Mulberroside A from Cortex Mori Enhanced Gut Integrity in Diabetes.

BACKGROUND: Diabetic endotoxemia has been recognized as one of the hallmarks of type 2 diabetes mellitus (T2DM). Recent findings suggest that gut leak plays a pivotal role in diabetic endotoxemia. Cortex Mori (CM) has been widely applied in China to ameliorate development of T2DM, but its effect on endotoxemia is unknown. METHODS: The study was constructed with two parts: (1) in vivo study of CM on diabetic endotoxemia in db/db mice. Eight C57BL/6 mice were set as normal control; (2) in vitro study of mulberroside A (MBA) from CM on diabetic endotoxemia. Potential mechanism of MBA on ameliorating diabetic endotoxemia was also explored. RESULTS: The present study found that CM water extract decreased levels of blood glucose, ameliorated liver and renal damage in db/db mice, and ameliorated diabetic endotoxemia (p < 0.01). We also found that the water extract enhanced gut integrity and decreased gut inflammatory protein ICAM-1 expression in db/db mice as detected by H&E staining and immunohistochemistry methods. In the in vitro study, MBA decreased levels of MDA and ROS induced by LPS (p < 0.01) and enhanced the integrity of gut epithelial barrier (p < 0.01). CONCLUSIONS: We found that Cortex Mori and its active component mulberroside A could ameliorate diabetic endotoxemia by preserving gut integrity.

Kuwanon G protects HT22 cells from advanced glycation end product-induced damage.

The incidence of diabetic encephalopathy is increasing as the population ages. Evidence suggests that formation and accumulation of advanced glycation end products (AGEs) plays a pivotal role in disease progression, but limited research has been carried out in this area. A previous study demonstrated that Kuwanon G (KWG) had significant anti-oxidative stress and anti-inflammatory properties. As AGEs are oxidative products and inflammation is involved in their generation it is hypothesized that KWG may have effects against AGE-induced neuronal damage. In the present study, mouse hippocampal neuronal cell line HT22 was used. KWG was shown to significantly inhibit AGE-induced cell apoptosis in comparison with a control treatment, as determined by both MTT and flow cytometry. Compared with the AGEs group, expression of pro-apoptotic protein Bax was reduced and expression of anti-apoptotic protein Bcl-2 was increased in the AGEs + KWG group. Both intracellular and extracellular levels of acetylcholine and choline acetyltransferase were significantly elevated after KWG administration in comparison with controls whilethe level of acetylcholinesterase decreased. These changes in protein expression were accompanied by increased levels of superoxide dismutase and glutathione peroxidase synthesis and reduced production of malondialdehyde and reactive oxygen species. Intracellular signaling pathway protein levels were determined by western blot and immunocytochemistry. KWG administration was found to prevent AGE-induced changes to the phosphorylation levels of Akt, IκB-α, glycogen synthase kinase 3 (GSK3)-α and ß, p38 MAPK and NF-κB p65 suggesting a potential neuroprotective effect of KWG against AGE-induced damage was via the PI3K/Akt/GSK3αß signaling pathway. The findings of the present study suggest that KWG may be a potential treatment for diabetic encephalopathy.

Ginsenoside Rg1 attenuates high glucose-induced endothelial barrier dysfunction in human umbilical vein endothelial cells by protecting the endothelial glycocalyx.

Disruption of the endothelial barrier is essential for vascular complications associated with diabetes mellitus, and damage to the endothelial glycocalyx has been demonstrated to participate in this process. Ginsenoside Rg1 (Rg1), the major active component isolated from Panax notoginseng, is widely applied for the protection against vascular injury. The present study aimed to analyze the effect of high glucose on endothelial barrier function and its association with endothelial glycocalyx in human umbilical vein endothelial cells (HUVECs), and explore the potential benefits of Rg1 in protecting endothelial barrier function from high glucose-induced injury. The results indicated that high glucose induced a disorder of the endothelial glycocalyx and increased heparanase mRNA expression in HUVECs, which was reversed by Rg1 treatment. In addition, Rg1 treatment reduced transendothelial electrical resistance and transendothelial albumin passage after high-glucose stimulation. The present study suggested that high glucose caused a disruption in the endothelial glycocalyx and increased heparanase expression, which finally resulted in endothelial barrier dysfunction in HUVECs. Of note, Rg1 has a protective effect on high glucose-induced endothelial barrier dysfunction by attenuating the associated increase in heparanase expression.

Sodium butyrate supplementation ameliorates diabetic inflammation in db/db mice.

