Isabel Matias

Cloning of the first sn1-DAG lipases points to the spatial and temporal regulation of endocannabinoid signaling in the brain

Diacylglycerol (DAG) lipase activity is required for axonal growth during development and for retrograde synaptic signaling at mature synapses. This enzyme synthesizes the endocannabinoid 2-arachidonoyl-glycerol (2-AG), and the CB1 cannabinoid receptor is also required for the above responses. We now report on the cloning and enzymatic characterization of the first specific sn-1 DAG lipases. Two closely related genes have been identified and their expression in cells correlated with 2-AG biosynthesis and release. The expression of both enzymes changes from axonal tracts in the embryo to dendritic fields in the adult, and this correlates with the developmental change in requirement for 2-AG synthesis from the pre- to the postsynaptic compartment. This switch provides a possible explanation for a fundamental change in endocannabinoid function during brain development. Identification of these enzymes may offer new therapeutic opportunities for a wide range of disorders.

Endocannabinoid control of food intake and energy balance

Marijuana and its major psychotropic component, Δ9-tetrahydrocannabinol, stimulate appetite and increase body weight in wasting syndromes, suggesting that the CB1 cannabinoid receptor and its endogenous ligands, the endocannabinoids, are involved in controlling energy balance. The endocannabinoid system controls food intake via both central and peripheral mechanisms, and it may also stimulate lipogenesis and fat accumulation. Here we discuss the multifaceted regulation of energy homeostasis by endocannabinoids, together with its applications to the treatment of eating disorders and metabolic syndromes.

Endocannabinoids and the control of energy balance.

Two receptors have been cloned to date for the psychotropic compound Delta(9)-tetrahydrocannabinol, and termed cannabinoid CB(1) and CB(2) receptors. Their endogenous ligands, the endocannabinoids, have also been identified. CB(1) receptors and endocannabinoids are present in brain structures controlling energy intake and in peripheral cells (hepatocytes, adipocytes, pancreatic islet cells) regulating energy homeostasis. CB(2) receptors are more abundant in lymphocytes and macrophages, and participate in immune and inflammatory reactions. Metabolic hormones and peptides regulate the levels of the endocannabinoids and, hence, the activity of cannabinoid receptors in several tissues in a seemingly coordinated way. The endocannabinoids, particularly after stress and brief food deprivation, act in turn as local modulators of the expression and action of neurotransmitters, hormones and adipokines involved in metabolic control. Endocannabinoid overactivity seems to accompany metabolic and eating disorders and to contribute to the development of abdominal obesity, dyslipidemia and hyperglycemia. Accordingly, clinical trials have shown that CB(1) receptor antagonists are efficacious at reducing not only food intake, but also abdominal adiposity and its metabolic sequelae.

Antitumor Activity of Plant Cannabinoids with Emphasis on the Effect of Cannabidiol on Human Breast Carcinoma

Δ9-Tetrahydrocannabinol (THC) exhibits antitumor effects on various cancer cell types, but its use in chemotherapy is limited by its psychotropic activity. We investigated the antitumor activities of other plant cannabinoids, i.e., cannabidiol, cannabigerol, cannabichromene, cannabidiol acid and THC acid, and assessed whether there is any advantage in using Cannabis extracts (enriched in either cannabidiol or THC) over pure cannabinoids. Results obtained in a panel of tumor cell lines clearly indicate that, of the five natural compounds tested, cannabidiol is the most potent inhibitor of cancer cell growth (IC50 between 6.0 and 10.6 μM), with significantly lower potency in noncancer cells. The cannabidiol-rich extract was equipotent to cannabidiol, whereas cannabigerol and cannabichromene followed in the rank of potency. Both cannabidiol and the cannabidiol-rich extract inhibited the growth of xenograft tumors obtained by s.c. injection into athymic mice of human MDA-MB-231 breast carcinoma or rat v-K-ras-transformed thyroid epithelial cells and reduced lung metastases deriving from intrapaw injection of MDA-MB-231 cells. Judging from several experiments on its possible cellular and molecular mechanisms of action, we propose that cannabidiol lacks a unique mode of action in the cell lines investigated. At least for MDA-MB-231 cells, however, our experiments indicate that cannabidiol effect is due to its capability of inducing apoptosis via: direct or indirect activation of cannabinoid CB2 and vanilloid transient receptor potential vanilloid type-1 receptors and cannabinoid/vanilloid receptor-independent elevation of intracellular Ca2+ and reactive oxygen species. Our data support the further testing of cannabidiol and cannabidiol-rich extracts for the potential treatment of cancer.

Circulating endocannabinoid levels, abdominal adiposity and related cardiometabolic risk factors in obese men

Objective:The link between excess intra-abdominal adiposity (IAA) and metabolic complications leading to type 2 diabetes and cardiovascular disease is well recognized. Blockade of endocannabinoid action at cannabinoid CB1 receptors was shown to reduce these complications. Here, we investigated the relationship between IAA, circulating endocannabinoid levels and markers of cardiometabolic risk in male obese subjects.Design, subjects and measurements:Fasting plasma levels of the endocannabinoids, anandamide (AEA) and 2-arachidonoylglycerol (2-AG), were measured by liquid chromatography-mass spectrometry in a study sample of 62 untreated asymptomatic men with body mass index (BMI) from 18.7 to 35.2 kg/m2.Results:Plasma 2-AG, but not AEA, levels correlated positively with BMI, waist girth, IAA measured by computed tomography, and fasting plasma triglyceride and insulin levels, and negatively with high-density lipoprotein cholesterol and adiponectin levels. Obese men with similar BMI values (⩾30 kg/m2) but who markedly differed in their amount of IAA (< vs⩾130 cm2, n=17) exhibited higher 2-AG levels in the presence of high IAA. No difference in 2-AG concentrations was observed between obese men with low levels of IAA vs nonobese controls.Conclusions:These results provide evidence for a relationship in men between a key endocannabinoid, 2-AG, and cardiometabolic risk factors, including IAA.

