Gene-diet interaction in mice supplemented with methionine in the fetal and postnatal periods: studies of genomic instability, methylation and expression of genes related to cardiovascular diseases

Author(s)

Alexandre Ferro Aissa

• Document type: Doctoral Thesis
• Press: Ribeirão Preto.
• Institution: Universidade de São Paulo (USP). Faculdade de Medicina de Ribeirão Preto (PCARP/BC)
• Defense date: 2014-04-16

Examining board members

Lusania Maria Greggi Antunes; Ilce Mara de Syllos Colus; Elza Tiemi Sakamoto Hojo; André Salim Khayat; Tiago Campos Pereira

• Advisor: Lusania Maria Greggi Antunes

Abstract

Methionine obtained from the diet is the major donor of methyl groups for DNA methylation. Methylation occurs predominantly in CpG dinucleotides, primarily distributed in regions called CpG islands, which are typically found in the promoter regions of genes participating in the regulation of gene transcription. During the reproductive process, the mammalian genome undergoes a profound reprogramming of methylation patterns in germ cells and early pre-implantation embryo events. Problems in methylation mechanisms during the embryonic period may induce the onset of diseases throughout the life of the individual. It is also known that problems in DNA methylation influence the expression of genes related to cardiovascular diseases. This study assessed the effects of methionine concentration in the diet on genomic instability, methylation, and the mRNA expression of genes related to cardiovascular diseases. We fed three groups of randomly allocated female Swiss albino mice a control (methionine-adequate) diet and two experimental (methionine-deficient or methionine-supplemented) diets for 10 weeks during their pre-mating, pregnancy, and lactation. ln their offspring, nutritional intervention was initiated 21 days after birth, after weaning, and lasted for 18 weeks. The results showed that there was increased chromosomal instability in females fed the supplemented diet, while in their offspring, only the diet deficient in methionine increased chromosomal instability. The primary DNA damage was measured by the comet assay in the tissues of females, and was found to be induced in a tissue-specific manner, indicating that the supplemented diet was genotoxic in peripheral blood but not in the liver. This effect was not triggered by the activity of DNA repair genes, as there was no increase in the expression of mismatch repair genes in the liver. ln the females, both diets induced an increase of oxidative stress in the liver, with a stronger effect induced by the methionine deficient diet. This event was followed by changes in the expression of genes related to cardiovascular disease in the liver and heart, with the diets having a profound effect on lipid accumulation in the liver, although changes in the expression of genes and proteins related to lipid transport and metabolism were mainly induced by the methionine deficient diet. Both diets increased the concentrations of inflammatory cytokines in the liver, although greater changes were induced by the methionine deficient diet. Both diets increased hepatic global DNA methylation. Both diets altered the expression of 28 microRNAs that target genes involved in the metabolism of macromolecules, regulation of metabolic processes and morphogenesis of anatomical structures. Both diets, both in females and in their offspring, reduced the methylation of the CpG island located in the intragenic region of the Apoa5 gene, and this change seems to be correlated with a reduction in the expression of Apoa5. The diets of mothers influenced the phenotypes of their offspring, through changes in the methylation of the promoter and intragenic regions of the genes studied, as well as through changes in the expression of the gene. (AU)

• FAPESP's process: 10/01410-0 - Gene-diet interaction in mice supplemented with methionine in the fetal and postnatal periods: studies of genomic instability, methylation and expression of genes related to cardiovascular diseases
• Grantee: Alexandre Ferro Aissa
• Support Opportunities: Scholarships in Brazil - Doctorate