Metformin suppresses interleukin (IL)-1beta-induced IL-8 production, aromatase activation, and proliferation of endometriotic stromal cells

Endometrial progesterone resistance and PCOS

Polycystic ovary syndrome (PCOS) is a state of altered steroid hormone production and activity. Chronic estrogen exposure or lack of progesterone due to ovarian dysfunction can result in endometrial hyperplasia and carcinoma. A key contributor to our understanding of progesterone as a critical regulator for normal uterine function has been the elucidation of progesterone receptor (PR) expression, regulation, and signaling pathways. Several human studies indicate that PR-mediated signaling pathways in the nucleus are associated with progesterone resistance in women with PCOS. The aim of this review is to provide an overview of endometrial progesterone resistance in women with PCOS; to present the PR structure, its different isoforms, and their expression in the endometrium; to illustrate the possible regulation of PR and PR-mediated signaling in progesterone resistance in women with PCOS; and to discuss current clinical treatments for atypical endometrial hyperplasia and endometrial carcinoma in women with PCOS and accompanying progesterone resistance.

Diabetes in relation to breast cancer relapse and all-cause mortality in elderly breast cancer patients: a FOCUS study analysis

BACKGROUND

In developed countries, 40% of breast cancer patients are >65 years of age at diagnosis, of whom 16% additionally suffer from diabetes. The aim of this study was to assess the impact of diabetes on relapse-free period (RFP) and overall mortality in elderly breast cancer patients.

PATIENTS AND METHODS

Patients were selected from the retrospective FOCUS cohort, which contains detailed information of elderly breast cancer patients. RFP was calculated using Fine and Gray competing risk regression models for patients with diabetes versus patients without diabetes. Overall survival was calculated by Cox regression models, in which patients were divided into four groups: no comorbidity, diabetes only, diabetes and other comorbidity or other comorbidity without diabetes.

RESULTS

Overall, 3124 patients with non-metastasized breast cancer were included. RFP was better for patients with diabetes compared with patients without diabetes (multivariable HR 0.77, 95% CI 0.59-1.01), irrespective of other comorbidity and most evident in patients aged ≥75 years (HR 0.67, 95% CI 0.45-0.98). The overall survival was similar for patients with diabetes only compared with patients without comorbidity (HR 0.86, 95% CI 0.45-0.98), while patients with diabetes and additional comorbidity had the worst overall survival (HR 1.70, 95% CI 1.44-2.01).

CONCLUSION

When taking competing mortality into account, RFP was better in elderly breast cancer patients with diabetes compared with patients without diabetes. Moreover, patients with diabetes without other comorbidity had a similar overall survival as patients without any comorbidity. Possibly, unfavourable effects of (complications of) diabetes on overall survival are counterbalanced by beneficial effects of metformin on the occurrence of breast cancer recurrences.

Repositioning metformin for cancer prevention and treatment

Metformin is the most commonly prescribed drug for type 2 diabetes (T2DM). Retrospective studies show that metformin is associated with decreased cancer risk. This historical correlation has driven vigorous research campaigns to determine the anticancer mechanisms of metformin. Consolidating the preclinical data is a challenge because unanswered questions remain concerning relevant mechanisms, bioavailability, and genetic factors that confer metformin sensitivity. Perhaps the most important unanswered question is whether metformin has activity against cancer in non-diabetics. In this review we highlight the proposed mechanisms of metformin action in cancer and discuss ongoing clinical trials with metformin in cancer. Improved understanding of these issues will increase the chances for successful application of metformin as an inexpensive, well-tolerated, and effective anticancer agent.

Mesenchymal stem/progenitors and other endometrial cell types from women with polycystic ovary syndrome (PCOS) display inflammatory and oncogenic potential

CONTEXT

Endometrium in polycystic ovary syndrome (PCOS) presents altered gene expression indicating progesterone resistance and predisposing to reduced endometrial receptivity and endometrial cancer.

OBJECTIVE

We hypothesized that an altered endocrine/metabolic environment in PCOS may result in an endometrial "disease phenotype" affecting the gene expression of different endometrial cell populations, including stem cells and their differentiated progeny.

DESIGN AND SETTING

This was a prospective study conducted at an academic medical center.

