Effects of eicosapentaenoic acid ethyl ester on visfatin and apelin in lean and overweight (cafeteria diet-fed) rats

Chronic docosahexaenoic acid supplementation improves metabolic plasticity in subcutaneous adipose tissue of aged obese female mice

This study aimed to characterize the potential beneficial effects of chronic docosahexaenoic acid (DHA) supplementation on restoring subcutaneous white adipose tissue (scWAT) plasticity in obese aged female mice. Two-month-old female C57BL/6J mice received a control (CT) or a high fat diet (HFD) for 4 months. Then, 6-month-old diet-induced obese (DIO) mice were distributed into the DIO and the DIOMEG group (fed with a DHA-enriched HFD) up to 18 months. In scWAT, the DHA-enriched diet reduced the mean adipocyte size and reversed the upregulation of lipogenic genes induced by the HFD, reaching values even lower than those observed in CT animals. DIO mice exhibited an up-regulation of lipolytic and fatty oxidation gene expressions that was reversed in DHA-supplemented mice except for Cpt1a mRNA levels, which were higher in DIOMEG as compared to CT mice. DHA restored the increase of proinflammatory genes observed in scWAT of DIO mice. While no changes were observed in total macrophage F4/80+/CD11b+ content, the DHA treatment switched scWAT macrophages profile by reducing the M1 marker Cd11c and increasing the M2 marker CD206. These events occurred alongside with a stimulation of beige adipocyte specific genes, the restoration of UCP1 and pAKT/AKT ratio, and a recovery of the HFD-induced Fgf21 upregulation. In summary, DHA supplementation induced a metabolic remodeling of scWAT to a healthier phenotype in aged obese mice by modulating genes controlling lipid accumulation in adipocytes, reducing the inflammatory status, and inducing beige adipocyte markers in obese aged mice.

Is Habitual Dietary Intake of Fats Associated with Apelin Gene Expression in Visceral and Subcutaneous Adipose Tissues and Its Serum Levels in Obese Adults?

INTRODUCTION

Apelin could be one of the last protective defenses before developing obesity-related disorders, including insulin resistance, type 2 diabetes, and hypertension, which can be modified by dietary intake. The present study investigated the association of habitual intake of total fatty acids (TFAs), saturated-, monounsaturated-, polyunsaturated FAs, n-3, and n-6 FAs with Apelin expression in visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT).

METHODS

We obtained VAT and SAT from 168 participants (64 nonobese and 104 obese) who had undergone open abdominal surgery. Dietary intake information was gathered with a valid and reliable food frequency questionnaire. The mRNA expression of the Apelin gene was analyzed by real-time PCR.

RESULTS

Apelin serum levels were increased in the obese subjects compared to the nonobese group (p = 0.016). The SAT and VAT Apelin mRNA levels were significantly elevated in the obese participants compared to the nonobese ones (p < 0.05). Based on BMI status, only obese subjects indicated a positive association between SAT and VAT Apelin expression and TFA intake (p < 0.001). However, this association was observed between SAT and VAT Apelin gene expression and polyunsaturated fatty acid (PUFA) and n-3 FA intakes in both obese and nonobese groups (p < 0.05).

CONCLUSION

High Apelin gene expression was associated with TFA intake in obese subjects in both fat tissues. However, habitual intake of PUFA and n-3 FA was associated with Apelin gene expression in obese and nonobese individuals. Our results indicate a determinative role of the quality and quantity of FA intake on adipose tissue.

The relationship between apelin and carotid intima media thickness, and the presence of plaque in dialysis patients

BACKGROUND

Apelin is a peptide that has important effects on the cardiovascular system due to its anti-atherogenic properties and regulating blood pressure. There is not enough research evaluating the effects of apelin levels on the cardiovascular system in hemodialysis (HD) and peritoneal dialysis (PD) patients concurrently. The aim of this study was to determine apelin levels in dialysis, and control groups and to investigate the relationship between apelin and carotid intima media thickness (CIMT).

MATERIALS AND METHODS

Thirty three HD patients, 35 PD patients, and 15 healthy individuals were included in the study. All laboratory data, N-terminal pro-B-type natriuretic peptide (NT-proBNP), IL-6, and apelin-13 levels were analyzed. To prevent interobserver errors in CIMT measurement, the analyses were performed by a single radiologist.

RESULT

CIMT, presence of plaque, apelin, NT-proBNP, IL-6, and C-reactive protein (CRP) levels were higher in dialysis patients. There was a relationship between apelin and CIMT, and between apelin and high-density lipoprotein (HDL) in PD patients. Age, apelin, HDL, parathormone (PTH), glucose, and smoking were found to affect the presence of plaque in dialysis patients.

CONCLUSION

Apelin levels were high in dialysis patients. Especially in PD patients, there was a negative correlation between apelin and CIMT, and between apelin and HDL. Therefore, apelin may play a role in the pathogenesis of cardiovascular diseases in PD patients.

Plasma Fatty Acid Composition Was Associated with Apelin Gene Expression in Human Adipose Tissues

Background

Apelin is an adipokine with an intermediatory role in obesity and insulin resistance, which can be modified by dietary intake.

Aims

In this study, we aimed to determine the association of the plasma fatty acid composition with apelin plasma concentration and gene expression in visceral (VAT) and subcutaneous (SAT) adipose tissues.

Methods

In this cross-sectional study, we recruited 179 patients aged 19-75 years who were candidates for elective surgery. Through the surgery, SAT and VAT were collected to measure apelin gene expression. Anthropometric measurements, fasting blood samples, and dietary intakes were collected before surgery. Free fatty acids (FFAs) in fasting whole plasma were measured using gas chromatography with flame ionization detection. Linear regression models were used to estimate standardized β (STZ β) showing the association of individual and total FFAs with apelin gene expression after adjustment for potential confounding variables.

Results

In multivariable analysis, we observed a significant positive association of total plasma free fatty acids (FFAs) (STZ β = 0.241, P = 0.006), saturated fatty acid (SFA) (STZ β = 0.336, P < 0.001), and monounsaturated fatty acid (MUFA) (STZ β = 0.313, P < 0.001) concentrations with apelin gene expression from VAT after controlling for age, sex, body mass index, homeostatic model assessment for insulin resistance (HOMA-IR), physical activity, and energy intake. In the SFA family, there was a direct association with plasma concentration of myristic acid (STZ β = 0.372, P < 0.001), pentadecanoic acid (STZ β = 0.252, P = 0.002), and heptadecanoic acid (STZ β = 0.407, P < 0.001) with apelin mRNA expression in VAT. There was no significant association between FFAs and apelin plasma concentration and SAT mRNA levels.

Conclusions

In conclusion, circulating plasma FFAs, SFA, and MUFA had a positive association with apelin gene expression in VAT. It seems that plasma fatty acid composition may regulate apelin gene expression in VAT.

