anandamide and Fatty-Liver

Phthalates, used as plasticizers, have become a ubiquitous contaminant and have been reported for their potential to induce toxicity in living organisms. Among them, di-isononyl phthalate (DiNP) has been recently used to replace di(2-ethylhexyl) phthalate (DEHP). Nowadays, there is evidence that DiNP is an endocrine-disrupting chemical; however, little is known about its effects on the endocannabinoid system (ECS) and lipid metabolism. Hence, the aim of our study was to investigate the effects of DiNP on the ECS in zebrafish liver and brain and on hepatic lipid storage. To do so, adult female zebrafish were exposed to three concentrations (0.42 µg/L, 4.2 µg/L, and 42 µg/L) of DiNP via water for 3 weeks. Afterwards, we investigated transcript levels for genes involved in the ECS of the brain and liver as well as liver histology and image analysis, Fourier-transform infrared spectroscopy imaging, and measurement of endocannabinoid levels. Our results demonstrate that DiNP upregulates orexigenic signals and causes hepatosteatosis together with deregulation of the peripheral ECS and lipid metabolism. A decrease in the levels of ECS components at the central level was observed after exposure to the highest DiNP concentration tested. These findings suggest that replacement of DEHP with DiNP should be considered with caution because of observed adverse DiNP effects on aquatic organisms.

Topics: Animals; Arachidonic Acids; Brain; Dose-Response Relationship, Drug; Endocannabinoids; Endocrine Disruptors; Fatty Liver; Female; Gene Expression; Glycerides; Lipid Metabolism; Lipoprotein Lipase; Liver; Phospholipase D; Phthalic Acids; Plasticizers; Polyunsaturated Alkamides; Receptor, Cannabinoid, CB1; Receptor, Cannabinoid, CB2; Zebrafish

The xenoestrogen bisphenol A (BPA) is a widespread plasticizer detectable within several ecosystems. BPA is considered a metabolic disruptor, affecting different organs; however, little is known about its mechanism of action in the liver, in which it triggers triglyceride accumulation. Adult zebrafish (Danio rerio) exposed to BPA developed hepatosteatosis, which was associated with an increase in the liver levels of the obesogenic endocannabinoids 2-arachidonoylglycerol and anandamide and a concomitant decrease in palmitoylethanolamide. These changes were associated with variations in the expression of key endocannabinoid catabolic and metabolic enzymes and an increase in the expression of the endocannabinoid receptor cnr1. Acute and chronic in vitro treatments with nano- and micromolar BPA doses showed increased anandamide levels in line with decreased activity of fatty acid amide hydrolase, the main anandamide hydrolytic enzyme, and induced triglyceride accumulation in HHL-5 cells in a CB1-dependent manner. We conclude that BPA is able to produce hepatosteatosis in zebrafish and human hepatocytes by up-regulating the endocannabinoid system.

Topics: Amides; Animals; Arachidonic Acids; Benzhydryl Compounds; Cell Line; Endocannabinoids; Endocrine Disruptors; Ethanolamines; Fatty Liver; Feedback, Physiological; Glycerides; Hepatocytes; Humans; Liver; Palmitic Acids; Phenols; Polyunsaturated Alkamides; Receptor, Cannabinoid, CB1; Triglycerides; Zebrafish; Zebrafish Proteins

Obesity-related insulin resistance contributes to cardiovascular disease. Cannabinoid receptor-1 (CB(1)) blockade improves insulin sensitivity in obese animals and people, suggesting endocannabinoid involvement. We explored the role of hepatic CB(1) in insulin resistance and inhibition of insulin signaling pathways.. Wild-type mice and mice with disruption of CB(1) (CB(1)(-/-) mice) or with hepatocyte-specific deletion or transgenic overexpression of CB(1) were maintained on regular chow or a high-fat diet (HFD) to induce obesity and insulin resistance. Hyperinsulinemic-euglycemic clamp analysis was used to analyze the role of the liver and hepatic CB(1) in HFD-induced insulin resistance. The cellular mechanisms of insulin resistance were analyzed in mouse and human isolated hepatocytes using small interfering or short hairpin RNAs and lentiviral knockdown of gene expression.. The HFD induced hepatic insulin resistance in wild-type mice, but not in CB(1)(-/-) mice or mice with hepatocyte-specific deletion of CB(1). CB(1)(-/-) mice that overexpressed CB(1) specifically in hepatocytes became hyperinsulinemic as a result of reduced insulin clearance due to down-regulation of the insulin-degrading enzyme. However, they had increased hepatic glucose production due to increased glycogenolysis, indicating hepatic insulin resistance; this was further increased by the HFD. In mice with hepatocytes that express CB(1), the HFD or CB(1) activation induced the endoplasmic reticulum stress response via activation of the Bip-PERK-eIF2α protein translation pathway. In hepatocytes isolated from human or mouse liver, CB(1) activation caused endoplasmic reticulum stress-dependent suppression of insulin-induced phosphorylation of akt-2 via phosphorylation of IRS1 at serine-307 and by inducing the expression of the serine and threonine phosphatase Phlpp1. Expression of CB(1) was up-regulated in samples from patients with nonalcoholic fatty liver disease.. Endocannabinoids contribute to diet-induced insulin resistance in mice via hepatic CB(1)-mediated inhibition of insulin signaling and clearance.

