Effect of metformin on clastogenic and biochemical changes induced by adriamycin in Swiss albino mice

Metformin alleviates sodium arsenite-induced hepatotoxicity and glucose intolerance in mice by suppressing oxidative stress, inflammation, and apoptosis

BACKGROUND

Epidemiological studies have shown that exposure to sodium arsenite (NaAsO2) causes diabetes and hepatotoxicity. Metformin (MET), an oral hypoglycemic agent, has long been used in diabetes therapy. In addition, MET has been shown to have hepatoprotective effects. In this study, we investigated the effects of MET on NaAsO2-induced hepatotoxicity and glucose intolerance in mice.

METHODS

Mice were divided into four groups: Groups I and II received distilled water and NaAsO2 (10 mg/kg, p.o.) for five weeks, respectively. Groups III and IV were treated with NaAsO2 (10 mg/kg, p.o.) for three weeks, followed by MET (125 and 250 mg/kg, p.o.) for the last two weeks before NaAsO2. A glucose tolerance test was performed on day 35. The serum and tissue parameters were also evaluated.

RESULTS

Histopathological examination revealed NaAsO2-induced liver and pancreatic damage. NaAsO2 caused hyperglycemia, glucose intolerance, and a significant increase in liver function enzymes. Administration of NaAsO2 significantly reduced hepatic superoxide dismutase, catalase, glutathione peroxidase, and total thiol levels and increased the content of reactive thiobarbituric acid substances. In addition, it led to an increase in liver nitric oxide levels and protein expression of tumor necrosis factor-α, nuclear factor kappa B, and cysteine-aspartic proteases-3. In contrast, treatment with MET (250 mg/kg) significantly improved NaAsO2-induced biochemical and histopathological changes.

CONCLUSION

Our findings suggest that the significant effects of MET against NaAsO2-induced hepatotoxicity and glucose intolerance may be exerted via the regulation of oxidative stress, followed by suppression of inflammation and apoptosis.

High-dose metformin induces a low-glucose dependent genotoxic stress

Epidemiological studies have demonstrated that metformin (a cornerstone of diabetes treatment) has anticancer activity, but the underlying mechanism remains elusive. We aimed to investigate whether metformin elicits anticancer activity via increasing genotoxic stress, a state of increased genome damage that becomes tumor-suppressing if it goes beyond an intolerable threshold. We found that metformin (1-16 mM) suppressed proliferation and colony formation in a panel of cancer cell lines (HeLa, A375, A549 and QGY). Metformin induced a dose-dependent increase of genotoxic stress (including micronucleus, nucleoplasmic bridge and nuclear bud) and the increase of genotoxic stress correlated well with metformin's anticancer potential. Metformin deregulated the expression of BUBR1 and MAD2, two core genes of spindle assembly checkpoint (SAC) that surveillances chromosome segregation. Metformin had weakened antiproliferative effect and a corresponding attenuated genotoxic effect in HeLa cells cultured in high glucose (16 mg/ml). Meanwhile, metformin significantly increased genotoxicity in non-cancer cells (NCM460 and HUVECs). Metformin became non-genotoxic to HUVECs in high-glucose (8 and 16 mg/ml) conditions and reduced the genotoxicity of high glucose. Overall, these results infer a new mechanism of high-dose metformin, whereby low-glucose dependent genotoxic stress derived from SAC dysfunction might mediate some of the anticancer effect of this drug.

The Chemosensitizing Role of Metformin in Anti-Cancer Therapy

Chemoresistance, which leads to the failure of chemotherapy and further tumor recurrence, presents the largest hurdle for the success of anti-cancer therapy. In recent years, metformin, a widely used first-line antidiabetic drug, has attracted increasing attention for its anti-cancer effects. A growing body of evidence indicates that metformin can sensitize tumor responses to different chemotherapeutic drugs, such as hormone modulating drugs, anti-metabolite drugs, antibiotics, and DNA-damaging drugs via selective targeting of Cancer Stem Cells (CSCs), improving the hypoxic microenvironment, and by suppressing tumor metastasis and inflammation. In addition, metformin may regulate metabolic programming, induce apoptosis, reverse Epithelial to Mesenchymal Transition (EMT), and Multidrug Resistance (MDR). In this review, we summarize the chemosensitization effects of metformin and focus primarily on its molecular mechanisms in enhancing the sensitivity of multiple chemotherapeutic drugs, through targeting of mTOR, ERK/P70S6K, NF-κB/HIF-1 α, and Mitogen- Activated Protein Kinase (MAPK) signaling pathways, as well as by down-regulating the expression of CSC genes and Pyruvate Kinase isoenzyme M2 (PKM2). Through a comprehensive understanding of the molecular mechanisms of chemosensitization provided in this review, the rationale for the use of metformin in clinical combination medications can be more systematically and thoroughly explored for wider adoption against numerous cancer types.>.

