Maternal dietary betaine supplementation modifies hepatic expression of cholesterol metabolic genes via epigenetic mechanisms in newborn piglets

AbstractToelucidatetheeffectsofmaternaldietarybetainesupplementationonhepaticexpressionofcholesterolmetabolicgenesinnewbornpigletsand the involved epigenetic mechanisms, we fed gestational sows with control or betaine-supplemented diets (3g/kg) throughout preg-nancy. Neonatal piglets born to betaine-supplemented sows had higher serum methionine concentration and hepatic content of betaine,whichwasassociatedwithsignificantlyup-regulatedhepaticexpressionofglycineN-methyltransferase.Prenatalbetaineexposureincreasedhepaticcholesterolcontentandmodifiedthehepaticexpressionofcholesterolmetabolicgenesinneonatalpiglets.Sterolregulatoryelement-binding protein 2 was down-regulated at both mRNA and protein levels, while 3-hydroxy-3-methylglutaryl CoA reductase (HMGCR) wasdown-regulated at the mRNA level, but up-regulated at the protein level, in betaine-exposed piglets. The transcriptional repression ofHMGCR was associated with CpG island hypermethylation and higher repressive histone mark H3K27me3 (histone H3 lysine 27 trimethy-lation) on the promoter, whereas increased HMGCR protein content was associated with significantly decreased expression of miR-497.Furthermore, LDL receptor was significantly down-regulated at both mRNA and protein levels in the liver of betaine-exposed piglets,which was associated with promoter CpG hypermethylation. In addition, the expression of cholesterol-27a-hydroxylase (CYP27a1) wasup-regulated at both mRNA and protein levels, while the expression of cholesterol-7a-hydroxylase (CYP7a1) was increased at the mRNAlevel, but unchanged at the protein level associated with increased expression of miR-181. These results indicate that maternal betainesupplementation increases hepatic cholesterol content in neonatal piglets through epigenetic regulations of cholesterol metabolic genes,which involve alterations in DNA and histone methylation and in the expression of microRNA targeting these genes.Key words: Betaine: Epigenetic regulation: Cholesterol metabolism: Maternal diet: Piglets