Topics: Animals; Arachidonic Acids; Diet, High-Fat; Endocannabinoids; Endoplasmic Reticulum Stress; Fatty Liver; Glucose Intolerance; Humans; Insulin; Insulin Resistance; Liver; Male; Metabolic Clearance Rate; Mice; Mice, Inbred C57BL; Non-alcoholic Fatty Liver Disease; Phosphorylation; Polyunsaturated Alkamides; Proto-Oncogene Proteins c-akt; Receptor, Cannabinoid, CB1; Signal Transduction

The tissue-specific sources and regulated production of physiological signals that modulate food intake are incompletely understood. Previous work showed that L-Fabp(-/-) mice are protected against obesity and hepatic steatosis induced by a high-fat diet, findings at odds with an apparent obesity phenotype in a distinct line of aged L-Fabp(-/-) mice. Here we show that the lean phenotype in L-Fabp(-/-) mice is recapitulated in aged, chow-fed mice and correlates with alterations in hepatic, but not intestinal, fatty acid amide metabolism. L-Fabp(-/-) mice exhibited short-term changes in feeding behavior with decreased food intake, which was associated with reduced abundance of key signaling fatty acid ethanolamides, including oleoylethanolamide (OEA, an agonist of PPARα) and anandamide (AEA, an agonist of cannabinoid receptors), in the liver. These reductions were associated with increased expression and activity of hepatic fatty acid amide hydrolase-1, the enzyme that degrades both OEA and AEA. Moreover, L-Fabp(-/-) mice demonstrated attenuated responses to OEA administration, which was completely reversed with an enhanced response after administration of a nonhydrolyzable OEA analog. These findings demonstrate a role for L-Fabp in attenuating obesity and hepatic steatosis, and they suggest that hepatic fatty acid amide metabolism is altered in L-Fabp(-/-) mice.

Topics: Adiposity; Age Factors; Amidohydrolases; Animals; Arachidonic Acids; Body Weight; Chromosomes; Diet, Fat-Restricted; Endocannabinoids; Enzyme Activation; Fatty Acid-Binding Proteins; Fatty Liver; Feeding Behavior; Female; Lipid Metabolism; Liver; Mice; Mice, Inbred C57BL; Mice, Knockout; Obesity; Oleic Acids; Polyunsaturated Alkamides; PPAR gamma; Quantitative Trait Loci; Signal Transduction

Prevalence of non-alcoholic steatohepatitis (NASH) rises steadily in Western countries with the obesity epidemic. NASH is associated with activation of liver fibrogenesis and predisposes to cirrhosis and associated morbi-mortality. The cannabinoid system is increasingly emerging as a crucial mediator of acute and chronic liver injury. Recent experimental and clinical data indicate that peripheral activation of cannabinoid CB1 receptors promotes insulin resistance and liver steatogenesis, two key steps in the pathogenesis of non-alcoholic fatty liver disease. Moreover, CB1 receptors enhance progression of liver fibrogenesis. These findings provide a strong rationale for the use of CB1 antagonists in the management of NASH.

Topics: Arachidonic Acids; Cannabinoids; Endocannabinoids; Fatty Liver; Humans; Insulin Resistance; Polyunsaturated Alkamides; Receptor, Cannabinoid, CB1; Receptor, Cannabinoid, CB2; Receptors, Cannabinoid

Endogenous cannabinoids acting at CB(1) receptors stimulate appetite, and CB(1) antagonists show promise in the treatment of obesity. CB(1) (-/-) mice are resistant to diet-induced obesity even though their caloric intake is similar to that of wild-type mice, suggesting that endocannabinoids also regulate fat metabolism. Here, we investigated the possible role of endocannabinoids in the regulation of hepatic lipogenesis. Activation of CB(1) in mice increases the hepatic gene expression of the lipogenic transcription factor SREBP-1c and its targets acetyl-CoA carboxylase-1 and fatty acid synthase (FAS). Treatment with a CB(1) agonist also increases de novo fatty acid synthesis in the liver or in isolated hepatocytes, which express CB(1). High-fat diet increases hepatic levels of the endocannabinoid anandamide (arachidonoyl ethanolamide), CB(1) density, and basal rates of fatty acid synthesis, and the latter is reduced by CB(1) blockade. In the hypothalamus, where FAS inhibitors elicit anorexia, SREBP-1c and FAS expression are similarly affected by CB(1) ligands. We conclude that anandamide acting at hepatic CB(1) contributes to diet-induced obesity and that the FAS pathway may be a common molecular target for central appetitive and peripheral metabolic regulation.

Topics: Animals; Arachidonic Acids; Cannabinoid Receptor Modulators; CCAAT-Enhancer-Binding Proteins; Diet; Dietary Fats; DNA-Binding Proteins; Endocannabinoids; Fatty Acids; Fatty Liver; Hypothalamus; Liver; Mice; Obesity; Polyunsaturated Alkamides; Receptor, Cannabinoid, CB1; Sterol Regulatory Element Binding Protein 1; Transcription Factors