Taurine ameliorates hyperglycemia and dyslipidemia by reducing insulin resistance and leptin level in Otsuka Long-Evans Tokushima fatty (OLETF) rats with long-term diabetes

This study aimed to determine whether taurine supplementation improves metabolic disturbances and diabetic complications in an animal model for type 2 diabetes. We investigated whether taurine has therapeutic effects on glucose metabolism, lipid metabolism, and diabetic complications in Otsuka Long-Evans Tokushima fatty (OLETF) rats with long-term duration of diabetes. Fourteen 50-week-old OLETF rats with chronic diabetes were fed a diet supplemented with taurine (2%) or a non-supplemented control diet for 12 weeks. Taurine reduced blood glucose levels over 12 weeks, and improved OGTT outcomes at 6 weeks after taurine supplementation, in OLETF rats. Taurine significantly reduced insulin resistance but did not improve β-cell function or islet mass. After 12 weeks, taurine significantly decreased serum levels of lipids such as triglyceride, cholesterol, high density lipoprotein cholesterol, and low density lipoprotein cholesterol. Taurine significantly reduced serum leptin, but not adiponectin levels. However, taurine had no therapeutic effect on damaged tissues. Taurine ameliorated hyperglycemia and dyslipidemia, at least in part, by improving insulin sensitivity and leptin modulation in OLETF rats with long-term diabetes. Additional study is needed to investigate whether taurine has the same beneficial effects in human diabetic patients.     

糖肾方对自发性Ⅱ型糖尿病鼠磷脂代谢的影响

利用正相液相色谱飞行时间质谱建立了大鼠血浆磷脂的轮廓谱。通过对磷脂轮廓谱的PLS-DA判别分析及14种化合物的定量,考察了中药糖肾方对自发性II型糖尿病鼠磷脂代谢的影响,并对比了糖肾方与西药蒙诺在糖尿病发展过程中的不同作用。结果表明：与正常对照组相比,糖尿病鼠的血浆磷脂代谢发生异常。糖肾方能够调节糖尿病鼠的磷脂代谢紊乱,蒙诺则加剧了病鼠的磷脂代谢异常。此外,8种磷脂化合物可能成为糖尿病发展过程中的潜在生物标志物。     

Ferulic Acid Stimulates Adipocyte-Specific Secretory Proteins to Regulate Adipose Homeostasis in 3T3-L1 Adipocytes

Obesity has recently emerged as a public health issue facing developing countries in the world. It is caused by the accumulation of fat in adipose, characterized by insulin resistance, excessive lipid accumulation, inflammation, and oxidative stress, leading to an increase in adipokine levels. Herein, we investigated the capacity of a bioactive polyphenolic compound (ferulic acid (FA)) to control adipocyte dysfunction in 3T3-L1 adipocytes (in vitro). Key adipocyte differentiation markers, glycerol content, lipolysis-associated mRNA, and proteins were measured in experimental adipocytes. FA-treated adipocytes exhibited downregulated key adipocyte differentiation factors peroxisome proliferator-activated receptor-γ (PPAR-γ), CCAT enhancer binding-proteins—α (C/EBP-α) and its downstream targets in a time-dependent manner. The FA-treated 3T3-L1 adipocytes showed an increased release of glycerol content compared with non-treated adipocytes. Also, FA treatment significantly up-regulated the lipolysis-related factors, including p-HSL, and p-perilipin, and down-regulated ApoD, Sema3C, Cxcl12, Sfrp2, p-stearoyl-CoA desaturase 1 (SCD1), adiponectin, and Grk5. Also, the FA treatment showed significantly down-regulated adipokines leptin, chemerin, and irisin than the non-treated cells. The present findings indicated that FA showed significant anti-adipogenic and lipogenic activities by regulating key adipocyte factors and enzyme, enhanced lipolysis by HSL/perilipin cascade. FA is considered a potent molecule to prevent obesity and its associated metabolic changes in the future.     

