Serum oxidized low-density lipoprotein level and risk of cognitive impairment in older women

New insight into the role of altered brain cholesterol metabolism in the pathogenesis of AD: A unifying cholesterol hypothesis and new therapeutic approach for AD

The dysregulation of cholesterol metabolism homeostasis has been universally suggested in the aeotiology of Alzheimer's disease (AD). Initially, studies indicate that alteration of serum cholesterol level might contribute to AD. However, because blood-brain barrier impedes entry of plasma cholesterol, brain cells are not directly influenced by plasma cholesterol. Furthermore, mounting evidences suggest a link between alteration of brain cholesterol metabolism and AD. Interestingly, Amyloid-β proteins (Aβ) can markedly inhibit cellular cholesterol biosynthesis and lower cellular cholesterol content in cultured cells. And Aβ overproduction/overload induces a significant decrease of brain cellular cholesterol content in familial AD (FAD) animals. Importantly, mutations or polymorphisms of genes related to brain cholesterol transportation, such as ApoE4, ATP binding cassette (ABC) transporters, low-density lipoprotein receptor (LDLR) family and Niemann-Pick C disease 1 or 2 (NPC1/2), obviously lead to decreased brain cholesterol transport, resulting in brain cellular cholesterol loss, which could be tightly associated with AD pathological impairments. Additionally, accumulating data show that there are reduction of brain cholesterol biosynthesis and/or disorder of brain cholesterol trafficking in a variety of sporadic AD (SAD) animals and patients. Collectively, compelling evidences indicate that FAD and SAD could share one common and overlapping neurochemical mechanism: brain neuronal/cellular cholesterol deficiency. Therefore, accumulated evidences strongly support a novel hypothesis that deficiency of brain cholesterol contributes to the onset and progression of AD. This review highlights the pivotal role of brain cholesterol deficiency in the pathogenesis of AD. The hypothesis offers valuable insights for the future development of AD treatment.

Effects of Probucol on plasma amyloid-β transport in patients with hyperlipidemia: a 12-week randomized, double-blind, placebo-controlled trial

BACKGROUND

Although dyslipidemia has been acknowledged as a risk factor for Alzheimer's disease (AD), the effects of lipid-lowering drugs on AD have not been determined. The primary pathophysiological hallmark of AD is the deposition of amyloid-β (Aβ) plaques in the brain. Plasma Aβ levels are influenced by the transport of Aβ from the central nervous system to the peripheral blood. This study investigates the effects of Probucol, a lipid-lowering and antioxidant drug, on plasma Aβ transport.

METHODS

A total of 120 hyperlipidemic patients with normal cognition were randomly assigned (1:1 ratio) to receive either Probucol (1000 mg daily for 12 weeks) or a placebo. Plasma Aβ, soluble receptor of advanced glycation end products (sRAGE), and fasting lipid profiles were measured at baseline and every 6 weeks.

RESULTS

A total of 108 participants completed the study, with 55 in the Probucol group. The cohort consisted of 58 (53.7%) women, with a mean age of 58.4 ± 8.0 (range, 45-80) years. After 12 weeks of treatment, the changes in plasma Aβ42 and sRAGE levels significantly differed between the Probucol and placebo groups (ΔAβ42: β = 6.827, P = 0.030; ΔsRAGE: β = 98.668, P = 0.004). Furthermore, ΔsRAGE was positively correlated with the change in Aβ42 (β = 0.018, P = 0.048). When adjusted for ΔsRAGE, the effect of Probucol on plasma Aβ42 levels was attenuated (β = 5.065, P = 0.116). In the Probucol group only, ΔsRAGE was significantly correlated with oxidized low-density lipoproteins (β = 4.27, P = 0.011), total cholesterol (β = 67.50, P = 0.046), and low-density lipoproteins (β = - 91.01, P = 0.011).

CONCLUSIONS

Daily oral administration of Probucol (1000 mg) for 12 weeks significantly increased plasma Aβ42 levels, likely through modulation of sRAGE. This effect may be attributed to the antioxidant and lipid-lowering properties of Probucol. These findings suggest that Probucol could potentially serve as a protective agent against the pathological processes of AD.

TRIAL REGISTRATION

This study was registered on the Chinese Clinical Trial Registry platform in June 2019 (Trial registration number: ChiCTR-1900023542).

Association of Hyperlipidemia and Hyperglycemia With Cognitive Function in Type 2 Diabetes: A Cross-Sectional Analysis

Introduction Cognitive impairment is increasingly recognized as a significant health concern, particularly in the early stages of diabetes. The type and severity of cognitive deficits may vary with the duration of diabetes and the effectiveness of glucose management. Complications associated with metabolic syndrome may exacerbate these cognitive declines. This study investigates the association of hyperlipidemia and hyperglycemia with cognitive function in patients with type 2 diabetes (T2D). Methods We conducted a cross-sectional study on type 2 diabetic patients aged between 30 and 40 years of age and having the disease for less than 10 years duration. We collected anthropometric measurements, tested glycated hemoglobin (HbA1c) and fasting lipid profiles, and assessed cognitive function using the Montreal Cognitive Assessment (MoCA). Results All participants exhibited elevated HbA1c levels and abnormal lipid profiles. We observed weak positive correlations between the duration of diabetes and low-density lipoprotein cholesterol (LDL; 0.448), very low-density lipoprotein cholesterol (VLDL; 0.398), total cholesterol (0.526), and HbA1c (0.360). There were moderately negative correlations between the duration of diabetes and MoCA scores (-0.522) and weak negative correlations between LDL and MoCA (-0.304), VLDL and MoCA (-0.259), and total cholesterol and MoCA (-0.409). The correlation between HbA1c and MoCA was also moderately negative (-0.779). Regression analysis revealed statistically significant associations of MoCA with the duration of diabetes, HbA1c, and lipid parameters, with HbA1c being the largest contributor to cognitive decline at 60.66%, while the contributions of various lipid parameters were considerably lower (LDL: R² = 0.092, VLDL: R² = 0.067, total cholesterol: R² = 0.167). The contribution of the duration of diabetes (R² = 0.272) to cognitive decline was less than that of HbA1c but more than the lipid parameters. Conclusions The findings suggest that hyperglycemia and the duration of diabetes are the major factors contributing to cognitive decline in patients with T2D. Patients should be advised to maintain optimal glycemic control and engage in activities that enhance cognitive function to prevent cognitive impairment. Regular cognitive screening for diabetic patients is also recommended.