Cytogenetic effects of antidiabetic drug metformin

Metformin (MET) is the first-choice antidiabetic drug for type 2 diabetes mellitus treatment. In this study, the genotoxic potential of MET was evaluated by using chromosome aberrations (CAs), sister chromatid exchanges (SCEs), and micronucleus (MN) assays in human peripheral lymphocytes as well as comet assay in isolated lymphocytes. Human lymphocytes were treated with different concentrations of MET (12.5, 25, 50, 75, 100, and 125 µg/mL) for 24 h and 48 h. A negative and a positive control (Mitomycin-C-MMC, 0.20 μg/mL, for CA, SCE, and MN tests; hydrogen peroxide-H₂O₂, 100 µM, for comet assay) were also maintained. MET significantly increased the frequency of CAs at 48 h exposure (except 12.5 µg/mL) compared to the negative control. MET increased SCEs/cells in both treatment periods (except 12.5 µg/mL at 24 h). MET only increased the frequency of MN at 125 µg/mL. While MET significantly increased the comet tail length (CTL) at four concentrations (25, 75, 100, and 125 µg/mL), it did not affect comet tail intensity (CTI) (except 125 µg/mL) and comet tail moment (CTM) at all the treatments. All these data showed that MET had a mild genotoxic effect, especially at a long treatment period and higher concentrations in human lymphocytes in vitro. However, further in vitro and especially in vivo studies should be conducted to understand the detailed genotoxic potential of MET.HighlightsMetformin increased the frequency of CAs and SCEs, especially at 48-h exposure time in human lymphocytes.This antidiabetic drug increased the frequency of MN only at the highest concentration tested (125 µg/mL).Metformin significantly increased the comet tail length in all treatments (except 50 µg/mL).The drug did not significantly affect the comet tail intensity (except 125 µg/mL) and comet tail moment in all treatments.

Research progress on sirtuins family members and cell senescence

Human aging is a phenomenon of gradual decline and loss of cell, tissue, organ and other functions under the action of external environment and internal factors. It is mainly related to genomic instability, telomere wear, mitochondrial dysfunction, protein balance disorder, antioxidant damage, microRNA expression disorder and so on. Sirtuins protein is a kind of deacetylase which can regulate cell metabolism and participate in a variety of cell physiological functions. It has been found that sirtuins family can prolong the lifespan of yeast. Sirtuins can inhibit human aging through many signaling pathways, including apoptosis signaling pathway, mTOR signaling pathway, sirtuins signaling pathway, AMPK signaling pathway, phosphatidylinositol 3 kinase (PI3K) signaling pathway and so on. Based on this, this paper reviews the action principle of anti-aging star members of sirtuins family Sirt1, Sirt3 and Sirt6 on anti-aging related signaling pathways and typical compounds, in order to provide ideas for the screening of anti-aging compounds of sirtuins family members.

Metformin as a protective agent against natural or chemical toxicities: a comprehensive review on drug repositioning

BACKGROUND

Metformin is the first prescribed drug for hyperglycemia in type 2 diabetes mellitus. Mainly by activating AMPK pathway, this drug exerts various functions that among them protective effects are of the interest.

PURPOSE

Herein, we aimed to gather data about the protective impacts of metformin against various natural or chemical toxicities.

RESULTS

An extensive search among PubMed, Scopus, and Google Scholar was conducted by keywords related to protection, toxicity, natural and chemical toxins and, metformin. Our literature review showed metformin alongside its anti-hyperglycemic effect has a wide range of anti-toxic effects against anti-tumour and routine drugs, natural and chemical toxins, herbicides and, heavy metals.

CONCLUSION

It is evident that metformin is a potent drug against the toxicity of a broad spectrum of natural, chemical toxic agents which is proved by a vast number of studies. Metformin mainly through AMPK axis can protect different organs against toxicities. Moreover, metformin preserves DNA integrity and can be an option for adjuvant therapy to ameliorate side effect of other therapeutics.

