Minor compounds from virgin olive oil attenuate LPS-induced inflammation via visfatin-related gene modulation on primary human monocytes.

We have analyzed the effects of minor compounds found in the unsaponifiable fraction (UF) and in the phenolic fraction (PF) of virgin olive oil (VOO) on LPS-induced inflammatory response via visfatin modulation in human monocytes. For this purpose, monocytes were incubated with UF and PF at different concentrations and the pro-inflammatory stimulus LPS for 24 hr; squalene (SQ) and hydroxytyrosol (HTyr), the main components in UF and PF, respectively, were also used. The relative expression of both pro-inflammatory and anti-inflammatory genes, as well as other genes related to the NAD+-biosynthetic pathway was evaluated by RT-qPCR; and the secretion of some of these markers was assessed by ELISA procedures. We found that UF, SQ, PF, and HTyr prevented from LPS-induced dysfunctional gene expression and secretion via visfatin-related gene modulation in human monocytes. These findings unveil a potential beneficial role for minor compounds of VOO in the prevention of inflammatory-disorders. PRACTICAL APPLICATION: In this project, potential health benefits of VOO micronutrients (unsaponifiable and phenolic compounds) were confirmed through anti-inflammatory assays. Our results reveal new interesting researching goals concerning nutrition by considering the role of bioactive VOO compounds in the prevention and progress of diseases related to inflammation.

Monounsaturated Fatty Acids in a High-Fat Diet and Niacin Protect from White Fat Dysfunction in the Metabolic Syndrome.

SCOPE: Obesity is a principal causative factor of metabolic syndrome. Niacin potently regulates lipid metabolism. Replacement of saturated fatty acids by MUFAs or inclusion of omega-3 long-chain PUFAs in the diet improves plasma lipid levels. However, the potential benefits of niacin in combination with MUFAs or omega-3 long-chain PUFAs against white adipose tissue (WAT) dysfunction in the high fat diet (HFD)-induced metabolic syndrome are unknown. METHODS AND RESULTS: Male Lepob/ob LDLR-/- mice are fed a chow diet or HFDs based on milk cream (21% kcal), olive oil (21% kcal), or olive oil (20% kcal) plus 1% kcal from eicosapentaenoic and docosahexaenoic acids, including immediate-release niacin (1% w/v) in drinking water, for 8 weeks. Mice are then phenotyped. Dietary MUFAs are identified as positive regulators of adipose NAD+ signaling pathways by triggering NAD+ biosynthesis via the salvage pathway. This coexists with overexpression of genes involved in recognition of NAD+ and fatty acids, a surrounding lipid environment dominated by exogenous oleic acid and an alternatively activated macrophage profile, which culminate in a healthy expansion of WAT and improvement of several hallmarks that typify the metabolic syndrome. CONCLUSION: Niacin in combination with dietary MUFAs can favor WAT homeostasis in the development of HFD-induced obesity and metabolic syndrome.

Dietary fatty acids on aortic root calcification in mice with metabolic syndrome.

Metabolic syndrome (MetS) is associated with obesity, dyslipidemia, type 2 diabetes, and chronic low-grade inflammation. The aim of this study was to determine the role of high-fat low-cholesterol diets (HFLCDs) rich in SFAs (HFLCD-SFAs), MUFAs (HFLCD-MUFAs) or MUFAs plus omega-3 long-chain PUFAs (HFLCD-PUFAs) on vascular calcification by the modulation of the RANKL/RANK/OPG system in the aortic roots of Lepob/obLDLR-/- mice. Animals fed with HFLCD-SFAs had increased weight and a greater atheroma plaque size, calcification, and RANKL/CATHK expression in the aortic root than mice on MUFA-enriched diets, with an increasing OPG expression in the aortic roots of the latter. Our study demonstrates that compared to dietary SFAs, MUFAs from olive oil protect against atherosclerosis by interfering with vascular calcification via the RANKL/RANK/OPG system in the setting of MetS. These findings open opportunities for developing novel nutritional strategies with olive oil as the most important dietary source of MUFAs (notably oleic acid) to prevent cardiovascular complications in MetS.

