The impact of early aerobic exercise on brain microvascular alterations induced by cerebral hypoperfusion

Exploring the neuroprotective role of physical activity in cerebral small vessel disease

Cerebral small vessel disease (cSVD) is a common neurological finding characterized by abnormalities of the small blood vessels in the brain. Previous research has established a strong connection between cSVD and stroke, as well as neurodegenerative disorders, notably Alzheimer's disease (AD) and other dementias. As the search for effective interventions continues, physical activity (PA) has emerged as a potential preventative and therapeutic avenue. This review synthesizes the human and animal literature on the influence of PA on cSVD, highlighting the importance of determining optimal exercise protocols, considering aspects such as intensity, duration, timing, and exercise type. Furthermore, the necessity of widening the age bracket in research samples is discussed, ensuring a holistic understanding of the interventions across varying pathological stages of the disease. The review also suggests the potential of exploring diverse biomarkers and risk profiles associated with clinically significant outcomes. Moreover, we review findings demonstrating the beneficial effects of PA in various rodent models of cSVD, which have uncovered numerous mechanisms of neuroprotection, including increases in neuroplasticity and integrity of the vasculature and white matter; decreases in inflammation, oxidative stress, and mitochondrial dysfunction; and alterations in amyloid processing and neurotransmitter signaling. In conclusion, this review highlights the potential of physical activity as a preventive strategy for addressing cSVD, offering insights into the need for refining exercise parameters, diversifying research populations, and exploring novel biomarkers, while shedding light on the intricate mechanisms through which exercise confers neuroprotection in both humans and animal models.

Exercise Improves Cerebral Blood Flow and Functional Outcomes in an Experimental Mouse Model of Vascular Cognitive Impairment and Dementia (VCID)

Vascular cognitive impairment and dementia (VCID) are a growing threat to public health without any known treatment. The bilateral common carotid artery stenosis (BCAS) mouse model is valid for VCID. Previously, we have reported that remote ischemic postconditioning (RIPostC) during chronic cerebral hypoperfusion (CCH) induced by BCAS increases cerebral blood flow (CBF), improves cognitive function, and reduces white matter damage. We hypothesized that physical exercise (EXR) would augment CBF during CCH and prevent cognitive impairment in the BCAS model. BCAS was performed in C57/B6 mice of both sexes to establish CCH. One week after the BCAS surgery, mice were randomized to treadmill exercise once daily or no EXR for four weeks. CBF was monitored with an LSCI pre-, post, and 4 weeks post-BCAS. Cognitive testing was performed for post-BCAS after exercise training, and brain tissue was harvested for histopathology and biochemical test. BCAS led to chronic hypoperfusion resulting in impaired cognitive function and other functional outcomes. Histological examination revealed that BCAS caused changes in neuronal morphology and cell death in the cortex and hippocampus. Immunoblotting showed that BCAS was associated with a significant downregulate of AMPK and pAMPK and NOS3 and pNOS3. BCAS also decreased red blood cell (RBC) deformability. EXR therapy increased and sustained improved CBF and cognitive function, muscular strength, reduced cell death, and loss of white matter. EXR is effective in the BCAS model, improving CBF and cognitive function, reducing white matter damage, improving RBC deformability, and increasing RBC NOS3 and AMPK. The mechanisms by which EXR improves CBF and attenuates tissue damage need further investigation.

Circulating exo-miR-154-5p regulates vascular dementia through endothelial progenitor cell-mediated angiogenesis

Background

Vascular dementia (VaD) mainly results from cerebral vascular lesions and tissue changes, which contribute to neurodegenerative processes. Effective therapeutic approaches to targeting angiogenesis may reduce mortality of VaD. Endothelial progenitor cells (EPCs) play a key role in postnatal angiogenesis. Many exosomal microRNAs (exo-miRNAs) have been reported to involve in the development of dementia. The present study was designed to investigate whether the expression profile of the exo-miRNAs is significantly altered in patients with VaD and to reveal the function of differentially expressed miRNAs and the relevant mechanisms in EPC-mediated angiogenesis in VaD rat model.