PATIENTS AND MAIN OUTCOME MEASURES

Proliferative-phase endometrium was obtained from 6 overweight/obese PCOS (National Institutes of Health criteria) and 6 overweight/obese controls. Microarray analysis was performed on fluorescence-activated cell sorting-isolated endometrial epithelial cells (eEPs), endothelial cells, stromal fibroblasts (eSFs), and mesenchymal stem cells (eMSCs). Gene expression data were validated using microfluidic quantitative RT-PCR and immunohistochemistry.

RESULTS

The comparison between eEP(PCOS) and eEP(Ctrl) showed dysregulation of inflammatory genes and genes with oncogenic potential (CCL2, IL-6, ORM1, TNAIFP6, SFRP4, SPARC). eSF(PCOS) and eSF(Ctrl) showed up-regulation of inflammatory genes (C4A/B, CCL2, ICAM1, TNFAIP3). Similarly, in eMSC(PCOS) vs eMSC(Ctrl), the most up-regulated genes were related to inflammation and cancer (IL-8, ICAM1, SPRR3, LCN2). Immunohistochemistry scoring showed increased expression of CCL2 in eEP(PCOS) and eSF(PCOS) compared with eEP(Ctrl) and eSF(Ctrl) and IL-6 in eEP(PCOS) compared with eEP(Ctrl).

CONCLUSIONS

Isolated endometrial cell populations in women with PCOS showed altered gene expression revealing inflammation and prooncogenic changes, independent of body mass index, especially in eEP(PCOS) and eMSC(PCOS), compared with controls. The study reveals an endometrial disease phenotype in women with PCOS with potential negative effects on endometrial function and long-term health.

Comparison of antiproliferative effects of metformine and progesterone on estrogen-induced endometrial hyperplasia in rats

Metformin has been shown to inhibit the growth of endometriotic implants, and reverse endometrial hyperplasia when combined with oral contraceptive in a case report. The aim of this study is to compare the antiproliferative effects of medroxyprogesterone acetate (MPA), and metformin in oopherectomized rat endometrium. Forty oopherectomized Wistar-Albino rats were used, and assigned to receive saline, 17 β Estradiol hemihydrate (4 mg/kg), 17 β Estradiol hemihydrate (4 mg/kg) and metformin (50 mg/kg), 17 β Estradiol hemihydrate (4 mg/kg) and MPA (1 mg/day) for 14 days. Histological markers of uterotrophy, including endometrial height, luminal ephitelial cell height and density of endometrial glands on hysterectomy speciments were quantified for each specimen. Rats treated with estradiol had significantly increased in endometrial height, endomerial luminal epithelial height and endometrial gland densitiy than the other groups. Metformin and MPA acetate significantly reduced all parameters indicating endometrial hyperplasia, and uterotrophy with respect to the control group. Antiproliferative effects of metformin, and MPA was found to be comparable for all three parameters. In conclusion, metformin attenuates estrogen-induced endometrial hyperplasia in ooferectomized rats to the same degree as progesterone.

Interleukin-4 and prostaglandin E2 synergistically up-regulate 3β-hydroxysteroid dehydrogenase type 2 in endometrioma stromal cells

CONTEXT

Endometriosis is a chronic inflammatory disease in which immune response and production of estrogen in endometriotic tissues are involved in the development of the disease. Prostaglandin E2 (PGE2) stimulates aromatase (P450arom) expression in endometrioma stromal cells (ESCs) and increases the production of estrogens. On the other hand, an accumulating amount of evidence suggests that IL-4, a typical Th2 cytokine, plays important roles in the disease.

OBJECTIVE

The objective of the investigation was to study the effect of IL-4 on the expression of 3β-hydroxysteroid dehydrogenase (HSD3B2), a pivotal enzyme for estrogen production, in ESCs.

DESIGN, PATIENTS, AND MAIN OUTCOME MEASURES

ESCs were isolated from ovarian endometrioma tissues and cultured with IL-4 and PGE2. CP-690550, a Janus protein tyrosine kinase 3 inhibitor, and HSD3B2 small interfering RNA were added to the culture. Gene expression of HSD3B2 and P450arom was examined by quantitative RT-PCR. Dehydroepiandrosterone (DHEA) was added to the culture, and then the combined enzyme activity of HSD3B2, which converts DHEA to androstenedione, and P450arom, which converts androstenedione to estrone, was examined by measuring estrone concentration in the supernatants with a specific enzyme immunoassay.

