Arterial stiffness and cognitive impairment

Blood Pressure Control and Protection of the Aging Brain

Hypertension and dementia are both common disorders whose prevalence increases with age. There are multiple mechanisms by which hypertension affects the brain and alters cognition. These include blood flow dynamics, development of large and small vessel pathology and diverse molecular mechanisms including formation of reactive oxygen species and transcriptional cascades. Blood pressure interacts with Alzheimer disease pathology in numerous and unpredictable ways, affecting both β-amyloid and tau deposition, while also interacting with AD genetic risk factors and other metabolic processes. Treatment of hypertension may prevent cognitive decline and dementia, but methodological issues have limited the ability of randomized clinical trials to show this conclusively. Recent studies have raised hope that hypertension treatment may protect the function and structure of the aging brain from advancing to mild cognitive impairment and dementia.

Pulse Wave Velocity in Atherosclerosis

Early detection of subclinical atherosclerosis is important to reduce patients' cardiovascular risk. However, current diagnostic strategy focusing on traditional risk factors or using risk scoring is not satisfactory. Non-invasive imaging tools also have limitations such as cost, time, radiation hazard, renal toxicity, and requirement for specialized techniques or instruments. There is a close interaction between arterial stiffness and atherosclerosis. Increased luminal pressure and shear stress by arterial stiffening causes endothelial dysfunction, accelerates the formation of atheroma, and stimulates excessive collagen production and deposition in the arterial wall, leading to the progression of atherosclerosis. Pulse wave velocity (PWV), the most widely used measure of arterial stiffness, has emerged as a useful tool for the diagnosis and risk stratification of cardiovascular disease (CVD). The measurement of PWV is simple, non-invasive, and reproducible. There have been many clinical studies and meta-analyses showing the association between PWV and coronary/cerebral/carotid atherosclerosis. More importantly, longitudinal studies have shown that PWV is a significant risk factor for future CVD independent of well-known cardiovascular risk factors. The measurement of PWV may be a useful tool to select subjects at high risk of developing subclinical atherosclerosis or CVD especially in mass screening.

Pulse Wave Velocity in Atherosclerosis

Early detection of subclinical atherosclerosis is important to reduce patients' cardiovascular risk. However, current diagnostic strategy focusing on traditional risk factors or using risk scoring is not satisfactory. Non-invasive imaging tools also have limitations such as cost, time, radiation hazard, renal toxicity, and requirement for specialized techniques or instruments. There is a close interaction between arterial stiffness and atherosclerosis. Increased luminal pressure and shear stress by arterial stiffening causes endothelial dysfunction, accelerates the formation of atheroma, and stimulates excessive collagen production and deposition in the arterial wall, leading to the progression of atherosclerosis. Pulse wave velocity (PWV), the most widely used measure of arterial stiffness, has emerged as a useful tool for the diagnosis and risk stratification of cardiovascular disease (CVD). The measurement of PWV is simple, non-invasive, and reproducible. There have been many clinical studies and meta-analyses showing the association between PWV and coronary/cerebral/carotid atherosclerosis. More importantly, longitudinal studies have shown that PWV is a significant risk factor for future CVD independent of well-known cardiovascular risk factors. The measurement of PWV may be a useful tool to select subjects at high risk of developing subclinical atherosclerosis or CVD especially in mass screening.

Association Between Cardiovascular Risk Factors and Stress Hormones With Cognitive Performance in Mexican Adolescents

Objective

The objective of this study was to determine whether cardiovascular disease (CVD) risk factors and stress hormones are associated with cognitive performance in Mexican adolescents.

