Resveratrol exerts a biphasic effect on apolipoprotein M

Apolipoprotein M/sphingosine 1-phosphate protects against diabetic nephropathy

Diabetic nephropathy remains a common cause of end-stage renal failure and its associated mortality around the world. Sphingosine 1-phosphate (S1P) is a multifunctional lipid mediator and binds to HDL via apolipoprotein M (ApoM). Since HDL has been reported to be epidemiologically associated with kidney disease, we attempted to investigate the involvement of the ApoM/S1P axis in the pathogenesis/progression of diabetic nephropathy. In type 2 diabetic patients, the serum ApoM levels were inversely correlated with the clinical stage of diabetic nephropathy. The decline in the eGFR over a 5-year observation period proceeded more rapidly in subjects with lower serum ApoM levels. In a mouse model of streptozotocin-induced diabetes, deletion of ApoM deteriorated the phenotypes of diabetic nephropathy: the urinary albumin and plasma creatinine levels increased, the kidneys enlarged, and renal fibrosis and thickening of the basement membrane progressed. On the other hand, overexpression of ApoM ameliorated these phenotypes. These protective effects of ApoM were partially inhibited by treatment with VPC23019, an antagonist of S1P1 and S1P3, but not by treatment with JTE013, an antagonist of S1P2. ApoM/S1P axis attenuated activation of the Smad3 pathway, while augmented eNOS phosphorylation through the S1P1 pathway. Moreover, ApoM/S1P increased the SIRT1 protein levels and enhanced mitochondrial functions by increasing the S1P content of the cell membrane, which might cause selective activation of S1P1. ApoM might be a useful biomarker for predicting the progression of diabetic nephropathy, and the ApoM/S1P-S1P1 axis might serve as a novel therapeutic target for preventing the development/progression of diabetic nephropathy.

Apolipoprotein D modulates lipid mediators and osteopontin in an anti-inflammatory direction

BACKGROUND

HDL has been proposed to possess anti-inflammatory properties; however, the detail mechanisms have not been fully elucidated.

METHODS

We investigated the roles of Apolipoprotein D (ApoD) in the pathogenesis of inflammation in the mouse model of diet-induced obesity and that of lipopolysaccharide-induced sepsis and the in vitro experiments. Furthermore, we analyzed serum ApoD levels in human subjects.

RESULTS

The overexpression of human ApoD decreased the plasma IL-6 and TNF-a levels in both mice models. Lipidomics analyses demonstrated association of ApoD with increase of arachidonic acid, eicosapentaenoic acid, and docosahexaenoic acid, as well as of their metabolites, and of the anti-inflammatory molecule sphingosine 1-phosphate, and decrease of proinflammatory lysophosphatidic acids and lysophosphatidylinositol. ApoD-containing lipoproteins might directly bind eicosapentaenoic acid and docosahexaenoic acid. The modulations of the lysophosphatidic acid and sphingosine 1-phosphate levels resulted from the suppression of autotaxin expression and elevation of apolipoprotein M (ApoM), respectively. Moreover, ApoD negatively regulated osteopontin, a proinflammatory adipokine. The activation of PPARg by ApoD might suppress autotaxin and osteopontin. Serum ApoD levels were negatively correlated with the serum osteopontin and autotaxin levels and, positively with serum ApoM levels.

CONCLUSION

ApoD is an anti-inflammatory apolipoprotein, which modulates lipid mediators and osteopontin in an anti-inflammatory direction.

