The Impact of Dietary Fiber as a Prebiotic on Inflammation in Children with Obesity

Abstract

Background: Obesity is associated with dysbiosis, contributing to inflammation and insulin resistance. Inulin might reduce inflammation by manipulating intestinal microbiota. Objective: We aimed to determine the effects of inulin supplementation on inflammation and assess the relationships of inflammatory cytokines with adiposity and insulin resistance in obese Thai children. Design: Obese Thai children ages 7−15 years were randomly assigned to inulin (intervention), maltodextrin (placebo), and dietary fiber advice groups. All participants received monthly follow-up and identical advice on lifestyle modification for six visits. Body composition was evaluated using bioelectrical impedance analysis. IL-1β, IL-6, TNF-α, and fecal calprotectin were analyzed by ELISA technique at baseline and the final visit. Spearman correlation was used to assess the associations between inflammation and other clinical outcome variables. Results: A total of 155 obese children completed the study (mean age: 10.4 ± 2.2 years, 59% male). All groups showed a significant decrease in BMI z-score, fat mass index (FMI), percent body fat, and trunk FMI. A generalized estimating equation (GEE) model showed significantly decreased IL-1β and TNF-α of 34.8% and 25.8%, (p < 0.0001) but increased IL-6 (21.5%, p = 0.006) in all groups. There were no significant differences in inflammatory cytokines and fecal calprotectin between groups. Mean IL-6 was higher in obese children with acanthosis nigricans (p = 0.048). Only IL-6 was positively correlated with body fat percentage and FMI (r = 0.29, p = 0.008 and r = 0.25, p = 0.049, respectively). Conclusions: Intensive behavioral modification and frequent follow-up visits were effective methods to reduce BMI and adiposity leading to decreased inflammatory cytokines. The additional benefits of inulin on inflammation could not be demonstrated due to the Hawthorne effect. Among the three cytokines, IL-6 was the most likely mediator relating FM and insulin resistance at baseline; therefore, it could be used as a surrogate marker of inflammation in obese children who are at risk for insulin resistance and metabolic syndrome.

Keywords: fecal calprotectin; functional foods; inflammation; inflammatory cytokines; inulin; obesity; prebiotics.

Figure 1

Changes in inflammatory cytokines: (a) IL-1β, (b) IL-6, and (c) TNF-α over the 6-month intervention. IL-1β, IL-6, and TNF-α data were not normally distributed. The log transformation was used to make highly skewed distributions less skewed and then the comparison was made among geometric means (anti-log of the arithmetic mean of log-transformed value). Geometric mean for IL-1β and TNF-α decreased by 34.8% and 25.8%, respectively. Geometric mean for IL-6 increased by 21.5% in all groups. There was no difference between groups by GEE models. GEE, generalized estimating equation; IL, interleukin; TNF, tumor necrosis factor.

Figure 2

The relationship of IL-6 with body fat percentage (a), and FMI (b). IL-6 was positively correlated with body fat percentage and FMI (r = 0.29, p = 0.008 and r = 0.25, p = 0.049, respectively) by Spearman correlation coefficients. FMI, fat mass index; IL, interleukin.

Figure 2

The relationship of IL-6 with body fat percentage (a), and FMI (b). IL-6 was positively correlated with body fat percentage and FMI (r = 0.29, p = 0.008 and r = 0.25, p = 0.049, respectively) by Spearman correlation coefficients. FMI, fat mass index; IL, interleukin.