Sergio Lopez

Effects of meals rich in either monounsaturated or saturated fat on lipid concentrations and on insulin secretion and action in subjects with high fasting triglyceride concentrations

BACKGROUND The nature of dietary fats and fasting concentrations of triglycerides affect postprandial hypertriglyceridemia and glucose homeostasis. OBJECTIVES The objectives were to examine the effects of meals enriched in monounsaturated fatty acids (MUFAs) or saturated fatty acids (SFAs) on postprandial lipid, glucose, and insulin concentrations and to examine the extent of β cell function and insulin sensitivity in subjects with high fasting triglyceride concentrations. DESIGN Fourteen men with fasting hypertriglyceridemia and normal glucose tolerance were given meals (≈10 kcal/kg body weight) containing MUFAs, SFAs, or no fat. Blood samples were collected at baseline and hourly over 8 h for analysis. RESULTS The high-fat meals significantly increased postprandial concentrations of triglycerides, nonesterified fatty acids, and insulin and postprandial indexes of β cell function. However, postprandial indexes of insulin sensitivity decreased significantly. These effects were significantly attenuated with MUFAs relative to SFAs. CONCLUSIONS MUFAs postprandially buffered β cell hyperactivity and insulin intolerance relative to SFAs in subjects with high fasting triglyceride concentrations. These data suggest that, in contrast with SFAs, MUFA-based strategies may provide cardiovascular benefits to persons at risk by limiting lipid and insulin excursions and may contribute to optimal glycemic control after meal challenges.

Membrane composition and dynamics: A target of bioactive virgin olive oil constituents☆

The endogenous synthesis of lipids, which requires suitable dietary raw materials, is critical for the formation of membrane bilayers. In eukaryotic cells, phospholipids are the predominant membrane lipids and consist of hydrophobic acyl chains attached to a hydrophilic head group. The relative balance between saturated, monounsaturated, and polyunsaturated acyl chains is required for the organization and normal function of membranes. Virgin olive oil is the richest natural dietary source of the monounsaturated lipid oleic acid and is one of the key components of the healthy Mediterranean diet. Virgin olive oil also contains a unique constellation of many other lipophilic and amphipathic constituents whose health benefits are still being discovered. The focus of this review is the latest evidence regarding the impact of oleic acid and the minor constituents of virgin olive oil on the arrangement and behavior of lipid bilayers. We highlight the relevance of these interactions to the potential use of virgin olive oil in preserving the functional properties of membranes to maintain health and in modulating membrane functions that can be altered in several pathologies. This article is part of a Special Issue entitled: Membrane Structure and Function: Relevance in the Cells Physiology, Pathology and Therapy.

Influence of postprandial triglyceride-rich lipoproteins on lipid-mediated gene expression in smooth muscle cells of the human coronary artery

AIMS Postprandial triglyceride-rich lipoproteins (TRL) have a direct effect on vascular smooth muscle cells (SMC) and they increase the risk of atherogenesis. Here, we have tested the hypothesis that the different fatty acid composition of TRL is capable of differentially modifying gene expression in human coronary artery SMC (CASMC). In addition, the effect of TRL on cell proliferation and transcription factor activation was also evaluated. METHODS AND RESULTS TRL were prepared from plasma of healthy volunteers after the ingestion of meals enriched in refined olive oil (ROO), butter or a mixture of vegetable and fish oils (VEFO). We use cDNA microarrays to determine the genes differentially expressed in TRL-treated CASMC. Correspondence cluster analysis demonstrated that TRL-butter, -ROO and -VEFO provoked different transcriptional profiles in CASMC. Sixty-six genes were regulated by TRL-butter, 55 by -ROO, and 47 by -VEFO. The data revealed that TRL-butter predominantly activated genes involved in the regulation of cell proliferation and inflammation. Likewise, TRL-VEFO induced the expression of genes implicated in inflammation, while TRL-ROO promoted a less atherogenic gene profile. CONCLUSION The pathophysiological contribution of TRL to the development of atherosclerosis and the stability of atherosclerotic plaques may depend on the fatty acid composition of TRL. Our findings suggest a role for macrophage-inhibiting cytokine-1 (MIC-1) in coronary artery cardiovascular events.