Combination of cafeteria diet with intraperitoneally streptozotocin in rats. A type-2 diabetes model

Purpose

To develop a model of induction of type-2 diabetes (DM2) by combining low doses of streptozotocin (STZ) and a cafeteria diet.

Methods

Forty male Wistar rats (200 g) were allocated into four groups: control (non-diabetic, n = 10); STZ 30 mg/kg (diabetic, n = 10); STZ 35 mg/kg (diabetic,n = 10); and STZ 40 mg/kg (diabetic, n = 10). DM2 was induced with a single intraperitoneal injection of STZ after four weeks of cafeteria diet in the three diabetic groups. All animals were evaluated as for anthropometric, and biochemical analyses, as well as liver, kidney and pancreas histological analyses.

Results

Lower weight gain, higher water intake, higher Lee index, hyperglycemia and modified total protein, urea, alpha-amylase, as well as insulin resistance, hepatic steatosis, pancreas, and kidney injury were observed in animals treated with 35 and 40 mg/kg of STZ.

Conclusions

The results show that the experimental model using cafeteria diet associated with 35 mg/kg of STZ is a low-cost model and efficient in order to develop DM2, confirmed by the presence of polydipsia, hyperglycemia, altered biochemical tests, insulin resistance and damages to the liver, pancreas and kidney, which is similar to the disease found in humans.

The therapeutic potentials of apelin in obesity-associated diseases

Apelin, a peptide with several active isoforms ranging from 36 to 12 amino acids and its receptor APJ, a G-protein-coupled receptor, are widely distributed. However, apelin has emerged as an adipokine more than fifteen years ago, integrating the field of inter-organs interactions. The apelin/APJ system plays important roles in several physiological functions both in rodent and humans such as fluid homeostasis, cardiovascular physiology, angiogenesis, energy metabolism. Thus the apelin/APJ system has generated great interest as a potential therapeutic target in different pathologies. The present review will consider the effects of apelin in metabolic diseases such as obesity and diabetes with a focus on diabetic cardiomyopathy among the complications associated with diabetes and APJ agonists or antagonists of interest in these diseases.

Fatty acid composition, oxidative stability, and sensory evaluation of the sausages produced from the meat of pigs fed a diet enriched with 8% of fish oil

The objective of the present study was to increase by dietary means the long-chain polyunsaturated fatty acid (LC-PUFA) n-3 content in selected meat products. Fatty acid (FA) composition, texture, sensory characteristics, and oxidative stability were determined in the Vienna sausages (V-sausages) and Bologna-type salami (B-salami) produced from the meat of six pigs fed a standard feed (control, C) and six pigs fed a standard feed enriched with 8% of fish oil (F), respectively. The saturated FA content in the unheated FV and FB products was decreased (p < 0.05) by 24% and 39%, PUFA n-6/n-3 ratio improved (p < 0.001) from 13.9 to 2.8 and from 13.5 to 2.6, respectively. LC-PUFA n-3 content in the VF and BF products was 360 and 214 mg/100 g, which corresponds to 80% and 48% of the recommended daily intake. Interestingly, dietary fish oil decreased (p < 0.01) instrumentally the measured core hardness of the V-sausages, but increased (p < 0.001) this texture characteristic in the B-salami. Malondialdehyde content in the VF and BF products increased (p < 0.05) on average by 23% and the flavor of the heated FV sausages scored lower (p < 0.05) in comparison with the C-counterparts.

Fish oil extracted from Coregonus peled improves obese phenotype and changes gut microbiota in a high-fat diet-induced mouse model of recurrent obesity

Recurrent obesity is rapidly emerging as a public health problem. Previous studies have confirmed that fish oil supplementation can alleviate obesity in mice; however, the effect of fish oil on recurrent obesity remains unclear. In the present study, the modulatory effects of fish oil extracted from Coregonus peled on the phenotypes and gut microbiota of recurrent obese mice were evaluated by MRI, OGTT, and bioinformatics analysis. We found that fish oil supplementation could significantly reduce the body weight gain, net weight gain, body fat distribution, and glucose tolerance. In addition, the composition and structure of gut microbiota were significantly shifted toward those of the control group by fish oil treatment. Moreover, the relative abundance of gut microbiota, such as Bacteroidetes, Bacteroidia, Lachnospiraceae, and Bifidobacterium, was markedly responding to the rapid dietary changes between fish oil and high-fat diet. Overall, our results confirmed that the alleviation of recurrent obesity using fish oil supplementation might be modulated by altering the hysteretic behavior and memory-like function of gut microbiota. We proposed that further studies are needed to elucidate the modulation mechanism.

Breast milk apelin level increases with maternal obesity and high-fat feeding during lactation

OBJECTIVE

Recent evidence indicates that levels of breast milk (BM) hormones such as leptin can fluctuate with maternal adiposity, suggesting that BM hormones may signal maternal metabolic and nutritional environments to offspring during postnatal development. The hormone apelin is highly abundant in BM but its regulation during lactation is completely unknown. Here, we evaluated whether maternal obesity and overnutrition impacted BM apelin and leptin levels in clinical cohorts and lactating rats.

METHODS

BM and plasma samples were collected from normal-weight and obese breastfeeding women, and from lactating rats fed a control or a high fat (HF) diet during lactation. Apelin and leptin levels were assayed by ELISA. Mammary gland (MG) apelin expression and its cellular localization in lactating rats was measured by quantitative RT-PCR and immunofluorescence, respectively.

RESULTS

BM apelin levels increased with maternal BMI, whereas plasma apelin levels decreased. BM apelin was also positively correlated with maternal insulin and C-peptide levels. In rats, maternal HF feeding exclusively during lactation was sufficient to increase BM apelin levels and decrease its plasma concentration without changing body weight. In contrast, BM leptin levels increased with maternal BMI in humans, but did not change with maternal HF feeding during lactation in rats. Apelin is highly expressed in the rat MG during lactation and was mainly localized to mammary myoepithelial cells. We found that MG apelin gene expression was up-regulated by maternal HF diet and positively correlated with BM apelin content and maternal insulinemia.

CONCLUSIONS

Our study indicates that BM apelin levels increase with long- and short-term overnutrition, possibly via maternal hyperinsulinemia and transcriptional upregulation of MG apelin expression in myoepithelial cells. Apelin regulates many physiological processes, including energy metabolism, digestive function, and development. Further studies are needed to unravel the consequences of such changes in offspring development.