Caffeine Protects Against Retinal Inflammation

Caffeine, one of the most consumed central nervous system (CNS) stimulants, is an antagonist of A₁ and A_2A adenosine receptors. In this study, we investigated the potential protective effects of this methylxanthine in the retinal tissue. We tested caffeine by using in vitro and in vivo paradigms of retinal inflammation. Human retinal pigment epithelial cells (ARPE-19) were exposed to lipopolysaccharide (LPS) with or without caffeine. This latter was able to reduce the inflammatory response in ARPE-19 cells exposed to LPS, attenuating the release of IL-1β, IL-6, and TNF-α and the nuclear translocation of p-NFκB. Additionally, caffeine treatment restored the integrity of the ARPE-19 monolayer assessed by transepithelial electrical resistance (TEER) and the sodium fluorescein permeability test. Finally, the ischemia reperfusion (I/R) injury model was used in C57BL/6J mice to induce retinal inflammation and investigate the effects of caffeine treatment. Mouse eyes were treated topically with caffeine, and a pattern electroretinogram (PERG) was used to assess the retinal ganglion cell (RGC) function; furthermore, we evaluated the levels of IL-6 and BDNF in the retina. Retinal BDNF dropped significantly (p < 0.05) in the I/R group compared to the control group (normal mice); on the contrary, caffeine treatment maintained physiological levels of BDNF in the retina of I/R eyes. Caffeine was also able to reduce IL-6 mRNA levels in the retina of I/R eyes. In conclusion, these findings suggest that caffeine is a good candidate to counteract inflammation in retinal diseases.

Isoform-Dependent Effects of Apolipoprotein E on Sphingolipid Metabolism in Neural Cells

BACKGROUND

Sphingosine 1-phosphate (S1P) and ceramides have been implicated in the development of Alzheimer's disease. Apolipoprotein E (ApoE) isoforms are also involved in the development of Alzheimer's disease.

OBJECTIVE

We aimed at elucidating the potential association of the ApoE isoforms with sphingolipid metabolism in the central nervous system.

METHODS

We investigated the modulations of apolipoprotein M (apoM), a carrier of S1P, S1P, and ceramides in Apoeshl mice, which spontaneously lack apoE, and U251 cells and SH-SY5Y cells infected with adenovirus vectors encoding for apoE2, apoE3, and apoE4.

RESULTS

In the brains of Apoeshl mice, the levels of apoM were lower, while those of ceramides were higher. In U251 cells, cellular apoM and S1P levels were the highest in the cells overexpressing apoE2 among the apoE isoforms. The cellular and medium contents of ceramides decreased in the order of the cells overexpressing apoE3 > apoE2 and increased in the cells overexpressing apoE4. In SH-SY5Y cells, apoM mRNA and medium S1P levels were also the highest in the cells overexpressing apoE2. The cellular contents of ceramides decreased in the order of the cells overexpressing apoE3 > apoE2 = apoE4 and those in medium decreased in the order of the cells overexpressing apoE3 > apoE2, while increased in the cells overexpressing apoE4.

CONCLUSION

The modulation of apoM and S1P might partly explain the protective effects of apoE2 against Alzheimer's disease, and the modulation of ceramides might be one of the mechanisms explaining the association of apoE4 with the development of Alzheimer's disease.

Roflupram protects against rotenone-induced neurotoxicity and facilitates α-synuclein degradation in Parkinson's disease models

We have previously shown that roflupram (ROF) protects against MPP+-induced neuronal damage in models of Parkinson's disease (PD). Since impaired degradation of α-synuclein (α-syn) is one of the key factors that lead to PD, here we investigated whether and how ROF affects the degradation of α-syn in rotenone (ROT)-induced PD models in vivo and in vitro. We showed that pretreatment with ROF (10 μM) significantly attenuated cell apoptosis and reduced the level of α-syn in ROT-treated SH-SY5Y cells. Furthermore, ROF significantly enhanced the lysosomal function, as evidenced by the increased levels of mature cathepsin D (CTSD) and lysosomal-associated membrane protein 1 (LAMP1) through increasing NAD+/NADH and the expression of sirtuin 1 (SIRT1). Pretreatment with an SIRT1 inhibitor selisistat (SELI, 10 μM) attenuated the neuroprotection of ROF, ROF-reduced expression of α-syn, and ROF-increased expression levels of LAMP1 and mature CTSD. Moreover, inhibition of CTSD by pepstatin A (20 μM) attenuated ROF-reduced expression of α-syn. In vivo study was conducted in mice exposed to ROT (10 mg·kg-1·d-1, i.g.) for 6 weeks; then, ROT-treated mice received ROF (0.5, 1, or 2 mg·kg-1·d-1; i.g.) for four weeks. ROF significantly ameliorated motor deficits, which was accompanied by increased expression levels of tyrosine hydroxylase, SIRT1, mature CTSD, and LAMP1, and a reduced level of α-syn in the substantia nigra pars compacta. Taken together, these results demonstrate that ROF exerts a neuroprotective action and reduces the α-syn level in PD models. The mechanisms underlying ROF neuroprotective effects appear to be associated with NAD+/SIRT1-dependent activation of lysosomal function.

