How do genetic and environmental factors affect blood pressure?
Systemic hypertension has a worldwide prevalence of approximately 25% to 30%. It is a key risk factor for heart disease, stroke, and kidney disease.
Blood pressure correlations within families indicate that approximately 20% to 40% of the variation in both systolic and diastolic blood pressure is caused by genetic factors.
This figure is substantially less than 100% and indicates that environmental factors also must be important causes of blood pressure variation.
Important environmental risk factors for hypertension are:
Increased sodium intake
Decreased physical activity
Psychosocial stress
Obesity (the latter factor is itself influenced by both genes and environment)
Blood pressure regulation is a highly complex process that is influenced by many physiologic systems, including various aspects of kidney function, cellular ion transport, and heart function. Due to this complexity, research is now focused on specific components that influence blood pressure variation. Examples include:
The renin-angiotensin system (involved in sodium reabsorption and vasoconstriction)
Vasodilators such as nitric oxide and the kallikrein-kinin system
Ion-transport systems such as adducin and sodium-lithium counter-transport (Fig. 5.7)
Fig. 5.7
Renin-Angiotensin-Aldosterone System.
(Adapted from Khera AV, Chaffin M, Aragam KG, et al., 2018. Nature genetics in Jorde LB, Carey JC, Bamshad MJ.
Medical genetics
, 6th edition. Philadelphia: Elsevier; 2020).
These individual factors are more likely to be under the control of smaller numbers of genes than is blood pressure itself.
This simplifies the task of identifying these genes and their role in blood pressure regulation.
For example, linkage and association studies have implicated several genes involved in the renin-angiotensin system (e.g., the genes that encode angiotensinogen, angiotensin-converting enzyme, angiotensin receptors) in the causation of hypertension.
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