Kristin Connor

Epigenetic Changes in the Hypothalamic Proopiomelanocortin and Glucocorticoid Receptor Genes in the Ovine Fetus after Periconceptional Undernutrition

Maternal food restriction is associated with the development of obesity in offspring. This study examined how maternal undernutrition in sheep affects the fetal hypothalamic glucocorticoid receptor (GR) and the appetite-regulating neuropeptides, proopiomelanocortin (POMC) and neuropeptide Y, which it regulates. In fetuses from ewes undernourished from -60 to +30 d around conception, there was increased histone H3K9 acetylation (1.63-fold) and marked hypomethylation (62% decrease) of the POMC gene promoter but no change in POMC expression. In the same group, acetylation of histone H3K9 associated with the hypothalamic GR gene was increased 1.60-fold and the GR promoter region was hypomethylated (53% decrease). In addition, there was a 4.7-fold increase in hypothalamic GR expression but no change in methylation of GR gene expression in the anterior pituitary or hippocampus. Interestingly, hypomethylation of both POMC and GR promoter markers in fetal hypothalami was also identified after maternal undernutrition from -60 to 0 d and -2 to +30 d. In comparison, the Oct4 gene, was hypermethylated in both control and underfed groups. Periconceptional undernutrition is therefore associated with marked epigenetic changes in hypothalamic genes. Increase in GR expression in the undernourished group may contribute to fetal programming of a predisposition to obesity, via altered GR regulation of POMC and neuropeptide Y. These epigenetic changes in GR and POMC in the hypothalamus may also predispose the offspring to altered regulation of food intake, energy expenditure, and glucose homeostasis later in life.

Offspring of Mothers Fed a High Fat Diet Display Hepatic Cell Cycle Inhibition and Associated Changes in Gene Expression and DNA Methylation

The association between an adverse early life environment and increased susceptibility to later-life metabolic disorders such as obesity, type 2 diabetes and cardiovascular disease is described by the developmental origins of health and disease hypothesis. Employing a rat model of maternal high fat (MHF) nutrition, we recently reported that offspring born to MHF mothers are small at birth and develop a postnatal phenotype that closely resembles that of the human metabolic syndrome. Livers of offspring born to MHF mothers also display a fatty phenotype reflecting hepatic steatosis and characteristics of non-alcoholic fatty liver disease. In the present study we hypothesised that a MHF diet leads to altered regulation of liver development in offspring; a derangement that may be detectable during early postnatal life. Livers were collected at postnatal days 2 (P2) and 27 (P27) from male offspring of control and MHF mothers (n = 8 per group). Cell cycle dynamics, measured by flow cytometry, revealed significant G0/G1 arrest in the livers of P2 offspring born to MHF mothers, associated with an increased expression of the hepatic cell cycle inhibitor Cdkn1a. In P2 livers, Cdkn1a was hypomethylated at specific CpG dinucleotides and first exon in offspring of MHF mothers and was shown to correlate with a demonstrable increase in mRNA expression levels. These modifications at P2 preceded observable reductions in liver weight and liver∶brain weight ratio at P27, but there were no persistent changes in cell cycle dynamics or DNA methylation in MHF offspring at this time. Since Cdkn1a up-regulation has been associated with hepatocyte growth in pathologic states, our data may be suggestive of early hepatic dysfunction in neonates born to high fat fed mothers. It is likely that these offspring are predisposed to long-term hepatic dysfunction.

Nature, nurture or nutrition? Impact of maternal nutrition on maternal care, offspring development and reproductive function

•  Maternal high fat nutrition during pregnancy and lactation significantly reduced maternal care during the early neonatal period; but reduced maternal care was not associated with an offspring phenotype. •  Maternal high fat nutrition resulted in maternal obesity characterized by increased fat mass, hyperleptinaemia, hyperinsulinaemia. •  Maternal high fat nutrition resulted in fatter offspring before puberty and advanced pubertal onset. •  Adult female offspring of high fat‐fed mothers have altered reproductive function, reflected in an increased likelihood of prolonged or persistent oestrus. •  These phenotypic effects were not related to maternal care suggesting that poor maternal nutrition, rather than inadequate maternal care, could be the primary driver of the observed alterations in offspring development and reproductive function.

