Amelioration of Obesity in Mice Fed a High-Fat Diet with Uronic Acid-Rich Polysaccharides Derived from Tremella fuciformis

Abstract

Obesity is rapidly becoming an emerging disease in developing countries due to the Westernization of societies and lifestyle changes. This study evaluated the ameliorative effect of acidic heteropolysaccharides derived from Tremella fuciformis (TFPS) on high-fat diet (HFD; 34.9% fat)-induced obesity in mice. The TFPS exhibited high uronic acid content and high viscosity in water. The structural characteristics of TFPS showed that average molecular weight was 679 kDa, and the monosaccharide composition was galactose, glucose, fructose, xylose, fucose, and mannose at a ratio of 1.0:6.5:10.0:18.5:30.5:67.5. In an in vivo study, HFD-induced obese C57BL/6 mice were orally given a TFPS treatment at 1 and 2 g/kg of body weight for 8 weeks. The TFPS treatment significantly reduced features of obesity in the mice, namely weight gain, feed efficiency, body fat percentage, and serum cholesterol level and increased fecal lipid content, compared with mice fed an HFD with water. In addition, TFPS exhibited the inhibition of cholesterol micelles in vitro in a concentration-dependent manner. In conclusion, the TFPS treatment ameliorated the diet-induced obesity in the mice, presumably reducing fat absorption in the intestine by interfering with viscous TFPS.

Keywords: Tremella fuciformis; high-fat diet; obesity; polysaccharide; uronic acid; viscosity.

Figure 1

Anion-exchange chromatogram of water-soluble polysaccharides from Tremella fuciformis (TFPS) on a DEAE-650M column and eluted with 20 mM tris buffer (pH 7.8), followed by a sodium chloride gradient (0–0.32 M); the carbohydrate, uronic acid and protein contents were determined through a phenol–sulfuric acid method, m-hydroxydiphenyl method and Bradford method, respectively.

Figure 2

¹H NMR spectra of polysaccharides from Tremella fuciformis (TFPS).

Figure 3

(A) Viscosity of aqueous solutions of polysaccharides from Tremella fuciformis (TFPS) in water at 25 °C, 37 °C, 50 °C, and 75 °C. (B) Effect of TFPS on the solubility of cholesterol micellar in vitro (n = 3).

Figure 4

Body weight of mice in different groups. ^# p < 0.05, ^## p < 0.01, and ^### p < 0.001 while high-fat diet (HFD)-H₂O group compared with the normal diet-H₂O group. ** p < 0.01 and *** p < 0.001, while HFD-TFPS group compared with the HFD-H₂O group. HFD-TL and HFD-TH groups received oral administration of 1 and 2 g/kg TFPS, respectively.

Figure 5

Effects of the TFPS treatment on the weights of the (A) gonadal adipose tissue, (B) perirenal adipose tissue, and (C) mesenteric adipose tissue as well as (D) body fat percentage. Mice were fed an HFD or ND, and the HFD mice were treated with water (p.o.) or TFPS (p.o.) for 8 weeks. All values are means ± standard error (n = 12). ^### p < 0.001 while HFD-H₂O group compared with the ND-H₂O group; ** p < 0.01 and *** p < 0.001 while HFD-TFPS groups compared with the HFD-H₂O group.

Figure 6

Histology of the gonadal adipose tissue of mice in the (a) ND-H2O, (b) HFD- H2O, (c) HFD-TL (TFPS 1 g/kg), and (d) HFD-TH (TFPS 2 g/kg) groups. Each image is representative of the nine mice (10 × 40).