Myricitrin,a Glycosyloxyflavone in Myrica esculenta Bark Ameliorates Diabetic Nephropathy via Improving Glycemic Status,Reducing Oxidative Stress,and Suppressing Inflammation

The present study evaluated the therapeutic potential of myricitrin (Myr), a glycosyloxyflavone extracted from Myrica esculenta bark, against diabetic nephropathy. Myr exhibited a significant hypoglycemic effect in high fat-fed and a single low-dose streptozotocin-induced type 2 diabetic (T2D) rats. Myr was found to improve glucose uptake by the skeletal muscle via activating IRS-1/PI3K/Akt/GLUT4 signaling in vitro and in vivo. Myr significantly attenuated high glucose (HG)-induced toxicity in NRK cells and in the kidneys of T2D rats. In this study, hyperglycemia caused nephrotoxicity via endorsing oxidative stress and inflammation resulting in the induction of apoptosis, fibrosis, and inflammatory damages. Myr was found to attenuate oxidative stress via scavenging/neutralizing oxidative radicals and improving endogenous redox defense through Nrf-2 activation in both in vitro and in vivo systems. Myr was also found to attenuate diabetes-triggered renal inflammation via suppressing NF-κB activation. Myr inhibited hyperglycemia-induced apoptosis and fibrosis in renal cells evidenced by the changes in the expressions of the apoptotic and fibrotic factors. The molecular docking predicted the interactions between Myr and different signal proteins. An in silico absorption, distribution, metabolism, excretion, and toxicity (ADMET) study predicted the drug-likeness character of Myr. Results suggested the possibility of Myr to be a potential therapeutic agent for diabetic nephropathy in the future.     

Malaysian Propolis and Metformin Synergistically Mitigate Kidney Oxidative Stress and Inflammation in Streptozotocin-Induced Diabetic Rats

Diabetic nephropathy is reported to occur as a result of the interactions between several pathophysiological disturbances, as well as renal oxidative stress and inflammation. We examined the effect of Malaysian propolis (MP), which has anti-hyperglycemic, antioxidant and anti-inflammatory properties, on diabetes-induced nephropathy. Diabetic rats were either treated with distilled water (diabetic control (DC) group), MP (300 mg/kg b.w./day), metformin (300 mg/kg b.w./day) or MP + metformin for four weeks. We found significant increases in serum creatinine, urea and uric acid levels, decreases in serum sodium and chloride levels, and increase in kidney lactate dehydrogenase activity in DC group. Furthermore, malondialdehyde level increased significantly, while kidney antioxidant enzymes activities, glutathione level and total antioxidant capacity decreased significantly in DC group. Similarly, kidney immunoexpression of nuclear factor kappa B, tumor necrosis factor-α, interleukin (IL)-1β and caspase-3 increased significantly, while IL-10 immunoexpression decreased significantly in DC group relative to normal control group. Histopathological observations for DC group corroborated the biochemical data. Intervention with MP, metformin or both significantly mitigated these effects and improved renal function, with the best outcome following the combined therapy. MP attenuates diabetic nephropathy and exhibits combined beneficial effect with metformin.     

Thymoquinone Lowers Blood Glucose and Reduces Oxidative Stress in a Rat Model of Diabetes

The aim of the present study was to assess the short-term effects of Thymoquinone (TQ) on oxidative stress, glycaemic control, and renal functions in diabetic rats. DM was induced in groups II and III with a single dose of streptozotocin (STZ), while group I received no medication (control). The rats in groups I and II were then given distilled water, while the rats in group III were given TQ at a dose of 50 mg/kg body weight/day for 4 weeks. Lipid peroxidase, nitric oxide (NO), total antioxidant capacity (TAC), glycated haemoglobin (HbA1c), lipid profiles, and renal function were assessed. Moreover, the renal tissues were used for histopathological examination. STZ increased the levels of HbA1c, lipid peroxidase, NO, and creatinine in STZ-induced diabetic rats in comparison to control rats. TAC was lower in STZ-induced diabetic rats than in the control group. Furthermore, rats treated with TQ exhibited significantly lower levels of HbA1c, lipid peroxidase, and NO than did untreated diabetic rats. TAC was higher in diabetic rats treated with TQ than in untreated diabetic rats. The histopathological results showed that treatment with TQ greatly attenuated the effect of STZ-induced diabetic nephropathy. TQ effectively adjusts glycaemic control and reduces oxidative stress in STZ-induced diabetic rats without significant damaging effects on the renal function.     

