Antidiabetic effect of secoisolariciresinol diglucoside in streptozotocin-induced diabetic rats

Combination therapy of systemic and local metformin improves imiquimod-induced psoriasis-like lesions with type 2 diabetes: the role of AMPK/KGF/STAT3 axis

CONTEXT

Insulin resistance and a disturbed lipid profile are common associations with type 2 diabetes mellitus (T2DM) and different skin diseases, particularly psoriasis (PsO).

OBJECTIVES

We investigated potential therapeutic mechanisms of metformin in a murine animal model of psoriasiform lesions in T2DM.

MATERIALS AND METHODS

Forty-two rats were randomly divided into control, PsO, and type II DM (T2DM) groups. After confirmation of DM, the type II diabetic rats were allocated into T2DM+ PsO, T2DM+ PsO+ systemic metformin (S. met), T2DM+ PsO+ topical metformin (T. met)), and T2DM+ PsO + combined metformin (C. met). PsO was induced by topical imiquimod.

RESULTS

Systemic administration of the cornerstone antidiabetic drug, metformin, was able to improve insulin resistance and lipid profile. At molecular levels, both topical and systemic metformin significantly increased AMP-activated protein kinase (AMPK), and lowered keratinocyte growth factor (KGF) / "Signal transducer and activator of transcription" (STAT)3 protein levels, and the IL-17RA and IL-17RC gene expression.

CONCLUSION

Although its glucose-controlling effect was not optimum, T.met gel served anti-psoriatic and anti-inflammatory effects.

Reductive stress in mitochondria isolated from the carotid body of type 1 diabetic male Wistar rats

The carotid body (CB) senses changes in arterial O2 partial pressure (pO2) and glucose levels; therefore, it is key for the detection of hypoxia and hypoglycemia. The CB has been suggested to detect pO2 through an increase in reactive oxygen species (ROS) in the mitochondria. However, the mechanism protecting the chemoreceptor cells and their mitochondria from ROS and hyperglycemia is poorly understood. Here we measured glutathione levels in CB mitochondria of control and in streptozotocin (STZ)-induced type 1 diabetic male Wistar rats. We found a dramatic reduction in total glutathione from 11.45 ± 1.30 μmol/mg protein in control rats to 1.45 ± 0.31 μmol/mg protein in diabetic rats. However, the ratio of reduced to oxidized glutathione, a measure of the redox index, was increased in diabetic rats compared to controls. We conclude that the mitochondria of CB chemoreceptor cells in type 1 diabetic male Wistar rats were likely under glutathione-reducing stress.

Antioxidant, Anti-Inflammatory, Anti-Menopausal, and Anti-Cancer Effects of Lignans and Their Metabolites

Since chronic inflammation can be seen in severe, long-lasting diseases such as cancer, there is a high demand for effective methods to modulate inflammatory responses. Among many therapeutic candidates, lignans, absorbed from various plant sources, represent a type of phytoestrogen classified into secoisolariciresionol (Seco), pinoresinol (Pino), matairesinol (Mat), medioresinol (Med), sesamin (Ses), syringaresinol (Syr), and lariciresinol (Lari). Lignans consumed by humans can be further modified into END or ENL by the activities of gut microbiota. Lignans are known to exert antioxidant and anti-inflammatory activities, together with activity in estrogen receptor-dependent pathways. Lignans may have therapeutic potential for postmenopausal symptoms, including cardiovascular disease, osteoporosis, and psychological disorders. Moreover, the antitumor efficacy of lignans has been demonstrated in various cancer cell lines, including hormone-dependent breast cancer and prostate cancer, as well as colorectal cancer. Interestingly, the molecular mechanisms of lignans in these diseases involve the inhibition of inflammatory signals, including the nuclear factor (NF)-κB pathway. Therefore, we summarize the recent in vitro and in vivo studies evaluating the biological effects of various lignans, focusing on their values as effective anti-inflammatory agents.

Distribution, biosynthesis and therapeutic potential of lignans

Lignans have long been known for their abundant therapeutic properties due to their polyphenolic structure. Linseed is the richest plant source of lignans and has been studied widely for their properties. The most prevalent lignan, secoisolariciresinol diglucoside (SDG), is consumed with linseed and converted into mammalian lignans, enterodiol (END) and enterolactone (ENL), by the gut microbiota. SDG can easily be assessed using HPLC and its deglycosylated form viz secoisolariciresinol can be asses using GC-MS techniques. Variety of extraction and analysis methods has been reported for plant lignans. SDG is known to have therapeutic properties including anti-oxidant, anti-cancerous, anti-inflammatory, modulation of gene expression, anti-diabetic, estrogenic and anti-estrogenic. Despite a large number of bioactivities, strong evidences for the underlying mechanisms for most of the properties are still unknown. SDG is most studied for its anti-cancerous properties. But the use of lignans as anti-carcinogenic agent is limited and commercially not reported due to challenges of purification at commercial level, rapid metabolism, untargeted delivery and toxic compounds associated with lignans. Exploration of more prominent and active derivatives of SDG and their targeted drug delivery should be an important research toward the use of bioactive lignans of linseed.

Lariciresinol Displays Anti-Diabetic Activity through Inhibition of α-Glucosidase and Activation and Enhancement of Insulin Signaling

SCOPE

The aim of this study is to investigate the antidiabetic effect of lariciresinol (LSR) in C2C12 myotubes and streptozotocin (STZ)-induced diabetic mice.