Results

Exosomes isolated from serum of patients with VaD (n = 7) and age-matched control subjects (n = 7), and miRNA sequencing and bioinformatics analysis found that circulating exosome miRNA-155-5p, miRNA-154-5p, miR-132-5p, and miR-1294 were upregulated in patients with VaD. The expression of miRNA-154-5p was further verified to be upregulated in clinical samples (n = 23) and 2-vessel occlusion-induced VaD rat model by reverse transcription quantitative PCR (RT-qPCR). Notably, miRNA-154-5p inhibition in bone marrow-EPCs (BM-EPCs) from VaD rats improved EPC functions, including tube formation, migration, and adhesion, and elevated concentrations of vascular endothelial growth factor (VEGF) and stromal cell-derived factor-1α (SDF-1α). The mRNA levels of ICAM-1, VCAM-1, and MCP-1 were reduced in miRNA-154-5p-inhibited EPCs. In addition, miRNA-154-5p inhibition increased the level of superoxide dismutase (SOD), and decreased reactive oxygen species (ROS) in EPCs. PRKAA2 was chosen as a promising target gene of miR-154-5p, and miRNA-154-5p inhibition upregulated the protein expression of AMPKα2. Furthermore, upregulation of miR-154-5p markedly diminished EPC functions and inhibited angiogenesis following EPC transplantation in VaD rats.

Conclusion

Circulating exo-miR-154-5p was upregulated in patients with VaD, and miR-154-5p upregulation was associated with impaired EPC functions and angiogenesis in VaD rat model. Therefore, miR-154-5p is a promising biomarker and therapeutic strategy for VaD.

Prophylactic Zinc Administration Combined with Swimming Exercise Prevents Cognitive-Emotional Disturbances and Tissue Injury following a Transient Hypoxic-Ischemic Insult in the Rat

Exercise performance and zinc administration individually yield a protective effect on various neurodegenerative models, including ischemic brain injury. Therefore, this work was aimed at evaluating the combined effect of subacute prophylactic zinc administration and swimming exercise in a transient cerebral ischemia model. The prophylactic zinc administration (2.5 mg/kg of body weight) was provided every 24 h for four days before a 30 min common carotid artery occlusion (CCAO), and 24 h after reperfusion, the rats were subjected to swimming exercise in the Morris Water Maze (MWM). Learning was evaluated daily for five days, and memory on day 12 postreperfusion; anxiety or depression-like behavior was measured by the elevated plus maze and the motor activity by open-field test. Nitrites, lipid peroxidation, and the activity of superoxide dismutase (SOD) and catalase (CAT) were assessed in the temporoparietal cortex and hippocampus. The three nitric oxide (NO) synthase isoforms, chemokines, and their receptor levels were measured by ELISA. Nissl staining evaluated hippocampus cytoarchitecture and Iba-1 immunohistochemistry activated the microglia. Swimming exercise alone could not prevent ischemic damage but, combined with prophylactic zinc administration, reversed the cognitive deficit, decreased NOS and chemokine levels, prevented tissue damage, and increased Iba-1 (+) cell number. These results suggest that the subacute prophylactic zinc administration combined with swimming exercise, but not the individual treatment, prevents the ischemic damage on day 12 postreperfusion in the transient ischemia model.

The Effect of Physical Exercise on Cognitive Impairment in Neurodegenerative Disease: From Pathophysiology to Clinical and Rehabilitative Aspects

Neurodegenerative diseases are a group of pathologies that cause severe disability due to motor and cognitive limitations. In particular, cognitive impairment is a growing health and socioeconomic problem which is still difficult to deal with today. As there are no pharmacologically effective treatments for cognitive deficits, scientific interest is growing regarding the possible impacts of healthy lifestyles on them. In this context, physical activity is gaining more and more evidence as a primary prevention intervention, a nonpharmacological therapy and a rehabilitation tool for improving cognitive functions in neurodegenerative diseases. In this descriptive overview we highlight the neurobiological effects of physical exercise, which is able to promote neuroplasticity and neuroprotection by acting at the cytokine and hormonal level, and the consequent positive clinical effects on patients suffering from cognitive impairment.

Potentially undiagnosed cognitive impairment in patients with peripheral arterial disease: A systematic review of the literature

INTRODUCTION

It is purported that patients with peripheral arterial disease (PAD) may have impaired cognitive function due to concomitant cerebrovascular disease. Such disease may be clinically unrecognized but can impact on a patient's recovery and prognosis. The purpose of this systematic review was to interrogate the body of published evidence on undiagnosed cognitive impairment in PAD patients.

