Gut Microbiota Flashcards
What is the difference between the terms “microbiome” and “microbiota”?
The microbiome refers to the collection of genomes from all microorganisms found in a particular environment, such as the gut. In contrast, microbiota refers to the actual microorganisms themselves—bacteria, viruses, fungi—within that environment.
What is the gut microbiota and what role does it play in human digestion?
The gut microbiota consists of microorganisms living in the human intestine. It helps break down otherwise indigestible food components, produces beneficial metabolites (e.g., SCFAs), and is suggested to influence overall health, metabolism, and immunity.
How is gut microbiota composition associated with obesity?
In obesity, there’s a decrease in Bacteroidetes and an increase in Firmicutes. This shift may allow greater energy harvest from food and contribute to weight gain. The gut microbiota in people with obesity tends to have increased metabolic efficiency.
What evidence from mice supports a link between gut microbiota and obesity?
In mouse studies, gut microbiota transplants from obese human twins caused recipient mice to gain weight, while transplants from lean twins did not. Co-housing mice allowed microbial exchange, and lean-associated microbes prevented weight gain in obese microbiota-recipient mice.
How does co-housing affect obesity-related microbiota in mice?
When mice colonized with obese microbiota are co-housed with mice colonized by lean microbiota, microbial transfer occurs, and lean microbes tend to dominate. This results in reduced weight gain in obese microbiota mice, demonstrating the transmissible effects of gut microbes.
How does a diet high in plant fiber affect gut microbiota and metabolic health?
A high-fiber diet promotes the growth of microbes that produce short-chain fatty acids (SCFAs), which improve insulin sensitivity, regulate appetite, and reduce inflammation. These microbes are associated with better metabolic health.
How does a diet high in animal fat impact gut microbiota and health?
High-fat, low-fiber diets encourage aberrant microbiota that produce harmful compounds (e.g., hydrogen sulfide, ammonia). These disrupt the intestinal environment, lower mucus secretion, and contribute to inflammation, metabolic dysfunction, and insulin resistance.
What are short-chain fatty acids (SCFAs), and what is their role in metabolism?
SCFAs, such as acetate, propionate, and butyrate, are produced by gut microbes fermenting dietary fibers. They stimulate gut hormone release, enhance insulin secretion, suppress appetite, and improve energy regulation and gut-brain communication.
How do SCFAs influence appetite through the gut-brain axis?
SCFAs stimulate enteroendocrine L-cells to release hormones like PYY and GLP-1, which signal the hypothalamus to suppress appetite. They also affect brain regions controlling reward and satiety, promoting reduced food intake and improved mood.
What is the gut-brain axis and how does it relate to microbiota?
The gut-brain axis is the bidirectional communication system between the gut and brain. Gut microbes influence brain activity via SCFA signaling, which affects neuronal activity, reward pathways, satiety, and long-term energy balance.
What are prebiotics, and how do they influence the gut microbiome?
Prebiotics are non-digestible dietary fibers that promote the growth of beneficial gut bacteria. They help increase the production of SCFAs and improve the microbial profile, supporting metabolic and immune health.
What are probiotics, and how might they improve gut health?
Probiotics are live microorganisms that, when ingested in adequate amounts, may modify the gut microbiota, enhance the balance of beneficial bacteria, and positively impact digestion, immune response, and metabolic outcomes.
How does fiber supplementation affect insulin sensitivity in people with metabolic syndrome?
In studies, low-fermentable fiber (LF) supplementation followed by fecal microbiota transplantation (FMT) significantly improved insulin sensitivity, showing fiber’s key role in modulating gut microbes and glucose metabolism.
What is the impact of a methyl donor deficient (MDD) diet on gut microbiota?
MDD diets in animal models led to reduced gut microbial diversity, underdeveloped gut structures (e.g., abnormal intestinal crypts), and low birth weights in offspring. Antibiotic suppression of folate-producing bacteria worsened these effects.
What is HOMA2 and how is it used in microbiome research?
HOMA2 (Homeostasis Model Assessment 2) estimates insulin sensitivity and beta-cell function using fasting glucose, insulin, and C-peptide levels. It helps assess metabolic changes in microbiome-related interventions.
What are some untargeted interventions that alter gut microbiota?
Untargeted interventions include exercise, dietary changes, probiotics, prebiotics, synbiotics, postbiotics, and fecal microbiota transplantation (FMT). These generally improve microbial diversity and function without targeting specific microbes.
What are targeted interventions for modifying gut microbiota?
argeted interventions include engineered commensal bacteria, microbial metabolism-targeting drugs, phage therapy, and CRISPR-Cas9 therapy. These aim to directly alter specific microbial populations or functions.
How does gut microbiota composition influence metabolic health?
Gut microbes impact adiposity, inflammation, insulin sensitivity, and glucose/lipid homeostasis through mechanisms such as energy harvest, immune interactions, and metabolite production (e.g., SCFAs, bile acids, LPS).
How do animal-based nutrients influence gut microbiota and disease risk?
Nutrients like L-carnitine and phosphatidylcholine from red meat promote production of compounds linked to atherosclerosis, inflammation, and fatty acid dysregulation, while excess amino acids can promote insulin resistance.
What is the relationship between gut microbial diversity and metabolic outcomes in mice?
Mice with more diverse microbiota (often from lean donors) exhibit leaner phenotypes and healthier metabolism. Transplanting lean microbes can prevent weight gain in obese-recipient mice, showing that microbial diversity promotes metabolic resilience.
Why is obesity considered a complex, multifactorial disease involving the microbiome?
Obesity arises from interactions between genetics, diet, behavior, environment, and the gut microbiota. Gut microbes contribute via energy harvest, hormonal regulation, and inflammatory signaling, making them both contributors to and potential therapeutic targets for obesity.