Adipokines, Myokines, and Cardiokines: The Role of Nutritional Interventions

It is now established that adipose tissue, skeletal muscle, and heart are endocrine organs and secrete in normal and in pathological conditions several molecules, called, respectively, adipokines, myokines, and cardiokines. These secretory proteins constitute a closed network that plays a crucial role in obesity and above all in cardiac diseases associated with obesity. In particular, the interaction between adipokines, myokines, and cardiokines is mainly involved in inflammatory and oxidative damage characterized obesity condition. Identifying new therapeutic agents or treatment having a positive action on the expression of these molecules could have a key positive effect on the management of obesity and its cardiac complications. Results from recent studies indicate that several nutritional interventions, including nutraceutical supplements, could represent new therapeutic agents on the adipo-myo-cardiokines network. This review focuses the biological action on the main adipokines, myokines and cardiokines involved in obesity and cardiovascular diseases and describe the principal nutraceutical approaches able to regulate leptin, adiponectin, apelin, irisin, natriuretic peptides, and follistatin-like 1 expression.

Visfatin and Rheumatoid Arthritis: Pathogenetic Implications and Clinical Utility

Objective:

Analysis and generalization of data related to visfatin involvement in the pathogenesis of inflammation at various stages of rheumatoid arthritis.

Data Synthesis:

Visfatin is an adipocytokine which has also been identified in non-adipose tissues. It influences directly on the maturation of B cells, which are involved in autoantibody production and T cell activation. Visfatin can promote inflammation via regulation of pro-inflammatory cytokines including TNF, IL-1β and IL-6. The concentration of circulating visfatin in rheumatoid arthritis patients is higher compared to healthy individuals. Several studies suggest that visfatin level is associated with rheumatoid arthritis activity, and its elevation may precede clinical signs of the relapse. In murine collagen-induced arthritis, visfatin levels were also found to be elevated both in inflamed synovial cells and in joint vasculature. Visfatin blockers have been shown to confer fast and long-term attenuation of pathological processes; however, most of their effects are transient. Other factors responsible for hyperactivation of the immune system can participate in this process at a later stage. Treatment of rheumatoid arthritis with a combination of these blockers and inhibitors of other mediators of inflammation can potentially improve treatment outcomes compared to current therapeutic strategies. Recent advances in the treatment of experimental arthritis in mice as well as the application of emerging treatment strategies obtained from oncology for rheumatoid arthritis management could be a source of novel adipokine-mediated anti-rheumatic drugs.

Conclusion:

The ongoing surge of interest in anticytokine therapy makes further study of visfatin highly relevant as it may serve as a base for innovational RA treatment.

Effect of aging and obesity on GLUT12 expression in small intestine, adipose tissue, muscle, and kidney and its regulation by docosahexaenoic acid and exercise in mice

Obesity is characterized by excessive fat accumulation and inflammation. Aging has also been characterized as an inflammatory condition, frequently accompanied by accumulation of visceral fat. Beneficial effects of exercise and n-3 long-chain polyunsaturated fatty acids in metabolic disorders have been described. Glucose transporter 12 (GLUT12) is one of the less investigated members of the GLUT family. Glucose, insulin, and tumor necrosis factor alpha (TNF-α) induce GLUT12 translocation to the membrane in muscle, adipose tissue, and intestine. We aimed to investigate GLUT12 expression in obesity and aging, and under diet supplementation with docosahexaenoic acid (DHA) alone or in combination with physical exercise in mice. Aging increased GLUT12 expression in intestine, kidney, and adipose tissue, whereas obesity reduced it. No changes on the transporter occurred in skeletal muscle. In obese 18-month-old mice, DHA further decreased GLUT12 in the 4 organs. Aerobic exercise alone did not modify GLUT12, but the changes triggered by exercise were able to prevent the DHA-diminishing effect, and almost restored GLUT12 basal levels. In conclusion, the downregulation of metabolism in aging would be a stimulus to upregulate GLUT12 expression. Contrary, obesity, an excessive energy condition, would induce GLUT12 downregulation. The combination of exercise and DHA would contribute to restore basal function of GLUT12. Novelty In small intestine, kidney and adipose tissue aging increases GLUT12 protein expression whereas obesity reduces it. Dietary DHA decreases GLUT12 in small intestine, kidney, adipose tissue and skeletal muscle. Exercise alone does not modify GLUT12 expression, nevertheless exercise prevents the DHA-diminishing effect on GLUT12.

Biochemical and nutritional overview of diet-induced metabolic syndrome models in rats: what is the best choice?

Metabolic syndrome (MS) is a condition that includes obesity, insulin resistance, dyslipidemias among other, abnormalities that favors type 2 Diabetes Mellitus (T2DM) and cardiovascular diseases development. Three main diet-induced metabolic syndrome models in rats exist: High carbohydrate diet (HCHD), high fat diet (HFD), and high carbohydrate-high fat diet (HCHHFD). We analyzed data from at least 35 articles per diet, from different research groups, to determine their effect on the development of the MS, aimed to aid researchers in choosing the model that better suits their research question; and also the best parameter that defines obesity, as there is no consensus to determine this condition in rats. For the HCHD we found a mild effect on body weight gain and fasting blood glucose levels (FBG), but significant increases in triglycerides, fasting insulin, insulin resistance and visceral fat accumulation. HFD had the greater increase in the parameters previously mentioned, followed by HCHHFD, which had a modest effect on FBG levels. Therefore, to study early stages of MS a HCHD is recommended, while HFD and HCHHFD better reproduce more severe stages of MS. We recommend the assessment of visceral fat accumulation as a good estimate for obesity in the rat.

Eicosapentaenoic Acid (EPA) Modulates Glucose Metabolism by Targeting AMP-Activated Protein Kinase (AMPK) Pathway

EPA, an omega-3 polyunsaturated fatty acid, exerts beneficial effects on human health. However, the molecular mechanisms underlying EPA function are poorly understood. The object was to illuminate molecular mechanism underlying EPA's role. Here, ¹H-NMR-based metabolic analysis showed enhanced branched-chain amino acids (BCAAs) and lactate following EPA treatment in skeletal muscle cells. EPA regulated mitochondrial oxygen consumption rate. Furthermore, EPA induced calcium/calmodulin-dependent protein kinase kinase (CaMKK) through the generation of intracellular calcium. This induced the phosphorylation of AMP-activated protein kinase (AMPK) and p38 mitogen-activated protein kinase (p38 MAPK) that led to glucose uptake, and the translocation of glucose transporter type 4 (GLUT4) in muscles. In conclusion, EPA exerts benign effects on glucose through the activation of AMPK-p38 MAPK signaling pathways in skeletal muscles.