METHODS AND RESULTS

To investigate antidiabetic potential of LSR, α-glucosidase inhibitory assay, molecular docking, glucose uptake assay, western blot assay on antidiabetic biomarkers are performed. STZ-induced diabetic model is used for in vivo study by calculating oral glucose tolerance test, histochemical examination, and glycogen assay. LSR inhibits α-glucosidase activity with an IC₅₀ value of 6.97 ± 0.37 µM and acts as a competitive inhibitor with an inhibitory constant (Ki) value of 0.046 µM. In C2C12 cells, LSR activates insulin signaling leading to glucose transporter 4 (GLUT4) translocation and augmented glucose uptake. Furthermore, in Streptozotocin (STZ)-treated diabetic mice, 3 weeks of oral LSR administration (10 mg kg^-1 ) considerably decrease blood glucose levels, while increasing insulin levels in an oral glucose tolerance test, improve pancreatic islet size, increase GLUT4 expression, and significantly enhance insulin signaling in skeletal muscle. LSR treatment also activates glycogen synthase kinase 3β (GSK-3β) resulting in improved glycogen content.

CONCLUSION

The findings indicate a potential usefulness for oral LSR in the management and prevention of diabetes by enhancing glucose homeostasis.

Effects of alcoholic extract of Terminalia Chebula dried fruit on blood biochemical profile in diabetic rats

Background

A considerable amount of attention has been recently paid to the discovery of effective natural antidiabetic drugs. Terminalia chebula is considered as the mother of herbs, with reported antidiabetic activity. This study aims to evaluate the renal and hepatic protective profile of its antidiabetic therapeutic doses.

Methods

To achieve the aim of the study, a total of 66 adult male rats of Sprague-Dawley species weighing about 180-200 g (weighed using a digital scale) were used. Type 2 diabetes mellitus (T2DM) was induced in using streptozotocin (STZ), rats were given a 5% dextrose solution for the next 24 h. Subjects received oral treatment of Terminalia chebula ethanolic extract at different doses (200, 400, and 600 mg/kg body weight) for 28 days. Measurements of fasting blood glucose level, change in body weight, lipid profile, serum liver enzymes, serum renal parameter, and histopathology of liver and kidney were carried out.

Results

Higher doses of Terminalia chebula (600 mg/Kg) were shown to have a potential therapeutic effect as well as the most prominent antidiabetic, antilipidemic activity, hepatoprotective and renoprotective profiles when compared to lower doses.

Conclusion

The use of Terminalia chebula alone or in combination with conventional antidiabetic drugs may be beneficial as a new advent therapy for diabetes.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40200-021-00951-8.

Plant polyphenols mechanisms of action on insulin resistance and against the loss of pancreatic beta cells

Diabetes mellitus describes a group of metabolic disorders characterized by a prolonged period hyperglycemia with long-lasting detrimental effects on the cardiovascular and nervous systems, kidney, vision, and immunity. Many plant polyphenols are shown to have beneficial activity for the prevention and treatment of diabetes, by different mechanisms. This review article is focused on synthesizing the mechanisms by which polyphenols decrease insulin resistance and inhibit loss of pancreatic islet β-cell mass and function. To achieve the objectives, this review summarizes the results of the researches realized in recent years in clinical trials and in various experimental models, on the effects of foods rich in polyphenols, polyphenolic extracts, and commercially polyphenols on insulin resistance and β-cells death. Dietary polyphenols are able to reduce insulin resistance alleviating the IRS-1/PI3-k/Akt signaling pathway, and to reduce the loss of pancreatic islet β-cell mass and function by several molecular mechanisms, such as protection of the surviving machinery of cells against the oxidative insult; increasing insulin secretion in pancreatic β-cells through activation of the FFAR1; cytoprotective effect on β-cells by activation of autophagy; protection of β-cells to act as activators for anti-apoptotic pathways and inhibitors for apoptotic pathway; stimulating of insulin release, presumably by transient ATP-sensitive K⁺ channel inhibition and whole-cell Ca²⁺ stimulation; involvement in insulin release that act on ionic currents and membrane potential as inhibitor of delayed-rectifier K⁺ current (I_K(DR)) and activator of current. dietary polyphenols could be used as potential anti-diabetic agents to prevent and alleviate diabetes and its complications, but further studies are needed.

High-yield production of secoisolariciresinol diglucoside from flaxseed hull by extraction with alcoholic ammonium hydroxide and chromatography on microporous resin

This study used alcoholic ammonium hydroxide to directly hydrolyze and extract secoisolariciresinol diglucoside (SDG) from flaxseed hull in a one pot reaction. The optimal extraction conditions, including the concentration of ammonium hydroxide, extraction time, and temperature, were examined in single factor experiments, followed by response surface methodology (RSM) with 3-level, 3-factor Box-Behnken experiments. As a result, the optimal extraction conditions were determined as follows: material-liquid ratio 1:20, percentage of reagent ammonium hydroxide (25–28% of NH3 in water) in ethanol 33.7% (pH = 12.9), extraction time 4.9 h, and extraction temperature 75.3 °C. Under these conditions, the yield of SDG, as measured by ultra-high-performance liquid chromatography-mass spectrometry, was 23.3 mg/g, consistent with the predicted content of SDG in flaxseed hull (23.0 mg/g). Further, 30.0 g of pulverized flaxseed hull was extracted under the optimal conditions, and the extract was subjected to a single run of macroporous resin chromatography to obtain 772.1 mg of a fraction with an SDG content exceeding 76.1%. Subsequent chromatography on Sephadex LH20, yielded 602.8 mg SDG of 98.0% purity, and the yield was 20.1 mg/g (2.0%) from flaxseed hulls. Thus, one-pot hydrolysis and extraction of SDG using alcoholic ammonium hydroxide is simple, and of high-yield.

