Dietary Effects on Metabolic Health in Mice

Eight-week-old C57Bl6/J male mice (n = 75; Janvier, France) were housed in pairs under specific conditions, i.e., specific and opportunistic pathogen-free conditions (SOPF) and in a controlled environment (12 h daylight cycle, temperature of 22 ± 2°C) with food and water ad libitum. After being acclimatized during one week with a control diet (CTRL) (D12450H, Research diet) and matched according to body weight and fat mass, mice were divided into 5 distinct dietary groups (n = 15/group): (1) control group of mice fed a control diet (D12450H, Research diets) containing 10% calories from fat (CTRL group); (2) mice fed a high-fat and high-sucrose diet (HFHS diet, D12451, Research diets) containing 45% calories from fat and 35% calories from carbohydrates (HFHS group); (3) mice fed a HFHS diet supplemented with rhubarb extract (0.3% w/w in the diet, Ortis, Belgium) (RHUB group), (4) mice fed a HFHS diet supplemented with inulin, a chicory root extract (20% food intake in water, Fibruline, Cosucra, Belgium) (ITF group); (5) mice fed a HFHS supplemented with rhubarb and inulin (0.3% rhubarb in the diet and 20% inulin in the drinking water) (RHUB+ITF group). Supplementation with either rhubarb, inulin or both started concomitantly with the introduction of HFHS diet. Water containing inulin was replaced every two days and the concentration of inulin was adapted depending on food intake for each cage. Body weight, food intake and water intake were recorded every week for the duration of the experiment (6 to 9 weeks). Body composition was assessed once a week by using 7,5-MHz time-domain nuclear magnetic resonance (LF50 minispec; Bruker; Rheinstetten, Germany). All mouse experiments were approved by and performed in accordance with the guideline of the local ethics committee (the ethics Committee of the Université catholique de Louvain for Animal Experiments specifically approved this study, agreement number 2017/UCL/MD/005).
At the end of the experiment and after 3 hours of fasting, all mice were anesthetized with isoflurane (Forene, Abbott, Queenborough, Ken, UK) and blood was sampled. After exsanguination, mice were euthanized by cervical dislocation. Organs and tissues were dissected, weighted, and directly immersed in liquid nitrogen before storage at −80°C for further analysis.