Abstract

Simple SummaryWe lack studies investigating mitochondrial metabolism in the prenatal and early postnatal period in humans, but parallel experiments conducted in a mammalian system are informative about the human condition. Our aim was to study the perinatal metabolic switch in rats—an extremely complex process, associated with tissue proliferation and differentiation together with a rapid oxidative stress response (using techniques including microarrays, qPCR, spectrophotometry and high-performance liquid chromatography). Out of 1546 mitochondrial genes, 1119 and 827 genes significantly changed expression in rat liver and skeletal muscle, respectively. The most remarkable expression shift occurred in the rat liver at least two days before birth. Coenzyme Q and mitochondrial metabolism-based evaluation in both the rat model and human tissues showed the same trend: the total CoQ content and mitochondrial metabolism significantly increases after birth, possibly regulated by COQ8A kinase. Our microarray data could serve as a suitable background for finding key factors regulating mitochondrial metabolism and preparation of the foetus for the transition to extra-uterine conditions, or as preliminary data for further studies of the complex mitochondrial metabolism regulation and diagnostics of mitochondrial disorders.At the end of the mammalian intra-uterine foetal development, a rapid switch from glycolytic to oxidative metabolism must proceed. Using microarray techniques, qPCR, enzyme activities and coenzyme Q content measurements, we describe perinatal mitochondrial metabolism acceleration in rat liver and skeletal muscle during the perinatal period and correlate the results with those in humans. Out of 1546 mitochondrial genes, we found significant changes in expression in 1119 and 827 genes in rat liver and skeletal muscle, respectively. The most remarkable expression shift occurred in the rat liver at least two days before birth. Coenzyme Q-based evaluation in both the rat model and human tissues showed the same trend: the total CoQ content is low prenatally, significantly increasing after birth in both the liver and skeletal muscle. We propose that an important regulator of rat coenzyme Q biosynthesis might be COQ8A, an atypical kinase involved in the biosynthesis of coenzyme Q. Our microarray data, a total of 16,557 RefSeq (Entrez) genes, have been deposited in NCBI’s Gene Expression Omnibus and are freely available to the broad scientific community. Our microarray data could serve as a suitable background for finding key factors regulating mitochondrial metabolism and the preparation of the foetus for the transition to extra-uterine conditions.

Highlights

  • Mitochondria are key players in mammalian ATP production

  • Our pilot study described the orchestration of Messenger RNA (mRNA) expression of 20 genes important to ATP synthase (ATPase) biogenesis and mitochondrial oxidative metabolism in the liver and muscle tissue during rat perinatal development (Rattus norvegicus Berkenhout, 1769, var. alba; Wistar albino rat) [33]

  • Together with using the data obtained in human foetuses, we decided to apply a broad RNA microarray analysis to find specific interconnections of transcriptional regulators or activators with an emphasis on Coenzyme Q (CoQ) biosynthesis. We believe that these data may enable the identification of further key factors regulating mitochondrial activation, and improve diagnostics of metabolic disorders and care in preterm newborns. The aim of this project was to study gene expression, with a validation of selected genes involved in CoQ biosynthetic process, during foetal and early postnatal physiological development of Rattus norvegicus, var. alba (Wistar albino rat) in the liver and the skeletal muscle tissue and to compare the results with those found in humans

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Summary

Introduction

Mitochondria are key players in mammalian ATP production. Oxidative phosphorylation, the mitochondrial process which produces the majority of cellular ATP, is executed by a system of several supercomplexes (OXPHOS) attached to the mitochondrial inner membrane. Regulation of ATP production is a complex process involving mitochondrial DNA (mtDNA) replication and transcription, the expression of OXPHOS subunits, biosynthesis of electron carriers (e.g., coenzyme Q, CoQ; cytochrome c), or even mitochondrial fission–fusion machinery regulation. The regulation of genes encoded both in nuclear DNA (nDNA) and mtDNA must be precisely orchestrated It has to be executed by a number of regulators. The concentration of ATP in the rat liver increases two-fold within the first two hours [4]. This metabolic switch has previously been reported in other tissues and organisms [5,6,7,8,9], encompassing changes in OXPHOS activities and mtDNA content as well. CoQ10 seems to play role in protecting the cell membranes and lipoproteins against lipid peroxidation in the antioxidant system of the plasma membrane, together with the NADH-cytochrome b5 and NADPH-cytochrome P450 reductases, and vitamins A, C and E [14,19,20,21]

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