Group items tagged

Gut bacteria in the cecum and large intestine produce SCFAs mainly from nondigestible carbohydrates that pass the small intestine unaffected

plant cell-wall polysaccharides, oligosaccharides, and resistant starches

inulin shifted the relative production of SCFAs from acetate to propionate and butyrate

age of approximately 3–4 years, when it becomes mature

SCFAs affect lipid, glucose, and cholesterol metabolism

colonocytes, the first host cells that take up SCFAs and which depend largely on butyrate for their energy supply

the microbiota educate the immune system and increase the tolerance to microbial immunodeterminants

the microbiota act as a metabolic organ that can break down otherwise indigestible food components, degrade potentially toxic food compounds like oxalate, and synthesize certain vitamins and amino acids

a large part of the SCFAs is used as a source of energy

The general idea is that colonocytes prefer butyrate to acetate and propionate, and oxidize it to ketone bodies and CO2

Exogenous acetate formed by colonic bacterial fermentation enters the blood compartment and is mixed with endogenous acetate released by tissues and organs (103, 104). Up to 70% of the acetate is taken up by the liver (105), where it is not only used as an energy source, but is also used as a substrate for the synthesis of cholesterol and long-chain fatty acids and as a cosubstrate for glutamine and glutamate synthesis

SCFAs regulate the balance between fatty acid synthesis, fatty acid oxidation, and lipolysis in the body.

Fatty acid oxidation is activated by SCFAs, while de novo synthesis and lipolysis are inhibited

obese animals in this study showed a 50% reduction in relative abundance of the Bacteroidetes (i.e., acetate and propionate producers), whereas the Firmicutes (i.e., butyrate producers) were proportionally increased compared with the lean counterparts.

increase in total fecal SCFA concentrations in obese humans.

In humans the distinct relation between the Firmicutes:Bacteroidetes ratio and obesity is less clear.

complex functional interactions between diet, gut microbiota, and host health.

probiotic supplementation in women with GDM was associated with significant reductions in insulin resistance

One proposed method is by the production of short chain fatty acids (SCFAs), generated as a by-product of bacterial fermentation of dietary fibers. SCFAs act as an energy source for intestinal cells and have been found to regulate the production of hormones effecting energy intake and expenditure such as leptin and grehlin

Another hypothesized mechanism of SCFA action includes reducing gastrointestinal permeability by upregulating transcription of tight junction proteins, enhancing production of Glucagon-like peptide-2 (GLP-2) which promotes crypt cell proliferation, and reducing inflammation in colonic epithelial cells by increasing PPAR-gamma activation

Maintenance of the integrity of the gut barrier minimizes the concentration of lipopolysaccharide (LPS) in circulation

LPS is a structural component of gram negative bacterial cell walls, which induces an immune-cell response upon absorption into the human bloodstream, stimulating proinflammatory cytokine production and the onset of insulin resistance and hyperglycemia

n increased intake of total DF was inversely associated with markers of insulin resistance in several studies

consumption of insoluble DF increased whole body glucose disposal independent of changes in body weight in both short-term and more prolonged studies

Short-chain fatty acids (SCFA) such as acetate, propionate, and butyrate are produced by bacterial fermentation of indigestible DF polysaccharides in the colon

increased production of SCFA is assumed to be beneficial by reducing hepatic glucose output and improving lipid homeostasis

a high DF diet (oligofructose) reduced gram-negative bacterial content and body weight, whereas a high fat diet increased the proportion of a gram-negative bacterial lipopolysaccharides (LPS) containing microbiota in humans

Prospective cohort studies indicate that diets high in insoluble cereal DF and whole grains might reduce diabetes risk

soluble DF (i.e., pectin, inulin, and β-glucans)

cereal DF (i.e., cellulose and hemicelluloses)