Effects of Laminarin on Gut Microbiota of High Fat Diet-induced Obese Mice

Abstract

Edible brown algae are one of the major food materials in Asian countries, especially in South Korea and Japan. In this study, the effects of laminarin on weight gain, fecal short chain fatty acid (SCFA) and gut microbiota of high fat-fed mice were investigated. Mice were fed with 45% Kcal fat-diet (HF), 45% Kcal fat diet supplemented with 1% laminarin (HFL) and a normal diet (CTL) for four weeks. Additional two weeks of feeding trial without laminarin were allowed to investigate the post effects of laminarin. To indirectly measure prebiotics effects, concentrations of fecal SCFA were quantified using High-Performance Liquid Chromatography (HPLC). Fecal microbiota was also analyzed through sequencing V4 region of the 16S rRNA gene by Illumina's MiSeq. HFL showed no weight increase during the 4th week. Results from taxonomic composition comparison analysis showed that HFL had significantly higher abundance of the phylum Bacteroidetes (P<0.05) than those of HF but dramatically decreased after the termination of laminarin injection, suggesting that laminarin shifted gut microbiota to what is referred as a 'lean type of microbiota' and the effect did not last more than a week. In addition, HFD and HFL showed significantly lower concentrations of acetic, butyric, formic, lactic, propionic, and pyruvic acid (P<0.05) in feces, while isobutyric acid was not detected in any sample. As previously reported, HF and CTL displayed significantly different microbialcommunities in response to diet-induced obesity (P<0.05). Results from the NMDS analysis positioned HFL microbiota in between CTL and HF. Our results suggested that laminarin could shift gut microbiota toward 'lean type' but did not enhance SCFA production in gut. Further studies are required for investigation of prebiotics effects of laminarin.