No abstract

Fetal exposure of male rats to di (n-butyl) phthalate (DBP) induces testicular changes remarkably similar to testicular dysgenesis syndrome in humans; these include induction of focal areas of dysgenetic tubules in otherwise normal testes. In searching for the fetal origins of the latter, we used image analysis to show that exposure to 500 mg/kg DBP [embryonic day (E)13.5-20.5)] caused abnormal aggregation of Leydig cells centrally in the fetal testis. This aggregation was not due to increase in Leydig cell number, and Leydig cell size was significantly reduced in DBP-exposed animals, as were testosterone levels and immunoexpression of P450 side-chain cleavage enzyme. The Leydig cell aggregates did not exhibit evidence of focal proliferation at E17.5-19.5. Using confocal microscopy and Leydig (3beta-hydroxysteroid dehydrogenase) and Sertoli (anti-Mullerian hormone) cell-specific markers, we show that fetal Leydig cell aggregates in DBP-exposed animals trap isolated Sertoli cells within them at E21.5. These areas of intermingled cells are still apparent on postnatal d 4, after cessation of DBP treatment, when they may form misshapen seminiferous cords that trap (intratubular) Leydig cells within them. These centrally located dysgenetic tubules contain germ cells in early puberty, but by adulthood they are Sertoli cell only, implying that presence of intratubular Leydig cells interferes with spermatogenesis. It is concluded that DBP-induced fetal Leydig cell aggregation may be a key event in formation of focal dysgenetic areas in the testis, and identification of the mechanisms underlying these events may give new insights into the fetal origins of testicular dysgenesis syndrome disorders in the human.

Genome-wide association studies (GWAS) have identified 14 tagging single nucleotide polymorphisms (tagSNPs) that are associated with the risk of colorectal cancer (CRC), and several of these tagSNPs are near bone morphogenetic protein (BMP) pathway loci. The penalty of multiple testing implicit in GWAS increases the attraction of complementary approaches for disease gene discovery, including candidate gene- or pathway-based analyses. The strongest candidate loci for additional predisposition SNPs are arguably those already known both to have functional relevance and to be involved in disease risk. To investigate this proposition, we searched for novel CRC susceptibility variants close to the BMP pathway genes GREM1 (15q13.3), BMP4 (14q22.2), and BMP2 (20p12.3) using sample sets totalling 24,910 CRC cases and 26,275 controls. We identified new, independent CRC predisposition SNPs close to BMP4 (rs1957636, P = 3.93×10−10) and BMP2 (rs4813802, P = 4.65×10−11). Near GREM1, we found using fine-mapping that the previously-identified association between tagSNP rs4779584 and CRC actually resulted from two independent signals represented by rs16969681 (P = 5.33×10−8) and rs11632715 (P = 2.30×10−10). As low-penetrance predisposition variants become harder to identify—owing to small effect sizes and/or low risk allele frequencies—approaches based on informed candidate gene selection may become increasingly attractive. Our data emphasise that genetic fine-mapping studies can deconvolute associations that have arisen owing to independent correlation of a tagSNP with more than one functional SNP, thus explaining some of the apparently missing heritability of common diseases.

The role of androgens in the proliferation and maturation of Sertoli cells (SC) and the development of their capacity to support spermatogenesis remains poorly understood. We evaluated these functions in complete androgen receptor knockout (ARKO) and SC-selective androgen receptor knockout (SCARKO) mice. Compared with controls, ARKO mice exhibited a progressive reduction in SC number/testis, whereas SCARKOs showed minor changes, suggesting that androgen effects on SC number are not mediated via direct action on SCs. Immunoexpression of anti-Mullerian hormone (AMH), p27(kip1), GATA-1, and sulfated glycoprotein-2, which changes according to SC maturational status, occurred normally in ARKOs and SCARKOs. Functional capacity of SCs to support spermatogonia was similar in SCARKOs and controls, whereas ARKOs showed reduced capacity with age. SC capacity to support total germ cells revealed major deficits in ARKO and SCARKO adults, particularly with respect to postmeiotic germ cells. Using quantitative RT-PCR, the expression of SC markers was compared in d 50 testes. In ARKOs, expression of Pem, fatty acid binding protein, platelet-derived growth factor-A, and transferrin were all significantly reduced, whereas FSH receptor and AMH were increased. In SCARKOs, there were modest reductions in expression of cystatin-related gene highly expressed in testis and epididymis (cystatin-TE) and claudin-11, whereas expression of Pem, fatty acid binding protein, and platelet-derived growth factor-A was markedly reduced, highlighting these as potentially androgen-regulated SC genes that merit further study. In conclusion, androgen action is not required for maturation-dependent changes in immunoexpression of the SC markers AMH, p27(kip1), GATA-1, and sulfated glycoprotein-2 but is essential for expression of other SC genes, the attainment of normal SC number, and the support of meiotic and postmeiotic germ cell development.