The reno-protective effect of a phosphoinositide 3-kinase inhibitor wortmannin on streptozotocin-induced proteinuric renal disease rats

Diabetic nephropathy (DN) is a progressive kidney disease that is caused by injury to kidney glomeruli. Podocytes are glomerular epithelial cells and play critical roles in the glomerular filtration barrier. Recent studies have shown the importance of regulating the podocyte actin cytoskeleton in early DN. The phosphoinositide 3-kinase (PI3K) inhibitor, wortmannin, simultaneously regulates Rac1 and Cdc42, which destabilize the podocyte actin cytoskeleton during early DN. In this study, in order to evaluate the reno-protective effects of wortmannin in early DN by regulating Rac1 and Cdc42, streptozotocin (STZ)-induced proteinuric renal disease (SPRD) rats were treated with wortmannin. The albuminuria value of the SPRD group was 3.55 ± 0.56 mg/day, whereas wortmannin group was 1.77 ± 0.48 mg/day. Also, the albumin to creatinine ratio (ACR) value of the SPRD group was 53.08 ± 10.82 mg/g, whereas wortmannin group was 20.27 ± 6.41 mg/g. Changes in the expression level of nephrin, podocin and Rac1/Cdc42, which is related to actin cytoskeleton in podocytes, by wortmannin administration were confirmed by Western blotting. The expression levels of nephrin (79.66 ± 0.02), podocin (87.81 ± 0.03) and Rac1/Cdc42 (86.12 ± 0.02) in the wortmannin group were higher than the expression levels of nephrin (55.32 ± 0.03), podocin (53.40 ± 0.06) and Rac1/Cdc42 (54.05 ± 0.04) in the SPRD group. In addition, expression and localization of nephrin, podocin and desmin were confirmed by immunofluorescence. In summary, we found for the first time that wortmannin has a reno-protective effect on SPRD rats during the early DN. The beneficial effects of wortmannin in SPRD rats indicate that this compound could be used to delay the progression of the disease during the early DN stage.     

Excretion of formaldehyde, malondialdehyde, acetaldehyde and acetone in the urine of rats in response to 2,3,7,8-tetrachlorodibenzo-p-dioxin, paraquat, endrin and carbon tetrachloride.

Formaldehyde (FA), acetaldehyde (ACT), malondialdehyde (MDA) and acetone (ACON) were simultaneously identified in urine, and their excretion quantitated in response to chemically induced oxidative stress. Urine samples of female Sprague-Dawley rats were collected over dry ice and derivatized with 2,4-dinitrophenylhydrazine. The hydrazones of the four lipid metabolic products were quantitated by high-performance liquid chromatography on a Waters 10-microns mu-Bondapak C18 column. The identities of FA, ACT, MDA and ACON in urine were confirmed by gas chromatography-mass spectrometry. An oxidative stress was induced by orally administering 100 micrograms/kg 2,3,7,8-tetrachlorodibenzo-p-dioxin, 75 mg/kg paraquat, 6 mg/kg endrin or 2.5 ml/kg carbon tetrachloride to rats. Urinary excretion of FA, ACT, MDA and ACON increased relative to control animals 24 h after treatment with all xenobiotics. The system has wide-spread applicability to the investigation of altered lipid metabolism in disease states and exposure to environmental pollutants.     