Different Dietary Proportions of Fish Oil Regulate Inflammatory Factors but Do Not Change Intestinal Tight Junction ZO-1 Expression in Ethanol-Fed Rats

Sixty male Wistar rats were fed a control or an ethanol-containing diet in groups C or E. The fat compositions were adjusted with 25% or 57% fish oil substituted for olive oil in groups CF25, CF57, EF25, and EF57. Hepatic thiobarbituric acid-reactive substance (TBARS) levels, cytochrome P450 2E1 protein expression, and tumor necrosis factor- (TNF-) α, interleukin- (IL-) 1β, IL-6, and IL-10 levels, as well as intracellular adhesion molecule (ICAM)-1 levels were significantly elevated, whereas plasma adiponectin level was significantly reduced in group E (p < 0.05). Hepatic histopathological scores of fatty change and inflammation, in group E were significantly higher than those of group C (p < 0.05). Hepatic TBARS, plasma ICAM-1, and hepatic TNF-α, IL-1β, and IL-10 levels were significantly lower, and plasma adiponectin levels were significantly higher in groups EF25 and EF57 than those in group E (p < 0.05). The immunoreactive area of the intestinal tight junction protein, ZO-1, showed no change between groups C and E. Only group CF57 displayed a significantly higher ZO-1 immunoreactive area compared to group C (p = 0.0415). 25% or 57% fish oil substituted for dietary olive oil could prevent ethanol-induced liver damage in rats, but the mechanism might not be related to intestinal tight junction ZO-1 expression.

Maresin 1 inhibits TNF-alpha-induced lipolysis and autophagy in 3T3-L1 adipocytes

Obesity is associated with high levels of pro-inflammatory cytokines such as tumor necrosis factor-alpha (TNF-α), which promotes inflammation in adipose tissue. The omega-3 PUFAs, and their derived lipid mediators, such as Maresin 1 (MaR1) have anti-inflammatory effects on adipose tissue. This study aimed to analyze if MaR1 may counteract alterations induced by TNF-α on lipolysis and autophagy in mature 3T3-L1 adipocytes. Our data revealed that MaR1 (1-100 nM) inhibited the TNF-α-induced glycerol release after 48 hr, which may be related to MaR1 ability of preventing the decrease in lipid droplet-coating protein perilipin and G0/G1 Switch 2 protein expression. MaR1 also reversed the decrease in total hormone sensitive lipase (total HSL), and the ratio of phosphoHSL at Ser-565/total HSL, while preventing the increased ratio of phosphoHSL at Ser-660/total HSL and phosphorylation of extracellular signal-regulated kinase 1/2 induced by TNF-α. Moreover, MaR1 counteracted the cytokine-induced decrease of p62 protein, a key autophagy indicator, and also prevented the induction of LC3II/LC3I, an important autophagosome formation marker. Current data suggest that MaR1 may ameliorate TNF-α-induced alterations on lipolysis and autophagy in adipocytes. This may also contribute to the beneficial actions of MaR1 on adipose tissue and insulin sensitivity in obesity.

Eicosapentaenoic acid down-regulates expression of the selenoprotein P gene by inhibiting SREBP-1c protein independently of the AMP-activated protein kinase pathway in H4IIEC3 hepatocytes

Selenoprotein P (encoded by SELENOP in humans, Selenop in rat), a liver-derived secretory protein, induces resistance to insulin and vascular endothelial growth factor (VEGF) in type 2 diabetes. Suppression of selenoprotein P may provide a novel therapeutic approach to treating type 2 diabetes; however, few drugs inhibiting SELENOP expression in hepatocytes have been identified. The present findings demonstrate that eicosapentaenoic acid (EPA) suppresses SELENOP expression by inactivating sterol regulatory element-binding protein-1c (SREBP-1c, encoded by Srebf1 in rat) in H4IIEC3 hepatocytes. Treatment with EPA caused concentration- and time-dependent reduction in SELENOP promoter activity. EPA activated AMP-activated protein kinase (AMPK); however, the inhibitory effect of EPA on SELENOP promoter activity was not canceled with an AMPK inhibitor compound C and dominant-negative AMPK transfection. Deletion mutant promoter assays and computational analysis of transcription factor-binding sites conserved among the species resulted in identification of a sterol regulatory element (SRE)-like site in the SELENOP promoter. A chromatin immunoprecipitation (ChIP) assay revealed that EPA decreases binding of SREBP-1c to the SELENOP promoter. Knockdown of Srebf1 resulted in a significant down-regulation of Selenop expression. Conversely, SREBP-1c overexpression inhibited the suppressive effect of EPA. These data provide a novel mechanism of action for EPA involving improvement of systemic insulin sensitivity through the regulation of selenoprotein P production independently of the AMPK pathway and suggest an additional approach to developing anti-diabetic drugs.

Cardiotrophin-1 Regulates Adipokine Production in 3T3-L1 Adipocytes and Adipose Tissue From Obese Mice

Cardiotrophin-1 (CT-1) belongs to the IL-6 family of cytokines. Previous studies of our group revealed that CT-1 is a key regulator of glucose and lipid metabolism. The aim of the present study was to analyze the in vitro and in vivo effects of CT-1 on the production of several adipokines involved in body weight regulation, nutrient metabolism, and inflammation. For this purpose, 3T3-L1 adipocytes were incubated with recombinant protein CT-1 (rCT-1) (1-40 ng/ml) for 1 and 18 h. Moreover, the acute effects of rCT-1 administration (0.2 mg/kg, i.v.) for 30 min and 3 h on adipokines levels were also evaluated in high-fat fed obese mice. In 3T3-L1 adipocytes, rCT-1 treatment downregulated the expression and secretion of leptin, resistin, and visfatin. However, rCT-1 significantly stimulated apelin mRNA and secretion. rCT-1 (18 h) also promoted the activation by phosphorylation of AKT, ERK 1/2, and STAT3. Interestingly, pre-treatment with the PI3K inhibitor LY294002 reversed the stimulatory effects of rCT-1 on apelin expression, suggesting that this pathway could be mediating the effects of rCT-1 on apelin production. In contrast, acute administration of rCT-1 (30 min and 3 h) to diet-induced obese mice downregulated leptin and resistin, without significantly modifying apelin or visfatin mRNA in adipose tissue. Furthermore, CT-1 null mice exhibited altered expression of adipokines in adipose tissue. The present study demonstrates that rCT-1 modulates the production of adipokines in vitro and in vivo, suggesting that the regulation of the secretory function of adipocytes could be involved in the metabolic actions of this cytokine. J. Cell. Physiol. 232: 2469-2477, 2017. © 2016 Wiley Periodicals, Inc.

Eicosapentaenoic acid promotes mitochondrial biogenesis and beige-like features in subcutaneous adipocytes from overweight subjects

Eicosapentaenoic acid (EPA), a n-3 long-chain polyunsaturated fatty acid, has been reported to have beneficial effects in obesity-associated metabolic disorders. The objective of the present study was to determine the effects of EPA on the regulation of genes involved in lipid metabolism, and the ability of EPA to induce mitochondrial biogenesis and beiging in subcutaneous adipocytes from overweight subjects. Fully differentiated human subcutaneous adipocytes from overweight females (BMI: 28.1-29.8kg/m²) were treated with EPA (100-200 μM) for 24 h. Changes in mRNA expression levels of genes involved in lipogenesis, fatty acid oxidation and mitochondrial biogenesis were determined by qRT-PCR. Mitochondrial content was evaluated using MitoTracker® Green stain. The effects on peroxisome proliferator-activated receptor gamma, co-activator 1 alpha (PGC-1α) and AMP-activated protein kinase (AMPK) were also characterized. EPA down-regulated lipogenic genes expression while up-regulated genes involved in fatty acid oxidation. Moreover, EPA-treated adipocytes showed increased mitochondrial content, accompanied by an up-regulation of nuclear respiratory factor-1, mitochondrial transcription factor A and cytochrome c oxidase IV mRNA expression. EPA also promoted the activation of master regulators of mitochondrial biogenesis such as sirtuin 1, PGC1-α and AMPK. In parallel, EPA induced the expression of genes that typify beige adipocytes such as fat determination factor PR domain containing 16, uncoupling protein 1 and cell death-inducing DFFA-like effector A, T-Box protein 1 and CD137. Our results suggest that EPA induces a remodeling of adipocyte metabolism preventing fat storage and promoting fatty acid oxidation, mitochondrial biogenesis and beige-like markers in human subcutaneous adipocytes from overweight subjects.

