Chronic Oleoylethanolamide Treatment Decreases Hepatic Triacylglycerol Level in Rat Liver by a PPARγ/SREBP-Mediated Suppression of Fatty Acid and Triacylglycerol Synthesis

Oleoylethanolamide (OEA) is a naturally occurring bioactive lipid belonging to the family of N-acylethanolamides. A variety of beneficial effects have been attributed to OEA, although the greater interest is due to its potential role in the treatment of obesity, fatty liver, and eating-related disorders. To better clarify the mechanism of the antiadipogenic effect of OEA in the liver, using a lipidomic study performed by ¹H-NMR, LC-MS/MS and thin-layer chromatography analyses we evaluated the whole lipid composition of rat liver, following a two-week daily treatment of OEA (10 mg kg⁻¹ i.p.). We found that OEA induced a significant reduction in hepatic triacylglycerol (TAG) content and significant changes in sphingolipid composition and ceramidase activity. We associated the antiadipogenic effect of OEA to decreased activity and expression of key enzymes involved in fatty acid and TAG syntheses, such as acetyl-CoA carboxylase, fatty acid synthase, diacylglycerol acyltransferase, and stearoyl-CoA desaturase 1. Moreover, we found that both SREBP-1 and PPARγ protein expression were significantly reduced in the liver of OEA-treated rats. Our findings add significant and important insights into the molecular mechanism of OEA on hepatic adipogenesis, and suggest a possible link between the OEA-induced changes in sphingolipid metabolism and suppression of hepatic TAG level.     

The effects of oleoylethanolamide,an endogenous PPAR‐α agonist,on risk factors for NAFLD: A systematic review

Non‐alcoholic fatty liver disease (NAFLD) is the most prevalent chronic liver disease. Recently, some novel compounds have been investigated for the prevention and treatment of NAFLD. Oleoylethanolamide (OEA), an endogenous PPAR‐α agonist, has exhibited a plethora of pharmacological properties for the treatment of obesity and other obesity‐associated metabolic complications. This systematic review was performed with a focus on the effects of OEA on the risk factors for NAFLD. PubMed, Scopus, Embase, ProQuest, and Google Scholar databases were searched up to December 2018 using relevant keywords. All articles written in English evaluating the effects of OEA on the risk factors for NAFLD were eligible for the review. The evidence reviewed in this article illustrates that OEA regulates multiple biological processes associated with NAFLD, including lipid metabolism, inflammation, oxidative stress, and energy homeostasis through different mechanisms. In summary, many beneficial effects of OEA have led to the understanding that OEA may be an effective therapeutic strategy for the management of NAFLD. Although a wide range of studies have demonstrated the most useful effects of OEA on NAFLD and the associated risk factors, further clinical trials, from both in vivo studies and in vitro experiments, are warranted to verify these outcomes.     

'Entourage' effects of N-palmitoylethanolamide and N-oleoylethanolamide on vasorelaxation to anandamide occur through TRPV1 receptors

Background and purpose:

The endocannabinoid N-arachidonoylethanolamide (anandamide) is co-synthesized with other N-acylethanolamides, namely N-palmitoylethanolamide (PEA) and N-oleoylethanolamide (OEA), which have been shown to potentiate anandamide responses (so-called ‘entourage effects'') in non-vascular tissues. It remains unclear whether such interactions occur in the circulation.

Experimental approach:

In rat isolated small mesenteric arteries, the effects of PEA and OEA on relaxation to anandamide and tissue contents of the N-acylethanolamides were examined under myographic conditions.

