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. 2017 Jul 21;7(1):6109.
doi: 10.1038/s41598-017-06447-x.

Short-chain Fatty Acids and Inulin, but Not Guar Gum, Prevent Diet-Induced Obesity and Insulin Resistance Through Differential Mechanisms in Mice

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Free PMC article

Short-chain Fatty Acids and Inulin, but Not Guar Gum, Prevent Diet-Induced Obesity and Insulin Resistance Through Differential Mechanisms in Mice

Karolin Weitkunat et al. Sci Rep. .
Free PMC article

Abstract

The role of dietary fibre and short-chain fatty acids (SCFA) in obesity development is controversially discussed. Here, we investigated how various types of dietary fibre and different SCFA ratios affect metabolic syndrome-related disorders. Male mice (B6) were fed high-fat diets supplemented with dietary fibres (either cellulose, inulin or guar gum) or different Ac:Pr ratios (high acetate (HAc) or propionate (HPr)) for 30 weeks. Body-fat gain and insulin resistance were greatly reduced by inulin, but not by guar gum, and completely prevented by SCFA supplementation. Only inulin and HAc increased body temperature, possibly by the induction of beige/browning markers in WAT. In addition, inulin and SCFA lowered hepatic triglycerides and improved insulin sensitivity. Both, inulin and HAc reduced hepatic fatty acid uptake, while only inulin enhanced mitochondrial capacity and only HAc suppressed lipogenesis in liver. Interestingly, HPr was accompanied by the induction of Nrg4 in BAT. Fermentable fibre supplementation increased the abundance of bifidobacteria; B. animalis was particularly stimulated by inulin and B. pseudolongum by guar gum. We conclude that in contrast to guar gum, inulin and SCFA prevent the onset of diet-induced weight gain and hepatic steatosis by different mechanisms on liver and adipose tissue metabolism.

Conflict of interest statement

The authors declare that they have no competing interests.

Figures

Figure 1
Figure 1
Inulin and SCFA prevent diet-induced body weight/fat gain and insulin resistance. Male C57BL/6JRj mice were fed a semi-synthetic low-fat diet (LF) or high-fat diets (HF) supplemented with either 10% dietary fibre (HFC: 10% cellulose; HFI: 3% cellulose + 7% inulin; HFG: 3% cellulose + 7% guar gum; depicted in green hues) or 5% SCFA (depicted in red hues) with different Ac:Pr ratios, a high acetate (HAc; 10:1 Ac:Pr) or high propionate diet (HPr; 1:2.5 Ac:Pr). Body weight development during (A) dietary fibre, (B) SCFA intervention or (C) final body weight (BW) after 30 weeks, n = 20–22. (DF) Time-dependent blood glucose levels and (G, H) insulin concentrations after oral glucose load (2 g/kg body weight) and the corresponding incremental area under the curves (iAUC), n = 10–11. (I) Rectal body temperature was measured in week 29 of intervention, n = 19–21. Tissue weights of (J) subcutaneous white adipose tissue (sWAT) and (K) epididymal WAT (eWAT) adipose tissue (BAT) after 30 weeks, n = 19–21. Data are mean +/− SEM, */#P < 0.05; **/##P < 0.01, ***/###P < 0.001. *Significant differences HFC vs. HFI or HF vs. HAc, #significant differences HFI vs. HFG or HF vs. HPr.
Figure 2
Figure 2
Inulin and SCFA reduce adipocyte size and affect adipose tissues metabolism by distinct mechanisms. Characterization of (AD) subcutaneous white adipose tissue (sWAT) and (E,F) brown adipose tissue (BAT) of male C57BL/6JRj mice that were fed a semi-synthetic low-fat diet (LF) or high-fat diets (HF) supplemented with either 10% dietary fibre (HFC: 10% cellulose; HFI: 3% cellulose + 7% inulin; HFG: 3% cellulose + 7% guar gum; depicted in green hues) or 5% SCFA (depicted in red hues) with different Ac:Pr ratios, a high acetate (HAc; 10:1 Ac:Pr) or high propionate diet (HPr; 1:2.5 Ac:Pr) for 30 weeks. (A) Representative histological images of sWAT. (B) Adipocyte size distribution and corresponding quantification of cell size, n = 5. Measurement of cytochrome c oxidase (COX) activity in (C) sWAT and (E) BAT, n = 5. Analysis of mRNA expression in (D) sWAT or (F) BAT, normalized to LF-diet (set as 1), n = 8–9. (G) Relative Nrg4 secretion of primary brown adipocytes after 4 h of treatment with propionate (Pr) or without treatment (M, Media), n = 5. Data are mean + SEM, *P < 0.05; **P < 0.01; ***P < 0.001.
Figure 3
Figure 3
Inulin and SCFA prevent the onset of diet-induced hepatic steatosis by affecting lipid metabolism in different ways. Characterization of liver tissue in male C57BL/6JRj mice that were fed a semi-synthetic low-fat diet (LF) or high-fat diets (HF) supplemented with either 10% dietary fibre (HFC: 10% cellulose; HFI: 3% cellulose + 7% inulin; HFG: 3% cellulose + 7% guar gum; depicted in green hues) or 5% SCFA (depicted in red hues) with different Ac:Pr ratios, a high acetate (HAc; 10:1 Ac:Pr) or high propionate diet (HPr; 1:2.5 Ac:Pr) for 30 weeks. (A) Representative H&E staining of hepatocytes after intervention. (B) Liver tissue weight (n = 19–21) and corresponding (C) hepatic triglyceride (TG) concentration, n = 9–11. (D) Formation of odd-chain fatty acids (OCFA) in liver phospholipid fraction, n = 8. (E) Hepatic gene expression, (F) respective western blots with corresponding load control (GAPDH) and (G) analysis of protein expression (normalized to LF-diet as set to a value of 1), n = 4–8. Analysis of (H) citrate synthase (CS) and (I) cytochrome c oxidase (COX) activity in liver, n = 5–8. (J) Hepatic fatty acid synthase (FASN) activity and (K) calculated de novo lipogenesis (DNL)-Index by measurement of long-chain fatty acid amount in liver phospholipids, n = 8. Data are mean + SEM. *P < 0.05; **P < 0.01; ***P < 0.001.
Figure 4
Figure 4
Dietary fibre supplementation modulates the faecal microbiota composition after 30 weeks. Faecal microbiota composition of male C57BL/6JRj mice that were fed a semi-synthetic low-fat diet (LF) or high-fat diets (HF) supplemented with 10% dietary fibre (HFC: 10% cellulose; HFI: 3% cellulose + 7% inulin; HFG: 3% cellulose + 7% guar gum) for 30 weeks. (A) Microbial diversity at phylum-level, (B) Actinobacteria (phylum), (C) Bifidobacterium (genus), (D) Bifidobacterium animalis, (E) Bifidobacterium pseudolongum. Data are shown for individual animals (numbered 1–22) and as group mean + SEM (n = 4–7), *p < 0.05, **p < 0.01, ***p < 0.001.
Figure 5
Figure 5
Overview of dietary fibre- and SCFA-mediated metabolic effects to accomplish the prevention of diet-induced metabolic disorders. WAT: White adipose tissue; FA: Fatty acid; Nrg4: Neuregulin 4; BAT: Brown adipose tissue.

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