High-density lipoproteins (HDL) play a critical role in cholesterol homeostasis. Apolipoprotein E (APOE), particularly the E4 allele, is a significant risk factor for Alzheimer’s disease but is also a key HDL-associated protein involved in lipid transport in both the periphery and central nervous systems. The objective was to determine the influence of the APOE genotype on HDL function and size in the context of Alzheimer’s disease. HDL from 194 participants (non-demented controls, mild cognitive impairment, and Alzheimer’s disease dementia) were isolated from the plasma. The HDL cholesterol efflux capacity (CEC), lecithin-cholesterol acyltransferase (LCAT) activity, and particle diameter were measured. Neuropsychological test scores, clinical dementia rating, and magnetic resonance imaging scores were used to determine if cognition is associated with HDL function and size. HDL CEC and LCAT activity were reduced in APOE3E4 carriers compared to APOE3E3 carriers, regardless of diagnosis. In APOE3E3 carriers, CEC and LCAT activity were lower in patients. In APOE3E4 patients, the average particle size was lower. HDL LCAT activity and particle size were positively correlated with the neuropsychological scores and negatively correlated with the clinical dementia rating. We provide evidence for the first time of APOE genotype-specific alterations in HDL particles in Alzheimer’s disease and an association between HDL function, size, and cognitive function.

High-density lipoproteins (HDLs) are key regulators of cellular cholesterol homeostasis but are functionally altered in many chronic diseases. The factors that cause HDL functional loss in chronic disease are not fully understood. It is also unknown what roles antioxidant carotenoids play in protecting HDL against functional loss. The aim of this study was to measure how various disease-associated chemical factors including exposure to (1) Cu²⁺ ions, (2) hypochlorous acid (HOCL), (3) hydrogen peroxide (H₂O₂), (4) sialidase, (5) glycosidase, (6) high glucose, (7) high fructose, and (8) acidic pH, and the carotenoid antioxidants (9) lutein and (10) zeaxanthin affect HDL functionality. We hypothesized that some of the modifications would have stronger impacts on HDL particle structure and function than others and that lutein and zeaxanthin would improve HDL function. HDL samples were isolated from generally healthy human plasma and incubated with the corresponding treatments listed above. Cholesterol efflux capacity (CEC), lecithin–cholesterol acyl transferase (LCAT) activity, and paraoxonase-1 (PON1) activity were measured in order to determine changes in HDL functionality. Median HDL particle diameter was increased by acidic pH treatment and reduced by HOCl, high glucose, high fructose, N-glycosidase, and lutein treatments. Acidic pH, oxidation, and fructosylation all reduced HDL CEC, whereas lutein, zeaxanthin, and sialidase treatment improved HDL CEC. LCAT activity was reduced by acidic pH, oxidation, high fructose treatments, and lutein. PON1 activity was reduced by sialidase, glycosidase, H₂O₂, and fructose and improved by zeaxanthin and lutein treatment. These results show that exposure to oxidizing agents, high fructose, and low pH directly impairs HDL functionality related to cholesterol efflux and particle maturation, whereas deglycosylation impairs HDL antioxidant capacity. On the other hand, the antioxidants lutein and zeaxanthin improve or preserve both HDL cholesterol efflux and antioxidant activity but have no effect on particle maturation.

The effects of fasting on high-density lipoprotein (HDL) particles remain an area of ongoing investigation. This narrative review examines the impact of various fasting regimens, including intermittent fasting (IF) and continuous fasting (CF), on HDL cholesterol (HDL-C), particle size distribution, and concentration. Current evidence on fasting's influence on HDL particles is limited and inconsistent, particularly in IF studies, where variability in HDL metrics, recruitment bias, and confounding factors-such as weight loss as a primary study goal-complicate interpretation. While some CF studies suggest a mild trend toward decreased HDL-C and alterations in HDL particle size distribution, the overall health implications of these changes remain unclear. Further research is needed to provide a more comprehensive understanding of how fasting affects HDL particles and their broader implication for health and disease.