Minor compounds of olive oil have postprandial anti-inflammatory effects

High postprandial levels of TAG may further induce endothelial dysfunction and inflammation in subjects with high fasting levels of TAG, an effect that seems to be related to oxidative stress. The present study investigated whether minor compounds of olive oil with antioxidant activity decrease postprandial levels of soluble isoforms of intercellular adhesion molecule 1 (sICAM-1) and vascular cell adhesion molecule 1 (sVCAM-1), as surrogate markers of vascular inflammation, after a high-fat meal. A randomized crossover and blind trial on fourteen healthy and fourteen hypertriacylglycerolaemic subjects was performed. The study involved a 1-week adaptation lead-in period on a National Cholesterol Education Program Step I diet supplemented with extra-virgin olive oil (EVOO) containing 1125 mg polyphenols/kg and 350 mg tocopherols/kg, or refined olive oil (ROO) with no polyphenols or tocopherols. After a 12 h fast, the participants ate a high-fat meal enriched in EVOO or ROO (50 g/m2 body surface area), which on average provided 3700 kJ energy with a macronutrient profile of 72% fat, 22% carbohydrate and 6% protein. Blood samples drawn hourly over the following 8 h demonstrated a similar postprandial TAG response for both EVOO and ROO meals. However, in both healthy and hypertriacylglycerolaemic subjects the net incremental area under the curve for sICAM-1 and sVCAM-1 were significantly lower after the EVOO meal. In conclusion,the consumption of EVOO with a high content of minor antioxidant compounds may have postprandial anti-inflammatory protective effects.

A high-fat meal promotes lipid-load and apolipoprotein B-48 receptor transcriptional activity in circulating monocytes

BACKGROUND The postprandial metabolism of dietary fats results in the production of apolipoprotein B-48 (apoB48)-containing triglyceride-rich lipoproteins (TRLs), which cause rapid receptor-mediated macrophage lipid engorgement via the apoB48 cell surface receptor (apoB48R). Monocytes circulate together with apoB48-containing TRLs in the postprandial bloodstream and may start accumulating lipids even before their migration to tissues and differentiation to macrophages. OBJECTIVE We sought to determine whether circulating monocytes are equipped with apoB48R and whether, in the postprandial state, circulating monocytes accumulate lipids and modulate apoB48R transcriptional activity after intake of a high-fat meal. DESIGN In a crossover design, we studied the effect of a high-fat meal on fasting and postprandial concentrations of triglycerides, free fatty acids, cholesterol, and insulin in 12 healthy men. TRLs and monocytes were freshly isolated at fasting, hourly until the postprandial peak, and at the late postprandial phase. TRLs were subjected to triglycerides, apoB48, and apolipoprotein B-100 analyses; and lipid accumulation and apoB48R mRNA expression levels were measured in monocytes. RESULTS Monocytes showed a time-dependent lipid accumulation in response to the high-fat meal, which was paralleled by an increase in apoB48R mRNA expression levels. These effects were coincident only with an increase in apoB48-containing TRLs in the postprandial phase and were also observed ex vivo in freshly isolated monocytes incubated with apoB48-containing TRLs. CONCLUSION In a setting of abundant plasma apoB48-containing TRLs, these findings highlight the role of dietary fat in inducing lipid accumulation and apoB48R gene transcription in circulating monocytes.

Induction of Sustained Hypercholesterolemia by Single Adeno-Associated Virus–Mediated Gene Transfer of Mutant hPCSK9

Objectives—Patients with mutations in the proprotein convertase subtilisin/kexin type 9 (PCSK9) gene have hypercholesterolemia and are at high risk of adverse cardiovascular events. We aimed to stably express the pathological human D374Y gain-of-function mutant form of PCSK9 (PCSK9DY) in adult wild-type mice to generate a hyperlipidemic and proatherogenic animal model, achieved with a single systemic injection with adeno-associated virus (AAV). Approach and Results—We constructed an AAV-based vector to support targeted transfer of the PCSK9DY gene to liver. After injection with 3.5×1010 viral particles, mice in the C57BL/6J, 129/SvPasCrlf, or FVB/NCrl backgrounds developed long-term hyperlipidemia with a strong increase in serum low-density lipoprotein. Macroscopic and histological analysis showed atherosclerotic lesions in the aortas of AAV-PCSK9DY mice fed a high-fat-diet. Advanced lesions in these high-fat-diet–fed mice also showed evidence of macrophage infiltration and fibrous cap formation. Hepatic AAV-PCSK9DY infection did not result in liver damage or signs of immunologic response. We further tested the use of AAV-PCSK9DY to study potential genetic interaction with the ApoE gene. Histological analysis of ApoE−/− AAV-PCSK9DY mice showed a synergistic response to ApoE deficiency, with aortic lesions twice as extensive in ApoE−/− AAV-PCSK9DY-transexpressing mice as in ApoE−/− AAV-Luc controls without altering serum cholesterol levels. Conclusions—Single intravenous AAV-PCSK9DY injection is a fast, easy, and cost-effective approach, resulting in rapid and long-term sustained hyperlipidemia and atherosclerosis. We demonstrate as a proof of concept the synergy between PCSK9DY gain-of-function and ApoE deficiency. This methodology could allow testing of the genetic interaction of several mutations without the need for complex and time-consuming backcrosses.