METHODS

A search strategy encompassing MEDLINE, Scopus, and the Cochrane database was developed to identify peer-reviewed articles examining rates of undiagnosed cognitive impairment in patients with PAD. The following search terms were used: 'PAD'; 'PVD'; 'dementia'; 'peripheral arterial disease'; 'peripheral vascular disease'; 'cognitive impairment'; 'alzheimer's disease' and 'cogniti∗'. Our primary outcome was the incidence of previously undiagnosed cognitive impairment in patients with PAD.

RESULTS

The initial search yielded 1492 titles. After removal of duplicates, 961 abstracts were screened to ascertain if they were eligible for inclusion. Abstract review yielded 62 full texts for further evaluation. Eight case-control studies consisting of 1161 patients were included. Analysis of these studies revealed that PAD patients performed significantly worse than controls on a variety of neuropsychological measures.

CONCLUSION

Our review indicated that PAD patients are more likely to suffer with undiagnosed cognitive impairment than healthy controls.

Physical exercise promotes astrocyte coverage of microvessels in a model of chronic cerebral hypoperfusion

BACKGROUND

Brain circulation disorders such as chronic cerebral hypoperfusion have been associated with a decline in cognitive function during the development of dementia. Astrocytes together with microglia participate in the immune response in the CNS and make them potential sentinels in the brain parenchyma. In addition, astrocytes coverage integrity has been related to brain homeostasis. Currently, physical exercise has been proposed as an effective intervention to promote brain function improvement. However, the neuroprotective effects of early physical exercise on the astrocyte communication with the microcirculation and the microglial activation in a chronic cerebral hypoperfusion model are still unclear. The aim of this study was to investigate the impact of early intervention with physical exercise on cognition, brain microcirculatory, and inflammatory parameters in an experimental model of chronic cerebral hypoperfusion induced by permanent bilateral occlusion of the common carotid arteries (2VO).

METHODS

Wistar rats aged 12 weeks were randomly divided into four groups: Sham-sedentary group (Sham-Sed), Sham-exercised group (Sham-Ex), 2VO-sedentary group (2VO-Sed), and 2VO-exercised group (2VO-Ex). The early intervention with physical exercise started 3 days after 2VO or Sham surgery during 12 weeks. Then, the brain functional capillary density and endothelial-leukocyte interactions were evaluated by intravital microscopy; cognitive function was evaluated by open-field test; hippocampus postsynaptic density protein 95 and synaptophysin were evaluated by western blotting; astrocytic coverage of the capillaries, microglial activation, and structural capillary density were evaluated by immunohistochemistry.

RESULTS

Early moderate physical exercise was able to normalize functional capillary density and reduce leukocyte rolling in the brain of animals with chronic cerebral hypoperfusion. These effects were accompanied by restore synaptic protein and the improvement of cognitive function. In addition, early moderate exercise improves astrocytes coverage in blood vessels of the cerebral cortex and hippocampus, decreases microglial activation in the hippocampus, and improves structural capillaries in the hippocampus.

CONCLUSIONS

Microcirculatory and inflammatory changes in the brain appear to be involved in triggering a cognitive decline in animals with chronic cerebral ischemia. Therefore, early intervention with physical exercise may represent a preventive approach to neurodegeneration caused by chronic cerebral hypoperfusion.

Effects of Remote Ischemic Conditioning on Cerebral Hemodynamics in Ischemic Stroke

Ischemic stroke is one of the most common cerebrovascular diseases and is the leading cause of disability all over the world. It is well known that cerebral blood flow (CBF) is disturbed or even disrupted when ischemic stroke happens. The imbalance between demand and shortage of blood supply makes ischemic stroke take place or worsen. The search for treatments that can preserve CBF, especially during the acute phase of ischemic stroke, has become a research hotspot. Animal and clinical experiments have proven that remote ischemic conditioning (RIC) is a beneficial therapeutic strategy for the treatment of ischemic stroke. However, the mechanism by which RIC affects CBF has not been fully understood. This review aims to discuss several possible mechanisms of RIC on the cerebral hemodynamics in ischemic stroke, such as the improvement of cardiac function and collateral circulation of cerebral vessels, the protection of neurovascular units, the formation of gas molecules, the effect on the function of vascular endothelial cells and the nervous system. RIC has the potential to become a therapeutic treatment to improve CBF in ischemic stroke. Future studies are needed to highlight our understanding of RIC as well as accelerate its clinical translation.

