Hello everyone. Welcome back to my Coursera class, Biochemical Principles of Energy Metabolism. This is a last session of entire class. Okay? Final session of week seven, so last class. So I just truly wish you could enjoy the biochemical basis of bioenergetics, and I hope you could obtain fundamental knowledges on the significance of energy metabolism in normal physiology, as well as the pathophysiology like diabetes and cancer and so on. So let me begin with the last session. It's about Microbiota. Microbiota. So, the human body is actually not just compose of not just human cells. Human body is many other living organisms and bacteria, actually, being populated in human and human body. So microbial community inhabiting a specific environment is so-called microbiota. It's like a definition. Okay? So think about microbial and human relationship. Many bacteria living in your oral cavity, or skin, vagina, or gut, right? So it's kind of mutual benefits identified for a long time. In particular, in your gut, like cellular density increases along the length of the gut, and the microbiota living in your gut is the densest and most diverse community and even in the whole human body. Okay? 10 to the 14th bacteria actually living in your gut. And the type of bacteria is more than 1000 different types of bacterial species actually so far identified. So human gut microbiota metabolic interactions are very, very complex and very, very dynamic. Okay? And those dynamic relationship can be changed over time depending on the diet you have, depending on the lifestyle, and types of disease you have, or depending on the antibiotics. Antibiotics means the removal of your gut microbiota. Okay? So I'm going to talk about the importance of microbiota in the regulation of bioenergetics of human. So Microbiota dysbiosis. So what is that? Dysbiosis. So perturbation of the normal healthy microbial profile is defined as microbiota dysbiosis. So simply speaking, good gut bacteria levels decreased and rather pathologically critical pathobionts, those bacteria levels will be increased and then in this imbalance situation, many human diseases can be indeed developed like dental plaque, bacterial vaginosis, psoriasis, a skin disease, atopic dermatitis. But more importantly, gut microbiota dysbiosis can lead to metabolic syndromes like obesity and type 2 diabetes. In particular, I'm going to show the data. Around 90 percent of the gut microbial community is actually indeed dominated by two members of phyla, Bacteroidetes and Firmicutes. And many correlation studies and biochemical analysis showing that the ratio of Firmicutes to Bacteroidetes when that ratio is increased that means when Firmicutes is somehow dominate in your gut is more like obesity and related metabolic syndrome can be developed. Okay? So, and gut microbiota and Bioenergetics. How those bacteria can influence the host human physiology, in particular, human metabolism, and complex carbohydrates, for example, dietary fibres? I introduced many like enzymes involved in intestinal digestion system. So some dietary fibres, humans do not have appropriate enzymes, but bacteria have. So gut micro-bacteria can further metabolize, fully metabolize those dietary fibres in your colon to oligosaccharide, monosaccharide or whatever, and finally, being fermented to, in this case, short-chain fatty acid called SCFA. Examples include acetate, propionate and butyric acid. And those short-chain fatty acids can be produced inside your gut, and then those SCFA can be observed in the colon. Okay? So without those gut microbiota, these dietary fibre may be just excreted and moved away, right? Through the feces. But in the presence of those gut microbiota, short-chain fatty acids will be metabolized and supplied to your cells and ultimately, energy harvest efficiency will be dramatically increased. So bioenergetically, energy harvest is very, very increased. And in parallel, those acetate, propionic acid or a butyrate can act as a signaling molecules. There are some examples and those fatty acids can affect host to human cell gene expression, and in some cases, they can activate gut-derived hormone like a GLP hormone secretion. So those bacterial drive to metabolite SCFA can influence the metabolic efficiency as well as host cellular signaling networks. So on top of that, there is another layer of microbiota-dependent metabolism. So bile acid metabolism. What is bile acid? Bile acid is the chemicals produced from cholesterol, and in particular, fat digestion. This bile acids are very, very important, right? For facilitate fat digestion. But interestingly, this bile acid can be further metabolized inside the lumen of colon and the secondary bile as it can be developed, can be produced. And then secondary bile acid metabolism