Dose-dependent effects of a soluble dietary fibre (pectin) on food intake, adiposity, gut hypertrophy and gut satiety hormone secretion in rats

Abstract

Soluble fermentable dietary fibre elicits gut adaptations, increases satiety and potentially offers a natural sustainable means of body weight regulation. Here we aimed to quantify physiological responses to graded intakes of a specific dietary fibre (pectin) in an animal model. Four isocaloric semi-purified diets containing 0, 3.3%, 6.7% or 10% w/w apple pectin were offered ad libitum for 8 or 28 days to young adult male rats (n = 8/group). Measurements were made of voluntary food intake, body weight, initial and final body composition by magnetic resonance imaging, final gut regional weights and histology, and final plasma satiety hormone concentrations. In both 8- and 28-day cohorts, dietary pectin inclusion rate was negatively correlated with food intake, body weight gain and the change in body fat mass, with no effect on lean mass gain. In both cohorts, pectin had no effect on stomach weight but pectin inclusion rate was positively correlated with weights and lengths of small intestine and caecum, jejunum villus height and crypt depth, ileum crypt depth, and plasma total glucagon-like peptide-1 (GLP-1) and peptide tyrosine tyrosine (PYY) concentrations, and at 8 days was correlated with weight and length of colon and with caecal mucosal depth. Therefore, the gut's morphological and endocrine adaptations were dose-dependent, occurred within 8 days and were largely sustained for 28 days during continued dietary intervention. Increasing amounts of the soluble fermentable fibre pectin in the diet proportionately decreased food intake, body weight gain and body fat content, associated with proportionately increased satiety hormones GLP-1 and PYY and intestinal hypertrophy, supporting a role for soluble dietary fibre-induced satiety in healthy body weight regulation.

Figure 1. Food intake.

Daily (a, b) and cumulative (c, d) voluntary food intake by rats offered control diet (C) or diet containing 3, 7 or 10% pectin (P) for 8 days (a, c) or 28 days (b, d), and correlation between cumulative intake and amount of P in the diet in 8-day (e) and 28-day (f) cohorts. Results of repeated measures ANOVA are indicated in figures a and b. Columns labelled with different letters in figures c and d are significantly different by one-way ANOVA, P<0.05, and r is the Pearson product-moment correlation coefficient in figs e and f, ***P<0.001.

Figure 2. Body weight.

Changes in body weight in rats offered control diet (C) or diet containing 3, 7 or 10% pectin (P) for 8 days (a, c) or 28 days (b, d). Results of repeated measures ANOVA are indicated in fig b. Within figures c and d, columns labelled with different letters are significantly different by one-way ANOVA, P<0.05.

Figure 3. Body composition (by MRI).

Changes in total lean tissue mass (a, b) and total fat mass (c, d), correlation between change in body fat mass and amount of pectin in the diet (e, f), final total body lean tissue percentage (g, h), and final total body fat percentage (i, j) in rats offered control diet (C) or diet containing 3, 7 or 10% pectin (P) for 8 days (a, c, e, g, i) or 28 days (b, d, f, h, j). Within figures, columns labelled with different letters are significantly different by one-way ANOVA, P<0.05, and r is the Pearson product-moment correlation coefficient, ***P<0.001.

Figure 4. Satiety hormones.

Plasma concentrations of PYY (a, c) and total GLP-1 (e, g) in rats offered control diet (C) or diet containing 3, 7 or 10% pectin (P) for 8 days (a, e) or 28 days (c, g); and correlations between amount of pectin in the diet and PYY and total GLP-1 concentrations in the 8-day (b, f) and 28-day (d, h) cohorts. Within figures, columns labelled with different letters are significantly different by one-way ANOVA, P<0.05, and r is the Pearson product-moment correlation coefficient, ***P<0.001.