Implications of oxidative stress and homocysteine in the pathophysiology of essential hypertension

Genetics of essential hypertension

PURPOSE

To inform healthcare providers of the genetics involved in the development of essential hypertension and to illustrate the role the healthcare provider has in the management of patients with essential hypertension.

DATA SOURCES

Research-based articles in the medical literature, selected published literature in refereed journals, and Internet sites.

CONCLUSIONS

Essential hypertension is a complex chronic disease that affects many people and has grave implications for the patient. Genetics involved in the development of essential hypertension and treatment choices is evolving; therefore, the healthcare provider must be knowledgeable in these areas to effectively care for patients with hypertension.

IMPLICATIONS FOR PRACTICE

Essential hypertension is a chronic disease that affects over 50 million people in the United States. Advances in genetics are allowing scientists to discover the genetic basis of hypertension. With knowledge of genetics and environmental factors involved in the development of essential hypertension, healthcare providers will be able to more effectively screen, manage, and treat individuals with hypertension.

Homocysteine and cognitive function in a population-based study of older adults

OBJECTIVES

To assess the relations between homocysteine levels and neurobehavioral test scores representing a broad range of cognitive domains in a population-based study of older adults.

DESIGN

Cross-sectional analysis of first-visit data of subjects in the Baltimore Memory Study, a longitudinal study.

SETTING

Specific neighborhoods in Baltimore.

PARTICIPANTS

Participants were 1,140 randomly selected residents aged 50 to 70 with a mean age+/-standard deviation of 59.3+/-5.9; 65.9% were female, and 54.2% were white and 41.1% African-American.

MEASUREMENTS

Twenty neurobehavioral test scores in eight cognitive domains.

RESULTS

Linear regression models revealed that homocysteine was consistently and strongly associated with worse neurobehavioral test performance, in crude analysis and after control for a large set of important covariates. Associations were observed in all eight cognitive domains assessed but were strongest and most consistent in the domains of simple motor and psychomotor speed, eye-hand coordination/manual dexterity, and verbal memory and learning. On average, an increase in homocysteine levels from the 25th to the 75th percentile, all in the generally accepted normal range, was equivalent in its association with neurobehavioral test scores to an increase of 4.2 years of age. Logistic regression models revealed that, on average, for the neurobehavioral tests associated with homocysteine, subjects in the highest quartile of homocysteine levels were more than two times as likely to be in the lowest quartile of neurobehavioral test scores as those in the lowest quartile.

CONCLUSION

Higher homocysteine levels were associated with worse function across a broad range of cognitive domains, and the magnitude of the associations was large. The data suggest that homocysteine may be a potentially important modifiable cause of cognitive dysfunction.

Blood lead is a predictor of homocysteine levels in a population-based study of older adults

Lead and homocysteine are both associated with cardiovascular disease and cognitive dysfunction. We evaluated the relations among blood lead, tibia lead, and homocysteine levels by cross-sectional analysis of data among subjects in the Baltimore Memory Study, a longitudinal study of 1,140 randomly selected residents in Baltimore, Maryland, who were 50-70 years of age. Tibia lead was measured by (superscript)109(/superscript)Cd K-shell X-ray fluorescence. The subject population had a mean +/- SD age of 59.3 +/- 5.9 years and was 66.0% female, 53.9% white, and 41.4% black or African American. Mean +/- SD blood lead, tibia lead, and homocysteine levels were 3.5 +/- 2.4 microg/dL, 18.9 +/- 12.5 microg/g, and 10.0 +/- 4.1 micromol/L, respectively. In unadjusted analysis, blood lead and homocysteine were moderately correlated (Pearson's r = 0.27, p < 0.01). After adjustment for age, sex, race/ethnicity, educational level, tobacco and alcohol consumption, and body mass index using multiple linear regression, results revealed that homocysteine levels increased 0.35 micromol/L per 1.0 microg/dL increase in blood lead (p < 0.01). The relations of blood lead with homocysteine levels did not differ in subgroups distinguished by age, sex, or race/ethnicity. Tibia lead was modestly correlated with blood lead (Pearson's r = 0.12, p < 0.01) but was not associated with homocysteine levels. To our knowledge, these are the first data to reveal an association between blood lead and homocysteine. These results suggest that homocysteine could be a mechanism that underlies the effects of lead on the cardiovascular and central nervous systems, possibly offering new targets for intervention to prevent the long-term consequences of lead exposure.

Modulation of the Inflammatory Response in Cardiovascular Disease

There is a growing body of evidence that inflammation might play an important role in the initiation and progression of cardiovascular diseases (CVDs). The designation of CVD as a chronic inflammatory process is further supported by evidence that the risk factors for CVD cause endothelial cells throughout the vascular tree to assume an inflammatory phenotype. These activated endothelial cells characteristically exhibit oxidative stress and increased adhesiveness for circulating leukocytes. Although initial efforts to define the mechanisms underlying the inflammatory phenotype in diseased endothelial cells have focused on the linkage between oxidative stress and adhesion molecule activation/expression, recent work has implicated a variety of additional factors that can modulate the magnitude and/or nature of the inflammatory responses in CVD. Platelets, angiotensin II, and the CD40/CD40 ligand signaling system are gaining recognition as contributors to the pathogenesis of CVD. These factors appear to converge with known pathways that link oxidative stress with adhesion molecule expression and help to explain the apparent integration of coagulation with inflammation in CVD. These factors also hold the promise of offering multiple sites for therapeutic intervention in CVD.