Hypocholesterolemic Effect of the Lignin-Rich Insoluble Residue of Brewer’s Spent Grain in Mice Fed a High-Fat Diet

Abstract

Insoluble residue (INS) is a lignin-rich fraction of brewer's spent grain (BSG) that also contains β-glucan and arabinoxylan, the major constituents of dietary fiber. We investigated the effects of INS in diet-induced obese mice in terms of lipid metabolism and metabolic diseases. Male mice (C57bl6) were fed a high-fat diet (HFD), a HFD + 20% INS, a HFD + 20% cellulose (CEL), a HFD with a combination of 20% INS−CEL (1:1), or a control diet for 14 weeks. Insulin and glucose tolerance tests were performed after 12 weeks. Fasting plasma lipids, bile acid, and fecal bile acid were measured after 14 weeks of feeding, and tissues were collected for gene expression analysis. Body weight gain was significantly reduced with all fibers, but only INS and INS−CEL decreased fasting plasma low-density lipoprotein cholesterol and total cholesterol compared to HFD. CEL and INS−CEL significantly improved insulin resistance. Fecal bile acids were significantly increased by all fibers, but there was no change in plasma bile acid. Clostridium leptum was increased with all fibers, but universal bacterial diversity was only with INS and INS−CEL. In addition, INS significantly increased the abundance of Bacteriodes, while CEL decreased Atopobium and Lactobacillus. INS feeding significantly upregulated various genes of cholesterol and bile acid metabolism, such as Srebp2, Hmgcr, Ldlr, Cyp7a1, Pparα, Fxr, and Pxr, in the liver. INS, INS−CEL, and CEL significantly attenuated liver steatosis. Our results suggest that INS from BSG induced beneficial systemic changes in mice via gut microbiota, bile acids, and gene expression in the liver.

Dietary Supplementation of Black Rice Anthocyanin Extract Regulates Cholesterol Metabolism and Improves Gut Microbiota Dysbiosis in C57BL/6J Mice Fed a High‐Fat and Cholesterol Diet

“…[ 25 ] Fecal neutral sterols mainly come from dietary cholesterol and its metabolism (i.e., coprostanol, coprostanone, and dihydrocholesterol converted by bacteria in large intestine). [ 28 ] As shown in Figure 2D and Table 4; Figure S2, Supporting Information, the BRAE supplement significantly increased the mRNA expression of LXRα, CYP7A1, while reduced the mRNA expression of the FXR and SHP, contributing to the excretion of fecal acidic sterols ( p < 0.05). In this study BRAE downregulated the intestine mRNA expression of NPC1L1, ACAT2, MTTP, upregulated ABCG5/8 expression in intestine ( p < 0.05), which means that fecal sterols absorption in intestinal epithelial cell were inhibited, while excretion was increased (Figure 2D).…”

“…Acidic sterols, also known as bile acids, are products of cholesterol bioconversion by CYP7A1, which then turned into secondary bile acids through series of fermentative reaction. [ 28 ]…”

Miscanthus Grass as a Nutritional Fiber Source for Monogastric Animals

“…One benefit that Miscanthus grass could have in human health is the control of cholesterol levels. Lignin was shown to have hypocholesterolemic effects in mice [85]. While Miscanthus grass still needs to be evaluated in humans, this could be another use of this fiber source.…”

Bioavailability Based on the Gut Microbiota: a New Perspective

“…Therefore, R. coptidis alkaloids and metformin can not only trigger an increase in the production of SCFAs by enriching a group of SCFA-producing gut bacteria but also reduce the absorption of harmful substances by the body via regulation of the gut microbiota. Furthermore, a lignin-rich fraction of brewer's spent grain (BSG), as a special dietary fiber containing ␤-glucan and arabinoxylan, could also promote the deconjugation of bile acids (132).…”