Download Is Obesity an Infectious Disease?

Is Obesity an
Infectious Disease?
Adenovirus and its link to obesity
Alecia Sturgill
April 18, 2008
Advisor: Dr. Bill Grimes
Introduction
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Why is it easy for some people to lose
weight and difficult for others?
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Caloric intake
Physical activity
Genetic predisposition
Socioeconomic status
Some other unknown factors
Background
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What does overweight and obesity mean?
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CDC states, ranges of weight that are greater
than what is considered healthy for a given
height.
BMI (Body Mass Index)  25-29.9 = overweight,
30+ = obese
Why is it important to determine the
causes of obesity?
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Some associated diseases with obesity
are:
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Type II Diabetes
Hypertension
Coronary Heart Disease
Stroke
Dyslipidemia
Osteoarthritis
Other Negative Effects Associated
with Obesity
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Economic issues
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Account for 9.1 percent of the national medical
expenditure nearly 92.6 billion dollars
Psychological issue
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Discrimination in work and school
Epidemiology of Obesity
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WHO has proclaimed a global epidemic of
obesity estimates 300 million worldwide
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Obesity has doubled in adults and tripled in
children in the last thirty years
Since the 1970s, prevalence has sharply
increased from 15% to 32.9% in a 2003-2004
survey
NHANES survey (combined overweight &
obesity) went from 46% in 1976-1980 to 61% in
1999
Obesity: A Global Epidemic
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Dr. Leah Whigham, stated that this dramatic increase has
not been found in an other chronic disease in the past and
has only been witnessed in the spread of an infectious
disease.
Is obesity actually being caused by an infectious process?
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Could a virus, bacterium, etc. be interrupting the regulatory
controls of our bodies and causing people to gain weight?
Many were skeptical at first but this theory has recently been
given more credibility

Ex) Recent discovery of bacterium Helicobacter pylori as an
etiologic agent in peptic ulcer disease.
Research
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Nikhil V. Dhurandhar, previously of Wayne State University
and currently with Pennington Biomedical Research Center
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Six viruses and a scrapie agent that has been shown to produce
obesity in animals
Two viruses, an avian adenovirus and a human adenovirus
(Adenovirus-36) have been linked to human obesity.
Questions about the Virus
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How is the virus transmitted?
Does the virus act alone or does it require other
factors to increase obesity?
How does the virus act on the body to increase
obesity?
Could there be other agents that may act in a
similar way?
What can be done about this problem in the
realm of screening and prevention?
Adenovirus
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Virus getting most
attention
Medium-sized,
nonenveloped
icosahedral virus
containing doublestranded DNA.
49 immunologically
distinct types that can
cause human infections.
Adenovirus
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Usually does not cause severe illnesses
Most commonly cause respiratory illnesses,
but can cause gastroenteritis, conjunctivitis,
rashes, and cystitis
Severity depends on serotype and state of
patient’s immune system
Adenovirus-36 (Ad-36) most often causes
the common cold and pink eye
Adenovirus
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Transmission varies slightly by serotype being
from fecal-oral, direct-contact and water-borne
transmission
Severity can be dependent on transmission
Some adenoviruses are capable of existing in
tonsils, adenoids and intestines of hosts without
symptoms
Some are endemic to certain parts of the world
Diagnosis of an adenovirus infection
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Can be diagnosed in multiple ways
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Polymerase chain reaction assays (PCR)
Antigen detection
Virus isolation
Serology
Treatment and prevention of an
adenovirus infection
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Treatment
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Since most are mild, they usually require no treatment
Treat complications of infections
Prevention
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Hygiene practices  washing hands, cleaner drinking
water, better medical practice, etc.
Vaccine
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Exists but only given to the military
Live, oral vaccine that is attenuated in the intestine
Known to have an oncogenic potential
Review of Literature
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Dhurandhar’s first attempt (Dhurandhar, 2000)
Goal of study is to see if animals inoculated with Ad-36
would have increased adipose tissue
The results of this study showed those inoculated with
Ad-36 had increased adipose tissue with contradictory
low serum triglycerides and cholesterol, this did not
occur in those inoculated with the avian adenovirus
This allowed Dhurandhar to believe that a virus could be
involved and more research must be done
Dhurandhar’s next attempt
(Dhurandhar 2001)
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Goal was to determine if Ad-36 could be
transmitted from infected chickens sharing
the same cage and if the virus could be
transmitted through blood
This was found to be true in both cases. The
transmission of the Ad-36 induced adiposity
should raise concerns in the transmission in
humans
Further research (Dhurandhar, 2002)
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He decided to study nonhuman primates to investigate the
adiposity-promoting potential of Ad-36
In the first study he observed spontaneously occurring Ad-36
antibodies in male rhesus monkeys and an association of
positive antibody status with weight gain and decreased
plasma cholesterol.
The next experiment showed that marmoset monkeys had a
threefold body weight gain, an increase in body fat and lower
serum cholesterol compared to control groups
More Research (Vangipuram, 2004)
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Next experiment determined that Ad-36
enhances differentiation of preadipocytes
Also, Ad-36 increased the number of
differentiated adipocytes, GPDH enzyme levels,
and the total cellular lipid content.
This may be a contributing mechanism in its
adipogenic effect. It also proved that this is not a
common factor in all adenoviruses since the
same result was not found in Ad-2
More research (Atkinson, 2005)
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The result of another study showed a significant
association of obesity and a positive Ad-36 status. It was
found that 30% of obese participants were positive for
Ad-36 antibodies and 11% in the non obese.
There was also lower serum cholesterol and triglyceride
levels in Ad-36 antibody positive subjects. There was no
association in the other adenoviruses and obesity.
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Would it be logical to do viral antibody tests on obese individuals with low levels of
cholesterol?
Summary
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Obesity is a global epidemic
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It contributes to morbidity and mortality by its association with other chronic diseases
It is essential that all the etiologic agents associated with obesity is
identified
It is now evident that obesity being partially infectious should not be
disregarded
It is known that Ad-36 induces adiposity by increasing body fat,
enhancing differentiation of preadipocytes, lowering serum lipids
and triglycerides, increasing leptin production, and altering glucose
metabolism
Other infectious agents needs to be considered
More research needs to be done so that vaccines and screening
tests can be utilized to combat the problem
Conclusion
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It is important that this is not used as an excuse for being
overweight
Other causes of obesity should not be forgotten
What measures will be taken if this theory is fully accepted?
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Vaccines cover all serotypes known to cause obesity
Anti-viral medications Cidofovir prevents adiposity in mice cells
Screening tests expensive but may be worth it
New biotech company that developed an antibody screening test
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Criticized by peers because there is not very effective treatment for an
adenovirus infection
However, if a normal weight individual received a positive antibody test
they would know that they are at risk and could possibly change their
lifestyle
Conclusion
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If this theory does not follow through, it will
still raise awareness that infectious agents
should be considered as the causative
agents in other disease processes
No matter what the solution (vaccines,
screening tests, health & fitness programs,
etc.) the problem of obesity needs to be
conquered!
References
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adenovirus-36 is associated with increased body weight and paradoxical reduction of serum lipids.
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Center of Disease Control and Prevention, Adenoviruses. January 21, 2005, Available at:
http://www.cdc.gov/Ncidod/dvrd/revb/respiratory/eadfeat.htm, Accessed on December 21, 2007.
Center of Disease Control and Prevention, Obesity and Overweight. November 17, 2007, Available at
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Christakis, N.A. and J. H. Fowler. The spread of obesity in a large social network over 32 years. The New
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