Better Know Your Microbiome
Though there is plenty of coverage on the potential of microbiome research, often highlighting how the bacteria in your body outnumber the human cells, scientists do not yet fully understand the connections between the microbes in your gut and biological functions. Your microbiome could influence your ability to lose weight, immune response and even your mental state but we still require further understanding of the fundamental principles that result in an individual’s particular microbiome.
Most interestingly, the microbiome appears to be subject to the same forces that shape ecology. New niches form as populations of bacteria, archea, fungi, protozoa, and viruses evolve though natural selection, drift, and migration. One added dimension of genetics in the microbiome is the ability to share traits between species though horizontal gene transfer. In fact, strains of bacteria in the same niche have higher rates of horizontal gene transfer.
We also know that most individuals are colonized by 3 to 4 main strains of bacteria and generally more diversity of species is better than less. But it’s not clear how host genetics influence a microbiome composition. Because identical twins have more similar microbiota than their siblings and sibling microbiomes are more similar to each other than to unrelated individuals, genetics of the human host does play some role. Though genome wide association studies have difficulty tying specific variants in the human genome with outcomes in the microbiome, one illustrative case is the effect of the lactase persister gene and the presence of bifidobacteria in the gut. Individuals who do not possess the lactase persister gene are unable to digest lactose. If they continue to consume products containing milk, it translates to a higher abundance of bifidobacteria which break down the lactose instead. But such clear-cut examples have been hard to find. There is evidence that certain genes make it more likely to have a certain type of microbiome but the actual mechanism of relationship is often unknown. At best the microbiome appears to be a complex trait like height, which is affected by multiple genes, while the exact effect of single genes may not be clear.
While some would argue that our understanding of microbiome is too early stage for making health recommendations, several companies have been offering analysis of the bacteria in stool samples. A report from Viome, for example, would include a diet and supplement plan based on your microbiome health. However, a comparison of several different microbiome tests showed high variability in reports and only broad suggestions for diet changes. A more promising application comes from Persephone Biosciences which is pairing microbiome analysis with trials for cancer therapeutics in the clinic. The aggregate data can be used to inform development of drugs to be used in conjunction with immunotherapy for example.
While the implications of microbiome studies can be far reaching, the immediate benefits for heathy individuals is limited. At the same time, more data from all types of donors does help the field move forward. There are several nonprofit initiatives including American Gut which have created an open platform for microbiome research. Such initiatives may be the best way to aggregate the data which can be used to create actionable evidence for improving our microbiome health.
