Impact of obesity on ovotoxicity induced by 7,12-dimethylbenz[a]anthracene in mice

Diet-induced obesity alters the ovarian chemical biotransformation and oxidative stress response proteins both basally and in response to 7,12-dimethylbenz[a]anthracene exposure

7,12-Dimethylbenz[a]anthracene (DMBA) is a polycyclic aromatic hydrocarbon that causes female infertility via DNA damage, and the ovary has the capacity to mitigate DMBA exposure via the action of proteins including the glutathione S-transferase (GST) family. Due to previous findings of DNA damage and a reduced ovarian chemical biotransformation response to DMBA exposure in hyperphagia-induced obese mice, this study investigated the hypothesis that diet-induced obesity would hamper the ovarian biotransformative response to DMBA exposure. Six-week-old C57BL6/J mice were fed either a normal rodent diet (L) or a high fat high sucrose diet (O) until the O group was ∼30% heavier than the L. Both L and O mice were exposed to either corn oil (C) or DMBA (1 mg/kg) for 7 d. Liver weight was increased (P < 0.05) in obese mice exposed to DMBA but no effect on spleen weight, uterine weight, ovary weight, estrous cyclicity, or circulating 17β-estradiol and progesterone were observed. Primordial and preantral follicle numbers were higher (P < 0.05) in the obese mice and there was a tendency (P = 0.055) for higher antral follicles in DMBA-exposed obese mice. The ovarian proteome was identified by LC-MS/MS analysis to be altered both by diet-induced obesity and by DMBA exposure with changes observed in levels of proteins involved in oocyte development and chemical biotransformation, including GST isoform pi. Fewer proteins were affected by the combined exposure of diet and DMBA than by a single treatment, indicating that physiological status impacts the response to DMBA exposure.

High fat diet-induced obesity and gestational DMBA exposure alter folliculogenesis and the proteome of the maternal ovary†

Obesity and ovotoxicant exposures impair female reproductive health with greater ovotoxicity reported in obese relative to lean females. The mother and developing fetus are vulnerable to both during gestation. 7,12-dimethylbenz[a]anthracene (DMBA) is released during carbon combustion including from cigarettes, coal, fossil fuels, and forest fires. This study investigated the hypothesis that diet-induced obesity would increase sensitivity of the ovaries to DMBA-induced ovotoxicity and determined impacts of both obesity and DMBA exposure during gestation on the maternal ovary. Female C57BL/6 J mice were fed a control or a High Sugar High Fat (45% kcal from fat; 20% kcal from sucrose) diet until ~30% weight gain was attained before mating with unexposed males. From gestation Day 7, mice were exposed intraperitoneally to either vehicle control (corn oil) or DMBA (1 mg/kg diluted in corn oil) for 7 d. Thus, there were four groups: lean control (LC); lean DMBA exposed; obese control; obese DMBA exposed. Gestational obesity and DMBA exposure decreased (P < 0.05) ovarian and increased liver weights relative to LC dams, but there was no treatment impact (P > 0.05) on spleen weight or progesterone. Also, obesity exacerbated the DMBA reduction (P < 0.05) in the number of primordial, secondary follicles, and corpora lutea. In lean mice, DMBA exposure altered abundance of 21 proteins; in obese dams, DMBA exposure affected 134 proteins while obesity alone altered 81 proteins in the maternal ovary. Thus, the maternal ovary is impacted by DMBA exposure and metabolic status influences the outcome.

Trajectory of primordial follicle depletion is accelerated in obese mice in response to 7,12-dimethylbenz[a]anthracene exposure†

Both obesity and exposure to environmental genotoxicants, such as 7,12-dimethylbenz[a]anthracene, negatively impair female reproductive health. Hyperphagic lean KK.Cg-a/a (n = 8) and obese KK.Cg-Ay/J (n = 10) mice were exposed to corn oil as vehicle control (CT) or 7,12-dimethylbenz[a]anthracene (1 mg/kg/day) for 7d intraperitoneally, followed by a recovery period. Obesity increased liver and spleen weight (P < 0.05), and 7,12-dimethylbenz[a]anthracene exposure decreased uterine weight (P < 0.05) in obese mice. Primordial follicle loss (P < 0.05) caused by 7,12-dimethylbenz[a]anthracene exposure was observed in obese mice only. Primary (lean P < 0.1; obese P < 0.05) and secondary (lean P < 0.05, obese P < 0.1) follicle loss initiated by 7,12-dimethylbenz[a]anthracene exposure continued across recovery. Reduced pre-antral follicle number in lean mice (P < 0.05), regardless of 7,12-dimethylbenz[a]anthracene exposure, was evident with no effect on antral follicles or corpora lutea number. Immunofluorescence staining of DNA damage marker, γH2AX, did not indicate ongoing DNA damage but TRP53 abundance was decreased in follicles (P < 0.05) of 7,12-dimethylbenz[a]anthracene-exposed obese mice. In contrast, increased (P < 0.05) superoxide dismutase was observed in the corpora lutea of 7,12-dimethylbenz[a]anthracene-exposed obese mice and reduced (P < 0.05) TRP53 abundance was noted in preantral and antral follicles of 7,12-dimethylbenz[a]anthracene-exposed obese mice. This study indicates that obesity influences ovotoxicity caused by a genotoxicant, potentially involving accelerated primordial follicle activation and hampering normal follicular dynamics.