Graphical abstract

Sustained In Vitro and In Vivo Delivery of Metformin from Plant Pollen-Derived Composite Microcapsules

We developed a dual microencapsulation platform for the type 2 diabetes drug metformin (MTF), which is aimed to increase its bioavailability. We report the use of Lycopodium clavatum sporopollenin (LCS), derived from their natural spores, and raw Phoenix dactylifera L. (date palm) pollens (DPP) for MTF microencapsulation. MTF was loaded into LCS and DPP via a vacuum and a novel method of hydration-induced swelling. The loading capacity (LC) and encapsulation efficiency (EE) percentages for MTF-loaded LCS and MTF-loaded DPP microcapsules were 14.9% ± 0.7, 29.8 ± 0.8, and 15.2% ± 0.7, 30.3 ± 1.0, respectively. The release of MTF from MTF-loaded LCS microcapsules was additionally controlled by re-encapsulating the loaded microcapsules into calcium alginate (ALG) microbeads via ionotropic gelation, where the release of MTF was found to be significantly slower and pH-dependent. The pharmacokinetic parameters, obtained from the in vivo study, revealed that the relative bioavailability of the MTF-loaded LCS-ALG beads was 1.215 times higher compared to pure MTF, following oral administration of a single dose equivalent to 25 mg/kg body weight MTF to streptozotocin (STZ)-induced diabetic male Sprague-Dawley rats. Significant hypoglycemic effect was obtained for STZ-induced diabetic rats orally treated with MTF-loaded LCS-ALG beads compared to control diabetic rats. Over a period of 29 days, the STZ-induced diabetic rats treated with MTF-loaded LCS-ALG beads showed a decrease in the aspartate aminotransferase (AST), alanine aminotransferase (ALT), triglycerides, cholesterol, and low-density lipoprotein-cholesterol (LDL-C) levels, as well as an increase in glutathione peroxidase (GPx) and a recovery in the oxidative stress biomarker, lipid peroxidation (LPx). In addition, histopathological studies of liver, pancreas, kidney, and testes suggested that MTF-loaded LCS-ALG beads improved the degenerative changes in organs of diabetic rats. The LCS-ALG platform for dual encapsulation of MTF achieved sustained MTF delivery and enhancement of bioavailability, as well as the improved biochemical and histopathological characteristics in in vivo studies, opening many other intriguing applications in sustained drug delivery.

Flaxseed Lignans and Polyphenols Enhanced Activity in Streptozotocin-Induced Diabetic Rats

Simple Summary

Diabetes mellitus is a metabolic condition that affects millions of people globally. The present study highlights the enhanced activity of flaxseed lignans and polyphenols isolated from Linum usitatissimum in streptozotocin (STZ)-induced diabetic rats. Treatment with flaxseed extract showed enhanced glycosylated hemoglobin and blood glucose levels and reduced plasma cholesterol, low-density lipoprotein (LDL) cholesterol and triglycerides, urea and uric acid intensities, and plasma creatinine in the treated diabetic experimental animals, indicating beneficial effects—results sustained by histopathological observations of liver, pancreas, kidney, and spleen. Translation of this nutraceutical-based approach still requires further elucidation of its mechanism of action toward clinical applications.

Abstract

Flaxseeds play an important role in human health due to their chemical composition and recognized beneficial outcomes. This study investigated the antidiabetic effects of present lignans and polyphenols found in the flaxseed extract on streptozotocin (STZ)-induced diabetic rats. The flaxseed administration produced favorable changes in body weight, food and water intake, and glycosylated hemoglobin and blood glucose quantities in the treated diabetic rats. Additionally, significant positive results were observed in the biochemical parameters, namely reduced plasma cholesterol, LDL cholesterol and triglycerides, plasma creatinine, and urea and uric acid levels, highlighting the seeds’ use in traditional medicine. The results were sustained by histopathological observations that showed better tissue preservation following the flaxseed diet. Overall, the consumption of flaxseeds produced moderate reduction in glucose levels and hyperlipidemia, together with improvement in the impaired organs’ function in diabetic rats. The daily administration of polyphenols and lignans compounds could impact therapeutic potential in diabetes management.

Secoisolariciresinol diglucoside protects against cadmium-induced oxidative stress-mediated renal toxicity in rats

BACKGROUND

Cadmium is a well known environmental pollutant and strong toxic heavy metal, that causes oxidative damage to various organs of the body, including the kidney. Cadmium (II) chloride (CdCl2) is a water-soluble crystalline form, which exhibits a higher affinity with chlorides at the target site. The current study examined the protective effects of Secoisolariciresinol diglucoside (SDG), a principal lignan extracted from flaxseeds against CdCl2-induced renal toxicity in rats.

METHODS

Twenty four healthy male Wistar rats with four groups of six animals each were used in the study. Group-1- Control was administered with saline. Group-2 -was treated with SDG; Group-3 with CdCl2 alone, and Group-4 were treated with CdCl2 plus SDG. The effect of Cd on kidney was assessed in terms of various parameters like lipid peroxidation, production of Nitric oxide (NO) and Myeloperoxidase (MPO), and kidney function markers like uric acid, urea, and creatinine. The levels of antioxidant molecules like glutathione content and the activities of superoxide dismutase, catalase, glutathione peroxidase, and glutathione reductase were also measured, apart from histopathological studies.

