Monthly Archives: March 2014

A deeper look at Chagas disease

When we read about vector-borne disease, Chagas disease was mentioned. I’m not super informed about Chagas, but I do know some people studying the disease and knowledge of the disease among health providers. 
There are essentially two things that I want to convey through this post: (1) Chagas disease is a parasitic infection involving Trypanosoma cruzi and is endemic to Latin American countries but is incredibly influenced by social, cultural and economic factors that allow for movement of disease-affected areas and (2) because of the different influences, healthcare providers must be more cognizant of such “neglected” diseases because human migration and overall international interaction can cause serious public health burdens.
This article outlines the different qualitative influences on Chagas and how they affect transmission. The study performed an overall review of what qualitative research is out there on Chagas (in-depth interviews, focus groups, ethnography, participant observation and more). This article discusses the the following overall themes among the studies: socio-structural determinants of Chagas disease; health practices; biomedical conceptions of Chagas disease; patient’s experience; and institutional strategies adopted. 
I thought this article was informative because scientists often look to quantitative data as a source of answers, but so much of health and medicine is cultural and necessitates analysis of qualitative data. 
This study specifically looks at international migration from Chagas-endemic countries and how that has allowed for spread of the disease into non-endemic areas. I think this line summarizes the overall conclusion: “Non endemic countries receiving immigrants from the endemic ones should develop policies to protect organ recipients from T. cruzi infection, prevent tainting the blood supply with T. cruzi, and implement secondary prevention of congenital Chagas disease.” Here, it’s important to realize that there is movement of this disease across regions and countries. In other words, when we said that Chagas is a Latin American disease in class, we weren’t completely true. 
I don’t mean to say that we were entirely wrong, just that with our modern world, that kind of statement isn’t accurate anymore. This relates to something we’ve been talking about throughout the semester – how our understanding of disease influences medical education. There’s a lot of research out there about health providers’ knowledge on Chagas and other neglected parasitic infections, and from what I’ve read and understood, there’s a gap in that knowledge. It comes to the point where individuals with Chagas are misdiagnosed and sent home – to further spread the disease. Here’s an example article I found. 

Diabetes and Evolution

Although obesity is an unfavorable trait, there is evidence that in the past storing fat was quite beneficial. The body was apt to store fat to prepare for long periods of famine in our ancient history. This thrifty gene hypothesis was originally proposed by James Neel. Obesity leads to many health complications, one of the most common being Diabetes.

There are a high percentage of Native American populations that have Type 2 Diabetes. Unnatural Causes: Bad Sugar, a documentary,  delves into the many ways that other factors have contributed to the genetic predisposition of Diabetes in the Pima Indian population of Arizona. Many of these factors happen to be political/economic issues. For instances, the Coolage dam diverted water from the Gila River (major water source in the Pima community) away from the reservation.  The Pima Indians were left with little water resources for their crops and for survival, making them one of the poorest populations in America at the time. This severely affected the Pima economically and culturally. They had to learn to survive without water and adequate food.  Many of the Pima died from starvation during this time of famine. Within 30 years of building the dam there were more than 500 cases of diabetes among the Pima Indians. This supports the thrifty genotype hypothesis. Their bodies were used to not receiving adequate nutrition so the body evolved to hold onto more fat than usual for survival. After a while the government provided food subsidies, but they were not healthy options. The Pima community did not have markets where fresh produce was abundant so they had to rely on processed food that had low nutritional value, provided by the American governemtn. This resulted in even higher rates of diabetes in the population today.

I think that the story of the Pima community in Arizona is a good example of our class discussion on how the human genome evolves simultaneously with our environment and culture.  There is evidence that many minority groups, such as African Americans, that have experienced extreme hard ship in history have high rates of diabetes as well.

