Resistant starch and arabinoxylan augment SCFA absorption, but affect postprandial glucose and insulin responses differently

Abstract

The effects of increased colonic fermentation of dietary fibres (DF) on the net portal flux (NPF) of carbohydrate-derived metabolites (glucose, SCFA and, especially, butyrate), hormones (insulin, C-peptide, glucagon-like peptide 1 and glucose-dependent insulinotropic peptide) and NEFA were studied in a healthy catheterised pig model. A total of six pigs weighing 59 (SEM 1·6) kg were fitted with catheters in the mesenteric artery and in the portal and hepatic veins, and a flow probe around the portal vein, and included in a double 3 £ 3 cross-over design with three daily feedings (at 09.00, 14.00 and 19.00 hours). Fasting and 5 h postprandial blood samples were collected after 7 d adaptation to each diet. The pigs were fed a low-DF Western-style control diet (WSD) and two high-DF diets (an arabinoxylan-enriched diet (AXD) and a resistant starch-enriched diet (RSD)). The NPF of insulin was lower (P¼ 0·04) in AXD-fed pigs (4·6 nmol/h) than in RSD-fed pigs (10·5 nmol/h), despite the lowest NPF of glucose being observed in RSD-fed pigs (203 mmol/h, P¼ 0·02). The NPF of total SCFA, acetate, propionate and butyrate were high, intermediate and low (P, 0·01) in AXD-, RSD-and WSD-fed pigs, respectively, with the largest relative increase being observed for butyrate in response to arabinoxylan supplementation. In conclusion, the RSD and AXD had different effects on the NPF of insulin and glucose, suggesting different impacts of arabinoxylan and resistant starch on human health.

Microbial Degradation of Whole-Grain Complex Carbohydrates and Impact on Short-Chain Fatty Acids and Health

“…In contrast to these findings, studies in rats and pigs fed an arabinoxylan-rich fraction from wheat did not specifically show enhanced butyrate but only total SCFA production (49,50). The reasons for this difference in butyrate response between these 2 sets of experiments cannot be determined by any certainty but may be related to the way the arabinoxylans was provided, as a concentrate from wheat (49,50) or as part of a whole-grain matrix (27,47,48). The fermentation of the arabinoxylan concentrate can be expected to be rapid, as indicated by the results in references 49 and 50, and with a decrease in pH mainly in the cecum (48), whereas the fermentation of arabinoxylans from a whole-grain matrix will be slower, with a decrease in pH not only in the cecum but also in the proximal colon (28).…”

“…An arabinoxylan-rich cereal-based diet was found to stimulate the proliferation of butyrate-producing microorganisms (i.e., F. pausnitzii, Roseburia intestinalis) (46), butyrate production in the large intestine (47), and the net portal absorption of butyrate (48) to a larger extent than a diet with equal amounts of DF in the form of RS (Table 2). A Western-style diet high in refined carbohydrates from sugar and refined wheat flour was used as a reference diet (47,48). In contrast to these findings, studies in rats and pigs fed an arabinoxylan-rich fraction from wheat did not specifically show enhanced butyrate but only total SCFA production (49,50).…”

Obese Mice Fed a Diet Supplemented with Enzyme-Treated Wheat Bran Display Marked Shifts in the Liver Metabolome Concurrent with Altered Gut Bacteria

“…Mass spectra were acquired on a Leco Pegasus IV time-of-flight mass spectrometer with a 280°C transfer line, a 250°C ion source, and 270 eV electron ionization impact. The acquisition rate was 17 spectra s 21 with a scan mass range of 85-500 Da. Result files were exported to servers and processed by the Fiehn laboratoryÕs metabolomics database, known as BinBase (33).…”

“…Therefore, we set out to characterize how the consumption of the dietary fiber enzymetreated wheat bran (ETWB) alters the gut microbiota and liver metabolome. ETWB is made by treating wheat bran with heat and enzymes, resulting in a mixture of arabinoxylan oligosaccharides (AXOSs), high-molecular weight arabinoxylans, cellulose, and lignin (21). The treated wheat bran is more prone to bacterial degradation than is wheat bran in its native form (18,19).…”

“…The treated wheat bran is more prone to bacterial degradation than is wheat bran in its native form (18,19). Human and animal studies have shown that the consumption of ETWB can alter the gut microbiota, reduce body fat, and improve glucose and insulin homeostasis (21). However, there is a paucity of information with regard to what effects ETWB has on the liver, a major organ in terms of whole-body metabolic homeostasis.…”