The effects of exogenous fatty acids and niacin on human monocyte-macrophage plasticity.

SCOPE: Macrophage plasticity allows adapting to different environments, having a dual activity in inflammatory-related diseases. Our hypothesis is that the type of dietary fatty acids into human postprandial triglyceride-rich lipoproteins (TRLs), alone or in combination with niacin (vitamin B3), could modulate the plasticity of monocytes-macrophages. METHODS AND RESULTS: We isolated TRLs at the postprandial peak from blood samples of healthy volunteers after the ingestion of a meal rich in saturated fatty acids (SFAs), monounsaturated fatty acids (MUFAs) or MUFAs plus omega-3 long-chain polyunsaturated fatty acids (LCPUFAs). Autologous monocytes isolated at fasting were first induced to differentiate into naïve macrophages. We observed that postprandial TRL-MUFAs, particularly in combination with niacin, enhance competence to monocytes to differentiate and polarise into M2 macrophages. Postprandial TRL-SFAs made polarised macrophages prone to an M1 phenotype. In contrast to dietary SFAs, dietary MUFAs in the meals plus immediate-release niacin primed circulating monocytes for a reduced postprandial pro-inflammatory profile. CONCLUSION: Our study underlines a role of postprandial TRLs as a metabolic entity in regulating the plasticity of the monocyte-macrophage lineage and also brings an understanding of the mechanisms by which dietary fatty acids are environmental factors fostering the innate immune responsiveness in humans.

Exogenous fatty acids and niacin on acute prostaglandin D2 production in human myeloid cells.

Niacin activates HCA2 receptor that results in the release of PGD2. However, little is known on PGD2-producing cells and the role of fatty acids. Notably M-CSF macrophages exhibited a timely dependent PGD2 production upon niacin challenge. Short pretreatment of M-CSF macrophages with autologous postprandial TRLs induced the down-regulation of HCA2 gene and up-regulation of genes encoding COX1 and COX2 enzymes in a fatty acid-dependent manner. These effects were paralleled by a higher PGD2 production with postprandial TRL-SFAs. The niacin-mediated transcriptional activity of all genes involved in PGD2 biosynthesis was desensitized in a time-dependent manner by postprandial TRLs, leading to a decreased PGD2 release. In vivo, the net excursions of PGD2 in plasma followed similar fatty acid-dependent patterns as those found for PGD2 release in vitro. The predominant fatty acid class in the diet acutely modulates PGD2 biosynthetic pathway both in vitro and in vivo.

Niacin and olive oil promote skewing to the M2 phenotype in bone marrow-derived macrophages of mice with metabolic syndrome.

Metabolic syndrome (MetS) is associated with obesity, dyslipemia, type 2 diabetes and chronic low-grade inflammation. The aim of this study was to determine the role of high-fat low-cholesterol diets (HFLCDs) rich in SFAs (HFLCD-SFAs), MUFAs (HFLCD-MUFAs) or MUFAs plus omega-3 long-chain PUFAs (HFLCD-PUFAs) on polarisation and inflammatory potential in bone marrow-derived macrophages (BMDMs) from niacin (NA)-treated Lep(ob/ob)LDLR(-/-) mice. Animals fed with HFLCD-SFAs had increased weight and serum triglycerides, and their BMDMs accumulated triglycerides over the animals fed with HFLCD-MUFAs or -PUFAs. Furthermore, BMDMs from animals fed with HFLCD-SFAs were polarised towards the M1 phenotype with functional competence to produce pro-inflammatory cytokines, whereas BMDMs from animals fed with HFLCD-MUFAs or -PUFAs were skewed to the anti-inflammatory M2 phenotype. These findings open opportunities for developing novel nutritional strategies with olive oil as the most important dietary source of MUFAs (notably oleic acid) to prevent development and progression of metabolic complications in the NA-treated MetS.

Evidence for melatonin synthesis in the rat brain during development.