Pre-pubertal obesity compromises ovarian oxidative stress, DNA repair and chemical biotransformation

Obesity in adult females impairs fertility by altering oxidative stress, DNA repair and chemical biotransformation. Whether prepubertal obesity results in similar ovarian impacts is under-explored. The objective of this study was to induce obesity in prepubertal female mice and assess puberty onset, follicle number, and abundance of oxidative stress, DNA repair and chemical biotransformation proteins basally and in response to 7,12-dimethylbenz(a)anthracene (DMBA) exposure. DMBA is a polycyclic aromatic hydrocarbon that has been shown to be ovotoxic. Lactating dams (C57BL6J) were fed either a normal rodent containing 3.5% kCal from fat (lean), or a high fat diet comprised of 60% kCal from fat, and 9% kCal from sucrose. The offspring were weaned onto the diet of their dam and exposed at postnatal day 35 to either corn oil or DMBA (1 mg/kg) for 7 d via intraperitoneal injection. Mice on the HFD had reduced (P < 0.05) age at puberty onset as measured by vaginal opening but DMBA did not impact puberty onset. Heart, spleen, kidney, uterus and ovary weight were increased (P < 0.05) by obesity and liver weight was increased (P < 0.05) by DMBA exposure in obese mice. Follicle number was largely unaffected by obesity or DMBA exposure, with the exception of primary follicle number, which were higher (P < 0.05) in lean DMBA exposed and obese control relative to lean control mice. There were also greater numbers (P < 0.05) of corpora lutea in obese relative to lean mice. In lean mice, DMBA exposure reduced (P < 0.05) the level of CYP2E1, EPHX1, GSTP1, BRCA1, and CAT but this DMBA-induced reduction was absent in obese mice. Basally, obesity reduced (P < 0.05) the abundance of CYP2E1, EPHX1, GSTP1, BRCA1, SOD1 and CAT. There was greater (P < 0.05) fibrotic staining in obese DMBA-exposed ovaries and PPP2CA was decreased (P < 0.05) in growing follicles by both obesity and DMBA exposure. Thus, prepubertal obesity alters the capacity of the ovary to respond to DNA damage, ovotoxicant exposure and oxidative stress.

Exposure to 7,12-dimethylbenz[a]anthracene impacts ovarian DNA damage sensing and repair proteins differently in lean and obese female mice and weight loss may mitigate obesity-induced ovarian dysfunction

Obesity impairs oocyte quality, fertility, pregnancy maintenance, and is associated with offspring birth defects. The model ovotoxicant, 7,12-dimethylbenz[a]anthracene (DMBA), causes ovarian DNA damage and follicle loss. Both DMBA-induced chemical biotransformation and the DNA damage response are partially attenuated in obese relative to lean female mice but whether weight loss could improve the DNA damage response to DMBA exposure has not been explored. Thus, at six weeks of age, C57BL/6 J female mice were divided in three groups: 1) Lean (L; n = 20) fed a chow diet for 12 weeks, 2) obese (O; n = 20) fed a high fat high sugar (HFHS) diet for 12 weeks and, 3) slim-down (S; n = 20). The S group was fed with HFHS diet for 7 weeks until attaining a higher body relative to L mice on week 7.5 and switched to a chow diet for 5 weeks to achieve weight loss. Mice then received either corn oil (CT) or DMBA (D; 1 mg/kg) for 7 d via intraperitoneal injection (n = 10/treatment). Obesity increased (P < 0.05) kidney and spleen weight, and DMBA decreased uterine weight (P < 0.05). Ovarian weight was reduced (P < 0.05) in S mice, but DMBA exposure increased ovary weight in the S mice. LC-MS/MS identified 18, 64, and 7 ovarian proteins as altered (P < 0.05) by DMBA in the L, S and O groups, respectively. In S and O mice, 24 and 8 proteins differed, respectively, from L mice. These findings support weight loss as a strategy to modulate the ovarian genotoxicant response.

Biological sex differences in hepatic response to in utero dimethylbenz(a)anthracene exposure

