Effects of Heart Bypass Surgery on Plasma Aβ40 and Aβ42 Levels in Infants and Young Children

Role of monomeric amyloid-β in cognitive performance in Alzheimer's disease: Insights from clinical trials with secretase inhibitors and monoclonal antibodies

According to the β-amyloid (Aβ) hypothesis of Alzheimer's disease (AD), brain Aβ accumulation is the primary cascade event leading to cognitive deficit and dementia. Numerous anti-Aβ drugs either inhibiting production or aggregation of Aβ or stimulating its clearance have failed to show clinical benefit in large scale AD trials, with β- and γ-secretase inhibitors consistently worsening cognitive and clinical decline. In June 2021, the FDA approved aducanumab, an anti-Aβ monoclonal antibody for early AD based on its ability to reduce brain amyloid plaques, while two other amyloid-clearing antibodies (lecanemab and donanemab) have recently produced encouraging cognitive and clinical results. We reviewed AD trials using PubMed, meeting abstracts and ClinicalTrials.gov and evaluated the effects of such drugs on cerebrospinal fluid (CSF) Aβ levels, correlating them with cognitive effects. We found that β-secretase and γ-secretase inhibitors produce detrimental cognitive effects by significantly reducing CSF Aβ levels. We speculate that monoclonal antibodies targeting Aβ protofibrils, fibrils or plaques may improve cognitive performance in early AD by increasing soluble Aβ levels through Aβ aggregate disassembly and/or stabilization of existing Aβ monomers.These findings suggest that the real culprit in AD may be decreased levels of soluble monomeric Aβ due to sequestration into brain Aβ aggregates and plaques.

Predictors and occurrence of postoperative cognitive dysfunction in children undergoing noncardiac surgery: A prospective cohort study

In children after cardiac surgery, alterations in cognitive ability and behavior are increasingly common, but whether postoperative cognitive dysfunction (POCD) occurs in children undergoing noncardiac surgery is not known. The present study was performed to investigate the incidence rate and potential risk factors of early neurocognitive dysfunction in children after noncardiac surgery. Two hundred patients aged between 4 and 14 years old underwent elective noncardiac surgery and 100 healthy age-matched controls were enrolled in this prospective observational study. Wechsler Preschool and Primary Scale of Intelligence or Wechsler Intelligence Scale for Children-Revised were conducted 1 day before and 3 days after surgery. POCD was calculated and diagnosed as a combined Z score. Any factors that differed between POCD and non-POCD group (p < 0.10) were tested together by multivariate logistic regression analysis against the cognitive outcome of patients, to find out the independent risk factors of POCD. The general incidence of POCD was 15.6%. The univariate analysis revealed that POCD was associated with general anesthesia, surgical and anesthesia duration, early postoperative fever (EPF), and surgical history. However, only the history of surgery (p = 0.029), anesthesia duration (p = 0.010), and EPF (p < 0.001) were demonstrated to be independent risk factors for POCD. The occurrence rate of early POCD after noncardiac surgery in children is 15.6%. Children who had surgical history, longer anesthesia duration, or EPF are more prone to develop POCD.

Is postoperative cognitive decline after cardiac surgery associated with plasma beta amyloid 1-42 levels?

Background

Postoperative cognitive decline following cardiac surgery is one of the frequently reported complications affecting postoperative outcome, characterized by impairment of memory or concentration. The aetiology is considered multifactorial and the research conducted so far has presented contradictory results. The proposed mechanisms to explain the cognitive decline associated with cardiac surgery include the neurotoxic accumulation of β-amyloid (Aβ) proteins similar to Alzheimer's disease. The comparison of coronary artery bypass grafting procedures concerning postoperative cognitive decline and plasmatic Aβ1-42 concentrations has not yet been conducted.

Methods

The research was designed as a controlled clinical study of patients with coronary artery disease undergoing surgical myocardial revascularization with or without the use of a cardiopulmonary bypass machine. All patients completed a battery of neuropsychological tests and plasmatic Aβ1-42 concentrations were collected.

Results

The neuropsychological test results postoperatively were significantly worse in the cardiopulmonary bypass group and the patients had larger shifts in the Aβ1-42 preoperative and postoperative values than the group in which off-pump coronary artery bypass was performed.

Conclusions

The conducted research confirmed the earlier suspected association of plasmatic Aβ1-42 concentration to postoperative cognitive decline and the results further showed that there were less changes and lower concentrations in the off-pump coronary artery bypass group, which correlated to less neurocognitive decline. There is a lot of clinical contribution acquired by this research, not only in everyday decision making and using amyloid proteins as biomarkers, but also in the development and application of non-pharmacological and pharmacological neuroprotective strategies.