Methods

This was a cross-sectional study including 139 Mexican adolescents 10-14 years old. Participants were divided into three categories: 0, 1-2, and ≥3 CVD risk factors. These factors included: high-density lipoprotein-cholesterol (HDL-C) <40 mg/dl; waist circumference (WC) ≥90th percentile for age and sex, systolic or diastolic blood pressure ≥90th percentile for age, sex, and height; and triacylglycerols (TGs) ≥110 mg/dl. Low-density lipoprotein-cholesterol (LDL-C), very low-density lipoprotein-cholesterol (VLDL-C), total cholesterol, cortisol, and plasma catecholamines were measured as well. Furthermore, attention, memory, and executive functions were evaluated using a validated test for Spanish-speaking individuals (Neuropsi).

Results

Adolescents in the three risk categories did not show significant differences in Neuropsi test performance tasks; however, they presented different lipid and plasma norepinephrine concentrations. TG and VLDL-C were inversely associated with memory (r = -0.19, **p < .01). Multivariate regression analysis showed consistently that TG/HDL-C ratio was inversely related to attention-memory general score (standardized β = -0.99, t = -2.30, p = .023), memory (standardized β = -0.83, t = -2.08, p = .039), and attention-executive functions (standardized β = -1.02, t = -2.42, p = .017). Plasma epinephrine levels presented an inverse and weak relation to the attention-executive functions score (standardized β = -0.18, t = -2.19, p = .030).

Conclusions

Cognitive performance is not completely dependent on the accumulation of risk factors, but instead on the combination of strong predictors of CVD like waist to height ratio, TG/HDL-C, and VLDL-C. Plasma norepinephrine and epinephrine have a stronger association with cognition and CVD risk than dopamine and cortisol.

Chronic Kidney Disease and Pulse Wave Velocity: A Narrative Review

Chronic kidney disease (CKD) is associated with excess cardiovascular mortality, resulting from both traditional and nontraditional, CKD-specific, cardiovascular risk factors. Nontraditional risk factors include the entity Chronic Kidney Disease-Mineral and Bone Disorder (CKD-MBD) which is characterised by disorders of bone and mineral metabolism, including biochemical abnormalities of hyperphosphatemia and hyperparathyroidism, renal osteodystrophy, and vascular calcification. Increased arterial stiffness in the CKD population can be attributed amongst other influences to progression of vascular calcification, with significant resultant contribution to the cardiovascular disease burden. Pulse wave velocity (PWV) measured over the carotid-femoral arterial segments is the noninvasive gold-standard technique for measurement of aortic stiffness and has been suggested as a surrogate cardiovascular end-point. A PWV value of 10 m/s or greater has been recommended as a suitable cut-off for an increased risk of cardiovascular mortality. CKD is a risk factor for an excessive rate of increase in aortic stiffness, reflected by increases in PWV, and increased aortic PWV in CKD shows faster progression than for individuals with normal kidney function. Patients with varying stages of CKD, as well as those on dialysis or with a kidney transplant, have different biological milieu which influence aortic stiffness and associated changes in PWV. This review discusses the pathophysiology of arterial stiffness with CKD and outlines the literature on PWV across the spectrum of CKD, highlighting that determination of arterial stiffness using aortic PWV can be a useful diagnostic and prognostic tool for assessing cardiovascular disease in the CKD population.

Effect of revascularization on cognitive outcomes in intracranial steno-occlusive disease: a systematic review

