Research Paper: The Gut Microbiome, Obesity, and Mental Health
The gut microbiome has become an important topic in the biology field since it has impacts in human obesity and mental health. For the same reasons, the gut microbiome can help researchers find ways to help individuals get to a healthier way and help individuals find cures for different mental health such as anxiety. The gut contains millions of bacteria that helps with digestion of nutrients and sugars that then get turned into a source of energy. All individuals have a microbiome which can be similar to other individuals. However, there are many differences in every individual gut microbiome because there is a variation in the diversity and the number of bacteria living in the gut. The gut microbiome can be impacted by dieting, birth, the mother of the individual, and the environment. Many researchers use different techniques to find how the gut microbiome and lose of its bacterial diversity can affect the human body. Topics such as dieting, and obesity are known to be affected by the different bacteria in the gut since they could affect the way in which an individual digest their food this can affect individual. Furthermore, there has been research that has found that there are healthy bacteria that could help individuals lose weight and become healthier. However, multiple research has found that the gut microbiome can be affected by the diet of each individuals since certain bacteria could decrease the chances for an individual to lose weight. There has been multiple research done stating that the gut microbiome does affect the way in which we are able to stay at a healthy weight.
“Obesity is associated with phylum-level changes in the microbiota, reduced bacterial diversity and altered representation of bacterial genes and metabolic pathways.” (Turnbaugh, et al., 2009). Turnbaugh wanted to figure out the differences and similarities between the fecal samples of twins and obese twins. The decrease of bacterial diversity can be influence by the genetics of family members and the way in which they process food. The researcher wanted to find the difference in the gut microbiota of identical and fraternal twins. The researchers used twins that were not taking any antibiotics since antibiotics could eliminate the diversity of the gut microbiota and there was a tRNA sequencing done to test the biota of the samples being taken from each individual. “No matter which region of the gene was examined, individuals from the same family (a twin and her co-twin, or twins and their mother) had a more similar bacterial community structure than unrelated individuals” (Turnbaugh, et al., 2009). The sequencing of tRNA was able to determine that individuals that were closely related had a higher similarity of the gut microbiome than those that were not closely related.
However, Turnbaugh was able to determine the way in which obesity can occur even if the individuals were not genetically similar. The researcher tested the fetal samples of the obese twins to figure out the biome diversity of a healthy weight individual and those that were not at a healthy weight. The different methods used in the paper were able to determine a reduce diversity in the gut microbiome in individuals that were obese than those that had a healthier weight. “This reduced diversity suggests an analogy: the obese gut microbiota is not like a rainforest or reef, which are adapted to high energy flux and are highly diverse; rather, it may be more like a fertilizer runoff where a reduced-diversity microbial community blooms with abnormal energy input.” (Turnbaugh, et al., 2009). A low diversity microbiome does not allow the same strategies as one with high diversity that can allow the digestion and use of energy in a more proficient way. Individuals in the obese community are not able to lose weight simply because their microbiome is not strong enough. Similarly, Turnbaugh, looked at ways in which individuals’ gut can be affected by looking at glycoside hydrolase and glycosyltransferase in each of the individuals. Turnbaugh was able to find that this could show the way in which diet affected the different results since glycoside hydrolase was involved in the differences and glycosyltransferase was common between all individuals. “This suggests that the number and spectrum of glycoside hydrolases is affected by ‘external’ factors such as diet more than the glycosyltransferases.” (Turnbaugh, et al., 2009). This can help determine the ways in which an individual that have an unhealthy weight could have certain enzymes or other factors that are not involved in individuals that have a healthy weight. Similarly, the enzymes in an obese individual could be doing less work to use the energy in the diet compared to those that have a healthy weight and have a dependable metabolic pathway with a high diversity of bacteria.
Similarly, other papers have found similar results as to why obese is affected by the microbiome. Obesity could lead to other medical conditions such as type 2 diabetes since the body is not using the energy correctly. Researcher Liu and others have found that genetic and metabolic pathways can affect the obesity and the lead of type 2 diabetes. “We found that these young, obese individuals had lower gene counts and bacterial diversity than controls (Fig. 1a–c), indicating that gene richness is lower in obesity regard- less of ethnicity or age.” (Liu, et al., 2017). The ethnicity and ages of individuals do not have an impact in the low diversity of bacteria in individuals that are obese, the main reason for obese is simply the low diversity of bacteria. The researcher also looked at the gene variation of the individuals and genes that could potentially affect people from being able to lose weight. “Sing a metagenome-wide association analysis, we identified 350,524 genes associated with obesity (P < 0.01, Wilcoxon rank- sum test, FDR = 0.047). The association analysis also showed a P value distribution with a marked enrichment of obese-associated gene markers with low P values (Supplementary Fig. 2b), suggesting that these genes were associated with obesity.” (Liu, et al., 2017). Compared to Turnbaugh, who looked at the tRNA to find the way in which individuals were genetically similar when it came to obese.
Additionally, Liu used MLGs to find the bacteria’s that could be affecting individuals in the community. MLGs annotated to Ruminococcus torques, Ruminococcus gnavus, Dorea longicatena, Dorea formicigenerans and Coprococcus comes, and a cluster consisting of MLGs for Lachnospiraceae bacterium, Fusobacterium ulcerans and Fusobacterium varium, were highly enriched in obese individuals (Fig. 1e).” (Liu, et al., 2017). There are many bacteria’s that relate to individuals in the healthy weight community and that relate to the ones in the obese community. Compare to Turnbaugh, Liu used the MLG method to find the connection between bacteria’s and obese individuals instead of the tRNA method, but both gave similar results. Both papers were able to identify bacteria’s that could affect individuals that are obese which can lead to diets not being able to work when an individual wants to reduce weight to reach a healthier stage.
Liu also found a way in which KEGG pathways are a big part of carbohydrate transport in the body and the gut microbiome. Many results were found that could mean that obese individuals are using the carbohydrates. However, the inflammations could lead to the unhealthy weight and high sugar levels causing the diabetes. The researcher also found a connection between the abundance of amino acid “serum concentration” that could be affecting individuals that are obese. “We found that the abundance of genes related to ‘LPS biosynthesis’ and ‘peptidoglycan biosynthesis’ was higher in the microbiome of obese individuals than in that of lean controls, which may be related to the observed higher serum concentration of LBP, TNFα and IL6 in obese individuals (Supplementary Table 1).” Different bacteria’s will be eliminated or added in the gut based on the serum concentration and
Bibliography
Liu, Ruixin, et al. “Gut Microbiome and Serum Metabolome Alterations in Obesity and After
Weight-Loss Intervention.” Nature Medicine, vol. 23, no. 7, 2017, pp. 859–868.,
doi:10.1038/nm.4358
Turnbaugh PJ, et al. “A Core Gut Microbiome in Obese and Lean Twins.” Nature, vol. 457, no.
7228, 2009, pp. 480–4., doi:10.1038/nature07540