FP - Gut Microbiome and Diet

Question 1

How do dietary habits and lifestyles affect gut microbiome composition? (2)

Answer 1

• Changes in diet, especially in Western populations, have altered gut microbiomes.
• Bantu populations show intermediate microbiota between hunter-gatherers (Baaka) and Americans, reflecting a shift towards more modern lifestyles.

Question 2

What are the key differences between traditional diets (3) and industrialized diets (3) on the gut microbiome?

Answer 2

Traditional Diets:

• Higher abundance of Prevotellaceae, Treponema, Clostridiaceae
• Increased production of vitamins, amino acids, and virulence factors
• Lower intake of carbohydrates and exposure to xenobiotics

Industrialized Diets:

• Decreased abundance of Prevotellaceae and Treponema
• Reduced beneficial bacterial functions (e.g., vitamin synthesis)
• Increased exposure to xenobiotics and processed carbohydrates

Question 3

How do hunter-gatherer and industrialized populations differ in gut microbiome enzyme functions?

Answer 3

Hunter-Gatherers: Enzymes for breaking down complex plant polysaccharides, indicating a fiber-rich diet

Industrialized Populations: Enzymes for degrading xenobiotics, amino acids, and bile acids, suggesting a diet high in processed foods and animal protein

Question 4

How do short-term dietary interventions affect the gut microbiome?

Answer 4

Plant-Based Diet:

• Increases fiber intake but does not change microbial diversity

Animal-Based Diet:

• Increases bile-tolerant microorganisms, decreases plant polysaccharide metabolizers, and increases microbial diversity

Question 5

What are the characteristics of Agrarian (3) and Western diets (3), and their effects on the gut microbiome?

Answer 5

Agrarian Diet:

• Characteristics: High in fiber, low in fat and protein.
• Gut Microbiome: Dominated by Prevotella, Faecalibacterium, Lachnospira, Roseburia, and Eubacterium.
• Metabolic Products: Increased production of short-chain fatty acids (SCFAs) and equol (from phytochemicals).

Western Diet:

• Characteristics: Low in fiber, high in fat and protein.
• Gut Microbiome: Dominated by Bacteroides, Alistipes, and Bilophila.
• Metabolic Products: Increased production of trimethylamine N-oxide (TMAO), indoles, P-cresol, and hydrogen sulfide (H2S).

Question 6

What happens to dietary fiber in the gut, and which microbes are involved in its fermentation?

Answer 6

Dietary Fiber: Polysaccharides (complex sugars) from plant-based foods

• Depolymerized by gut microbes into oligo- and monosaccharides

Gut Microbe Fermentation:

• Prevotella: Produces acetate and propionate
• Firmicutes (e.g., Lachnospira, Roseburia, Clostridium, Eubacterium): Produce butyrate

Question 7

What are short-chain fatty acids (SCFAs) and their benefits (4) ?

Answer 7

Acetate, butyrate, and propionate (3:1:1 ratio)

Benefits:

• Neuroprotective effects
• Reduced inflammation
• Anticarcinogenic properties
• Contribute up to 10% of daily energy intake

Question 8

Which diets are linked to a higher production of SCFAs?

Answer 8

Fiber-rich diets are linked to higher production of short-chain fatty acids

Question 9

What are phytochemicals, and where are they found? (2)

Answer 9

Phytochemicals: Complex micronutrients found in plant cell walls

Examples: Polyphenols (e.g., flavanols, tannins, soy isoflavones) present in grains, fruits, and vegetables

Question 10

What happens to phytochemicals in the colon, and what are the effects of their transformation? (3)

Answer 10

• Conversion: Gut microbiota convert phytochemicals into bioactive molecules
• Example: Daidzein (from soy) is converted to equol by Slackia isoflavoniconvertens
• Health Benefits of Equol: Anti-inflammatory and anticarcinogenic effects

Question 11

How do phytochemicals affect the gut microbiome? (3)

Answer 11

Phytochemicals increase gut microbiome diversity by promoting the growth of beneficial bacteria

Examples:

• Lactobacillus and Bifidobacterium are supported by phytochemicals
• Cocoa-derived flavanols can boost the abundance of these bacteria

Question 12

What happens to undigested protein in the gut? (2)

Answer 12

• 5-10% of undigested protein reaches the large intestine.
• Proteolysis breaks down protein into peptides, then into amino acids.

Question 13

What happens during the fermentation of amino acids in the gut, and what are the effects? (4)

Answer 13

• Aromatic amino acids: Fermented into phenylacetic acid, phenols, and para-cresol by Bacteroides. These compounds are pro-inflammatory and carcinogenic.
• Branched-chain amino acids: Fermented into isovalerate and isobutyrate, which have been linked to insulin resistance and diabetes.
• Sulfur-containing amino acids: Catabolized into hydrogen sulfide (H2S) by sulfate-reducing bacteria (Desulfovibrio, Bilophila). H2S can contribute to gut inflammation and oxidative stress.
• Other amino acids: Can be further fermented into amines, which can react with nitrates to form N-nitroso compounds (NOCs), known carcinogens.

Question 14

How does the gut microbiome metabolize L-carnitine, and what are the health implications? (3)

Answer 14

• Gut microbes convert L-carnitine into trimethylamine (TMA)
• TMA is processed by the liver into trimethylamine-N-oxide (TMAO)
• TMAO is linked to an increased risk of cardiovascular diseases due to its role in promoting atherosclerosis (plaque buildup in arteries)

Question 15

How can diet influence health and the gut microbiome, particularly in glucose response? (4)

Answer 15

• High variability in post-meal glucose responses observed in an 800-person cohort
• Correlation between microbial genes/functions and post-meal response to diets
• Anthropometrics and microbiome features enable accurate prediction of glucose responses
• Microbiota can help design personalized diets to achieve desired health effects