Metformin attenuates cisplatin-induced genotoxicity and apoptosis in rat bone marrow cells

Metformin is widely used as an oral hypoglycemic drug in the management of type 2 diabetes mellitus. This study evaluated the possible protective effects of metformin against cisplatin-induced genotoxicity and apoptosis in rat bone marrow cells. Two different doses of metformin (50 and 100 mg/kg b.w.) were administered orally to experimental animals for seven consecutive days. On the seventh day, the rats were exposed to cisplatin (5 mg/kg, i.p.) 1 h after the last oral metformin administration. Rats in the control group were treated orally with 10 ml/kg PBS for 7 consecutive days and a single intraperitoneal injection of saline (0.9%) on the 7th day. The antagonistic effects of metformin against cisplatin were evaluated using micronucleus assay, reactive oxygen species (ROS) level analysis, hematological analysis, and flow cytometry. Treatment with 50 and 100 mg/kg metformin before cisplatin injection produced a significant reduction in the frequencies of micronucleated polychromatic erythrocytes (MnPCEs) and micronucleated normochromatic erythrocytes (MnNCEs) 24 h after cisplatin treatment with a corresponding increase in the PCE/(PCE + NCE) ratio. Moreover, metformin markedly elevated the levels of both red and white blood cells in peripheral blood and decreased the percentage of apoptotic cells and the ROS level in bone marrow cells of rats treated with cisplatin. The data suggest that metformin has potential chemoprotective properties in rat bone marrow after cisplatin treatment, which support its candidature as a potential chemoprotective agent for cancer patients undergoing chemotherapy.

Metformin: Prevention of genomic instability and cancer: A review

The diabetes drug metformin can mitigate the genotoxic effects of cytotoxic agents and has been proposed to prevent or even cure certain cancers. Metformin reduces DNA damage by mechanisms that are only incompletely understood. Metformin scavenges free radicals, including reactive oxygen species and nitric oxide, which are produced by genotoxicants such as ionizing or non-ionizing radiation, heavy metals, and chemotherapeutic agents. The drug may also increase the activities of antioxidant enzymes and inhibit NADPH oxidase, cyclooxygenase-2, and inducible nitric oxide synthase, thereby limiting macrophage recruitment and inflammatory responses. Metformin stimulates the DNA damage response (DDR) in the homologous end-joining, homologous recombination, and nucleotide excision repair pathways. This review focuses on the protective properties of metformin against genomic instability.

Magnesium isoglycyrrhizinate ameliorates doxorubicin-induced acute cardiac and hepatic toxicity via anti-oxidant and anti-apoptotic mechanisms in mice

The present study investigated the effects and potential mechanisms of action of magnesium isoglycyrrhizinate (MgIG) in doxorubicin (DOX)-treated mice. Histopathological analysis and western blot analysis were conducted in the liver and heart tissues and biochemical analysis of the serum was performed. The results revealed that MgIG (10, 20 and 40 mg/kg/day) could protect the structure and functions of the liver and heart by inhibiting the activities of the myocardial enzymes creatine kinase (CK), CK-MB and lactate dehydrogenase and the hepatic-specific enzymes aspirate aminotransferase and alanine aminotransferase, increasing the activities of the antioxidants superoxide dismutase and glutathione peroxidase, and inhibiting cellular apoptosis induced by DOX (30 mg/kg). These results demonstrate that inhibiting lipid peroxidation and reducing myocardial and hepatocyte apoptosis may be one of the mechanisms by which MgIG exhibits hepatoprotective and cardioprotective effects in DOX-treated mice.

The radioprotective effect of metformin against cytotoxicity and genotoxicity induced by ionizing radiation in cultured human blood lymphocytes

Metformin is a widely prescribed drug used in the treatment of patients with type 2 diabetes. In this study, the radioprotective effect of metformin was investigated against cytotoxicity and genotoxicity induced by ionizing radiation (IR) in human peripheral blood lymphocytes. Human lymphocytes were treated with metformin at concentrations 10 and 50μM for 2h and irradiated with 6MV X-rays. The radiation antagonistic potential of metformin was assessed by MTT [3-(4,5-dimethyl-2-thiaozolyl)-2,5-diphenyl-2H tetrazolium bromide] assay, chromosomal aberration (CA) analysis, cytokinesis blocked micronucleus (CBMN) assay, and flow cytometry. Observations demonstrated a radiation-dose-dependent decrease in the percentage of cell viability after 24h. It was found that pretreatment with metformin (10 and 50μM) increased the percentage of cell viability. A highly significant dose modifying factor (DMF) 1.35 and 1.42 was observed for 10 and 50μM metformin, respectively. Metformin (10 and 50μM) pretreatment significantly decreased the frequency of dicentrics (DCs), acentric fragments (AFs), rings (RIs), micronuclei (MN), and nucleoplasmic bridges (NPBs) in irradiated human peripheral blood lymphocytes. Also, treatment with metformin (10 and 50μM) without irradiation did not increase the number of MN, NPBs, DCs, AFs, RIs, and did not show a cytostatic effect in the human peripheral blood lymphocytes. On the other hand, metformin treatment (10 and 50μM) 2h prior to irradiation significantly reduced X-radiation-induced apoptotic incidence in human lymphocytes. The present study demonstrates metformin to be an effective radioprotector against DNA damage and apoptosis induced by IR in human lymphocytes. These data have an important application for the protection of lymphocytes from the genetic damage and side-effects induced by radiotherapy in cancer patients.