Peroxisome proliferator-activated receptor �� agonist attenuates hepatic steatosis by anti-inflammatory mechanism

Although peroxisome proliferator receptor (PPAR)-α and PPAR-γ agonist have been developed as chemical tools to uncover biological roles for the PPARs such as lipid and carbohydrate metabolism, PPAR-δ has not been fully investigated. In this study, we examined the effects of the PPAR-δ agonist GW0742 on fatty liver changes and inflammatory markers. We investigated the effects of PPAR-δ agonist GW0742 on fatty liver changes in OLETF rats. Intrahepatic triglyceride contents and expression of inflammatory cytokines such as tumor necrosis factor-α (TNF-α) and monocyte chemo-attractant protein-1 (MCP-1) and also, PPAR-γ coactivator (PGC)-1α gene were evaluated in liver tissues of OLETF rats and HepG2 cells after GW0742 treatment. The level of TNF-α and MCP-1 was also examined in supernatant of Raw264. 7 cell culture. To address the effects of GW0742 on insulin signaling, we performed in vitro study with AML12 mouse hepatocytes. Rats treated with GW0742 (10 mg/kg/day) from 26 to 36 weeks showed improvement in fatty infiltration of the liver. In liver tissues, mRNA expressions of TNF-α, MCP-1, and PGC-1α were significantly decreased in diabetic rats treated with GW0742 compared to diabetic control rats. We also observed that GW0742 had inhibitory effects on palmitic acid-induced fatty accumulation and inflammatory markers in HepG2 and Raw264.7 cells. The expression level of Akt and IRS-1 was significantly increased by treatment with GW0742. The PPAR-δ agonist may attenuate hepatic fat accumulation through anti-inflammatory mechanism, reducing hepatic PGC-1α gene expression, and improvement of insulin signaling.     

Angiotensin II receptor blocker attenuates overexpression of vascular endothelial growth factor in diabetic podocytes

VEGF expressed in glomerular podocytes, is known to increase vascular permeability to macromolecules. Angiotensin II can stimulate the release of VEGF, and the protective effects of angiotensin II antagonist against diabetic glomerular injury suggest that the angiotensin II-induced VEGF is an important pathogenetic mechanism in the development of proteinuria during diabetic nephropathy although this mechanism is not fully understood. In this study, the changes of VEGF expression was examined in the experimental diabetic nephropathy to determine whether these changes were modified by renoprotective intervention by blockers of angiotensin II receptors. The streptozotocin- induced diabetic rats were treated with L-158,809, a blocker of angiotensin II receptors, for 12 weeks. Age-matched rats with L-158,809 served as controls. RT-PCR and immunohistochemistry were used to assess and quantify gene and protein expression of VEGF. A progressive increase in urinary protein excretion was observed in diabetic rats. Glomerular VEGF expression was significantly higher in diabetic rats than in the control groups, with a significant reduction in glomerular VEGF expression and proteinuria in L-158,809- treated diabetic rats. VEGF mRNA was also significantly higher in diabetic kidneys than in the control groups, with a significant reduction in VEGF mRNA in L-158,809-treated diabetic kidneys. These results demonstrates that VEGF expression is significantly increased in diabetic podocytes, and angiotensin II receptor antagonist attenuated these changes in VEGF expression and prevented the development of proteinuria in vivo. Attenuation of increased VEGF expression in podocytes could contribute to the renoprotective effects of angiotensin II receptor antagonists in diabetic nephropathy.     

Inhibitory effect of fumaric acid on 3'-methyl-4-(dimethylamino)azobenzene-induced hepatocarcinogenesis in rats

Fumaric acid (FA) suppressed the carcinogenesis in the liver of rats fed 3'-methyl-4-(dimethylamino)azobenzene (3'-Me-DAB), and a study was performed to examine the effect of FA on deoxyribonucleic acid (DNA) synthesis and subcellular structures of hepatocytes under the anticarcinogenic regimens. Male Donryu strain rats were given 3'-Me-DAB by being fed a diet containing 0.06% 3'-Me-DAB for 50 d. They were then given a diet containing 1% FA and drinking water containing 0.025% FA for 53 to 69 weeks. Hepatocytes were isolated from the liver by the collagenase perfusion method and placed in culture, and their activity for DNA synthesis was measured in terms of the incorporation of [3H]dThd into DNA. An enhanced DNA synthesis of hepatocytes was noted in the rats given FA, indicating that FA enhanced the proliferation of hepatocytes to counteract the carcinogenic effect of 3'-Me-DAB. An electron microscopic examination indicated that the distribution of subcellular organella was almost normal in the FA-treated hepatocytes.     

