9606080651/653/654 GUT MICROBIOTA AND GASTROINTESTINAL HEALTH: CURRENT CONCEPTS AND FUTURE DIRECTIONS
INTRODUCTION:
Microbes that reside within the human gut are key contributors to host metabolism and are considered potential sources of novel therapeutics. The human gut microbiota has become the subject of extensive research in recent years and our knowledge of the resident species and their potential functional capacity is rapidly growing. The gut microbiota fulfils a very important role by helping the host from disease. This article critically reviews and summarizes recent literature reports on the role of microbiota and mechanisms involved in the progress and development of major human diseases, which include obesity, inflammatory bowel disease, colorectal cancer, celiac disease and diabetes.
REVIEW:
Obesity: Obesity is a chronic systemic disease caused by excessive fat accumulation. It is increasing tremendously day by day. In the last few years both in vivo and human studies suggest that the gut microbiota plays a vital role in the development of obesity, with the interactions between the microbiome, diet and host genotype being the key focus of research. [1] Researchers have found that in high fat diet there is an increase number of Bifidobacterium and Lactobacillus-Enterococcus sp. while decrease number of Bacteroides-Prevotella and Clostridium-histolyticum groups which induced obesity. Our dietary habits influence in the development of gut microbiota. It has been the focus of novel therapeutic treatments by using dietary interventions to modulate our gut microbial composition in order to treat diseases. A study using nanocomplexes loaded with (-)-epigallocatechin 3-O-(3-O-methyl) gallate (EGCG3ʺMe), a polyphenol present in oolong tea, was found to promote the growth of Bifidobacterium and Lactobacillus-Enterococcus sp. while inhibiting Bacteroides-Prevotella and Clostridium-histolyticum groups in high fat diet which induced obesity in mice models. [2]
Inflammatory bowel disease (IBD): IBD is generally a reduction of the Firmicutes and an increase of the Bacteroidetes, in particular of the species Bacteroides fragilis [3]. There is also an increase in Proteobacteria, and a notable increase in facultative anaerobic bacteria of Enterobacteriaceae, including the opportunistic pathogens Escherichia coli and Klebsiella pneumoniae. These causes inflammation of the mucosa and increase the risk of infections and leads to strong dysbiosis, with a reduction in microbial diversity, the number of bacteria and their metabolic activity [4]. Intake of probiotics and the faecal microbiota transplantation can be helpful for the disease.
Colorectal cancer (CRC): Recent publications have shown that there is a role of gut microbiota in the pathogenesis of CRC. It is a common cancer, causing about 500,000 deaths worldwide every year. Recent meta-analyses indicate that diets rich in fiber are associated with a lower risk of CRC, whereas consumption of saturated fat-rich foods such as red and processed meat, is strongly associated with an increased risk of CRC. [5] Mainly it is seen that Fusobacterium members are associated for causing CRC. This observation was supported by 16S rDNA sequencing analysis of the colorectal microbiome.
Celiac disease: Celiac disease is a chronic immune-mediated inflammatory disease of the small intestine. It is an autoimmune disorder, caused mainly for high gluten contained diet. From the recent studies, it is found that alternation of the gut microbial composition may contribute in the development or progression of celiac disease. It has been reported that Klebsiella oxytoca, Staphylococcus epidermidis, and Staphylococcus pasteuri are more abundant in duodenal biopsy specimens from patients with active celiac disease than in specimens from healthy individuals. In contrast, Streptococcus anginosus and Streptococcus mutans are less abundant in patients with celiac disease than in healthy individuals, regardless of inflammation status. [6]
Diabetes: In 2016, the world health organization (WHO) expanded the prevalence of diabetes from current levels to 592 million (12%) in 2035 [7], becoming the third major disease after cancer and cardiovascular disease. It has been found that people who have A. muciniphila in abundance have a lower risk to develop type 1 diabetes. So, A. muciniphila may be a potential probiotic in the treatment of type 1 diabetes.
FUTURE PERSPECTIVES:
In the past few years, there has been a flow in microbiome research and the attention has begun to shift from correlational studies towards mechanistic and clinical studies in understanding how the microbiome is able to influence human health and disease progression [8]. However, it is not without its limitations and improvements need to be made in order to enhance our understanding of the microbiome and to be able to translate this understanding to help us modulate the microbiome to improve our health. The use of pairwise interactions may be more appropriate in predicting the ability of specific probiotics to persist in the gut, or to determine the effects of removing a particular species, as opposed to higher order interactions [9].
CONCLUSION:
We are living with a huge number of microorganisms in our guts, ranging from bacteria, archaea to virus and fungi. Our gut microbiota develops with us and plays a crucial role in human health and disease. Large number of the studies published the last couple of years have reported differences in the microbiome under different conditions. Both types of approaches are important, that is, comparing diseased and healthy conditions and then showing the causality as a proof of concept. The general population as well as health practitioners should be rigorous when drawing conclusions from papers that assume that the discovery of differences in gut microbiota composition is potentially strongly associated with a specific disease or its overall evolution.
REFERENCES:
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