RESULTS

IL-4 increased the expression of HSD3B2 mRNA in a dose-dependent manner. CP-650550 inhibited the IL-4-induced increase in HSD3B2 mRNA expression. PGE2 also increased the expression of HSD3B2 mRNA, and the combination of IL-4 and PGE2 synergistically increased the expression of HSD3B2 mRNA. IL-4 had no effect on the expression of P450arom mRNA, whereas PGE2 increased the expression of P450arom mRNA. Although PGE2 alone increased the production of estrone from DHEA, the combination of IL-4 and PGE2 significantly augmented the production of estrone from DHEA. The enhanced production of estrone by the combination of IL-4 and PGE2 was inhibited by CP-690550 and HSD3B2 small interfering RNA.

CONCLUSIONS

IL-4 in combination with PGE2 may enhance estrogen production in endometriotic tissues, implying an elaborate mechanism that Th2 immune response augments inflammation-dependent progression of the disease.

Protective effect of metformin on periapical lesions in rats by decreasing the ratio of receptor activator of nuclear factor kappa B ligand/osteoprotegerin

INTRODUCTION

Metformin, one of the antihyperglycemic agents commonly used for the treatment of type 2 diabetes, was shown to inhibit osteoclast formation. The current study aimed to investigate the effects of systemically administered metformin on alveolar bone resorption and on the ratio of receptor activator of nuclear factor kappa B ligand/osteoprotegerin (RANKL/OPG) in rats subjected to experimental periapical lesions.

METHODS

Forty adult male Wistar rats were divided equally into control and experimental groups, and the pulp chambers of their mandibular first molars were exposed to the oral environment to induce periapical lesions. The experimental group received daily intramuscular injections of metformin at 40 mg/kg doses, whereas the control group received only the saline vehicle. The injections were initiated 1 day before the periapical lesion induction and then were continued daily throughout the entire experimental period. Two or 4 weeks after pulp exposure, the rats were killed, and the mandibles were prepared for histologic analysis, enzyme histochemistry, immunohistochemistry, and immunofluorescence.

RESULTS

The number of RANKL-positive and tartrate-resistant acid phosphatase (TRAP)-positive cells in the metformin-treated groups decreased on day 14, whereas the number of OPG-positive cells increased on day 28. The periapical bone loss area in the metformin-treated group significantly decreased on day 28 compared with the control group.

CONCLUSIONS

Metformin inhibits the periapical lesions possibly by lowering the RANKL/OPG ratio, subsequently reducing the number of osteoclasts and bone resorption areas.

The effects of metformin and letrozole on endometrium and ovary in a rat model

OBJECTIVE

The effects of metformin and letrozole on endometrium and ovarian reserve were studied in a rat model.

METHODS

Forty female Wistar albino mature rats at 8 weeks, weighing 180-260 g, were used for the study. These rats were randomly divided into four groups. Control group, eight rats, was given no medication by oral gavage. The rats in low-dose metformin group, 10 rats, were given 100 mg/kg/day of oral metformin. The rats in high-dose metformin group, 10 rats, were given 200 mg/kg/day of oral metformin. The rats in letrozole, 10 rats, were given 0.1 mg/kg/day of oral letrozole.

RESULTS

There was statistically significant difference in the endometrial thickness between the treatment groups and control group. The primordial follicle count was comparable in all treatment groups compared with control. Finally, there was no significant difference in total follicle count between the treatment groups and control.

CONCLUSIONS

This study showed that both metformin and letrozole had similar effects on endometrium and ovary in the rat model. Additionally, metformin had a little effect on endometrium than letrozole. Although metformin and letrozole might have tendency to enhance the total follicle count in the rat model, they had comparable effects on ovarian follicles and did not change the ovarian reserve compared with control.

Metformin modulates IL-8, IL-1β, ICAM and IGFBP-1 expression in human endometrial stromal cells

To evaluate the effects of metformin on endometrial stromal cell gene expression and on the decidualization process, endometrial biopsies were collected from five healthy, regularly cycling women. Stromal cell culture was performed and decidualized with oestrogen/progesterone in the presence or absence of metformin and thereafter stimulated with insulin. The effect of metformin on decidualization was analysed by prolactin determination in the cell culture supernatant. Gene expression of insulin-like growth factor binding protein 1 (IGFBP-1), interleukin (IL) 8 and 1β and intercellular adhesion molecule (ICAM) was analysed by real-time PCR. Decidualization was significantly diminished in cells incubated with metformin (P<0.05) accompanied by a significant reduction of prolactin secretion in the supernatant (day 10: 2.2 fold, P<0.05; day 15: 3.1 fold, P<0.05). IGFBP-1 gene expression was reduced after long-term metformin exposure (7.7 fold, P<0.05). The negative effect of insulin on IL-8 (4.8 fold) and IL-1β (9.3 fold) gene expression was similarly found in cells incubated with metformin. As far as is known, this is the first demonstration of a change in endometrial gene and protein expression after in-vitro stimulation with metformin, including a diminished decidualization process and changes in genes relevant to implantation.

