Cerebral white matter lesions in essential hypertension

Differential Impact of Plasma Homocysteine Levels on the Periventricular and Subcortical White Matter Hyperintensities on the Brain

Background: The clinical significance of cerebral white matter hyperintensities (WMH) on brain magnetic resonance imaging (MRI) has recently increased, and recognized now as a risk factor for future stroke and dementia. High levels of plasma homocysteine (Hcyt) are associated with cerebral WMH. Recent studies suggest a different anatomy and physiology in the arteriolar system may be supplied to the periventricular and deep subcortical white matter. We hypothesize that plasma Hcyt levels have differing impacts on periventricular WMH (PVWMH) than on deep subcortical WMH (DSWMH).

Methods: We evaluated plasma Hcyt levels from 937 neurologically healthy participants. The severity of PVWMH and DSWMH was evaluated by the use of a manual grading scale. Moderate to severe PVWMH and DSWMH levels were defined when the Fazekas score was two or three, respectively. Predominant PVWMH (pred-PVWMH) and predominant DSWMH (pred-DSWMH) were defined as having a difference of Fazekas score between PVWMH and DSWMH of two or more. Other confounding variables including age, sex, vascular risk factors, and estimated glomerular filtration rate (eGFR) were also analyzed.

Results: Logistic regression revealed that, after adjusting for the confounding variables, PVWMH was associated with old age, hypertension, diabetes mellitus, low eGFR, and high plasma Hcyt levels. DSWMH was associated with old age, hypertension, and hypercholesterolemia but not with plasma Hcyt levels. Plasma Hcyt levels were associated with pred-PVWMH but not with pred-DSWMH.

Conclusions: High plasma Hcyt levels are strongly associated with the development of PVWMH but not DSWMH. Our results suggest the possibility that different pathogeneses exist for PVWMH and DSWMH and that dysregulated Hcyt metabolism associated with the development of PVWMH.

Role of the prefrontal lobe in young normotensives with a family history of hypertension and hypertensives

Accumulating evidence has demonstrated a significant relationship between prefrontal lobe and hypertension. Elevated blood pressure is usually associated with a prefrontal hemodynamic abnormality. However, the detailed process is still unclear. In this study, we designed a startle protocol and tested the response of the cerebral cortex and cardiovascular system in young normotensive subjects with a family history of hypertension (FH+). Additionally, the cold forehead test (CFT) was performed in hypertensive subjects. In total, 40 young normotensive subjects (21 with FH+ and 19 without a family history of hypertension (FH-)) and 49 middle-aged subjects (21 normotensives (NT) and 28 hypertensives (HT)) were recruited. Our results showed that the magnitude of startle-evoked alpha oscillation at the parasympathetic-related prefrontal cortex (FP1 and FP2) in the FH+ group was significantly smaller than in the FH- group. Acute bradycardia (RRI increase) was observed in FH- subjects but disappeared in the FH+ group. The coupling between instant cardiac acute response (increased RRI) and prefrontal arousal (magnitude of evoked oscillation) was significantly weakened in the FH+ group compared with the FH- group. Furthermore, the decrease in HR induced by parasympathetic outflow during CFT was absent in HT subjects. Hence, we concluded that the impairment of parasympathetic outflow derived from the prefrontal lobe occurs in both healthy young offspring of hypertensive and hypertensive patients.

Endothelial function, adipokine serum levels and white matter hyperintesities in subjects with diabetic foot syndrome

CONTEXT

No study analysed the prevalence of white matter hyperintesities (WMHs) in subjects with diabetic foot syndrome (DFS) and their relationship with adipokine serum levels and indexes of endothelial and cognitive performance.

OBJECTIVE

To evaluate omentin and vaspin serum levels and WMHs prevalence in subjects with DFS and to analyse their relationship with other endothelial, arterial stiffness and cognitive function.

RESEARCH DESIGN AND METHODS

Case-control study enrolling 40 subjects with DFS, 40 diabetic subjects without foot complications, 40 controls with foot lesions without diabetes and 40 patients without diabetes mellitus.