Background: High‐density lipoproteins (HDL) are protective against several chronic diseases, including Alzheimer’s disease (AD). The size distribution of HDL particles is one of the determining factors of HDL function since HDL of various sizes subgroups play unique roles. Yet not much is known about HDL particle size distribution in the context of AD.Method: In this study negative‐stained transmission electron microscopy (NS‐TEM) was used to explore the particle size distribution of isolated HDL samples from 194 subjects with AD (n = 71), mild cognitive impairment (MCI, n = 40), or no cognitive impairment (n = 83). HDL particles were isolated using density‐adjusted ultracentrifugation followed by size exclusion chromatography and analyzed by NS‐TEM followed by image analysis using the software ImageJ. Individual particle diameter data were obtained, grouped into different size‐based categories and the relative abundances of each subgroup were compared among diagnostic groups and across clinical parameters.Result: Patients with AD and MCI had a significantly higher percentage of 7‐8 nm HDL particles and a lower percentage of 9‐10 nm, 12‐13 nm, and 13‐14 nm particles. Body mass index, clinical dementia rating score, and white matter hyperintensity volume were positively correlated with the percentage of 7‐8 nm particles and negatively correlated with the percentage of 9‐10 nm particles, whereas executive score, semantic memory score, and verbal memory score were negatively correlated with the percentage of 7‐8 nm particles, and positively correlated with the percentage of 9‐10 nm particles.Conclusion: These findings show that specific alterations in HDL particle size distribution in patients with AD and MCI are linked with measures of cognitive function and may be a promising direction for the discovery of new biomarkers and therapeutic targets in AD.

Summary: Lipoproteins (LPP) and extracellular vesicles are carriers of extracellular small RNA, with potential applications both in the areas of diagnostics and therapeutics. Lipid nanoparticles overlap across a range of densities and sizes in plasma, making them difficult to isolate intact and without contamination from other plasma components. Accurate characterization of their cargo through efficient isolation from other plasma components is required to understand their function. Here we describe the simultaneous separation of LPP classes using sequential flotation ultracentrifugation followed by size exclusion chromatography from 500µL of starting plasma. Using western blot, denaturing and non-denaturing gel electrophoresis, nuclear magnetic resonance, and electron microscopy, we demonstrate separation of the LPP classes with minimal contamination. We also show unique lipidomic, proteomic and small RNA signatures for each LPP class, including, for the first time, very high density high density lipoprotein particles in the density range of 1.21–1.25 g/mL. Motivation: In plasma, lipid nanoparticles overlap in size and density, making it difficult to separate and isolate intact particles. Additionally, currently available methods do not allow for simultaneous characterization and isolation of these particles. This method resolves both challenges. The results presented also analyze and describe the presence of known lipoprotein particles, as well as those that have been previously under-characterized.

Small-quantity lipid-based nutrient supplements (SQ-LNS) during pregnancy and postnatally were previously shown to improve high-density lipoprotein (HDL) cholesterol efflux capacity (CEC) and length in the children of supplemented mothers at 18 mo of age in the International Lipid-Based Nutrient Supplements (iLiNS) DYAD trial in Ghana. However, the effects of SQ-LNS on maternal HDL functionality during pregnancy are unknown. The goal of this cross-sectional, secondary outcome analysis was to compare HDL function in mothers supplemented with SQ-LNS vs. iron and folic acid (IFA) during gestation. HDL CEC and the activities of 3 HDL-associated enzymes were analyzed in archived plasma samples (N = 197) from a subsample of females at 36 weeks of gestation enrolled in the iLiNS-DYAD trial in Ghana. Correlations between HDL function and birth outcomes, inflammatory markers C-reactive protein (CRP) and alpha-1-acid glycoprotein (AGP), and the effects of season were explored to determine the influence of these factors on HDL function in this cohort of pregnant females. There were no statistically significant differences in HDL CEC, plasma lecithin-cholesterol acyltransferase (LCAT) activity, cholesteryl ester transfer protein (CETP) activity, or phospholipid transfer protein (PLTP) activity between mothers supplemented with SQ-LNS compared with IFA control, and no statistically significant relationships between maternal HDL function and childbirth outcomes. LCAT activity was negatively correlated with plasma AGP (R = -0.19, P = 0.007) and CRP (R = -0.28, P < 0.001), CETP and LCAT activity were higher during the dry season compared to the wet season, and PLTP activity was higher in the wet season compared to the dry season. Mothers in Ghana supplemented with SQ-LNS compared with IFA during gestation did not have measurable differences in HDL functionality, and maternal HDL function was not associated with childbirth outcomes. However, seasonal factors and markers of inflammation were associated with HDL function, indicating that these factors had a stronger influence on HDL functionality than SQ-LNS supplementation during pregnancy. The study was registered as NCT00970866. https://clinicaltrials.gov/study/NCT00970866