Fetal hepatic dimethylbenz(a)anthracene (DMBA) biotransformation is not defined, thus, this study investigated whether the fetal liver metabolizes DMBA and differs with biological sex. KK.Cg-a/a (lean; n = 20) or KK.Cg-Ay/J (obese; n = 20) pregnant mice were exposed to corn oil (CT) or DMBA (1 mg/kg bw/day) by intraperitoneal injection (n = 10/treatment) from gestation day 7-14. Postnatal day 2 male or female offspring livers were collected. Total RNA (n = 6) and protein (n = 6) were analyzed via a PCR-based array or LC-MS/MS, respectively. The level of Mgst3 was lower (P < 0.05) in livers of female compared to male offspring. Furthermore, in utero DMBA exposure increased (P < 0.1) Cyp2c29 and Gpx3 levels (P < 0.05) in female offspring. In male offspring, the abundance of Ahr, Comt (P < 0.1), Alox5, and Asna1 (P < 0.05) decreased due to DMBA exposure. Female and male offspring had 34 and 21 hepatic proteins altered (P < 0.05) by in utero DMBA exposure, respectively. Opposing patterns for hepatic CD81 and KRT78 occurred, being decreased in females but increased in males, while YWHAG was decreased by DMBA exposure in both. Functional KEGG pathway analysis identified enrichment of 26 and 13 hepatic metabolic proteins in male and female offspring, respectively, due to in utero DMBA exposure. In silico transcription factor analysis of differentially expressed proteins predicted involvement of female NRF1 but male AHR. Thus, hepatic biological sex differences and capacity to respond to toxicants in utero are supported.

Altered histone abundance as a mode of ovotoxicity during 7,12-dimethylbenz[a]anthracene exposure with additive influence of obesity†

Histones are slowly evolving chromatin components and chromatin remodeling can incorporate histone variants differing from canonical histones as an epigenetic modification. Several identified histone variants are involved with the environmental stress-induced DNA damage response (DDR). Mechanisms of DDR in transcriptionally inactive, prophase-arrested oocytes and epigenetic regulation are under-explored in ovarian toxicology. The study objective was to identify ovarian proteomic and histone modifications induced by DMBA exposure and an influence of obesity. Post-pubertal wildtype (KK.Cg-a/a; lean) and agouti (KK.Cg-Ay/J; obese) female mice, were exposed to either corn oil (control; CT) or DMBA (1 mg/kg) for 7d via intraperitoneal injection (n = 10/treatment). Ovarian proteome analysis (LC-MS/MS) determined that obesity altered 225 proteins (P < 0.05) with histone 3 being the second least abundant (FC = -5.98, P < 0.05). Histone 4 decreased by 3.33-fold, histone variant H3.3 decreased by 3.05-fold, and H1.2, H1.4 and H1.1(alpha) variants increased by 1.59, 1.90 and 2.01-fold, respectively (P < 0.05). DMBA exposure altered 48 proteins in lean mice with no observed alterations in histones or histone variants. In obese mice, DMBA exposure altered 120 proteins and histone 2B abundance increased by 0.30-fold (P < 0.05). In DMBA-exposed mice, obesity altered the abundance of 634 proteins. Histones 4, 3 and 2A type 1-F decreased by 4.03, 3.71, 0.43-fold, respectively, whereas histone variant H1.2 and linker histone, H15 increased by 2.72- and 3.07-fold, respectively (P < 0.05). Thus, DMBA exposure alters histones and histone variants, and responsivity is more pronounced during obesity, potentially altering ovarian transcriptional regulation.

Hepatic and ovarian effects of perfluorooctanoic acid exposure differ in lean and obese adult female mice

Obesity and overweight cause poor oocyte quality, miscarriage, infertility, polycystic ovarian syndrome, and offspring birth defects and affects 40% and 20% of US women and girls, respectively. Perfluorooctanoic acid (PFOA), a per- and poly-fluoroalkyl substance (PFAS), is environmentally persistent and has negative female reproductive effects including endocrine disruption, oxidative stress, altered menstrual cyclicity, and decreased fertility in humans and animal models. PFAS exposure is associated with non-alcoholic fatty liver disease which affects ∼24-26% of the US population. This study investigated the hypothesis that PFOA exposure impacts hepatic and ovarian chemical biotransformation and alters the serum metabolome. At 7 weeks of age, female lean, wild type (KK.Cg-a/a) or obese (KK.Cg-Ay/J) mice received saline (C) or PFOA (2.5 mg/Kg) per os for 15 d. Hepatic weight was increased by PFOA exposure in both lean and obese mice (P < 0.05) and obesity also increased liver weight (P < 0.05) compared to lean mice. The serum metabolome was also altered (P < 0.05) by PFOA exposure and differed between lean and obese mice. Exposure to PFOA altered (P < 0.05) the abundance of ovarian proteins with roles in xenobiotic biotransformation (lean - 6; obese - 17), metabolism of fatty acids (lean - 3; obese - 9), cholesterol (lean - 8; obese - 11), amino acids (lean - 18; obese - 19), glucose (lean - 7; obese - 10), apoptosis (lean - 18; obese - 13), and oxidative stress (lean - 3; obese - 2). Use of qRT-PCR determined that exposure to PFOA increased (P < 0.05) hepatic Ces1 and Chst1 in lean but Ephx1 and Gstm3 in obese mice. Also, obesity basally increased (P < 0.05) Nat2, Gpi and Hsd17b2 mRNA levels. These data identify molecular changes resultant from PFOA exposure that may cause liver injury and ovotoxicity in females. In addition, differences in toxicity induced by PFOA exposure occurs in lean and obese mice.

