(-)-Epicatechin and β-glucan from highland barley grain modulated glucose metabolism and showed synergistic effect via Akt pathway

Epicatechin and β-glucan from whole highland barley grain ameliorates hyperlipidemia associated with attenuating intestinal barrier dysfunction and modulating gut microbiota in high-fat-diet-fed mice

Hyperlipidemia is associated with intestinal barrier dysfunction and gut microbiota dysbiosis. Here, we aimed at investigating whether epicatechin (EC) and β-glucan (BG) from whole highland barley grain alleviated hyperlipidemia associated with ameliorating intestinal barrier dysfunction and modulating gut microbiota dysbiosis in high-fat-diet-induced mice. It was observed that EC and BG significantly improved serum lipid disorders and up-regulated expression of PPARα protein and genes. Supplementation of EC and BG attenuated intestinal barrier dysfunction via promoting goblet cells proliferation and tight junctions. Supplementation of EC and BG prevented high fat diet-induced gut microbiota dysbiosis via modulating the relative abundance of Ruminococcaceae, Lactobacillus, Desulfovibrio, Lactococcus, Allobaculum and Akkermansia, and the improving of short chain fatty acid contents. Notably, combination of EC and BG showed synergistic effect on activating PPARα expression, improving colonic physical barrier dysfunction and the relative abundance of Lactobacillus and Desulfovibrio, which may help explain the effect of whole grain highland barley on alleviating hyperlipidemia.

Epicatechin and β-Glucan from Whole Highland Barley Grain Synergistic Benefit on Attenuating Hyperglycemia via Improving Hepatic Glucose Metabolism in Diabetic C57BL/6J Mice

Our previous study proved that epicatechin (EC) and β-glucan (BG) from whole-grain highland barley synergistically modulate glucose metabolism in insulin-resistant HepG2 cells. However, the main target and the mechanism underlying the modulation of glucose metabolism in vivo remain largely unknown. In this study, cell transfection assay and microscale thermophoresis analysis revealed that EC and BG could directly bind to the insulin receptor (IR) and mammalian receptor for rapamycin (mTOR), respectively. Molecular dynamic analysis indicated that the key amino acids of binding sites were Asp, Met, Val, Lys, Ser, and Tys. EC supplementation upregulated the IRS-1/PI3K/Akt pathway, while BG upregulated the mTOR/Akt pathway. Notably, supplementation with EC + BG significantly increased Akt and glucose transporter type 4 (GLUT4) protein expressions, while decreasing glycogen synthase kinase 3β (GSK-3β) expression in liver cells as compared to the individual effects of EC and BG, indicating their synergistic effect on improving hepatic glucose uptake and glycogen synthesis. Consistently, supplementation with EC + BG significantly decreased blood glucose levels and improved oral glucose tolerance compared to EC and BG. Therefore, combined supplementation with EC and BG may bind to corresponding receptors, targeting synergistic activation of Akt expression, leading to the improvement of hepatic glucose metabolism and thereby ameliorating hyperglycemia in vivo.

Procyanidin B1 and p-coumaric acid from whole highland barley ameliorated HFD-induced impaired glucose tolerance via small intestinal barrier and hepatic glucose metabolism

Highland barley is a natural source for the development of phenolic compounds that exhibit potential in preventing type 2 diabetes, which is important for the agricultural and industrial utilization of highland barley. However, very few studies have focused on their effect on small intestinal absorption and barrier dysfunction, as well as the direct target for the modulation of hepatic glucose metabolism. In this study, procyanidin B1 (PB) and p-coumaric acid (CA) isolated from highland barley supplementation in impaired glucose tolerance (IGT) mice significantly increased lactase-phlorizin hydrolase (LPH), sulfotransferase 1A1 (SULT1A1), UDP glucuronosyltransferase 1A (UGT1A) families and sodium-dependent glucose transporter 1 (SGLT1) expression in the small intestine of IGT mice, indicating beneficial effects on polyphenol deglycosylation and transportation. Supplementation with PB and CA also exhibited attenuation of small intestinal barrier dysfunction by improving the mucus layer and tight junctions, which was closely related to the transportation of phenolic compounds. In addition, PB and CA supplementation were explored directly to bind to the insulin receptor and activate the insulin receptor substrate-1 (IRS-1)/phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt) pathway, thereby modulating hepatic glucose metabolism and ameliorating hyperglycemic in IGT mice. These results offer crucial insights into the potential development of PB and CA as non-food nutraceuticals, as well as the extensive utilization of highland barley as an industrial crop.

Procyanidin B1 and Coumaric Acid from Highland Barley Alleviated High-Fat-Diet-Induced Hyperlipidemia by Regulating PPARα-Mediated Hepatic Lipid Metabolism and Gut Microbiota in Diabetic C57BL/6J Mice

