Prebiotics Supplementation Impact on the Reinforcing and Motivational Aspect of Feeding

Abstract

Energy homeostasis is tightly regulated by the central nervous system which responds to nervous and circulating inputs to adapt food intake and energy expenditure. However, the rewarding and motivational aspect of food is tightly dependent of dopamine (DA) release in mesocorticolimbic (MCL) system and could be operant in uncontrolled caloric intake and obesity. Accumulating evidence indicate that manipulating the microbiota-gut-brain axis through prebiotic supplementation can have beneficial impact of the host appetite and body weight. However, the consequences of manipulating the implication of the microbiota-gut-brain axis in the control motivational and hedonic/reinforcing aspects of food are still underexplored. In this study, we investigate whether and how dietary prebiotic fructo-oligosaccharides (FOS) could oppose, or revert, the change in hedonic and homeostatic control of feeding occurring after a 2-months exposure to high-fat high-sugar (HFHS) diet. The reinforcing and motivational components of food reward were assessed using a two-food choice paradigm and a food operant behavioral test in mice exposed to FOS either during or after HFHS exposure. We also performed mRNA expression analysis for key genes involved in limbic and hypothalamic control of feeding. We show in a preventive-like approach, FOS addition of HFHS diet had beneficial impact of hypothalamic neuropeptides, and decreased the operant performance for food but only after an overnight fast while it did not prevent the imbalance in mesolimbic markers for DA signaling induced by palatable diet exposure nor the spontaneous tropism for palatable food when given the choice. However, when FOS was added to control diet after chronic HFHS exposure, although it did not significantly alter body weight loss, it greatly decreased palatable food tropism and consumption and was associated with normalization of MCL markers for DA signaling. We conclude that the nature of the diet (regular chow or HFHS) as well as the timing at which prebiotic supplementation is introduced (preventive or curative) greatly influence the efficacy of the gut-microbiota-brain axis. This crosstalk selectively alters the hedonic or motivational drive to eat and triggers molecular changes in neural substrates involved in the homeostatic and non-homeostatic control of body weight.

Keywords: dopaminergic system; food intake; hedonic and motivational component; prebiotic; reward.

Figure 1

(A). Experimental design of diet manipulation in which mice were fed, respectively, regular chow (Ctrl, black), high-fat high-sucrose diet (HFHS, red), or diet enriched in fructo-oligosaccharides (FOS) (Ctrl-FOS, gray and HFHS-FOS, orange) in a protective approach. Two additional groups were fed an HFHS and switched onto either regular chow diet (HFHS/Ctrl, blue) or regular chow enriched in FOS (HFHS/Ctrl-FOS, purple). (B–H) Body weight and body composition evolution during diet manipulation in the six different groups. (B,E) Body weight evolution, (C,D,F,G) body composition in (C,F) lean body mass (LBM) and (D,G) fat body mass in Ctrl (black), Ctrl-FOS (gray), HFHS (red), HFHS-FOS (orange), HFHS/Ctrl (blue), and HFHS/Ctrl-FOS (purple). (I,J) Targeted metagenomics analysis of cecum bacterial content in animal fed Ctrl (black), Ctrl-FOS (gray), HFHS (red), and HFHS-FOS (orange) and (J) after switch on Ctrl or Ctrl-FOS diet in HFHS/Ctrl (blue) and HFHS/Ctrl-FOS (purple). Data are expressed as mean ± SEM of 12 mice in each group. Significant differences from a one-way ANOVA (B–D), paired t-test (F) and a two-way ANOVA (I,J), Bonferroni Post hoc test are shown (*P < 0.005, **P < 0.001, ***P < 0.0005).

Figure 2

(A) Experimental design for food tropism analysis using short or overnight access to a two-food choice protocol using regular chow diet or palatable HFHS diet for six mice per group. Regular chow diet [CTRL (B,D,F,H)] or HFHS intake (C,D,G,H) during seven sessions consisting of a 2-h two-food choice access, (D,H) representative tropism for CTRL vs HFHS as average cumulated intake through all session or during the last session, (E,I) representative tropism for CTRL vs HFHS as average cumulated intake overnight in Ctrl (black), Ctrl-fructo-oligosaccharides (FOS) (gray), HFHS (red), HFHS-FOS (orange), HFHS/Ctrl (blue), and HFHS/Ctrl-FOS (purple). Data are expressed as mean ± SEM of six mice in each group. Significant differences from a two-way ANOVA, Bonferroni Post hoc test (*P < 0.005, **P < 0.001, ***P < 0.0005) (B–I).

Figure 3

(A) Experimental design for the operant responding performance assessment for six mice per group. (B,K) Reward number, (C,L) active lever press, (D,M) ratio between the active and inactive lever presses in (B–D) Ctrl (black), Ctrl-fructo-oligosaccharides (FOS) (gray), HFHS (red), (K–M) HFHS-FOS (orange), HFHS/Ctrl (blue), and HFHS/Ctrl-FOS (purple) during a 90% body weight reduction. (E,N) body weight change, reward number (F,G,O), active lever press (H,I,P) or active vs inactive lever press ratio (J,Q) in response to an overnight fast in Ctrl (black), Ctrl-FOS (gray), HFHS (red), HFHS-FOS (orange), HFHS/Ctrl (blue), and HFHS/Ctrl-FOS (purple). Data are expressed as mean ± SEM of six mice per group. Significant differences from a two-way ANOVA, Bonferroni Post hoc test are shown (*P < 0.005) (I).

Figure 4

Real-time PCR analysis of mRNA content (A) in the nucleus accumbens, for gene encoding for dopamine transporter (DAT), dopamine receptor 1 (DR1), dopamine receptor 2 (DR2), dopamine beta hydroxylase (DBH), and tyrosine hydroxylase (TH) and (B) in the hypothalamus for neuropeptide Y (NPY), Agouti-related protein (AgRP), Pro-opiomelanocortin (POMC), and cocaine and amphetamine-regulated transcript (CART) in Ctrl (black), Ctrl-fructo-oligosaccharides (FOS) (gray), HFHS (red), HFHS-FOS (orange), HFHS/Ctrl (blue), and HFHS/Ctrl-FOS (purple). Expression level corresponds to a ratio relative to housekeeping gene (HKG). Data are expressed as mean ± SEM of eight mice in each group. Significant differences from a two-way ANOVA, Bonferroni Post hoc test (*P < 0.005) (A,B).