Promoter-specific effects of metformin on aromatase transcript expression

Phase III aromatase inhibitors (AIs) are proving successful in the treatment of hormone-dependent postmenopausal breast cancer. Side-effects associated with total body aromatase inhibition have prompted new research into the development of breast-specific AIs. The identification of tissue- and disease-specific usage of aromatase promoters has made the inhibition of aromatase at the transcriptional level an interesting approach. We have previously demonstrated that AMPK-activating drugs, including metformin, were potent inhibitors of aromatase expression in primary human breast adipose stromal cells (hASCs). This study examines the promoter-specific effects of metformin on inhibiting aromatase expression in hASCs. Tumour-associated promoters PII/PI.3 were activated using forskolin (FSK)/phorbol ester (PMA), whereas normal adipose associated promoter PI.4 was activated using dexamethasone (DEX)/tumour necrosis factor-α (TNFα). Results demonstrate that metformin significantly decreased the FSK/PMA-, but not the DEX/TNFα-mediated expression of total aromatase at concentrations of 10, 20, and 50 μM (P ≤ 0.05). Using PCR to amplify promoter-specific transcripts of aromatase, it appears that the inhibition of the FSK/PMA-mediated expression of aromatase is due to decreases in PII/PI.3-specific transcripts, whereas no effect of metformin is observed on any promoter-specific transcript, including PI.4, in DEX/TNFα-treated hASCs. This report therefore supports the hypothesis that metformin would act as a breast-specific inhibitor of aromatase expression in the context of postmenopausal breast cancer.

Interleukin-17F increases the secretion of interleukin-8 and the expression of cyclooxygenase 2 in endometriosis

OBJECTIVE

To examine the effects of interleukin (IL)-17F on the secretion of IL-8 and the gene expression of cyclooxygenase 2 (COX2) in endometriotic stromal cells.

DESIGN

In vitro experimental study using human samples.

SETTING

University hospital.

PATIENT(S)

Endometriotic tissues were obtained from women with ovarian endometriomas undergoing laparoscopic surgery.

INTERVENTION(S)

Endometriotic stromal cells (ESCs) were cultured with IL-17F.

MAIN OUTCOME MEASURE(S)

Concentrations of IL-8 were measured by a specific ELISA, and messenger RNA levels of IL-8 and COX2 were measured by real-time reverse transcription-polymerase chain reaction (PCR).

RESULT(S)

IL-17F increased the secretion of IL-8 from ESCs, and the effect was inhibited by antibodies for IL-17 receptor A and IL-17 receptor C. Tumor necrosis factor α (TNF-α) synergistically enhanced IL-17F-induced increase in IL-8 secretion from ESCs. The IL-17F increased the gene expression of IL-8 and COX2 in ESCs.

CONCLUSION(S)

These findings suggest that IL-17F may stimulate the development of endometriosis by up-regulation of IL-8 and COX2.

TGF-β1 induces proteinase-activated receptor 2 (PAR2) expression in endometriotic stromal cells and stimulates PAR2 activation-induced secretion of IL-6

BACKGROUND

Proteinase-activated receptor 2 (PAR2) is a G-protein-coupled receptor that is activated by several serine proteases. PAR2 activation in endometriotic stromal cells (ESCs) has been implicated in the development of endometriosis but the regulatory mechanism of PAR2 expression in ESC is unknown. Our objective was to study the mechanism by which PAR2 expression may be regulated in endometriotic lesions.

METHODS

Primary cultures of ESCs were treated with transforming growth factor-β (TGF-β) 1, tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β), and the expression of PAR2 was examined by real-time quantitative PCR. ESCs pretreated with or without TGF-β1 were treated with PAR2 agonist peptide (PAR2AP) and the secretion of the pro-endometriotic cytokine, IL-6, was measured using a specific enzyme-linked immunosorbent assay. Effects of TGF-β type 1 inhibitor, SB431542, and PAR2 small interfering RNA (siRNA) on the TGF-β1 stimulation of PAR2 gene expression and PAR2AP-induced IL-6 secretion were also evaluated. To study intracellular signaling, effects of inhibitors of mitogen-activated protein kinases (MAPKs) and phosphoinositide 3-kinase (PI3K) and of Smad4 siRNA on the TGF-β1-induced PAR2 gene expression were studied.

