Hippocampal atrophy, whole brain volume, and white matter lesions in older hypertensive subjects.
ABSTRACT To determine the potential role of whole brain atrophy, hippocampal atrophy, or both, and small vessel disease/white matter lesions as mechanisms underlying the cognitive impairment associated with hypertension.
Using MRI scanning the authors determined hippocampal volumes, whole brain volumes, and location and severity of white matter lesions, using Scheltens scale, in 103 hypertensive (166 +/- 8/88 +/- 7 mm Hg, 54 female) and 51 normotensive (132 +/- 12/74 +/- 7 mm Hg, 21 female) subjects age > or = 70 years.
Compared to normotensive subjects, older hypertensive subjects had significantly smaller whole brain volumes (887 +/- 109 vs 930 +/- 97 cm3, p = 0.02) and nonsignificantly reduced hippocampal volumes (5.39 +/- 1.60 vs 5.67 +/- 1.80 cm3, p = 0.33). Hypertensive subjects had an increased burden of periventricular lesions: bands (p = 0.03), frontal caps (p = 0.08), occipital caps (p = 0.07), and total periventricular hyperintensities (p = 0.02). They also had higher scores in subcortical areas: frontal (p = 0.04), temporal (p = 0.03), and deep white matter areas (p = 0.05). A correlation was found between whole brain volumes and systolic blood pressure (r = -0.19, p = 0.02). No correlation was seen between whole brain volumes and white matter lesion burden.
Moderate hypertension in non-impaired older subjects is associated with smaller whole brain volume and an increased burden of subcortical and periventricular white matter lesions.
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ABSTRACT: Alzheimer’s disease (AD) is a progressive neurodegenerative disorder. The human brain is extremely sensitive to hypoxia, ischemia, and glucose depletion. Impaired delivery of oxygen in obstructive sleep apnea (OSA) alters neuronal homeostasis, induces pathology, and triggers neuronal degeneration/death. This article systematically delineates the steps in the complex cascade leading to AD, focusing on pathology caused by chronic intermittent hypoxia, hypertension, brain hypoperfusion, glucose dysmetabolism, and endothelial dysfunction. Hypoxia/hypoxemia underpins several pathological processes including sympathetic activation, chemoreflex activity, neuroinflammation, oxidative stress, and a host of perturbations leading to neurodegeneration. The arterial blood flow reduction in OSA is profound, being about 76 % in obstructive hypopneas and 80 % in obstructive apneas; this leads to cerebral ischemia promoting neuronal apoptosis in neocortex and brainstem. OSA pathology also includes gray matter loss in the frontal, parietal, temporal, and occipital cortices, the thalamus, hippocampus, and key brainstem nuclei including the nucleus tractus solitarius. (18)F-FDG PET studies on OSA and AD patients, and animal models of AD, have shown reduced cerebral glucose metabolism in the above mentioned brain regions. Owing to the pathological impact of hypoxia, hypertension, hypoperfusion and impaired glucose metabolism, the adverse cardiovascular, neurocirculatory and metabolic consequences upregulate amyloid beta generation and tau phosphorylation, and lead to memory/cognitive impairment—culminating in AD. The framework encompassing these factors provides a pragmatic neuropathological approach to explain onset of Alzheimer’s dementia. The basic tenets of the current paradigm should influence the design of therapeutic strategies to ameliorate AD.Neurochemical Research 01/2012; 37(12). · 2.13 Impact Factor
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ABSTRACT: Estrogens are neuroprotective factors for brain diseases, including hypertensive encephalopathy. In particular, the hippocampus is highly damaged by high blood pressure, with several hippocampus functions being altered in humans and animal models of hypertension. Working with a genetic model of primary hypertension, the spontaneously hypertensive rat (SHR), we have shown that SHR present decreased dentate gyrus neurogenesis, astrogliosis, low expression of brain derived neurotrophic factor (BDNF), decreased number of neurons in the hilus of the dentate gyrus, increased basal levels of the estrogen-synthesizing enzyme aromatase, and atrophic dendritic arbour with low spine density in the CA1 region compared to normotensive Wistar Kyoto (WKY) ratsl. Changes also occur in the hypothalamus of SHR, with increased expression of the hypertensinogenic peptide arginine vasopressin (AVP) and its V1b receptor. Following chronic estradiol treatment, SHR show decreased blood pressure, enhanced hippocampus neurogenesis, decreased the reactive astrogliosis, increased BDNF mRNA and protein expression in the dentate gyrus, increased neuronal number in the hilus of the dentate gyrus, further increased the hyperexpression of aromatase and replaced spine number with remodelling of the dendritic arbour of the CA1 region. We have detected by qPCR the estradiol receptors ERα and ERβ in hippocampus from both SHR and WKY rats, suggesting direct effects of estradiol on brain cells. We hypothesize that a combination of exogenously given estrogens plus those locally synthesized by estradiol-stimulated aromatase may better alleviate the hippocampal and hypothalamic encephalopathy of SHR.The Journal of steroid biochemistry and molecular biology 04/2014; · 3.98 Impact Factor
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ABSTRACT: Late onset Alzheimer’s disease (AD) is the most common cause of progressive cognitive dysfunction and dementia. Despite considerable progress in elucidating the molecular pathology of this disease, we are not yet close to unraveling its etiopathogenesis. The hippocampus is at the epicenter of cognition being associated with learning and memory. A battery of neurotoxic modifiers has been delineated that may unleash deleterious heterogeneous pathologic impacts. Synergistically they target hippocampus causing its neuronal degeneration, gray matter volume atrophy, and progressive cognitive decline. The neurotoxic factors include aging, stress, depression, hypoxia/hypoxemia, hypertension, diabetes, obesity, alcohol abuse, smoking, malnutrition, and polypharmacy—to name a few. Addressing “upstream pathologies” due to these multiple and heterogeneous neurotoxic modifiers vis-a-vis hippocampal dysfunction is of paramount importance. The downstream-generated inflammatory cytokines, mitochondrial dysfunction, oxidative stress, hypoperfusion, excitotoxicity, amyloid beta, and neurofibrillary tangles may then trigger and sustain neurocognitive pathology. The failure of clinical trials in AD is due in part to this complex multifactorial neurotoxic–pathophysiological labyrinth. The key is to employ appropriate preventive and treatment strategies prior to significant hippocampus damage and its dysfunction. Prevention/reversal of the diverse neurotoxic impacts, delineated here, should be an integral part of therapeutic armamentarium, in order to ameliorate hippocampus dysfunction and to enhance memory in aging, mild cognitive impairment, and AD. Throughout, the paper highlights both the challenges presented by the ever present neurotoxic onslaught, and the opportunities to overcome them. Hence, arresting AD pathogenesis is achievable through early intervention. A targeted approach may ameliorate neurocognitive pathology and attenuate memory deterioration.Neurotoxicity Research 07/2013; · 2.87 Impact Factor