Role of Gut Microbiota in Obesity

Question: Discuss about the Role of Gut Microbiota in Obesity. Answer: Introduction: Obesity and type 2 diabetes are two of most common chronic disorders, affecting the wide range of individuals throughout the world. The last decade experienced the exponential increase of number of people suffering from obesity along with its associated disorder type 2 disorder (Qin et al. 2012). Many studies highlighted that the sedentary lifestyle and increased consumption of high fat food are leading cause of these two chronic disorders. On the other hand, the role of gut microorganisms in keeping the intestine healthy is also known to everyone. Interestingly, these gut microbiota has co-evolved with the evolution of human species to support the evolving physiology and metabolism. The efficiency of metabolism depends upon the efficiency of these gut microbiota. It has been revealed that there are more bacteria in gut (1014) compared to total microorganisms in body (1013). There are approximately 2000 bacterial phylotypes in human intestine, the GIT metabolic activity is equivalent to the liver (Diamant et al. 2011). The gut microorganisms play a significant role in metabolism as well as immune functionality. The germ free mice, which are born into sterile environment has been seen to develop poor immunity, poor weight gain, have abnormal intestinal morphology and became susceptible to food borne disease. From the experiment, the role of gut microbiota in host metabolism, influence in GI tract development and blocking pathogens entrance has been revealed. However, most of the organisms habitat is the large intestine; 70 % of them are unculturable. For studying this wide population of microbes in culture-independent manner, the 16s rRNA of these microorganisms has been targeted in the flurescent in situ hybridization method (Kootte et al. 201 2). The sequencing technique helped in detecting the 16s rDNA regions of these bacteria. Therefore, to maintain a healthy weight, it is crucial to take care of microbial selves. Recent studies have demonstrated that gut microbes contribute to the energy harvest, storage and spending. The process remains most favourable if the amount of energy extracted from the diet is equivalent to the amount that is used in equilibrium maintenance. All the animals have developed smart strategies to protect the energy reservoirs. The obesity and type 2 diabetes are characterized as the low-grade inflammation and alterations in intestinal permeability, which is known as leaky gut (Tremaroli and Bckhed 2012). In case of obesity, inflammation is a significant component. As discussed previously that human intestine include 500 to 1000 microbial species, there are three dominant bacterial phyla, i.e. Bacteroidetes, Firmicutes and Actinobacteria. In recent studies with the germ-free mice has shown that germ-free mice, when fed with a high-fat diet failed to gain weight, however, the energy harvesting and adiposity, both increased while restoring the gut microbiota in the mice. In the 16s rDNA analysis of ob/ob (obese mutant) mice showed high number of Firmicutes and Bacteriodetes. The analysis also shown that the obese gut microbiota was enriched for metabolic genes, whereas the analysis showed reduced number of Bacteriodetes in obese person. Bacteriods can utilize plant polysaccharides as a source of energy (Wu et al. 2011). On the other hand, it has also been shown that diversity in diet promotes the high microbial diversity, which protects gut from the colonization of harmful pathogens. The pool of gut microbes may be different in individuals. Damag e to the microbial diversity at gut promotes adiposity. The changes in microbiota diversity is promoted by the antibiotic treatment or poor diet. In lean people, the diversity of gut microbes has been reported to be higher, whereas in obese people, Firmicures are higher in amount, with less diversity (Blaser 2014). Antibiotic administration has shown to reduce the diversity of gut microbiota, which can recover to its normal level after 1-4 weeks, antibiotic administration shown to reduce barrier function. Antibiotic administration promotes weight gain in mice, which is linked with the reduction of gut microbe pool. In a longitudinal study the results showed a significant association between antibiotic exposure at less than 6 months of age and weight gain at 3 years (Moreno-Indias et al. 2015). Akkermansia muciniphila is an inhabitant of mucus layer of human intestinal lining, which tends to be less abundant in obese people. Everard et al. (2013) reported that this microorganism has a significant role in reducing inflammation, showing its potential of protecting against obesity and Type 2 diabetes development. Researches found that gut bacteria is a market of type 2 diabetes. Gut bacteria interacts with the host through LPS, short chain fatty acids and bile acids. The reduction of gut bacteria pool leads to reduced gut barrier function, which in turn leads to the leakage of LPS into the blood stream, thereby influencing systematic inflammation and adipogenesis. Bacterial endotoxin has an important role in metabolic inflammation. Due to enhanced permeability of intestine or leaky gut, the gut-derived metabolic endotoxaemia can also occur, which increases the risk of obesity associated-diseases (Everard and Cani 2013). This condition can also take place, if increased concentration of bacterial toxin LPS enter the blood due to leaky gut, triggering inflammation. Research found that individuals consuming high-fat foods have increased level of LPS in blood and altered composition of gut microbiota. One study showed role of hunger stimulating hormone ghrelin, which is triggered by Helicobacter p ylori. Studies reported that elimination of H. pylori leads to increased appetite and weight gain, showing the role of H. pylori in protecting against weight gain and obesity. In colon some bacteria produces short chain fatty acids like butyrate, propionate and acetate through fermentation. Butyrate plays a key role in supporting intestinal lining integrity, increasing fluid and electrolyte uptake, promoting blood flow, serving as energy source for colon epithelial cells, exerting immune-metabolic effects, acting as energy source as well as signalling molecule (Everard and Cani 2013). Obesity and type 2 diabetes are the results of multiple factors, including high energy food consumption, age, less physical activity and genetic factors. Researchers have revealed several important facts regarding the role of gut microbiota in the development of these metabolic disorders, but controversies exists regarding the degree of contribution of gut microbiota in development of obesity and type 2 diabetes. The complexity of microbiota and its interaction with the host are making is challenging to reveal the most appropriate findings. However, manipulating the gut microbes by prebiotics, probiotics, changes in diet or radical methods of fecal microbial transplant have shown significant success in obesity management, revealing the link to the role of gut microbiota in obesity and associated diseases like type 2 diabetes. Reference List Blaser, M., 2014.Missing microbes. Oneworld Publications. Diamant, M., Blaak, E.E. and De Vos, W.M., 2011. Do nutrientgutmicrobiota interactions play a role in human obesity, insulin resistance and type 2 diabetes?.Obesity Reviews,12(4), pp.272-281. Everard, A. and Cani, P.D., 2013. 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