Hydroxymethylglutaryl-CoA reductase activity is essential for mitochondrial ß-oxidation of fatty acids to prevent lethal accumulation of long-chain acylcarnitines in the mouse liver.

BACKGROUND AND PURPOSE: Statins are competitive inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase (HMGCR), and exert adverse effects on mitochondrial function, although the mechanisms underlying these effects remain unclear. We used a tamoxifen-induced Hmgcr-knockout (KO) mouse model, a multi-omics approach and mitochondrial function assessments to investigate whether decreased HMGCR activity impacts key liver energy metabolism pathways. EXPERIMENTAL APPROACH: We established a new mouse strain using the Cre/loxP system, which enabled whole-body deletion of Hmgcr expression. These mice were crossed with Rosa26Cre mice and treated with tamoxifen to delete Hmgcr in all cells. We performed transcriptomic and metabolomic analyses and thus evaluated time-dependent changes in metabolic functions to identify the pathways leading to cell death in Hmgcr-KO mice. KEY RESULTS: Lack of Hmgcr expression resulted in lethality, due to acute liver damage caused by rapid disruption of mitochondrial fatty acid ß-oxidation and very high accumulation of long-chain (LC) acylcarnitines in both male and female mice. Gene expression and KO-related phenotype changes were not observed in other tissues. The progression to liver failure was driven by diminished peroxisome formation, which resulted in impaired mitochondrial and peroxisomal fatty acid metabolism, enhanced glucose utilization and whole-body hypoglycaemia. CONCLUSION AND IMPLICATIONS: Our findings suggest that HMGCR is crucial for maintaining energy metabolism balance, and its activity is necessary for functional mitochondrial ß-oxidation. Moreover, statin-induced adverse reactions might be rescued by the prevention of LC acylcarnitine accumulation.

Is Hippocampal Volume a Relevant Early Marker of Dementia?

OBJECTIVE: Hippocampal volume (HV) is a key imaging marker to improve Alzheimer's disease risk prediction. However, longitudinal studies are rare, and hippocampus may also be implicated in the subtle aging-related cognitive decline observed in dementia-free individuals. Our aim was to determine whether HV, measured by manual or automatic segmentation, is associated with dementia risk and cognitive decline in participants with and without incident dementia. METHODS: At baseline, 510 dementia-free participants from the French longitudinal ESPRIT cohort underwent magnetic resonance imaging. HV was measured by manual and by automatic segmentation (FreeSurfer 6.0). The presence of dementia and cognitive functions were investigated at each follow-up (2, 4, 7, 10, 12, and 15 years). Cox proportional hazards models and linear mixed models were used to assess the association of HV with dementia risk and with cognitive decline, respectively. RESULTS: During the 15-years follow-up, 42 participants developed dementia. Reduced HV (regardless of the measurement method) was significantly associated with higher dementia risk and cognitive decline in the whole sample. However, only the automatically measured HV was associated with cognitive decline in dementia-free participants. CONCLUSION: These results suggest that HV can be used to predict the long-term risk of dementia but also cognitive decline in a dementia-free population. This raises the question of the relevance of HV measurement as an early marker of dementia in the general population.

The Effects of Statins on Cognitive Performance Are Mediated by Low-Density Lipoprotein, C-Reactive Protein, and Blood Glucose Concentrations.

Statins are widely used for cardiovascular disease prevention but their effects on cognition remain unclear. Statins reduce cholesterol concentration and have been suggested to provide both beneficial and detrimental effects. Our aim was to investigate the cross-sectional and longitudinal association between statin use and cognitive performance, and whether blood low-density lipoprotein, high-density lipoprotein, triglycerides, glucose, C-reactive protein, and vitamin D biomarkers mediated this association. We used participants from the UK biobank aged 40-69 without neurological and psychiatric disorders (n = 147 502 and n = 24 355, respectively). We performed linear regression to evaluate the association between statin use and cognitive performance and, mediation analysis to quantify the total, direct, indirect effects and the proportion meditated by blood biomarkers. Statin use was associated with lower cognitive performance at baseline (ß = -0.40 [-0.53, -0.28], p = <.0001), and this association was mediated by low-density lipoprotein (proportion mediated = 51.4%, p = .002), C-reactive protein (proportion mediated = -11%, p = .006) and blood glucose (proportion mediated = 2.6%, p = .018) concentrations. However, statin use was not associated with cognitive performance, measured 8 years later (ß = -0.003 [-0.11, 0.10], p = .96). Our findings suggest that statins are associated with lower short-term cognitive performance by lowering low-density lipoprotein and raising blood glucose concentrations, and better performance by lowering C-reactive protein concentrations. In contrast, statins have no effect on long-term cognition and remain beneficial in reducing cardiovascular risk factors.

