by Tokyo Medical and Dental University
Several studies have shown that heart diseases and metabolic disorders, such as type 2 diabetes, are associated with the blood glucose levels after eating. However, certain foods, like the condiment vinegar, are reported to help decrease these levels if eaten with a meal. Another food product that produces a similar effect are dietary fibers. These fibers are also known to increase insulin response, improve fat metabolism, and have positive effects on the gut microbiome.
One such soluble fiber, xanthan gum, is used in a range of foods, including fluid thickeners, to prevent aspiration (choking) for patients who have difficulty swallowing. However, the biological effects of fluid thickener on postprandial blood glucose levels, gene expression in the gastrointestinal tract, and gut microbiome have not been fully clarified (Fig.1). The purpose of this study was to determine whether fluid thickeners have additional effects, particularly on postprandial blood glucose levels related to gene expression in the gastrointestinal tract and gut microbiome.
The rats were divided into two groups; those that were administered liquid thickened with a xanthan gum-based fluid thickener or saline for 5 weeks. Oral glucose tolerance test was performed 4 weeks after the beginning of the experiment. The blood glucose levels of rats were measured before glucose was given and at set intervals afterwards.
The RNA from different parts of the gastrointestinal system tissues were collected for qPCR method. Thereafter, the gene expression in the ileum and gut microbiome were comprehensively analyzed using a next-generation sequencer, which enables a comprehensive analysis of the amount of gene expression and DNA derived from microorganisms by decoding large quantities of DNA sequences at high speed.
Results showed that blood glucose levels at 60 and 90 minutes after being given glucose were significantly lower in rats given thickened liquid (Fig.2A). "The mechanism by which this happened is very interesting. Giving thickened liquid decreased blood glucose levels associated with Glp1 and Glp1r expression in the ileum (Fig.2B,C)," says senior author Haruka Tohara. Furthermore, comprehensive analysis revealed that cholesterol homeostasis, fatty acid metabolism, and glucose metabolism were enriched in the ileum.
Gut microbial composition was also altered after drinking the said thickened liquid. There was an increase in the numbers of two 'good' intestinal bacteria, Erysipelotrichales and Christensenellaceae, which is associated with Glp1 and Glp1r expression in the ileum (Fig.2D). These bacteria produce short-chain fatty acids that protect intestinal and pancreatic cells, which assist insulin secretion.
The findings are published in the Journal of Functional Foods.