Lingmin Tian

Effects of pectin supplementation on the fermentation patterns of different structural carbohydrates in rats

SCOPE We aimed to investigate and compare the effects of four types of pectins on dietary fiber (DF) fermentation, microbiota composition, and short chain fatty acid (SCFA) production throughout the large intestine in rats. METHODS AND RESULTS Male Wistar rats were given diets supplemented with or without 3% structurally different pectins for 7 weeks. Different fermentation patterns of pectins and different location of fermentation of pectin and diet arabinoxylans (AXs) in the large intestine were observed. During cecal fermentation, sugar beet pectin significantly stimulated Lactobacillus (p < 0.01) and Lachnospiraceae (p < 0.05). The stimulating effects of sugar beet pectin on these two groups of microbes are stronger than both other pectins. In the cecum, low-methyl esterified citrus pectin and complex soy pectin increased (p < 0.05) the production of total SCFAs, propionate and butyrate, whereas high-methyl esterified pectin and sugar beet pectin did not. The fermentation patterns of cereal AXs in the cecum were significantly different upon supplementation of different pectins. These differences, however, became smaller in the colon due to an enhanced fermentation of the remaining DFs. CONCLUSION Dietary supplementation of pectin is a potential strategy to modulate the location of fermentation of DFs, and consequently microbiota composition and SCFA production for health-promoting effects.

Effects of pectin on fermentation characteristics, carbohydrate utilization and microbial community composition in the gastrointestinal tract of weaning pigs

SCOPE We aimed to investigate the effects of three different soluble pectins on the digestion of other consumed carbohydrates, and the consequent alterations of microbiota composition and SCFA levels in the intestine of pigs. METHODS AND RESULTS Piglets were fed a low-methyl esterified pectin enriched diet (LMP), a high-methyl esterified pectin enriched diet (HMP), a hydrothermal treated soybean meal enriched diet (aSBM) or a control diet (CONT). LMP significantly decreased the ileal digestibility of starch resulting in more starch fermentation in the proximal colon. In the ileum, low-methyl esterified pectin present was more efficiently fermented by the microbiota than high-methyl esterified pectin present which was mainly fermented by the microbiota in the proximal colon. Treated soybean meal was mainly fermented in the proximal colon and shifted the fermentation of cereal dietary fiber to more distal parts, resulting in high SCFA levels in the mid colon. LMP, HMP, and aSBM decreased the relative abundance of the genus Lactobacillus and increased that of Prevotella in the colon. CONCLUSION The LMP, HMP, and aSBM, differently affected the digestion processes compared to the control diet and shaped the colonic microbiota from a Lactobacillus-dominating flora to a Prevotella-dominating community, with potential health-promoting effects.

Characterization of (Glucurono)arabinoxylans from Oats Using Enzymatic Fingerprinting

Cell wall material from whole oat grains was sequentially extracted to study the structural characteristics of individual arabinoxylan (AX) populations. Araf was singly substituted at both O-3 (mainly) and O-2 positions of Xylp, and no disubstitution of Xylp with Araf residues was found in oat AXs. Both highly substituted and sparsely substituted segments were found in AXs in Ba(OH)2 extracts, whereas AXs in 1 and 6 M NaOH extracts were rarely branched and easily aggregated. Both O-2-linked GlcA and 4-O-MeGlcA residues were present in oat AXs. A series of AX oligomers with galactose as a substituent was detected for the first time in oats. The present study suggested that the distribution of Araf was contiguous in oat AXs, different from the homogeneous distribution of Araf in wheat and barley AXs, which might result in different fermentation patterns in humans and animals.

Dietary Fiber Pectin Directly Blocks Toll-Like Receptor 2–1 and Prevents Doxorubicin-Induced Ileitis

Dietary carbohydrate fibers are known to prevent immunological diseases common in Western countries such as allergy and asthma but the underlying mechanisms are largely unknown. Until now beneficial effects of dietary fibers are mainly attributed to fermentation products of the fibers such as anti-inflammatory short-chain fatty acids (SCFAs). Here, we found and present a new mechanism by which dietary fibers can be anti-inflammatory: a commonly consumed fiber, pectin, blocks innate immune receptors. We show that pectin binds and inhibits, toll-like receptor 2 (TLR2) and specifically inhibits the proinflammatory TLR2–TLR1 pathway while the tolerogenic TLR2–TLR6 pathway remains unaltered. This effect is most pronounced with pectins having a low degree of methyl esterification (DM). Low-DM pectin interacts with TLR2 through electrostatic forces between non-esterified galacturonic acids on the pectin and positive charges on the TLR2 ectodomain, as confirmed by testing pectin binding on mutated TLR2. The anti-inflammatory effect of low-DM pectins was first studied in human dendritic cells and mouse macrophages in vitro and was subsequently tested in vivo in TLR2-dependent ileitis in a mouse model. In these mice, ileitis was prevented by pectin administration. Protective effects were shown to be TLR2–TLR1 dependent and independent of the SCFAs produced by the gut microbiota. These data suggest that low-DM pectins as a source of dietary fiber can reduce inflammation through direct interaction with TLR2–TLR1 receptors.