RESULTS

The animals that received CdCl2, exhibited changes in the concentration of Cd in the kidney. The levels of kidney function markers like uric acid, urea, and creatinine were found to be abnormal in serum, and also there was a drastic decrease in the levels of glutathione content and the activities of superoxide dismutase, catalase, glutathione peroxidase, and glutathione reductase. The treatment of SDG significantly decreased (p < 0.05) the levels of NO and MPO in the animals treated with CdCl2 plus SDG when compared to the animal group treated with CdCl2 alone. The treatment of SDG before CdCl2 injection exhibited significant changes in the activity of the antioxidant enzymes, which was evidenced by the restoration in their activities, when compared to CdCl2 alone treated group (p < 0.05), as observed in the results of histopathology.

CONCLUSIONS

The findings of the present investigation suggested that SDG exhibited anti-oxidant, anti-apoptotic and renoprotective properties. Thus, SDG may act as a supramolecular binding component and naturally occurring metal chelating agent for metal cations like Cd2+. Therefore, flaxseed lignan-SDG can be used as a therapeutic agent against nephrotoxicity caused by cadmium. However, detailed future studies are needed to know the underlying mechanism of action of SDG against the Cd and other heavy metals induced nephrotoxicity.

Lignans from linseed (Linum usitatissimum L.) and its allied species: Retrospect, introspect and prospect

Lignans are complex diphenolic compounds representing phytoestrogens and occur widely across the plant kingdom. Formed by the coupling of two coniferyl alcohol residues, lignans constitute major plant "specialized metabolites" with exceptional biological attributes that aid in plant defence and provide health benefits in humans by reducing the risk of ailments such as cancer, diabetes etc. Linseed (Linum usitatissimum L.) is one of the richest sources of lignans followed by cereals and legumes. Among the various types of lignans, secoisolariciresinol diglucoside (SDG) is considered as the essential and nutrient rich lignan in linseed. Lignans exhibit established antimitotic, antiviral and anti-tumor properties that contribute to their medicinal value. The present review seeks to provide a holistic view of research in the past and present times revolving around lignans from linseed and its allied species. This review attempts to elucidate sources, structures and functional properties of lignans, along with detailed biosynthetic mechanisms operating in plants. It summarizes various methods for the determination of lignan content in plants. Biotechnological interventions (in planta and in vitro) aimed at enriching lignan content and adoption of integrative approaches that might further enhance lignan content and medicinal and nutraceutical value of Linum spp. have also been discussed.

Ophiopogonin D of Ophiopogon japonicus ameliorates renal function by suppressing oxidative stress and inflammatory response in streptozotocin-induced diabetic nephropathy rats

Ophiopogonin D (OP-D) is the principal pharmacologically active ingredient from Ophiopogon japonicas, which has been demonstrated to have numerous pharmacological activities. However, its protective effect against renal damage in streptozotocin (STZ)-induced diabetic nephropathy (DN) rats remains unclear. The present study was performed to investigate the protective effect of OP-D in the STZ-induced DN rat model. DN rats showed renal dysfunction, as evidenced by decreased serum albumin and creatinine clearance, along with increases in serum creatinine, blood urea nitrogen, TGF-β1, and kidney hypertrophy, and these were reversed by OP-D. In addition, STZ induced oxidative damage and inflammatory response in diabetic kidney tissue. These abnormalities were reversed by OP-D treatment. The findings obtained in the present study indicated that OP-D might possess the potential to be a therapeutic agent against DN via inhibiting renal inflammation and oxidative stress.

Natural Products Derived from the Mediterranean Diet with Antidiabetic Activity: from Insulin Mimetic Hypoglycemic to Nutriepigenetic Modulator Compounds

BACKGROUND

The Mediterranean diet is a healthy eating pattern that protects against the development of Type 2 diabetes mellitus (T2DM), a metabolic disease characterized by elevated blood sugar levels due to pancreatic beta-cell functional impairment and insulin resistance in various tissues. Inspired by the ancient communities, this diet emphasizes eating primarily plant-based foods, including vegetables, legumes, fruits, cereals, and nuts. Importantly, virgin olive oil is used as the principal source of fat. Red meat is consumed in low amounts while wine and fish are consumed moderately.

OBJECTIVE

Here, we review the most beneficial components of the Mediterranean Diet and tentative mechanisms of action for prevention and/or management of T2DM, based on research conducted within the last decade.

METHODS

The references over the last five years have been reviewed and they have been selected properly according to inclusion/ exclusion criteria.

RESULTS

Several bioactive diet components were evaluated to prevent inflammation and cytokine-induced oxidative damage, reduce glucose concentration, carbohydrate absorption and increase insulin sensitivity and related gene expression.

CONCLUSION

The adherence to a healthy lifestyle, including diet, exercise and habits remains the best approach for the prevention of diabetes as well as frequent check-ups and education. Though diabetes has a strong genetic component, in recent years many reports strongly point to the critical role of lifestyle specific epigenetic modifications in the development of T2DM. It remains to be established how different components of the Mediterranean Diet interact and influence the epigenetic landscape to prevent or treat the disease.

