Differential effects of two fermentable carbohydrates on central appetite regulation and body composition

Objective: To investigate if two different forms of fermentable carbohydrate (inulin and β-glucan) have the same effects on body composition and central appetite regulation in high fat fed mice. Methods: Thirty six C57BL/6 mice were randomized and maintained for 8 weeks on a high fat diet containing 10% (w/v) cellulose (control) or 10% (w/v) inulin or 10% (w/v) β-glucan. Measurements: Microbial changes were measured using fluorescent in situ hybridization, proton nuclear magnetic resonance (1H NMR) metabolic profiling were obtained from feces, colonic short chain fatty acids content was measured by gas chromatography, body composition and hypothalamic neuronal activation were measured using magnetic resonance imaging (MRI), and manganese enhanced MRI respectively, PYY concentration was determined by radioimmunoassay, adipocyte cell size and number were also measured. Results: Both the inulin and β-glucan groups showed significantly lower weight gain compared with controls. Energy intake was significantly greater in β-glucan than inulin fed mice, with the latter having the greatest effect on total adipose tissue content. Both groups also showed an increase in total bacteria and the numbers of Bifidobacterium and Lactobacillus-Enterococcus. Manganese enhanced MRI demonstrated a greater suppression of neuronal signal in the arcuate nucleus, ventromedial hypothalamus, paraventricular nucleus, periventricular nucleus and the nucleus of the tractus solitarius in the β-glucan supplemented group compared with the other two groups suggesting a reduction in neuronal activity. Conclusion: Although both fermentable carbohydrates are protective against increased body weight, the lower body fat content induced by inulin may be metabolically advantageous. β-glucan appears to suppress neuronal activity in hypothalamic appetite centers. Differential effects of fermentable carbohydrate open new possibilities for nutritionally targeting appetite regulation and body composition.