Eicosapentaenoic acid ameliorates hyperglycemia in high-fat diet-sensitive diabetes mice in conjunction with restoration of hypoadiponectinemia

Background/Objective:

Eicosapentaenoic acid (EPA) exerts pleiotropic effects on metabolic disorders such as atherosclerosis and dyslipidemia, but its effectiveness in the treatment of type 2 diabetes mellitus remains controversial.

Methods:

We examined the antidiabetic effect of EPA in insulin receptor mutant (Insr^P1195L/+) mice that exhibit high-fat diet (HFD)-dependent hyperglycemia.

Results:

EPA supplementation was found to alleviate hyperglycemia of Insr^P1195L/+ mice fed HFD (Insr^P1195L/+/HFD mice), which was accompanied by amelioration of increased gluconeogenesis and impaired insulin signaling, as assessed by glucose-6-phosphatase (G6pc) expression on refeeding and insulin-induced phosphorylation of Akt in the liver, respectively. We found that serum levels of adiponectin, the antidiabetic adipokine, were decreased by HFD along with the body weight gain in Insr^P1195L/+ mice but not in wild-type mice, suggesting that Insr^P1195L/+ mice are prone to hypoadiponectinemia in response to obesity. Interestingly, the blood glucose levels of Insr^P1195L/+ mice were in reverse proportion to their serum adiponectin levels and EPA supplementation ameliorated their hyperglycemia in conjunction with the restoration of hypoadiponectinemia.

Conclusions:

EPA exerts an antidiabetic effect in Insr^P1195L/+/HFD mice, an HFD-sensitive, insulin-resistant animal model, possibly through its action against hypoadiponectinemia.

Fasting and postprandial regulation of the intracellular localization of adiponectin and of adipokines secretion by dietary fat in rats

Background/Objective:

Dietary fat sources modulate fasting serum concentration of adipokines, particularly adiponectin. However, previous studies utilized obese animals in which adipose tissue function is severely altered. Thus, the present study aimed to assess the postprandial regulation of adipokine secretion in nonobese rats that consumed high-fat diet (HFD) composed of different types of fat for a short time.

Methods:

The rats were fed a control diet or a HFD containing coconut, safflower or soybean oil (rich in saturated fatty acid, monounsaturated fatty acid or polyunsaturated fatty acid, respectively) for 21 days. The serum concentrations of adiponectin, leptin, retinol, retinol-binding protein-4 (RBP-4), visfatin and resistin were determined at fasting and after refeeding. Adiponectin multimerization and intracellular localization, as well as the expression of endoplasmic reticulum (ER) chaperones and transcriptional regulators, were evaluated in epididymal white adipose tissue.

Results:

In HFD-fed rats, serum adiponectin was significantly decreased 30 min after refeeding. With coconut oil, all three multimeric forms were reduced; with safflower oil, only the high-molecular-weight (HMW) and medium-molecular-weight (MMW) forms were decreased; and with soybean oil, only the HMW form was diminished. These reductions were due not to modifications in mRNA abundance or adiponectin multimerization but rather to an increment in intracellular localization at the ER and plasma membrane. Thus, when rats consumed a HFD, the type of dietary fat differentially affected the abundance of endoplasmic reticulum resident protein 44 kDa (ERp44), sirtuin 1 (SIRT1) and peroxisome proliferator-activated receptor-γ (PPARγ) mRNAs, all of which are involved in the post-translational processing of adiponectin required for its secretion.

Leptin, RBP-4, resistin and visfatin serum concentrations did not change during fasting, whereas modest alterations were observed after refeeding.

Conclusions:

The short-term consumption of a HFD affected adiponectin localization in adipose tissue, thereby decreasing its secretion to a different magnitude depending on the dietary fat source. Evaluating the fasting serum concentration of adipokines was not sufficient to identify alterations in their secretion, whereas postprandial values provided additional information as dynamic indicators.

Does Fish Oil Have an Anti-Obesity Effect in Overweight/Obese Adults? A Meta-Analysis of Randomized Controlled Trials

Context

Accumulating evidence has suggested favorable effects of fish oil on weight loss in animal experiments; however, findings remain inconsistent in humans.

Objects

The meta-analysis was performed to investigate the influence of fish oil on some parameters of body composition in overweight/obese adults.

Design

Human randomized, placebo-controlled trials were identified by a systematic search of Embase, PubMed, the Cochrane Library, web of science and reference lists of related reviews and articles. The random-effects model was used to estimate the calculated results.

Results

In total, 21 studies with 30 study arms were included in this analysis. Calculated results of the meta-analysis demonstrated that fish oil had no effect on reducing body weight (overall SMD = -0.07, 95% CI -0.21 to 0.07, P = 0.31) and BMI (overall SMD = -0.09, 95% CI -0.22 to 0.03, P = 0.14) whether alone or combined with life modification intervention in overweight/obese subjects. However, waist circumference was significantly reduced (SMD = -0.23, 95% CI -0.40 to -0.06, P = 0.008) in those with fish oil supplementation combined with life modification intervention. Waist hip ratio (WHR) was significantly reduced (overall SMD = -0.52 95% CI -0.76 to -0.27, P < 0.0005) in fish oil supplemented individuals with or without combination life modification intervention.

Conclusion

Current evidence cannot support an exact anti-obesity role of n-3 polyunsaturated fatty acids (PUFAs) in overweight/obese subjects. However, these subjects may benefit from reducing abdominal fat with fish oil supplementation especially when combined with life modification intervention. Further large-scale and long-term clinical trials are needed to gain definite conclusions.

