Biomarkers

Although fatty acids are integral structural components of neuronal membranes, knowledge of their metabolism and contribution to cognition is sparse and limited. This study aimed to evaluate the diagnostic performance of fatty acids in cerebrospinal fluid (CSF) fractions in the differential diagnosis of mild cognitive impairment (MCI) from cognitively unimpaired (CU) older adults.

Saturated fatty acids (SAFA), monounsaturated fatty acids (MUFA), and polyunsaturated fatty acids (PUFA) from three CSF fractions (unesterified, supernatant fluid and nanoparticles) were obtained from the Huntington Medical Research Institutes (HMRI) Aging Study. The data consisted of 68 CU and 38 MCI. The socio-demographic data were summarized where continuous variables were reported as mean ± SD and categorical variables as counts and percentages. Multivariable binary logistic regression analysis was performed to differentiat CU from MCI. The best fitting CSF fatty acids biomarker was integrated with CSF Aβ₄₂, tau, and Aβ₄₂/tau ratio to assess their impact on the diagnostic performance. The model was adjusted for covariates; age, sex, smoking status, hypertension, diabetes, and APOE genotype. ROC curves were generated for the top 10 CSF fatty acids based on the area under the curve (AUC), sensitivity, and specificity and statistical significance differences between the groups using the DeLong test.

The palmitoleic acid/palmitic acid ratio, alpha-linolenic acid, and palmitoleic acid in CSF unesterified, supernatant fluid, and nanoparticles fraction respectively effectively differentiated MCI from CU than Aβ, tau, and Aβ/tau with AUC of 0.70, 0.66 and 0.71 respectively which were significantly different from the AUC of Aβ₄₂, tau and Aβ₄₂/tau ratio (0.53, 0.54, 0.55) respectively. Moreover, integrating a panel of these fatty acids with Aβ₄₂/tau significantly improved its diagnostic accuracy. Age, sex, smoking, hypertension, APOE genotype and diabetes did not influence the model performance.

Our study suggests that changes in fatty acid metabolism precede abnormalities in amyloid and tau in MCI. Thus, strategies that regulate fatty acid metabolism may stem off early cognitive decline in an older population.