Carotid Flow Velocities and Blood Pressures Are Independently Associated With Cognitive Function

Aged Mouse Hippocampus Exhibits Signs of Chronic Hypoxia and an Impaired HIF-Controlled Response to Acute Hypoxic Exposures

Altered hypoxia-inducible factor-alpha (HIF-α) activity may have significant consequences in the hippocampus, which mediates declarative memory, has limited vascularization, and is vulnerable to hypoxic insults. Previous studies have reported that neurovascular coupling is reduced in aged brains and that diseases which cause hypoxia increase with age, which may render the hippocampus susceptible to acute hypoxia. Most studies have investigated the actions of HIF-α in aging cortical structures, but few have focused on the role of HIF-α within aged hippocampus. This study tests the hypothesis that aging is associated with impaired hippocampal HIF-α activity. Dorsal hippocampal sections from mice aged 3, 9, 18, and 24 months were probed for the presence of HIF-α isoforms or their associated gene products using immunohistochemistry and fluorescent in situ hybridization (fISH). A subset of each age was exposed to acute hypoxia (8% oxygen) for 3 h to investigate changes in the responsiveness of HIF-α to hypoxia. Basal mean intensity of fluorescently labeled HIF-1α protein increases with age in the hippocampus, whereas HIF-2α intensity only increases in the 24-month group. Acute hypoxic elevation of HIF-1α is lost with aging and is reversed in the 24-month group. fISH reveals that glycolytic genes induced by HIF-1α (lactose dehydrogenase-a, phosphoglycerate kinase 1, and pyruvate dehydrogenase kinase 1) are lower in aged hippocampus than in 3-month hippocampus, and mRNA for monocarboxylate transporter 1, a lactose transporter, increases. These results indicate that lactate, used in neurotransmission, may be limited in aged hippocampus, concurrent with impaired HIF-α response to hypoxic events. Therefore, impaired HIF-α may contribute to age-associated cognitive decline during hypoxic events.

Differential association of flow velocities in the carotid artery with plaques, intima media thickness and cardiac function

Background and aims

We aimed to determine the association of carotid intima media thickness (CIMT), carotid plaques, and heart function with peak systolic velocity (PSV) of the common (CCA) and internal carotid artery (ICA) in a cross-sectional study.

Methods

In the population-based Hamburg-City-Health-Study participants between 45 and 74 years were recruited. Cardio-vascular risk factors were assessed by history, blood samples, and clinical examination. CIMT, plaques, and PSV were determined by carotid ultrasound. Serum N-terminal brain natriuretic peptide (NT-proBNP) was determined as a biomarker for cardiac dysfunction, and left ventricular ejection fraction (LVEF) was quantified by echocardiography. Participants with carotid stenosis were excluded. Data were analyzed by multivariate linear regression.

Results

We included 8567 participants, median age was 62 years, 51.8% were women. Median CIMT was 0.75 mm, NT-proBNP 80 pg/ml, LVEF 58.5%, and 30.4% had carotid plaques. For women PSV decreased in decades from 89 to 73 cm/s in CCAs and 78 to 66 cm/s in ICAs, and for men from 91 to 76 cm/s in CCAs and from 70 to 66 cm/s in ICAs. Corrected for age, sex, red blood cell count, and blood pressure, in CCAs lower PSV was associated with carotid plaques (p < 0.001; β = -0.03), lower CIMT (p = 0.005; β = 0.007), higher levels of log-transformed NT-proBNP (p < 0.001; β = -0.01), and lower LVEF (p < 0.001; β = 0.01). In ICAs, lower PSV was independently associated with lower CIMT (p < 0.001; β = 0.02) and lower EF (p = 0.001; β = 0.007).

Conclusions

Markers of cardiac dysfunction and plaques are associated with lower and CIMT with higher flow velocities in the carotid arteries.

Clinical Trial Registration

http://www.clinicaltrials.gov, NCT03934957.