N-3 Polyunsaturated Fatty Acids and Inflammation in Obesity: Local Effect and Systemic Benefit

Overwhelming consensus emerges among countless evidences that obesity is characterized by a chronic low-grade inflammation in the adipose tissue (AT), which subsequently develops into a systemic inflammatory state contributing to obesity-associated diseases. N-3 Polyunsaturated fatty acids (n-3 PUFA), known as important modulators participating in inflammatory process, turn out to be an effective mitigating strategy dealing with local and systemic inflammation observed in obesity. Some of the effects of n-3 PUFA are brought about by regulation of gene expression through interacting with nuclear receptors and transcription factors; other effects are elicited by modulation of the amount and type of mediator derived from PUFAs. The metabolic effects of n-3 PUFA mainly result from their interactions with several organ systems, not limited to AT. Notably, the attenuation of inflammation in hard-hit AT, in turn, contributes to reducing circulating concentrations of proinflammatory cytokines and detrimental metabolic derivatives, which is beneficial for the function of other involved organs. The present review highlights a bridging mechanism between n-3 PUFA-mediated inflammation relief in AT and systemic benefits.

Omega-3 fatty acids and adipose tissue function in obesity and metabolic syndrome

The n-3 long-chain polyunsaturated fatty acids (n-3 PUFAs) such as eicosapentaenoic (EPA) and docosahexaenoic (DHA) have been reported to improve obesity-associated metabolic disorders including chronic inflammation, insulin resistance and dyslipidaemia. Growing evidence exits about adipose tissue as a target in mediating the beneficial effects of these marine n-3 PUFAs in adverse metabolic syndrome manifestations. Therefore, in this manuscript we focus in reviewing the current knowledge about effects of marine n-3 PUFAs on adipose tissue metabolism and secretory functions. This scope includes n-3 PUFAs actions on adipogenesis, lipogenesis and lipolysis as well as on fatty acid oxidation and mitochondrial biogenesis. The effects of n-3 PUFAs on adipose tissue glucose uptake and insulin signaling are also summarized. Moreover, the roles of peroxisome proliferator-activated receptor γ (PPARγ) and AMPK activation in mediating n-3 PUFAs actions on adipose tissue functions are discussed. Finally, the mechanisms underlying the ability of n-3 PUFAs to prevent and/or ameliorate adipose tissue inflammation are also revised, focusing on the role of n-3 PUFAs-derived specialized proresolving lipid mediators such as resolvins, protectins and maresins.

Circulating irisin and glucose metabolism in overweight/obese women: effects of α-lipoic acid and eicosapentaenoic acid

Irisin is a myokine/adipokine with potential role in obesity and diabetes. The objectives of the present study were to analyse the relationship between irisin and glucose metabolism at baseline and during an oral glucose tolerance test (OGTT) and to determine the effects of eicosapentaenoic acid (EPA) and/or α-lipoic acid treatment on irisin production in cultured human adipocytes and in vivo in healthy overweight/obese women following a weight loss program. Seventy-three overweight/obese women followed a 30% energy-restricted diet supplemented without (control) or with EPA (1.3 g/day), α-lipoic acid (0.3 g/day) or both EPA + α-lipoic acid (1.3 + 0.3 g/day) during 10 weeks. An OGTT was performed at baseline. Moreover, human adipocytes were treated with EPA (100-200 μM) or α-lipoic acid (100-250 μM) during 24 h. At baseline plasma, irisin circulating levels were positively associated with glucose levels; however, serum irisin concentrations were not affected by the increment in blood glucose or insulin during the OGTT. Treatment with α-lipoic acid (250 μM) upregulated Fndc5 messenger RNA (mRNA) and irisin secretion in cultured adipocytes. In overweight/obese women, irisin circulating levels decreased significantly after weight loss in all groups, while no additional differences were induced by EPA or α-lipoic acid supplementation. Moreover, plasma irisin levels were positively associated with higher glucose concentrations at beginning and at endpoint of the study. The data from the OGTT suggest that glucose is not a direct contributing factor of irisin release. The higher irisin levels observed in overweight/obese conditions could be a protective response of organism to early glucose impairments.

Mechanisms of enhanced insulin secretion and sensitivity with n-3 unsaturated fatty acids

The widespread acceptance that increased dietary n-3 polyunsaturated fatty acids (PUFAs), especially α-linolenic acid (ALA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), improve health is based on extensive studies in animals, isolated cells and humans. Visceral adiposity is part of the metabolic syndrome, together with insulin resistance, dyslipidemia, hypertension and inflammation. Alleviation of metabolic syndrome requires normalization of insulin release and responses. This review assesses our current knowledge of the mechanisms that allow n-3 PUFAs to improve insulin secretion and sensitivity. EPA has been more extensively studied than either ALA or DHA. The complex actions of EPA include increased G-protein-receptor-mediated release of glucagon-like peptide 1 (GLP-1) from enteroendocrine L-cells in the intestine, up-regulation of the apelin pathway and down-regulation of other control pathways to promote insulin secretion by the pancreatic β-cells, together with suppression of inflammatory responses to adipokines, inhibition of peroxisome proliferator-activated receptor α actions and prevention of decreased insulin-like growth factor-1 secretion to improve peripheral insulin responses. The receptors involved and the mechanisms of action probably differ for ALA and DHA, with antiobesity effects predominating for ALA and anti-inflammatory effects for DHA. Modifying both GLP-1 release and the actions of adipokines by n-3 PUFAs could lead to additive improvements in both insulin secretion and sensitivity.

Effects of dietary eicosapentaenoic acid (EPA) supplementation in high-fat fed mice on lipid metabolism and apelin/APJ system in skeletal muscle

Various studies have shown that eicosapentaenoic acid (EPA) has beneficial effects on obesity and associated disorders. Apelin, the ligand of APJ receptor also exerts insulin-sensitizing effects especially by improving muscle metabolism. EPA has been shown to increase apelin production in adipose tissue but its effects in muscle have not been addressed. Thus, the effects of EPA supplementation (36 g/kg EPA) in high-fat diet (HFD) (45% fat, 20% protein, 35% carbohydrate) were studied in mice with focus on muscle lipid metabolism and apelin/APJ expression. Compared with HFD mice, HFD+EPA mice had significantly less weight gain, fat mass, lower blood glucose, insulinemia and hepatic steatosis after 10 weeks of diet. In addition, EPA prevented muscle metabolism alterations since intramuscular triglycerides were decreased and β-oxidation increased. In soleus muscles of HFD+EPA mice, apelin and APJ expression were significantly increased compared to HFD mice. However, plasma apelin concentrations in HFD and HFD+EPA mice were similar. EPA-induced apelin expression was confirmed in differentiated C2C12 myocytes but in this model, apelin secretion was also increased in response to EPA treatment. In conclusion, EPA supplementation in HFD prevents obesity and metabolic alterations in mice, especially in skeletal muscle. Since EPA increases apelin/APJ expression in muscle, apelin may act in a paracrine/autocrine manner to contribute to these benefical effects.

Omega-3 fatty acids improve glucose metabolism without effects on obesity values and serum visfatin levels in women with polycystic ovary syndrome

OBJECTIVE

Polycystic ovary syndrome (PCOS) is the most common female endocrine disorder. Affected women present a higher risk of type 2 diabetes. The objectives of this study were to investigate the effects of omega-3 fatty acids on obesity status, insulin resistance, and serum levels of visfatin in PCOS patients.