The gender- and age- dependent relationships between serum lipids and cognitive impairment: a cross-sectional study in a rural area of Xi'an, China

Background

Serum lipids [total cholesterol (TC), low density lipoprotein cholesterol (LDL-C), high density lipoprotein cholesterol (HDL-C) and triglyceride (TG)] are risk factors for stroke, but the relationships between serum lipids and cognitive impairment have not been verified completely. In this study, we studied the relationships between serum lipids and cognitive impairment and explored whether gender and age had effects on the relationships.

Methods

In this cross-sectional study, we collected serum lipids and cognitive function information from 1762 participants (aged 40–85). Univariate analysis, multivariate analysis, and both gender- and age-based stratified multivariate analysis were used.

Results

In the entire sample set, there was no significant correlation between serum lipid parameters (TC, LDL-C, HDL-C and TG) and cognitive impairment. In both gender- and age-based stratified multivariate analysis, high serum TC was positively associated with cognitive impairment in the elderly (> 55) male participants (OR = 4.404, 95% CI = 1.264–15.344, p = 0.02), and high serum LDL-C was positively correlated with cognitive impairment in the elderly female subjects (OR = 2.496, 95% CI = 1.057–5.896, p = 0.037), while high serum TG was negatively associated with cognitive impairment in the middle-aged (≤ 55) male participants (OR = 0.157, 95% CI = 0.051–0.484, p = 0.001).

Conclusions

The relationships between serum lipids and cognitive impairment are gender- and age- dependent, with high serum TC and LDL-C may be risk factors of cognitive impairment in the elderly male and female subjects respectively, while high serum TG may be protector of cognitive impairment in the middle-aged male participants.

Serum low-density lipoprotein levels, statin use, and cognition in patients with coronary artery disease

AIM

Statins have been associated with decreased cognition due to the effects of low concentrations of low-density lipoprotein (LDL) on brain function. This has remained controversial and is particularly relevant to patients with coronary artery disease (CAD), who have an increased risk of cognitive decline and are frequently prescribed statins. This study hypothesized that low concentration of LDL is associated with poor cognition in CAD patients using statins. It also explored the association between high-dose versus low-dose statins on cognition in this population.

PATIENTS AND METHODS

Baseline cross-sectional data from a longitudinal study of 120 statin-using CAD patients were examined (mean statin duration 25±43 months). The main outcomes were measures of global cognition and cognitive domains, with poor cognition defined as cognitive performance ≤1 standard deviation below the population age and education adjusted means. A battery of cognitive tests was used to assess verbal memory, executive function, speed of processing, visuospatial memory, and global cognition. Adjusting for age, sex, education, and other covariates, multivariable logistic regression analyses assessed associations between low LDL levels (<1.5 mmol/L), statin use, and poor cognition.

RESULTS

LDL levels were not associated with global cognition or individual cognitive domains. High-dose statin use was associated with higher visuospatial memory (odds ratio, OR [95% confidence interval, CI] =0.12 [0.02-0.66], P=0.01) and executive functioning (OR =0.25 [0.06-0.99], P=0.05). This effect was independent of covariates such as LDL levels.

CONCLUSION

Low LDL levels do not appear to be associated with poor cognition in CAD patients using statins. Whether high-dose statin use may have positive effects on cognition in CAD patients could be investigated in future studies.

Vascular risk factors and mild cognitive impairment in the elderly population in Southwest China

OBJECTIVES

Increasing evidence has demonstrated that vascular risk factors (VRFs) contribute to cognitive impairment in the elderly population. Prevention and administration of VRFs can be a vital strategy for delaying cognitive impairment. This study aimed to determine the impact of VRFs on cognitive function of the aged people from Chongqing, Southwest China.

METHODS

A total of 597 participants (≥60 years) from hospital and community population were enrolled in the cross-sectional study. Participants were screened for hypertension, coronary heart disease (CHD), and cerebrovascular disease (CVD). Blood pressure (BP) and blood lipid were also measured. Cognitive function was assessed with Mini-Mental State Examination and Clinical Dementia Rating. Logistic regression analysis was used to look for VRFs impacting mild cognitive impairment (MCI). Then we investigated the relationship between different types of vascular diseases and MCI.

RESULTS

A total of 457 participants showed normal cognitive function and 140 participants showed MCI. After adjusting for age, gender, and education, logistic regression analysis demonstrated that hypertension, CHD, systolic BP, total cholesterol (TC), and low-density lipoprotein cholesterol (LDL-C) were independently associated with MCI; however, CVD, diastolic BP, triglyceride, and high-density lipoprotein cholesterol were not associated with MCI. Moreover, vascular diseases significantly contributed to MCI compared with no vascular disease; however, no significant difference in incident MCI was found among different combinations of vascular diseases.

CONCLUSIONS

Hypertension, CHD, TC, and LDL-C are independent risk factors for MCI. Moreover, patients with vascular diseases have a higher risk of MCI; however, the amount of vascular diseases does not increase the risk of MCI.