Is Obesity an Infectious Disease? Adenovirus and its link to obesity Alecia Sturgill April 18, 2008 Advisor: Dr. Bill Grimes.

Is Obesity an Infectious Disease?

Adenovirus and its link to obesity

Alecia Sturgill

April 18, 2008

Advisor: Dr. Bill Grimes

Introduction Why is it easy for some people to lose

weight and difficult for others? Caloric intake Physical activity Genetic predisposition Socioeconomic status Some other unknown factors

Background What does overweight and obesity mean?

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?

Some associated diseases with obesity are: Type II Diabetes Hypertension Coronary Heart Disease Stroke Dyslipidemia Osteoarthritis

Other Negative Effects Associated with Obesity

Economic issues Account for 9.1 percent of the national medical

expenditure nearly 92.6 billion dollars

Psychological issue Discrimination in work and school

Epidemiology of Obesity WHO has proclaimed a global epidemic of

obesity estimates 300 million worldwide 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 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? 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 Nikhil V. Dhurandhar, previously of Wayne State University

and currently with Pennington Biomedical Research Center 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 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 Virus getting most

attention Medium-sized,

nonenveloped icosahedral virus containing double-stranded DNA.

49 immunologically distinct types that can cause human infections.

Adenovirus 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 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

Can be diagnosed in multiple ways Polymerase chain reaction assays (PCR) Antigen detection Virus isolation Serology

Treatment and prevention of an adenovirus infection

Treatment Since most are mild, they usually require no treatment Treat complications of infections

Prevention Hygiene practices washing hands, cleaner drinking

water, better medical practice, etc. Vaccine

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 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)

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) 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) 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)

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.

Would it be logical to do viral antibody tests on obese individuals with low levels of cholesterol?

Summary Obesity is a global epidemic

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 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?

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 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 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!

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