BackgroundCertain phthalates can impair Leydig cell distribution and steroidogenesis in the fetal rat in utero, but it is unknown whether similar effects might occur in the human.ObjectivesOur aim in this study was to investigate the effects of di(n-butyl) phthalate (DBP), or its metabolite monobutyl phthalate (MBP), on testosterone production and Leydig cell aggregation (LCA) in fetal testis explants from the rat and human, and to compare the results with in vivo findings for DBP-exposed rats. We also wanted to determine if DBP/MBP affects testosterone production in vivo in the neonatal male marmoset.MethodsFetal testis explants obtained from the rat [gestation day (GD)19.5] and from the human (15–19 weeks of gestation) were cultured for 24–48 hr with or without human chorionic gonadotropin (hCG) or 22R-hydroxycholesterol (22R-OH), and with or without DBP/MBP. Pregnant rats and neonatal male marmosets were dosed with 500 mg/kg/day DBP or MBP.ResultsExposure of rats in utero to DBP (500 mg/kg/day) for 48 hr before GD21.5 induced major suppression of intratesticular testosterone levels and cytochrome P450 side chain cleavage enzyme (P450scc) expression; this short-term treatment induced LCA, but was less marked than longer term (GD13.5–20.5) DBP treatment. In vitro, MBP (10−3 M) did not affect basal or 22R-OH-stimulated testosterone production by fetal rat testis explants but slightly attenuated hCG-stimulated steroidogenesis; MBP induced minor LCA in vitro. None of these parameters were affected in human fetal testis explants cultured with 10−3 M MBP for up to 48 hr. Because the in vivo effects of DBP/MBP were not reproduced in vitro in the rat, the absence of MBP effects in vitro on fetal human testes is inconclusive. In newborn (Day 2–7) marmosets, administration of a single dose of 500 mg/kg MBP significantly (p = 0.019) suppressed blood testosterone levels 5 hr later. Similar treatment of newborn co-twin male marmosets for 14 days resulted in increased Leydig cell volume per testis (p = 0.011), compared with co-twin controls; this is consistent with MBP-induced inhibition of steroidogenesis followed by compensatory Leydig cell hyperplasia/hypertrophy.ConclusionsThese findings suggest that MBP/DBP suppresses steroidogenesis by fetal-type Leydig cells in primates as in rodents, but this cannot be studied in vitro.

The effects on reproductive tract development in male rats, of neonatal exposure to potent (reference) oestrogens, diethylstilboestrol (DES) and ethinyl oestradiol (EE), with those of two environmental oestrogens, octylphenol and hisphenol A were systematically compared. Other treatments, such as administration of a gonadotrophin-releasing hormone antagonist (GnRHa) or the anti-oestrogen tamoxifen or the anti-androgen flutamide, were used to aid interpretation of the pathways involved. All treatments were administered in the neonatal period before onset of puberty. The cellular sites of expression of androgen receptors (AR) and of oestrogen receptor-alpha (ERalpha) and ERbeta were also established throughout development of the reproductive system. The main findings were as follows: (i) all cell types that express AR also express one or both ERs at all stages of development; (ii) Sertoli cell expression of ERbeta occurs considerably earlier in development than does expression of AR; (iii) most germ cells, including fetal gonocytes, express ERbeta but not AR; (iv) treatment with high, but not low, doses of potent oestrogens such as DES and EE, induces widespread structural and cellular abnormalities of the testis and reproductive tract before puberty; (v) the latter changes are associated with loss of immunoexpression of AR in all affected tissues and a reduction in Leydig cell volume per testis; (vi) none of the effects in (iv) and (v) can be duplicated by treating with high-dose octylphenol or bisphenol A; (vi) none of the reproductive tract changes in (iv) and (v) can be induced by simply suppressing androgen production (GnRHa treatment) or action (flutamide treatment); and (vii) the adverse changes induced by high-dose DES (iv and v) can be largely prevented by co-administration of testosterone. Thus, it is suggested that many of the adverse changes to the testis and reproductive tract induced by exposure to oestrogens result from a combination of high oestrogen and low androgen action. High oestrogen action or low androgen action on their own are unable to induce the same changes.

