Iris Publishers- Open access Journal of Neurology & Neuroscience | A New Approach in the Study of Hypertension in the Elderly Subject: The Role of Epigenetics

 

 

Authored by Valerio Massimo Magro

The causes of high blood pressure are numerous and are based on the important distinction between the various types of arterial hypertension, which sees the existence of so-called essential hypertension and the so-called secondary hypertension. The elderly, considered as individuals 75 years of age and older, with essential hypertension, represent a conspicuous percentage of subjects suffering from diseases in the general population. Essential hypertension is the hypertensive state whose presence is imputed to a multiplicity of predisposing factors, since it is impossible to establish with certainty a precise and univocal triggering cause. Age itself is a powerful risk factor for hypertension. Although it has never been set aside, the emphasis has recently been placed on the role played by genetics in the genesis of hypertension. Furthermore, the discovery that changes in the functioning of a gene do not derive only from mutations in the nucleotide sequence but also that changes in the conformation of chromatin and modifications of the subsequent phases of gene expression, from the transcription of mRNA onwards, led to consider the role played by the genetic heritage in the determinism of this pathology under a new aspect.

Epigenetics is considered to be that series of dynamic and reversible modifications, generated and removed by enzymes, of our genetic heritage. There are therefore changes in gene activity that do not involve changes in the DNA sequence and that are also inheritable. The structure of the chromosome is the nucleosome, that is a formation of structural proteins of the chromosome itself, the histones, which, in number of eight, form a complex. The DNA helix surrounds around the complex. In fact the chromatin is present in the cell nucleus in different degrees of compaction. There is a condensed chromatin (heterochromatin), which is transcriptionally silent, because the DNA is not accessible. The histone tails protrude from the nucleosome and they participate in the compaction of the chromatin. There are enzymes that modify histones or DNA itself through acetylation or methylation. For example, in case of histone acetylation, the nucleosome remodels, the chromatin is decondensed and the transcription is activated; another type of enzyme performs a deacetylation action on the tail of the histones: the chromatin is recondensed and the transcription is repressed.

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