Lipoproteins and ImmunoMetabolism

Dietary interventions have been consistently proposed as a part of a comprehensive strategy to lower the incidence and severity of atherosclerosis and cardiovascular diseases (CVD). Excessive consumption of fats enriched in saturated fatty acids (SFA) is associated with an increased risk of atherosclerosis and other CVD. By contrast, replacement of SFA with monounsaturated fatty acids (MUFA) and omega-3 long-chain polyunsaturated fatty acids (ω-3 PUFA) has been reported to be inversely associated with risk of atherosclerosis. This is partly due to the ability of MUFA (and PUFA) in modulating low-density lipoprotein (LDL) and triglyceride-rich lipoprotein (TRL) lipid composition and oxidation status, and thereby the functionality of such lipoproteins. While most of the nutritional studies have focused on elucidating the mechanisms by which dietary fats affect LDL and TRL, little or nothing is known about the regulatory effect of MUFA and PUFA on structure and functional remodelling of high-density lipoproteins (HDL). There is clear evidence of an inverse association between plasma levels of HDL and the formation of atherosclerotic plaques. However, recent studies have suggested that HDL may not be as beneficial as thought at least in patients with established cardiometabolic disorders. In those patients, the HDL behaves as pro-inflammatory lipoproteins. Until now, few studies have addressed this "dark side" of HDL and has never been evaluated the role of dietary fatty acids on HDL plasticity (i.e. phenotype and functionality). A better understanding of this duality between anti-inflammatory and pro-inflammatory HDL would be relevant to prevent HDL-related atherogenic dyslipidemias and to provide personalized dietary advices for a successful management of atherogenic lipid profiles. This step of proof-of-principle will determine the instrumental role of major fatty acids present on a diet (SFA, MUFA and MUFA plus ω-3 PUFA) in promoting or reversing the phenotype of pro-inflammatory HDL. We expect to offer a novel insight on HDL and its relationship with dietary fatty acids through the following objectives: 1) To analyse acute changes in the lipidome, proteome and functional properties of HDL in humans (healthy volunteers and patients with metabolic syndrome) upon a challenge of a meal rich in SFA, MUFA or MUFA plus ω-3 PUFA; and 2) To analyse the influence of diets rich in SFA, MUFA and MUFA plus ω-3 PUFA on HDL plasticity in a preclinical animal model of diet-induced metabolic syndrome and that develops atherosclerosis.

The oral lipid emulsions will contain water, sucrose, emulsifier, flavouring, and the corresponding fat (50 g/m2 of body surface area): milk cream (SFA) or refined olive oil (MUFA) with or without a dose of omega-3 PUFA, which will consist of 920 mg of EPA and 760 mg of DHA.

Triglyceride and NEFA levels in plasma will be measured at several time-points postprandially using routine biochemical procedures (mg/dL)

NAMP activity will be measured in plasma at several postprandial time-points using colorimetric techniques (UI/ml).

Pro-inflammatory and anti-inflammatory cytokines, including NFα, IL-1β, IL-6, IL-8, IL-10, ICAM-1, MCP-1, leptin, and adiponectin, in plasma will be measured using ELISA techniques (mg/dl).

The acute phase protein (hsCRP), PAI-1, fibrinogen, transferrin, albumin, and myeloperoxidase (MPO) will be measured using colorimetric techniques (mg/dl).

HDL protein and lipid fractions HDL will be analysed by MALDI-TOF MS after employing an organic polymeric anion exchanger [Poly(GMA/EGDMA)] for lipoprotein enrichment from serum samples.

HDL obtained from different postprandial points will be tested by their capacity to prevent LDL oxidation with an in vitro cell-free assay.

HDL cholesterol efflux capacity will be measured using fluorescent-labelled cholesterol. HDL extracted from serum at different postprandial points will be tested.

Lecithin choltesteryl acyl transferase (LCAT) activity (UI/ml) of HDL obtained from different postprandial points will be measured using a fluorimetric cell-free assay.

Paraoxonse 1 (PON1) activity, of HDL obtained from serum at different postprandial tiems, will be measured using a colorimetric assay (pmol/mL).

Inclusion Criteria: clinical diagnosis of metabolic syndrome Exclusion Criteria: Allergy to dairy products Allergy to fish oil Vegetarian Tobacco smoker Current or recent (<4 wk) use of fish oil supplements or more than four times fish/week Received innoculations within 2 mo of starting the study or planned to during the study Donated or intended to donate blood from 2 mo before the study till 2 mo after the study Unstable body weight (no weight gain/loss >3 kg) Medical condition that can interfere with the study outcome (i.e., biochemical evidence of active heart disease, renal impairment, hypothyroidism, liver dysfunction, etc.) Use of medications know to interfere with glucose homeostasis or lipid metabolism Use of anti-inflammatory medication, hormone or cytokine or growth factor therapies Abuse of drugs and/or alcohol Participation in another biomedical study within 1 mo before the first screening visit, or not wanting to be informed about chance-findings during screening. Severe diabetes, which requires application of insuin Diabetes-related complications.