The role of viscosity and fermentability of dietary fibers on satiety- and adiposity-related hormones in rats

Abstract

Dietary fiber may contribute to satiety. This study examined the effect of two dietary fiber characteristics, small intestinal contents viscosity and large intestinal fermentability, on satiety-and adiposity-related hormones in rats. Diets contained fiber sources that were non-viscous, somewhat viscous, or highly viscous, and either highly fermentable or non-fermentable, in a 2 × 3 factorial design. In the fed state (2 h postprandial), rats fed non-fermentable fibers had significantly greater plasma GLP-1 concentration than fermentable fibers. In the fasted state, among non-fermentable fibers, viscosity had no effect on GLP-1 concentration. However, among fermentable fibers, greater viscosity reduced GLP-1 concentration. Plasma peptide tyrosine tyrosine (PYY) concentrations in the fasted state were not influenced by the fermentability of the fiber overall, however animals consuming a fructooligosaccharide greater PYY concentration. In both the fed and fasted states, rats fed non-fermentable fibers had a significantly lower plasma ghrelin concentration than rats fed fermentable fibers. In the fasted state, rats fed non-fermentable fibers had a significantly lower plasma leptin concentration than rats fed fermentable fibers. Thus, fermentability and viscosity of dietary fiber interacted in complex ways to influence satiety- and adiposity-related plasma hormone concentrations. However, the results suggest that highly viscous, non-fermentable fibers may limit weight gain and reduce adiposity and non-fermentable fibers, regardless of viscosity, may promote meal termination.

Figure 1

Dietary fiber types used in the experimental diets to produce a range of intestinal viscosities, with or without large intestinal fermentation. Each fiber type was present in the diets at 5%.

Figure 2

Effect of dietary fiber viscosity and fermentability on plasma GLP-1 concentrations in the fasted state (A) and fed state (B). Values are mean ± SEM, n = 10–12 per group. Bars having different letters differ significantly (p < 0.05). In the fasted state, there was a significant viscosity by fermentability interaction (p = 0.041). In the fed state, there was a significant main effect of fermentability (p = 0.021). The non-fermentable fibers, in order of increasing viscosity were cellulose, LV-HPMC, and HV-HPMC. The fermentable fibers, in order of increasing viscosity, were scFOS, scFOS + RS, and βG.

Figure 3

Effect of dietary fiber viscosity and fermentability on plasma ghrelin concentrations in the fasted state (A) and fed state (B). Values are mean ± SEM, n = 10–12 per group. Bars having different letters differ significantly (p < 0.05). In the fasted state, there was a significant main effect of fermentability (p = 0.001). In the fed state there was also a significant main effect of fermentability (p = 0.006). The non-fermentable fibers, in order of increasing viscosity were cellulose, LV-HPMC, and HV-HPMC. The fermentable fibers, in order of increasing viscosity, were scFOS, scFOS + RS, and βG.

Figure 4

Effect of dietary fiber viscosity and fermentability on plasma PYY concentrations in the fasted state. Values are mean ± SEM, n = 10–12 per group. Bars having different letters differ significantly (p < 0.05). There was a significant viscosity by fermentability interaction (p =\ 0.001). The non-fermentable fibers, in order of increasing viscosity were cellulose, LV-HPMC, and HV-HPMC. The fermentable fibers, in order of increasing viscosity, were scFOS, scFOS + RS, and βG.

Figure 5

Effect of dietary fiber viscosity and fermentability on plasma leptin concentrations in the fasted state (A) and fed state (B). Values are mean ± SEM, n = 10–12 per group. Bars having different letters differ significantly (p < 0.05). In the fasted state, there was a significant main effect of fermentability (p = 0.027). In the fed state, there were no significant main effects of fermentation or viscosity. The non-fermentable fibers, in order of increasing viscosity were cellulose, LV-HPMC, and HV-HPMC. The fermentable fibers, in order of increasing viscosity, were scFOS, scFOS + RS, and βG.

Figure 6

Effect of dietary fiber viscosity and fermentability on plasma insulin concentration in the fasted state (A) and fed state (B). Values are mean ± SEM, n = 10–12 per group. Bars having different letters differ significantly (p < 0.05). There were no significant main effects of fermentation or viscosity in either the fasted or fed states. The non-fermentable fibers, in order of increasing viscosity were cellulose, LV-HPMC, and HV-HPMC. The fermentable fibers, in order of increasing viscosity, were scFOS, scFOS + RS, and βG.