Anti-amyloid-β protein agents for the treatment of Alzheimer's disease: an update on emerging drugs

INTRODUCTION

Currently available Alzheimer's disease (AD) therapeutics are only symptomatic, targeting cholinergic and glutamatergic neurotransmissions. Several putative disease-modifying drugs in late-stage clinical development target amyloid-β (Aβ) peptide and tau protein, the principal neurophatological hallmarks of the disease.

AREAS COVERED

Phase III randomized clinical trials of anti-Aβ drugs for AD treatment were searched in US and EU clinical trial registries and principal biomedical databases until May 2020.

EXPERT OPINION

At present, compounds in Phase III clinical development for AD include four  anti-Ab monoclonal antibodies (solanezumab, gantenerumab, aducanumab, BAN2401), the combination of cromolyn sodium and ibuprofen (ALZT-OP1), and two small molecules (levetiracetam, GV-971). These drugs are mainly being tested in subjects during early AD phases or at preclinical stage of familial AD or even in asymptomatic subjects at high risk of developing AD. The actual results support the hypothesis that elevated Aβ represents an early stage in the AD continuum and demonstrate the feasibility of enrolling these high-risk participants in secondary prevention trials to slow cognitive decline during the AD preclinical stages. However, a series of clinical failures may question further development of Aβ-targeting drugs and the findings from current ongoing Phase III trials will hopefully give light to this critical issue.

Plasma amyloid beta level changes in aged mice with cognitive dysfunction following sevoflurane exposure

INTRODUCTION

Previous studies have stated that cognitive impairment induced by anesthetics was associated with amyloid beta (Aβ). However, few researchers have investigated the transport of Aβ inside and outside of the brain.

AIM

We attempted to probe the effects of sevoflurane on cognitive functions, the plasma Aβ, and transporters of Aβ in aged mice. The receptor for advanced glycation end-products (RAGE) is an Aβ influx protein, and Low-density lipoprotein receptor-related protein-1 (LRP-1) is an Aβ efflux protein.

METHODS

Aged mice were divided into the control group and the sevoflurane group. The mice were exposed to 100% oxygen or 2.5% sevoflurane for 2 h. The abilities of spatial learning and memory in mice were tested using the Morris water maze. Aβ concentrations of plasma were measured with enzyme-linked immunosorbent assay kits. The RAGE and LRP-1 gene levels in the brain were assessed with quantitative polymerase chain reaction, and the protein levels were determined by western blot analysis. The locations of RAGE in the brain were confirmed via immunofluorescence.

RESULTS

In the sevoflurane group mice, the escape latency was increased on the 5th day of training, and the time spent in the target quadrant was decreased on the 7th day after anesthesia. Sevoflurane reduced the concentration of plasma Aβ1-40. In addition, sevoflurane increased both gene and protein levels of RAGE in the brain, and increased RAGE proteins co-localized with the hippocampal vascular endothelial cells.

CONCLUSION

RAGE over-expression in the hippocampal vascular endothelial cells possibly resulted in the excessive transport of the plasma Aβ1-40 into the brain after treatment with sevoflurane, which was associated with sevoflurane-induced cognitive dysfunction in aged mice.

Effect of general anesthesia on serum β-amyloid protein and regional cerebral oxygen saturation of elderly patients after subtotal gastrectomy

The aim of the present study was to investigate the influence of general anesthesia on serum β-amyloid protein (Aβ) and regional cerebral oxygen saturation (rSO₂) of elderly patients after subtotal gastrectomy. From June, 2014 to December, 2015, among 168 patients undergoing subtotal gastrectomy, the Mini-Mental State Examination and Montreal Cognitive Assessment was administered the day prior to surgery and the second and ninth days after the operation. In addition, we administered the tests to 168 healthy adult volunteers (healthy controls) who were treated in our hospital medical center in the same period. Near-infrared spectroscopy technology was used for continuous monitoring of the intraoperative rSO₂, and the mean of intraoperative rSO₂ was then calculated. Of the 168 patients, 28 developed postoperative cognitive dysfunction (POCD) and the remaining 140 patients were normal (control). The ELISA method was used to test the expression levels of serum Aβ in the three groups and statistical analyses were conducted. Serum Aβ level in the POCD group was significantly higher than that in the control and healthy control groups, and the difference was statistically significant (P<0.05). The rSO₂ level in the patients with POCD was significantly lower than the control group (P<0.05). The correlation analysis with Aβ as an independent variable and other factors as dependent variables revealed that the serum Aβ level negatively correlated with rSO₂ (r=-1.6749, P<0.05). The combined Aβ and rSO₂ may be useful for the diagnosis and prevention of POCD after subtotal gastrectomy under general anesthesia.