Cerebral Small Vessel Disease (CSVD) - Lessons From the Animal Models

Cerebral small vessel disease (CSVD) refers to a spectrum of clinical and imaging findings resulting from pathological processes of various etiologies affecting cerebral arterioles, perforating arteries, capillaries, and venules. Unlike large vessels, it is a challenge to visualize small vessels in vivo, hence the difficulty to directly monitor the natural progression of the disease. CSVD might progress for many years during the early stage of the disease as it remains asymptomatic. Prevalent among elderly individuals, CSVD has been alarmingly reported as an important precursor of full-blown stroke and vascular dementia. Growing evidence has also shown a significant association between CSVD's radiological manifestation with dementia and Alzheimer's disease (AD) pathology. Although it remains contentious as to whether CSVD is a cause or sequelae of AD, it is not far-fetched to posit that effective therapeutic measures of CSVD would mitigate the overall burden of dementia. Nevertheless, the unifying theory on the pathomechanism of the disease remains elusive, hence the lack of effective therapeutic approaches. Thus, this chapter consolidates the contemporary insights from numerous experimental animal models of CSVD, to date: from the available experimental animal models of CSVD and its translational research value; the pathomechanical aspects of the disease; relevant aspects on systems biology; opportunities for early disease biomarkers; and finally, converging approaches for future therapeutic directions of CSVD.

A refined model of chronic cerebral hypoperfusion resulting in cognitive impairment and a low mortality rate in rats

OBJECTIVE

The cognitive deficits of vascular dementia and the vasoocclusive state of moyamoya disease have often been mimicked with bilateral stenosis/occlusion of the common carotid artery (CCA) or internal carotid artery. However, the cerebral blood flow (CBF) declines abruptly in these models after ligation of the CCA, which differs from “chronic” cerebral hypoperfusion. While some modified but time-consuming techniques have used staged occlusion of both CCAs, others used microcoils for CCA stenosis, producing an adverse effect on the arterial endothelium. Thus, the authors developed a new chronic cerebral hypoperfusion (CCH) model with cognitive impairment and a low mortality rate in rats.

METHODS

Male Sprague-Dawley rats were subjected to unilateral CCA occlusion and contralateral induction of CCA stenosis (modified CCA occlusion [mCCAO]) or a sham operation. Cortical regional CBF (rCBF) was measured using laser speckle flowmetry. Cognitive function was assessed using a Barnes circular maze (BCM). MRI studies were performed 4 weeks after the operation to evaluate cervical and intracranial arteries and parenchymal injury. Behavioral and histological studies were performed at 4 and 8 weeks after surgery.

RESULTS

The mCCAO group revealed a gradual CBF reduction with a low mortality rate (2.3%). White matter degeneration was evident in the corpus callosum and corpus striatum. Although the cellular density declined in the hippocampus, MRI revealed no cerebral infarctions after mCCAO. Immunohistochemistry revealed upregulated inflammatory cells and angiogenesis in the hippocampus and cerebral cortex. Results of the BCM assessment indicated significant impairment in spatial learning and memory in the mCCAO group. Although some resolution of white matter injury was observed at 8 weeks, the animals still had cognitive impairment.

CONCLUSIONS

The mCCAO is a straightforward method of producing a CCH model in rats. It is associated with a low mortality rate and could potentially be used to investigate vascular disease, moyamoya disease, and CCH. This model was verified for an extended time point of 8 weeks after surgery.