Scrambled eggs-Negative impacts of heat stress and chemical exposures on ovarian function in swine

Exposure to environmental toxicants and hyperthermia can hamper reproduction in female mammals including swine. Phenotypic manifestations include poor quality oocytes, endocrine disruption, infertility, lengthened time to conceive, pregnancy loss, and embryonic defects. The ovary has the capacity for toxicant biotransformation, regulated in part by the phosphatidylinositol-3 kinase signaling pathway. The impacts of exposure to mycotoxins and pesticides on swine reproduction and the potential for an emerging chemical class of concern, the per- and polyfluoroalkylated substances, to hamper porcine reproduction are reviewed. The negative impairments of heat stress (HS) on swine reproductive outcomes are also described and the cumulative effect of environmental exposures, such as HS, when present in conjunction with a toxicant is considered.

Obesity partially potentiates dimethylbenz[a]anthracene-exposed ovotoxicity by altering the DNA damage repair response in mice†

Obesity adversely affects reproduction, impairing oocyte quality, fecundity, conception, and implantation. The ovotoxicant, dimethylbenz[a]anthracene, is biotransformed into a genotoxic metabolite to which the ovary responds by activating the ataxia telangiectasia mutated DNA repair pathway. Basal ovarian DNA damage coupled with a blunted response to genotoxicant exposure occurs in obese females, leading to the hypothesis that obesity potentiates ovotoxicity through ineffective DNA damage repair. Female KK.Cg-a/a (lean) and KK.Cg-Ay/J (obese) mice received corn oil or dimethylbenz[a]anthracene (1 mg/kg) at 9 weeks of age for 7 days via intraperitoneal injection (n = 10/treatment). Obesity increased liver weight (P < 0.001) and reduced (P < 0.05) primary, preantral, and corpora lutea number. In lean mice, dimethylbenz[a]anthracene exposure tended (P < 0.1) to increase proestrus duration and reduced (P = 0.07) primordial follicle number. Dimethylbenz[a]anthracene exposure decreased (P < 0.05) uterine weight and increased (P < 0.05) primary follicle number in obese mice. Total ovarian abundance of BRCA1, γH2AX, H3K4me, H4K5ac, H4K12ac, and H4K16ac (P > 0.05) was unchanged by obesity or dimethylbenz[a]anthracene exposure. Immunofluorescence staining demonstrated decreased (P < 0.05) abundance of γH2AX foci in antral follicles of obese mice. In primary follicle oocytes, BRCA1 protein was reduced (P < 0.05) by dimethylbenz[a]anthracene exposure in lean mice. Obesity also decreased (P < 0.05) BRCA1 protein in primary follicle oocytes. These findings support both a follicle stage-specific ovarian response to dimethylbenz[a]anthracene exposure and an impact of obesity on this ovarian response.

PFOA-Induced Ovotoxicity Differs Between Lean and Obese Mice With Impacts on Ovarian Reproductive and DNA Damage Sensing and Repair Proteins

Perfluorooctanoic acid (PFOA) is an environmentally persistent perfluoroalkyl substance that is widely used in consumer products. Exposure to PFOA is associated with reproductive and developmental effects including endocrine disruption, delayed puberty in girls, and decreased fetal growth. In the United States, obesity affects 40% of women and 20% of girls, with higher rates in minority females. Obesity causes infertility, poor oocyte quality, miscarriage, and offspring defects. This study proposed that PFOA exposure would impact estrous cyclicity, ovarian steroid hormones, and the ovarian proteome and further hypothesized that obesity would impact PFOA-induced ovotoxicity. Female wild type (KK.Cg-a/a; lean) or KK.Cg-Ay/J mice (obese) received saline (CT) or PFOA (2.5 mg/kg) per os for 15 days beginning at 7 weeks of age. There were no effects on food intake, body weight, estrous cyclicity, serum progesterone, and heart, spleen, kidney, or uterus weight (p > .05). Ovary weight was decreased (p < .05) by PFOA exposure relative to vehicle control-treated mice in lean but not obese mice. Liquid chromatography-tandem mass spectrometry was performed on isolated ovarian protein and PFOA exposure altered the ovarian abundance of proteins involved in DNA damage sensing and repair pathways and reproduction pathways (p < .05) differentially in lean and obese mice. The data suggest that PFOA exposure alters ovary weight and differentially targets ovarian proteins in lean and obese females in ways that might reduce female fecundity.

Biomarkers and Mechanisms of Oxidative Stress-Last 20 Years of Research with an Emphasis on Kidney Damage and Renal Transplantation

Oxidative stress is an imbalance between pro- and antioxidants that adversely influences the organism in various mechanisms and on many levels. Oxidative damage occurring concomitantly in many cellular structures may cause a deterioration of function, including apoptosis and necrosis. The damage leaves a molecular “footprint”, which can be detected by specific methodology, using certain oxidative stress biomarkers. There is an intimate relationship between oxidative stress, inflammation, and functional impairment, resulting in various diseases affecting the entire human body. In the current narrative review, we strengthen the connection between oxidative stress mechanisms and their active compounds, emphasizing kidney damage and renal transplantation. An analysis of reactive oxygen species (ROS), antioxidants, products of peroxidation, and finally signaling pathways gives a lot of promising data that potentially will modify cell responses on many levels, including gene expression. Oxidative damage, stress, and ROS are still intensively exploited research subjects. We discuss compounds mentioned earlier as biomarkers of oxidative stress and present their role documented during the last 20 years of research. The following keywords and MeSH terms were used in the search: oxidative stress, kidney, transplantation, ischemia-reperfusion injury, IRI, biomarkers, peroxidation, and treatment.

