Microbial Mechanistic Insight into the Role of Inulin in Improving Maternal Health in a Pregnant Sow Model

Abstract

General consumption of "western diet" characterized by high refined carbohydrates, fat and energy intake has resulted in a global obesity epidemics and related metabolic disturbance even for pregnant women. Pregnancy process is accompanied by substantial hormonal, metabolic and immunological changes during which gut microbiota is also remarkably remodeled. Dietary fiber has been demonstrated to have a striking role in shifting the microbial composition so as to improve host metabolism and health in non-pregnant individuals. The present study was conducted to investigate effects of adding a soluble dietary fiber inulin (0 or 1.5%) to low- or high- fat (0 or 5% fat addition) gestational diet on maternal and neonatal health and fecal microbial composition in a sow model. Results showed that inulin addition decreased the gestational body weight gain and fat accumulation induced by fat addition. Circulating concentrations of pro-inflammatory cytokine IL-6, adipokine leptin and chemerin were decreased by inulin supplementation. Inulin addition remarkably reduced the average BMI of newborn piglets and the within litter BMI distributions (%) ranging between 17 and 20 kg/m², and increased the BMI distribution ranging between 14 and 17 kg/m². 16S rRNA gene sequencing of the V3-V4 region showed that fecal microbial changes at different taxonomic levels triggered by inulin addition predisposed the pregnant sow to be thinner and lower inflammatory. Meanwhile, fecal microbial composition was also profoundly altered by gestation stage with distinct changes occurring at perinatal period. Most representative volatile fatty acid (VFA) producing-related genera changed dramatically when reaching the perinatal period and varied degrees of increases were detected with inulin addition. Fecal VFA concentrations failed to show any significant effect with dietary intervention, however, were markedly increased at perinatal period. Our findings indicate that positive microbial changes resulted by 1.5% soluble fiber inulin addition would possibly be the potential mechanisms under which maternal body weight, metabolic and inflammatory status and neonatal BMI were improved. Besides, distinct changes of microbial community at perinatal period indicated the mother sow is undergoing a catabolic state with increased energy loss and inflammation response at that period compared with other stages of gestation.

Keywords: dietary fiber; gestation; maternal health; microbial composition; neonatal body mass index.

Figure 1

(A,C) Body weight (BW) and (B,D) Backfat (BF) changes during gestation. Data were expressed as means ± SEM. Sows were regarded as the experimental units, n = 5 for each treatment. (B) BF thickness on G112: P = 0.05 for inulin effect. (C) Total BW gain: P < 0.01, = 0.08, and = 0.03 for fat, inulin and fat × inulin interaction effect, respectively; Maternal BW gain: P < 0.01, = 0.04, and = 0.02 for fat, inulin and fat × inulin interaction effect, respectively. (D) BF gain: P < 0.01 for fat, inulin, and fat × inulin interaction effect, respectively. When significant main effects or interative effects were observed, the means were compared using the least significant difference method with a P < 0.05 indicating significance. Therefore, mean values without a common letter are significantly different for each parameter in the figure (P < 0.05). LFD, low fat diet; LFD.Inu, low fat diet with inulin addition; HFD, high fat diet; HFD.Inu, high fat diet with inulin addition; maternal BW gain, net weight gain of sow itself. Only significant p-values were presented in the figure.

Figure 2

Maternal (A) serum inflammatory indices and (B–D) adipokines at perinatal period. Data were expressed as means ± SEM. Sows were regarded as the experimental units, n = 5 for each treatment. (A) IL-6: P = 0.04 for inulin effect; IL-10: P = 0.06 for inulin effect. (B) Serum leptin: P < 0.01 for fat and inulin effect and P = 0.01 for fat × inulin interaction effect; Backfat leptin: P = 0.06 for inulin effect. (C) Backfat adiponectin: P = 0.08 for inulin effect. (D) Serum chemerin: P < 0.01 for inulin effect; Backfat chemerin: P = 0.02 for inulin effect. When significant main effects or interative effects were observed, the means were compared using the least significant difference method with a P < 0.05 indicating significance. Therefore, mean values without a common letter are significantly different for each parameter in the figure (P < 0.05). LFD, low fat diet; LFD.Inu, low fat diet with inulin addition; HFD, high fat diet; HFD.Inu, high fat diet with inulin addition. Only significant p-values were presented in the figure.

Figure 3

Comparison of the OTUs among treatments at each gestation stage. The observed OTUs sharing ≥97% sequence similarity. (A–D) Venn diagrams were generated to describe the common and unique OTUs among treatments at d30, 60, 90, and 110 of gestation, respectively. (E) Observed species at different gestation stage. Sows were regarded as the experimental units, n = 5 for each treatment at each gestation stage except for LFD group on d90 and d110 with n = 4 due to an unexplained diarrhea on d88 of gestation which lasted for 2 days. LFD, low fat diet; LFD.Inu, low fat diet with inulin addition; HFD, high fat diet; HFD.Inu, high fat diet with inulin addition.

Figure 4

(A) Chao 1 and (B) Simpson index analyses over the course of gestation. Sows were regarded as the experimental units, n = 5 for each treatment at each gestation stage except for LFD group on d90 and d110 with n = 4 due to an unexplained diarrhea on d88 of gestation which lasted for 2 days. (A) Chao 1 index: P < 0.01 and P = 0.02 for gestation stage and fat × gestation stage interaction effect, respectively. (B) Simpson index: P = 0.02 and P = 0.01 for inulin and fat × inulin interaction effect, respectively. When significant main effects or interative effects were observed, the means were compared using the least significant difference method with a P < 0.05 indicating significance. Therefore, mean values without a common letter are significantly different for each parameter in the figure (P < 0.05). LFD, low fat diet; LFD.Inu, low fat diet with inulin addition; HFD, high fat diet; HFD.Inu, high fat diet with inulin addition. Only significant p values were presented in the figure.

Figure 5

The relative abundances of representative VFA-producing related genera (%) during gestation. (A) Eubacterium-hallii-group: P = 0.04 for inulin effect. (B) Enterococcus: P = 0.02 for gestation stage. (C) Anaerostipes: P < 0.01 for gestation stage. (D) Faecalibacterium: P < 0.01 for gestation stage. (E) Roseburia: P < 0.01 for gestation stage. (F) Akkermansia. (G) Veillonella. (H) Lactococcus: P = 0.02 for fat effect and P < 0.01 for gestation stage. Data were log-transformed following the addition of a small offset (0.00001) to counteract the presence of zero values before statistical analysis. Sows were regarded as the experimental units, n = 5 for each treatment at each gestation stage except for LFD group with n = 4 on d90 and d110 of gestation due to an unexplained diarrhea on d88 of gestation which lasted for 2 days. When significant main effects or interative effects were observed, the means were compared using the least significant difference method with a P < 0.05 indicating significance. LFD, low fat diet; LFD.Inu, low fat diet with inulin addition; HFD, high fat diet; HFD.Inu, high fat diet with inulin addition. Only significant p-values were presented in the figure.