Statins and cognition: Modifying factors and possible underlying mechanisms.

Statins are a class of widely prescribed drugs used to reduce low-density lipoprotein cholesterol (LDL-C) and important to prevent cardiovascular diseases (CVD). Most statin users are older adults with CVD, who are also at high risk of cognitive decline. It has been suggested that statins can alter cognitive performance, although their positive or negative effects are still debated. With more than 200 million people on statin therapy worldwide, it is crucial to understand the reasons behind discrepancies in the results of these studies. Here, we review the effects of statins on cognitive function and their association with different etiologies of dementia, and particularly, Alzheimer's disease (AD). First, we summarized the main individual and statin-related factors that could modify the cognitive effects of statins. Second, we proposed the underlying mechanisms for the protective and adverse effects of statins on cognitive performance. Finally, we discussed potential causes of discrepancies between studies and suggested approaches to improve future studies assessing the impact of statins on dementia risk and cognitive function.

Glucometabolic Changes Are Associated with Structural Gray Matter Alterations in Prodromal Dementia.

BACKGROUND: Glucometabolic changes, such as high glycemic load (GL) diet and insulin resistance (IR), are potential risk factor of Alzheimer's disease (AD). Yet, the effect of these factors on brain alterations that contribute to AD pathology has not been clearly demonstrated. OBJECTIVE: We aimed to assess the relationship of GL and IR with gray matter volumes involved in prodromal dementia. METHODS: GL and Triglyceride-Glucose (TyG) index, an IR surrogate marker, were calculated in 497 participants who underwent magnetic resonance imaging (MRI). The gray matter volumes most related to prodromal dementia/mild cognitive impairment (diagnosed in 18/158 participants during the 7-year follow-up) were identified using a data-driven machine learning algorithm. RESULTS: Higher GL diet was associated with reduced amygdala volume. The TyG index was negatively associated with the hippocampus, amygdala, and putamen volumes. CONCLUSION: These results suggest that GL and IR are associated with lower gray matter volumes in brain regions involved in AD pathology.

Dietary Glycemic Load and Plasma Amyloid-ß Biomarkers of Alzheimer's Disease.

Previous studies have highlighted links between a high-glycemic-load (GL) diet and Alzheimer's disease in apolipoprotein E ε4 (APOE4) carriers. However, the impact of high-GL diet on plasma amyloid-ß (Aß), an Alzheimer's disease hallmark that can be detected decades before clinical symptomatology, is unknown. This study examined the association between plasma Aß peptides (Aß40, Aß42 concentration and Aß42/Aß40 ratio) and GL. The influence of the GL of four meal types (breakfast, lunch, afternoon snack, and dinner) was also determined. From the prospective Three-City study, 377 participants with plasma Aß measurements, and who completed the Food Frequency Questionnaire, were selected. The association between plasma Aß and GL was tested using an adjusted linear regression model. Lunch GL was associated with a lower plasma Aß42 concentration (ß = -2.2 [CI = -4.27, -0.12], p = 0.038) and lower Aß42/Aß40 ratio (ß = -0.009 [CI = -0.0172, -0.0007], p = 0.034) in the model adjusted for center, age, sex, education level, APOE4 status, energy intake, serum creatinine, total cholesterol, and Mediterranean-like diet. No significant association was found with the GL of the other meal types. These results suggest that dietary GL may independently modulate the plasma Aß of the APOE4 status. The mechanism underlying diet, metabolic response, and Aß peptide regulation must be elucidated.

Simple Carbohydrate Intake and Higher Risk for Physical Frailty Over 15 Years in Community-Dwelling Older Adults.