Beneficial Effect of Exercise on Cognitive Function during Peripheral Arterial Disease: Potential Involvement of Myokines and Microglial Anti-Inflammatory Phenotype Enhancement

Peripheral arterial disease (PAD), leading to intermittent claudication, critical ischemia with rest pain, and/or tissue damage, is a public health issue associated with significant morbidity and mortality. Little is known about the link between PAD, cognitive function, and whether exercise might reduce cognitive dysfunction in PAD patients, as previously observed concerning both quality of life and prognosis. This review highlights the fact that patients suffering from PAD often demonstrate cognitive dysfunction characterized by reduced performance in nonverbal reasoning, reduced verbal fluency, and decreased information processing speed and a greater risk for progression toward dementia. Further, the data presented support that physical exercise, likely through myokine secretion and microglial anti-inflammatory phenotype enhancement, might participate in the cognition protection in common clinical settings.

Randomized Controlled Trial of Physical Exercise in Diabetic Veterans With Length-Dependent Distal Symmetric Polyneuropathy

Rationale: Physical exercise is an essential adjunct to the management of patients with type 2 diabetes mellitus. Therapeutic interventions that improve blood flow to peripheral nerves, such as exercise, may slow the progression of neuropathy in the diabetic patient.

Aims: This randomized clinical trial was conducted to determine whether a structured program of aerobic, isokinetic strength, or the combination of aerobic–isokinetic strength exercise intervention alters peripheral nerve function in glycemic-controlled diabetic patients with advanced length-dependent distal symmetric polyneuropathy.

Methods: Forty-five patients with type 2 diabetes mellitus exhibiting tight glycemic control (HbA_1c intergroup range 7.2–8.0%) were randomized by block design across four experimental groups: sedentary controls (n = 12), aerobic exercise (n = 11), isokinetic strength (n = 11), or the combination of aerobic–isokinetic strength training (n = 11). Patients randomized to training groups exercised 3× per week for 12 weeks, whereas patients randomized to the sedentary control group received standard of care. To minimize attention and educational bias, all patients attended a 12-session health promotion educational series. At baseline, immediately following intervention, and again at 12-week post-intervention, detailed nerve conduction studies were conducted as a primary outcome measure. At these same intervals, all patients completed as secondary measures quantitative sensory testing, symptom-limited treadmill stress tests, and a Short-Form 36-Veterans Questionnaire (SF-36V).

Results: Of the 45 patients randomized into this study, 37 (82%) had absent sural nerve responses, 19 (42%) had absent median sensory nerve responses, and 17 (38%) had absent ulnar sensory nerve responses. By comparison, responses from tibial nerves were absent in only three (7%) subjects while responses from peroneal nerves were absent in five (11%) subjects. Eleven (92%) of 12 patients that had volunteered to be biopsied exhibited abnormal levels of epidermal nerve fiber densities. Exercise, regardless of type, did not alter sensory or motor nerve electrodiagnostic findings among those patients exhibiting measurable responses (ANOVA). There was, however, a modest (p = 0.01) beneficial effect of exercise on sensory nerve function (Fisher’s Exact Test). Importantly, the beneficial effect of exercise on sensory nerve function was enhanced (p = 0.03) during the post-intervention interval. In addition, three of six patients that had undergone exercise intervention exhibited a marked 1.9 ± 0.3-fold improvement in epidermal nerve fiber density. By comparison, none of three sedentary patients whom agreed to be biopsied a second time showed improvement in epidermal nerve fiber density. Compared to baseline values within groups, and compared with sedentary values across groups, neither aerobic, isokinetic strength, or the combination of aerobic–isokinetic strength exercise intervention altered peak oxygen uptake. Patients that underwent aerobic or the combined aerobic–isokinetic strength exercise intervention, however, demonstrated an increase in treadmill test duration that was sustained over the 12-week post-intervention period.

Conclusion: A 12-week course of physical exercise, regardless of type, does not alter sensory or motor nerve electrodiagnostic findings. In a subset of patients, a short-term structured program of aerobic exercise may selectively improve sensory nerve fiber function. Large-scale exercise lifestyle intervention trials are warranted to further evaluate the impact of aerobic exercise on sensory nerve fiber function in diabetic neuropathic patients.

Clinical Trial Registration:www.ClinicalTrials.gov, identifier NCT00955201.

