Effects of the Brown Seaweed Laminaria japonica Supplementation on Serum Concentrations of IgG, Triglycerides, and Cholesterol, and Intestinal Microbiota Composition in Rats

Abstract

The intestinal microbial communities play critical roles in various aspects of body function of the host. Prebiotics, such as dietary fiber, can affect health of the host by altering the composition of intestinal microbiota. Although brown seaweed <i>Laminaria japonica</i> is rich in dietary fiber, studies on its prebiotic potential are quite rare. In this study, basal diet (control), basal diet supplemented with dried <i>L. japonica</i> (DLJ), heat-treated dried <i>L. japonica</i> (HLJ), or heated dried <i>L. japonica</i> with added fructooligosaccharide (FHLJ) was fed to rats for 16 weeks. Serum concentrations of IgG, triglyceride, and cholesterol were measured. In addition, the intestinal microbiota composition was analyzed by high-throughput sequencing of 16S rRNA gene. As compared to the control group, DLJ, HLJ, and FHLJ groups showed significantly higher serum IgG concentration, but had lower weight gain and serum triglyceride concentration. Moreover, DLJ, HLJ, and FHLJ groups showed lower <i>Fimicutes</i> to <i>Bacteroidetes</i> ratio when compared with the control group. As compared with the control group, obesity-associated bacterial genera (<i>Allobaculum, Turicibacter, Coprobacillus, Mollicute</i>, and <i>Oscilibacter</i>), and the genera with pathogenic potentials (<i>Mollicute, Bacteroides, Clostridium, Escherichia</i>, and <i>Prevotella</i>) decreased while leanness-associated genera (<i>Alistipes, Bacteroides</i>, and <i>Prevotella</i>), and lactic acid bacterial genera (<i>Subdoligranulum, Streptococcus, Lactobacillus, Enterococcus</i>, and <i>Bifidobacterium</i>) increased in all treatment groups. On the contrary, butyric acid producing genera including <i>Subdoligranulum, Roseburia, Eubacterium, Butyrivibrio</i>, and <i>Anaerotruncus</i> increased significantly only in FHLJ group. The overall results support multiple prebiotic effects of seaweed <i>L. japonica</i> on rats as determined by body weight reduction, enhanced immune response, and desirable changes in intestinal microbiota composition, suggesting the great potential of <i>L. japonica</i> as an effective prebiotic for promotion of host metabolism and reduction of obesity in humans.