RESULTS

Only TGF-β1, but neither TNF-α nor IL-1β, increased gene expression of PAR2. Activation of PAR2 with PAR2AP increased the secretion of IL-6 from ESCs. As expected, TGF-β1 pretreatment dose-dependently enhanced the PAR2AP-induced increase in IL-6 secretion from ESCs. Treatment of ESCs with the TGF-β type 1 inhibitor, SB431542, inhibited both TGF-β1-stimulation of PAR2 gene expression and PAR2AP-induced IL-6 secretion. Transfection of ESCs with PAR2 siRNA produced a similar inhibition of IL-6 secretion. The TGF-β1-induced increase in PAR2 gene expression was repressed by inhibition of p38 MAPK, p42/44 MAPK or PI3K, but not by knockdown of Smad4 expression.

CONCLUSIONS

In view of significant roles of PAR2 and IL-6 in endometriosis, the TGF-β1-induced increase in PAR2 expression may be an elaborate mechanism that augments the progression of the disease.

Insulin and metformin may prevent renal injury in young type 2 diabetic Goto-Kakizaki rats

Type 2 diabetes is increasing at epidemic proportions throughout the world, and diabetic nephropathy is the principal cause of end stage renal failure. Approximately 40% of patients with type 2 diabetes may progress to nephropathy and a good metabolic control can prevent the development of diabetic renal injury. The aim of our study was to evaluate, in young type 2 diabetic Goto-Kakizaki (GK) rats fed with atherogenic diet, the effects of the anti-diabetic compounds insulin, metformin and gliclazide on renal damage. GK rats fed with atherogenic diet showed increased body weight and fasting blood glucose, total cholesterol, triglycerides, C-reactive protein and protein carbonyl levels and lower HDL-cholesterol concentration; renal markers of inflammation and fibrosis were also elevated. All the anti-diabetic agents ameliorated fasting glycaemia and insulin resistance but only insulin and metformin were able to improve glycoxidation, fibrosis and inflammation kidney parameters. Our data suggest that insulin and metformin treatments, improving glicoxidative, inflammatory and fibrotic renal damage markers, play a key role in the prevention of diabetic nephropathy.

Metformin treatment may increase omentin-1 levels in women with polycystic ovary syndrome

OBJECTIVE

Polycystic ovary syndrome (PCOS) is associated with the metabolic syndrome. Decreased omentin-1 levels are associated with obesity and diabetes. To study the effects of metformin treatment on omentin-1 levels in PCOS subjects and effects of omentin-1 on in vitro migration and angiogenesis.

RESEARCH DESIGN AND METHODS

Serum omentin-1 was measured by ELISA. Angiogenesis was assessed by studying capillary tube formation in human microvascular endothelial cells (HMEC-1) on growth factor reduced Matrigel. Endothelial cell migration assay was performed in a modified Boyden chamber. Nuclear factor-κB (NF-κB) was studied by stably transfecting HMEC-1 cells with a cis-reporter plasmid containing luciferase reporter gene linked to five repeats of NF-κB binding sites. Akt phosphorylation was assessed by Western blotting.

RESULTS

Serum omentin-1 was significantly lower in PCOS women (P < 0.05). After 6 months of metformin treatment, there was a significant increase in serum omentin-1 (P < 0.01). Importantly, changes in hs-CRP were significantly negatively correlated with changes in serum omentin-1 (P = 0.036). In vitro migration and angiogenesis were significantly increased in serum from PCOS women (P < 0.01) compared with matched control subjects; these effects were significantly attenuated by metformin treatment (P < 0.01) plausibly through the regulation of omentin-1 levels via NF-κB and Akt pathways. CRP and VEGF induced in vitro migration, and angiogenesis was significantly decreased by omentin-1.

CONCLUSIONS

Increases in omentin-1 levels may play a role but are not sufficient to explain the decreased inflammatory and angiogenic effects of sera from metformin-treated PCOS women.