Glycation of HDL Polymerizes Apolipoprotein M and Attenuates Its Capacity to Bind to Sphingosine 1-Phosphate

Aim: Recently, it has been established that most of the pleiotropic effects of high-density lipoprotein (HDL) are attributed to sphingosine 1-phosphate (S1P), which rides on HDL via apolipoprotein M (ApoM). In subjects with diabetes mellitus, both the pleiotropic effects of HDL and its role in reverse cholesterol transport are reported to be impaired. To elucidate the mechanisms underlying the impaired pleiotropic effects of HDL in subjects with diabetes, from the aspects of S1P and ApoM.

Methods: The incubation of HDL in a high-glucose condition resulted in the dimerization of ApoM. Moreover, the treatment of HDL with methylglyoxal resulted in the modulation of the ApoM structure, as suggested by the results of western blot analysis, isoelectric focusing electrophoresis, and two-dimensional gel electrophoresis, which was reversed by treatment with anti-glycation reagents.

Results: The glycation of HDL resulted in impaired binding of the glycated HDL to S1P, and the S1P on glycated HDL degraded faster. In the case of human subjects, on the other hand, although both the serum ApoM levels and the ApoM content in HDL were lower in subjects with diabetes, we did not observe the polymerization of ApoM.

Conclusions: Modulation of the quantity and quality of ApoM might explain, at least in part, the impaired functions of HDL in subjects with diabetes mellitus. ApoM might be a useful target for laboratory testing and/or the treatment of diabetes mellitus.

Dibutyl phthalate induces allergic airway inflammation in rats via inhibition of the Nrf2/TSLP/JAK1 pathway

Dibutyl phthalate (DBP), an important plastic contaminant in the environment, is known to cause organ toxicity. Although current research has shown that DBP-induced organ toxicity is associated with oxidative stress, the toxic effect of DBP on the lungs have not been fully elucidated. Therefore, we investigated the potential mechanism by which DBP induces pulmonary toxicity using a model of DBP-induced allergic airway inflammation in rats. The results showed that chronic exposure to DBP induced histopathological damage, inflammation, oxidative stress, apoptosis, and increased the protein levels of thymic stromal lymphopoietin (TSLP) and its downstream protein Janus kinase 1 (JAK1) and signal transducer and activator of transcription 6 (STAT6). Moreover, DBP exposure inhibited nuclear factor-erythroid-2-related factor 2 (Nrf2) and levels of its target genes NAD(P)H quinone oxidoreductase 1 (NQO1) and heme oxygenase-1 (HO-1). Additionally, using in vitro experiments, we found that DBP induced oxidative stress, reduced cell viability, and inhibited the Nrf2/HO-1/NQO1 pathway in mouse alveolar type II epithelial cell line. Overall, these data demonstrate that DBP induces allergic airway inflammation in rats via inhibition of the Nrf2/TSLP/JAK1 pathway.

