Cardioprotection of stevioside on stunned rat hearts: A mechano-energetical study

Stevioside Improves Antioxidant Capacity and Intestinal Barrier Function while Attenuating Inflammation and Apoptosis by Regulating the NF-κB/MAPK Pathways in Diquat-Induced Oxidative Stress of IPEC-J2 Cells

As a natural sweetener, stevioside is extracted from Stevia rebaudiana Bertoni and possesses potent antioxidant activity. However, little information is known about its protective role in maintaining the intestinal epithelial cells health under oxidative stress. The aim of this study was to investigate the protective effects and underlying mechanisms of stevioside on alleviating inflammation, apoptosis, and improving antioxidant capacity in intestinal porcine epithelial cells (IPEC-J2) under oxidative stress by diquat. The results demonstrated that the pretreatment with stevioside (250 μM) for 6 h increased cell viability and proliferation and prevented apoptosis induced by diquat at 1000 μM for 6 h in IPEC-J2 cells, compared with the diquat alone-treated cells. Importantly, stevioside pretreatment significantly reduced ROS and MDA production as well as upregulated T-SOD, CAT, and GSH-Px activity. Moreover, it also decreased cell permeability and improved intestinal barrier functions by significantly upregulating the tight junction protein abundances of claudin-1, occludin, and ZO-1. At the same time, stevioside significantly down-regulated the secretion and gene expression of IL-6, IL-8, and TNF-α and decreased the phosphorylation levels of NF-κB, IκB, and ERK1/2 compared with the diquat alone group. Taken together, this study demonstrated that stevioside alleviated diquat-stimulated cytotoxicity, inflammation, and apoptosis in IPEC-J2 cells, protecting cellular barrier integrity and mitigating oxidative stress by interfering with the NF-κB and MAPK signaling pathways.

Mechanism of neuroprotective effect of stevioside on cerebral ischemia-reperfusion injury via PPAR-γ activation

OBJECTIVE

The aim of this work was to explore the possible protective effects and its mechanism of stevioside on cerebral ischemia reperfusion (CIR) induced neuron damages.

METHODS

Middle cerebral artery occlusion/reperfusion (MCAO/R) rat models were constructed. The rats were treated with stevioside treatment, PPAR-γ antagonist GW9662, PPAR-γ activator pioglitazone or PI3K/AKT inhibitor LY294002 before neurological deficits were assessed using modified Neurological Severity Scale (mNSS) scores. The infarct size, brain injury, apoptotic cells, inflammatory cytokines in neurons extracted from MCAO/R rats were determined by TTC staining, H&E staining, TUNEL staining, qRT-PCR and Western blot, respectively.

RESULTS

Stevioside attenuates MCAO/R-induced neuronal apoptosis and inflammation by regulating PPAR-γ expression. Besides, PPAR-γ activates PI3K/AKT signaling pathway. Moreover, PPAR-γ antagonist GW9662 or PI3K/AKT inhibitor LY294002 abrogated the anti-apoptosis and anti-inflammatory effects of stevioside on MCAO/R rats.

CONCLUSION

Stevioside alleviates MCAO/R-induced neuronal apoptosis and inflammation by upregulating PPAR-γ to activate PI3K/AKT signaling pathway.

The role of metabolites of steviol glycosides and their glucosylated derivatives against diabetes-related metabolic disorders

Diabetes mellitus (DM), characterized by abnormal carbohydrate, lipid, and protein metabolism, is a metabolic disorder caused by a shortage of insulin secretion or decreased sensitivity of target cells to insulin. In addition to changes in lifestyle, a low-calorie diet is recommended to reduce the development of DM. Steviol glycosides (SGs), as natural sweeteners, have gained attention as sucrose alternatives because of their advantages of high sweetness and being low calorie. Most SGs with multiple bioactivities are beneficial to regulate physiological functions. Though SGs have been widely applied in food industry, there is little data on their glucosylated derivatives that are glucosylated steviol glycosides (GSGs). In this review, we have discussed the metabolic fate of GSGs in contrast to SGs, and the molecular mechanisms of glycoside metabolites against diabetes-related metabolic disorders are also summarized. SGs are generally extracted from the Stevia leaf, while GSGs are mainly manufactured using enzymes that transfer glucose units from a starch source to SGs. Results from this study suggest that SGs and GSGs share same bioactive metabolites, steviol and steviol glucuronide (SVG), which exhibit anti-hyperglycemic effects by activating glucose-induced insulin secretion to enhance pancreatic β-cell function. In addition, steviol and SVG have been found to ameliorate the inflammatory response, lipid imbalance, myocardial fibrosis and renal functions to modulate diabetes-related metabolic disorders. Therefore, both SGs and GSGs may be used as potential sucrose alternatives and/or pharmacological alternatives for preventing and treating metabolic disorders.

