Combinations of Indigestible Carbohydrates Affect Short-Chain Fatty Acid Formation in the Hindgut of Rats

Abstract

The fermentability and pattern of short-chain fatty acids (SCFA) formed in the hindgut of rats given various combinations of dietary fibers (DF) and resistant starch (RS) were investigated. Highly fermentable indigestible carbohydrates, i.e., guar gum (GG), pectin (Pec) and high amylose cornstarch (HAS), and a DF with a relatively high resistance to fermentation, i.e., wheat bran (WB), were included. The substrates were studied individually or as mixtures (GG + Pec, GG + WB and HAS + WB, 1:1, wt/wt indigestible carbohydrate basis) at a total concentration of 100 g indigestible carbohydrates/kg diet and fed to rats for 13 d. Rats fed Pec had a high proportion of acetic acid in the cecum (76 +/- 2% of total SCFA), whereas those fed GG had the highest proportion of propionic acid (31 +/- 4%, P <0.0005). Rats fed GG and Pec had low proportions of butyric acid (6 +/- 1 and 10 +/- 1%, respectively), whereas those fed both had a higher proportion of butyric acid (15 +/- 3%, P < 0.05). Consequently, the cecal butyric acid pool was twice as high in rats fed the GG + Pec mixture (44 +/- 9 micro mol) as in those fed the individual components (19 +/- 2 and 21 +/- 3 micro mol, respectively, P < 0.05). Rats fed HAS with WB had a greater fecal excretion of SCFA (184 +/- 19 micro mol/d) than those fed the individual components (77 +/- 10 and 116 +/- 12 micro mol/d in rats fed HAS and WB, respectively P < 0.05), suggesting that incorporation of WB delayed the site of fermentation of HAS to the distal part of the hindgut. In conclusion, the combination of indigestible carbohydrates may affect both SCFA patterns and the site of SCFA release in the rat hindgut.

Dietary supplementation with β-glucan enriched oat bran increases faecal concentration of carboxylic acids in healthy subjects

“…One may speculate whether a combination with wheat bran will increase the distal and/or faecal concentrations of CAs. Studies in rats have shown that by combining a highly fermentable type of resistant starch with the more resistant wheat bran shifted the fermentation and release of CAs to the distal part of colon (Henningsson et al, 2002).…”

“…Different types of indigestible carbohydrates give rise to different amounts and patterns of CAs during colonic fermentation, and it may therefore be possible to regulate the CA formation by diet. The CAs formed may depend on for example the monomeric composition of the carbohydrates, the type of linkages between the carbohydrate monomers, their solubility and their molecular weight (Berggren et al, 1993;Casterline et al, 1997;Bird et al, 2000;Karppinen et al, 2000;Henningsson et al, 2002Henningsson et al, , 2003Nilsson and Nyman, 2005). Studies examining CA formation have mainly been conducted in vitro by using human faecal inocula, or in vivo using animal models.…”

“…Studies examining CA formation have mainly been conducted in vitro by using human faecal inocula, or in vivo using animal models. The rat is the most common model when studying the CA formation in vivo, although there are also some studies available in pigs (Berggren et al, 1993;Roland et al, 1995;Brown et al, 1997;Djouzi and Andrieux, 1997;Bird et al, 2000;Henningsson et al, 2002Henningsson et al, , 2003Nilsson and Nyman, 2005). Studies in man have mainly been performed by measurements of CAs in faeces and have been questioned on the premises that such measurements do not give information regarding the formation of CAs in proximal colon where most of the fermentation actually takes place.…”

Transfer of blood urea nitrogen to cecal microbial nitrogen is increased by mannitol feeding in growing rabbits fed timothy hay diet

“…It is well documented that fermentable carbohydrates can increase urea flux from the blood to the digestive tract and alter fermentation in the large intestine of rats (Ré mé sy and Demigné, 1989;Younes et al, 1995b;Henningsson et al, 2002). In rabbits, a considerable portion of endogenous urea is transferred to the alimentary tract (Regoeczi et al, 1965), and the exchange between blood urea nitrogen (N) and cecal ammonia N is well established Parker, 1985a and1985b).…”

Influence of the type of indigestible carbohydrate on plasma and urine short-chain fatty acid profiles in healthy human volunteers

“…Similarly, the type of indigestible carbohydrate consumed was found to influence the distribution of SCFA in the hindgut of rats (Henningsson et al, 2002) and pigs (Bird et al, 2004).…”