Modulation of sphingosine 1-phosphate by hepatobiliary cholesterol handling

Hepatobiliary cholesterol handling, mediated by Niemann-Pick C1-like 1 protein (NPC1L1) and ABCG5/8, is well-known to contribute to the homeostasis of cholesterol. We attempted to elucidate the impact of hepatobiliary cholesterol handling on the homeostasis of sphingolipids and lysophospholipids, especially sphingosine 1-phosphate (S1P). We induced the overexpression of NPC1L1 or ABCG5/8 in the mouse liver. Hepatic NPC1L1 overexpression increased the plasma and hepatic S1P levels, while it decreased the biliary S1P levels, and all of these changes were inhibited by ezetimibe. The ability of HDL to activate Akt in the endothelial cells was augmented by hepatic NPC1L1 overexpression. NPC1L1-mediated S1P transport was confirmed by both in vitro and in vivo studies conducted using C₁₇ S1P, an exogenous S1P analog. Upregulation of apolipoprotein M (apoM) was involved in these modulations, although apoM was not necessary for these modulations. Moreover, the increase in the plasma S1P levels also observed in ABCG5/8-overexpressing mice was dependent on the elevation of the plasma apoM levels. In regard to other sphingolipids and lysophospholipids, ceramides were similarly modulated by NPC1L1 to S1P, while other lipids were differently influenced by NPC1L1 or ABCG5/8 from S1P. Hepatobiliary cholesterol handling might also regulate the functional lipids, such as S1P.

Protection Against Insulin Resistance by Apolipoprotein M/Sphingosine-1-Phosphate

Subjects with low serum HDL cholesterol levels are reported to be susceptible to diabetes, with insulin resistance believed to be the underlying pathological mechanism. Apolipoprotein M (apoM) is a carrier of sphingosine-1-phosphate (S1P), a multifunctional lipid mediator, on HDL, and the pleiotropic effects of HDL are believed to be mediated by S1P. In the current study, we attempted to investigate the potential association between apoM/S1P and insulin resistance. We observed that the serum levels of apoM were lower in patients with type 2 diabetes and that they were negatively correlated with BMI and the insulin resistance index. While deletion of apoM in mice was associated with worsening of insulin resistance, overexpression of apoM was associated with improvement of insulin resistance. Presumably, apoM/S1P exerts its protective effect against insulin resistance by activating insulin signaling pathways, such as the AKT and AMPK pathways, and also by improving the mitochondrial functions through upregulation of SIRT1 protein levels. These actions of apoM/S1P appear to be mediated via activation of S1P1 and/or S1P3. These results suggest that apoM/S1P exerts protective roles against the development of insulin resistance.

Biphasic Dose-Response Induced by Phytochemicals: Experimental Evidence

Many phytochemicals demonstrate nonmonotonic dose/concentration-response termed biphasic dose-response and are considered to be hormetic compounds, i.e., they induce biologically opposite effects at different doses. In numerous articles the hormetic nature of phytochemicals is declared, however, no experimental evidence is provided. Our aim was to present the overview of the reports in which phytochemical-induced biphasic dose-response is experimentally proven. Hence, we included in the current review only articles in which the reversal of response between low and high doses/concentrations of phytochemicals for a single endpoint was documented. The majority of data on biphasic dose-response have been found for phytoestrogens; other reports described these types of effects for resveratrol, sulforaphane, and natural compounds from various chemical classes such as isoquinoline alkaloid berberine, polyacetylenes falcarinol and falcarindiol, prenylated pterocarpan glyceollin1, naphthoquinones plumbagin and naphazarin, and panaxatriol saponins. The prevailing part of the studies presented in the current review was performed on cell cultures. The most common endpoint tested was a proliferation of tumor and non-cancerous cells. Very few experiments demonstrating biphasic dose-response induced by phytochemicals were carried out on animal models. Data on the biphasic dose-response of various endpoints to phytochemicals may have a potential therapeutic or preventive implication.