METHODS

This double-blind, randomized, controlled clinical trial was conducted on 61 women who were diagnosed with PCOS, had a body mass index (BMI) between 25 and 40 kg/m(2), and were from 20-35 years old. Thirty of the subjects had taken four 1-g omega-3 fatty acids capsules per day, providing 1200 mg n-3 long chain polyunsaturated fatty acids (n-3 LC PUFA), and 31 were given a placebo over 8 weeks. Fasting blood samples, anthropometric measurements, and dietary intake data were collected at the baseline and at the end of the trial. Data were analyzed by independent t test, paired t test, Pearson correlation test, and analysis of covariance.

RESULTS

Omega-3 fatty acids had no significant effects on weight, BMI, waist circumference, and waist to hip ratio at the end of the study. Omega-3 fatty acids significantly decreased glucose (by 11.4%, p < 0.001), insulin (by 8.4%, p < 0.05), and homeostatic model assessment for insulin resistance (by 21.8%, p < 0.001) compared with placebo. Changes in serum visfatin levels were not significant in either of the groups.

CONCLUSION

Omega-3 fatty acids improved insulin sensitivity in PCOS patients. This beneficial effect was not associated with alteration in anthropometric measurements and serum visfatin levels.

Influence of quercetin-rich onion peel extracts on adipokine expression in the visceral adipose tissue of rats

We examined the effects of quercetin-rich onion peel extract supplementation on adipokine expressions from adipose tissues in a diet-induced obese animal model. Male Sprague-Dawley rats (n = 24) were randomly assigned into control (n = 8), high fat diet (HF, n = 8) and high fat diet with onion peel extract (HFOE, n = 8). After 8 weeks, serum biochemical parameters, weights of adipose tissues (epididymal, perirenal and mesenteric fats) and adipokine mRNA levels (adiponectin, IL (interleukin)-6 and visfatin) along with PPAR (peroxisome proliferator-activated receptor) γ2 from adipose tissues were measured. After the 8 week supplementation, mesenteric fat weights were lower in the HFOE group than the HF group (p < 0.05). Adiponectin mRNA levels (mesenteric fats) were remarkably higher in the HFOE group than the other groups (p < 0.05 for both). Levels of PPARγ2 mRNA (mesenteric fats) were significantly higher in the HF group (p < 0.05) than those in the control group, but those in the HFOE group were not different from those in the control group. The IL-6 mRNA levels (perirenal and mesenteric fats) were higher in the HF and HFOE groups, but those in the HFOE group were slightly lower than those in the HF group. In conclusion, quercetin-rich onion peel extract supplementation influenced adipokine expressions, particularly from mesenteric fat, addressing the modulatory effect of this substance on obesity-induced inflammation.

Apelin, diabetes, and obesity

Apelin is a peptide known as the ligand of the G-protein-coupled receptor APJ. Several active apelin forms exist such as apelin-36, apelin-17, apelin-13, and the pyroglutamated form of apelin-13. Apelin and APJ are expressed in the central nervous system, particularly in the hypothalamus and in many peripheral tissues. Apelin has been shown to be involved in the regulation of cardiovascular and fluid homeostasis, food intake, cell proliferation, and angiogenesis. In addition to be an ubiquitous peptide, apelin is also produced and secreted by adipocytes and thus considered as an adipokine. This has opened a new field of investigation establishing a link between apelin and metabolic disorders (obesity, type 2 diabetes, etc.) which is the focus of the present review. Several studies, but not all, have reported an increase of plasma apelin concentrations in humans and in animal models with different metabolic pathologies. Moreover, important roles for apelin both in glucose and lipid metabolism have been highlighted as well as the associated signaling pathways. Apelin appears as a beneficial adipokine with anti-obesity and anti-diabetic properties and thus as a promising therapeutic target in metabolic disorders.

(n-3) Fatty acids alleviate adipose tissue inflammation and insulin resistance: mechanistic insights

Obesity is associated with the metabolic syndrome, a significant risk factor for developing type 2 diabetes and cardiovascular diseases. Chronic low-grade inflammation occurring in the adipose tissue of obese individuals is causally linked to the pathogenesis of insulin resistance and the metabolic syndrome. Although the exact trigger of this inflammatory process is unknown, adipose tissue hypoxia, endoplasmic reticular stress, and saturated fatty acid-mediated activation of innate immune processes have been identified as important processes in these disorders. Furthermore, macrophages and T lymphocytes have important roles in orchestrating this immune process. Although energy restriction leading to weight loss is the primary dietary intervention to reverse these obesity-associated metabolic disorders, other interventions targeted at alleviating adipose tissue inflammation have not been explored in detail. In this regard, (n-3) PUFA of marine origin both prevent and reverse high-fat-diet-induced adipose tissue inflammation and insulin resistance in rodents. We provide an update on the pathogenesis of adipose tissue inflammation and insulin resistance in obesity and discuss potential mechanisms by which (n-3) PUFA prevent and reverse these changes and the implications in human health.

Curcumin prevents leptin raising glucose levels in hepatic stellate cells by blocking translocation of glucose transporter-4 and increasing glucokinase

BACKGROUND AND PURPOSE

Hyperleptinemia is commonly found in obese patients, associated with non-alcoholic steatohepatitis and hepatic fibrosis. Hepatic stellate cells (HSCs) are the most relevant effectors during hepatic fibrogenesis. We recently reported that leptin stimulated HSC activation, which was eliminated by curcumin, a phytochemical from turmeric. This study was designed to explore the underlying mechanisms, focusing on their effects on intracellular glucose in HSCs. We hypothesized that leptin stimulated HSC activation by elevating the level of intracellular glucose, which was eliminated by curcumin by inhibiting the membrane translocation of glucose transporter-4 (GLUT4) and inducing the conversion of glucose to glucose-6-phosphate (G-6-P).

EXPERIMENTAL APPROACH

Levels of intracellular glucose were measured in rat HSCs and immortalized human hepatocytes. Contents of GLUT4 in cell fractions were analysed by Western blotting analyses. Activation of signalling pathways was assessed by comparing phosphorylation levels of protein kinases.

KEY RESULTS

Leptin elevated the level of intracellular glucose in cultured HSCs, which was diminished by curcumin. Curcumin suppressed the leptin-induced membrane translocation of GLUT4 by interrupting the insulin receptor substrates/phosphatidyl inositol 3-kinase/AKT signalling pathway. Furthermore, curcumin stimulated glucokinase activity, increasing conversion of glucose to G-6-P.

CONCLUSIONS AND IMPLICATIONS

Curcumin prevented leptin from elevating levels of intracellular glucose in activated HSCs in vitro by inhibiting the membrane translocation of GLUT4 and stimulating glucose conversion, leading to the inhibition of HSC activation. Our results provide novel insights into mechanisms of curcumin in inhibiting leptin-induced HSC activation.

