Epigenetics - Milk modifies Gene Expression
Epigenetics – definition – the study of changes in organisms caused by modification of gene expression rather than alteration of the genetic code itself.
Epigenetic Effects of Human Breast Milk
1.1. Beneficial Effects of Human Breast Milk
Breastfeeding and human milk are the normative standards for infant feeding and nutrition. Short-and long-term benefits of breastfeeding on health are documented [1,2]. Breastfeeding has been associated with a reduction in the incidence of gastrointestinal tract infections, respiratory tract infections, and otitis media [1,2].
The relationship of human milk feeding with a significant reduction in the incidence of necrotizing enterocolitis (NEC) has been suggested in preterm infants . Protective effects are shown also in autoimmune disorders (celiac disease, type-1 diabetes) and inflammatory bowel disease [1,2]. Additionally there is extensive evidence that individuals who had been breast-fed or received human milk show lower risk of some non-communicable diseases in later life [1,2]. Indeed breastfeeding has been associated with lower risk of obesity, lower levels of arterial blood pressure, lower total-and LDL-blood cholesterol levels in adulthood, and lower risk of developing type-2 diabetes [1,2]. Furthermore consistent differences in neurodevelopmental outcome between breastfed and formula fed infants have been reported [1,2]. Evidence about the association between neurodevelopment and exclusive breastfeeding was provided by the cluster-randomized Promotion of Breastfeeding Intervention Trial (PROBIT) study . Adjusted outcomes of intelligence scores were significantly greater in exclusively breastfed for three months or longer.”
“1.2. Nutritional Epigenetics
If evidence suggests that genome may be able to influence the nutrition , nutrients may be able to regulate gene expression . Genes and nutrition seem, therefore, to be in mutual relationship. The term epigenetics literally means on top of genetics and refers to processes that induce heritable changes in gene expression without altering the gene sequence . Epigenetic processes are integral in determining when and where specific genes are expressed. Alterations in the epigenetic regulation of genes may lead to profound changes in phenotype. The major epigenetic processes are DNA methylation, histone modification, chromatin remodeling and microRNAs, although it is still debated if miRNA may be considered as an epigenetic phenomenon. To date, most studies on the effect of early-life nutrition on the epigenetic regulation of genes have focused on DNA methylation [15,16,17,18]. Methylation of the 5′ position of a cytosine within the genome occurs by the enzymatic family of DNA methyltransferases forming 5-methylcytosine (5-mC), that is present in an estimated 4%–6% of the cytosine bases within a human genome. Most of DNA methylation occurs within CpG dinucleotides, although methylation outside of the CpG context has been reported in human DNA in recent years . The human genome contains about 30 million CpG dinucleotides that exist in a methylated or unmethylated state. Dense repeats of CpG nucleotides are called CpG islands and occur throughout the genome. Methylation of CpG islands located in the promoter region of a gene is usually inversely associated with transcription of that gene due to binding of methyl-CpG binding proteins, which recruit proteins to the promoter of the gene, thereby blocking transcription. Therefore, epigenetics, that is the inter-individual variation in DNA methylation patterns and chromatin remodeling, provide a potential explanation for how environmental factors (e.g., bioactive food components, nutrients, specific diets) can modify the risk for development of many common diseases [16,17]. Age, genetics, and environment may together interact to affect epigenetic regulation. The epigenetics determinants may interfere at any time during the life of the individual . Several studies have shown that the environment and nutrition, at an early stage or at critical periods of development, may influence the expression of genes with short- and long-term effects on the organism [15,16,17].”