Obesity alters the ovarian proteomic response to zearalenone exposure†

Zearalenone (ZEN), a nonsteroidal estrogenic mycotoxin, is detrimental to female reproduction. Altered chemical biotransformation, depleted primordial follicles and a blunted genotoxicant response have been discovered in obese female ovaries, thus, this study investigated the hypothesis that obesity would enhance ovarian sensitivity to ZEN exposure. Seven-week-old female wild-type nonagouti KK.Cg-a/a mice (lean) and agouti lethal yellow KK.Cg-Ay/J mice (obese) received food and water ad libitum, and either saline or ZEN (40 μg/kg) per os for 15 days. Body and organ weights, and estrous cyclicity were recorded, and ovaries collected posteuthanasia for protein analysis. Body and liver weights were increased (P < 0.05) in the obese mice, but obesity did not affect (P > 0.05) heart, kidney, spleen, uterus, or ovary weight and there was no impact (P > 0.05) of ZEN exposure on body or organ weight in lean or obese mice. Obese mice had shorter proestrus (P < 0.05) and a tendency (P = 0.055) for longer metestrus/diestrus. ZEN exposure in obese mice increased estrus but shortened metestrus/diestrus length. Neither obesity nor ZEN exposure impacted (P > 0.05) circulating progesterone, or ovarian abundance of EPHX1, GSTP1, CYP2E1, ATM, BRCA1, DNMT1, HDAC1, H4K16ac, or H3K9me3. Lean mice exposed to ZEN had a minor increase in γH2AX abundance (P < 0.05). In lean and obese mice, LC-MS/MS identified alterations to proteins involved in chemical metabolism, DNA repair and reproduction. These data identify ZEN-induced adverse ovarian modes of action and suggest that obesity is additive to ZEN-induced ovotoxicity.

Developmental origins of ovarian disorder: impact of maternal lean gestational diabetes on the offspring ovarian proteome in mice†

Gestational diabetes mellitus (GDM) is an obstetric disorder affecting approximately 10% of pregnancies. The four high-fat, high-sucrose (HFHS) mouse model emulates GDM in lean women. Dams are fed a HFHS diet 1 week prior to mating and throughout gestation resulting in inadequate insulin response to glucose in mid-late pregnancy. The offspring of HFHS dams have increased adiposity, thus, we hypothesized that maternal metabolic alterations during lean GDM would compromise ovarian function in offspring both basally and in response to a control or HFHS diet in adulthood. Briefly, DLPL were lean dams and control diet pups; DLPH were lean dams and HFHS pups; DHPL were HFHS dams and control diet pups; and DHPH were HFHS dams and HFHS pups. A HFHS challenge in the absence of maternal GDM (DLPL vs. DLPH) increased 3 and decreased 30 ovarian proteins. Maternal GDM in the absence of a dietary stress (DLPL vs. DHPL) increased abundance of 4 proteins and decreased abundance of 85 proteins in the offspring ovary. Finally, 87 proteins increased, and 4 proteins decreased in offspring ovaries due to dietary challenge and exposure to maternal GDM in utero (DLPL vs. DHPH). Canopy FGF signaling regulator 2, deleted in azoospermia-associated protein 1, septin 7, and serine/arginine-rich splicing factor 2 were altered across multiple offspring groups. Together, these findings suggest a possible impact on fertility and oocyte quality in relation to GDM exposure in utero as well as in response to a western diet in later life.

Obesity alters phosphoramide mustard-induced ovarian DNA repair in mice

Phosphoramide mustard (PM) destroys rapidly dividing cells and activates the DNA double strand break marker, γH2AX, and DNA repair in rat granulosa cells and neonatal ovaries. The effects of PM exposure on DNA damage and activation of DNA damage repair in lean and obese female mice were investigated. Wild type (lean) non agouti (a/a) and KK.Cg-Ay/J heterozygote (obese) mice received sesame oil or PM (95%; 25 mg/kg; intraperitoneal injection). Obesity increased (P < 0.05) hepatic and spleen but decreased (P < 0.05) uterine weight. PM exposure reduced (P < 0.05) spleen weight regardless of body composition, however, decreased (P < 0.05) ovarian and hepatic weight were observed in the obese PM-exposed females. PM decreased (P < 0.05) primordial and primary follicle number in lean females. Obesity and PM increased (P < 0.05) γH2AX protein. DNA damage repair genes Prkdc, Parp1, and Rad51 mRNA were unaltered by obesity, however, Atm and Xrcc6 mRNA were increased (P < 0.05) while Brca1 was reduced (P < 0.05). Obesity reduced (P < 0.05) PRKDC, XRCC6 and but increased (P < 0.05) ATM protein. ATM, BRCA1 and RAD51 protein levels were increased (P < 0.05) by PM exposure in both lean and obese mice, while PM-induced increased (P < 0.05) XRCC6 and PARP1 were observed only in lean mice. Thus, PM induces ovarian DNA damage in vivo; obesity alters DNA repair response gene mRNA and protein level; the ovary activates DNA repair proteins in response to PM; but obesity compromises the ovarian PM response.

