Low-molecular alginate improved diet-induced obesity and metabolic syndrome through modulating the gut microbiota in BALB/c mice

Alginate is the most abundant polysaccharide in brown seaweed, which is widely used as a food additive, but its high viscosity and gel property limit its applications in foods as a functional ingredient. In this study, low-molecular alginate from Laminaria japonica (L-LJA) was prepared, and its effect on obesity and metabolic syndrome was analyzed in high-fat diet (HFD)-fed mice. L-LJA reduced weight gain, fat accumulation in the liver and epididymal adipose tissue, lipid abnormality and inflammation in HFD-fed mice accompanied with the improvement of gut microbiota. L-LJA modulated the structure of gut microbiota, increased some Bacteroidales members, and reduced some Clostridiales members in mice, which were positively correlated with the improvement of physiological status. Fecal transplant from L-LJA-fed mice reduced fat accumulation in body tissues and lipid abnormality in the serum and liver and increased short chain fatty acids production in HFD-fed mice, confirming that L-LJA-induced gut microbiota alteration played an important role in its bioactivity. L-LJA has better solubility and can be utilized in food systems in high dose, implying that it can be developed as a prebiotic agent to increase both economic value and nutritive value of alginate.