The role of adipose tissue in mediating the beneficial effects of dietary fish oil

Fish oil improves several features of metabolic syndrome (MetS), such as dyslipidemia, insulin resistance and hepatic steatosis. Fish oil may mediate some of its beneficial effects by modulating the storage and/or secretory functions of adipose tissue (AT). The storage of triglycerides in AT is regulated by the availability of free fatty acids and the degree of lipolysis in AT. Fish oil has been shown to reduce lipolysis in several studies, indicating improved triglyceride storage. Importantly, AT secretes a variety of adipokines and fish oil feeding is associated with remarkable changes in the plasma levels of two key adipokines, adiponectin and leptin. Much attention has been focused on the contribution of adiponectin in fish oil-mediated improvements in MetS. However, emerging evidence also indicates a role of leptin in modulating the components of the MetS upon fish oil feeding. In addition to improving the storage and secretory functions of AT, fish oil, and the n-3 fatty acids found in fish oil, has been shown to reduce inflammation in AT. These effects may be in part a result of activation of peroxisome proliferator-activated receptor γ or inhibition of Toll-like receptor 4. Thus, there is compelling evidence that fish oil mediates its beneficial effects on MetS by improving AT storage and secretory functions and by reducing inflammation.

Role of obesity-associated dysfunctional adipose tissue in cancer: a molecular nutrition approach

Obesity is a complex disease caused by the interaction of a myriad of genetic, dietary, lifestyle and environmental factors, which favors a chronic positive energy balance, leading to increased body fat mass. There is emerging evidence of a strong association between obesity and an increased risk of cancer. However, the mechanisms linking both diseases are not fully understood. Here, we analyze the current knowledge about the potential contribution that expanding adipose tissue in obesity could make to the development of cancer via dysregulated secretion of pro-inflammatory cytokines, chemokines and adipokines such as TNF-α, IL-6, leptin, adiponectin, visfatin and PAI-1. Dietary factors play an important role in the risk of suffering obesity and cancer. The identification of bioactive dietary factors or substances that affect some of the components of energy balance to prevent/reduce weight gain as well as cancer is a promising avenue of research. This article reviews the beneficial effects of some bioactive food molecules (n-3 PUFA, CLA, resveratrol and lipoic acid) in energy metabolism and cancer, focusing on the molecular mechanisms involved, which may provide new therapeutic targets in obesity and cancer.

Drug discovery in a multidimensional world: systems, patterns, and networks

Despite great strides in revealing and understanding the physiological and molecular bases of cardiovascular disease, efforts to translate this understanding into needed therapeutic interventions continue to lag far behind the initial discoveries. Although pharmaceutical companies continue to increase investments into research and development, the number of drugs gaining federal approval is in decline. Many factors underlie these trends, and a vast number of technological and scientific innovations are being sought through efforts to reinvigorate drug discovery pipelines. Recent advances in molecular profiling technologies and development of sophisticated computational approaches for analyzing these data are providing new, systems-oriented approaches towards drug discovery. Unlike the traditional approach to drug discovery which is typified by a one-drug-one-target mindset, systems-oriented approaches to drug discovery leverage the parallelism and high-dimensionality of the molecular data to construct more comprehensive molecular models that aim to model broader bimolecular systems. These models offer a means to explore complex molecular states (e.g., disease) where thousands to millions of molecular entities comprising multiple molecular data types (e.g., proteomics and gene expression) can be evaluated simultaneously as components of a cohesive biomolecular system. In this paper, we discuss emerging approaches towards systems-oriented drug discovery and contrast these efforts with the traditional, unidimensional approach to drug discovery. We also highlight several applications of these system-oriented approaches across various aspects of drug discovery, including target discovery, drug repositioning and drug toxicity. When available, specific applications to cardiovascular drug discovery are highlighted and discussed.

Regulation of adipokine secretion by n-3 fatty acids

Obesity leads to several chronic morbidities including type 2 diabetes, dyslipidaemia, atherosclerosis and hypertension, which are major components of the metabolic syndrome. White adipose tissue (WAT) metabolism and WAT-derived factors (fatty acids and adipokines) play an important role in the development of these metabolic disturbances. In fact, dysregulated adipokine secretion from the expanded WAT of obese individuals contributes to the development of systemic low-grade inflammation, insulin resistance and metabolic syndrome. The n-3 PUFA EPA and DHA have been widely reported to have protective effects in a range of chronic inflammatory conditions including obesity. In fact, n-3 PUFA have been shown to ameliorate low-grade inflammation in adipose tissue associated with obesity and up-regulate mitochondrial biogenesis and induce beta-oxidation in WAT in mice. Moreover, the ability of n-3 PUFA to regulate adipokine gene expression and secretion has been observed both in vitro and in vivo in rodents and human subjects. The present article reviews: (1) the physiological role of adiponectin, leptin and pre-B cell colony-enhancer factor/visfatin, three adipokines with immune-modulatory properties involved in the regulation of metabolism and insulin sensitivity and (2) the actions of n-3 PUFA on these adipokines focusing on the underlying mechanisms and the potential relationship with the beneficial effects of these fatty acids on obesity-associated metabolic disorders. It can be concluded that the ability of n-3 PUFA to improve obesity and insulin resistance conditions partially results from the modulation of WAT metabolism and the secretion of bioactive adipokines including leptin, adiponectin and visfatin.

Lack of direct insulin-like action of visfatin/Nampt/PBEF1 in human adipocytes

Visfatin, a protein identified as a secretion product of visceral fat in humans and mice, is also expressed in different anatomical locations, and is known as pre-B cell-colony enhancing factor (PEBF1). It is also an enzyme displaying nicotinamide phosphoribosyltransferase activity (Nampt). The evidence that levels of visfatin correlate with visceral fat mass has been largely debated and widely extended to other regulations in numerous clinical studies and in diverse animal models. On the opposite, the initial findings regarding the capacity of visfatin/Nampt/PEBF1 to bind and to activate the insulin receptor have been scarcely reproduced, and even were contradicted in recent reports. Since the putative insulin mimicking effects of visfatin/Nampt/PEBF1 have never been tested on mature human adipocytes, at least to our knowledge, we tested different human visfatin batches on human fat cells freshly isolated from subcutaneous abdominal fat and exhibiting high insulin responsiveness. Up to 10 nM, visfatin was devoid of clear activatory action on glucose transport in human fat cells while, in the same conditions, insulin increased by more than threefold the basal 2-deoxyglucose uptake. Moreover, visfatin was unable to mimic the lipolysis inhibition induced by insulin. Visfatin definitively cannot be considered as a direct activator of insulin signalling in human fat cells. Nevertheless itsin vivo effects on insulin release and on glucose handling deserve to further study the role of this multifunctional extracellular enzyme in obese and diabetic states.