Progressive obesity alters ovarian insulin, phosphatidylinositol-3 kinase, and chemical metabolism signaling pathways and potentiates ovotoxicity induced by phosphoramide mustard in mice

Mechanisms underlying obesity-associated reproductive impairment are ill defined. Hyperinsulinemia is a metabolic perturbation often observed in obese subjects. Insulin activates phosphatidylinositol 3-kinase (PI3K) signaling, which regulates ovarian folliculogenesis, steroidogenesis, and xenobiotic metabolism. The impact of progressive obesity on ovarian genes encoding mRNA involved in insulin-mediated PI3K signaling and xenobiotic biotransformation [insulin receptor (Insr), insulin receptor substrate 1 (Irs1), 2 (Irs2), and 3 (Irs3); kit ligand (Kitlg), stem cell growth factor receptor (Kit), protein kinase B (AKT) alpha (Akt1), beta (Akt2), forkhead transcription factor (FOXO) subfamily 1 (Foxo1), and subfamily 3 (Foxo3a), microsomal epoxide hydrolase (Ephx1), cytochrome P450 family 2, subfamily E, polypeptide 1 (Cyp2e1), glutathione S-transferase (GST) class Pi (Gstp1) and class mu 1 (Gstm1)] was determined in normal wild-type nonagouti (a/a; lean) and lethal yellow mice (KK.CG-Ay/J; obese) at 6, 12, 18, or 24 weeks of age. At 6 weeks, ovaries from obese mice had increased (P < 0.05) Insr and Irs3 but decreased (P < 0.05) Kitlg, Foxo1, and Cyp2e1 mRNA levels. Interestingly, at 12 weeks, an increase (P < 0.05) in Kitlg and Kit mRNA, pIRS1Ser302, pAKTThr308, EPHX1, and GSTP1 protein level was observed due to obesity, while Cyp2e1 mRNA and protein were reduced. A phosphoramide mustard (PM) challenge increased (P < 0.05) ovarian EPHX1 protein abundance in lean but not obese females. In addition, lung tissue from PM-exposed animals had increased (P < 0.05) EPHX1 protein with no impact of obesity thereon. Taken together, progressive obesity affected ovarian signaling pathways potentially involved in obesity-associated reproductive disorders.

Expression Levels of Some Detoxification Genes in Liver and Testis of Rats Exposed to a Single Dose of Methyl-Tertiary Butyl Ether

AIM

Methyl-tertiary-butyl ether (MTBE), a well-known gasoline oxygenate compound, is still used in several countries. Several studies investigated the effects of MTBE on the activity of phase II metabolism enzymes. There is no published data on the effect(s) of short-term exposure to MTBE on mRNA levels of antioxidant genes. Therefore, the present study was carried out.

METHODS

A total of 15 adults male Wistar rats were randomly divided into five equal experimental groups. They received a single dose of 0, 400, 800 and 1600 mg/Kg MTBE in peanut oil by gavages. The final group received no MTBE and peanut oil. After 24 hr animals were slaughtered then livers and testis were removed to extract the total RNA. Real-time PCR was done to detect the gene expressions of glutathione S-transferase family (Gstt1, Gstm1, and Gstp1).

RESULTS

The mRNAs levels of the examined genes neither in liver nor in testis showed a significant difference between the exposed groups and control rats.

CONCLUSIONS

The present data revealed that exposure to a single dose of MTBE has no significant effect on the mRNA levels of the Gstt1, Gstm1, and Gstp1 genes.

Obesity-related known and candidate SNP markers can significantly change affinity of TATA-binding protein for human gene promoters

BACKGROUND

Obesity affects quality of life and life expectancy and is associated with cardiovascular disorders, cancer, diabetes, reproductive disorders in women, prostate diseases in men, and congenital anomalies in children. The use of single nucleotide polymorphism (SNP) markers of diseases and drug responses (i.e., significant differences of personal genomes of patients from the reference human genome) can help physicians to improve treatment. Clinical research can validate SNP markers via genotyping of patients and demonstration that SNP alleles are significantly more frequent in patients than in healthy people. The search for biomedical SNP markers of interest can be accelerated by computer-based analysis of hundreds of millions of SNPs in the 1000 Genomes project because of selection of the most meaningful candidate SNP markers and elimination of neutral SNPs.