Effects of Maternal Flaxseed Supplementation on Female Offspring of Diabetic Rats in Serum Concentration of Glucose, Insulin, and Thyroid Hormones

Objective: This study aimed to evaluate the effect of maternal consumption of flaxseed flour and oil on serum concentrations of glucose, insulin, and thyroid hormones of the adult female offspring of diabetic rats. Methods: Wistar rats were induced to diabetes by a high-fat diet (60%) and streptozotocin (35 mg/kg). Rats were mated and once pregnancy was confirmed, were divided into the following groups: Control Group (CG): casein-based diet; High-fat Group (HG): high-fat diet (49%); High-fat Flaxseed Group (HFG): high-fat diet supplemented with 25% flaxseed flour; High-fat Flaxseed Oil group (HOG): high-fat diet, where soya oil was replaced with flaxseed oil. After weaning, female pups (n = 6) from each group were separated, received a commercial rat diet and were sacrificed after 180 days. Serum insulin concentrations were determined by ELISA, the levels of triiodothyronine (T3), thyroxine (T4) and thyroid-stimulating hormone (TSH) were determined by chemiluminescence. Results: There was a significant reduction in body weight at weaning in HG (-31%), HFG (-33%) and HOG (44%) compared to CG (p = 0.002), which became similar by the end of 180 days. Blood glucose levels were reduced in HFG (-10%, p = 0.044) when compared to CG, and there was no significant difference between groups in relation to insulin, T3, T4, and TSH after 180 days. Conclusions: Maternal severe hyperglycemia during pregnancy and lactation resulted in a microsomal offspring. Maternal consumption of flaxseed reduces blood glucose levels in adult offspring without significant effects on insulin levels and thyroid hormones.

Antidiabetic Activity of Sargassum hystrix Extracts in Streptozotocin-Induced Diabetic Rats

The objective of this research was to determine the potential effects of Sargassum hystrix extracts (SHE) on the glucose levels, lipid profile, and pancreas of streptozotocin (STZ)-induced diabetic rats. SHE at 200, 300, and 400 mg/kg was administered orally to STZ-induced diabetic rats once daily for 15 days. Glucose levels, lipid profile, and weight of rats were measured in the normal state and on the 15th day. The histology of the pancreas was observed on the 15th day. The results showed that the preprandial and postprandial glucose levels in the group treated with SHE at 300 mg/kg were significantly reduced compared with those of the diabetes group. Additionally, the levels of triglycerides and cholesterol in the 300 mg/kg SHE group were significantly different from those in the diabetes group. However, the levels of high-density lipoprotein cholesterol and low-density lipoprotein cholesterol across the treatment groups did not have significant differences. Necrosis was found in all STZ-induced rats. SHE at a dose of 300 mg/kg had the best capability to lower the levels of preprandial and postprandial glucose and to prevent necrosis in diabetic rats.

Secoisolariciresinol diglucoside attenuates cardiac hypertrophy and oxidative stress in monocrotaline-induced right heart dysfunction

Pulmonary arterial hypertension (PAH) occurs when remodeling of pulmonary vessels leads to increased pulmonary vascular resistance resulting in increased pulmonary arterial pressure. Increased pulmonary arterial pressure results in right ventricle hypertrophy and eventually heart failure. Oxidative stress has been implicated in the pathogenesis of PAH and may play a role in the regulation of cellular signaling involved in cardiac response to pressure overload. Secoisolariciresinol diglucoside (SDG), a component from flaxseed, has been shown to reduce cardiac oxidative stress in various pathophysiological conditions. We investigated the potential protective effects of SDG in a monocrotaline-induced model of PAH. Five- to six-week-old male Wistar rats were given a single intraperitoneal injection of monocrotaline (60 mg/kg) and sacrificed 21 days later where heart, lung, and plasma were collected. SDG (25 mg/kg) was given via gavage as either a 21-day co-treatment or pre-treatment of 14 days before monocrotaline administration and continued for 21 days. Monocrotaline led to right ventricle hypertrophy, increased lipid peroxidation, and elevated plasma levels of alanine transaminase (ALT) and aspartate transaminase (AST). Co-treatment with SDG did not attenuate hypertrophy or ALT and AST levels but decreased reactive oxygen species (ROS) levels and catalase and superoxide dismutase activity compared to the monocrotaline-treated group. Pre-treatment with SDG decreased right ventricle hypertrophy, ROS levels, lipid peroxidation, catalase, superoxide dismutase, and glutathione peroxidase activity and plasma levels of ALT and AST when compared to the monocrotaline group. These findings indicate that pre-treatment with SDG provided better protection than co-treatment in this model of right heart dysfunction, suggesting an important role for SDG in PAH and right ventricular remodeling.

Protective effect of Sophoraflavanone G on streptozotocin (STZ)-induced inflammation in diabetic rats

The present study was designed to investigate the protective effect of Sophoraflavanone G (SG) on streptozotocin (STZ)-induced diabetic rats. The rats were intraperitoneally injected with STZ (35mg/kg). 7days later, the rats were intragastrically administered with Metformin (MET, 150mg/kg), SG (20mg/kg) or SG (40mg/kg) once daily for consecutive 30 days. The animals were anaesthetized, the blood and liver samples were also collected for further assay. SG significantly decreased the serum levels of glucose, insulin, aspartate transaminase (AST), alanine aminotransferase (ALT). In addition, SG increased superoxide dismutase (SOD) activity and inhibited malondialdehyde (MDA) content in serum. SG also ameliorated the histopathological condition. Furthermore, SG attenuated the expressions of thioredoxin (Trx), thioredoxin-interacting protein (Txnip) and the phosphorylations of inhibitory kappa B kinase (IKK)α, IKKβ, nuclear factor-κB inhibitory proteins (IκB)α, nuclear factor κB (NF-κB). These findings demonstrated that SG showed beneficial effects on STZ-induced diabetic rats.

