Obesity and different diseases: Does the cause reside within the very own human gut?

Obesity and different diseases: Does the cause reside within the very own human gut?

 

Have you ever come across the word, “microbe”? The living organisms that are too small in size to be visible to the naked eye and require a microscope for you to see them. Microbes often include bacteria, algae, fungi, archaea, protozoa and viruses. The first instinct upon hearing these names is to think of a disease. But what if I tell you that you have microbes residing in your bodies, too? In fact, more than half of your body is not human but microbial. Surprised? There’s even more to be surprised about. 

These microbes (generally bacteria and archaea) live not only on your skin but also inside your nose, your throat, your mouth, in the vagina, and in the gut. Collectively, this microbial community inhabiting human bodies is referred to as Microbiota. Much of the bacteria lives in our intestines and is known as the ‘Gut Microbiota.’ The relationship between these bacteria and human is often mutualistic, meaning both the host (humans) and the colonizers (microbes) benefit from it.

 

 https://www.genengnews.com/insights/tapping-the-human-gut-microbiome-part-2/

How do humans acquire these microbes?

Now, the question is how and where do humans get all these microbes from? Are they part of humans before birth or does the environment give these microbes to humans? Hold on a second, you’re about to find out. Humans get their very first microbes at a stage as early as their birth. Quite often, the body of the mother is what gives the newly born his very first microbes but which microbes would be given to the baby varies depending upon the method with which he has been delivered. For a baby delivered through the vagina, the set of microbes would be different as compared to the one delivered through the caesarian section.

Other factors also influence the microbes you inherit at an early stage. For example, nutritional factors such as bottle-feeding or breastfeeding. As you grow, the composition of your microbes changes depending upon different factors and living conditions. That means, your body will have different microbes during different stages of your life and you will have a different set of microbes in your adulthood and old age as compared to your childhood or infancy.

Why is the gut microbiota composition so important? 

The composition of microbes varies in each person depending upon different factors but the set of gut colonizers (the core gut microbiota) and genes (the core microbiome) is common among different individuals. The microbial composition is important for your body because it makes an impact on your development. It plays an important role in many different metabolic processes.

Under normal conditions and composition, gut microbiota helps humans in harvesting energy, promotes fat storage and boosts immune response by releasing important substances called metabolites, for the body. Metabolites are intermediates of metabolism that help in performing normal biological activities. These metabolites either influence other microbes present in the body or act as signals to the host either directly or through bloodstream, acting on organs like liver, adipose depots, muscles and even the brain or affecting their function. Microbial enzymatic activities can have a direct effect on the fermentation of polysaccharides and on bile-acid metabolism, or act in conjunction with the host on the metabolism of choline. Thus, these microbial communities are responsible for normal metabolic function and immunity.

 http://sitn.hms.harvard.edu/flash/2016/second-brain-microbes-gut-may-affect-body-mind/ 

Understanding the gut microbiota along with its composition is vital

Advancements in metagenomics, high-throughput sequencing technology, direct sequencing of genetic material, development of bioinformatics tools, and 16S ribosomal RNA have enabled ways for us to understand the gut microbiota in a better way. Because of their help, we know that if the composition of the gut microbiota is altered, it can lead to life-threatening diseases. The knowledge of the microbial communities in our body are not only important to understand its relationship with different diseases but the development of proper treatments in the present and the future is also highly dependent on the correct understanding of the microbiota composition, its complexity, and the changes that occur in it. Therefore, there is a need for us to increase our knowledge of human microbes and how they affect us.

 Alternations in the composition of gut microbiota

The composition of gut microbiota is a matter of vital importance. There are certain factors that lead to dysbalance in the composition of the gut microbiota in the body. Reduced or imbalanced bacterial diversity due to different factors leads to “dysbiosis” which is defined as the condition of having imbalanced microbial communities in the body. Dysbiosis can further, be responsible for a variety of diseases including gastric ulcers, obesity and metabolic syndromes, colon cancer, inflammatory bowel disease. The composition of the gut microbiota is important because the pattern of intestinal fermentation and the type and amount of metabolites produced is highly determined by the bacterial composition of the gut. In simple words, the right composition is what is responsible for the efficient working of the gut microbes.

 

 Figure: Jeremy K. Nicholson et al. Science 336, 1262 (2012)

What develops and changes the gut microbiota composition?

 

There are certain factors that are responsible not only for the type of microbial communities you acquire but also for changing their composition. These factors include:

Age and delivery pattern: How a baby is delivered, strongly influences his body’s microbial composition. If a baby is delivered through vagina, the dominant bacteria in that baby would be Lactobacillus, Prevotella and Atopobium. On the other hand, if a baby is delivered by caesarian section, he will receive microbes from the skin of the mother and the hospital environment which microbes would be different from those acquired through vaginal delivery.

As we age, the microbial composition changes and continues to take shifts throughout childhood, adult life and old age depending on a number of different environmental factors such as diet, antibiotic use, stress, disease, injury etc.