RESULTS

We cross-validated the output of two computer-based methods: DNA sequence analysis using Web service SNP_TATA_Comparator and keyword search for articles on comorbidities of obesity. Near the sites binding to TATA-binding protein (TBP) in human gene promoters, we found 22 obesity-related candidate SNP markers, including rs10895068 (male breast cancer in obesity); rs35036378 (reduced risk of obesity after ovariectomy); rs201739205 (reduced risk of obesity-related cancers due to weight loss by diet/exercise in obese postmenopausal women); rs183433761 (obesity resistance during a high-fat diet); rs367732974 and rs549591993 (both: cardiovascular complications in obese patients with type 2 diabetes mellitus); rs200487063 and rs34104384 (both: obesity-caused hypertension); rs35518301, rs72661131, and rs562962093 (all: obesity); and rs397509430, rs33980857, rs34598529, rs33931746, rs33981098, rs34500389, rs63750953, rs281864525, rs35518301, and rs34166473 (all: chronic inflammation in comorbidities of obesity). Using an electrophoretic mobility shift assay under nonequilibrium conditions, we empirically validated the statistical significance (α < 0.00025) of the differences in TBP affinity values between the minor and ancestral alleles of 4 out of the 22 SNPs: rs200487063, rs201381696, rs34104384, and rs183433761. We also measured half-life (t1/2), Gibbs free energy change (ΔG), and the association and dissociation rate constants, ka and kd, of the TBP-DNA complex for these SNPs.

CONCLUSIONS

Validation of the 22 candidate SNP markers by proper clinical protocols appears to have a strong rationale and may advance postgenomic predictive preventive personalized medicine.

Impact of obesity on 7,12-dimethylbenz[a]anthracene-induced altered ovarian connexin gap junction proteins in female mice

The ovarian gap junction proteins alpha 4 (GJA4 or connexin 37; CX37), alpha 1 (GJA1 or connexin 43; CX43) and gamma 1 (GJC1 or connexin 45; CX45) are involved in cell communication and folliculogenesis. 7,12-dimethylbenz[a]anthracene (DMBA) alters Cx37 and Cx43 expression in cultured neonatal rat ovaries. Additionally, obesity has an additive effect on DMBA-induced ovarian cell death and follicle depletion, thus, we investigated in vivo impacts of obesity and DMBA on CX protein levels. Ovaries were collected from lean and obese mice aged 6, 12, 18, or 24 wks. A subset of 18 wk old mice (lean and obese) were dosed with sesame oil or DMBA (1mg/kg; ip) for 14days and ovaries collected 3days thereafter. Cx43 and Cx45 mRNA and protein levels decreased (P<0.05) after 18 wks while Cx37 mRNA and protein levels decreased (P<0.05) after 24 wks in obese ovaries. Cx37 mRNA and antral follicle protein staining intensity were reduced (P<0.05) by obesity while total CX37 protein was reduced (P<0.05) in DMBA exposed obese ovaries. Cx43 mRNA and total protein levels were decreased (P<0.05) by DMBA in both lean and obese ovaries while basal protein staining intensity was reduced (P<0.05) in obese controls. Cx45 mRNA, total protein and protein staining intensity level were decreased (P<0.05) by obesity. These data support that obesity temporally alters gap junction protein expression and that DMBA-induced ovotoxicity may involve reduced gap junction protein function.

Enhanced susceptibility of ovaries from obese mice to 7,12-dimethylbenz[a]anthracene-induced DNA damage

7,12-Dimethylbenz[a]anthracene (DMBA) depletes ovarian follicles and induces DNA damage in extra-ovarian tissues, thus, we investigated ovarian DMBA-induced DNA damage. Additionally, since obesity is associated with increased offspring birth defect incidence, we hypothesized that a DMBA-induced DNA damage response (DDR) is compromised in ovaries from obese females. Wild type (lean) non agouti (a/a) and KK.Cg-Ay/J heterozygote (obese) mice were dosed with sesame oil or DMBA (1mg/kg; intraperitoneal injection) at 18weeks of age, for 14days. Total ovarian RNA and protein were isolated and abundance of Ataxia telangiectasia mutated (Atm), X-ray repair complementing defective repair in Chinese hamster cells 6 (Xrcc6), breast cancer type 1 (Brca1), Rad 51 homolog (Rad51), poly [ADP-ribose] polymerase 1 (Parp1) and protein kinase, DNA-activated, catalytic polypeptide (Prkdc) were quantified by RT-PCR or Western blot. Phosphorylated histone H2AX (γH2AX) level was determined by Western blotting. Obesity decreased (P<0.05) basal protein abundance of PRKDC and BRCA1 proteins but increased (P<0.05) γH2AX and PARP1 proteins. Ovarian ATM, XRCC6, PRKDC, RAD51 and PARP1 proteins were increased (P<0.05) by DMBA exposure in lean mice. A blunted DMBA-induced increase (P<0.05) in XRCC6, PRKDC, RAD51 and BRCA1 was observed in ovaries from obese mice, relative to lean counterparts. Taken together, DMBA exposure induced γH2AX as well as the ovarian DDR, supporting that DMBA causes ovarian DNA damage. Additionally, ovarian DDR was partially attenuated in obese females raising concern that obesity may be an additive factor during chemical-induced ovotoxicity.