Neonatal hypoxia-ischemia caused mild motor dysfunction, recovered by acrobatic training, without affecting morphological structures involved in motor control in rats

The aim of this study was to evaluated motor function and morphological aspects of the components involved in motor control (sensorimotor cortex, spinal cord, sciatic nerve, neuromuscular junctions and skeletal muscle) in male Wistar rats exposed to a model of neonatal hypoxic-ischemic encephalopathy (HIE) and the possible influence of different physical exercise protocols - treadmill and acrobatic. Male Wistar rats at the 7^th post-natal day (PND) were submitted to the HIE model and from the 22^nd until 60^th PND the exercise protocols (treadmill or acrobatic training) were running. After the training, the animals were evaluated in Open Field, Ladder Rung Walking and Rotarod tasks and after samples of the motor control components were collected. Our results evidenced that the acrobatic training reversed the hyperactivity and anxiety, caused locomotion improvement and decreased brain atrophy in HIE animals. We did not find morphological differences on sensorimotor cortex, spinal cord, sciatic nerve, neuromuscular junctions and skeletal muscle in the animals submitted to HIE model. These intriguing data support the statement of the Rice-Vannucci model does not seem to reproduce, in structures involved in control function, the damage found in humans that suffer HIE. Regarding the protocols of exercise, we proposed that the acrobatic exercise could be a good therapeutic option especially in children affected by neonatal HIE and can be responsible for good results in cognitive and motor aspects.

Limb Ischemic Conditioning Improved Cognitive Deficits via eNOS-Dependent Augmentation of Angiogenesis after Chronic Cerebral Hypoperfusion in Rats

Intracranial and extracranial arterial stenosis, the primary cause of chronic cerebral hypoperfusion (CCH), is a critical reason for the pathogenesis of vascular dementia and Alzheimer’s disease characterized by cognitive impairments. Our previous study demonstrated that limb remote ischemic conditioning (LRIC) improved cerebral perfusion in intracranial arterial stenosis patients. The current study aimed to test whether LRIC promotes angiogenesis and increases phosphorylated endothelial nitric oxide synthase (p-eNOS) activity in CCH rat model. Adult male Sprague-Dawley rats were randomly assigned to three different groups: sham group, bilateral carotid artery occlusion (2VO) group and 2VO+LRIC group. Cerebral Blood Flow (CBF) was measured with laser speckle contrast imager at 4 weeks. Cognitive testing was performed at four and six weeks after 2VO surgery. We demonstrated that LRIC treatment increased cerebral perfusion and improved the CCH induced spatial learning and memory impairment. Immunohistochemistry confirmed that LRIC prevented cell death in the CA1 region, and increased the number of vessels and angiogenesis in the hippocampus after 2VO. Western blot analysis shows that LRIC therapy significantly increased p-eNOS expression in the hippocampus when compared with 2VO rats. Moreover, eNOS inhibitor reduced the effect of LRIC on angiogenesis in the hippocampus and spatial learning and memory function. Our data suggested that LRIC promoted angiogenesis, which is mediated, in part, by eNOS/NO.

The Neurotropic Parasite Toxoplasma gondii Induces Sustained Neuroinflammation with Microvascular Dysfunction in Infected Mice

Toxoplasmosis is one of the leading parasitic diseases worldwide. Some data suggest that chronic acquired toxoplasmosis could be linked to behavioral alterations in humans. The parasite infects neurons, forming immunologically silent cysts. Cerebral microcirculation homeostasis is determinant to brain functions, and pathologic states can alter capillarity or blood perfusion, leading to neurodegeneration and cognitive deficits. Albino mice were infected with Toxoplasma gondii (ME49 strain) and analyzed after 10, 40, and 180 days. Infected mice presented decreased cerebral blood flow at 10 and 40 days post infection (dpi), which were restored at 180 dpi, as shown by laser speckle contrast imaging. Intravital microscopy demonstrated that infection led to significant capillary rarefaction, accompanied by neuroinflammation, with microglial activation and increased numbers of rolling and adherent leukocytes to the wall of cerebral capillaries. Acetylcholine-induced vasodilation was altered at all time points, and blood brain barrier permeability was evident in infected animals at 40 dpi. Infection reduced angiogenesis, with a decreased number of isolectin B4-stained blood vessels and a decrease in length and branching of laminin-stained capillaries. Sulfadiazine reduced parasite load and partially repaired microvascular damages. We conclude that T. gondii latent infection causes a harmful insult in the brain, promoting neuroinflammation and microcirculatory dysfunction in the brain, with decreased angiogenesis and can contribute to a neurodegenerative process.