Melatonin production is not restricted to the pineal gland. Several extrapineal sources of this indole such as retina, Harderian gland, and immune system are well documented. Melatonin of pineal origin is not present in the rat at early stages of development. To assess the potential capacity of local melatonin synthesis by the immature brain and to gain insight into the relationship between melatonin production by the brain (without the pineal gland) and pineal gland during rat development, the melatonin content as well as the expression and activity of the melatonin-synthesizing enzymes, N-acetyltransferase (NAT) and hydroxyindole-O-methyltransferase (HIOMT), were studied at fetal and postnatal stages. Moreover, melatonin-membrane receptor (MT(1)) expression was also analyzed. Both, the expression and activity of NAT and HIOMT were found in the brain with significant day/night differences in enzymes activities. Additionally, melatonin content was detected in all stages showing day/night differences depending on the stage of development. The brain nocturnal melatonin content was higher than diurnal content on postnatal day 16 and in adult rats which is in accordance with the pineal melatonin synthesis. To investigate the origin of this brain melatonin, pinealectomized rats were used and we found that the developing brain produced its own melatonin. Also, MT(1) expression was detected in brain during development. These results demonstrate that, when the pineal is not yet producing melatonin, there is melatonin synthesis by the brain that could be used as protection from free radical damage and/or could exert some actions through MT(1) receptors.

Melatonin synthesized by Jurkat human leukemic T cell line is implicated in IL-2 production.

Human lymphocytes have recently been described as an important physiological source of melatonin (N-acetyl-5-methoxytryptamine), which could be involved in the regulation of the human immune system. On the other hand, stimulation of IL-2 production by exogenous melatonin has been shown in the Jurkat human lymphocytic cell line. Furthermore, both melatonin membrane and nuclear receptors are present in these cells. In this study, we show that the necessary machinery to synthesize melatonin is present and active in resting and stimulated Jurkat cells. Accordingly, we have found that cells synthesize and release melatonin in both conditions. Therefore, we investigated whether endogenous melatonin produced by Jurkat cells was involved in the regulation of IL-2 production. When melatonin membrane and nuclear receptors were blocked using specific antagonists, luzindole and CGP 55644, respectively, we found that IL-2 production decreased, and this drop was reverted by exogenous melatonin. Additionally, PHA activation of Jurkat cells changed the profile of melatonin nuclear receptor mRNA expression. A previous study showed that exogenous melatonin is able to counteract the decrease in IL-2 production caused by prostaglandin E2 (PGE2) in human lymphocytes via its membrane receptor. In our model, when we blocked the melatonin membrane receptor with luzindole, the inhibitory effect of PGE2 on IL-2 production was higher. Therefore, we have demonstrated the physiological role of endogenous melatonin in this cell line. These findings indicate that endogenous melatonin synthesized by human T cells would contribute to regulation of its own IL-2 production, acting as an intracrine, autocrine, and/or paracrine substance.

Melatonin synthesis and melatonin-membrane receptor (MT1) expression during rat thymus development: role of the pineal gland.

To gain insight into the relationship between thymus and pineal gland during rat development, the melatonin content as well as the activity and expression of the two key enzymes for melatonin biosynthesis, i.e. N-acetyltransferase (NAT) and hydroxyindole-O-methyltransferase (HIOMT), were studied in the thymus at fetal and postnatal stages. Moreover, melatonin-membrane receptor (MT1) expression was also analyzed. We found both the expression and activity of thymic NAT and HIOMT at 18 days of fetal life. Additionally, there is production of melatonin in the thymus as well as MT1 expression at this fetal age. These results show values higher in day-time than at night-time. The pineal gland begins to produce significant levels of melatonin around postnatal day 16, and this synthesis shows a circadian rhythm with high values during the dark period; therefore the nocturnal serum melatonin may inhibit thymic melatonin production. To document this, we report an increased melatonin content of the thymus in pinealectomized rats compared with sham-pinealectomized. In conclusion, these results show, for the first time, the presence of the biosynthetic machinery of melatonin and melatonin production in developing rat thymus and that the pineal gland may regulate this process.