The effects of dietary fatty acids on the postprandial triglyceride-rich lipoprotein/apoB48 receptor axis in human monocyte/macrophage cells☆☆☆

Intestinally produced triglyceride-rich lipoproteins (TRL) play an important role in the progression of atherosclerosis. In this study, we investigated the relevance of monounsaturated fatty acid (MUFA) and saturated fatty acid (SFA) in postprandial TRL in affecting the transcriptional activity of the apolipoprotein-B48 receptor (ApoB48R) and its functionality in human monocyte/macrophage cells. Healthy male volunteers were administered four standardized high-fat meals containing butter, high-palmitic sunflower oil, olive oil (ROO) or a mixture of vegetable and fish oils (50 g/m(2) body surface area) to obtain a panel of postprandial TRL with gradual MUFA oleic acid-to-SFA palmitic acid ratios. The increase in this ratio was linearly associated with a decrease of ApoB48R up-regulation and lipid accumulation in THP-1 and primary monocytes. ApoB48R mRNA levels and intracellular triglycerides were also lower in the monocytes from volunteers after the ingestion of the ROO meal when compared to the ingestion of the butter meal. In THP-1 macrophages, the increase in the MUFA oleic acid-to-SFA palmitic acid ratio in the postprandial TRL was linearly correlated with an increase in ApoB48R down-regulation and a decrease in lipid accumulation. We also revealed that the nuclear receptor transcription factors PPARα, PPARβ/δ, and PPARγ and the PPAR-RXR transcriptional complex were involved in sensing the proportion of MUFA oleic acid and SFA palmitic acid, and these were also involved in adjusting the transcriptional activity of ApoB48R. The results of this study support the notion that MUFA-rich dietary fats may prevent excessive lipid accumulation in monocyte/macrophage cells by targeting the postprandial TRL/ApoB48R axis.

Triglyceride-Rich Lipoprotein Regulates APOB48 Receptor Gene Expression in Human THP-1 Monocytes and Macrophages

The postprandial metabolism of dietary fats implies that the production of TG-rich lipoproteins (TRL) contributes to the progression of plaque development. TRL and their remnants cause rapid receptor-mediated monocyte/macrophage lipid engorgement via the cell surface apoB48 receptor (apoB48R). However, the mechanistic basis for apoB48 receptor (APOB48R) regulation by postprandial TRL in monocytes and macrophages is not well established. In this study, we investigated the effects of postprandial TRL from healthy volunteers on the expression of APOB48R mRNA and lipid uptake in human THP-1 monocytes and THP-1-derived macrophages. The expression of APOB48R mRNA was upregulated in THP-1 monocytes, but downregulated in THP-1-derived macrophages when treated with postprandial TRL (P < 0.05), in a dose- and time-dependent manner. TG and free cholesterol were dramatically increased in THP-1-derived macrophages (140 and 50%, respectively; P < 0.05) and in THP-1 monocytes (160 and 95%, respectively; P < 0.05). This lipid accumulation was severely decreased (~50%; P < 0.05) in THP-1-derived macrophages by small interfering RNA (siRNA) targeting of APOB48R. Using PPAR and retinoid X receptor (RXR) agonists, antagonists, and siRNA, our data indicate that PPARα, PPARγ, and RXRα are involved in postprandial TRL-induced APOB48R transcriptional regulation. Co-incubation with acyl-CoA synthetase or acyl-CoA:cholesterol acyltransferase inhibitors potentiated the effects of postprandial TRL on the expression of APOB48R mRNA in THP-1 monocytes and THP-1-derived macrophages. Our findings collectively suggest that APOB48R represents a molecular target of postprandial TRL via PPAR-dependent pathways in human THP-1 monocytes and macrophages and advance a potentially important link between postprandial metabolism of dietary fats and atherogenesis.