MAIN OUTCOME MEASURE

Pulse wave velocity (PWV), augmentation index (Aix), Reactive hyperemia index (RHI), serum vaspin and omentin levels, Fazekas Score, MMSE.

RESULTS

Subjects with DFS showed higher mean PWV values if compared with diabetic controls, lower RHI values if compared with controls. They also showed a lower mean MMSE score, significantly lower omentin serum levels, a higher prevalence of grade 2 severity of periventricular hyperintensities (PVH). We observed a significant positive correlation between PWV and PVH, between Fazekas Score and PWV among diabetic subjects, whereas among subjects with diabetic foot we observed a significant negative correlation between PVH and RHI.

CONCLUSIONS

Diabetes seems to be more associated with endothelial function disturbance in comparison with patients with diabetic foot that exhibit a more strict association with microvascular brain damage as indicated by our significant finding of an association with periventricular hyperintensities.

Left ventricular geometry and white matter lesions in ischemic stroke patients

Abnormal left ventricular (LV) geometry is associated with extracardiac organ damage in patients with hypertension. The aim of this study was to determine the relationship between LV geometry and white matter lesions (WMLs) in ischemic stroke patients. We retrospectively analyzed data from 155 patients (median age 62; 49.8% male) with mild ischemic stroke (median National Institutes of Health Stroke Scale score 4) who underwent brain magnetic resonance imaging and echocardiography. Patients were categorized into four groups: normal LV geometry, concentric remodeling, eccentric left ventricular hypertrophy (LVH) and concentric LVH. WMLs were graded using the Fazekas scale on fluid-attenuated inversion recovery images. Extensive WMLs were defined as a Fazekas score > 2. Extensive WMLs were more prevalent in patients with concentric LVH, eccentric LVH and concentric remodeling than in those with normal LV geometry. After adjusting for hypertension, age, diabetes mellitus, hypercholesterolemia, glomerular filtration rate and ischemic heart disease, patients with concentric remodeling [odds ratio (OR) 3.94, 95% confidence interval (CI) 1.26-12.31, p = 0.02] and those with concentric LVH (OR 3.69, 95% CI 1.24-10.95, p = 0.02), but not patients with eccentric LVH (OR 2.44, 95% CI 0.72-8.29, p = 0.15), had higher risk of extensive WMLs than patients with normal LV geometry.

Age-related white matter changes

Age-related white matter changes (WMC) are considered manifestation of arteriolosclerotic small vessel disease and are related to age and vascular risk factors. Most recent studies have shown that WMC are associated with a host of poor outcomes, including cognitive impairment, dementia, urinary incontinence, gait disturbances, depression, and increased risk of stroke and death. Although the clinical relevance of WMC has been extensively studied, to date, only very few clinical trials have evaluated potential symptomatic or preventive treatments for WMC. In this paper, we reviewed the current understanding in the pathophysiology, epidemiology, clinical importance, chemical biomarkers, and treatments of age-related WMC.

Association between cytokines and cerebral MRI changes in the aging brain

The association between cytokines (IL-1 beta, sIL-4R, IL-6, IL-8, IL-10, IL-12, TNF-alpha) and subcortical white matter lesions, cortical atrophy and lacunar infarctions of the aging brain was investigated among 268 elderly community participants. Single pro- and anti-inflammatory cytokines were neither associated with WML nor with atrophy and lacunar infarction. An association between atrophy and the chemokine-cytokine factor (containing sIL-4R, IL-6, IL-8) remained significant after adjustment for age, gender, education, depressive symptoms, diabetes mellitus, cardiovascular diseases (stroke, TIA, myocardial infarction, myocardial insufficiency, arrhythmic heart), hypertension, body-mass index, smoking status and aggregation inhibitors as opposed to single cytokines. Atrophy of the parietal, temporal and occipital lobes was associated with the same cytokine-chemokine factor for both the whole sample or restricted to those without history of stroke/TIA. The results indicate that a combination of chemokine-cytokines rather than single cytokines may contribute to inflammatory processes associated with cortical atrophy in the aging brain.