Inhibition on α-Glucosidase Activity and Non-Enzymatic Glycation by an Anti-Oxidative Proteoglycan from Ganoderma lucidum

The prevention of postprandial hyperglycemia and diabetic complications is crucial for diabetes management. Inhibition of α-glucosidase to slow carbohydrate metabolism is a strategy to alleviate postprandial hyperglycemia. In addition, suppression of non-enzymatic glycation can diminish the advanced glycation end products and reduce the oxidative stress and inflammation, thereby preventing the diabetic complications. In this study, an anti-oxidative proteoglycan (named FYGL) extracted from Ganoderma lucidum was investigated in vitro for its inhibitory effect on α-glucosidase and non-enzymatic glycation using molecular kinetics, intrinsic fluorescence assay, and bovine serum albumin glycation models. The molecular kinetics and fluorescence assay revealed that FYGL decreases α-glucosidase activity by forming a FYGL–α-glucosidase complex. To evaluate the anti-glycation effect, fructose-glycated and methylglyoxal-glycated BSA models were analyzed by spectroscopic and SDS-PAGE methods. Results showed that FYGL inhibited the glycation at every stage and suppressed glycoxidation, possibly due to its anti-oxidative capacity and FYGL–BSA complex formation. Furthermore, we demonstrated in vivo that FYGL could alleviate postprandial hyperglycemia in db/db mice as well as AGE accumulation and vascular injury in diabetic rats. Overall, FYGL possesses anti-postprandial hyperglycemia and anti-glycation functions and would be potentially used in clinic for diabetes and related complication management.     

Baicalein and Αlpha-Tocopherol Inhibit Toll-like Receptor Pathways in Cisplatin-Induced Nephrotoxicity

Cisplatin (CP) is a conventional chemotherapeutic agent with serious adverse effects. Its toxicity was linked to the stimulation of oxidative stress and inflammation. As a result, this study explored the protective effect of baicalein and alpha-tocopherol in nephrotoxicity induced by cisplatin. Until receiving an intraperitoneal injection of CP (3 mg/kg BW), rats were given baicalein orally 100 mg/kg for seven days or/and a single intraperitoneal injection of α-tocopherol 250 mg/kg. Renal function was tested to explore whether baicalein and α-tocopherol have any beneficial effects; blood urea nitrogen (BUN), serum creatinine, malondialdehyde (MDA) content, antioxidant activity biomarkers and histopathology of renal tissue, oxidative stress biomarkers, inflammatory response markers, and histopathological features of kidney architecture were measured. Cisplatin treatment resulted in extreme renal failure, as measured by high serum creatinine and BUN levels and severe renal changes. Cisplatin therapy resulted in increased lipid peroxidation and decreased glutathione and superoxide dismutase levels, reflecting oxidative stress. Upon treatment with α-tocopherol, baicalein, and combined therapy, there was augmentation in the antioxidant status as well as a reduction in IL-6, NF-κB, TNF, TLR2, and TLR4 and a significant increase in Keap-1 and NRF-2. The combined treatment was the most effective and the nearest to the normal status. These findings suggest that baicalein and α-tocopherol may be useful in preventing cisplatin-induced nephrotoxicity.     