Finding New Tricks for Old Drugs: Tumoricidal Activity of Non-Traditional Antitumor Drugs

Chemotherapy, a traditional method, plays an important role in tumor therapy. Currently, common clinical antitumor drugs have several defects like poor efficacy, side effects, etc. Furthermore, developing new antitumor drugs takes a long time and requires many resources. Recent studies have found that oldies are newbies for the oncologist, such as flavonoid, metformin, aspirin, etc. These non-traditional antitumor drugs (NTADs) are widely used in management of non-cancer diseases, which gained FDA approval for treatment of patients. Increasingly, studies about antitumor action of NTADs have attracted many researchers' interests. A giant amount of studies showed a decrease in cancer incidence in NTAD-treated patients. Several reports outlined a direct inhibitory effect of NTADs on cancer cell growth and antitumoral actions. This review summarized the research progress on antitumor effects of ten NTADs. Retrospective and meta-analyses of trials also showed that these NTADs had preventive effects against cancer in vitro and in vivo. These drugs represent a promising option for cancer treatment, which have clear benefits including clinical safety, obvious curative effect, and saving medical and health resources. Judged from previous reports, future studies will yield valuable data about the profitable effects of these drugs. With a better understanding of its mechanisms of antitumor activity, NTADs may become available for combination with chemotherapy or targeted therapy in clinic.

Effect of Metformin and Sitagliptin on Doxorubicin-Induced Cardiotoxicity in Rats: Impact of Oxidative Stress, Inflammation, and Apoptosis

Doxorubicin (DOX) is a widely used antineoplastic drug whose efficacy is limited by its cardiotoxicity. The aim of this study was to investigate the possible protective role of the antidiabetic drugs metformin (250 mg/kg dissolved in DW p.o. for seven days) and sitagliptin (10 mg/kg dissolved in DW p.o. for seven days) in a model of DOX-induced (single dose 15 mg/kg i.p. at the fifth day) cardiotoxicity in rats. Results of our study revealed that pretreatment with metformin or sitagliptin produced significant (P < 0.05) cardiac protection manifested by a significant decrease in serum levels of LDH and CK-MB enzymes and cardiac MDA and total nitrites and nitrates levels, a significant increase in cardiac SOD activity, and remarkable improvement in the histopathological features as well as a significant reduction in the immunohistochemical expression of COX-2, iNOS, and caspase-3 enzymes as compared to DOX group. These results may suggest using metformin and/or sitagliptin as preferable drugs for diabetic patients suffering from cancer and receiving DOX in their chemotherapy regimen.

Acute Treatment of Resveratrol Alleviates Doxorubicin-Induced Myotoxicity in Aged Skeletal Muscle Through SIRT1-Dependent Mechanisms

Study of the exacerbating effects of chemotherapeutics, such as doxorubicin, on the impairment of insulin metabolic signaling in aged skeletal muscle is very limited. Here, we tested the hypothesis that activation of sirtuin 1 deacetylase activity by resveratrol would prevent the disruption of insulin signaling and augmentation of catabolic markers induced by doxorubicin in aged skeletal muscle. Two- and 10-month-old senescence-accelerated mice (prone 8) were randomized to receive saline, doxorubicin, doxorubicin and resveratrol, or a combination of doxorubicin, resveratrol, and sirtinol or EX527. Doxorubicin reduced the sirtuin 1 activity without affecting the phosphorylation levels of IRS1(Ser307), mTOR(Ser2481), Akt(Thr308/Ser473), membranous glucose transporter 4, protein abundance of PDK4, and enzymatic activity of pyruvate dehydrogenase in aged muscles. Intriguingly, resveratrol attenuated the doxorubicin-induced elevations of apoptotic and catabolic markers measured as Bax, caspase 3 activity, apoptotic DNA fragmentation, MuRF-1, ubiquitinated proteins, and proteasomal activity in aged muscles, whereas these beneficial effects were abolished on inhibition of sirtuin 1 by sirtinol or EX527. Markers of insulin signaling were not affected by doxorubicin or resveratrol in the senescent skeletal muscle. Nevertheless, the antiapoptotic and anticatabolic effects of resveratrol in aged skeletal muscle treated with doxorubicin were mediated in a sirtuin 1-dependent signaling manner.