Diet: Diet is another important factor that plays a major role in shaping the early microbial composition of a child. If a baby is breastfed, the prominent species of bacteria in the gut would be Lactobacillus and Bifidobacterium. During suckling, our microbial community forms quite rapidly. Breast milk has different oligosaccharides in it that can be broken down easily by these specific species of microbes, which results in an increase in short-chain fatty acids. This directs our immune system to increase the expression of immunoglobulin G and increase our immunity. On the other hand, the infants raised on formula have Enterobacteria, Bacteroides, Enterococcus, Clostridia, and Streptococcus as dominant species. The composition of primary microbiota during the early period after birth is important to protect babies from diseases related to poor immunity.

Antibiotics: The use of antibiotics destroys the gut microbiota causing dysbiosis and increases the growth of unwanted microbes.

Probiotics: Probiotics are live microorganisms that have health benefits when consumed. The most common probiotic species include Lactobacillus, Bifidobacteria and yeasts, such as Saccharomyces boulardii. Probiotics improve health by promoting favourable types of gut microbes.

Epigenetic modifications: Epigenetic modifications are heritable changes in the phenotype of a gene without any alternations in the DNA sequence itself. These changes can be brought about by a number of factors such as diet, medication and chemical exposure. However, the most omnipresent factor in these modifications is the gut microbiota. Gut microbiota influences these modifications via some metabolite it produces or through some structural component interacting with the host cell. This, therefore, influences the overall functioning of the body. For example, if a gene that makes a tumour suppressing protein is turned off as a result of an epigenetic change brought about by the gut microbiota, it can lead to disease.

Other factors: Lack of exercise, poor sleeping habits, stress, smoking and alcohol consumption are some factors also influence the microbial communities residing in our body in harmful ways.

 

Association of altered gut microbiota with the prevalence of diseases

The change in the composition of the gut microbiota has vastly been associated with the prevalence of obesity and its comorbidities including insulin resistance, type 2 diabetes mellitus, cardiovascular disease and even certain cancers. Recent years of research have proven to be valuable. Sekirov has tried to investigate the complexity of gut microbiota in order to understand its correlation with different diseases and health conditions.

 

How to protect the body and its microbiota

Fermented food: Fermented food with live bacteria or yeast such as cheese, yoghurt, Lacto- fermented pickles etc. can help you increase the good bacteria in the gut or restore it.

Prebiotic foods: Prebiotics, which are different fibres indigestible for humans but digestible for the living micro-organisms residing in the human bodies, help in stimulating the growth of friendly bacteria in the gut. They can be found in different fruits and vegetables and whole grains.

Avoiding unnecessary use of drugs: Drugs such as antibiotics deplete your gut microbiota. If taking them, be sure to increase the intake of prebiotics to avoid your microbial composition from being depleted.

Non-steroidal anti-inflammatory drugs (NSAIDs) are some painkillers that provide short term relief but often affect the lining of the intestines, causing bleeding. These drugs disturb the gut microbiota composition. Therefore, one should avoid taking them until it’s really necessary.

Healthy lifestyle habits: Healthy lifestyle habits such as good sleeping pattern, exercise and zero alcohol consumption can also help you protect your microbiota.

Concluding remarks

Allah has bestowed us human-beings with the best of everything. Humans contain worlds inside them in the form of tiny organisms which carry out mechanisms for the survival of humans. As humans, it’s our duty to protect the gift we are given and take care of our bodies in the best possible way so that the microbial communities that aid our survival work in their best possible form. The relationship between gut microbiota and disease is quite evident, which is in so many ways dependent on the composition of the microbial communities. But it does not stop here. With the advancements in technology, the researchers are trying their best to get into further depths of the relationship between gut microbiota and the onset of diseases. In the upcoming years, a lot more treatments will be available then there are now. Hopefully, the future of our knowledge about the gut microbiota will be full of exciting revelations.

Author’s information: Adeena Khashir, BS biotechnology, has written this article. She was inspired motivated by her mentor Miss Iqra Aslam (MPhil Biochemistry), Lecturer of Biochemistry at University of Management and Technology, Sialkot, Punjab, Pakistan.

 

 Reviewer and Editor information: This article is reviewed & edited by Muhammad
 Numan (PhD Scholar Biochemistry).

Figures: The figures used in this article are properly cited in the article.

References: All the resources which are used to write this article are given below.

·    Tilg, H. & Zmora, N. & Adolph, T. E. & Elinav, E. (2019). The intestinal microbiota fuelling metabolic inflammation. Nature, 1-15.

·    Cani, P.D. & Hul, M.V. (2020). Gut microbiota and obesity: causally linked? Expert Review of Gastroenterology & Hepatology, 1-4.

·    Tremaroli, V. & Bäckhed, F. (2012). Functional interactions between the gut microbiota and host metabolism. Nature (Vol. 489, pp. 242-249)

·    Nicholson, J.K. & Holmes, E. & Kinross, J. & Burcelin, R. & Gibson, G. & Jia, W. & Pettersson, S. (2012). Host-Gut Microbiota Metabolic Interactions. Science, 336, 1262-1267.

·    Sekirov, I & Russell, S.L. & Antunes, C.M. & Finlay, B.B. (2010). Gut Microbiota in Health and Disease. The American Physiological Society.