OBJECTIVESteno-occlusive diseases of the cerebral vasculature have been associated with cognitive decline. The authors performed a systematic review of the existing literature on intracranial steno-occlusive disease, including intracranial atherosclerosis and moyamoya disease (MMD), to determine the extent and quality of evidence for the effect of revascularization on cognitive performance.METHODSA systematic search of PubMed/MEDLINE, the Thomson Reuters Web of Science Core Collection, and the KCI Korean Journal Database was performed to identify randomized controlled trials (RCTs) in the English-language literature and observational studies that compared cognitive outcomes before and after revascularization in patients with steno-occlusive disease of the intracranial vasculature, from which data were extracted and analyzed.RESULTSNine papers were included, consisting of 2 RCTs and 7 observational cohort studies. Results from 2 randomized trials including 142 patients with symptomatic intracranial atherosclerotic steno-occlusion found no additional benefit to revascularization when added to maximal medical therapy. The certainty in the results of these trials was limited by concerns for bias and indirectness. Results from 7 observational trials including 282 patients found some cognitive benefit for revascularization for symptomatic atherosclerotic steno-occlusion and for steno-occlusion related to MMD in children. The certainty of these conclusions was low to very low, due to both inherent limitations in observational studies for inferring causality and concerns for added risk of bias and indirectness in some studies.CONCLUSIONSThe effects of revascularization on cognitive performance in intracranial steno-occlusive disease remain uncertain due to limitations in existing studies. More well-designed randomized trials and observational studies are needed to determine if revascularization can arrest or reverse cognitive decline in these patients.

A Major Role for the Lateral Habenula in Depressive Illness: Physiologic and Molecular Mechanisms

Emerging preclinical and clinical evidence indicate that the lateral habenula plays a major role in the pathophysiology of depressive illness. Aberrant increases in neuronal activity in the lateral habenula, an anti-reward center, signals down-regulation of brainstem dopaminergic and serotonergic firing, leading to anhedonia, helplessness, excessive focus on negative experiences, and, hence, depressive symptomatology. The lateral habenula has distinctive regulatory adaptive role to stress regulation in part due to its bidirectional connectivity with the hypothalamic-pituitary-adrenal (HPA) axis. In addition, studies show that increased lateral habenula activity affects components of sleep regulation including slow wave activity and rapid eye movement (REM), both disrupted in depressive illness. Lack of perceived reward experienced during the adverse outcomes also precipitates lateral habenula firing, while outcomes that meet or exceed expectations decrease lateral habenula firing and, in turn, increase midbrain dopaminergic and serotonergic neurotransmission. The ability to update expectations of the environment based on rewards and aversive stimuli reflects a potentially important survival mechanism relevant to the capacity to adapt to changing circumstances. What if one lives in a continuously aversive and invalidating environment or under the conditions of chronic stress? If there is a propensity of the habenula to release many burst discharges over time, an individual could habitually come to perceive the world as perpetually disappointing. Conceivably, the lateral habenula could learn to expect an adverse outcome systematically and communicate it more easily. Thus, if the lateral habenula fires more frequently, it may lead to a state of continuous disappointment and hopelessness, akin to depression. Furthermore, postmortem studies reveal that the size of the lateral habenula and total number of neurons are decreased in patients who had depressive illness. Novel research in the field shows that ketamine induces rapid and sustained antidepressant effect. Intriguingly, recent preclinical animal models show that ketamine abolishes N-methyl-D-aspartate receptor (NMDAR)-dependent lateral habenula bursting activity, leading to rapid resolution of depressive symptoms.

Cognitive Functioning of Geriatric Patients: Is Hypovitaminosis D the Next Marker of Cognitive Dysfunction and Dementia?

The study objective is to investigate whether vitamin D is associated with the cognitive function of geriatric patients. This cross-sectional study involved 357 patients hospitalized in the geriatric ward who complained of memory problems (mean age: 82.3 years). The level of cognitive function was measured with the Mini-Mental State Examination (MMSE) and the clinical diagnosis of dementia was established according to the International Classification of Diseases (ICD-10) criteria. The serum 25-hydroxy vitamin D was measured with liquid chromatography-tandem mass spectrometry. The iterative Bayesian model averaging (BMA) procedure was applied to linear and logistic regression models in order to identify the best set of factors describing cognitive dysfunction and dementia, respectively. According to BMA, there is strong evidence that higher vitamin D levels, higher body mass index (BMI), and higher mobility function measured with the Timed Up and Go (TUG) test are independently associated with better cognitive performance and lower risk of dementia. Additionally, there is strong evidence that fewer years of education and lower vitamin B12 plasma levels independently describe worse cognitive performance. However, vitamin B12 levels higher than 800 pg/mL is negatively associated with the MMSE performance. Hypovitaminosis D in geriatric patients is an underrated marker of cognitive dysfunction and dementia.