Antioxidant activity of milk protein hydrolysate in alloxan-induced diabetic rats

We investigated the effects of milk protein concentrate (MPC) and milk protein concentrate hydrolysate (MPCH) as antioxidant agents in rats. Six groups of healthy (non-diabetic) and type-II diabetic rats were used: (1) healthy rats (control), (2) alloxan-induced rats (diabetic control group), (3) healthy rats treated orally with MPC, (4) diabetic rats treated orally with MPC, (5) healthy rats treated orally with MPCH, and (6) diabetic rats treated orally with MPCH. We concluded that treatment with MPC or MPCH reduced the level of thiobarbituric acid reactive substances in healthy and diabetic rats. Treatment with MPC or MPCH improved activities of antioxidant enzymes (catalase, superoxide dismutase, reduced glutathione, glutathione-S-transferase, and glutathione peroxidase) in healthy and diabetic rats. From the present data, we concluded that both MPC and MPCH contain potent antioxidants and could improve the health of rats or other animals with diabetes mellitus.

Total saponin of Dioscoreae hypoglaucae rhizoma ameliorates streptozotocin-induced diabetic nephropathy

BACKGROUND

Diabetic nephropathy has become the most common cause of morbidity and mortality in diabetic patients. Therefore, there is an urgent need for more effective and safer drugs for use in this condition.

PURPOSE

The aims of this study were to investigate the ameliorative effects of total saponin of Dioscoreae hypoglaucae rhizoma (TSD) on diabetic nephropathy and to explore the potential underlying mechanism(s).

METHODS

Rats with streptozotocin-induced diabetes were orally treated with TSD at 40, 80, and 160 mg/kg/d for 12 weeks. At the end of the treatment, blood, urine, and kidneys were collected for biochemical and histological examination.

RESULTS

The results demonstrated that TSD significantly decreased the fasting blood glucose, glycosylated hemoglobin, urinary protein, serum creatinine, and blood urea nitrogen levels in diabetic rats. The results of histological examinations showed that TSD ameliorated glomerular and tubular pathological changes in diabetic rats. Furthermore, TSD significantly prevented oxidative stress and reduced the renal levels of advanced glycation end products, transforming growth factor-β1, connective tissue growth factor, and tumor necrosis factor-α.

CONCLUSION

This study demonstrated the renoprotective effects of TSD in experimental diabetic nephropathy via a number of different mechanisms.

Antihyperglycemic and antihyperlipidemic activities of protodioscin in a high-fat diet and streptozotocin-induced diabetic rats

Protodioscin attenuated hyperglycaemia and dyslipidemia in diabetic rats by improving the insulin sensitivity and increasing adiponectin concentrations.

Secoisolariciresinol diglycoside, a flaxseed lignan, exerts analgesic effects in a mouse model of type 1 diabetes: Engagement of antioxidant mechanism

Peripheral painful neuropathy is one of the most common complications in diabetes and necessitates improved treatment. Secoisolariciresinol diglycoside (SDG), a predominant lignan in flaxseed, has been shown in our previous studies to exert antidepressant-like effect. As antidepressant drugs are clinically used to treat chronic neuropathic pain, this work aimed to investigate the potential analgesic efficacy of SDG against diabetic neuropathic pain in a mouse model of type 1 diabetes. We subjected mice to diabetes by a single intraperitoneal (i.p.) injection of streptozotocin (STZ, 200 mg/kg), and Hargreaves test or von Frey test was used to assess thermal hyperalgesia or mechanical allodynia, respectively. Chronic instead of acute SDG treatment (3, 10 or 30 mg/kg, p.o., twice per day for three weeks) ameliorated thermal hyperalgesia and mechanical allodynia in diabetic mice, and these analgesic actions persisted about three days when SDG treatment was terminated. Although chronic treatment of SDG to diabetic mice did not impact on the symptom of hyperglycemia, it greatly attenuated excessive oxidative stress in sciatic nerve and spinal cord tissues, and partially counteracted the condition of weight decrease. Furthermore, the analgesic actions of SDG were abolished by co-treatment with the reactive oxygen species donor tert-butyl hydroperoxide (t-BOOH), but potentiated by the reactive oxygen species scavenger phenyl-N-tert-butylnitrone (PBN). These findings indicate that chronic SDG treatment can correct neuropathic hyperalgesia and allodynia in mice with type 1 diabetes. Mechanistically, the analgesic actions of SDG in diabetic mice may be associated with its antioxidant activity.

