Arzo Iqbal
This week marks the 70th anniversary of the National Health Service (NHS) in the UK. It was formally launched on 5th July 1948 by Aneurin Bevan, the Health Secretary at the time, and has gone on to provide healthcare for generations of people. As well as being a time to reflect on the history of medicine on the whole, we thought this anniversary would be a good time to look to the future of medicine, and beg the question, how important is an understanding of evolution in medicine?
Many life-saving treatments and techniques used today in medicine have been discovered without evolutionary input. So why use evolutionary medicine now? Evolutionary medicine has helped to introduce strategies to control microbial drug resistance, predict future patterns of how disease might change and aided in developing treatments for infectious diseases. Without these treatments, medical care will be affected drastically; surgery, transplantations, care of vulnerable patients and many more treatments, will not be possible. Moreover, analysis of the evolutionary past of humans and our relationships with other species, has enabled us to safely and effectively test drugs on suitable organisms. For example, treatments for HIV are tested on primates, because we share around 98% of our DNA with them, hence effects and responses could be similar.
Many health problems can be considered from an evolutionary perspective, giving us new insights into disease, and leading to innovative treatments which create advances in medicine.
Drug resistance is a major issue, and if not controlled, 10 million people worldwide may die by 2050 from drug resistant infections. Some methods employed today to combat drug resistance, apply evolutionary theory; evolution is driven by variation; some microbes may have genetic traits expressing resistance. Therefore, if a microbe with the genetic mutations expressing resistance, cannot survive, emergence of resistant strains can be decreased. Combinational therapy and antibiotic cycling are strategies which exploit this process.Combinational therapy combines several drugs, thereby increasing the number of ‘genes’ needed which promote resistance, thus lowering chance of resistant strains emerging. The drugs usually work by inhibiting β-lactamase enzymes or interfering with signaling pathways A study comparing survival rates of patients treated with piperacillin and combination therapy demonstrated that resistant strains in the former were more frequent (42%), compared to the latter (17%). Antibiotic cycling, rotational use of antibiotics, works by decreasing the selective pressure on bacteria for genes expressing resistance. A study on aminoglycoside resistance, found that resistance to Gentamicin decreased when replaced by amikacin rotationally.Furthermore, studies have found that bacteria have evolved cellular processes – stress response regulators – which sense and respond to changes in their environment by altering gene expression. Therefore, by identifying these stress response regulators, we can develop drugs to switch them off, thus preventing microbes from adapting to new environments, and so decreasing the number of resistant strains arising.Drug resistance is not just an issue in bacteria but also in viruses, especially in HIV. How can evolutionary science help to combat HIV?
Evolutionary biologists have aided in developing techniques to reconstruct evolutionary trees, which show genetic relationships between pathogens and their origins e.g. phylogenetic analysis. Analysis of these relationships can show us how close relatives of a particular pathogen may have different effects on different organisms. This can be exploited to find treatments and even cures for a particular disease. Phylogenetic analysis of HIV indicated a very close relation to SIVs (Simian immunodeficiency viruses), which infect primates Researchers have developed a vaccine to treat a deadly form of SIV in primates, which contains a virus that expresses SIV proteins. This stimulates the immune system to detect and eliminate the virus. Using this, they successfully removed all traces of the virus. The close evolutionary relationship between SIV and HIV may be exploited to develop a similar vaccine, for HIV, which may have the same effect in humans.
Furthermore, researchers have mapped the evolutionary history of SIV in primates, and found the time it took for the virus to become non-lethal; they have speculated that the HIV virus may follow a similar time-frame to naturally becoming non-lethal in humans. By finding out how the SIV virus became non-lethal, we may be able to develop treatments to accelerate this process within humans for HIV.
The application of evolution to medicine, does not just help to combat infectious diseases but can help to deal with diseases arising from our lifestyle. For instance, the environment our ancestors evolved in is very different to the environment we live in today. Humans co-evolved with symbiotic bacteria and parasitic worms, however modern hygiene results in reduced exposure to these microbes; increasing our susceptibility to allergies, asthma and auto-immune diseases. By understanding the evolutionary past and origin of humans, we can predict the diseases we may face today and in the future. Therefore, enabling us to develop appropriate treatments, for example, Crohn’s disease can be treated by ingesting parasitic eggs of worms.
The application of evolutionary thinking to medical research can have profound impacts in medicine. From management of drug resistance, treatment for infectious diseases, to predicting future diseases. Many doctors may feel that knowing why a certain disease occurs does not help them with treating it, but evolutionary medicine is not just about why disease happens; it’s about finding the root of the problem and dealing with it from there. A crucial point to make is that evolutionary medicine is not an alternative form of medicine, but rather gives rise to new theories to create advances in medical practice. Furthermore, doctors who can think beyond what is wrong with a patient, to why it is wrong, can help direct research and therapy. It’s clear that evolution is very important to medicine, and its application has benefitted healthcare and will continue to do so.
Check out our new summary video to see what we’ve been up to on Seeking Science throughout June!