Evaluation of Metformin on Cognitive Improvement in Patients With Non-dementia Vascular Cognitive Impairment and Abnormal Glucose Metabolism

Objective: Recent studies have suggested that metformin can penetrate the blood–brain barrier, protecting neurons via anti-inflammatory action and improvement of brain energy metabolism. In this study, we aim to investigate the effect of metformin on cognitive function in patients with abnormal glucose metabolism and non-dementia vascular cognitive impairment (NDVCI).

Methods: One hundred patients with NDVCI and abnormal glucose metabolism were randomly allocated into two groups: metformin and donepezil (n = 50) or acarbose and donepezil (n = 50). The neuropsychological status, glucose metabolism, and common carotid arteries intima–media thickness (CCA-IMT) before and after a year of treatment, were measured and compared between the groups.

Results: Ninety four patients completed all the assessment and follow-up. After a year of treatment, there was a decrease in Alzheimer’s disease Assessment Scale-Cognitive Subscale scores and the duration of the Trail Making Test in the metformin-donepezil group. Furthermore, these patients showed a significant increase in World Health Organization–University of California–Los Angeles Auditory Verbal Learning Test scores after treatment (all P < 0.05). However, there was no obvious improvement in cognitive function in the acarbose-donepezil group. We also observed a significant decrease in the level of fasting insulin and insulin resistance (IR) index in the metformin-donepezil group, with a lower CCA-IMT value than that in the acarbose-donepezil group after a year of treatment (P < 0.05).

Conclusion: We conclude that metformin can improve cognitive function in patients with NDVCI and abnormal glucose metabolism, especially in terms of performance function. Improved cognitive function may be related to improvement of IR and the attenuated progression of IMT.

Trial Registration:ChiCTR-IPR-17011855.

Vitamin D deficiency causes inward hypertrophic remodeling and alters vascular reactivity of rat cerebral arterioles

Background and purpose

Vitamin D deficiency (VDD) is a global health problem, which can lead to several pathophysiological consequences including cardiovascular diseases. Its impact on the cerebrovascular system is not well understood. The goal of the present work was to examine the effects of VDD on the morphological, biomechanical and functional properties of cerebral arterioles.

Methods

Four-week-old male Wistar rats (n = 11 per group) were either fed with vitamin D deficient diet or received conventional rat chow with per os vitamin D supplementation. Cardiovascular parameters and hormone levels (testosterone, androstenedione, progesterone and 25-hydroxyvitamin D) were measured during the study. After 8 weeks of treatment anterior cerebral artery segments were prepared and their morphological, biomechanical and functional properties were examined using pressure microangiometry. Resorcin-fuchsin and smooth muscle actin staining were used to detect elastic fiber density and smooth muscle cell counts in the vessel wall, respectively. Sections were immunostained for eNOS and COX-2 as well.

Results

VDD markedly increased the wall thickness, the wall-to-lumen ratio and the wall cross-sectional area of arterioles as well as the number of smooth muscle cells in the tunica media. As a consequence, tangential wall stress was significantly lower in the VDD group. In addition, VDD increased the myogenic as well as the uridine 5’-triphosphate-induced tone and impaired bradykinin-induced relaxation. Decreased eNOS and increased COX-2 expression were also observed in the endothelium of VDD animals.

Conclusions

VDD causes inward hypertrophic remodeling due to vascular smooth muscle cell proliferation and enhances the vessel tone probably because of increased vasoconstrictor prostanoid levels in young adult rats. In addition, the decreased eNOS expression results in endothelial dysfunction. These morphological and functional alterations can potentially compromise the cerebral circulation and lead to cerebrovascular disorders in VDD.