Sphingosine-1-Phosphate and Macrophage Biology-How the Sphinx Tames the Big Eater

The sphingolipid sphingosine-1-phosphate (S1P) is produced by sphingosine kinases to either signal through intracellular targets or to activate a family of specific G-protein-coupled receptors (S1PR). S1P levels are usually low in peripheral tissues compared to the vasculature, forming a gradient that mediates lymphocyte trafficking. However, S1P levels rise during inflammation in peripheral tissues, thereby affecting resident or recruited immune cells, including macrophages. As macrophages orchestrate initiation and resolution of inflammation, the sphingosine kinase/S1P/S1P-receptor axis emerges as an important determinant of macrophage function in the pathogenesis of inflammatory diseases such as cancer, atherosclerosis, and infection. In this review, we therefore summarize the current knowledge how S1P affects macrophage biology.

Resveratrol Action on Lipid Metabolism in Cancer

Cancer diseases have the leading position in human mortality nowadays. The age of oncologic patients is still decreasing, and the entire scientific society is eager for new ways to fight against cancer. One of the most discussed issues is prevention by means of natural substances. Resveratrol is a naturally occurring plant polyphenol with proven antioxidant, anti-inflammatory, and anticancer effects. Tumor cells display specific changes in the metabolism of various lipids. Resveratrol alters lipid metabolism in cancer, thereby affecting storage of energy, cell signaling, proliferation, progression, and invasiveness of cancer cells. At the whole organism level, it contributes to the optimal metabolism extent with respect to the demands of the organism. Thus, resveratrol could be used as a preventive and anticancer agent. In this review, we focus on some of the plethora of lipid pathways and signal molecules which are affected by resveratrol during carcinogenesis.

Apolipoprotein M suppresses the phenotypes of IgA nephropathy in hyper-IgA mice

Because the association between sphingosine 1-phosphate (S1P)/apolipoprotein M (ApoM) and chronic kidney diseases has not been established, we investigated the involvement of S1P/ApoM in the phenotypes of IgA nephropathy in hyper-IgA (HIGA) mice. The overexpression of ApoM in adenoviral gene transfer ameliorated the phenotypes of IgA nephropathy in HIGA mice, whereas the knockdown of ApoM with siRNA caused deterioration. When ApoM-overexpressing HIGA mice were treated with VPC23019, an antagonist against S1P receptor 1 (S1P1) and 3 (S1P3), we observed that the protective effects of ApoM were reversed, whereas JTE013, an antagonist against S1P2, did not inhibit the effects. We also found that S1P bound to albumin accelerated the proliferation of MES13 cells and the fibrotic changes of HK2 cells, which were inhibited by JTE013, whereas S1P bound to ApoM suppressed these changes, which were inhibited by VPC23019. These results suggest that S1P bound to ApoM possesses properties protective against the phenotypes of IgA nephropathy through S1P1 and S1P3, whereas S1P bound to albumin exerts deteriorating effects through S1P2. ApoM may be useful as a therapeutic target to treat or retard the progression of IgA nephropathy.-Kurano, M., Tsuneyama, K., Morimoto, Y., Nishikawa, M., Yatomi, Y. Apolipoprotein M suppresses the phenotypes of IgA nephropathy in hyper-IgA mice.

Regulation of the metabolism of apolipoprotein M and sphingosine 1-phosphate by hepatic PPARγ activity