Anticancer efficacy and absorption, distribution, metabolism, and toxicity studies of aspergiolide A in early drug development

Since the first anthracycline was discovered, many other related compounds have been studied in order to overcome its defects and improve efficacy. In the present paper, we investigated the anticancer effects of a new anthracycline, aspergiolide A (ASP-A), from a marine-derived fungus in vitro and in vivo, and we evaluated the absorption, distribution, metabolism, and toxicity drug properties in early drug development. We found that ASP-A had activity against topoisomerase II that was comparable to adriamycin. ASP-A decreased the growth of various human cancer cells in vitro and induced apoptosis in BEL-7402 cells via a caspase-dependent pathway. The anticancer efficacy of ASP-A on the growth of hepatocellular carcinoma xenografts was further assessed in vivo. Results showed that, compared with the vehicle group, ASP-A exhibited significant anticancer activity with less loss of body weight. A pharmacokinetics and tissue distribution study revealed that ASP-A was rapidly cleared in a first order reaction kinetics manner, and was enriched in cancer tissue. The maximal tolerable dose (MTD) of ASP-A was more than 400 mg/kg, and ASP-A was not considered to be potentially genotoxic or cardiotoxic, as no significant increase of micronucleus rates or inhibition of the hERG channel was seen. Finally, an uptake and transport assay of ASP-A was performed in monolayers of Caco-2 cells, and ASP-A was shown to be absorbed through the active transport pathway. Altogether, these results indicate that ASP-A has anticancer activity targeting topoisomerase II, with a similar structure and mechanism to adriamycin, but with much lower toxicity. Nonetheless, further molecular structure optimization is necessary.

The key role of growth hormone-insulin-IGF-1 signaling in aging and cancer

Studies in mammals have led to the suggestion that hyperglycemia and hyperinsulinemia are important factors in aging. GH/Insulin/insulin-like growth factor-1 (IGF-1) signaling molecules that have been linked to longevity include daf-2 and InR and their homologues in mammals, and inactivation of the corresponding genes increases lifespan in nematodes, fruit flies and mice. The life-prolonging effects of caloric restriction are likely related to decreasing IGF-1 levels. Evidence has emerged that antidiabetic drugs are promising candidates for both lifespan extension and prevention of cancer. Thus, antidiabetic drugs postpone spontaneous carcinogenesis in mice and rats, as well as chemical and radiation carcinogenesis in mice, rats and hamsters. Furthermore, metformin seems to decrease the risk for cancer in diabetic patients.

Metformin's performance in in vitro and in vivo genetic toxicology studies

Metformin is a hypoglycemiant drug prescribed for the treatment and control of the type 2 diabetes mellitus. Recently, the potential efficacy of this antidiabetic drug as an anticancer agent has been demonstrated in various mammalian cancer cells. This report evaluates the mutagenic as well as the recombinogenic potentials of the metformin drug in therapeutically relevant plasma concentrations (12.5 µM, 25.0 µM or 50.0 µM). Since the loss of heterozygosity is a process associated with carcinogenesis, the recombinogenic potential of such a drug was evaluated by the homozygotization assay using a heterozygous diploid strain of Aspergillus nidulans. The homozigotization indices (HI) for the genetic markers from the metformin-treated diploids were not statistically different from the negative control (non-treated diploids). For the first time, this indicated a lack of recombinogenic activity of the antidiabetic drug. The mutagenic potential of the metformin drug was evaluated by the chromosome aberrations and the micronuclei tests in human lymphocytes cultures. The metformin drug did not show any significant increase either in the numerical or in the structural chromosome aberrations and did not affect significantly the mitotic index when compared to the negative control. In the in vitro micronucleus test, the drug did not increase the number of micronuclei or nuclear buds when compared with the negative control. The data in this study suggest that the metformin drug is not a secondary cancer inducer, since it has neither showed recombinogenic nor mutagenic activities when used in pharmacological concentrations.