The influence of major dietary fatty acids on insulin secretion and action

Purpose of review To briefly summarize recent advances towards understanding the influence of major dietary fatty acids on β-cell function and evaluate their implications for insulin resistance. Recent findings Studies in humans have shown that β-cell function and insulin sensitivity improve progressively in the postprandial period as the proportion of monounsaturated fatty acids (MUFAs) with respect to saturated fatty acids (SFAs) in dietary fats increases. However, cell-culture experiments have revealed a dichotomy in the ability of fatty acids to moderate hyperactivity of, and induce lipotoxicity in, β-cells. There are also some novel findings regarding the ability of HDL to protect β-cells against oxidized LDL-induced apoptosis in vitro and of reconstituted HDL to attenuate insulin resistance in vivo. These findings raise new questions regarding the contribution of dietary fatty acids to insulin secretion and action. Summary These new findings point to a critical role for major dietary fatty acids in the etiology and pathogenesis of diabetes, which appears to be of particular relevance during postprandial periods and mainly depends on the fatty acid type. This underscores the importance of dietary fatty acids in standard diabetes management.

Extra‐virgin vs. refined olive oil on postprandial hemostatic markers in healthy subjects

There are stillmanyopenquestions regarding themodulationof the hemostatic system by dietary fats in the postprandial state [1]. However, rapidly accumulating evidence links the ingestion of a high-fat meal to oxidative stress [2], which has also recently emerged as a determinant for thrombogenesis and fibrinolysis [3,4].Amongstdietary fats, extra-virginoliveoil (EVOO) isakey contributor to the cardiovascular and thrombotic disease preventive properties attributed to the Mediterranean diet [5]. As antioxidants are common in EVOO, it remains to be establishedwhethermeals rich inEVOOcould favourablyaffect the postprandial hemostatic system, independently of the effects usually associated with dietary fatty acids. The aim of this study was to evaluate the effects of olive oil with (EVOO) and without (refined olive oil, ROO) antioxidant minor compoundsonpostprandialmarkers related to thrombogenesis and fibrinolysis, and triglycerides (TG) in healthy subjects. ROOwas obtained by physical refining of EVOO and had no detected minor compounds with antioxidant activity, whereas the contents (in mg kg) of carotenoids, tocopherols and polyphenols in EVOOwere 22, 350 and 1125, respectively. The fatty acid composition and TG molecular species were identical for EVOO and ROO. Fourteen healthy male nonsmokers [age (mean ± SD) 27.41 ± 7.20 years; BMI (kg m) 23.92 ± 1.91] were recruited by advertising. Subjects were required to have no evidence of established coronary heart disease, renal impairment, hypothyroidism or liver dysfunction. Prior to the study, all subjects provided informed consent using Human Clinic Commission and Ethic Committee approved protocols. The design of the study was, randomized, withinsubject crossover and blinded investigators. Subjects had an adaptation 1-week lead-in period that consisted of a NCEP Step I diet with the corresponding fat (EVOO or ROO), which supplied 9623 kJ daily and identical distribution of carbohydrates (49%), proteins (13%), fats (38%), cholesterol (184 mg) and fibers (23 g). Subjects were then sampled after a 12-h overnight fast (baseline values), immediately, they were administered a fat-rich meal consisting of the corresponding dietary fat (EVOO or ROO, 50 g m body surface area) mixed with one portion of plain pasta (50 g), one slice of brown bread (28 g) and one skimmed yogurt. Blood samples were drawn every 1 h for a total of 8 h (postprandial values). Plasma levels of TG, tissue factor, fibrinogen, tissue-type plasminogen activator (t-PA) antigen and plasminogen activator inhibitor-1 (PAI-1) antigen were measured. For all parameters, mean and standard deviations were calculated. Differences were evaluated using one-factor repeated-measures ANOVA. A Bonferroni correction was used for the post hoc detection of significant pairwise differences. The net incremental area under the curve (netAUC) was calculated by the trapezoidal method. All P-values are two-sided, and the designated level of significance was P < 0.05. Our findings are depicted in Table 1. We found that, after 1-week lead-in dietary period, EVOO and ROO did not change fasting plasma levels of TG, TF, fibrinogen, t-PA and PAI-1. The TG postprandial responses to EVOO and ROO meals were also similar. However, the netAUC for hemostatic markers were significantly lower after the EVOO meal compared with the ROO meal. Our data are in line with longand short-term and postprandial studies showing cardiovascular benefits and protection of endogenous antioxidant defences by EVOO [5– 7]. In the postprandial state, TG-rich lipoproteins support the