A Second Look at Depression

The evolution of mental illness has always interested me, after our discussion in class about Schizophrenia, I became interested in the evolution of depression. Unlike Schizophrenia, depression is a common mental disorder, it is estimated to affect 121 million people all over the world and the number of people who have been diagnosed is increasing at a 20% rate per year. This phenomenon puzzles evolutionary biologists and psychiatrists because the alleles that are responsible for depression should be selected against over time according to the four postulates of evolution. This paradox is examined in this NYTimes article. 

The proximate cause of depression is rumination, which means that people fixate on their flaws and problems, and extending their negative moods, rumination decrease a person’s functionality in daily life and it is considered useless, waste of mental energy. Rumination is associated with ventrolateral prefrontal cortex (VLPFC), which is located a few inches behind the forehead. Interestingly, VLPFC is also responsible for intense focus which is necessary to produce meaningful work. Therefore, it is hypothesized that depression has the benefit to allow the individual to have an increased brain activity that normal people cannot achieve. In another word, depression is an extreme end at the spectrum of ordinary thought process, and the inability to engage in pleasant activities help the depressed person focus better on their work

The question is, does depression and sadness indeed make people more productive for being more attentive? Psychiatrists and researchers has argued that many patients who have suffered from depression have a hard time performing daily functions such as bathe or eat, not to mention work and solve problems. These counter arguments suggest that the benefit theory of depression is a stretch.

Another school of psychiatrists suggest that depression could be a warning sign like chronic pain. Only by seeing a therapists and walk through the rumination process, can patients who suffer from depression find out the fundamental cause of depression.

This leads to the conclusion from the author which I think perfectly describes the relationship between emotions and consciousness, “ This is the paradox of evolution: even if our pain is useful, the urge to escape from the pain remains the most powerful instinct of all.”

Synopsis (Greenspan)

The Greenspan paper sheds light on a topic that we have been focusing on since the beginning of class: how has modern medicine changed the evolution of human diseases? This author suggests that the development of modern medical technologies and vaccines has enabled human with rare diseases to live beyond reproductive age and pass on their genes; also, the improvement of living conditions has sustained tremendous population growth that gives rise to a larger gene pool that allows for possibilities of new mutations.Essentially, the cultural evolution has relaxed natural selection on humans.

 By using the example of Cystic Fibrosis, the author provides evidence that survival rate for the once-lethal disease has dramatically increased over the years and patients with CF can easily live up to reproductive age. In addition, the author uses empirical evidence to support the idea that a small mutation could easily be magnified into deleterious conditions.

 The authors distinguishes between culture evolution, which is the development of medical care and public health interventions; and biological evolution, which is the traditionally defined “survive of the fittest”. I think it is important to note that culture evolution is unique to human, so it is difficult to fit cultural evolution into the frame of traditional evolution theories. Also, I think the author brings up a great point that “personalized medicine” might be more challenging than we have expected due to the expanding population size and the weakened elimination on deleterious alleles.

Have Farm Animals Evolved with Us?

At the very beginning of class, we read an article by Wang that talked about how dogs have evolved with human as they are domesticated early on in their evolutionary history. In a recent class, we also discussed the differences in nutrition content between the meat we consume today and meat we used to consume decades ago. I was wondering if farm animals have also evolved with us as the domestication of chicken, cows, and pigs have definitely changed their physiology over the years.

In a NYTimes article, author pointed out that animals that are raised in modern industrial farms are bred to produce the most amount of edible meat. For example, chickens are bred to have gigantic, disproportionate breast because human like to consume chicken breasts. It is a desirable trait for human as meat consumers, however, it is detrimental to chicken’s health because large breast in no way benefit chicken’s survival or reproduction in their natural habitant. Human have genetically changed the way animals are raised in industrial farms, as a result, chicken eat less while grow bigger. However, physiology is not the only thing that has changed in modern farm animal population. Due to the highly regulated farm industry, farm animals tend to become more and more homogenized and loaded with antibiotics, consequently, they are a lot more vulnerable to diseases compared to their wild counterparts. Tyson Foods, which is called “America’s meat factory” that monopolizes the production of chicken, is able to bring chicken’s retail price from $6.48 per pond to $1.57 per pound, as a result of the mass production.