Geraniin ameliorates streptozotocin-induced diabetic retinopathy in rats via modulating retinal inflammation and oxidative stress

BackgroundDiabetic retinopathy (DR) is the major complication of diabetes, which causes acquired vision loss in the working-age group population.ObjectiveHere, we planned to address the therapeutic roles of geraniin against the streptozotocin (STZ)-challenged DR in ratsMethodologyThe DR was induced in the animals by 60 mg/kg of STZ, and then treated with 25 mg/kg of geraniin for 60 days. Later, bodyweight, food consumption, and blood glucose levels were investigated. The levels of antioxidants, MMP-9, MCP-1, and VEGF, and inflammatory cytokine status were measured using marker-specific kits. The morphometric study was conducted to assess the retinal thickness. The pancreatic tissues were analyzed microscopically.ResultsGeraniin reduced the blood glucose (270.36 ± 81 mg/dL), hemoglobin, and enhanced bodyweight (261.93 ± 72 g)in the DR rats. The antioxidant levels in the STZ-challenged DR rats were substantially improved by geraniin. Geraniin also decreased inflammatory cytokines, MCP-I, MMP-9, and VEGF levels and enhanced the retinal thickness. A histological study demonstrated that geraniin reduced the pancreatic islet cell damage in STZ-induced DR rats.ConclusionOur outcomes witnessed that geraniin reduced retinal inflammation and oxidative stress in the STZ-induced DR rats.     

Regulation of oxidative stress inside living cells through polythiophene derivatives

Oxidative stress stimulated by angiotensin II(Ang II) plays an important role in the progression of inflammation and cardiovascular disease. In this work, polythiophene modified with dihydropyridine groups(PTDHP) realized the control of oxidative stress induced by Angiotensin II stimulation in living cells, by inhibiting the activity of NADPH oxidase via DHP groups. Upon light irradiation, the PTDHP could sensitize surrounding oxygen molecules to generate reactive oxygen species(ROS). The generated ROS oxidized the pendant DHP of polythiophene into pyridine group, which inactivated the control ability of DHP to oxidative stress in living cells. Thus, PTDHP can not only control the intracellular oxidative stress effectively and suppress ROS to some degree in dark, but also regulate its anti-oxidative effect under light irradiation.     

Protective effects of grape seed extract fractions with different degrees of polymerisation on blood glucose,lipids and hepatic oxidative stress in diabetic rats

The purpose of this study was to evaluate the effect of grape seed procyanidin (GSPE) fractions with different degrees of polymerisation (DPs) on blood glucose, lipids and hepatic oxidative stress in diabetic rats. Diabetic rats received a daily oral supplement of GSPE with different DPs for 6 weeks. During this period, blood glucose, body weight and food intake were assessed weekly. At the end of the experiment, serum lipid and hepatic oxidative stress were assessed compared with those of rats that did not receive GSPE. GSPE significantly decreased blood glucose, serum lipids and hepatic oxidative stress. Moreover, these effects were significantly better in the groups administered the oligomeric rather than the polymeric forms. These results demonstrate that GSPE has a positive effect on diabetes in rats, and the oligomeric form of GSPE may be more protective than other forms.     

Protective Effects of 6-Shogaol,an Active Compound of Ginger,in a Murine Model of Cisplatin-Induced Acute Kidney Injury

Acute kidney injury (AKI) is a dose-limiting side effect of cisplatin therapy in cancer patients. However, effective therapies for cisplatin-induced AKI are not available. Oxidative stress, tubular cell death, and inflammation are known to be the major pathological processes of the disease. 6-Shogaol is a major component of ginger and exhibits anti-oxidative and anti-inflammatory effects. Accumulating evidence suggest that 6-shogaol may serve as a potential therapeutic agent for various inflammatory diseases. However, whether 6-shogaol exerts a protective effect on cisplatin-induced renal side effect has not yet been determined. The aim of this study was to evaluate the effect of 6-shogaol on cisplatin-induced AKI and to investigate its underlying mechanisms. An administration of 6-shogaol after cisplatin treatment ameliorated renal dysfunction and tubular injury, as shown by a reduction in serum levels of creatinine and blood urea nitrogen and an improvement in histological abnormalities. Mechanistically, 6-shogaol attenuated cisplatin-induced oxidative stress and modulated the renal expression of prooxidant and antioxidant enzymes. Apoptosis and necroptosis induced by cisplatin were also suppressed by 6-shogaol. Moreover, 6-shogaol inhibited cisplatin-induced cytokine production and immune cell infiltration. These results suggest that 6-shogaol exhibits therapeutic effects against cisplatin-induced AKI via the suppression of oxidative stress, tubular cell death, and inflammation.     