Recruitment of CCR6-expressing Th17 cells by CCL 20 secreted from IL-1 beta-, TNF-alpha-, and IL-17A-stimulated endometriotic stromal cells

In a novel paradigm of T cell differentiation, type 17 T helper (Th17) cells may play a significant role in endometriosis, a chronic inflammatory disease. However, the mechanism regulating the accumulation of Th17 cells in endometriotic tissues remains unknown. We hypothesized that Th17 cells migrate to endometriotic tissues through an interaction of the chemokine CC chemokine ligand (CCL)20 and its receptor CCR6. Using endometriotic tissues from women with endometriosis, we demonstrated, by flow cytometry, that Th17 cells in endometriotic tissues express CC chemokine receptor (CCR)6. Immunohistochemistry also revealed that CCL20 was expressed in the epithelial cells and stromal cells beneath the epithelium of endometriotic tissues. CCR6+ cells were small and round and scattered in the stroma in which abundant CCL20+ cells were detected. CCL20 caused selective migration of Th17 cells in the peripheral blood in a migration assay. IL-1β, TNF-α, and IL-17A increased the secretion of CCL20 in cultured endometriotic stromal cells. Inhibitors of p38- and p42/44-MAPKs, and stress-activated protein kinase/c-Jun kinase suppressed the secretion of CCL20 increased by IL-1β, TNF-α, and IL-17A. This suggests that the CCL20/CCR6 system is involved in the migration of Th17 cells to endometriotic tissues and that proinflammatory cytokines contribute to the development of endometriosis via up-regulation of CCL20 secretion from endometriotic stromal cells.

Isolated and combined action of tamoxifen and metformin in wild-type, tamoxifen-resistant, and estrogen-deprived MCF-7 cells

Resistance to tamoxifen (TAM) and aromatase inhibitors represents a major drawback to the treatment of hormone-dependent breast cancer, and strategies to overcome this problem are urgently needed. The anti-diabetic biguanide metformin (MF) exerts pleiotropic effects which could enhance the effectiveness of available hormonal therapies. This study modeled several aspects of hormonal therapy in women and examined the effectiveness of MF under those conditions. For cell growth evaluation, wild-type (wt), TAM-resistant (TAM-R), and long-term estradiol-deprived (LTED) MCF-7 cells, as a model of aromatase inhibitor resistance, were grown in the presence or absence of TAM or MF for 5 days. For immunoblot analysis and aromatase activity measurements, these cells were grown for 48 h. Wild-type and LTED cells were equally sensitive to the growth inhibitory effects of TAM and MF, while TAM-R cells were less sensitive to TAM than to MF. Partial additive effects on cell number of TAM combined with MF were greatest (if compared with isolated TAM action) in TAM-R and LTED cells. In contrast to the decrease in PCNA values in TAM-resistant cells treated with the TAM and MF combination, no other changes were found in the levels of this proliferation marker. These findings suggested a major component of apoptosis in the growth inhibitory effect. This was confirmed with Western blot analysis of PARP and caspase 7 as well as with apoptosis ELISA assay. MF also altered signaling pathways. AMP-kinase was stimulated by MF approximately equally in MCF-7, TAM-R, and LTED cells, while inhibition by biguanide of p-S6K as a downstream target of mTOR was strongest in TAM-R cells. Under the influence of MF, expression of ER-α was decreased in wt MCF-7 cells suggesting possible involvement of this compound in estrogen signaling. Metformin interacts additively with TAM to reduce neoplastic cells growth. The cellular context (including loss of sensitivity to TAM and estrogen deprivation) is of importance in influencing breast cancer responses to MF and to a combination of MF and TAM.

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.

Metformin decreases IGF1-induced cell proliferation and protein synthesis through AMP-activated protein kinase in cultured bovine granulosa cells

Although its mechanism of action is still unclear, metformin is an anti-diabetic drug effective to restore cyclicity and spontaneous ovulation in women with polycystic ovary syndrome. It may also reduce the risk of cancer. We have recently shown that metformin treatment decreases steroidogenesis through AMP-activated kinase (AMPK) in granulosa cells of various species. Here, we investigated the effects and the molecular mechanisms of metformin in IGF1-induced proliferation and protein synthesis in cultured bovine granulosa cells. Treatment with metformin (10 mM) for 24 h reduced cell proliferation and the levels of cyclin D2 and E, and increased the associations cyclin D2/p21 and cyclin D2/p27 without affecting cell viability in response to IGF1 (10(-8) M). It also decreased IGF1-induced protein synthesis and phosphorylation of P70S6 kinase and ribosomal S6 protein. Interestingly, metformin treatment for 1 h decreased MAPK3/1 (ERK1/2) and P90RSK phosphorylation without affecting AKT phosphorylation in response to IGF1. Adenovirus-mediated expression of dominant-negative AMPK totally abolished the effects of metformin on cell proliferation and phosphorylation of P70S6K in response to IGF1. It also eliminated the inhibitory effects of metformin on MAPK3/1 and P90RSK phosphorylation. Taken together, our results strongly suggest that metformin reduces cell growth, protein synthesis, MAPK3/1, and P90RSK phosphorylation in response to IGF1 through an AMPK-dependent mechanism in cultured bovine granulosa cells.

