Whole barley prevents obesity and dyslipidemia without the involvement of the gut microbiota in germ free C57BL/6J obese mice
Whole barley (WB) consumption is the subject of renewed interest because of its health benefits. However, there are still controversies regarding the mechanisms of the anti-obesity effects of WB. The gut microbiota has recently become a focus of research into obesity-related disorders. Therefore, the aim of this study was to investigate the contribution of the gut microbiota to the anti-obesity effects of WB. Germ-free (GF) C57BL/6J mice underwent gastric inoculation with human feces to obtain human flora-associated (HFA) mice, and then both the GF and HFA mice were fed a high fat diet (HFD) containing 46% WB or refined barley for 9 weeks. Features of obesity and dyslipidemia were compared between the GF and HFA mice and the cecal microbiota was analyzed using next-generation sequencing of microbial 16S rRNA. WB prevents obesity and hypercholesterolemia in the GF and HFA mice. The mechanism may include the inhibition of cholesterol synthesis, because sterol regulatory element-binding protein-1c (SREBP-1c) and 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG-CoA) expression was downregulated, and a reduction in cholesterol accumulation, because cholesterol 7α-hydroxylase (CYP7A1) expression was upregulated, independent of the gut microbiota. Furthermore, WB intake enriched a variety of bacterial genera that are negatively associated with obesity, including Bacteroides, Parabacteroides, and Clostridium cluster XIVa, suggesting that WB counteracted gut dysbiosis in obese mice. Thus, WB helps prevent obesity and dyslipidemia via both gut microbiota-dependent and independent mechanisms.