Progressive obesity alters ovarian folliculogenesis with impacts on pro-inflammatory and steroidogenic signaling in female mice

Diet-induced obesity induces immune cell infiltration and inflammation in peri-ovarian adipose tissue and mRNA expression of inflammatory markers in ovarian tissue. Whether these changes are associated with obesity-related ovarian dysfunction remains unknown. In the present study, qRT-PCR and Western blotting techniques were used to compare mRNA and protein abundance of ovarian immune cell and inflammation markers, along with NF-kappaB and steroidogenic pathway members in normal wild-type non-agouti (a/a; lean) and lethal yellow mice (KK.CG-A(y/)J; obese) at 6, 12, 18, or 24 wk of age. Our data revealed that, beginning at 12 wk of age, NF-kappaB inflammatory signaling members were elevated (P < 0.05) in obese females. Interestingly obesity had opposing and temporal effects on the steroidogenic enzyme pathway. Obesity decreased (P < 0.05) STAR protein at 12, 18, and 24 wk of age. CYP11A1 and CYP19A1 proteins were increased (P < 0.05) at 12 wk but were decreased (P < 0.05) at 18 and 24 wk. Interestingly, CYP19A1 was increased in lethal yellow mouse ovaries at 6 wk of age, potentially indicating early puberty onset. These data demonstrate that obesity alters expression of ovarian inflammatory and steroidogenic pathway genes in ways which could adversely affect ovarian function.

Progressive obesity alters the steroidogenic response to ovulatory stimulation and increases the abundance of mRNAs stored in the ovulated oocyte

Obese women who are able to attain pregnancy are at increased risk for early-pregnancy loss due, in part, to reduced oocyte quality. We and others have demonstrated that female Lethal Yellow (LY) mice and female C57BL/6 mice fed a high fat diet (B6-HFD) exhibit phenotypes consistent with human obesity. These studies also showed that zygotes collected from LY and B6-HFD females have reduced developmental competence. The current hypothesis is that LY and B6-HFD females exhibit an abnormal response to gonadotropin stimulation compared to C57BL/6 controls fed normal rodent chow (B6-ND), resulting in the ovulation of oocytes with an altered molecular phenotype which may contribute to its reduced developmental competence. To test this hypothesis, age-matched B6-ND, B6-HFD, and LY females were stimulated with exogenous gonadotropins, then circulating hormone levels and the phenotypes of ovulated oocytes were analyzed. There was no difference in ovulation rate or in the percentage of morphologically abnormal oocytes collected from the oviduct of any females. Progesterone and progesterone/estradiol ratios, however, were increased in B6-HFD and LY compared to B6-ND females 16 hr post-human chorionic gonadotropin treatment. The transcript abundance of several candidate oocyte genes was also increased in B6-HFD- and LY-derived oocytes compared to B6-ND-derived oocytes. These data suggest that increased insulin and leptin levels of obese females elevated circulating progesterone concentrations, altered transcriptional activity during oocyte growth, and/or impaired mechanisms of RNA translation and degradation during oocyte maturation. These changes in mRNA abundance likely contribute to reduced oocyte quality and the subsequent poor embryogenesis associated with obesity.

Acute 7,12-dimethylbenz[a]anthracene exposure causes differential concentration-dependent follicle depletion and gene expression in neonatal rat ovaries

Chronic exposure to the polycyclic aromatic hydrocarbon 7,12-dimethylbenz[a]anthracene (DMBA), generated during combustion of organic matter including cigarette smoke, depletes all ovarian follicle types in the mouse and rat, and in vitro models mimic this effect. To investigate the mechanisms involved in follicular depletion during acute DMBA exposure, two concentrations of DMBA at which follicle depletion has (75 nM) and has not (12.5 nM) been observed were investigated. Postnatal day four F344 rat ovaries were maintained in culture for four days before a single exposure to vehicle control (1% DMSO; CT) or DMBA (12 nM; low-concentration or 75 nM; high-concentration). After four or eight additional days of culture, DMBA-induced follicle depletion was evaluated via follicle enumeration. Relative to control, DMBA did not affect follicle numbers after 4 days of exposure, but induced large primary follicle loss at both concentrations after 8 days; while, the low-concentration DMBA also caused secondary follicle depletion. Neither concentration affected primordial or small primary follicle number. RNA was isolated and quantitative RT-PCR performed prior to follicle loss to measure mRNA levels of genes involved in xenobiotic metabolism (Cyp2e1, Gstmu, Gstpi, Ephx1), autophagy (Atg7, Becn1), oxidative stress response (Sod1, Sod2) and the phosphatidylinositol 3-kinase (PI3K) pathway (Kitlg, cKit, Akt1) 1, 2 and 4 days after exposure. With the exception of Atg7 and cKit, DMBA increased (P < 0.05) expression of all genes investigated. Also, BECN1 and pAKT(Thr308) protein levels were increased while cKIT was decreased by DMBA exposure. Taken together, these results suggest an increase in DMBA bioactivation, add to the mechanistic understanding of DMBA-induced ovotoxicity and raise concern regarding female low concentration DMBA exposures.