Case-cohort study of plasma phospholipid fatty acid profiles, cognitive function, and risk of dementia: a secondary analysis in the Ginkgo Evaluation of Memory Study

Associations of circulating saturated long-chain fatty acids with risk of mild cognitive impairment and Alzheimer's disease in the Alzheimer's Disease Neuroimaging Initiative (ADNI) cohort

BACKGROUND

No study has examined the associations between peripheral saturated long-chain fatty acids (LCFAs) and conversion from mild cognitive impairment (MCI) to Alzheimer's disease (AD). This study aimed to examine whether circulating saturated LCFAs are associated with both risks of incident MCI from cognitively normal (CN) participants and incident AD progressed from MCI in the Alzheimer's Disease Neuroimaging Initiative (ADNI) cohort.

METHODS

We conducted analysis of data from older adults aged 55-90 years who were recruited at 63 sites across the USA and Canada. We examined associations between circulating saturated LCFAs (i.e., C14:0, C16:0, C18:0, C20:0) and risk for incident MCI in CN participants, and incident AD progressed from MCI.

FINDINGS

829 participants who were enrolled in ADNI-1 had data on plasma saturated LCFAs, of which 618 AD-free participants were included in our analysis (226 with normal cognition and 392 with MCI; 60.2% were men). Cox proportional-hazards models were used to account for time-to-event/censor with a 48-month follow-up period for the primary analysis. Other than C20:0, saturated LCFAs were associated with an increased risk for AD among participants with MCI at baseline (Hazard ratios (HRs) = 1.3 to 2.2, P = 0.0005 to 0.003 in fully-adjusted models). No association of C20:0 with risk of AD among participants with MCI was observed. No associations were observed between saturated LCFAs and risk for MCI among participants with normal cognition.

INTERPRETATION

Saturated LCFAs are associated with increased risk of progressing from MCI to AD. This finding holds the potential to facilitate precision prevention of AD among patients with MCI.

FUNDING

National Institutes of Health.

Nutrition in Alzheimer's disease: a review of an underappreciated pathophysiological mechanism

Alzheimer's disease (AD) is the leading cause of dementia in older individuals and is an escalating challenge to global public health. Pharmacy therapy of AD is one of the well-funded areas; however, little progress has been made due to the complex pathogenesis. Recent evidence has demonstrated that modifying risk factors and lifestyle may prevent or delay the incidence of AD by 40%, which suggests that the management should pivot from single pharmacotherapy toward a multipronged approach because AD is a complex and multifaceted disease. Recently, the gut-microbiota-brain axis has gained tremendous traction in the pathogenesis of AD through bidirectional communication with multiple neural, immune, and metabolic pathways, providing new insights into novel therapeutic strategies. Dietary nutrition is an important and profound environmental factor that influences the composition and function of the microbiota. The Nutrition for Dementia Prevention Working Group recently found that dietary nutrition can affect cognition in AD-related dementia directly or indirectly through complex interactions of behavioral, genetic, systemic, and brain factors. Thus, considering the multiple etiologies of AD, nutrition represents a multidimensional factor that has a profound effect on AD onset and development. However, mechanistically, the effect of nutrition on AD is uncertain; therefore, optimal strategies or the timing of nutritional intervention to prevent or treat AD has not been established.Thus, this review summarizes the current state of knowledge concerning nutritional disorders, AD patient and caregiver burden, and the roles of nutrition in the pathophysiology of AD. We aim to emphasize knowledge gaps to provide direction for future research and to establish optimal nutrition-based intervention strategies for AD.

Red Blood Cell Fatty Acid Profiles Are Significantly Altered in South Australian Mild Cognitive Impairment and Alzheimer's Disease Cases Compared to Matched Controls

Nutritional imbalances have been associated with a higher risk for cognitive impairment. This study determined the red blood cell (RBC) fatty acid profile of newly diagnosed mild cognitive impairment (MCI) and Alzheimer's disease (AD) patients compared to age and gender-matched controls. There was a significant increase in palmitic acid (p < 0.00001) for both MCI and AD groups. Saturated fatty acids were significantly elevated in the MCI group, including stearic acid (p = 0.0001), arachidic acid (p = 0.003), behenic acid (p = 0.0002), tricosanoic acid (p = 0.007) and lignoceric acid (p = 0.001). n-6 polyunsaturated fatty acids (PUFAs) were significantly reduced in MCI, including linoleic acid (p = 0.001), γ-linolenic acid (p = 0.03), eicosatrienoic acid (p = 0.009) and arachidonic acid (p < 0.00004). The n-3 PUFAs, α-linolenic acid and docosahexaenoic acid, were both significantly reduced in MCI and AD (p = 0.0005 and p = 0.00003). A positive correlation was evident between the Mini-Mental State Examination score and nervonic acid in MCI (r = 0.54, p = 0.01) and a negative correlation with γ-linolenic acid in AD (r = -0.43, p = 0.05). Differences in fatty acid profiles may prove useful as potential biomarkers reflecting increased risk for dementia.

Quantitative Lipidomic Analysis of Serum Phospholipids Reveals Dissociable Markers of Alzheimer's Disease and Subcortical Cerebrovascular Disease

BACKGROUND

Circulating phospholipid species have been shown to predict Alzheimer's disease (AD) prognosis but the link between phospholipid disturbances and subcortical small vessel cerebrovascular disease (CeVD) common in AD patients is not known.

OBJECTIVE

This study used quantitative lipidomics to measure serum diacyl, alkenyl (ether), alkyl, and lyso phospholipid species in individuals with extensive CeVD (n = 29), AD with minimal CeVD (n = 16), and AD with extensive CeVD (n = 14), and compared them to age-matched controls (n = 27). Memory was assessed using the California Verbal Learning Test. 3.0T MRI was used to assess hippocampal volume, atrophy, and white matter hyperintensity (WMH) volumes as manifestations of CeVD.

RESULTS

AD was associated with significantly higher concentrations of choline plasmalogen 18:0_18:1 and alkyl-phosphocholine 18:1. CeVD was associated with significantly lower lysophospholipids containing 16:0. Phospholipids containing arachidonic acid (AA) were associated with poorer memory in controls, whereas docosahexaenoic acid (DHA)-containing phospholipids were associated with better memory in individuals with AD+CeVD. In controls, DHA-containing phospholipids were associated with more atrophy and phospholipids containing linoleic acid and AA were associated with less atrophy. Lysophospholipids containing 16:0, 18:0, and 18:1 were correlated with less atrophy in controls, and of these, alkyl-phosphocholine 18:1 was correlated with smaller WMH volumes. Conversely, 16:0_18:1 choline plasmalogen was correlated with greater WMH volumes in controls.

CONCLUSION

This study demonstrates discernable differences in circulating phospholipids in individuals with AD and CeVD, as well as new associations between phospholipid species with memory and brain structure that were specific to contexts of commonly comorbid vascular and neurodegenerative pathologies.