Effects of dietary concentration of laminaran and depolymerised alginate on rat cecal microflora and plasma lipids

This study was carried out to survey the effects of laminalan and depolymerised sodium alginate (AG5), which are water soluble polysaccharides of brown algae and are not highly viscous, on the intestinal microflora and blood lipids in vitro and/or in vivo. Laminaran was fermented by human (two adults and an infant) fecal and rat cecal microflora in vitro. AG5 was fermented by these microflora besides infant fecal microflora. Laminaran was a more strongly fermented and supressed ammonia production than AG5. In vivo, the diets containing 0.4, 2 and 8% of laminaran or 0.4, 2 and 10% of AG5 were administered to male rats for one week. Eight and 10% of these polysaccharides lead to diarrhea and a decreased body weight gain. Cecal weights increased depending on the dose of the polysaccharides. Liver weights decreased depending on the dose of AG5. Cecal pH values were the lowest at 2% polysaccharides. Though 2% of laminaran increased cecal propionate and n-butyrate, 2% of AG5 decreased cecal short-chain fatty acids. AG5 decreased plasma triglycerides and cholesterol. High density lipoprotein cholesterol of plasma increased in the case of the diets containing 0.4% AGS. The ratio of cecal bifidobacteria to total bacteria was the highest, 0.4% at both polysaccharides. These results indicate that laminaran and AG5 have a profitable and different effect on intestinal microflora and levels of blood lipid depending on their concentrations.