Introduction to serial review on the role of oxidative stress in diabetes mellitus

Protective Effect of Peptides from Pinctada Martensii Meat on the H2O2-Induced Oxidative Injured HepG2 Cells

Pinctada martensii is a major marine pearl cultured species in southern China, and its meat is rich in protein, which is an excellent material for the preparation of bioactive peptides. In this study, the peptides from Pinctada martensii meat were prepared by simulated gastrointestinal hydrolysis, and after multistep purification, the structures of the peptides were identified, followed by the solid-phase synthesis of the potential antioxidant peptides. Finally, the antioxidant activities of the peptides were verified using HepG2 cells, whose oxidative stress was induced by hydrogen peroxide (H₂O₂). It was shown that the antioxidant peptide (S4) obtained from Pinctada martensii meat could significantly increase the cell viability of HepG2 cells. S4 could also scavenge reactive oxygen species (ROS) and reduce the lactate dehydrogenase (LDH) level. In addition, it could enhance the production of glutathione (GSH) and catalase (CAT) in HepG2 cells, as well as the expression of key genes in the Nrf2 signaling pathway. Three novel antioxidant peptides, arginine-leucine (RL), arginine-glycine-leucine (RGL), and proline-arginine (PR), were also identified. In conclusion, peptides from Pinctada martensii meat and three synthetic peptides (RGL, RL, PR) showed antioxidant activity and could have the potential to be used as antioxidant candidates in functional foods.

Botanical characteristics, chemical components, biological activity, and potential applications of mangosteen

Garcinia mangostana L. (Mangosteen), a functional food, belongs to the Garcinaceae family and has various pharmacological effects, including anti-oxidative, anti-inflammatory, anticancer, antidiabetic, and neuroprotective effects. Mangosteen has abundant chemical constituents with powerful pharmacological effects. After searching scientific literature databases, including PubMed, Science Direct, Research Gate, Web of Science, VIP, Wanfang, and CNKI, we summarized the traditional applications, botanical features, chemical composition, and pharmacological effects of mangosteen. Further, we revealed the mechanism by which it improves health and treats disease. These findings provide a theoretical basis for mangosteen's future clinical use and will aid doctors and researchers who investigate the biological activity and functions of food.

Dietary prenylated flavonoid xanthohumol alleviates oxidative damage and accelerates diabetic wound healing via Nrf2 activation

Diabetic skin ulcer is one of the most common complications in patients suffering diabetes mellitus. Xanthohumol (XN), a hop-derived prenylated dietary flavonoid, has multiple health beneficial bioactivities. In the present study, we reported XN alleviates oxidative damage and accelerates diabetic wound healing via Nrf2 activation. In vitro, XN attenuated hydrogen peroxide (H₂O₂)-induced cytotoxicity, ROS production, cell apoptosis, as well as high glucose-induced cell damage. Mechanistic studies further demonstrated that XN could stabilize nuclear factor erythroid 2-related factor 2 (Nrf2) and promote its nuclear translocation, which was associated with AMPKα activation and covalent modification of Keap1 by XN. In vivo, XN increased Nrf2 expression and accelerated diabetic wound healing. Our study revealed a novel function of XN in diabetic wound healing as well as the underlying molecular mechanisms, suggesting XN is a promising lead compound and a potential food and/or drug candidate for the treatment of diabetic skin ulcers.

The effect of apple vinegar consumption on glycemic indices, blood pressure, oxidative stress, and homocysteine in patients with type 2 diabetes and dyslipidemia: A randomized controlled clinical trial

BACKGROUND

Some foods and drinks contain special ingredients, causing impressive effects on human health. The aim of the current study was to assess the health effects of apple vinegar in patients with diabetes and dyslipidemia.

METHOD

Seventy participants with type 2 diabetes and hyperlipidemia were randomly assigned into an intervention and control group in order to assess the effect of 20 ml apple vinegar per day using an 8-week parallel study. Fasting blood sugar (FBS), homeostasis model assessment for insulin resistance (HOMA-IR), homeostasis model assessment for b-cell function (HOMA-B), quantitative insulin sensitivity checks index (QUICKI), insulin, malondialdehyde (MDA), 2,20-Diphenyl-1- picrylhydrazyl (DPPH), homocysteine, systolic blood pressure (SBP), and diastolic blood pressure (DBP) were measured at the beginning and end of the study.

RESULTS

The intervention with apple vinegar could significantly improve FBS (mean change: -10.16 ± 19.48 mg/dl, p = 0.006) and DPPH (mean change: 16.58 ± 11.56, p < 0.001) within intervention group and in comparison with control group (p < 0.001). Additionally, the significant increase of MDA in control group (p < 0.05) caused a considerable difference between two groups. Glycemic indices containing insulin, HOMA-IR, HOMA-B, and QUICKI decrease significantly in both groups (p < 0.05). No considerable effect was observed on blood pressure and homocysteine in intervention group as well as control group.

