Association Between The Human Microbiota and Type II Diabetes Mellitus

Microbes in a gut under magnifying glass (from 2016)

Type II diabetes mellitus is increasing at an alarming rate, especially in children. According to the World Health Organization (WHO) statistics, the number of individuals with type II diabetes is projected to rise to more than 590 million by the year 2035 (Diabetes, 2017 and Upadhyaya, 2015). Type II diabetes is the result of the body’s resistance to insulin, a hormone that regulates blood sugar. The WHO states that type II is largely the effect of being overweight and very little exercise. Type I diabetes is distinguished by the bodies inability to produce insulin and there is no way to prevent it. Symptoms of type II diabetes include thirst, constant hunger, weight loss, vision loss, numbness in feet, and tiredness (Diabetes, 2017).  Scientists are trying to discover new ways to mediate the effects of type II diabetes and many think that the gut microbiota of the human body might correlate with diabetes in an interesting way.

The human body contains approximately 10 trillion bacteria, all with different functions and advantages or disadvantages within the human body (Sender, 2016). Many gut microbiota studies have been conducted that link the microbiota of individuals to certain aspects of their health. A study was conducted utilizing lab mice that suggested the gut microbiota of a human could be transferred to the gut of a germ-free mouse. The study also showed that the phenotype of the obese humans was transferred to the mice (Ridaura, 2013). Can the human gut microbiome be the key to mitigating the epidemic of type II diabetes? New research is looking to answer this question by relating the human gut microbiota to diabetes.

Authors of a recent study (Sedighi, 2017) look at specific bacteria found to be correlated with type II diabetes in other studies, including Lactobacillus, Bifidobacterium, Fusobacterium and Prevotella. The purpose of their study was to compare these bacteria obtained from the feces of healthy individuals and type II diabetic individuals using real-time quantitative PCR and to show that the composition of the gut microbiome was different between the two groups. The authors assume that diabetes is more related to a disturbance in balance of microbes in the human body rather than a select few creating or magnifying the issue. The authors determined abundances of each bacterium in the healthy and diabetic individuals. Out of the four microbial phyla they studied, they determined that at least two of them showed significant results. Lactobacillus levels were significantly higher in patients with diabetes and Bifidobacterium levels were significantly higher in abundance in the healthy subjects. Fusobacterium and Prevotella showed no significant differences. The authors also analyzed dietary habits and physical activity during their study (Sedighi, 2017). The International Physical Activity Questionnaire (IPAQ-short) was used to evaluate the study subjects activity. Physical inactivity is considered to be a health concern and can lead to an increased risk of Type II diabetes and other diseases (Craig, 2013). There was a significant difference in physical activity participation between the diabetic and healthy control group. The diabetic group had a lower physical activity score than the healthy group (Sedighi, 2017).

This study analyzed four families of bacteria, two of which were statistically shown to occur in different abundances within type II diabetic people and healthy people, a small but significant correlation between the human gut microbiota and type II diabetes. This study lead me to delve further into the general study of human microbial correlations with diabetes.

What is the diabetic microbiome composed of?

This study led me to question what the whole gut microbiome of a diabetic individual looked like and how it might differ from a healthy individual. A paper published in 2012, studied the metagenome of the gut microbiota in type II diabetes. The metagenome is the genetic material of the microbiota within the type II diabetic individuals. The paper stated that the gut of a type II diabetic is a “hostile’ environment and shows a “moderate’ degree of disturbance in the balance of the normal gut microbiota. It also indicated a decline in butyrate-producing bacterium and an increase in opportunistic pathogens (Qin, 2012). Butyrate-producing bacteria digest glucose to produce butyrate, the main energy source for colon cells (Barcenilla, 2000). An opportunistic pathogen is a bacterium that normally does not harm the host but, is capable of creating disease when their environment is disturbed. Another study found higher amount of Bifidobacteriaceae, Coriobacteriaceae, and Clostridiaceae in their Type II diabetic subjects (Wang, 2017). Unfortunately, there is no clear picture of what comprises the gut microbiota of a diabetic individual. Sample size varied between each study treatment (Wang n=40, Qin n=368) however the DNA sequencing platforms (Illumina HiSeq) and the 16S rRNA target gene were maintained. Differing experimental setups can lead to differing data outcomes. If more identical studies were conducted on the gut microbiota there would be more chances for similar data to be reproduced and stronger support for that data. Replication is the key to scientific research so if a research project can be replicated and the same results are obtained, the stronger the support for the outcomes of the project.  

How does one achieve a healthy microbiome?

This is all interesting, but wouldn’t this work be even better if there was something that could fix an unhealthy (diabetic) gut microbiome? Right now, diabetes can be prevented by eating a healthy and balanced diet and by engaging in physical activity (Diabetes, 2017). Being excessively overweight is correlated with diabetes so a great way to stop onset would be to stay within a healthy BMI range. BMI is the Body Mass Index used to determine healthy weight ranges for height (Obesity and overweight, 2017).  Scientist are suggesting that maybe, probiotics would be beneficial to the diabetic gut, if we could figure out what balance of microbes they could benefit from. An Verna et al (2010) concludes that very few studies have actually seen the contents of probiotics survive through digestive system. They mention that certain bacteria may have different tolerances for their environment and that the combination of bacteria in the probiotic might interact and create a hostile environment for them to try and survive in (Verna, 2010). Of course, the bacteria in the probiotic would need to survive in order to be effective. Another study, states that temporary recovery of ulcerative colitis was achieved using probiotics but still only says it could be possible for probiotics to improve human gut microbiota (Markowiak, 2017).

Unfortunately, there is no definite answer but there is progress in this field. Our next step as a scientific community should be to pursue research that leads to furthering the goal of finding clinical treatments for diabetes and other gastrointestinal disorders.

If this is interesting to you!

If the microbiome is interesting to you and you would like to learn more here are some links to interesting videos or research papers on the subject.

Rob Knight: How our microbes make us who we are

This video TED talk is given by Rob Knight, a very well known microbiologist and author. It is a general talk about the microbes all throughout the human body.

Three scientists on how the microbiome shapes our world

This is a blog post written by Brooke Borel who invited 3 scientists to talk about what interested them most about current microbiome research. A great read!

The healthy human microbiome

This paper goes over the healthy microbiome and was published in 2016 by the Genome Medicine journal.

Effects of Probiotics on Human Health

This is an interesting read on current information about probiotics, prebiotics and synbiotics. Keep in mind that there is not a definite answer to whether prebiotics works or not. More research needs to be completed.