Metformin inhibits inflammatory angiogenesis in a murine sponge model

To investigate the effects of metformin on angiogenesis, on inflammatory cell accumulation and on production of endogenous cytokines in sponge implant in mice. Polyester-polyurethane sponges were implanted in Swiss mice and metformin (40 or 400mg/kg/day) was given orally for six days. The implants collected at day 7 postimplantation were processed for the assessment of hemoglobin (Hb), myeloperoxidase (MPO), N-acetylglucosaminidase (NAG) e collagen used as indexes for angiogenesis, neutrophil and macrophage accumulation and extracellular matrix deposition, respectively. Relevant inflammatory, angiogenic and fibrogenic cytokines were also determined. Metformin treatment attenuated the main components of the fibrovascular tissue, wet weight, vascularization (Hb content), macrophage recruitment (NAG activity), collagen deposition and the levels of transforming growth factor (TGF-beta1) intraimplant. A regulatory function of metformin on multiple parameters of main components of inflammatory angiogenesis has been revealed giving insight into the potential therapeutic underlying the actions of metformin.

Metformin inhibits aromatase via an extracellular signal-regulated kinase-mediated pathway

Metformin treatment, now widely prescribed in polycystic ovary syndrome, is aimed at correcting the associated insulin resistance, but it has also been shown to directly inhibit ovarian steroidogenesis. The mechanisms, however, by which metformin inhibits estradiol production in human granulosa cells remains unknown. Granulosa luteal cells were incubated with metformin, insulin, or combined metformin and insulin treatment, and aromatase mRNA expression was quantified using real-time RT-PCR. Enzyme activity was assessed by the conversion of (3)H-androstenedione to estrone and estradiol. Metformin's effect on the expression of specific untranslated first exon aromatase promoters was analyzed using semiquantitative PCR. The involvement of MAPK kinase (MEK)/ERK pathway was investigated by immunoblotting for aromatase, phosphorylated, and total ERK-1,2 from cells cultured as above with/without the MEK inhibitor PD98059. Metformin significantly inhibited basal and insulin-stimulated aromatase mRNA expression, with parallel results from the aromatase activity assay and protein assessment. This suppression was via down-regulation of aromatase promoter II, I.3, and 1.4 expression and was reversed by the addition of PD98059. Involvement of the ERK signaling pathway was demonstrated by the significant increase in phosphorylated ERK-1,2 with the combined metformin and insulin treatment. We have shown for the first time in human granulosa cells that metformin signficantly attenuated basal and insulin-stimulated P450 aromatase mRNA expression and activity, via silencing of key promoters. This occurred by activation of MEK/ERK pathway, which negatively regulated aromatase production. This is an important consideration given metformin's widespread use in polycystic ovary syndrome and may further support a possible therapeutic indication in estrogen-dependent breast tumors.

Metformin, insulin, breast cancer and more

EVALUATION OF: Goodwin PJ, Pritchard KI, Ennis M, Clemons M, Graham M, Fantus IG: Insulin-lowering effects of metformin in women with early breast cancer. Clin. Breast Cancer 8(6), 501-505 (2008). This paper demonstrates that in breast cancer patients without overt diabetes mellitus, the antidiabetic biguanide metformin at a dose of 1500 mg/day reduces initially increased fasting insulinemia by 22.4% on average, 6 months after the onset of treatment. Since the same authors reported earlier on the association between preoperational insulinemia and breast cancer progression rate, an important conclusion from the above publication was that a Phase III randomized trial of metformin is warranted in order to assess the possible antitumor effect of this preparation. The evaluation presented below briefly addresses the history of the issue and possible targets of metformin effects beside its insulin-related action. It is argued that in selecting breast cancer patients for metformin therapy, one should take into account, along with the standard criteria, the pharmacogenetic aspects, estrogen production and specific features of estrogenic signaling, and also the expression of important metformin targets, including AMP-activated protein kinase, in tumor tissue.

