Dietary Fiber and Coronary Heart Disease
Robert E.C. Wildman, Richard S. Bruno in Handbook of Nutraceuticals and Functional Foods, 2019
Digestible polysaccharides in plant foods, such as starch, and to a much lesser degree glycogen in meats, have repeating monosaccharide units bonded by 1–4 linkages (Figure 10.1). These bonds are readily digested by amylase in both salivary and pancreatic secretions. Branch points in the starch and glycogen chains are joined through 1–6 linkages that are hydrolyzed by the enzyme 1–6 dextrinase (isomaltase) in pancreatic secretions. On the contrary, 1–4 linkages are formed by plants between monosaccharides in fibrous polysaccharides (Figure 10.1). Both salivary and pancreatic amylases are unable to hydrolyze 1–4 covalent bonds efficiently. This renders such polysaccharides resistant to human digestive action. However, bacteria inhabiting the large intestine can indeed metabolize some polysaccharide fiber and create short-chain fatty acids (acetic, propionic, and butyric acids) as metabolites. Table 10.4 summarizes the fermentation of common types of fiber. These short-chain fatty acids are now being recognized to have important roles in mediating diverse metabolic effects that impact inflammation, immune function, and gut health. A review of these effects is outside the scope of this chapter, but there are many excellent reviews on this topic available that have been published in the last few years.
Participation of Vagal Sensory Neurons in Putative Satiety Signals from the Upper Gastrointestinal Tract
Sue Ritter, Robert C. Ritter, Charles D. Barnes in Neuroanatomy and Physiology of Abdominal Vagal Afferents, 2020
With regard to chemical stimulation of the intestine, a variety of nutrient- related responses have been observed. Mei51 has reported afferent fibers that increase their firing rate in response to intraluminal oligosaccharides, especially glucose. Likewise, hindbrain neurons that receive afferent vagal projections also respond to intestinal glucose infusion.24 Jeanningros44 has reported intestinal afferents that respond rather selectively to amino acids. Although a few of these units also responded to glucose, they were not responsive to osmotic or mechanical stimuli. Vagal afferents responding to fatty acids have been recorded by Melone.52 The fatty acid response is greater to long-chain than short- chain fatty acids and is not mimicked by other organic acids or mineral acids.
Effect of Short-Chain Fatty Acids Produced by Probiotics
Marcela Albuquerque Cavalcanti de Albuquerque, Alejandra de Moreno de LeBlanc, Jean Guy LeBlanc, Raquel Bedani in Lactic Acid Bacteria, 2020
An overview of the literature published over the last five years up to the end of December 2018 has shown an increase in the contributions related to “short chain fatty acids and probiotics and human health”, with no less than 2955 scientific articles (based on Science Direct search: http://www.sciencedirect.com). A substantial portion of them deals with “short chain fatty acids and probiotic lactic acid bacteria and human health” (1269 scientific articles); thus, this topic is an active and expanding field of research. Owing to the biological significance of SCFAs, recent advances have been made in the development of rapid and selective analytical methods capable of identifying and quantifying them especially in human faecal samples (Primec et al. 2019), which are summarized in Table 1. Readers are directed elsewhere for a comprehensive review of the SCFAs analysis in human faeces (Primec et al. 2017). On the other hand, Table 2 summarizes the more recent examples of current scientific reports on the functional role of SCFAs produced by probiotic bacteria in the improvement of human health.
Stool Short-Chain Fatty Acids in Critically Ill Patients with Sepsis
Published in Journal of the American College of Nutrition, 2020
Beatriz E. Valdés-Duque, Nubia A. Giraldo-Giraldo, Ana M. Jaillier-Ramírez, Adriana Giraldo-Villa, Irene Acevedo-Castaño, Mónica A. Yepes-Molina, Janeth Barbosa-Barbosa, Carlos J. Barrera-Causil, Gloria M. Agudelo-Ochoa
Short-chain fatty acids (SCFAs) are compounds with two to six carbon atoms in their structure. SFCAs play a key role in promoting intestinal barrier integrity. The main SCFAs include acetic (C2), propionic (C3), and butyric (C4) acids. Although they are naturally produced by host metabolic pathways, they are mainly synthesized in the colon due to polysaccharide fermentation by anaerobic bacteria (1). In the intestinal lumen, SCFAs are found in different concentrations depending on the site; 13 mM SCFAs are found in the terminal ileum, 130 mM in the cecum, and 80 mM in the descending colon (2). SCFA concentration is variable, and its production is regulated by factors related to the host, environment, diet, substrate availability, and microbiological conditions such as the metabolic capacity of the gut intestinal microbiota (IM). In healthy individuals, the molar proportion of acetic, propionic, and butyric acids is 60:25:15 and remains relatively stable over time (3, 4).
Fatty acids produced by the gut microbiota dampen host inflammatory responses by modulating intestinal SUMOylation
Published in Gut Microbes, 2022
Chaima Ezzine, Léa Loison, Nadine Montbrion, Christine Bôle-Feysot, Pierre Déchelotte, Moïse Coëffier, David Ribet
The gut microbiota produces a wide variety of metabolites diffusing to the intestinal mucosa and modulating intestinal cell activities.1 Some of these metabolites may even cross the intestinal barrier and reach distant organs via the bloodstream or via nerve communications. Fatty acids constitute a major class of metabolites produced by intestinal bacteria. They include the so-called Short Chain Fatty Acids (SCFAs), which are carboxylic acids with aliphatic tails of one to six carbons.2 Acetate, butyrate, and propionate are the main SCFAs produced in the human colon and derive mostly from the anaerobic catabolism of dietary fibers by intestinal bacteria.3,4 Branched Chain Fatty Acids (BCFAs), such as isobutyrate, isovalerate, or 2-methylbutyrate, constitute another class of fatty acids produced by bacteria with one or more methyl branches on the carbon chain. BCFA mostly derives from the breakdown of proteins by intestinal bacteria and more particularly from the catabolism of branched-chain amino-acids (valine, leucine, and isoleucine, producing isobutyrate, isovalerate, or 2-methylbutyrate, respectively).5
Bugs in the system: bringing the human microbiome to bear in cancer immunotherapy
Published in Gut Microbes, 2019
Christopher Strouse, Ashutosh Mangalam, Jun Zhang
Beyond considering these other niches, analytic techniques other than 16S rRNA sequencing may be necessary to capture the full breadth of the interaction between microbial communities and the immune system. Products of microbial metabolism are known to modulate immune responses. Short chain fatty acids, produced by gut microbiota from insoluble fiber, are one such example. They have been shown to modulate pulmonary immune responses, affecting patients’ allergic airway disease.15 The regulatory T cell pool is modulated by short chain fatty acids via a G protein-coupled receptor mechanism, offering a molecular explanation for this association.16 Characterization of the bacterial microbiome via 16S rRNA sequencing may fail to identify relevant variations in these and other bacterial metabolites.
Related Knowledge Centers
- Atom
- Dietary Fiber
- Fatty Acid
- Fermentation
- Gastrointestinal Tract
- Digestion
- Carbon
- Large Intestine
- Medium-Chain Triglyceride
- Portal Vein