus cannot receive
compensation for his or her comments. One of the most interesting
things about Google Answers is that sometimes you may receive useful
information free of charge.

Well, in that case, susk-ga, thanks a lot for all the information.

-Zak

Zak,

If you've received all the information you need, you may want to
cancel the question (use the grey button in the upper right of the
page that says 'CANCEL QUESTION'). This will take the question off the
Researchers' queue of questions needing attention, and you'll pay only
the fifty-cent listing fee.