Effect of DHEA and metformin on corpus luteum in mice

We evaluated the effect of hyperandrogenism in ovaries with functional and regressing corpora lutea (CL) and the action of metformin in preventing these possible alterations using a mouse model. To obtain a CL functional for 9+/-1 days, immature female mice of the BALB/c strain were injected i.p. with 10 IU/mouse of pregnant mare's serum gonadotropin (PMSG). DHEA (60 mg/kg body weight s.c., 24 and 48 h prior to kill) decreased both serum progesterone (P) and estradiol (E(2)) levels and increased the activity of superoxide dismutase (SOD) from ovaries with functional CL (on day 5 after PMSG). It increased P and E(2) and the activities of SOD and catalase (CAT) and decreased lipoperoxidation of ovaries with regressing CL (on day 9 after PMSG). Treatment with DHEA did not affect the production of prostaglandin F(2alpha) (PGF(2alpha)) or PGE by ovaries with functional CL, whereas DHEA decreased PGF(2alpha) and increased PGE production by ovaries with regressing CL. Metformin (50 mg/kg body weight, orally) given together with DHEA restored E(2) levels from mice with ovaries with functional CL and serum P, PGF(2alpha) and PGE levels, and oxidative balance in mice with ovaries with regressing CL. Metformin alone was able to modulate serum P and E(2) levels, lipoperoxidation, SOD and CAT, and the 5,5-dimethyl-1-pyrroline N-oxide/(*)OH signal. These findings suggest that hyperandrogenism is able to induce or to rescue CL from luteolysis and metformin treatment is able to prevent these effects.

Interleukin-4 stimulates proliferation of endometriotic stromal cells

Several lines of evidence indicate that the Th2 immune response is associated with endometriosis. Although an increased concentration of interleukin (IL)-4, a typical Th2 cytokine, has been reported in endometriotic tissues, the implication of this for endometriosis has not been determined. To investigate a possible role of IL-4 in the development of endometriosis, we examined the presence of IL-4-producing cells in endometriotic tissues and the effect of IL-4 on proliferation of endometriotic stromal cells. Endometriotic stromal cells were isolated from endometriotic tissues obtained from women undergoing surgery for endometrioma. Immunohistochemistry of endometriotic tissues revealed that IL-4-positive cells were abundant in the stroma. The effect of IL-4 on proliferation of endometriotic stromal cells was studied using cell counting and BrdU incorporation assays. IL-4 (0.1 to 10 ng/ml) significantly increased cell number and BrdU incorporation in a dose-dependent manner, and the proliferative effect of IL-4 was inhibited by anti-IL-4 receptor antibody. IL-4-induced activation of mitogen-activated protein kinases in endometriotic stromal cells was examined by Western blotting. IL-4 induced phosphorylation of p38 mitogen-activated protein kinase, stress-activated protein kinase/c-Jun kinase, and p42/44 mitogen-activated protein kinase and inhibitors of these kinases suppressed IL-4-induced proliferation of endometriotic stromal cells. These findings suggest that proliferation of endometriotic stromal cells induced by locally produced IL-4 is involved in the development of endometriosis.

Interleukin (IL)-17A stimulates IL-8 secretion, cyclooxygensase-2 expression, and cell proliferation of endometriotic stromal cells

IL-17A is secreted from Th17 cells, a discovery leading to revision of the mechanism underlying the role of Th1/Th2 in the immune response. Strong evidence suggests that immune responses associated with inflammation are involved in the pathogenesis of endometriosis. In the present study, we first demonstrated that the presence of Th17 cells in peritoneal fluid of endometriotic women by flow cytometric analysis and IL-17A-positive cells in endometriotic tissues by immunohistochemistry. To investigate the role of IL-17A in the development of endometriosis, we then studied the effect of IL-17A on IL-8 production, cyclooxygensase-2 expression, and cell proliferation of cultured endometriotic stromal cells (ESCs). IL-17A enhanced IL-8 secretion from ESCs in a dose-dependent manner. The IL-17A-induced secretion of IL-8 from ESCs was suppressed by anti-IL-17 receptor A antibodies or inhibitors of p38 MAPK, p42/44 MAPK, and stress-activated protein kinase/c-Jun N-terminal kinase. Addition of TNFalpha synergistically increased IL-17A-induced IL-8 secretion from ESCs. IL-17A also enhanced the expression of cyclooxygensase-2 mRNA and proliferation of ESCs. IL-17A may play a role in the development of endometriosis by stimulating inflammatory responses and proliferation of ESCs.