Prevention of stroke in patients with hypertension

Despite the substantial evidence of the benefits of lowering blood pressure, conventional treatment does not normalize the burden of major cardiovascular events in patients with hypertension. Data now suggest that the nature of the antihypertensive agent used may have an important impact on long-term cardiovascular outcomes, including stroke. Optimal treatment should provide powerful 24-hour blood pressure control, including during the early morning hours when the risk of stroke is highest. In addition, antihypertensive therapies selected should have positive blood pressure-independent effects on stroke risk. In contrast to angiotensin-converting enzyme inhibitors, angiotensin II receptor blockers (ARBs) provide consistent benefits in stroke protection beyond blood pressure lowering. The ARB telmisartan has a particularly interesting profile for stroke management. Selective angiotensin II type 1 receptor blockade and 24-hour blood pressure control with telmisartan provide the potential for improved stroke prevention. This will be investigated in the Prevention Regimen for Effectively Avoiding Second Strokes (PROFESS) study.

Guiding antihypertensive treatment decisions using ambulatory blood pressure monitoring

Compared with isolated clinic measurements, ambulatory blood pressure monitoring (ABPM) provides an insight into blood pressure (BP) changes in everyday life and an estimate of the overall BP load exerted on the cardiovascular system over 24 hours. Cross-sectional evidence suggests a direct and significant relationship between ambulatory BP and organ damage. There is also longitudinal evidence for a superior predictive value of 24-hour BP in relation to the risk for cardiovascular morbidity and mortality as opposed to clinic BP. The usefulness of ABPM in pharmacologic studies aimed at evaluating the 24-hour antihypertensive efficacy of different drugs and drug combinations is now acknowledged. Among the mathematical indices available to explore 24-hour BP coverage by treatment, the ABPM-derived smoothness index provides a superior measure of the homogeneity of BP control compared with trough:peak ratios. The main applications of clinical practice should be in identifying patients with isolated office hypertension and those who are nonresponders to treatment, in assessing coverage of the 24-hour BP profile in high-risk patients and in diagnosing suspected treatment-related hypotension.

Increased expression of glial fibrillary acidic protein in the brain of spontaneously hypertensive rats

Astrogliosis, consisting in astroglial proliferation and increased expression of the specific cytoskeletal protein glial fibrillary acid protein (GFAP) is common in several situations of brain damage. Arterial hypertension, which induces cerebrovascular changes, can cause also brain damage, neurodegeneration and dementia (vascular dementia). This study was designed to assess astroglial reaction in different brain areas (frontal cortex, occipital cortex, hippocampus and striatum) of spontaneously hypertensive rats (SHR) in the pre-hypertensive phase (2 months of age), in the developing phase of hypertension (4 months of age) and in established hypertension (6 months of age). SHR were compared to age-matched normotensive Wistar-Kyoto (WKY) rats. Analysis included reverse transcription-polymerase chain reaction (RT-PCR) of GFAP mRNA, GFAP immunochemistry (Western blot analysis) and immunohistochemistry. A significant increase of GFAP mRNA and an increase of GFAP immunoreactivity were noticeable in different brain areas of SHR compared to normotensive WKY rats at 6, but not at 2 or 4 months of age. Immunohistochemistry revealed a numerical augmentation (hyperplasia) and an increase in size (hypertrophy) of GFAP-immunoreactive astrocytes in frontal cortex, occipital cortex and striatum of SHR. In the hippocampus of SHR only a numerical increase of GFAP-immunoreactive astrocytes was found. These finding demonstrating the occurrence of astrogliosis in the brain of SHR with established hypertension suggest that hypertension induces a condition of brain suffering enough to increase biosynthesis and expression of GFAP similarly as reported in several neurodegenerative disorders and in brain ischemia.