Key results:

Anandamide-induced relaxation was potentiated by pretreatment with PEA (10 μM) or OEA (1 μM), or in combination. The potentiation by PEA and OEA was endothelium-independent and abolished by treatment with capsaicin (10 μM), which desensitizes the transient receptor potential vanilloid type 1 (TRPV1) receptor system, or by the TRPV1 receptor antagonist, N-(3-methoxyphenyl)-4-chlorocinnamide (SB366791) (2 μM). It was also observed at molar ratios of anandamide and PEA (or OEA) similar to those found in mesenteric arteries. PEA and inhibition of anandamide hydrolysis by 3′-carbamoyl-biphenyl-3-yl-cyclohexylcarbamate (URB597) (1 μM) additively potentiated anandamide responses. On the other hand, PEA and OEA also induced vasorelaxation per se (rank order of potency: anandamide>OEA>PEA), but relaxation to the three N-acylethanolamides displayed different sensitivity to treatment with capsaicin, SB366791 and URB597. For example, relaxations to anandamide and OEA, but not PEA, were attenuated by both capsaicin and SB366791.

Conclusion and implications:

This study shows that PEA and OEA potentiate relaxant responses to anandamide through TRPV1 receptors in rat small mesenteric arteries. The congeners also induce vasorelaxation per se, suggesting a function for the N-acylethanolamides in vascular control.     

Endogenous and synthetic agonists of GPR119 differ in signalling pathways and their effects on insulin secretion in MIN6c4 insulinoma cells

Background and purpose:     

Oleoylethanolamide: The role of a bioactive lipid amide in modulating eating behaviour

Fatty acid ethanolamides are lipid mediators that regulate a plethora of physiological functions. One such bioactive lipid mediator, oleoylethanolamide (OEA), is a potent agonist of the peroxisome proliferator‐activated receptor‐alpha (PPAR‐α), which modulates increased expression of the fatty acid translocase CD36 that enables the regulation of feeding behaviour. Consumption of dietary fat rich in oleic acid activates taste receptors in the gut activating specific enzymes that lead to the formation of OEA. OEA further combines with PPAR‐α to enable fat oxidation in the liver, resulting in enhanced energy production. Evidence suggests that sustained ingestion of a high‐fat diet abolishes the anorexic signal of OEA. Additionally, malfunction of the enterocyte that transforms oleic acid produced during fat digestion into OEA might be responsible for reduced satiety and hyperphagia, resulting in overweight and obesity. Thus, OEA anorectic signalling may be an essential element of the physiology and metabolic system regulating dietary fat intake and obesity. The evidence reviewed in this article indicates that intake of oleic acid, and thereby the resulting OEA imparting anorexic properties, is dependent on CD36, PPAR‐α, enterocyte fat sensory receptors, histamine, oxytocin and dopamine; leading to increased fat oxidation and enhanced energy expenditure to induce satiety and increase feeding latency; and that a disruption in any of these systems will cease/curb fat‐induced satiety.     

油酰乙醇胺对脂多糖诱导的THP-1细胞炎症因子表达的影响

目的探讨油酰乙醇胺(OEA)对细菌脂多糖(LPS)诱导的人急性白血病单核细胞(THP-1)中前炎症因子TNF-α、IL-1β、IL-6表达的影响,并初步探讨OEA作为过氧化物酶体增殖物激活受体-α(PPAR-α)激动剂参与对炎症调节的作用机制。方法体外培养的THP-1细胞,分别加入不同浓度的OEA(10,20,40μmol/L)或非诺贝特(100μmol/L)共同孵育1 h后,用1μg/mL LPS分别诱导6或24 h。采用RT-PCR、实时定量PCR和酶联免疫吸附检测测定细胞中TNF-α、IL-1β、IL-6 mRNA和蛋白的表达的变化,并使用实时定量PCR及Western blot方法检测PPAR-α及Toll样受体4(TLR4)的mRNA和蛋白的表达。结果相对于正常THP-1细胞,LPS诱导后细胞中炎症因子(TNF-α、IL-1β、IL-6)表达明显增加。OEA对TNF-α、IL-1β、IL-6 mRNA和蛋白的表达有抑制作用,并呈现出一定的剂量依赖性。且OEA在激活PPAR-α表达的同时能够抑制TLR4的表达。结论 OEA对LPS诱导的炎症反应有抑制作用,其机制可能与激活PPAR-α,下调TLR4的表达有关。     

