Dietary intake of barley β-
glucan (BG) is known to affect energy metabolism. However, its underlying mechanism remains poorly understood because studies have presented inconsistent results, with both positive and negative effects reported in terms of satiety, energy intake,
weight loss, and
glycemic control. The objective of this study was to clarify the physiological role underlying the metabolic benefits of barley BG using a mouse model of high fat diet (HFD)-induced
obesity. Male 4-wk-old C57BL/6J mice were fed an HFD with 20% barley flour containing either high BG (HBG; 2% BG) or low BG (LBG; 0.6% BG) levels under conventional and germ-free (GF) conditions for 12 wks. In addition, mice were fed either an HFD with 5%
cellulose (HFC; high fiber
cellulose) or 5% barley BG (HFB; high fiber β-
glucan) for 12 wks. Then, metabolic parameters, gut microbial compositions, and the production of fecal
short-chain fatty acids (SCFAs) were analyzed. The
weight gain and fat mass of HBG-fed mice were lower than those of control mice at 16-wk-old. Moreover, the secretion of the gut
hormones PYY and
GLP-1 increased in HBG-fed mice, thereby reducing food intake and improving
insulin sensitivity by changing the gut microbiota and increasing SCFAs (especially,
butyrate) under conventional condition. These effects in HBG-fed mice were abolished under GF conditions. Moreover, the HFB diets also increased PYY and
GLP-1 secretion, and decreased food intake compared with that in HFC-fed mice. These results suggest that the beneficial metabolic effects of barley BG are primary due to the suppression of appetite and improvement of
insulin sensitivity, which are induced by gut
hormone secretion promoted via gut microbiota-produced SCFAs.