The association between carotid blood flow and resting-state brain activity in patients with cerebrovascular diseases

Cerebral hypoperfusion impairs brain activity and leads to cognitive impairment. Left and right common carotid arteries (CCA) are the major source of cerebral blood supply. It remains unclear whether blood flow in both CCA contributes equally to brain activity. Here, CCA blood flow was evaluated using ultrasonography in 23 patients with cerebrovascular diseases. Resting-state brain activity and cognitive status were also assessed using magnetoencephalography and a cognitive subscale of the Functional Independence Measure, respectively, to explore the relationships between blood flow, functional brain activity, and cognitive status. Our findings indicated that there was an association between blood flow and resting-state brain activity, and between resting-state brain activity and cognitive status. However, blood flow was not significantly associated with cognitive status directly. Furthermore, blood velocity in the right CCA correlated with resting-state brain activity, but not with the resistance index. In contrast, the resistance index in the left CCA correlated with resting-state brain activity, but not with blood velocity. Our findings suggest that hypoperfusion is important in the right CCA, whereas cerebral microcirculation is important in the left CCA for brain activity. Hence, this asymmetry should be considered when designing appropriate therapeutic strategies.

Associations of Blood Pressure and Carotid Flow Velocity with Brain Volume and Cerebral Small Vessel Disease in a Community-Based Population

Cerebral small vessel disease (CSVD) is a common finding on brain magnetic resonance imaging (MRI). We previously demonstrated that high blood pressure (BP) and low carotid flow velocity were associated with cerebrovascular disease. However, their associations with brain volume and CSVD remain to be determined. A total of 721 adults (≥ 50 years) from the community-based I-Lan Longitudinal Aging Study were included. Flow velocities at the common (CCA) and internal carotid artery (ICA), including peak systolic velocity (PSV) and end-diastolic velocity (EDV), were measured with Doppler ultrasound. We further detected the presence of CSVD including lacune, microbleed, and white matter hyperintensity (WMH) on brain MRI, which were used to construct a combined CSVD score. General linear regression and logistic regression analysis were exploited to evaluate the association between carotid flow velocity, BP, brain volume, and CSVD. The mean of white matter, gray matter, and WMH volume were 422.2 cm³, 546.9 cm³, and 2.61 cm³, respectively. The proportion of lacune and microbleed were 11.1% and 14.2%, respectively. The CSVD score were negatively associated with gray (r = - 0.121, p < .01) and white matter volume (r = 0.058, p = 0.12), but positively associated with systolic BP (beta = 1.02, p = 0.0017). EDV at common carotid artery associated positively with white matter volume (beta = 1.013, p = 0.0064) and negatively predicted the presence CSVD (odds ratio [OR] = 0.93, p = 0.0023). In the ordinal logistic regression analysis adjusting for age, sex, total intracranial volume education, low-density lipoprotein cholesterol, and fasting glucose, compared with hypertensive subjects with low EDV, normotensive subjects with low, middle, and high EDV had an odds ratio of 0.656 (0.327-1.318), 0.429 (0.261-0.705), and 0.272 (0.147-0.502) for CSVD score, respectively. High SBP and low carotid flow velocities were independently associated with brain volume and CSVD. These associations may be involved in the pathophysiology of cognitive function decline.

Common carotid flow velocity is associated with cognitive function after carotid endarterectomy

The relationship between ultrasonographic flow parameters and cognitive function has not been well studied. This study aimed to clarify associations between carotid flow velocity (FV) and cognitive function in patients with a history of carotid endarterectomy (CEA). Ninety-four patients who previously underwent CEA participated in this study. The Neurobehavioral Cognitive Status Examination (Cognistat) and Frontal Assessment Battery (FAB) were adopted to assess cognitive functions at a mean of 6.5 ± 3.2 years after CEA. End-diastolic flow velocity (EDV) of the left and right common carotid artery (CCA) was significantly associated with total Cognistat score (p < 0.001) and total FAB score (p < 0.05). Pulsatility index (PI) of the left CCA was significantly associated with total Cognistat score and total FAB score (p < 0.01). A cut-off right CCA EDV of 14.5 cm/s offered the most reliable predictor of the bottom 25th percentile of total Cognistat score (sensitivity 83.3%, specificity 61.0%, area under the curve (AUC) 0.731, p = 0.0060), while a cut-off left CCA PI of 1.83 was the most reliable predictor of the bottom 25th percentile of total FAB score (sensitivity 73.3%, specificity 60.0%, AUC 0.679, p = 0.0179). Left and right CCA EDV correlated with sub-components of comprehension, construction, judgment, programming (p < 0.01), and conceptualization (p < 0.05). Right CCA EDV correlated with similarity (p < 0.01), repetition, naming, and memory (p < 0.05). Left CCA PI correlated with attention, conceptualization (p < 0.01), repetition, construction, similarity, and mental flexibility (p < 0.05), while right CCA PI correlated with construction (p < 0.05). CCA FV may offer useful markers of cognitive functions in patients with a history of CEA.