Apolipoprotein M (apoM) is a carrier and a modulator of sphingosine 1-phosphate (S1P), an important multifunctional bioactive lipid. Since peroxisome proliferator-activated receptor γ (PPARγ) is reportedly associated with the function and metabolism of S1P, we investigated the modulation of apoM/S1P homeostasis by PPARγ. First, we investigated the modulation of apoM and S1P homeostasis by the overexpression or knockdown of PPARγ in HepG2 cells and found that both the overexpression and the knockdown of PPARγ decreased apoM expression and S1P synthesis. When we activated or suppressed the PPARγ more mildly with pioglitazone or GW9662, we found that pioglitazone suppressed apoM expression and S1P synthesis, while GW9662 increased them. Next, we overexpressed PPARγ in mouse liver through adenoviral gene transfer and observed that both the plasma and hepatic apoM levels and the plasma S1P levels decreased, while the hepatic S1P levels increased, in the presence of enhanced sphingosine kinase activity. Treatment with pioglitazone decreased both the plasma and hepatic apoM and S1P levels only in diet-induced obese mice. Moreover, the overexpression of apoM increased, while the knockdown of apoM suppressed PPARγ activities in HepG2 cells. These results suggested that PPARγ regulates the S1P levels by modulating apoM in a bell-shaped manner, with the greatest levels of apoM/S1P observed when PPARγ was mildly expressed and that hepatic apoM/PPARγ axis might maintain the homeostasis of S1P metabolism.

Lysophospholipids in laboratory medicine

Lysophospholipids (LPLs), such as lysophosphatidic acid (LPA), sphingosine 1-phosphate (S1P), and lysophosphatidylserine (LysoPS), are attracting attention as second-generation lipid mediators. In our laboratory, the functional roles of these lipid mediators and the mechanisms by which the levels of these mediators are regulated in vivo have been studied. Based on these studies, the clinical introduction of assays for LPLs and related proteins has been pursued and will be described in this review. Although assays of these lipids themselves are possible, autotaxin (ATX), apolipoprotein M (ApoM), and phosphatidylserine-specific phospholipase A₁ (PS-PLA₁) are more promising as alternate biomarkers for LPA, S1P, and LysoPS, respectively. Presently, ATX, which produces LPA through its lysophospholipase D activity, has been shown to be a useful laboratory test for the diagnosis and staging of liver fibrosis, whereas PS-PLA₁ and ApoM are considered to be promising clinical markers reflecting the in vivo actions induced by LysoPS and S1P.

Epigenetic Regulatory Mechanisms Induced by Resveratrol

Resveratrol (RVT) is one of the main natural compounds studied worldwide due to its potential therapeutic use in the treatment of many diseases, including cancer, diabetes, cardiovascular diseases, neurodegenerative diseases and metabolic disorders. Nevertheless, the mechanism of action of RVT in all of these conditions is not completely understood, as it can modify not only biochemical pathways but also epigenetic mechanisms. In this paper, we analyze the biological activities exhibited by RVT with a focus on the epigenetic mechanisms, especially those related to DNA methyltransferase (DNMT), histone deacetylase (HDAC) and lysine-specific demethylase-1 (LSD1).

Protective effect of resveratrol against light-induced retinal degeneration in aged SAMP8 mice

Purpose

The purpose of this study was to determine the protective effects of Resveratrol (RESV) on acute bright light-induced retinal degeneration in aged senescence accelerated mouse strain.

Methods

Ten three-month-old male SAMP8 mice (prone to aging) were randomly assigned to two experimental dietary groups: one untreated group and one RESV treatment group (n=20 eyes for each group). After 30 days of treatment, mice were exposed to intense bright light. Ten male SAMR1 mice (resistant to aging) served as control (n=20 eyes). The protective effects of RESV administration on light-induced retinal degeneration in SAMP8 strain as well as the effect of bright light damage in the retinas of SAMP8 mice were analyzed by electroretinography (ERG), retinal histology, mRNA, protein and lipid profile.

Results

68%-85% of a-wave amplitude and 72%-92% of b-wave amplitude were persevered by RESV in SAMP8 mice that were exposed to light damage. Also, RESV preserved their photoreceptor nuclei. mRNA expression of neuroprotective factors leukemia inhibitory factor (LIF), brain derived neurotrophic factor (BDNF), oncostatin M (OSM), cardiotrophin 1(CT-1) and cardiotrophin-like cytokine (CLC) were up-regulated 28, 8, 7, 5 and 9-fold in SAMP8 mice after RESV treatment. In addition, RESV could suppress the NF-κB pathway by down-regulating the expression of pIκB. Light damage led to increase of saturated FA, monoenoic FA, n6 PUFA and n6/n3 ratio and decrease of Docosahexaenoic acid (DHA). There was no significant difference on DHA and the ratio of n6/n3-FA between the untreated and RESV treated SAMP8 mice.