I think this phenomenon is best summarized by the author’s comment that industrialized faring “privatizes gains but socializes the health and environmental cost”.

Are Antibiotics Making Us Obese?

In the Scientific America article we read for class: Swapping Germs: Should Fecal Transplants ecome Routine for Debilitating Diarrhea, we learned about the importance of maintaining a healthy population of microorganisms in our gut. In previous classes, we also talked about the increasing health threat created by the overuse of antibiotics: the emerging new generation of bacteria that are resistant to all existing antibiotics.

I came across this NYTimes article that discusses the correlation between antibiotics abuse, obesity and microbiome in human gut. Essentially, it was discovered in 1948 that antibiotics makes young animals pack on weight easily. Since then, antibiotics have been used unethically as superfood to produce cheap meat. Another favor that antibiotics did for mass produced farm animals is that, they are able to stay inside for their entire life because they can now resist the terrible living conditions in animal farms while packing on more meat. The questions is, can antibiotics do the same thing to us? Could the American obesity epidemic be the result of our high consumption of antibiotics from both meat products and prescription pills?Despite of ethical limitations, an experiment was done on a group of children from Guatemala, while a doctor in Florida conducted similar experiment on a group of mentally challenged children. And just like they have expected, the children indeed grow larger just like farm animals. Although the exact causation of the weight gain from antibiotics is unknown, it is hypothezed that antibiotics can change the population of microorganisms in the gut and therefore change the metabolism of nutrients. As more studies are done on this particular subject, the correlation between microorganism population and human’s health and growth becomes more clearer.

Examining the history of antibiotics abuse not only reveals the health complications, but also sheds light on related ethical issues. While terminating the use of antibiotics from our lives all together is not realistic, we can choose to purchase farm raised, antibiotic-free meat product and try to find alternatives to all-purpose antibiotics in our prescription drugs.

Down with the Human Race

In class we have discussed that it is imperative to our understanding of evolution and natural selection that no one species is more advanced than another. It is a fundamental principle that also leads to the understanding that as species evolve, it is not with the goal in mind of being a “perfect” or the best species on the planet. Instead, a species evolves to be as well adapted to its current environment as possible (and of course it is not doing that by conscious choice but by natural selection).

We all have a grasp on these concepts. What I did not know was that some have inflated these ideas to an extreme. According to this video (see link below) there is a growing population of people who believe that because humans are technically no “better” than any other species that we should depopulate for the sake of the life of all other species. These extremists argue that humans are a plague upon the Earth that are destroying the planet for all other organisms. They say this simply because of the fact that humans are no more advanced or superior than any other species.

The video goes on to articulate implications of this ideology. The one that stood out to me was the fact that if we legally equivocate animals to humans, then all of us would have to become vegetarians. Secondly, animals would be able to bring up lawsuits against humans for issues such as maltreatment (the animal of course would be unable to do this but one of these extremists would do so for them). The most extreme of the extremists would even argue that plants have rights, so we would have to stop consuming plants as well.

In my opinion, these extremist ideas are nothing short of insane. But I cannot deny that the concept these ideas are based on is actually 100% correct and is fundamental to understanding evolutionary medicine.


Hygiene Hypothesis – New Developments

Dr. Garcia’s presentation last class on host-parasite interaction of gut microbes touched on what is known as the hygiene hypothesis. The hygiene hypothesis is a very relevant and interesting topic in connection to evolutionary medicine because it takes into account the history of human exposure to microbes and how our immunoregulatory circuits developed in relation to the presence of microorganisms, especially with gut and skin flora. There is even evidence of evolved dependence to some of these microorganisms due to coevolution. With the changes brought about by technological modernization, the decreasing presence of microbes in our immediate environment has exacerbated systems of inflammation to cause a growing set of chronic autoimmune diseases to emerge. This connection is described in great detail in the book The Hygiene Hypothesis and Darwinian Medicine, edited by Graham A. W. Rook, who is a prominent name in this field of study.