Stevioside inhibits unilateral ureteral obstruction-induced kidney fibrosis and upregulates renal PPARγ expression in mice

This study aimed to examine the inhibitory effect of stevioside on unilateral ureteral obstruction (UUO)-induced kidney fibrosis. The UUO mice were daily given 50-100 mg/kg stevioside by gavage for 14 days after the operation. The results showed that stevioside decreased the levels of blood urea nitrogen and renal hydroxyproline, severity of kidney fibrosis, and expressions of renal collagen I/III and α-smooth muscle actin proteins. Importantly, stevioside increased the expressions of renal peroxisome proliferator-activated receptor γ (PPARγ) and Smad7 proteins and level of renal glutathione peroxidase, decreased the expressions of renal nuclear factor kappa B (NF-κB), signal transducer and activator of transcription 3 (STAT3), p-STAT3, transforming growth factor-β1 (TGF-β1), Smad2/3, and p-Smad2/3 proteins, suggesting that the antifibrotic mechanisms are related to the activation of PPARγ and subsequent downregulations of NF-κB-mediated STAT3 and TGF-β1 expressions and inhibition of Smad-mediated signaling pathway. These findings provide an applied perspective of stevioside for kidney fibrosis. PRACTICAL APPLICATIONS: Stevioside is widely used in food products as a sweetener, and it has many beneficial biological effects, including antidiabetes, antihypertension, and renal protective action. Here, we provide a novel potential application of stevioside in the prevention and treatment of kidney fibrosis.

Antioxidant and immunomodulatory activity induced by stevioside in liver damage: In vivo, in vitro and in silico assays

AIMS

Stevioside is a diterpenoid obtained from the leaves of Stevia rebaudiana (Bertoni) that exhibits antioxidant, antifibrotic, antiglycemic and anticancer properties. Therefore, we aimed to study whether stevioside has beneficial effects in liver injury induced by long-term thioacetamide (TAA) administration and investigated the possible underlying molecular mechanism using in vivo, in vitro and in silico approaches.

MAIN METHODS

Liver injury was induced in male Wistar rats by TAA administration (200 mg/kg), intraperitoneally, three times per week. Rats received saline or stevioside (20 mg/kg) twice daily intraperitoneally. In addition, cocultures were incubated with either lipopolysaccharide or ethanol. Liver injury, antioxidant and immunological responses were evaluated.

KEY FINDINGS

Chronic TAA administration induced significant liver damage. In addition, TAA upregulated the protein expression of nuclear factor (NF)-κB, thus increasing the expression of proinflammatory cytokines and decreasing the antioxidant capacity of the liver through downregulation of nuclear erythroid factor 2 (Nrf2). Notably, stevioside administration prevented all of these changes. In vitro, stevioside prevented the upregulation of several genes implicated in liver inflammation when cocultured cells were incubated with lipopolysaccharide or ethanol. In silico assays using tumor necrosis factor receptor (TNFR)-1 and Toll-like receptor (TLR)-4-MD2 demonstrated that stevioside docks with TNFR1 and TLR4-MD2, thus promoting an antagonistic action against this proinflammatory mediator.

SIGNIFICANCE

Collectively, these data suggest that stevioside prevented liver damage through antioxidant activity by upregulating Nrf2 and immunomodulatory activity by blocking NF-κB signaling.