is mediated by gut microbiota. And this type of secondary bile acids are produced and those bile acids, they are acting as a specific signaling molecules and some receptors will be affected, in particular, like the brown adipose tissue and muscles. When those secondary bile acids act upon those tissues, an energy expenditure will be increased and finally, diet-induced obesity can be increased. This is another important layer of gut microbiota. In this case, bile acids depend on metabolic actions. So, in that sense, it's like the scientists are working on the bioenergetics. They're primarily focusing on the human cell or biochemistry or human cell metabolism. But recently, many people are being interested in probiotics or prebiotics or the gut microbiota dependent metabolic regulations. So probiotics, definition-wise is the live microorganisms. So simply speaking, we can use a good gut microbiota, Lactobacillus, or Bifidobacterium. When we just establish those good bacteria a living environment in the gut of humans, then we can have many medical benefits. So, those bacteria can compete with other pathogenic bacteria or interfere with the bad bacterial life cycles, or they can directly attack or inhibit the pathogenic bacteria or they are just antagonistically live together inside the human gut. And the other approach is prebiotics. Prebiotics is just non-digestible food ingredients. And actually, when they are efficiently utilized by a gut microbiota in specific good microbial species, can be dominant and then favor gut like a microbial community in the host colon. This is another area of active or investigation in the regulation of human energy metabolism. So finally, I'm going to wrap up these gut microbiota dependent functions. So, in the very beginning, we have to think about host energy metabolism. So gut microbiota can break down diets like indigestible fibers or other types of diet that humans cannot use and produce gut microbiota specific metabolite and ultimately, those are used for human bioenergetics. And secondly, protection. So, resident good microbiota, gut bacteria like a bacteria [inaudible] protect the host from pathogenic population. The third one is immune control. I have no time to explain this topic but this is also very, very important action of gut microbiota. A good bacteria in your gut can influence the development and function of immune cells, immune cells, by excreting many bacterial substances and ultimately, help the strong and tight and healthy gut epithelial tissues. These are proposed functions of gut microbiota. Obviously, right now, many scientists are trying to fully understand the actual biochemical and molecular and physiological relationship between gut microbiota and the host. I mean, the human, in the context of metabolism as well as any other types of diseases. All right, I'm trying to wrap up this course by showing the list of topics. So, in the very beginning, we studied about the introduction of metabolism and what energy is, and so what is ATP, how those ATP molecules are utilized in our system, and we reviewed the metabolic organs and the basic concept of enzymes, and we began with the glucose digestion and full catabolic reactions called the cellular respiration. And then to make sure this glucose is not just given for free easily, plant cells undergo miraculous biochemical event called photosynthesis. And I also emphasized the importance of fat metabolism. So, glucose and fat. So, in addition to biochemical details involved in energy extraction, I mean ATP synthesis, we looked at physiologic inter-organ relationship. In particular, I emphasized the insulin signalling actions to understand diabetes mellitus. And then lastly, I believe I tried to introduce different types of bioenergetics. Mediated physiologic processes like starvation-induced metabolic responses, stress responses, exercise and alcohol metabolism and what types of biochemical adaptations are available for tumor cells and finally, the importance of gut microbiota. So, as I introduced in the very beginning of this course, this course is about basic conceptualization of bioenergetics. So, if you're really interested in the biochemical details, very details of each enzymatic actions, please look up to Advanced Level of Biochemistry textbook. I think like this biochemistry textbook, and then you can have those biochemical details by yourself. I just truly wish you could enjoy the content of my course, and I hope you could nicely build up the basic fundamental principles of bioenergetics. And I really appreciate your support and passion and I thank you very much for listening to, watch my video clips and my course. If you have any questions, feel free to send me e-mail and I'm going to respond with best answers. Thank you very much.