油酰乙醇胺对小鼠局灶性脑缺血的保护作用

目的观察新型PPARα激动剂油酰乙醇胺(oleoyleth-anolamide,OEA)对小鼠局灶性脑缺血损伤的保护作用及特点。方法线栓法制备小鼠大脑中动脉栓塞模型诱导脑缺血。OEA(10、20、40mg·kg-1)在术前3d开始每天灌胃给药1次;或在缺血前0.5h、1h、再灌注同时、再灌后1h,各单次灌胃给予OEA40mg·kg-1。脑缺血1.5h,再灌注24h后,测定小鼠神经功能缺失评分、脑梗死体积、脑水肿等评定脑缺血损伤的指标。结果OEA(20、40mg·kg-1)术前多次给药及OEA(40mg·kg-1)缺血前0.5h或再灌注同时单次给药可明显改善小鼠神经功能损伤,减小脑梗死体积和减轻脑水肿程度,且以再灌注同时单次给药效果最为明显。结论OEA剂量及时间依赖性的保护小鼠局灶性脑缺血急性损伤,有效剂量为20mg·kg-1和40mg·kg-1,最佳治疗时间点为再灌注同时。     

The identification of peroxisome proliferator-activated receptor alpha-independent effects of oleoylethanolamide on intestinal transit in mice

Abstract  Oleoylethanolamide (OEA) is an endogenous lipid produced in the intestine that mediates satiety by activation of peroxisome proliferator-activated receptor alpha (PPARα). OEA inhibits gastric emptying and intestinal motility, but the mechanism of action remains to be determined. We investigated whether OEA inhibits intestinal motility by activation of PPARα. PPARα immunoreactivity was examined in whole mount preparations of mouse gastrointestinal (GI) tract. The effect of OEA on motility was assessed in wildtype, PPARα, cannabinoid CB₁ receptor and CB₂ receptor gene-deficient mice and in a model of accelerated GI transit. In addition, the effect of OEA on motility was assessed in mice injected with the PPARα antagonist GW6471, transient receptor potential vanilloid 1 antagonist SB366791 or the glucagon-like peptide 1 antagonist exendin-3(9-39) amide. PPARα immunoreactivity was present in neurons in the myenteric and submucosal plexuses throughout the GI tract. OEA inhibited upper GI transit in a dose-dependent manner, but was devoid of an effect on whole gut transit or colonic propulsion. OEA-induced inhibition of motility was still present in PPARα, CB₁ and CB₂ receptor gene-deficient mice and in the presence of GW6471, SB366791 and exendin-3(9-39) amide, suggesting neither PPARα nor the cannabinoids and other likely receptors are involved in mediating the effects of OEA. OEA blocked stress-induced accelerated upper GI transit at a dose that had no effect on physiological transit. We show that PPARα is found in the enteric nervous system, but our results suggest that PPARα is not involved in the suppression of motility by OEA.     

油酰乙醇胺对高脂血症大鼠降血脂及肝脏的保护作用

目的观察油酰乙醇胺(OEA)对高脂血症模型大鼠降血脂及肝脏保护作用。方法高脂饮食建立高脂血症大鼠模型,分别观察OEA(10,203,0 mg/kg)对高脂血症大鼠的血清胆固醇(TC)、甘油三酯(TG)、低密度脂蛋白胆固醇(LDL-C)、高密度脂蛋白胆固醇(HDL-C)、谷丙转氨酶(ALT)、肝重和肝脏系数、肝脏丙二醛(MDA)、谷胱甘肽过氧化物酶(GSH-Px)的影响。制作冰冻切片观察大鼠肝脏脂质变性程度。结果与模型组相比,OEA(20,30mg/kg)具有降血脂作用,同时降低血清ALT、肝脏脂质、肝重和肝脏系数、肝脏MDA水平,升高肝脏GSH-Px活力。结论 OEA能降低高脂血症大鼠血脂、抑制肝脏脂肪沉积,并减轻脂质过氧化物对肝脏的损伤。