Epigenetic changes in fetal hypothalamic energy regulating pathways are associated with maternal undernutrition and twinning

Undernutrition during pregnancy is implicated in the programming of offspring for the development of obesity and diabetes. We hypothesized that maternal programming causes epigenetic changes in fetal hypothalamic pathways regulating metabolism. This study used sheep to examine the effect of moderate maternal undernutrition (60 d before to 30 d after mating) and twinning to investigate changes in the key metabolic regulators proopiomelanocortin (POMC) and the glucocorticoid receptor (GR) in fetal hypothalami. Methylation of the fetal hypothalamic POMC promoter was reduced in underfed singleton, fed twin, and underfed twin groups (60, 73, and 63% decrease, respectively). This was associated with reduced DNA methyltransferase activity and altered histone methylation and acetylation. Methylation of the hypothalamic GR promoter was decreased in both twin groups and in maternally underfed singleton fetuses (52, 65, and 55% decrease, respectively). This correlated with changes in histone methylation and acetylation and increased GR mRNA expression in the maternally underfed singleton group. Alterations in GR were hypothalamic specific, with no changes in hippocampi. Unaltered levels of OCT4 promoter methylation indicated gene‐specific effects. In conclusion, twinning and periconceptional undernutrition are associated with epigenetic changes in fetal hypothalamic POMC and GR genes, potentially resulting in altered energy balance regulation in the offspring.—Begum, G., Stevens, A., Smith, E. B., Connor, K., Challis, J. R. G., Bloomfield, F., White, A. Epigenetic changes in fetal hypothalamic energy regulating pathways are associated with maternal undernutrition and twinning. FASEB J. 26, 1694–1703 (2012). www.fasebj.org

Fetal exposure to excess glucocorticoid is unlikely to explain the effects of periconceptional undernutrition in sheep

Periconceptional undernutrition alters fetal growth, metabolism and endocrinology in late gestation. The underlying mechanisms remain uncertain, but fetal exposure to excess maternal glucocorticoids has been hypothesized. We investigated the effects of periconceptional undernutrition on maternal hypothalamic–pituitary–adrenal axis function and placental 11β‐hydroxysteroid dehydrogenase type 2 (11βHSD2) activity. Ewes received maintenance feed (N, n= 20) or decreased feed from −60 to +30 days from mating to achieve 15% weight loss after an initial 2‐day fast (UN, n= 21). Baseline plasma samples and arginine vasopressin (AVP)–corticotrophin‐releasing hormone (CRH) challenges were performed on days −61, −57, −29, −1, +29, 33, and 49 from mating (day 0). Maternal adrenal and placental tissue was collected at 50 days. Baseline plasma levels of adrenocorticotrophic hormone (ACTH) and cortisol decreased in the UN group (P < 0.0001). ACTH response to AVP–CRH was greater in UN ewes during undernutrition (P= 0.03) returning to normal levels after refeeding. Cortisol response to AVP–CRH was greater in UN ewes after the initial 2‐day fast, but thereafter decreased and was lower in UN ewes from mating until the end of the experiment (P= 0.007). ACTH receptor, StAR and p450c17 mRNA levels were down‐regulated in adrenal tissue from UN ewes. Placental 11βHSD2 activity was lower in UN than N ewes at 50 days (P= 0.014). Moderate periconceptional undernutrition results in decreased maternal plasma cortisol concentrations during undernutrition and after refeeding, and adrenal resistance to ACTH for at least 20 days after refeeding. Fetal exposure to excess maternal cortisol is unlikely during the period of undernutrition, but could occur later in gestation if maternal plasma cortisol levels return to normal while placental 11βHSD2 activity remains low.