Stevioside inhibits experimental fibrosis by down-regulating profibrotic Smad pathways and blocking hepatic stellate cell activation

Liver cirrhosis is associated with increased morbidity and mortality with important health and social consequences; however, an effective treatment has not been found yet. Previous reports have shown some beneficial effects of stevioside (SVT) in different diseases, but the ability of SVT to inhibit liver cirrhosis has not been reported. Therefore, we studied the potential of this diterpenoid to inhibit liver cirrhosis induced by thioacetamide, a model that shares many similarities with the human disease, and investigated the possible underlying molecular mechanism using in vivo and in vitro approaches. Cirrhosis was induced in male Wistar rats by chronic thioacetamide administration (200 mg/kg) intraperitoneally three times per week. Rats received saline or SVT (20 mg/kg) two times daily intraperitoneally. In addition, co-cultures were incubated with either lipopolysaccharide or ethanol. Liver fibrosis, hepatic stellate cells activation, metalloproteinases activity, canonical and non-canonical Smads pathway and expression of several profibrogenic genes were evaluated. Thioacetamide activated hepatic stellate cells and distorted the liver parenchyma with the presence of abundant thick bands of collagen. In addition, thioacetamide up-regulated the protein expression of α-smooth muscle actin, transforming growth factor-β1, metalloproteinases-9,-2 and -13 and overstimulate the canonical and non-canonical Smad pathways. SVT administration inhibited all of these changes. In vitro, SVT inhibited the up-regulation of several genes implicated in cirrhosis when cells were exposed to lipopolysaccharides or ethanol. We conclude that SVT inhibited liver damage by blocking hepatic stellate cells activation, down-regulating canonical and non-canonical profibrotic Smad pathways.

Stevioside Prevents Wear Particle-Induced Osteolysis by Inhibiting Osteoclastogenesis and Inflammatory Response via the Suppression of TAK1 Activation

Aseptic loosening and periprosthetic osteolysis are the leading causes of total joint arthroplasty failure, which occurs as a result of chronic inflammatory response and enhanced osteoclast activity. Here we showed that stevioside, a natural compound isolated from Stevia rebaudiana, exhibited preventative effects on titanium particle-induced osteolysis in a mouse calvarial model. Further histological assessment and real-time PCR analysis indicated that stevioside prevented titanium particle-induced osteolysis by inhibiting osteoclast formation and inflammatory cytokine expression in vivo. In vitro, we found that stevioside could suppress RANKL-induced osteoclastogenesis and titanium particle-induced inflammatory response in a dose-dependent manner. Mechanistically, stevioside achieved these effects by disrupting the phosphorylation of TAK1 and subsequent activation of NF-κB/MAPKs signaling pathways. Collectively, our data suggest that stevioside effectively suppresses osteoclastogenesis and inflammatory response both in vitro and in vivo, and it might be a potential therapy for particle-induced osteolysis and other osteolytic diseases.

Stevia Nonsweetener Fraction Displays an Insulinotropic Effect Involving Neurotransmission in Pancreatic Islets

Stevia rebaudiana (Bert.) Bertoni besides being a source of noncaloric sweeteners is also an important source of bioactive molecules. Many plant extracts, mostly obtained with ethyl acetate solvent, are rich in polyphenol compounds that present insulinotropic effects. To investigate whether the nonsweetener fraction, which is rich in phenolic compounds isolated from Stevia rebaudiana with the solvent ethyl acetate (EAF), has an insulinotropic effect, including interference at the terminals of the autonomic nervous system of the pancreatic islets of rats. Pancreatic islets were isolated from Wistar rats and incubated with EAF and inhibitory or stimulatory substances of insulin secretion, including cholinergic and adrenergic agonists and antagonists. EAF potentiates glucose-stimulated insulin secretion (GSIS) only in the presence of high glucose and calcium-dependent concentrations. EAF increased muscarinic insulinotropic effects in pancreatic islets, interfering with the muscarinic receptor subfamily M3. Adrenergic inhibitory effects on GSIS were attenuated in the presence of EAF, which interfered with the adrenergic α2 receptor. Results suggest that EAF isolated from stevia leaves is a potential therapy for treating type 2 diabetes mellitus by stimulating insulin secretion only in high glucose concentrations, enhancing parasympathetic signal transduction and inhibiting sympathetic signal transduction in beta cells.