Maternal Low-Protein Diet Affects Epigenetic Regulation of Hepatic Mitochondrial DNA Transcription in a Sex-Specific Manner in Newborn Piglets Associated with GR Binding to Its Promoter

Yimin Jia,Ruqian Zhao,Nahid Parvizi,Rihua Cong,Runsheng Li,Xiaojing Yang,Qinwei Sun,Claire Wade

doi:10.1371/journal.pone.0063855

Abstract

Mitochondrial oxidative phosphorylation (OXPHOS) plays an important role in energy homeostasis by controlling electron transfer and ATP generation. Maternal malnutrition during pregnancy affects mitochondrial (mt) DNA-encoded OXPHOS activity in offspring, yet it is unknown whether epigenetic mechanism is involved in the transcriptional regulation of mtDNA-encoded OXPHOS genes. In this study, 14 primiparous purebred Meishan sows were fed either standard- (SP, 12% crude protein) or low-protein (LP; 6% crude protein) diets throughout gestation, and the hepatic expression and transcriptional regulation of mtDNA-encoded OXPHOS genes were analyzed in newborn piglets. Maternal low protein diet decreased hepatic mtDNA copy number in males, but not in females. LP male piglets had significantly higher hepatic AMP concentration and low energy charge, which was accompanied by enhanced mRNA expression of NADH dehydrogenase subunits 6, cytochrome c oxidase subunit 1, 2, 3 and cytochrome b, as well as increased cytochrome c oxidase enzyme activity. In contrast, LP female piglets showed significantly lower hepatic AMP concentrations and higher energy charge with no alterations in OXPHOS gene expression. Moreover, LP males demonstrated higher glucocorticoid receptor (GR) binding to the mtDNA promoter compared with SP males, which was accompanied by lower cytosine methylation and hydroxymethylation on mtDNA promoter. Interestingly, opposite changes were seen in females, which showed diminished GR binding and enriched cytosine methylation and hydroxymethylation on mtDNA promoter. These results suggest that maternal low protein diet during pregnancy causes sex-dependent epigenetic alterations in mtDNA-encoded OXPHOS gene expression, possibly GR is involved in mtDNA transcription regulation.

Highlights

Mitochondria play an important role in maintaining energy homeostasis by balancing ATP generation and expenditure at the cellular level
Deregulation of energy homeostasis is a common feature of metabolic syndrome and a number of studies have shown that maternal nutrition programs offspring mitochondria oxidative phosphorylation (OXPHOS) activity in various types of tissues, including liver [10], pancreatic islet [11] and skeletal muscle in rats [12], kidney [13] and skeletal muscle [14] in sheep, as well as liver in pig [15]
Maternal low protein diet throughout pregnancy resulted in IUGR which is indicated by significantly lower birth weight and liver weight in LP offspring

Summary

Introduction

Mitochondria play an important role in maintaining energy homeostasis by balancing ATP generation and expenditure at the cellular level. Mitochondrial dysfunction in various tissues, such as skeletal muscle [1], liver [2] and fat [3], has been associated with metabolic diseases in human and animal models. It is considered that decreased mitochondrial OXPHOS activity is related to metabolic perturbation in diabetes human [4] and mice [5]. Deregulation of energy homeostasis is a common feature of metabolic syndrome and a number of studies have shown that maternal nutrition programs offspring mitochondria OXPHOS activity in various types of tissues, including liver [10], pancreatic islet [11] and skeletal muscle in rats [12], kidney [13] and skeletal muscle [14] in sheep, as well as liver in pig [15]

Methods

Results

Conclusion