A whole-grain highland barley (WHB) diet has been recognized to exhibit the potential for alleviating hyperlipidemia, which is mainly characterized by lipids accumulation in the serum and liver. Previously, procyanidin B1 (PB) and coumaric acid (CA) from WHB were found to alleviate serum lipid accumulation in impaired glucose tolerance mice, while the effect on modulating the hepatic lipid metabolism remains unknown. In this study, the results showed the supplementation of PB and CA activated the expression of peroxisome proliferator-activated receptor α (PPARα) and the target genes of cholesterol 7-α hydroxylase (CYP7A1) and carnitine palmitoyl transferase I (Cpt1) in the liver cells of high-fat-diet (HFD)-induced diabetic C57BL/6J mice, resulting in decreases in the serum total cholesterol (TC), triglyceride (TG), and low-density lipoprotein (LDL-C) contents, and an increase in the high-density lipoprotein (HDL-C) content. High-throughput sequencing of 16S rRNA indicated that supplementation with PB and CA ameliorated the gut microbiota dysbiosis, which was associated with a reduction in the relative abundance of Ruminococcaceae and an increase in the relative abundance of Lactobacillus, Desulfovibrio, and Akkermansia. Spearman's correlation analysis revealed that these genera were closely related to obesity-related indices. In summary, the activation of PPARα expression by PB and CA from WHB was important for the alleviation of hyperlipidemia and the structural adjustment of the gut microbiota.

Clinical applications and mechanism insights of natural flavonoids against type 2 diabetes mellitus

Diabetes is a complex disease that affects a large percentage of the world's population, and it is associated with several risk factors. Self-management poses a significant challenge, but natural sources have shown great potential in providing effective glucose reducing solutions. Flavonoids, a class of bioactive substances found in different natural sources including medicinal plants, have emerged as promising candidates in this regard. Indeed, several flavonoids, including apigenin, arbutin, catechins, and cyanidin, have demonstrated remarkable anti-diabetic properties. The clinical effectiveness of these flavonoids is linked to their potential to decrease blood glucose concentration and increase insulin concentration. Thus, the regulation of certain metabolic pathways such as glycolysis and neoglycogenesis has also been demonstrated. In vitro and in vivo investigations revealed different mechanisms of action related to flavonoid compounds at subcellular, cellular, and molecular levels. The main actions reside in the activation of glycolytic signaling pathways and the inhibition of signaling that promotes glucose synthesis and storage. In this review, we highlight the clinical efficiency of natural flavonoids as well as the molecular mechanisms underlying this effectiveness.

Catechins and Proanthocyanidins Involvement in Metabolic Syndrome

Recent studies on natural antioxidant compounds have highlighted their potentiality against various pathological conditions. The present review aims to selectively evaluate the benefits of catechins and their polymeric structure on metabolic syndrome, a common disorder characterized by a cluster of three main risk factors: obesity, hypertension, and hyperglycemia. Patients with metabolic syndrome suffer chronic low inflammation state and oxidative stress both conditions effectively countered by flavanols and their polymers. The mechanism behind the activity of these molecules has been highlighted and correlated with the characteristic features present on their basic flavonoidic skelethon, as well as the efficient doses needed to perform their activity in both in vitro and in vivo studies. The amount of evidence provided in this review offers a starting point for flavanol dietary supplementation as a potential strategy to counteract several metabolic targets associated with metabolic syndrome and suggests a key role of albumin as flavanol-delivery system to the different target of action inside the organism.

Barley β-glucan inhibits digestion of soybean oil in vitro and lipid-lowering effects of digested products in cell co-culture model

The effect of barley β-glucan on soybean oil digestion characteristics before and after fermentation was studied in an in vitro-simulated gastrointestinal digestion model. The addition of barley β-glucan made the system more unstable, the particle size increased significantly, and confocal laser imaging showed that it was easier to form agglomerates. The addition of barley β-glucan increased the proportion of unsaturated fatty acids in digestion products, and reduced digestibility of soybean oil. In a co-culture model of Caco-2/HT29 and HepG2 cells, the effects of digestive products of soybean oil and barley β-glucan before and after fermentation on lipid metabolism in HepG2 cells were investigated. The results showed that adding only soybean oil digestion products significantly increased triglycerides (TG) content and lipid accumulation in basolateral HepG2 cells. When fermented barley β-glucan was added, lipid deposition was significantly decreased, and the lipid-lowering activity was better than that of unfermented barley β-glucan.

Beneficial Effects of Partly Milled Highland Barley on the Prevention of High-Fat Diet-Induced Glycometabolic Disorder and the Modulation of Gut Microbiota in Mice

The nutritional functions of highland barley (HB) are superior to those of regular cereals and have attracted increasing attention in recent years. The objective of this study was to investigate whether partly milled highland barley (PHB) can regulate the serum glucose and lipid disorders of mice fed a high-fat diet (HFD) and to further explore their potential gut microbiota modulatory effect. Our results showed that PHB supplementation significantly reduced fasting blood glucose (FBG) and improved oral glucose tolerance. Histological observations confirmed the ability of PHB to alleviate liver and intestine damage. Furthermore, the results of 16S amplicon sequencing revealed that PHB prevented a HFD-induced gut microbiota dysbiosis, enriching some beneficial bacteria, such as Lactobacillus, Bifidobacterium, and Ileibacterium, and reducing several HFD-dependent taxa (norank_f_Desulfovibrionaceae, Blautia, norank_f_Lachnospiraceae, unclassified_f_Lachnospiraceae, and Colidextribacter). In addition, the increase of Lactobacillus and Bifidobacterium presence has a slightly dose-dependent relationship with the amount of the added PHB. Spearman correlation analysis revealed that Lactobacillus and Bifidobacterium were negatively correlated with the blood glucose level of the oral glucose tolerance test. Overall, our results provide important information about the processing of highland barley to retain its hypoglycemic effect and improve its acceptability and biosafety.