Androgen control of penis development/growth is unclear. In rats, androgen action in a foetal ‘masculinisation programming window’ (MPW; e15.5–e18.5)’ predetermines penile length and hypospadias occurrence. This has implications for humans (e.g. micropenis). Our studies aimed to establish in rats when androgen action/administration affects development/growth of the penis and if deficits in MPW androgen action were rescuable postnatally. Thus, pregnant rats were treated with flutamide during the MPW ± postnatal testosterone propionate (TP) treatment. To assess penile growth responsiveness, rats were treated with TP in various time windows (late foetal, neonatal through early puberty, puberty onset, or combinations thereof). Phallus length, weight, and morphology, hypospadias and anogenital distance (AGD) were measured in mid-puberty (d25) or adulthood (d90) in males and females, plus serum testosterone in adult males. MPW flutamide exposure reduced adult penile length and induced hypospadias dose-dependently; this was not rescued by postnatal TP treatment. In normal rats, foetal (e14.5–e21.5) TP exposure did not affect male penis size but increased female clitoral size. In males, TP exposure from postnatal d1–24 or at puberty (d15–24), increased penile length at d25, but not ultimately in adulthood. Foetal + postnatal TP (e14–postnatal d24) increased penile size at d25 but reduced it at d90 (due to reduced endogenous testosterone). In females, this treatment caused the biggest increase in adult clitoral size but, unlike in males, phallus size was unaffected by TP during puberty (d15–24). Postnatal TP treatment advanced penile histology at d25 to more resemble adult histology. AGD strongly correlated with final penis length. It is concluded that adult penile size depends critically on androgen action during the MPW but subsequent growth depends on later androgen exposure. Foetal and/or postnatal TP exposure does not increase adult penile size above its ‘predetermined’ length though its growth towards this maximum is advanced by peripubertal TP treatment.

IntroductionHyperuricemia is a strong risk factor for gout. The incidence of gout and hyperuricemia has increased recently, which is thought to be, in part, due to changes in diet and lifestyle. Objective of this study was to investigate the association between plasma urate concentration and: a) food items: dairy, sugar-sweetened beverages (SSB) and purine-rich vegetables; b) related nutrients: lactose, calcium and fructose.MethodsA total of 2,076 healthy participants (44% female) from a population-based case-control study in Scotland (1999–2006) were included in this study. Dietary data was collected using a semi-quantitative food frequency questionnaire (FFQ). Nutrient intake was calculated using FFQ and composition of foods information. Urate concentration was measured in plasma.ResultsMean urate concentration was 283.8±72.1 mmol/dL (females: 260.1±68.9 mmol/dL and males: 302.3±69.2 mmol/dL). Using multivariate regression analysis we found that dairy, calcium and lactose intakes were inversely associated with urate (p = 0.008, p = 0.003, p = 0.0007, respectively). Overall SSB consumption was positively associated with urate (p = 0.008), however, energy-adjusted fructose intake was not associated with urate (p = 0.66). The intake of purine-rich vegetables was not associated to plasma urate (p = 0.38).ConclusionsOur results suggest that limiting purine-rich vegetables intake for lowering plasma urate may be ineffectual, despite current recommendations. Although a positive association between plasma urate and SSB consumption was found, there was no association with fructose intake, suggesting that fructose is not the causal agent underlying the SSB-urate association. The abundant evidence supporting the inverse association between plasma urate concentration and dairy consumption should be reflected in dietary guidelines for hyperuricemic individuals and gout patients. Further research is needed to establish which nutrients and food products influence plasma urate concentration, to inform the development of evidence-based dietary guidelines.