Insulin resistance is a major mechanism involved in the onset of physical frailty (PF). Although rich carbohydrate diets may promote insulin resistance, few studies have examined their association with PF risk. This study aimed to investigate the spectrum of carbohydrate exposure, including carbohydrate intake (simple, complex, and total), glycemic load (a measure of the diet-related insulin demand), and adherence to a low-carbohydrate diet with the incident risk of PF in community-dwelling older adults. Baseline carbohydrate exposure was assessed in nonfrail participants of the Three-City Bordeaux cohort using a 24-hour dietary recall. Over 15 years of follow-up, participants were screened for PF, defined by the FRAIL scale (≥3 criteria out of Fatigue, Resistance, Ambulation, Illnesses, and weight Loss). Associations were estimated using mixed-effects logistic models adjusted for sex, age, education, smoking status, alcohol consumption, depressive symptomatology, global cognitive performances, and protein and energy intakes. The sample included 1 210 participants (62% females, mean age 76 years). Over the follow-up, 295 (24%) incident cases of PF were documented (28% in females, 18% in males). Higher intake of simple carbohydrates was significantly associated with greater odds of incident PF (per 1-SD increased: OR = 1.29; 95% CI = 1.02-1.62), specifically among males (OR = 1.52; 95% CI = 1.04-2.22). No association was observed with complex or total carbohydrate intake, glycemic load, or low-carbohydrate diet. Among the whole carbohydrate exposure, only higher consumption of simple carbohydrates in older age was associated with a higher risk of developing PF. Further studies are required to explore underlying mechanisms.

Late-life cynical hostility is associated with white matter alterations and the risk of Alzheimer's disease.

BACKGROUND: Cynical hostility (CH), a specific dimension of hostility that consists of a mistrust of others, has been suggested as a high-risk trait for dementia. However, the influence of CH on the incidence of Alzheimer's disease (AD) remains poorly understood. This study investigated whether late-life CH is associated with AD risk and structural neuroimaging markers of AD. METHODS: In community-dwelling older adults from the French ESPRIT cohort (n = 1388), incident dementia rate according to CH level was monitored during an 8-year follow-up and analyzed using Cox proportional hazards regression models. Brain magnetic resonance imaging volumes were measured at baseline (n = 508). Using automated segmentation procedures (Freesurfer 6.0), the authors assessed brain grey and white volumes on all magnetic resonance imaging scans. They also measured white matter hyperintensities volumes using semi-automated procedures. Mean volumes according to the level of CH were compared using ANOVA. RESULTS: Eighty-four participants developed dementia (32 with AD). After controlling for potential confounders, high CH was predictive of AD (HR 2.74; 95% CI 1.10-6.85; p = 0.030) and all dementia types are taken together (HR 2.30; 95% CI 1.10-4.80; p = 0.027). High CH was associated with white matter alterations, particularly smaller anterior corpus callosum volume (p < 0.01) after False Discovery Rate correction, but not with grey matter volumes. CONCLUSIONS: High CH in late life is associated with cerebral white matter alterations, designated as early markers of dementia, and higher AD risk. Identifying lifestyle and biological determinants related to CH could provide clues on AD physiopathology and avenues for prevention strategies.

High Glycemic Load Is Associated with Cognitive Decline in Apolipoprotein E ε4 Allele Carriers.

Recent evidence suggests that a high glycemic load (GL) diet is a risk factor for dementia, especially among apolipoprotein E ε4 allele (APOE4) carriers, while its association with cognitive decline is poorly known. Here, we investigated the association of high-GL meals with cognitive decline in older adults during a 12-year follow-up, according to their APOE4 carrier status. We used random-effect models and data from 2539 elderly participants from the Three-City study who completed a food frequency questionnaire (FFQ) to longitudinally assess the association of GL with changes in different cognitive domains (verbal fluency, visual memory, attention, visual motor processing speed, episodic memory). In APOE4 carriers, afternoon snack with high GL was significantly associated with cognitive decline in visual memory, episodic memory, and global cognition compared with APOE4 non-carriers. This study suggests a detrimental association between a high-GL diet and cognitive decline. The promotion of a low GL diet as a target to prevent cognitive decline in high-risk populations deserves more research.

Refined carbohydrate-rich diet is associated with long-term risk of dementia and Alzheimer's disease in apolipoprotein E ε4 allele carriers.

INTRODUCTION: In animal models, refined carbohydrates (RF) worsen Alzheimer's disease (AD). However, the long-term effects of high RF intake on the risk of dementia and AD are poorly described in epidemiological studies. Moreover, the interaction between RF and the apolipoprotein E ε4 allele (APOE-ε4) is unknown. Our study investigated whether RF-rich diets are associated with the risk of dementia and AD. METHODS: The glycemic load (GL) was quantified in 2777 elderly participants from the French Three-City Study to estimate RF intake. Then, the associations between GL and risk of dementia and AD, and the interaction with APOE-ε4 over a 12-year period were assessed using proportional hazards models. RESULTS: After adjustment for potential confounders, high afternoon-snack GL was associated with increased dementia and AD risk in APOE-ε4 carriers (hazard ratio = 1.27 [1.03-1.56]). DISCUSSION: This study highlights that RF-rich diets are a risk factor for dementia and AD in APOE-ε4 carriers.