The human body, consisting of about 10 trillion cells, carries about ten times as many microorganisms in the intestines. Gut microbiota is an assortment of microorganisms inhabiting the length and width of the mammalian gastrointestinal tract. The composition of this microbial community is host specific, evolving throughout an individual’s lifetime and susceptible to both exogenous and endogenous modifications. Gut flora have around 100 times as many genes in aggregate as there are in the human genome. Recent renewed interest in the structure and function of this “organ” has illuminated its central position in health and disease. The microbiota is intimately involved in numerous aspects of normal host physiology, from nutritional status to behavior and stress response. Additionally, they can be a central or a contributing cause of many diseases, affecting both near and far organ systems. The overall balance in the composition of the gut microbial community, as well as the presence or absence of key species capable of effecting specific responses, is important in ensuring homeostasis or lack thereof at the intestinal mucosa and beyond.
The mechanisms through which microbiota exerts its beneficial or detrimental influences remain largely undefined, but it can be said that gut microbiota play a contributing role in the development of diabetes and non-alcoholic fatty liver disease (NAFLD) independent of obesity. Gut microbiota transplantation, i.e. grafting new microbiota from a healthy donor’s fecal material and transplanting it into the colon of a diseased recipient, can potentially prevent diabetes and NAFLD. Diabetes is a metabolic disorder that is characterized by high blood glucose in the context of insulin resistance and relative insulin deficiency and Non-alcoholic fatty liver disease (NAFLD) is one cause of a fatty liver, occurring when fat is deposited (steatosis) in the liver not due to excessive alcohol use. It is related to insulin resistance and the metabolic syndrome and may respond to treatments originally developed for other insulin-resistant states such as weight loss, metformin and thiazolidinediones.
Different microbiota cause different metabolic responses in animals. By implanting microbiota from healthy individuals prevented the development of liver inflammation and insulin resistance, both indications of liver disease and diabetes. Thus, gut microbiota transplants could have a therapeutic role in the development of these diseases. The intestinal microbiota is currently viewed as a ‘microbial organ’ in its own entity, which plays vital roles in terms of metabolism and immune function. Transplanting microbiota could therefore potentially restore gut functionality and re-establish a certain state of intestinal flora.