Ionic Liquid-Based Ultrasonic-Assisted Extraction of Secoisolariciresinol Diglucoside from Flaxseed (Linum usitatissimum L.) with Further Purification by an Aqueous Two-Phase System

In this work, a two-step extraction methodology of ionic liquid-based ultrasonic-assisted extraction (IL-UAE) and ionic liquid-based aqueous two-phase system (IL-ATPS) was developed for the extraction and purification of secoisolariciresinol diglucoside (SDG) from flaxseed. In the IL-UAE step, several kinds of ILs were investigated as the extractants, to identify the IL that affords the optimum extraction yield. The extraction conditions such as IL concentration, ultrasonic irradiation time, and liquid–solid ratio were optimized using response surface methodology (RSM). In the IL-ATPS step, ATPS formed by adding kosmotropic salts to the IL extract was used for further separation and purification of SDG. The most influential parameters (type and concentration of salt, temperature, and pH) were investigated to obtain the optimum extraction efficiency. The maximum extraction efficiency was 93.35% under the optimal conditions of 45.86% (w/w) IL and 8.27% (w/w) Na₂SO₄ at 22 °C and pH 11.0. Thus, the combination of IL-UAE and IL-ATPS makes up a simple and effective methodology for the extraction and purification of SDG. This process is also expected to be highly useful for the extraction and purification of bioactive compounds from other important medicinal plants.

Antioxidative and antiatherogenic effects of flaxseed, α-tocopherol and their combination in diabetic hamsters fed with a high-fat diet

Oxidative stress has previously been shown to play a role in the pathogenesis of diabetes mellitus (DM) and its complications. In the present study, the effects of supplementation with dietary antioxidants, flaxseed and α-tocopherol were investigated in diabetic golden Syrian hamsters fed with a high-fat diet. Thirty-five golden Syrian hamsters were randomly divided into a control group (C) and four diabetic groups (DM, DM + flax, DM + E and DM + Flax + E). The hamsters received four different diets for a 20-week period, as follows: i) Groups C and DM received a high-fat diet (40% energy as fat), deficient in α-linolenic acid (ALA); ii) the DM + Flax group received a high-fat diet enriched with ground flaxseed 15 g/100 g of food, rich in ALA; iii) the DM + E group received a high-fat diet enriched with vitamin E, 40 mg α-tocopherol/100 g of food; and iv) the DM + Flax + E group received a high-fat diet enriched with flaxseed and vitamin E. The results of serum lipid and oxidative stress analysis suggested that the antiatherogenic effect of flaxseed, α-tocopherol and their combination added to a high-fat diet in diabetic hamsters was based primarily on their antioxidative role, demonstrated by decreased serum lipid peroxidation and increased liver glutathione content. Improvements of serum glucose and non-high-density lipoprotein cholesterol (HDL-C) levels were observed and may have contributed to the prevention of diabetic macroangiopathy evidenced in the histopathological examination. The antioxidant effect of flaxseed was similar to that of α-tocopherol in diabetic hamsters fed a high-fat diet and combined supplementation did not appear to bring more benefits than flaxseed alone. Moreover, the high dose of ground flaxseed alone may have a better cardioprotective effect than α-tocopherol in diabetic hamsters by reducing total cholesterol and non-HDL-C levels and increasing HDL-C levels.

Pharmacophore Modeling and Molecular Docking Studies on Pinus roxburghii as a Target for Diabetes Mellitus

The present study attempts to establish a relationship between ethnopharmacological claims and bioactive constituents present in Pinus roxburghii against all possible targets for diabetes through molecular docking and to develop a pharmacophore model for the active target. The process of molecular docking involves study of different bonding modes of one ligand with active cavities of target receptors protein tyrosine phosphatase 1-beta (PTP-1β), dipeptidyl peptidase-IV (DPP-IV), aldose reductase (AR), and insulin receptor (IR) with help of docking software Molegro virtual docker (MVD). From the results of docking score values on different receptors for antidiabetic activity, it is observed that constituents, namely, secoisoresinol, pinoresinol, and cedeodarin, showed the best docking results on almost all the receptors, while the most significant results were observed on AR. Then, LigandScout was applied to develop a pharmacophore model for active target. LigandScout revealed that 2 hydrogen bond donors pointing towards Tyr 48 and His 110 are a major requirement of the pharmacophore generated. In our molecular docking studies, the active constituent, secoisoresinol, has also shown hydrogen bonding with His 110 residue which is a part of the pharmacophore. The docking results have given better insights into the development of better aldose reductase inhibitor so as to treat diabetes related secondary complications.

Neuromodulatory effects of hesperidin in mitigating oxidative stress in streptozotocin induced diabetes

Oxidative stress has been implicated in pathogenesis of streptozotocin- (STZ-) induced diabetes mellitus and its complication in central nervous system (CNS). Recent studies have provided insights on antioxidants and their emergence as potential therapeutic and nutraceutical. The present study examined the hypothesis that hesperidin (HP) ameliorates oxidative stress and may be a limiting factor in the extent of CNS complication following diabetes. To test this hypothesis rats were divided into four groups: control, diabetic, diabetic-HP treated, and vehicle for HP treatment group. Diabetes mellitus was induced by a single injection of STZ (65 mg/kg body weight). Three days after STZ injection, HP was given (50 mg/kg b.wt. orally) once daily for four weeks. The results of the present investigation suggest that the significant elevated levels of oxidative stress markers were observed in STZ-treated animals, whereas significant depletion in the activity of nonenzymatic antioxidants and enzymatic antioxidants was witnessed in diabetic rat brain. Neurotoxicity biomarker activity was also altered significantly. HP treatment significantly attenuated the altered levels of oxidative stress and neurotoxicity biomarkers. Our results demonstrate that HP exhibits potent antioxidant and neuroprotective effects on the brain tissue against the diabetic oxidative damage in STZ-induced rodent model.