Metformin rescues the myocardium from doxorubicin-induced energy starvation and mitochondrial damage in rats

Clinical use of doxorubicin (DOX) is limited by its cardiotoxic side effects. Recent studies established that metformin (MET), an oral antidiabetic drug, possesses an antioxidant activity. However, whether it can protect against DOX-induced energy starvation and mitochondrial damage has not been reported. Our results, in a rat model of DOX-induced cardiotoxicity, show that DOX treatment significantly increased serum levels of LDH and CK-MB, indicators of cardiac injury, and induced expression of hypertrophic gene markers. DOX also caused marked decreases in the cardiac levels of glutathione, CoA-SH and ATP, and mRNA expression of catalase and NQO-1. These biochemical changes were associated with myocardial histopathological and ultrastructural deteriorations, as observed by light and electron microscopy, respectively. Cotreatment with MET (500 mg/kg) eliminated all DOX-induced biochemical, histopathological, and ultrastructural changes. These findings demonstrate that MET successfully prevents DOX-induced cardiotoxicity in vivo by inhibiting DOX-induced oxidative stress, energy starvation, and depletion of intramitochondrial CoA-SH.

Metformin as an antitumor agent in cancer prevention and treatment

Recent epidemiological investigations conducted in diabetic cohorts and cancer patients have found that metformin users have lower risks for cancer than those using insulin or insulin secretagogues. Studies conducted in various animal tumor models and cancer cell lines have demonstrated that metformin prevents tumor development or inhibits cell proliferation. In addition, a recent clinical trial has shown that short-term use of metformin reduces aberrant crypt foci (ACF) formation in non-diabetic patients with ACF. The antitumor activity of metformin may be mediated through its regulatory effect on hormonal, metabolic, and immune functions. Metformin achieves glycemic control by reducing hepatic glucose production and increasing the muscle intake of glucose, thus lowering levels of circulating glucose and, consequently, insulin. The major molecular targets of metformin are the liver kinase B1 (LKB1)-AMP-activated protein kinase (AMPK) signaling and mammalian target of rapamycin (mTOR) pathways, which are central in the regulation of cellular energy homeostasis and play a crucial role in the control of cell division and cell proliferation. Metformin has been shown to improve endothelial function, decrease inflammatory activity, and regulate immune function. Increasing experimental evidence provides a strong biological rationale for metformin as an antitumor and chemopreventive agent. Metformin is being tested as an adjuvant cancer therapy in clinical settings, and metformin is recommended for all cases of Type 2 diabetes without contraindications. As described in this review, the chemopreventive value of metformin is not restricted to diabetic or obese individuals.

Protective role of glibenclamide against nicotinamide-streptozotocin induced nuclear damage in diabetic Wistar rats

Objective:

To evaluate the protective effect of glibenclamide against the experimental diabetes-induced nuclear damage in Wistar rats.

Materials and Methods:

The anti-mutagenic effect of glibenclamide (0.5, 5 and 50 mg/kg, p.o daily for 4 weeks) was evaluated against the nicotinamide (NA)-streptozotocin (STZ) induced type-2 diabetes mellitus using bone marrow micronucleus and sperm abnormalities tests. The antioxidant status was tested by estimating the serum levels of lipid peroxidation (LPO), catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GPx).

Results:

The results indicated that glibenclamide at 50 mg/kg decreased the frequency of micronuclei in erythrocytes (P < 0.05) and sperm shape abnormality (P < 0.01) besides enhancing the antioxidant status (P < 0.05) in the diabetic rats. However, glibenclamide treatment did not enhance the polychromatic and normochromatic erythrocytes (P/N) ratio and sperm count in the diabetic condition.

Conclusion:

The observations indicate that the glibenclamide has anti-mutagenic potential which could be related to the antioxidant effect and might also possess anti-proliferative property.

Metformin for aging and cancer prevention

Studies in mammals have led to the suggestion that hyperglycemia and hyperinsulinemia are important factors in aging. Insulin/insulin-like growth factor 1 (IGF-1) signaling molecules that have been linked to longevity include daf-2 and InR and their homologues in mammals, and inactivation of the corresponding genes increases life span in nematodes, fruit flies and mice. It is possible that the life-prolonging effect of caloric restriction is due to decreasing IGF-1 levels. Evidence has emerged that antidiabetic drugs are promising candidates for both life span extension and prevention of cancer. Thus, antidiabetic drugs postpone spontaneous carcinogenesis in mice and rats, as well as chemical and radiation carcinogenesis in mice, rats and hamsters. Furthermore metformin seems to decrease cancer risk in diabetic patients.