CONCLUSION

This trial provided some evidences that apple vinegar consumption may cause beneficial effects on glycemic indices and oxidative stress in individuals with diabetes and dyslipidemia. This randomized clinical trial was registered in the Iranian Registry of Clinical Trials (https://www.irct.ir/) as 2013070710826N5.

Extraction, characterization and antioxidant activity analysis of the polysaccharide from the solid-state fermentation substrate of Inonotus hispidus

A polysaccharide from Inonotus hispidus was prepared by solid-state fermentation (SSF), and an efficient ultrasound-assisted extraction method was used to optimize the extraction process of Inonotus hispidus solid-state fermentation polysaccharide (IHSFP). The optimal extraction parameters were as follows: solid-liquid ratio of 1:40, ultrasound time of 34 min, ultrasound power of 350 W and ultrasound temperature of 70 °C. The yield of IHSFP was 51.06 ± 0.34% under the optimal conditions. Two types of polysaccharide fractions (IHSFP-1 and IHSFP-2) were isolated by DEAE-52 and Sephadex G-200 columns. IHSFP-2 had stronger antioxidant activity than IHSFP-1, and it can reduce H₂O₂-induced oxidative damage to cells in vitro. Therefore, the properties of IHSFP-2 were further characterized. The results showed that the molecular weight of IHSFP-2 was 14.44 kDa, it was composed of glucose (Glc), mannose (Man), galactose (Gal), glucuronic acid (GlcUA), galactosamine (GalN), arabinose (Ara) and ribose (Rib), and the contents of these monosaccharides were 51%, 21%, 20%, 3%, 2%, 2% and 1%, respectively. The results of this study may contribute to the efficient production of the polysaccharide of Inonotus hispidus, and provide new ideas for its application in functional foods and cosmetics.

Overuse injuries in sport: a comprehensive overview

BACKGROUND

The absence of a single, identifiable traumatic cause has been traditionally used as a definition for a causative factor of overuse injury. Excessive loading, insufficient recovery, and underpreparedness can increase injury risk by exposing athletes to relatively large changes in load. The musculoskeletal system, if subjected to excessive stress, can suffer from various types of overuse injuries which may affect the bone, muscles, tendons, and ligaments.

METHODS

We performed a search (up to March 2018) in the PubMed and Scopus electronic databases to identify the available scientific articles about the pathophysiology and the incidence of overuse sport injuries. For the purposes of our review, we used several combinations of the following keywords: overuse, injury, tendon, tendinopathy, stress fracture, stress reaction, and juvenile osteochondritis dissecans.

RESULTS

Overuse tendinopathy induces in the tendon pain and swelling with associated decreased tolerance to exercise and various types of tendon degeneration. Poor training technique and a variety of risk factors may predispose athletes to stress reactions that may be interpreted as possible precursors of stress fractures. A frequent cause of pain in adolescents is juvenile osteochondritis dissecans (JOCD), which is characterized by delamination and localized necrosis of the subchondral bone, with or without the involvement of articular cartilage. The purpose of this compressive review is to give an overview of overuse injuries in sport by describing the theoretical foundations of these conditions that may predispose to the development of tendinopathy, stress fractures, stress reactions, and juvenile osteochondritis dissecans and the implication that these pathologies may have in their management.

CONCLUSIONS

Further research is required to improve our knowledge on tendon and bone healing, enabling specific treatment strategies to be developed for the management of overuse injuries.

GC-MS analysis and screening of antidiabetic, antioxidant and hypolipidemic potential of Cinnamomum tamala oil in streptozotocin induced diabetes mellitus in rats

AIM OF THE STUDY

This study was made to investigate the antidiabetic, antioxidant and hypolipidemic potential of Cinnamomum tamala, (Buch.-Ham.) Nees & Eberm (Tejpat) oil (CTO) in streptozotocin (STZ) induced diabetes in rats along with evaluation of chemical constituents.

MATERIALS AND METHODS

The GC-MS (Gas chromatography-mass spectrometry) analysis of the oil showed 31 constituents of which cinnamaldehyde was found the major component (44.898%). CTO and cinnamaldehyde was orally administered to diabetic rats to study its effect in both acute and chronic antihyperglycemic models. The body weight, oral glucose tolerance test and biochemical parameters viz. glucose level, insulin level, liver glycogen content, glycosylated hemoglobin, total plasma cholesterol, triglyceride and antioxidant parameters were estimated for all treated groups and compared against diabetic control group.

