Whole grain component: An innovative whole grain model ingredient to glycemic control in diabetic mice via the function of GLP-1

Whole grain food is a type of healthy food with many beneficial effects, but the fundamental mechanism is still illusive. In the current study, a whole grain component (WGC), as a whole grain model, was prepared by mimicking the endosperm cellular structure through encapsulating glucomannan (dietary fiber) and starch in a matrix formed by polysaccharide gelation. A high level of slowly digestible starch (SDS) (>50 %) in WGC was observed from an in vitro digestion experiment. When the in vivo test of WGC was conducted, a reduced postprandial glycemia and an increased GLP-1 response were observed, which confirmed the stimulation effect of WGC on the secretion GLP-1, an incretin hormone with numerous health benefits. Further study showed that the blood glucose level (from 29.2 to 9.5 mmol/L) and the biomarker HbA1c (from 10.5 to 6.4 %) in diabetic mice were significantly reduced under the condition of WGC-containing diet (WGC-diet). The β-cell function and insulin sensitivity were also significantly improved. Furthermore, the WGC-diet reversed the dysbiosis with increased production of healthy short-chain fatty acids, which are likely the basis to the secretion of GLP-1. Gene expression revealed that WGC-diet activated the GLP-1 signaling pathway, leading to an increased secretion of insulin and improved β-cell function, which all contribute to the glycemic control in diabetic mice. Thus, GLP-1, as pleotropic incretin hormone, could be an important mechanism to the various health benefits of whole grain foods.