An article in Science Daily from March 2012 titled “Getting the Dirt on Immunity: Scientists Show Evidence for Hygiene Hypothesis” details new supporting evidence for the theory provided by Brigham and Women’s Hospital about this modern predicament. The hospital’s study specifically provided an underlying biological mechanism explaining the hypothesis for the first time in its history, using “germ-free mice” as models. These mice, which were completely lacking in bacteria or any other microbes, were compared to mice living in normal microbial environments and were found to have exaggerated displays of inflammation due to hyperactivity of a unique class of T cells previously linked to disorders such as asthma and colitis in the lungs and colon. Most important of the research’s findings was that exposure to microbes during the first years of life, even if they no longer were as adults, still led to normal immune function, showing the important of early immune conditioning to microbes.


Status of Gene Therapy

In class we have touched on the issues surrounding research progressing from animal models to human subjects and we have discussed the possibilities that personalized medicine and the human genome project pose for the future of health care. Gene therapy , in which researchers continue to search for effective but safe vectors to introduce the DNA of  “healthy” versions of genes into diseased patients, is highly related to these discussion topics. This technique offers a huge range of possibilities for countless genetic disorders, but it has many associated complications as well.

This article (accessible through Emory’s network) outlines the troubled past of gene therapy, its setbacks, current research being conducted in the field, and the future of the therapy. Until reading this article, I was unaware of the rocky history of gene therapy. I deemed this important to share with the class so that we would all have a more holistic view of a this development in medicine that has the potential to be viewed through a singular, highly optimistic lens.

Upon reading the gene therapy article, I investigated the death of Jesse Gelsinger and came across this NY Times article about his death and the research study that caused it. This story is a grave reminder of why there are so many regulations in medical research, and that even when everything seems to have been done properly there are still occasionally unpredictable outcomes.

I am interested in following the advancement of gene therapy in the upcoming years, especially since new techniques are expected to be approved in the U.S. by 2016. Gene therapy has the potential to drastically change the way we treat many diseases, but we must not forget the history behind it.

Supernormal Stimuli

The other day in class we were introduced to Nikolaas Tinbergen‘s four questions during our discussion of proximate and ultimate causation. Tinbergen is also known for conducting research on “Supernormal Stimuli” in animals. A supernormal stimulus is defined as a stimulus that elicits a response stronger than the stimulus for which the response mechanism evolved. The blog post, Is Your Brain Truly Ready for Junk Food, Porn, or the Internet? connects Tinbergen’s research on supernormal stimuli in animals to that in humans with the help of a comic by Stuart McMillen, a Youtube video about Nicholas Carr’s research on the effect of the Internet on the human brain, and Diedre Barret’s book Supernormal Stimuli: How Primal Urges Overran Their Evolutionary Purpose. Modern day examples of supernormal stimuli for humans are: junk food, the Internet, pornography, TV, and video games.

I found this topic interesting because I am familiar with the tendency of our bodies to crave junk food based on what was evolutionarily valuable for our species to consume in the past, but I had never given much thought about how our minds may develop addictions to technology based on our evolutionary background. Humans have created their own supernormal stimuli by manufacturing foods that are sweeter and more calorically dense than naturally occurring foods, TV shows and video games that provide us with the ability to enter a world that may be deemed “better” than actual reality, pornography that tends to exaggerate sexual acts and the human body (which does not seem to be a new thing for humans based on the discovery of the Venus of Willendorf), and the Internet which provides access to endless information/entertainment/distraction at the tips of our fingers.

The blog post concludes by providing encouragement that humans are not inevitably doomed by our new environment. Unlike the animals in Tinbergen’s research, humans can differentiate between reality and supernormal stimuli. Humans have the ability to take control of their actions and moderate their indulgence in these behaviors. Could the ability to regulate the time and energy invested in surfing the Internet, watching porn, or playing video games serve as a factor of natural selection in present-day humans?