The potential auxiliary effects of Sargassum fusiform polysaccharides on sitagliptin in the treatment of diabetes mellitus

This work aimed to evaluate the potential positive effects of Sargassum fusiform polysaccharides (SFP) as add-on adjuncts to sitagliptin (SIT) in treating diabetes in rats. The results showed that both SIT and SIT coadministrated with SFP (SIT+SFP) could improve hyperglycemia, glucose tolerance, insulin resistance and hyperlipidemia, and SIT+SFP exhibited better effects in alleviating the levels of blood glucose, glucose tolerance, insulin resistance index, cholesterol, and low-density lipoprotein cholesterol compared to SIT administration. Intestinal flora analysis showed that SIT+SFP treatment significantly restored the beneficial composition of gut flora as compared with SIT administration, such as the increase of Lactobacillus, Romboutsia, Blautia, Bifidobacterium, Bacteroides, Ruminococcaceae_UCG_014 and Ruminococcus_1, and the decrease of Helicobacter, Escherichia-Shigella and Pseudomonas. The fecal metabolite analysis demonstrated that the fecal bile acid and shortchain fatty acid levels in the SIT+SFP group significantly increased compared to SIT treatment. Additionally, mRNA expression results confirmed that the hypoglycemic effects of SIT+SFP were better than those of SIT, which might be attributed to the regulation of blood glucose absorption, inhibition of gluconeogenesis and regulation of cholesterol metabolism. These results suggested that SFP could be used as an auxiliary substance for SIT in treating diabetes mellitus.