Alteration in dendritic morphology of pyramidal neurons from the prefrontal cortex of rats with renovascular hypertension

We have studied, in the rat, the dendritic morphological changes of the pyramidal neurons of the medial part of the prefrontal cortex induced by the chronic effect of high blood pressure. Renovascular hypertension was induced using a silver clip on the renal artery by surgery. The morphology of the pyramidal neurons from the medial part of the prefrontal cortex was investigated in these animals. The blood pressure was measured to confirm the increase in the arterial blood pressure. After 16 weeks of increase in the arterial blood pressure, the animals were sacrificed by overdoses of sodium pentobarbital and perfused intracardially with a 0.9% saline solution. The brains were removed, processed by the Golgi-Cox stain method and analyzed by the Sholl method. The dendritic morphology clearly showed that the hypertensive animals had an increase (32%) in the dendritic length of the pyramidal cells with a decrease (50%) in the density of dendritic spines when compared with sham animals. The branch-order analysis showed that the animals with hypertension exhibit more dendritic arborization at the level of the first to fourth branch order. This result suggests that renovascular hypertension may in part affect the dendritic morphology in this limbic structure, which may implicate cognitive impairment in hypertensive patients.

[Loss of motivation and frontal dysfunction. Role of the white matter change]

Since the recognition of white matter changes on computed tomography, researches were done to investigate a possible relation with ageing and cognition. This study examined whether computed tomography evidence of cerebrovascular disease in the form of white matter changes was associated with decreased implicit performance of frontal tests and with a loss of motivation in a group of 10 elderly volunteers with a mild cognitive impairment and in a group of 29 demented patients; 39 old patients (28 females: 82.4 +/- 7.1; 10 males: 75.5 +/- 11.3) cared in a psycho-geriatric day care hospital were enrolled for this essay. Motivation was evaluated with a specific scale: EAD. Patients were tested during the same period with MMSE for cognition, Cornell's scale for depression, Marin's scale for apathy. There were also assessed with a battery of frontal tests: BREF test. A brain scan was used to determinate the presence of leukoaraïosis. Table 1 give a description of the population according to the pathology. Cognitive disorder, but also apathy and loss motivation, frontal evaluation significantly differ in the two studied groups. The presence of a leukoaraïosis is associated with older people, a weaker cognitive status, a more important apathy or loss of motivation, and weaker results with frontal evaluation (table 2). Similar results were obtained considering only the frontal lesions (table 3). Age related changes of the white matter observed on computed tomography were associated with a decreased cognitive status. Leukoaraïosis is associated with loss of motivation and related with a poor results on frontal assessment. Loss of motivation is associated with certain frontal dysfunctions and with brain abnormal scan anomalies.

Heritability of leukoaraiosis in hypertensive sibships

Ischemic damage to the subcortical white matter of the brain, referred to as leukoaraiosis, is a frequent complication of hypertension-related microvascular disease and contributes to the risk of stroke and vascular dementia. A large genetic contribution to this late-life form of target organ damage was suggested by a study of elderly male twins. As part of the Genetic Epidemiology Network of Arteriopathy (GENOA), 483 non-Hispanic white subjects were recruited to undergo MRI for determination of the brain volume of leukoaraiosis (291 women and 192 men from 210 sibships providing 434 sibling pairs; mean age+/-SD=65.2+/-7.3 years). The GENOA-Rochester sibships contain 2 or more siblings with essential hypertension diagnosed before age 60. The frequency distribution of the volume of leukoaraiosis was positively skewed, with a median value of 6.61 cm3 (interquartile range: 4.77 to 9 0.83 cm3). Variance component models were used to estimate the heritability (ie, the proportion of phenotypic variation caused by additive genetic factors). After logarithm transformation of the volume of leukoaraiosis, the estimated heritability (+/-SE) was 0.802+/-0.102 (P<0.0001). Adjustments for sex, age, systolic blood pressure, and brain volume reduced the heritability estimate to 0.671+/-0.110 (P<0.0001). This evidence of strong genetic influence on the susceptibility to leukoaraiosis justifies efforts to localize the responsible genes and characterize the predisposing genetic polymorphisms.

