The Differences Between the Male and Female Gut Microbiome and Its Impact On Health
When we think of biome, we may imagine a complex web of species dispersed throughout
vast landscapes. One biome that we often fail to recall is ourselves, which is home to a
diverse range of microbial species. Microbiota covers almost every surface of the body, to
the point where they have become ubiquitous to us. These form biomes within our
organs and tissues, which are distinct from one another. The organism in the oral
microbiome differs from the gut; the latter is the one of most interest to us. The gut
microbiome contains trillions of bacteria, fungi, archaea and viruses, all interspersed down
the intestinal tract. Their main purpose is to aid in digestion, control hormonal levels,
promote immunity, produce vitamins and support neurological health. This network of
microorganisms collaborates with the body to boost our physical well-being, and in today’s
age, we have access to many probiotic products (a prime example being yogurt) to maintain
a healthy gut microbiome. While there is an association between lifestyle and physiology
with microbial health, recent studies suggest that our genetics may also play a
significant role.
The X chromosome is among the few which have become famous beyond the world of
science. It is one of two sex chromosomes whose function extends well beyond assigning.
biological gender, as it impacts normal development and the overall health of an individual.
Now as most will know, females have double the number of X- chromosomes than males.
Many of us are also aware that to balance the chromosomal dosage, one X is inactivated in.
women via a complex pathway. Resulting in both men and women possessing one active X
chromosome per cell. However, what many don’t realise is that females can have either of
these chromosomes active in a cell, the distribution of which is determined by unknown
processes. So, either allele of a certain gene can be active in each cell, and we theoretically
assume there is a 50/50 split. This provides women with an advantage when it comes to sex-linked
diseases like red-green colour-blindness. The causative mutant resides on the X chromosome,
thus, men who have a single copy are predestined to present the illness. While
women have a second copy to fall back on if one chromosome contains the pathogenic
allele and thus are characterised as carriers. It requires the rare event of women inheriting
chromosomes that both contain the mutant for them to be colour-blind. While it may seem
rather tangential, it is an important factor to consider when comparing the gut microbiomes
of males and females.
Analysis of the sex-specific interactions of the microbiome is a growing branch of study in
health. A given foetus lives in a sterile environment during gestation and begins
accumulating its personal microbiota upon birth. From there, they rapidly spread and
diversify until it reaches an adult-like stable distribution, typically by the time an individual
turns three. In adults, the gut microbiome is relatively stable, with slight fluctuations
depending on daily nutritional intake and other personal differences. This persists until a
person reaches the advanced aging portion of their lives, where they begin to experience
depletion in their immune function along with physiological changes, which can alter their
microbiome. Hormones are an integral feature of health that can be greatly modulated by
microbiota, and they are tagged by these organisms as such to benefit in their control. Most
interestingly, the health of gut microbiota has been linked to various neurodegenerative
illnesses. Ranging from childhood-onset conditions like autism to adulthood conditions like
Multiple Sclerosis (MS) and later Alzheimer’s or Parkinson’s Disease. However, until
recently, sex-based differences were not greatly ventured into clinical studies. 2016
paper by Cox et al. found that males have a heightened susceptibility to pathogens such as
Campylobacter jejuni, the Hepatitis B virus and Mycobacterium tuberculosis. The shared
feature shared by all these organisms is the greater severity of the diseases they cause.
Thus, males are at a biological disadvantage in terms of their likelihood of contracting
serious illnesses. Our adaptive immune system is composed of immune cells which protect us
from infection by recognising unique markers on pathogens called antigens. These antigens
signal cells to produce the respective antibody that can be used to mark the microbe for
termination. This model is consistent for all humans; however, the level of immune function
can considerably vary between females and males.
Factors that influence infection control include the effects of sex-linked steroids and X-linked
immune genes. In direct contrast to males, the female antiviral response is ten times
more effective. In addition, their immune system possesses stronger cell-mediated antibodies
and innate responses. An X-linked gene mediates the function of the pattern recognition
receptor, TLR7, which may explain this disparity in immune function. It could further be
postulated that the dosage effects of X-chromosomes may also influence this. Possibly the
mere presence of a second TLR7 gene may be responsible for the heightened immune
function in females. As mentioned before, another facet that is being researched is the
association between gut microbiota and neurological disease. Gut microbiota regulates our
metabolism, which breaks down ingested materials to extract and expend energy. This
means that dysfunction of gut microbiota is a potential basis for obesity, which is attributed to
having a greater energy intake than expenditure. Furthermore, obesity has been linked to a
higher risk of neurological disease. Thus, there is an implicit connection to the metabolic
fluctuations caused by gut microbiota. In studies using mice, limiting caloric intake improved
the clinical outcomes models for Alzheimer’s and MS. The changes were more distinct
between the sexes, as female mice displayed greater sensitivity to the treatment than
males. Overall, diet can be a viable treatment to mitigate the effects of certain neurological
conditions.
Our gut microbiome has an overwhelming effect on our health. It affects everything from
our body’s defence mechanism to neurological function, and there is still much more left for
us to uncover. In particular, there seems to be a significant difference in how men’s and
women’s bodies are affected, most likely due to our chromosomal variances. The amount of
importance that is being placed into this area of research solidifies the idea that the health
of our own microbiome must be prioritised in equal measure as any other ecological biome.