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-1β (IL-1β) 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).

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 and 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 and 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.

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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)-1β 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.

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.