Fetal signals and parturition

John R. G. Challis, Frank H. Bloomfield, Alan D. Bocking, Valentina Casciani, Hiroshi Chisaka, Kristin Connor, Xuesen Dong, Peter Gluckman, Jane E. Harding, Jim Johnstone, Wei Li, Stephen Lye, Kunihiro Okamura and Marina Premyslova Departments of Physiology, Medicine and Obstetrics and Gynecology, University of Toronto, CIHR Group in Fetal Development and Health Toronto, Canada; Liggins Institute, University of Auckland, New Zealand; Department of Obstetrics and Gynecology, Tohoku University, Sendai, Japan; and Program in Development and Fetal Health, Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Canada

Association between liver-specific gene polymorphisms and their expression levels with nonalcoholic fatty liver disease

Genetic factors account for a significant proportion of the phenotypic variance of nonalcoholic fatty liver disease (NAFLD); however, very few predisposing genes have been identified. We aimed to (1) identify novel genetic associations with NAFLD by performing a genome‐wide association study (GWAS), and (2) examine the biological expression of the strongest genetic associations in a separate cohort. We performed GWAS of a population‐based cohort (Raine Study) of 928 adolescents assessed for NAFLD by ultrasound at age 17. Expression of genes with single nucleotide polymorphisms (SNPs) that were associated with NAFLD at a significance level of P < 10−5 was examined in adults with NAFLD and controls by quantifying hepatic messenger RNA (mRNA) expression and serum levels of protein. After adjustment for sex and degree of adiposity, SNPs in two genes expressed in liver were associated with NAFLD adolescents: group‐specific component (GC) (odds ratio [OR], 2.54; P = 1.20 × 10−6) and lymphocyte cytosolic protein‐1 (LCP1) (OR, 3.29; P = 2.96 × 10−6). SNPs in two genes expressed in neurons were also associated with NAFLD: lipid phosphate phosphatase‐related protein type 4 (LPPR4) (OR, 2.30; P = 4.82 × 10−6) and solute carrier family 38 member 8 (SLC38A8) (OR, 3.14; P = 1.86 × 10−6). Hepatic GC mRNA was significantly reduced (by 83%) and LCP1 mRNA was increased (by 300%) in liver biopsy samples from patients with NAFLD compared to controls (P < 0.05). Mean serum levels of GC protein were significantly lower in patients with NAFLD than controls (250 ± 90 versus 298 ± 90, respectively; P = 0.004); GC protein levels decreased with increasing severity of hepatic steatosis (P < 0.01). Conclusion: The association between GC and LCP1 SNPs and NAFLD as well as altered biological expression implicate these genes in the pathogenesis of NAFLD. (HEPATOLOGY 2013;)

A Maternal high-fat diet in rat pregnancy reduces growth of the fetus and the placental junctional zone, but not placental labyrinth zone growth

Maternal obesity during pregnancy is often characterized by fetal macrosomia but it can also result in fetal growth restriction in a subset of pregnancies. We hypothesized that mechanisms of this growth restriction may include adverse effects of maternal high fat (HF) intake on placental growth and function. Female rats (100 days old) were time-mated and randomly assigned to either a control (Con) or HF diet ad libitum throughout gestation. At E21, dams were killed; litter size and fetal and placental weights were recorded and maternal and fetal samples collected for further analyses. The HF diet resulted in a 54% increase in maternal body weight gain during gestation. In contrast, male and female fetal weights were reduced in HF pregnancies (P ,0.05), as were the weights of the junctional zone of the placenta (P 50.013), whereas labyrinth zone weights were unaffected. The HF diet increased maternal and fetal plasma leptin levels (P ,0.05), but maternal and fetal insulin and fetal glucose levels were unaffected. Labyrinthine expression of PPARg and total VEGFa mRNA, both markers of placental vascular development, were unaffected by consumption of the HF diet in placentas of male and female fetuses. Furthermore, maternal HF nutrition did not alter phosphorylated protein levels of either mammalian target of rapamycin or its downstream signaling factor eIF4E binding protein 1 (4E-BP1). These data show that in the rat, maternal HF nutrition results in fetal and placental junctional zone growth restriction, maternal and fetal hyperleptinemia but did not alter gene expression of markers of placental vascular development. Received 8 February 2010; Revised 3 November 2010; Accepted 28 November 2010; First published online 7 January 2011