RESULTS

CTO (100 mg/kg and 200 mg/kg), cinnamaldehyde (20 mg/kg) and glibenclamide (0.6 mg/kg) in respective groups of diabetic animals administered for 28 days reduced the blood glucose level in streptozotocin induced diabetic rats. There was significant increase in body weight, liver glycogen content, plasma insulin level and decrease in the blood glucose, glycosylated hemoglobin and total plasma cholesterol in test groups as compared to control group. The results of CTO and cinnamaldehyde were found comparable with standard drug glibenclamide. In vitro antioxidant studies on CTO using various models showed significant antioxidant activity. In vivo antioxidant studies on STZ induced diabetic rats revealed decreased malondialdehyde (MDA) and increased reduced glutathione (GSH).

CONCLUSION

Thus the investigation results that CTO has significant antidiabetic, antioxidant and hypolipidemic activity.

Pyrus biossieriana Buhse leaf extract: An antioxidant, antihyperglycaemic and antihyperlipidemic agent

The antihyperglycaemic, antihyperlipidemic and antioxidant effects of wild pear (Pyrus biossieriana Buhse) leaf extract were investigated. An alloxan-induced rat model of hyperglycaemia was used to evaluate the antihyperglycaemic, antihyperlipidemic and antioxidant properties of the Pyrus biossieriana Buhse leaf extract. The arbutin content of Pyrus biossieriana Buhse leaves, measured by HPLC, was 12.6 dry weight percent. Administration of the Pyrus biossieriana Buhse leaf extract (at doses of 500 and 1000mg/kg/day) significantly reduced the increase in serum glucose concentration seen in alloxan-treated hyperglycaemic rats. Both concentrations of the extract enhanced serum insulin levels compared to the control group. Both high and low doses of the extract decreased serum triacylglycerol (TG) and cholesterol (CHOL) levels as compared to controls. Serum antioxidant levels were significantly higher in rats treated with low (500mg/kg/day) and high (1000mg/kg/day) doses of Pyrus biossieriana Buhse extracts at 24, 48 and 72h after alloxan injection than in control rats. This study demonstrated that Pyrus biossieriana Buhse leaf extract reduces blood glucose and lipid levels and increases antioxidant status in rats with alloxan-induced hyperglycaemia.

Activities of cyclooxygenases, and levels of prostaglandins E2 and F2alpha, in fetopathy associated with experimental diabetic gestation

AIM

The present study investigated the cyclooxygenase (COX) pathway to elucidate any changes that may be involved in the mechanism(s) underlying diabetic fetopathy.

METHODS

Diabetes was induced in female rats (n=12) by two successive daily injections of 55 mg/kg streptozotocin, while control animals (n=10) were injected with a buffer solution; hyperglycaemia was confirmed by blood glucose levels greater than 11 mmol/L. The study female rats were made pregnant and, on day 15 of gestation, the rats were sacrificed, and the fetuses, placentas and membranes dissected out of the uterine horns. Following morphological examination, the fetuses, placentas and membranes were homogenized, and used to measure COX activities and prostaglandin (PG) E(2) and PGF(2alpha) levels.

RESULTS

Fetuses from diabetic mothers exhibited significantly (P<0.05) shorter crown-to-rump lengths, lower body weights and heavier placental weights. The activity of COX-1 in the fetuses, placentas and membranes from diabetic mothers represented a small percentage of total COX activity compared with that of COX-2. The presence of a COX-1 inhibitor in the control and diabetic rats was investigated and found to be negative. The activity of COX-2 in malformed fetuses from diabetic mothers was significantly lower (P<0.05) compared with non-malformed fetuses from control and diabetic mothers. The mean level of PGE(2) in fetuses from diabetic mothers was significantly (P<0.05) lower than that in controls. In contrast, the biggest increases in PGF(2alpha) were observed in the malformed diabetic fetuses, placentas and membranes.

CONCLUSION

The increased production of PGF(2alpha) probably proceeds, at least in part, independently of the COX pathway and via the isoprostane route. However, it is unclear whether the relatively high levels of PGF(2alpha) are causally related to, or simply coincidental with, fetal malformation.

Effect of Indian herbal hypoglycemic agents on antioxidant capacity and trace elements content in diabetic rats

