Many
of the functional proteins and lipids in high density lipoprotein
(HDL) particles are potentially glycosylated, yet very little is known
about the glycoconjugates of HDL. In this study, HDL was isolated
from plasma by sequential micro-ultracentrifugation, followed by glycoprotein
and glycolipid analysis. N-Glycans, glycopeptides, and gangliosides
were extracted and purified followed by analysis with nano-HPLC Chip
quadrupole time of flight mass spectrometry and MS/MS. HDL particles
were found to be highly sialylated. Most of the N-glycans (∼90%)
from HDL glycoproteins were sialylated with one or two neuraminic
acids (Neu5Ac). The most abundant N-glycan was a biantennary complex
type glycan with two sialic acids (Hexose5HexNAc4Neu5Ac2) and was found in multiple glycoproteins using
site-specific glycosylation analysis. The observed O-glycans were
all sialylated, and most contained a core 1 structure with two Neu5Acs,
including those that were associated with apolipoprotein CIII (ApoC-III)
and fetuin A. GM3 (monosialoganglioside, NeuAc2–3Gal1–4Glc–Cer)
and GD3 (disialoganglioside, NeuAc2–8NeuAc2–3Gal1–4Glc–Cer)
were the major gangliosides in HDL. A 60% GM3 and 40% GD3 distribution
was observed. Both GM3 and GD3 were composed of heterogeneous ceramide
lipid tails, including d18:1/16:0 and d18:1/23:0. This report describes
for the first time a glycomic approach for analyzing HDL, highlighting
that HDL are highly sialylated particles.
Meals high in SFA, particularly palmitate, are associated with postprandial inflammation
and insulin resistance. Milk fat globule membrane (MFGM) has anti-inflammatory properties
that may attenuate the negative effects of SFA-rich meals. Our objective was to examine
the postprandial metabolic and inflammatory response to a high-fat meal composed of palm
oil (PO) compared with PO with an added dairy fraction rich in MFGM (PO+MFGM) in
overweight and obese men and women (n 36) in a randomised,
double-blinded, cross-over trial. Participants consumed two isoenergetic high-fat meals
composed of a smoothie enriched with PO with v. without a cream-derived
complex milk lipid fraction ( dairy fraction rich in MFGM) separated by a washout of 1–2
weeks. Serum cytokines, adhesion molecules, cortisol and markers of inflammation were
measured at fasting, and at 1, 3 and 6 h postprandially. Glucose, insulin and lipid
profiles were analysed in plasma. Consumption of the PO + MFGM v. PO meal
resulted in lower total cholesterol (P = 0·021), LDL-cholesterol
(P = 0·046), soluble intracellular adhesion molecule
(P = 0·005) and insulin (P = 0·005) incremental AUC, and
increased IL-10 (P = 0·013). Individuals with high baseline C-reactive
protein (CRP) concentrations (≥3 mg/l, n 17) had higher
(P = 0·030) insulin at 1 h after the PO meal than individuals with CRP
concentrations <3 mg/l (n 19). The addition of MFGM attenuated
this difference between CRP groups. The addition of a dairy fraction rich in MFGM
attenuated the negative effects of a high-SFA meal by reducing postprandial cholesterol,
inflammatory markers and insulin response in overweight and obese individuals,
particularly in those with elevated CRP.
Dietary recommendations suggest decreased consumption of SFA to minimise CVD risk;
however, not all foods rich in SFA are equivalent. To evaluate the effects of SFA in a
dairy food matrix, as Cheddar cheese, v. SFA from a vegan-alternative
test meal on postprandial inflammatory markers, a randomised controlled cross-over trial
was conducted in twenty overweight or obese adults with metabolic abnormalities.
Individuals consumed two isoenergetic high-fat mixed meals separated by a 1- to 2-week
washout period. Serum was collected at baseline, and at 1, 3 and 6 h postprandially and
analysed for inflammatory markers (IL-6, IL-8, IL-10, IL-17, IL-18, TNFα, monocyte
chemotactic protein-1 (MCP-1)), acute-phase proteins C-reactive protein (CRP) and serum
amyloid-A (SAA), cellular adhesion molecules and blood lipids, glucose and insulin.
Following both high-fat test meals, postprandial TAG concentrations rose steadily
(P < 0·05) without a decrease by 6 h. The incremental AUC (iAUC)
for CRP was significantly lower (P < 0·05) in response to the
cheese compared with the vegan-alternative test meal. A treatment effect was not observed
for any other inflammatory markers; however, for both test meals, multiple markers
significantly changed from baseline over the 6 h postprandial period (IL-6, IL-8, IL-18,
TNFα, MCP-1, SAA). Saturated fat in the form of a cheese matrix reduced the iAUC for CRP
compared with a vegan-alternative test meal during the postprandial 6 h period. The study
is registered at clinicaltrials.gov under NCT01803633.
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