Tufts University biologists link Huntington's disease to health benefits in young

September 25, 2007

MEDFORD/SOMERVILLE, Mass. -- For years researchers in neurology have believed that people with Huntington's disease have more children than the general population because of behavioral changes associated with the disease that lead to sexual promiscuity. In a new Tufts University study, three biologists have challenged that notion by suggesting that people with Huntington's have more children because they are healthier - not more promiscuous - during their peak reproductive years. "A Darwinian Approach to Huntington's Disease: Subtle Health Benefits of a Neurological Disorder" is published in the August 8, 2007 online issue of the journal Medical Hypothesis and will soon appear in print.

"Huntington's is a disease that may have beneficial health effects on people early in life, but dire health costs later when symptoms express themselves," said Philip T. Starks, assistant professor of biology in the School of Arts and Sciences at Tufts. "Ironically, these early health benefits may contribute to an increased prevalence of the disease." Huntington's disease is a genetic disease involving degeneration of the central nervous system (CNS), leading to uncontrolled muscle movements, emotional instability and dementia. Folk musician and songwriter Woody Guthrie died from complications of the disease in 1967.

Link Between Huntington's and Immune System

Along with Dr. Starks, former Tufts undergraduate Benjamin R. Eskenazi and present doctoral student Noah S. Wilson-Rich reviewed 75 published studies in forming their hypothesis. They focused on the tumor suppressor protein p53, which maintains normal cell growth and is found at levels above normal in Huntington's sufferers. At these elevated levels, p53 appears to increase resistance to cancer by causing cancerous cells to destroy themselves. Previous research has linked increased production of p53 to the mutant form of the Huntington (htt) protein that is found in the CNS of individuals with the disease. In this new hypothesis, the Tufts researchers suggest that p53 not only reduces the incidence of cancer in those affected by Huntington's disease but by improving overall health may also contribute to increased offspring production.

The Tufts team analyzed the often-noted fertility gap between people who have Huntington's and those who do not. Studies comparing family members indicated that individuals with the disease had between 1.14 and 1.34 children for every child born to an unaffected sibling. In explaining this difference, previous researchers have theorized that psychological deterioration and difficulty in discriminating between right and wrong - both symptoms associated with Huntington's - are reasons for promiscuous behavior in people who had the disease. But Eskenazi, Wilson-Rich and Starks observed that such behavior takes place later in life - not during peak reproductive age. They noted that the onset of Huntington's disease occurs, on average, at 41.5 years of age.

In their alternative hypothesis the Tufts researchers suggested that individuals affected with Huntington's have better health earlier in life at the time when their fertility is highest. "We've raised the possibility that the high birth rates are a result of better health," explained Starks. "We know that healthy people have more offspring than those who are sick."

Starks and his team suggested that one key factor behind these health benefits may be p53, and pointed to a 1999 study by doctors at the Danish Huntington Disease Registry at the University of Copenhagen that found lower age-adjusted cancer rates for individuals affected by Huntington's. "Research has shown that individuals with Huntington's produce higher levels of cancer-suppressing p53, and we hypothesize that they may also reap the health benefits associated with a generally more vigilant immune system," said Starks. "These individuals also suffer from the negative impacts of heightened immune function, as they are more likely than those without Huntington's to suffer from autoimmune diseases."

Starks said that the hypothesis pointing to health benefits of people with Huntington's requires significant additional research. "This is a hypothesis that still needs strong support through more studies," he said.

Marriage of Evolutionary Biology and Medicine

Starks, whose research areas include behavior and evolution in a wide range of organisms, noted that Huntington's disease may be an example of antagonistic pleiotropy, in which one gene creates multiple and conflicting effects. Another example of this phenomenon includes a gene that appears to decrease the incidence of Alzheimer's disease while increasing the chance of elevated lipids in the blood. The convergence of evolutionary biology and medicine can reap many benefits, he believes. "This marriage has already shed light on phenomena such as fever and morning sickness," he noted. Huntington's disease may be one more beneficiary of this synergy.
-end-
Tufts University, located on three Massachusetts campuses in Boston, Medford/Somerville, and Grafton, and in Talloires, France, is recognized among the Premier research universities in the United States. Tufts enjoys a global reputation for academic excellence and for the preparation of students as leaders in a wide range of professions. A growing number of innovative teaching and research initiatives span all Tufts campuses, and collaboration among the faculty and students in the undergraduate, graduate and professional programs across the university's schools is widely encouraged.

Tufts University

Related Evolutionary Biology Articles from Brightsurf:

The propagation of admixture-derived evolutionary potential
Adaptive radiation - the rapid evolution of many new species from a single ancestor - is a major focus in evolutionary biology.

Genome duplications as evolutionary adaptation strategy
Genome duplications play a major role in the development of forms and structures of plant organisms and their changes across long periods of evolution.

Evolutionary theory of economic decisions
When survival over generations is the end game, researchers say it makes sense to undervalue long shots that could be profitable and overestimate the likelihood of rare bad outcomes.

Evolutionary assimilation of foreign DNA in a new host
Bioengineers at the University of California San Diego used genetic engineering and laboratory evolution to test the functionality of DNA placed into a new species and study how it can mutate to become functional if given sufficient evolutionary time.

The evolutionary puzzle of the mammalian ear
How could the tiny parts of the ear adapt independently to the diverse functional and environmental regimes encountered in mammals?

Bees point to new evolutionary answers
Evolutionary biology aims to explain how new species arise and evolve to occupy myriad niches -- but it is not a singular or simplistic story.

New evolutionary insights into the early development of songbirds
An international team led by Alexander Suh at Uppsala University has sequenced a chromosome in zebra finches called the germline-restricted chromosome (GRC).

Quantitative biology opens trail to ecological exploration, evolutionary prediction
Back-to-back papers published in Nature uncover surprising new findings on bacterial chemotaxis -- the movement of bacterial cells in response to chemical stimuli -- one of the most studied areas of molecular biology.

Evolutionary discovery to rewrite textbooks
Scientists at The University of Queensland have upended biologists' century-old understanding of the evolutionary history of animals.

Godzilla is back and he's bigger than ever: The evolutionary biology of the monster
Godzilla first made his debut in 1954 as a 50-meter tall metaphor for indiscriminate destruction, particularly US hydrogen-bomb testing in the Marshall Islands, which, in the film, destroyed Godzilla's deep-sea ecosystem.

Read More: Evolutionary Biology News and Evolutionary Biology Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.