Do Alterations in Placental 11β-Hydroxysteroid Dehydrogenase (11βHSD) Activities Explain Differences in Fetal Hypothalamic-Pituitary-Adrenal (HPA) Function Following Periconceptional Undernutrition or Twinning in Sheep?

Periconceptional undernutrition (UN) in sheep accelerates fetal hypothalamic-pituitary-adrenal (HPA) axis activation, resulting in preterm birth. In contrast, twin conception suppresses fetal HPA function and delays prepartum HPA activation. We hypothesized that these dissimilar effects on fetal HPA activity result from different influences of maternal glucocorticoid (GC) on maturation of the fetal HPA axis, mediated via different activities of placental 11β-hydroxysteroid dehydrogenase (11βHSD) isozymes. We examined the effects of twinning and maternal periconceptional UN from 60 days before until 30 days after mating on the ontogeny of placental 11βHSD-1 and -2 enzyme activities. At day 85 of gestation, placental 11βHSD-2 activity was lower in UN than in normally nourished (N) fetuses (P < .05) and was higher in twins than in singletons (P < .05). Furthermore, placental 11βHSD-1 activity was not different between nutritional groups but was higher in twins than in singletons (P = .01). At day 85, fetal plasma cortisol (P < .001) and cortisone (P < .001) concentrations were lower in UN than in N fetuses, but the cortisol to cortisone ratio was higher in UN than in N fetuses (P = .01). There was no effect of fetus number on plasma cortisol or cortisone concentrations or on the ratio of cortisol to cortisone at day 85. Therefore, periconceptional UN and twinning may result in the alterations of placental 11βHSD isozyme activities at particular times during gestation. Changes in these activities during critical periods of fetal development could affect transplacental transfer or placental generation of GCs that reach the fetus, potentially influencing the timing of activation of the fetal HPA axis, fetal maturation, and hence the development and health later in life.

Pyridoxine 5′-phosphate oxidase is a novel therapeutic target and regulated by the TGF-β signalling pathway in epithelial ovarian cancer

Pyridoxine 5′-phosphate oxidase (PNPO) is an enzyme that converts pyridoxine 5′-phosphate into pyridoxal 5′-phosphate (PLP), an active form of vitamin B6 implicated in several types of cancer. However, the role of PNPO and its regulatory mechanism in epithelial ovarian cancer (EOC) are unknown. In the present study, PNPO expression in human ovarian tumour tissue and its association with the clinicopathological features of patients with EOC were examined. Further, the biological function of PNPO in EOC cells and in xenograft was evaluated. We demonstrated for the first time that PNPO was overexpressed in human EOC. Knockdown of PNPO induced EOC cell apoptosis, arrested cell cycle at G2/M phase, decreased cell proliferation, migration and invasion. Xenografts of PNPO-shRNA-expressing cells into the nude mouse attenuated tumour growth. PNPO at mRNA and protein levels in EOC cells was decreased after transforming growth factor-β1 (TGF-β1) treatment. The inhibitory effect of TGF-β1 on PNPO expression was abolished in the presence of SB-431542, a TGF-β type I receptor kinase inhibitor. Moreover, we found that TGF-β1-mediated PNPO expression was at least in part through the upregulation of miR-143-3p. These data indicate a mechanism underlying PNPO regulation by the TGF-β signalling pathway. Furthermore, PLP administration reduced PNPO expression and decreased EOC cell proliferation, suggesting a feedback loop between PLP and PNPO. Thus, our findings reveal that PNPO can serve as a novel tissue biomarker of EOC and may be a potential target for therapeutic intervention.