No abstract

High density lipoprotein (HDL) particles are believed to be protective due to their inverse correlation with the prevalence of cardiovascular diseases. However, recent studies show that in some conditions such as heart disease and diabetes, HDL particles can become dysfunctional. Great attention has been directed toward HDL particle composition because the relative abundances of HDL constituents determine HDL's functional properties. A key factor to consider when studying the structure and composition of plasma particles is the protein glycosylation. Here, we profile the O- and N-linked glycosylation of HDL associated-proteins including the truncated form of Apo CIII and their glycan heterogeneity in a site-specific manner. Apolipoprotein CIII, fetuin A, and alpha 1 antitrypsin are glycoproteins associated with lipoproteins and are implicated in many cardiovascular and other disease conditions. A targeted method (UHPLC-QQQ) was used to measure the glycoprotein concentrations and site-specific glycovariations of the proteins in human plasma and compared with HDL particles isolated from the same plasma samples. The proteins found in the plasma are differentially glycosylated compared to those isolated in HDL. The results of this study suggest that glycosylation may play a role in protein partitioning in the blood, with possible functional implications.

Since HDL glycoprofiles are associated with HDL functional capacity we set out to determine whether diet can alter the glycoprofiles of key HDL-associated proteins, including ApoE, a potent driver of chronic disease risk. Ten healthy subjects consumed a fast food (FF) and a Mediterranean (Med) diet for 4 days in randomized order, with a 4-day wash-out between treatments. A multiple reaction monitoring (MRM) method was used to characterize the site-specific glycoprofiles of HDL proteins, and HDL functional capacity was analyzed. We describe for the first time that ApoE has 7 mucin-type Oglycosylation sites, which were not affected by short-term diet. The glycoprofiles of other HDLassociated proteins were also unaffected, except a di-sialylated ApoC-III glycan was enriched after Med diet, while a non-sialylated ApoC-III glycan was enriched after FF diet. Twenty-five individual glycopeptides were significantly correlated with cholesterol efflux capacity and 21 glycopeptides were correlated with immunomodulatory capacity. Results from this study indicate that the glycoprofiles of HDL-associated proteins including ApoE are correlated with HDL functional capacity but generally unaffected by diet in the short-term, except ApoC-III sialylation. These results suggest that HDL protein glycoprofiles are affected by both acute and long-term factors, and may be useful for biomarker discovery.

As a crucial part of the symbiotic system, the gut microbiome has been shown to be a metabolic organ that presents important connections to many diseases and conditions, including cardiovascular diseases (CVD), the world wide leading cause of death. Trimethylamine N‐oxide (TMAO) is a plasma metabolite that is positively correlated with CVD. Trimethylamine (TMA) is produced by gut bacteria from dietary choline, betaine, or L‐carnitine, and is then converted in the liver to TMAO, which in turn affects hepatic and intestinal lipid and cholesterol metabolism. Because eggs are rich in choline, it has been speculated that their consumption may increase plasma TMAO. The objective of this study was to examine the effect of two eggs per day on plasma TMAO level and how it is related with gut microbiome composition in mildly hypercholesterolemic postmenopausal women. In this randomized, cross‐over study, 20 overweight human subjects were given two whole eggs and the equivalent amount of yolk‐free substitute as breakfast for four weeks, in randomized order, with a four‐week washout in between. Fasting blood draws and stool were collected at the beginning and of each treatment period. Plasma TMAO, choline, betaine and other metabolites were analyzed using LC/MS, while gut microbiome composition was analyzed using 16S amplicon sequencing. Plasma choline and betaine were significantly increased after whole egg but not yolk‐free substitute, however TMAO level was not significantly affected by treatments. Gut microbiome composition showed large inter‐individual variability at baseline and in response to the treatments. Parabacteroides, Ruminococcus, and Faecalibacterium were slightly increased after whole egg but not yolk‐free substitute for the majority of the subjects, while Bilophila slightly increased after yolk‐free substitute but not whole egg. The consumption of two eggs per day in overweight, postmenopausal mildly hypercholesterolemic women significantly increased plasma choline and betaine, but not TMAO, with a subtle effect on gut microbiome composition. This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Introduction: HDL is associated with increased longevity and protection from multiple chronic diseases. The major HDL protein ApoA-I has a half-life of about 4 days, however, the effects of diet on the composition of HDL particles at this time scale have not been studied. Objectives: The objective of this study is to investigate the short term dietary effect on HDL lipidomic composition. Methods: In this randomized order cross-over study, ten healthy subjects consumed a Mediterranean (Med) and a fast food (FF) diet for 4 days, with a 4-day wash-out between treatments. Lipidomic composition was analyzed in isolated HDL fractions by an untargeted LC-MS method with 15 internal standards. Results: HDL PE content was increased by FF diet, and 41 out of 170 lipid species were differentially affected by diet. Saturated fatty acids (FA) and odd chain FA were enriched after FF diet, while very-long chain FA and unsaturated FA were enriched after Med diet. The composition of PC, TG and CE were significantly altered to reflect the FA composition of the diet whereas the composition of SM and ceramides were generally unaffected. Conclusion: Results from this study indicate that the HDL lipidome is widely remodeled within 4 days of diet change and that certain lipid classes are more sensitive markers of diet whereas other lipid classes are better indicators of non-dietary factors.