Conclusions

Collectively, our study provides evidence that RESV prevents light-induced retinal damage associated with aging.

Sphingosine 1-Phosphate and Atherosclerosis

Sphingosine 1-phosphate (S1P) is a potent lipid mediator that works on five kinds of S1P receptors located on the cell membrane. In the circulation, S1P is distributed to HDL, followed by albumin. Since S1P and HDL share several bioactivities, S1P is believed to be responsible for the pleiotropic effects of HDL. Plasma S1P levels are reportedly lower in subjects with coronary artery disease, suggesting that S1P might be deeply involved in the pathogenesis of atherosclerosis. In basic experiments, however, S1P appears to possess both pro-atherosclerotic and anti-atherosclerotic properties; for example, S1P possesses anti-apoptosis, anti-inflammation, and vaso-relaxation properties and maintains the barrier function of endothelial cells, while S1P also promotes the egress and activation of lymphocytes and exhibits pro-thrombotic properties. Recently, the mechanism for the biased distribution of S1P on HDL has been elucidated; apolipoprotein M (apoM) carries S1P on HDL. ApoM is also a modulator of S1P, and the metabolism of apoM-containing lipoproteins largely affects the plasma S1P level. Moreover, apoM modulates the biological properties of S1P. S1P bound to albumin exerts both beneficial and harmful effects in the pathogenesis of atherosclerosis, while S1P bound to apoM strengthens anti-atherosclerotic properties and might weaken the pro-atherosclerotic properties of S1P. Although the detailed mechanisms remain to be elucidated, apoM and S1P might be novel targets for the alleviation of atherosclerotic diseases in the future.

Resveratrol exerts a biphasic effect on apolipoprotein M

BACKGROUND AND PURPOSE

Resveratrol exerts a range of beneficial actions in several areas of pathophysiology, including vascular biology. Here, we have investigated the effects of resveratrol on apolipoprotein M (apoM), a carrier and modulator of sphingosine 1-phosphate (S1P), a vasoactive lipid mediator.

EXPERIMENTAL APPROACH

We used a hepatoma cell line (HepG2), human primary hepatocytes and C57BL/6 mice. We measured apoM, S1P and related enzymes, LDL receptors and sirtuin1 activity, using Western blotting, RT-PCR and enzyme assays. We also used si-RNA to knock-down sirtuin1 in HepG2 cells.

KEY RESULTS

In cultures of HepG2 cells, resveratrol (1-10 μM) increased intracellular apoM and S1P. High concentrations of resveratrol (100 μM) decreased extracellular (in the culture medium) apoM, whereas moderate concentrations of resveratrol (1-10 μM) increased extracellular apoM. High concentrations of resveratrol also increased LDL receptor expression, while all concentrations of resveratrol activated the histone deacetylase sirtuin1. In cultures of human primary hepatocytes, resveratrol, at all concentrations, increased both intra- and extracellular apoM. When wild-type mice were fed a resveratrol-containing chow (0.3% w/w) for 2 weeks, both the plasma and hepatic apoM and S1P levels were increased. However, the resveratrol diet did not affect hepatic LDL receptor levels in this in vivo study.

CONCLUSIONS AND IMPLICATIONS

Resveratrol increased intra- and extracellular levels of apoM, along with intracellular S1P levels, while a high concentration of resveratrol reduced extracellular apoM. The present findings suggest that resveratrol has novel effects on the metabolic kinetics of S1P, a multi-functional bioactive phospholipid.