Susceptibility to postnatal growth retardation induced by 5-AZA-2'-deoxycytidine in utero: gender specificity and correlation with reduced insulin-like growth factor 1.
ABSTRACT The DNA demethylating agent 5-AZA-2'-deoxyxytidine (5-AZA-CdR) alters gene expression in mice exposed during developmental stages and causes malformations and growth suppression. The aim of this study was to determine if 5-AZA-CdR-induced growth retardation is associated with alterations in energy metabolism or in serum IGF-1 levels. Mice were exposed in utero to 5-AZA-CdR at gestation day 10. At postnatal day 21, exposed pups were weaned and body weights recorded. At 3 months of age, reproductive capacity was studied. At 5 months old, after body weight was recorded mice were killed and serum was collected to determine serum glucose, corticosterone, and IGF-1 levels. The body weights of both treated males and females were reduced at weaning compared with controls, but by 5 months of age, only the male body weight was affected. Reproductive capacity of males and females was reduced with males being more affected. Levels of corticosterone and glucose were not altered. Serum IGF-1 levels were lower in males exposed in utero to 5-AZA-CdR when compared to controls, but not in females, and correlated significantly with body weights. Our data suggest that the decreased levels of IGF-1 associated with the treatment could be the cause of the observed growth retardation in the in utero-exposed mice. A gender dimorphic effect, where males are more affected, is evident.
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ABSTRACT: Intrauterine exposure to 5-AZA-2'-deoxycytidine (5-AZA-CdR) alters gene expression causing malformations, abnormal post-natal growth and altered reproductive capacity. To elucidate whether the phenomenon observed in 5-AZA-CdR in utero exposed male mice was a behavioral alteration, at gestation day (GD) 10, CD-1 pregnant mice were administered 1mg/kg i.p. of 5-AZA-CdR or saline solution. After parturition, the number and sex of pups were recorded. While litter size was not affected, the ratio of male to female offspring was altered in treated mice. To determine whether the phenotypic observation of male gender corresponded to the appropriate genotype, presence of Sry gene in 5-AZA-CdR F1 males was determined. At 3 months of age, the male sexual behavior test outlined by Chubb was conducted. Presence of vaginal plug and pregnancy were determined in the natural breeding phase. Mount latency and number of mounts per mouse were assessed in the behavioral test phase. In utero exposed male mice resulted in diminished mating behavior (as measured by vaginal plug presence, mount latency and number of mounts) and reduced sexual interest while exposed to a receptive female. While normal presence of Sry gene was observed, mating behavior was altered in exposed males suggesting that the reproductive alteration could be attributed to a behavioral phenomenon.NeuroToxicology 04/2004; 25(3):411-7. DOI:10.1016/j.neuro.2003.09.002
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ABSTRACT: Male infertility is one of the biggest concerns of today's health care community. In the US and other developed countries, approximately 70% of infertility among couples is attributed to male reproductive failure. Alterations in reproductive organ development and sperm production have been listed as the major causes of this phenomenon. Sex determination and differentiation, X chromosome inactivation, gene imprinting and normal germ cell development are important biological processes that, in turn, control mammalian reproduction. Specific patterns of gene expression and repression are important in such processes. The strong correlation between DNA methylation, a major epigenetic modification of the genome, and gene expression patterns is well documented. The effects of DNA methylation on the expression of genes affecting male reproductive organ development, spermatogenesis, and male sexual behavior have been reported, suggesting that alterations in DNA methylation could induce abnormal male sexual development and reproductive performance. Inheritance of epigenetic processes and changes in DNA methylation patterns induced by certain diets have been demonstrated in recent years. However, the effects of DNA methylation on male fertility have not been well studied. Since inherited altered DNA methylation patterns could be a cause of increased susceptibility to xenobiotics or abnormal phenotype in future generations, multigenerational studies oriented to determine the effects of xenobiotics affecting DNA methylation in male fertility are recommended.Frontiers in Bioscience 06/2004; 9:1189-200. DOI:10.2741/1332
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ABSTRACT: The mouse serves as an important model for insulin-like (IGF)-related research. However, lack of homologous mouse assays has prevented studies of the normal ontology of the murine IGF system. Therefore, we developed and validated immunoaassays for murine IGF-I, IGFBP-3 and ALS and studied levels of these analytes in mice. Using commercially available reagents, we developed and validated specific enzyme-linked immunosorbent assays (ELISAs) for murine IGF-I, IGFBP-3, and ALS. Levels of these analytes were measured in sera from CD-1 mice, male and female, sampled at 1, 2, 4, 8, 20 and 32 weeks of age. In addition, sera from pregnant and postpartum CD-1 mice were also studied. Validation of specific ELISAs for murine IGF-I, IGFBP-3 and ALS are described; all 3 assays were highly sensitive, precise and accurate. As measured by our homologous ELISA, IGF-I levels (ng/mL, mean+/-SD) in male mice were relatively low at 1 week (53+/-8), rising sharply to peak at 8 weeks of age (636+/-48), and gradually declining thereafter, reaching 395+/-64 at 32 weeks. IGF-I levels in non-pregnant female mice peaked at 4 weeks of age (548+/-77) declined at 8 weeks (417+/-61), then recovered to plateau at 539+/-78 and 535+/-88 at 20 and 32 weeks, respectively. In male mice, trends in IGFBP-3 were similar to the patterns of IGF-I. However, in non-pregnant female mice, the IGFBP-3 levels declined relatively slowly after peaking at 4-weeks of age, unlike IGF-I levels during this period. ALS levels followed the same pattern as IGF-I in both sexes. IGF-I to IGFBP-3 molar ratios (percent) were similar between sexes, rising continuously with age: approximately 30% at 1 week, 80% at 4 weeks, 135% at 32 weeks. IGF-I was reduced in 8 week old mice in mid-pregnancy (354+/-75 vs 417+/-61 in non-pregnant 8 week females), reaching a nadir in late-term (146+/-40), and only partially recovering in the postpartum period (239+/-23). IGFBP-3 was also lower in late-pregnancy (1245+/-100 vs 1925+/-439) and remained depressed postpartum. In contrast to IGF-I and IGFBP-3, ALS increased more than threefold in mid-pregnancy (12180+/-1641 vs 3741+/-910), followed by a 4-fold decrease in late-pregnancy (2964+/-489), recovering postpartum (6104+/-1178). We report the first ontological studies of IGF-I, IGFBP-3 and ALS in mice using newly-characterized sensitive, homologous immunoassays. Our results indicate that mice have a generally similar pattern in IGF-related axis components, with low levels early in life, increasing to peak during sexual maturation and declining thereafter. Significant gender differences in non-pregnant levels and dramatic changes during pregnancy were also found. Knowledge of the normal developmental changes in the murine IGF system and accurate tools for investigations of this system are a necessary foundation for research in this field.Growth Hormone & IGF Research 03/2008; 18(1):65-74. DOI:10.1016/j.ghir.2007.07.007