Reprod Fertil Dev. 2017 Sep;29(10):1995-2004. doi: 10.1071/RD16276.

Epigenetic changes of hepatic glucocorticoid receptor in sheep male offspring undernourished in utero.

Chadio S, Kotsampasi B, Taka S, Liandris E, Papadopoulos N, Plakokefalos E.

Corresponding Author: Stella Chadio. Department of Anatomy and Physiology of Domestic Animals, Faculty of Animal Science and Aquaculture, Agricultural University of Athens, 75 Iera Odos, 11855, Athens, Greece, E-mail: shad@aua.gr

 

Abstract

BACKGROUND: Experimental and epidemiological data indicate that nutrient restriction during specific developmental windows may affect liver development and glucose –insulin homeostasis in later life due to programming effects.

The aim of our study was to characterize the effects of maternal undernutrition, during two different gestational periods on hepatic gluconeogenic enzyme gene expression and to determine whether such effects are mediated through epigenetic changes in the glucocorticoid receptor (GR), in a large animal model of developmental programming. METHODS: Pregnant ewes were fed a 50% nutrient-restricted diet from Day 0 to 30 (R1) or from Day 31 to 100 of gestation (R2) or a 100% diet throughout gestation (Control). After parturition lambs were fed to appetite. At 10 months of age, offspring were euthanized. Methylation status of the GR gene promoter and gluconeogenic enzyme gene expression were analyzed in the liver of the offspring. RESULTS: Maternal undernutrition did not affect offspring body weight at birth or at 10 months of age, but reduced liver weight was detected in males of the R2, compared to other two groups. A significant hypomethylation of the hepatic GR gene promoter was revealed in males of the R2 group and a tendency towards the same in the R1 group, together with increased GR gene expression in both restricted groups. In male offspring of both undernourished groups an increase in PEPCK gene expression was detected, accompanied by increased protein levels, while no differences were observed for glucose-6-phosphatase (G6Pase) expression and protein levels. Female offspring showed no difference between groups for any parameter studied. CONCLUSION: Nutrient restriction during fetal life have long term, sex specific effects on the expression of liver enzymes involved in gluconeogenesis, mediated probably by the glucocorticoid receptor (GR). These data represent potential mechanisms by which nutritional disturbances in early life may lead to persistent metabolic changes in the offspring.

PMID: 28076749

 

Supplement:

Accumulating evidence support an association between early life events and the subsequent development of adult metabolic disorders. In this context, the “developmental origins of health and disease” (DOHaD) hypothesis implies that a stimulus or insult acting during a sensitive period of uterine life lead to permanent adaptations in fetal homeostatic mechanisms, producing long-term changes in physiology and determine susceptibility to later disease (Barker 2007). Variation in the nutrient supply during fetal life and especially maternal undernutrition has been highlighted, as a dominant cause of programming.

Epidemiological studies in humans and experimental studies in animals have revealed that disturbances in the glucose-insulin homeostasis and type 2 diabetes could originate from in utero malnutrition, especially in association with maladaptation to a postnatal environment providing plentiful nutrition (McMillen and Robinson 2005).

Excessive hepatic glucose production has been recognized as an important contributing factor to Type 2 diabetes. The rate of gluconeogenesis is mainly determined by the key gluconeogenic enzymes, phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G6Pase), which are tightly controlled by glucocorticoids (GCs), whose effects are mediated by the glucocorticoid receptor (GR) acting as a transcription factor.

Altered glucocorticoid activity has been implicated in the prenatal programming of glucose intolerance after prenatal substrate restriction (Nyirenda et al. 1998). Glucocorticoid hormone action within the cell is regulated by expression of the glucocorticoid receptor (GR) at the level of gene transcription. The activated GR acts as a transcription factor and controls the level of expression of target genes, but also modulates intracellular signaling pathways (Klein-Hitpass et al. 1998). Molecular mechanisms underlying the effects of glucocorticoids probably include epigenetic changes in target gene promoters, including the GR (Harris and Seckl 2011), thus persistently affecting glucocorticoid signaling in certain tissues.

To address these hypotheses we examined the extent of methylation of the GR gene promoter in the liver of sheep offspring derived from mothers fed a 50% nutrient-restricted diet from Day 0 to 30 (R1) or from Day 31 to 100 of gestation (R2) or a 100% diet throughout gestation (Control) and its association with the expression of the gluconeogenic enzymes.

Methylation analysis of the GR gene promoter revealed a significant (P<0.05) hypomethylation, accompanied by increased (P<0.001) GR expression in males of the R2 group and a trend towards decreased methylation, together with increased (P<0.001) GR expression in the R1 group (Fig. 1a, b). No differences were observed for female lambs between groups.

Consistent with sex specific changes in GR expression, we also observed increased (P<0.05) expression, accompanied by elevated (P<0.01) protein levels of the gluconeogenic enzyme PEPCK in the liver of male offspring of both undernourished groups. (Fig. 1c, d). No differences for G6Pase gene expression and protein levels were detected between groups

A role for glucocorticoids in mediating the effects of undernutrition on hepatic gene expression is strongly supported by our data, as the increased GR mRNA abundance detected in the present study indicates augmented cortisol signaling in response to maternal feed restriction. The resulted up-regulation of the PEPCK expression and activity mediated through GR activation may be an important contributor factor to the induction of insulin resistance.

A gender-specific effect was detected in the present study, both for liver weight and hepatic gene expression in male offspring of both nutrient restricted groups, consistent with the concept that prenatal programming is largely characterized by sex-specific effects. These findings may explain sexual dimorphism in programming of the susceptibility to metabolic diseases.

In conclusion, maternal undernutrition alters the epigenetic and expression status of the glucocorticoid receptor in the liver of offspring in later life. These alterations are accompanied by changes in the expression of enzymes involved in liver gluconeogenesis, providing a potential mechanism by which nutritional disturbances in early life may lead to persistent metabolic changes in the offspring.

 

 

References

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Nyirenda, M. J., Lindsay, R. S., Kenyon, C. J., Burchell, A., and Seckl, J. R.(1998). Glucocorticoid exposure in late gestation permanently programs rat hepatic phosphoenolpyruvate carboxykinase and glucocorticoid receptor expression and causes glucose intolerance in adult offspring. J. Clin. Invest. 101, 2174–2181. doi:10.1172/JCI1567

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