Protective Effect of Ferulic Acid against Hydrogen Peroxide Induced Apoptosis in PC12 Cells

Ferulic Acid (FA) is a highly abundant phenolic phytochemical which is present in plant tissues. FA has biological effects on physiological and pathological processes due to its anti-apoptotic and anti-oxidative properties, however, the detailed mechanism(s) of function is poorly understood. We have identified FA as a molecule that inhibits apoptosis induced by hydrogen peroxide (H₂O₂) or actinomycin D (ActD) in rat pheochromocytoma, PC12 cell. We also found that FA reduces H₂O₂-induced reactive oxygen species (ROS) production in PC12 cell, thereby acting as an anti-oxidant. Then, we analyzed FA-mediated signaling responses in rat pheochromocytoma, PC12 cells using antibody arrays for phosphokinase and apoptosis related proteins. This FA signaling pathway in PC12 cells includes inactivation of pro-apoptotic proteins, SMAC/Diablo and Bad. In addition, FA attenuates the cell injury by H₂O₂ through the inhibition of phosphorylation of the extracellular signal-regulated kinase (ERK). Importantly, we find that FA restores expression levels of brain-derived neurotrophic factor (BDNF), a key neuroprotective effector, in H₂O₂-treated PC12 cells. As a possible mechanism, FA increases BDNF by regulating microRNA-10b expression following H₂O₂ stimulation. Taken together, FA has broad biological effects as a neuroprotective modulator to regulate the expression of phosphokinases, apoptosis-related proteins and microRNAs against oxidative stress in PC12 cells.     

Stevioside Attenuates Insulin Resistance in Skeletal Muscle by Facilitating IR/IRS-1/Akt/GLUT 4 Signaling Pathways: An In Vivo and In Silico Approach

Type-2 diabetes mellitus (T2DM), the leading global health burden of this century majorly develops due to obesity and hyperglycemia-induced oxidative stress in skeletal muscles. Hence, developing novel drugs that ameliorate these pathological events is an immediate priority. The study was designed to analyze the possible role of Stevioside, a characteristic sugar from leaves of Stevia rebaudiana (Bertoni) on insulin signaling molecules in gastrocnemius muscle of obesity and hyperglycemia-induced T2DM rats. Adult male Wistar rats rendered diabetic by administration of high fat diet (HFD) and sucrose for 60 days were orally administered with SIT (20 mg/kg/day) for 45 days. Various parameters were estimated including fasting blood glucose (FBG), serum lipid profile, oxidative stress markers, antioxidant enzymes and expression of insulin signaling molecules in diabetic gastrocnemius muscle. Stevioside treatment improved glucose and insulin tolerances in diabetic rats and restored their elevated levels of FBG, serum insulin and lipid profile to normalcy. In diabetic gastrocnemius muscles, Setvioside normalized the altered levels of lipid peroxidase (LPO), hydrogen peroxide (H₂O₂) and hydroxyl radical (OH*), antioxidant enzymes (CAT, SOD, GPx and GSH) and molecules of insulin signaling including insulin receptor (IR), insulin receptor substrate-1 (IRS-1) and Akt mRNA levels. Furthermore, Stevioside enhanced glucose uptake (GU) and oxidation in diabetic muscles by augmenting glucose transporter 4 (GLUT 4) synthesis very effectively in a similar way to metformin. Results of molecular docking analysis evidenced the higher binding affinity with IRS-1 and GLUT 4. Stevioside effectively inhibits oxidative stress and promotes glucose uptake in diabetic gastrocnemius muscles by activating IR/IRS-1/Akt/GLUT 4 pathway. The results of the in silico investigation matched those of the in vivo study. Hence, Stevioside could be considered as a promising phytomedicine to treat T2DM.