Association of Microvascular Dysfunction With Late-Life Depression: A Systematic Review and Meta-analysis

Importance

The etiologic factors of late-life depression are still poorly understood. Recent evidence suggests that microvascular dysfunction is associated with depression, which may have implications for prevention and treatment. However, this association has not been systematically reviewed.

Objective

To examine the associations of peripheral and cerebral microvascular dysfunction with late-life depression.

Data Sources

A systematic literature search was conducted in MEDLINE and EMBASE for and longitudinal studies published since inception to October 16, 2016, that assessed the associations between microvascular dysfunction and depression.

Study Selection

Three independent researchers performed the study selection based on consensus. Inclusion criteria were a study population 40 years of age or older, a validated method of detecting depression, and validated measures of microvascular function.

Data Extraction and Synthesis

This systematic review and meta-analysis has been registered at PROSPERO (CRD42016049158) and is reported in accordance with the PRISMA and MOOSE guidelines. Data extraction was performed by an independent researcher.

Main Outcomes and Measures

The following 5 estimates of microvascular dysfunction were considered in participants with or without depression: plasma markers of endothelial function, albuminuria, measurements of skin and muscle microcirculation, retinal arteriolar and venular diameter, and markers for cerebral small vessel disease. Data are reported as pooled odds ratios (ORs) by use of the generic inverse variance method with the use of random-effects models.

Results

A total of 712 studies were identified; 48 were included in the meta-analysis, of which 8 described longitudinal data. Data from 43 600 participants, 9203 individuals with depression, and 72 441 person-years (mean follow-up, 3.7 years) were available. Higher levels of plasma endothelial biomarkers (soluble intercellular adhesion molecule-1: OR, 1.58; 95% CI, 1.28-1.96), white matter hyperintensities (OR, 1.29; 95% CI, 1.19-1.39), cerebral microbleeds (OR, 1.18; 95% CI, 1.03-1.34), and cerebral (micro)infarctions (OR, 1.30; 95% CI, 1.21-1.39) were associated with depression. Among the studies available, no significant associations of albuminuria and retinal vessel diameters with depression were reported. Longitudinal data showed a significant association of white matter hyperintensities with incident depression (OR, 1.19; 95% CI, 1.09-1.30).

Conclusions and Relevance

This meta-analysis shows that both the peripheral and cerebral forms of microvascular dysfunction are associated with higher odds of (incident) late-life depression. This finding may have clinical implications because microvascular dysfunction might provide a potential target for the prevention and treatment of depression.

Chronic cerebral hypoperfusion independently exacerbates cognitive impairment within the pathopoiesis of Parkinson's disease via microvascular pathologys

To date, the role of microvascular pathology and chronic cerebral hypoperfusion (CHH) in the development of mild cognitive impairment in Parkinson's disease (PD-MCI) is unclear. Here, we investigated how the combined injury through interaction of CHH and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) toxicity act as an exacerbating element to damagae cognitive fuction in a mouse model. In the present study, C57BL/6 mice underwent MPTP injection. Subjects were classified into a PD with normal cognitive performance (PDCN) group or a PD-MCI group using the Morris Water Maze test. Further, CHH was induced by stenosis of the bilateral common carotid arteries (BCCAs). Consequently, the animals were divided into 7 groups: they are control, sham, BCCAs, PDCN, PD-MCI, PDCN+BCCAs and PD-MCI+BCCAs. The Morris Water Maze test, open field test, histological investigation and western blotting were performed to analyze cerebral microvascular impairment in each group. The results showed that CHH and MPTP injection caused spatial memory and behavioral impairment, accompanied by microvascular impairment and down-regulation of ZO-1 and Occludin at the protein level compared to the control group. The above injuries were synergistically exacerbated in the PDCN+BCCAs group and the PD-MCI+BCCAs group, which paralleled the elevated expression of p-MAPK and p-Akt. In short, our data demonstrate that CHH and MPTP caused cognitive and microvascular impairment separately. Moreover, CHH may exacerbate cognitive impairment in a mouse model of PD. The study provides a new opportunity for understanding the pathogenesis of PD-MCI.