Hypoglycemic and hypolipidemic effects of oxymatrine in high-fat diet and streptozotocin-induced diabetic rats

Oxymatrine, a quinolizidine alkaloid, has been widely used for the treatment of hepatitis. In this study, we investigated the hypoglycemic and hypolipidemic effects and new pharmacological activities of oxymatrine, in a high-fat diet and streptozotocin (STZ)-induced diabetic rats. The results demonstrated that oxymatrine could significantly decrease fasting blood glucose, glycosylated hemoglobin (GHb), food and water intake, non-esterified fatty acid (NEFA), total cholesterol (TC), triglyceride (TG), low density lipoprotein cholesterol levels (LDL-c), and increase serum insulin, liver and muscle glycogen, high density lipoprotein cholesterol (HDL-c), glucagon-like peptide-1 (GLP-1) and muscle glucose transporter-4 (GLUT-4) content in diabetic rats. The results of the histological examinations of the pancreas and liver show that oxymatrine protected the islet architecture and prevented disordered structure of the liver. This study displays that oxymatrine can alleviate hyperglycemia and hyperlipemia in a high-fat diet and STZ-induced diabetic rats might by improving insulin secretion and sensitivity.

Erythropoietin attenuates oxidative stress and apoptosis in Schwann cells isolated from streptozotocin-induced diabetic rats

OBJECTIVES

High glucose-evoked oxidative stress and apoptosis within Schwann cells (SCs) are mechanisms facilitating the procession of diabetic peripheral neuropathy (DPN). Although erythropoietin (EPO) was demonstrated to have neuroprotective effects in neurodegenerative diseases, the effects of EPO on glucose-evoked oxidative stress and apoptosis of SCs remain unknown.

METHODS

Primary cultured SCs isolated from streptozotocin (STZ)-induced diabetic peripheral neuropathic rats and normal control rats were exposed to high or normal glucose condition with or without EPO incubation for 72 h. Cell viability, apoptotic rate, cellular reactive oxygen species (ROS) level, total glutathione (GSH) level, EPO mRNA and erythropoietin receptor (EPOR) mRNA levels were assayed.

KEY FINDINGS

SCs from diabetic rats showed a lower cell viability and a higher apoptotic rate. High glucose culture condition elevated ROS level and diminished total GSH level of SCs. EPO improved cell viability and decreased cell apoptotic rate of SCs. EPO also elevated total GSH level and decreased intracellular ROS level. SCs from diabetic rats exhibited higher EPO mRNA and EPOR mRNA levels than SCs from normal control rats.

CONCLUSIONS

The data of this study offered fresh viewpoints for interpreting the pathogenesis of DPN and novel pharmacological principles implicit in the therapeutic effect of EPO.

Low-dose radiation induces renal SOD1 expression and activity in type 1 diabetic mice

PURPOSE

Oxidative stress plays a critical role in the pathogenesis of diabetic nephropathy (DN). As an antioxidant, superoxide dismutase (SOD)-1 deficiency exacerbates but SOD1 supplementation prevents diabetes-induced renal damage. Previously, we have demonstrated that repetitive exposure to low-dose radiation (LDR) at 25 mGy significantly prevents DN. Whether this prevention is related to SOD1 expression and activity remains unknown. The aim of the present study was to explore the effects of different methods of LDR treatment on SOD1 expression and activity in the kidneys of diabetic mice.

MATERIALS AND METHODS

C57BL/6J mice were induced with type 1 diabetes using streptozotocin (STZ). Diabetic mice were irradiated with whole-body X-rays at either a single dose of 25 mGy or 75 mGy, or three doses of 25 mGy and then sacrificed at different times. Body weight, blood glucose level, and renal SOD1 expression and activity were measured.

RESULTS

LDR had no impact on the body weights or blood glucose levels of the mice in either the normal or diabetic groups. A single exposure of LDR at 25 mGy did not preserve renal SOD1 expression and activity in diabetic mice, but a single exposure of LDR at 75 mGy or three exposures of LDR at 25 mGy could preserve them.

CONCLUSION

The stimulation of renal SOD1 expression and activity by a single or cumulative LDR of 75 mGy may be one of the preventive mechanisms of DN observed in the previous study.

Berberine ameliorates experimental diabetes-induced renal inflammation and fibronectin by inhibiting the activation of RhoA/ROCK signaling

The accumulation of glomerular extracellular matrix proteins, especially fibronectin (FN), is a critical pathological characteristic of diabetic renal fibrosis. Inflammation mediated by nuclear factor-κB (NF-κB) plays a critical role in the pathogenesis of diabetic nephropathy (DN). RhoA/ROCK signaling is responsible for FN accumulation and NF-κB activation. Berberine (BBR) treatment significantly inhibited renal inflammation and thus improved renal damage in diabetes. Here, we study whether BBR inhibits FN accumulation and NF-κB activation by inhibiting RhoA/ROCK signaling and the underlying mechanisms involved. Results showed that BBR effectively inhibited RhoA/ROCK signaling activation in diabetic rat kidneys and high glucose-induced glomerular mesangial cells (GMCs) and simultaneously down-regulated NF-κB activity, which was accompanied by reduced intercellular adhesionmolecule-1, transforming growth factor-beta 1 and FN overproduction. Furthermore, we observed that BBR abrogated high glucose-mediated reactive oxygen species generation in GMCs. BBR and N-acetylcysteine inhibited RhoA/ROCK signaling activation in high glucose-exposed GMCs. Collectively, our data suggest that the renoprotective effect of BBR on DN partly depends on RhoA/ROCK inhibition. The anti-oxidative stress effect of BBR is responsible for RhoA/ROCK inhibition in DN.