Jose F. Garcia-Mazcorro, David A. Mills, Kevin Murphy, Giuliana Noratto

Barley is a low-glycemic index grain that can help diabetic and obese patients. The effect of barley intake depends on the host and the associated gut microbiota. This study investigated the effect of barley intake on the fecal microbiota, caecal biochemistry, and key biomarkers of obesity and inflammation. Obese db/db mice were fed diets with and without barley during 8 weeks; lean mice were used as lean controls. Fecal microbiota was evaluated using 16S marker gene sequencing in a MiSeq instrument; several markers of caecal biochemistry, obesity, and inflammation were also evaluated using standard techniques. Bacterial richness (i.e., Operational Taxonomic Units) and Shannon diversity indexes were similar in all obese mice (with and without barley) and higher compared to lean controls. Barley intake was associated with increased abundances of Prevotella, Lactobacillus, and the fiber-degraders S24-7 (Candidatus Homeothermaceae) compared to both lean and obese controls. The analysis of unweighted UniFrac distances showed a separate clustering of samples for each experimental group, suggesting that consumption of barley contributed to a phylogenetically unique microbiota distinct from both obese and lean controls. Caecal butyrate concentrations were similar in all obese mice, while succinic acid was lower in the barley group compared to obese controls. Barley intake was also associated with lower plasma insulin and resistin levels compared to obese controls. This study shows that barley intake is associated with a different fecal microbiota, caecal biochemistry, and obesity biomarkers in db/db mice that tend to be more similar to lean controls.