View source for 17. Genomics and epigenetics in public health. Nutrigenomics

* Most diseases with a genetic component can not be traced back to a single gene but rather multiple
** Exceptions: Cystic fibrosis, Huntington disease
* Genomics = the interactions of all genes and their combined influence on the organism
** Genetics = the study of heredity. The effect of single gene mutations on the organism
* Genomics in public health – Using genome-based discoveries for health benefits of the population
* Genomics are important in
** Determining why exposure only causes the disease in some people
** Determining why prognostic factors have different importance in different people
** Determining why treatment only works in some people
* How to start:
** Candidate gene studies
*** A gene is suspected for having a role in disease
*** Identify differences in one gene in patients and controls
** Genome-wide association studies
*** No prior gene candidate is needed
*** Identify genetic differences in the whole genome of patients and controls
*** Can find alleles of a gene which increases susceptibility
* Personalized medicine
** Use genetic testing to find screening, treatment, and other preventative measures that are best suited for the patient
** Will prevent overdiagnosis and overtreatment
** Examples
*** Genetic information of nicotine metabolism can be used to personalize smoking cessation
*** Genetic information can give indication for screening, if high-risk genotypes are present
*** Genetic information can tell us upfront which treatments will be most effective

Epigenetics

* Definition: Instructions for the cell on how and when to read DNA
* Epigenetics changes gene expression
* Genetically identical organisms can have different phenotype due to different epigenetics
* Types
** Acetylation of histones
** Methylation of DNA
** Presence of miRNA
** Chromatin remodelling
* Environmental factors can change epigenetics of an individual, and therefore the expression of the DNA
* Folic acid necessary for DNA methylation -> deficiency could theoretically cause hypomethylation and carcinogenesis
* MicroRNA profiles in blood could be used as biomarkers
** Already used for CRC
* Drugs affecting epigenetics = epigenetic drugs
** Used as chemotherapeutic agents against cancer
** Epigenetic alterations are reversible and can be reversed by these drugs
*** Unlike genetic mutations
** They demethylate DNA or acetylate histones
*** This can reactivate silenced tumor suppressors, repress activated oncogenes, etc.

Nutrigenomics

* Definition: The relationship between nutrition and genomics
** Basically how what you eat can change epigenetics
* Deficiency of certain nutrients (folate, B12, C, E) can cause DNA changes similar to those seen after radiation
* Folate
** Folate is required for DNA methylation
** Folate deficiency -> DNA hypomethylation -> carcinogenesis
* Methyl-donating nutrients
** Diets high in methyl-donating nutrients can alter gene expression
** Especially during early development
** Examples
*** Methionine
*** Folate
*** B12
* Maternal nutrition
** Maternal nutritional status during early pregnancy can cause permanent epigenetic changes in the foetus

[[Category:Public health 4 - Preventive medicine]]