Endotoxemia has been recognized to be closely accompanied with type 2 diabetes mellitus (T2DM) and is responsible for many diabetic complications. Recent study suggests the potential role of butyrate, a short-chain fatty acid (SCFA) from microbiota metabolite, on T2DM. Gut-leak is a key event in diabetic-endotoxemia. To investigate if butyrate could ameliorate diabetic-endotoxemia, both in vivo and in vitro experiments were carried out in the present study. The effect of butyrate supplementation on blood HbA1c and inflammatory cytokines were determined in db/db mice; gut barrier integrity and expression of tight junction proteins were investigated both in vivo and in vitro Oral butyrate administration significantly decreased blood HbA1c, inflammatory cytokines and LPS in db/db mice; inflammatory cell infiltration was reduced, and gut integrity and intercellular adhesion molecules were increased as detected by HE staining, immunohistochemistry and Western blot. By gut microbiota assay, ratio of Firmicutes:Bacteroidetes for gut microbiota was reduced by butyrate. In Caco-2 cells, butyrate significantly promoted cell proliferation, decreased inflammatory cytokines' secretion, enhanced cell anti-oxidative stress ability and preserved the epithelial monocellular integrity, which was damaged by LPS. The present findings demonstrated that butyrate supplementation could ameliorate diabetic-endotoxemia in db/db mice via restoring composition of gut microbiota and preserving gut epithelial barrier integrity.

The role of short-chain fatty acids in kidney injury induced by gut-derived inflammatory response.

It has been found that several circulating metabolites derived from gut microbiota fermentation associate with a systemic immuno-inflammatory response and kidney injury, which has been coined the gut-kidney axis. Recent evidence has suggested that short-chain fatty acids (SCFAs), which are primarily originated from fermentation of dietary fiber in the gut, play an important role in regulation of immunity, blood pressure, glucose and lipid metabolism, and seem to be the link between microbiota and host homeostasis. In addition to their important role as fuel for colonic epithelial cells, SCFAs also modulate different cell signal transduction processes via G-protein coupled receptors, and act as epigenetic regulators by the inhibition of histone deacetylase and as potential mediators involved in the autophagy pathway. Though controversial, an intimate connection between SCFAs and kidney injury has been revealed, suggesting that SCFAs may act as new therapeutic targets of kidney injury. This review is intended to provide an overview of the impact of SCFAs and the potential link to kidney injury induced by gut-derived inflammatory response.

Short-Chain Fatty Acids Inhibit Oxidative Stress and Inflammation in Mesangial Cells Induced by High Glucose and Lipopolysaccharide.

Recently, an connection between Short-chain fatty acids (SCFAs) produced by intestinal microbiota and kidney has been revealed. The aim of this study was to explore whether SCFAs or their specific G protein-coupled receptors 43 (GPR43) agonist inhibit oxidative stress and inflammatory response in glomerular mesangial cells (GMCs) induced by high glucose and lipopolysaccharide (LPS). Our research showed that treatment with SCFAs, especially acetate and butyrate, or GPR43 agonist significantly inhibited GMCs proliferation induced by high glucose and LPS, and then reversed the production of reactive oxygen species (ROS) and malondialdehyde (MDA) but increased levels of antioxidant enzyme superoxide dismutase (SOD). Furthermore, SCFAs or GPR43 agonist obviously increased the protein expression of GPR43 induced by high glucose and LPS, but diminished the expression of adhesion molecule intercellular adhesion molecule-1 (ICAM-1), and then decreased the proinflammatory cytokine monocyte chemoattractant protein (MCP-1) and interleukin-1ß (IL-1ß) release from GMCs stimulated by the high glucose and LPS. These combined results support the hypothesis that SCFAs or GPR43 agonist can inhibit oxidative stress and inflammation of GMCs induced by high glucose and LPS, suggesting that SCFAs induced signaling pathway may act as new therapeutic targets of diabetic nephropathy (DN).

Kuwanon G Preserves LPS-Induced Disruption of Gut Epithelial Barrier In Vitro.

Defects in the gut epithelial barrier have now been recognized to be responsible for diabetic endotoxemia. In everyday life, Mulberry leaf tea is widely used in Asian nations due to its proposed benefits to health and control of diabetes. Evidence indicates the potential role of Kuwanon G (KWG), a component from Morus alba L., on blocking the gut epithelial barrier. In lipopolysaccharides (LPS)-damaged Caco-2 cells, it was found that KWG increased the viability of cells in a concentration-dependent manner. KWG administration significantly elevated the anti-oxidant abilities via increasing ratio of superoxidase dismutase (SOD)/malondialdehyde (MDA) and decreasing reactive oxygen species (ROS) within the cells. During KWG incubation, pro-inflammatory cytokines including interleukin (IL)-1ß and tumor necrosis factor (TNF)-α were significantly reduced, tight junction proteins including zonula occludens (ZO)-1, intercellular adhesion molecule (ICAM)-1 and Occludin were dramatically increased as detected by immunofluorescence assay, trans-epithelial electrical resistance was significantly increased and the transmission of albumin-fluorescein isothiocyanate (FITC) across the barrier was decreased. In conclusion, the present study demonstrated that KWG could ameliorate LPS-induced disruption of the gut epithelial barrier by increasing cell viability and tight junction between cells, and decreasing pro-inflammatory cytokines and oxidative damage.