Genetics of blood pressure, hypertensive complications, and antihypertensive drug responses

Hypertension is the most prevalent, treatable risk factor for diseases of the heart, brain and kidneys. In this review, we discuss advances in understanding of the genetics of blood pressure regulation, the development of hypertensive complications and the pharmacodynamics of antihypertensive drug responses. Discovery of single gene mutations that cause hypertension or hypotension in humans suggests that the common final pathway for regulation of blood pressure level is via alterations in renal sodium handling. Based on a working hypothesis that common genetic variations contributing to blood pressure variation in the population may also act on this same pathway, we summarize supporting evidence emerging from linkage and selected association studies of candidate genes--including those encoding components of the renin-angiotensin-aldosterone system, the epithelial sodium channel, adrenoceptors, G protein subunits, and other cellular signaling mediators and modifiers. We proceed to distinguish ischemic target organ complications due to arteriolosclerotic changes of the microvasculature from those due to atherosclerosis involving larger conduit and capacitance arteries. Using the example of subcortical white matter ischemia of the brain, we propose that interindividual variation in the arteriolosclerotic complications is more likely than atherosclerotic complications to be related to the same genetic (and environmental) mechanisms that contribute to hypertension. We conclude by summarizing the state-of-the-art of antihypertensive pharmacogenetics, which has succeeded in rejecting the null hypothesis that genetic variation does not influence blood pressure or protective target organ responses to drug therapy. In each of the three areas covered in this review, we indicate the many remaining obstacles to the routine clinical use of genetic measurements in the diagnosis, evaluation and treatment of hypertension.

Are antihypertensive agents protective against dementia? A review of clinical and preclinical data

In the United States, the size of the population of persons aged 65 years or older is expected to double within the next 30 years, resulting in a marked increase in the prevalence of dementia. Hypertension is a risk factor for cognitive impairment and dementia in addition to cerebrovascular morbidity and mortality. The evidence for a connection between high blood pressure in midlife and dementia in late life comes from numerous longitudinal studies. A placebo-controlled, double-blind, randomized trial involving 2,418 patients aged 60 years or older with isolated systolic hypertension demonstrated that active treatment based on the dihydropyridine calcium antagonist nitrendipine with the addition of enalapril, hydrochlorothiazide, or both if needed to control systolic blood pressure to <150 mmHg, significantly reduced not only stroke and cardiovascular complications but also the incidence of vascular dementia and Alzheimer's disease. Several trials of antihypertensive treatment are ongoing to confirm this important finding. The newer dihydropyridine calcium antagonists lacidipine and lercanidipine are effective and well tolerated in the treatment of hypertension. In animal models, these newer agents also have been shown to prevent the progression of hypertensive microvascular damage. Their neuroprotective effects offer possible unique advantages in the management of hypertension.

Genetics of leukoaraiosis

Computed tomography and magnetic resonance imaging of the brains of elderly individuals frequently show areas of altered signal intensity in the periventricular and subcortical white matter, referred to as leukoaraiosis. Although mildly affected individuals appear asymptomatic, larger burdens of leukoaraiosis are associated with deficits of cognition and gait. Histopathologically, areas of leukoaraiosis invariably show sclerosis, luminal narrowing, and tortuosity of small arteries and arterioles, accompanied by variable degrees of gliosis, demyelination, and axonal loss resulting from ischemia. Genetic variation plays a substantial role in interindividual differences in the volume of leukoaraiosis and its associated adverse clinical outcomes. Characterizing genetic factors contributing to interindividual differences in leukoaraiosis has the potential to enhance understanding of molecular determinants of ischemic brain injury and lead to new approaches to the diagnosis, evaluation, treatment, and prevention of this common form of vascular dementia.