In the present investigation we report the protective potential of some herbal hypoglycemic agents on antioxidant status and levels of metal ions in streptozotocin-induced diabetic rats. Furthermore, in vitro antioxidant activity of the herbs was also evaluated. Induction of diabetes mellitus in rats caused an increase in blood lipid peroxide levels that was associated with the reduced activity of red blood cell (RBC) antioxidant enzymes--namely, superoxide dismutase, catalase, glutathione reductase, and glutathione peroxidase--along with depletion of plasma reduced glutathione (GSH) and copper, zinc, iron, magnesium, and selenium levels. Oral treatment of diabetic rats with Allium sativum, Azadirachta indica, Momordica charantia, and Ocimum sanctum extracts (500 mg/kg of body weight) not only lowered the blood glucose level but also inhibited the formation of lipid peroxides, reactivated the antioxidant enzymes, and restored levels of GSH and metals in the above-mentioned model. The herbal extracts (50-500 microg) inhibited the generation of superoxide anions (O(2)(-.)) in both enzymatic and nonenzymatic in vitro systems. These preparations also inhibited the ferrous-sodium ascorbate-induced formation of lipid peroxides in RBCs. The in vivo and in vitro protective effects of the above-mentioned herbal drugs were also compared with that of glibenclamide. On the basis of our results, we conclude that the above-mentioned herbal plants not only possess hypoglycemic properties, but they also decrease oxidative load in diabetes mellitus. Therefore, we propose that long-term use of such agents might help in the prevention of diabetes-associated complications. However, the extrapolation of these results to humans needs further in-depth study.

Anticlastogenic activity of morin against whole body gamma irradiation in Swiss albino mice

Anticlastogenic activity of morin was explored against whole body gamma radiation, at a dose rate of 1.66 Gy/min in Swiss albino mice pretreated intraperitoneal or orally. Pretreatment with morin 10, 25, 50, 75, 100, 125, and 150 mg/kg, i.p. delayed and reduced percentage mortality and increased mean survival times in mice irradiated with 10 Gy gamma radiation. Intraperitoneal route was found superior to oral route. An i.p. dose of 100 mg/kg was found to be the most effective dose in preventing radiation-induced weight loss, increasing the mean survival times and reducing percentage mortality. Morin (100 mg/kg) pretreatment effectively maintained spleen index (spleen weight/body weight x 100) and stimulated endogenous spleen colony forming units. Pretreatment with morin (100 mg/kg) significantly reduced dead, inflammatory, and mitotic cells in irradiated mice jejunum along with a significant increase in goblet cells and rapidly multiplying crypt cells. Morin (100 mg/kg) also maintained the villus height close to normal, prevented mucosal erosion and basement membrane damage in irradiated jejunum. Nuclear enlargement in epithelial cells of jejunum was lower in morin treated mice compared to radiation control. Morin (100 mg/kg) also significantly elevated the endogenous antioxidant enzymes viz. glutathione S transferase (GST), superoxide dismutase (SOD) and reduced glutathione (GSH), in normal mice at 2, 4 and 8 h post treatment. Drastic decrease in endogenous enzymes (GSH, GST, catalase and SOD) and total thiols was observed in irradiated mice at 2, 4 and 8 h post irradiation, while pretreatment with morin (100 mg/kg) prevented this decrease. Morin (100 mg/kg) also elevated radiation LD(50) from 9.2 to 10.1 Gy, indicating a dose modifying factor (DMF) of 1.11.

Glycogen synthase kinase-3beta inhibits the xenobiotic and antioxidant cell response by direct phosphorylation and nuclear exclusion of the transcription factor Nrf2

The transcription factor Nrf2 (nuclear factor E2-related factor 2) regulates the expression of antioxidant phase II genes and contributes to preserve redox homeostasis and cell viability in response to oxidant insults. Nrf2 should be coordinated with the canonical cell survival pathway represented by phosphatidylinositol 3-kinase (PI3K) and the Ser/Thr kinase Akt but so far the mechanistic connections remain undefined. Here we identify glycogen synthase kinase-3beta (GSK-3beta), which is inhibited by Akt-mediated phosphorylation, as the link between both processes. Using heme oxygenase-1 (HO-1) as a model phase II gene, we found that both PI3K and Akt increased mRNA and protein levels of this enzyme. Pharmacological inhibitors (LiCl and PDZD-8) and genetic variants of GSK-3beta (constitutively active and dominant negative mutants) indicated that PI3K/Akt activates and GSK-3beta inhibits the antioxidant response elements of the ho1 promoter and pointed Nrf2 as directly involved in this process. Indeed, GSK-3beta phosphorylated Nrf2 in vitro and in vivo. Immunocytochemistry and subcellular fractionation analyses demonstrated that the effect of GSK-3beta-mediated phosphorylation of Nrf2 is to exclude this transcription factor from the nucleus. Nrf2 up-regulated the expression of HO-1, glutathione peroxidase, glutathione S-transferase A1, NAD(P)H: quinone oxidoreductase and glutamate-cysteine ligase and protected against hydrogen peroxide-induced glutathione depletion and cell death, whereas co-expression of active GSK-3beta attenuated both phase II gene expression and oxidant protection. These results contribute to clarify the cross-talk between the survival signal elicited by PI3K/Akt and the antioxidant phase II cell response, and introduce GSK-3beta as the key mediator of this regulation mechanism.