Sodium alginate and galactooligosaccharides ameliorate metabolic disorders and alter the composition of the gut microbiota in mice with high-fat diet-induced obesity.

We aimed to investigate the effects of sodium alginate (SA) and galactooligosaccharides (GOS) on the metabolism and gut microbiota of high-fat diet (HFD)-fed obese mice. GOS and SA delayed high-fat diet-induced obesity, reduced the epididymal fat and liver indices, and improved the circulating lipid profile. Low- and high-dose GOS reduced weight gain by 48.8 % and 35.3 %, and low- and high-dose SA reduced it by 37.7 % and 34.4 %, respectively. GOS and SA reduced blood glucose concentration, probably by increasing the expression of glucose transporter 4. GOS and SA increased the expression of tight junction proteins (ZO-1 and occludin), reduced the D-lactic acid (D-LA) and lipopolysaccharide concentrations, and reduced the expression of toll-like receptors, consistent with improved intestinal barrier function. GOS and SA also increased the abundance of Bacteroidota, Bifidobacterium, and Lactobacillus; and reduced that of Patescibacteria in the gut. The abundance of Parabacteroides positively correlated with the circulating low-density lipoprotein-cholesterol (LDL-C) concentration; that of Lactobacillus negatively correlated with LDL-C, D-LA, and tumor necrosis factor-α concentration; and that of Bifidobacterium positively correlated with high-density lipoprotein-cholesterol concentration, according to Spearman correlation analysis. In conclusion, SA and GOS ameliorate obesity and the associated metabolic disorders in mice, and also modulate their gut microbial composition.