Activation of P53 in HepG2 cells as surrogate to detect mutagens and promutagens in vitro

The current genotoxicity tests of the standard in vitro battery, especially those using mammalian cells, are limited by their low specificity and highlight the importance of new in vitro tools. This study aimed to evaluate the suitability of HepG2 cells for assaying mutagens and promutagens. We determined P53 activity as surrogate genotoxicity endpoint in HepG2 cells. Our results revealed a significant P53-induction by actinomycin D, methyl methanesulfonate and etoposide. Prior to the investigation of promutagens we characterized HepG2 cells by analyzing the expression of 45 genes involved in xenobiotic metabolism and measuring the activity of selected Cytochrome-P450 (CYP) enzymes. We determined a limited metabolic capacity prompting us to employ a co-treatment with rat liver S9 as metabolic activation system (MAS) for promutagens. While cyclophosphamide showed an elevation of activated P53 in the presence of S9, 7,12-dimethylbenz[a]anthracene and aflatoxin B(1) responded without the MAS. Inhibition of cellular CYP3A4 or CYP1A/1B suppressed the aflatoxin B(1)- and dimethylbenz[a]anthracene-mediated P53 response, respectively, indicating that HepG2 cells are capable of metabolizing these compounds in a CYP1A/B/3A4-dependent manner. In summary, our results indicate that P53 activation in HepG2 cells combined with a MAS can be used for the identification of new (pro)genotoxicants.

Metformin regresses endometriotic implants in rats by improving implant levels of superoxide dismutase, vascular endothelial growth factor, tissue inhibitor of metalloproteinase-2, and matrix metalloproteinase-9

OBJECTIVE

We sought to test if metformin could regress endometriotic explants in rats.

STUDY DESIGN

After inducing endometriotic implants and randomization of female Wistar albino rats, they were given 25 and 50 mg/kg/day of oral metformin in group A (n = 9) and B (n = 8), respectively, for 28 days. Group C (n = 9) was given saline as placebo.

RESULTS

Mean volume, weight, and histologic score of implants in groups A (P < .01, P < .05, and P < .05, respectively) and B (P < .01, P < .05, and P < .05, respectively) were significantly lower than in group C. The activity of superoxide dismutase and tissue inhibitor of metalloproteinase-2 staining in groups A (P < .05 and P < .01, respectively) and B (P < .01 and P < .01, respectively) was significantly higher than in the control group. Moreover, there were more significant reductions in implant levels of vascular endothelial growth factor and matrix metalloproteinase-9 in groups A (both P < .001) and B (both P < .001) than in group C.

CONCLUSION

Metformin causes regression of endometriotic implants in rats.

Evaluation of the genotoxic and cytotoxic effects of crude extracts of Cordia ecalyculata and Echinodorus grandiflorus

ETHNOPHARMACOLOGICAL RELEVANCE

Cordia ecalyculata Vell. and Echinodorus grandiflorus (Cham. & Schltdl.) Micheli are extensively used in Brazil as therapeutic preparations for indigenous groups and the general population. These plants have been used in the folk medicine as: tonic, diuretic, anti-inflammatory, appetite suppressants, for the treatment of snake bites, and weight loss.

AIM OF THE STUDY

In this study, it was verified the possible cytotoxic and genotoxic effects of the crude extracts of. Cordia ecalyculata and Echinodorus grandiflorus, as well as their effectiveness in treating obesity.

MATERIALS AND METHODS

The Micronucleus Test was used for the evaluation of possible clastogenic and aneugenic effects, and the Comet Assay was used for the evaluation of single-strand and double-strand DNA breaks. The cytotoxic effects of the crude extracts were verified by PCE/NCE ratio. Swiss mice (Mus musculus) were used as the experimental model.

RESULTS

It was observed a significant (P<0.05) increase, dose-independent, in the average frequency of micronucleated erythrocytes in peripheral blood in mice treated with either the Cordia ecalyculata or Echinodorus grandiflorus extracts, in comparison with the negative control. There were no significant differences (P>0.05) in the frequency of micronucleated polychromatic erythrocytes for both extract treatment. We observed that treatment with the Cordia ecalyculata extract at concentrations of 1000 and 2000 mg/kg bw resulted in a PCE/NCE ratio that was larger (P<0.05) than the negative control. After 15 days of daily treatment, a dose of 2000 mg/kg bw of either phytotherapeutic did not reduce body mass gain or the amount of food consumed by Swiss mice when compared with the negative control (P>0.05).

CONCLUSION

The results of this study allowed us to infer that the crude extracts of Cordia ecalyculata and Echinodorus grandiflorus do not display cytotoxic or genotoxic activities. However, they do possess weak clastogenic activity (without significance) on peripheral blood cells. Contrary to commonly held beliefs it was also found in this study that the extracts are not effective for obesity treatments.

An evaluation of the genotoxic and cytotoxic effects of the anti-obesity drugs sibutramine and fenproporex

Anti-obesity medications deserve special considerations at the present time due to an increasing number of overweight and obese people who require these therapeutic alternatives. Obesity is positively associated with several chronic illnesses, including cancer. In this work, we evaluated the possible genotoxic and/or cytotoxic actions of two drugs, sibutramine and fenproporex, in the doses of 10, 20 and 40 mg/kg body weight (bw), administered intraperitoneally in male Swiss mice. The genotoxic effect was analyzed by comet assay and micronucleus test. We found that both drugs increased the frequency of genotoxic damage in Swiss mice, but did not present cytotoxic activities towards the polychromatic erythrocytes of the bone marrow of these animals.

Gastroprotective effects of the insulin sensitizers rosiglitazone and metformin against indomethacin-induced gastric ulcers in Type 2 diabetic rats

1. Gastric ulcers are common in Type 2 diabetic patients. Of all drugs used in the treatment of Type 2 diabetes, the insulin sensitizers thiazolidinediones (e.g. rosiglitazone) and metformin exhibit additional effects in ameliorating oxidative stress and inflammation, rendering them attractive candidates for the prevention of gastric ulcer in Type 2 diabetes. Thus, the aim of the present study was to evaluate the gastroprotective effects of rosiglitazone and metformin against indomethacin-induced gastric ulcer in Type 2 diabetic and non-diabetic rats. 2. Diabetes was induced by a single injection of streptozotocin (60 mg/kg, i.p., dissolved in 0.1 mol/L cold citrate buffer, pH 4.5), 15 min after administration of 120 mg/kg, i.p., nicotinamide. Three weeks after the successful induction of diabetes, rats were subjected to pyloric ligation and then injected immediately with 30 mg/kg, i.p., indomethacin. Three hours after indomethacin administration, rats were killed and gastric injury was evaluated. Ranitidine (50 mg/kg) was used as a reference drug and was administered in a single oral dose 1 h before indomethacin injection, as were rosiglitazone (3 mg/kg) and metformin (500 mg/kg). 3. Both rosiglitazone and metformin exhibited gastroprotective effects, as evidenced by significant decreases in the ulcer index, free and total acid output in gastric juice and gastric mucosal malondialdehyde concentrations, with concomitant increases in gastric juice pH (only with rosiglitazone), mucin concentrations, gastric mucosal concentrations of nitric oxide and catalase activity compared with untreated diabetic rats. Conversely, rosiglitazone and metformin had no effect on peptic activity and gastric mucosal prostaglandin E(2) content, particularly in the diabetic group, compared with the untreated groups. 4. In conclusion, rosiglitazone and metformin protect Type 2 diabetic rats against indomethacin-induced gastric ulceration, most possibly via antisecretory actions, enhanced mucosal protection and anti-oxidant activity. Rosiglitazone seems to be provide superior gastroprotection to metformin.

Assessment of genomic instability in normal and diabetic rats treated with metformin

To examine if a single or multiple oral administration of metformin, a member of the biguanide class of anti-diabetic agents, has any genotoxic and cytotoxic potential in normal and diabetic rats, a mammalian model, cytogenetic assays through several endpoints such as induction of micronuclei, chromosome aberrations, mitotic activity of bone marrow cells, sperm-head anomaly and assays of some oxidative stress markers have been conducted by the use of standard techniques. Diabetes was induced by streptozotocin injection. Metformin was administrated to both diabetic and non-diabetic rats in single doses of 100, 500 or 2500 mg/kg along with vehicle control groups for diabetic and non-diabetic rats. The animals were killed by cervical dislocation at 24h after treatment, and then bone marrow cells were sampled. Also, a multiple dose study has done in which diabetic and non-diabetic animals were treated with 100 or 500 mg/kg of metformin daily for 4 or 8 weeks after which the animals were killed by cervical dislocation, and then bone marrow and sperm cells were collected. Concurrent control groups were also included in each experiment. The obtained results revealed that metformin was neither genotoxic nor cytotoxic for the rats in all groups at all tested doses. Moreover, metformin significantly reduced the diabetes-induced genomic instability and cell proliferation changes in somatic and germinal cells in a dose-dependent manner (2500, 500, >100mg/kg). In addition, diabetes induced marked biochemical alterations characteristic of oxidative stress including, enhanced lipid peroxidation and reduction in the reduced glutathione level. Treatment with metformin ameliorated these biochemical markers. In conclusion, metformin is a non-genotoxic or cytotoxic compound and may protect from genomic instability induced by hyperglycemia. Apart from its well-known anti-diabetic effect, the antigenotoxic effect of metformin could be possibly ascribed to its radical scavenger effect that modulated the genomic instability responses and cell proliferation changes induced by hyperglycemia.