Possible endocannabinoid control of colorectal cancer growth

BACKGROUND & AIMS The endocannabinoids anandamide and 2-arachidonoylglycerol (2-AG) inhibit cancer cell proliferation by acting at cannabinoid receptors (CBRs). We studied (1). the levels of endocannabinoids, cannabinoid CB(1) and CB(2) receptors, and fatty acid amide hydrolase (FAAH, which catalyzes endocannabinoid hydrolysis) in colorectal carcinomas (CRC), adenomatous polyps, and neighboring healthy mucosa; and (2). the effects of endocannabinoids, and of inhibitors of their inactivation, on human CRC cell proliferation. METHODS Tissues were obtained from 21 patients by biopsy during colonoscopy. Endocannabinoids were measured by liquid chromatography-mass spectrometry (LC-MS). CB(1), CB(2), and FAAH expression were analyzed by RT-PCR and Western immunoblotting. CRC cell lines (CaCo-2 and DLD-1) were used to test antiproliferative effects. RESULTS All tissues and cells analyzed contain anandamide, 2-AG, CBRs, and FAAH. The levels of the endocannabinoids are 3- and 2-fold higher in adenomas and CRCs than normal mucosa. Anandamide, 2-AG, and the CBR agonist HU-210 potently inhibit CaCo-2 cell proliferation. This effect is blocked by the CB(1) antagonist SR141716A, but not by the CB(2) antagonist SR144528, and is mimicked by CB(1)-selective, but not CB(2)-selective, agonists. In DLD-1 cells, both CB(1) and CB(2) receptors mediate inhibition of proliferation. Inhibitors of endocannabinoid inactivation enhance CaCo-2 cell endocannabinoid levels and block cell proliferation, this effect being antagonized by SR141716A. CaCo-2 cell differentiation into noninvasive cells results in increased FAAH expression, lower endocannabinoid levels, and no responsiveness to cannabinoids. CONCLUSIONS Endocannabinoid levels are enhanced in transformed colon mucosa cells possibly to counteract proliferation via CBRs. Inhibitors of endocannabinoid inactivation may prove useful anticancer agents.

Mitochondrial CB1 receptors regulate neuronal energy metabolism

The mammalian brain is one of the organs with the highest energy demands, and mitochondria are key determinants of its functions. Here we show that the type-1 cannabinoid receptor (CB1) is present at the membranes of mouse neuronal mitochondria (mtCB1), where it directly controls cellular respiration and energy production. Through activation of mtCB1 receptors, exogenous cannabinoids and in situ endocannabinoids decreased cyclic AMP concentration, protein kinase A activity, complex I enzymatic activity and respiration in neuronal mitochondria. In addition, intracellular CB1 receptors and mitochondrial mechanisms contributed to endocannabinoid-dependent depolarization-induced suppression of inhibition in the hippocampus. Thus, mtCB1 receptors directly modulate neuronal energy metabolism, revealing a new mechanism of action of G protein–coupled receptor signaling in the brain.

Endocannabinoid Dysregulation in the Pancreas and Adipose Tissue of Mice Fed With a High‐fat Diet

Objective: In mice, endocannabinoids (ECs) modulate insulin release from pancreatic β‐cells and adipokine expression in adipocytes through cannabinoid receptors. Their pancreatic and adipose tissue levels are elevated during hyperglycemia and obesity, but the mechanisms underlying these alterations are not understood.

Dysregulation of peripheral endocannabinoid levels in hyperglycemia and obesity: Effect of high fat diets.

Increasing evidence indicates that endocannabinoid (EC) signalling is dysregulated during hyperglycemia and obesity, particularly at the level of anandamide (AEA) and/or 2-arachidonoylglycerol (2-AG) concentrations in tissues involved in the control of energy intake and processing, such as the liver, white adipose tissue and pancreas. Here we review this previous evidence and provide new data on the possible dysregulation of EC levels in organs with endocrine function (adrenal glands and thyroid), involved in energy expenditure (brown adipose tissue and skeletal muscle), or affected by the consequences of metabolic disorders (heart and kidney), obtained from mice fed for 3, 8 and 14 weeks with two different high fat diets (HFDs), with different fatty acid compositions and impact on fasting glucose levels. Statistically significant elevations (in the skeletal muscle, heart and kidney) or reductions (in the thyroid) of the levels of either AEA or 2-AG, or both, were found. Depending on the diet, these changes preceded or accompanied the development of overt obesity and/or hyperglycemia. In the adrenal gland, first a reduction and then an elevation of EC levels were observed. In the brown fat, a very early elevation of both AEA and 2-AG normalized levels was observed with one of the diets, whereas delayed decreases were explained by an increase of the amount of fat tissue weight induced by the HFDs. The potential implications of these and previous findings in the general framework of the proposed roles of the EC system in the control of metabolic, endocrine and cardiovascular and renal functions are discussed.

Pharmacological enhancement of the endocannabinoid system in the nucleus accumbens shell stimulates food intake and increases c-Fos expression in the hypothalamus

Evidence indicates that the endocannabinoid, 2‐arachidonoylglycerol (2‐AG), increases food intake when injected into the nucleus accumbens shell (NAcS), thereby potentially activating hypothalamic nuclei involved in food intake regulation. We aimed to evaluate potential orexigenic effects of the endocannabinoid anandamide and of AA5HT, a fatty acid amide hydrolase (FAAH) inhibitor, and OMDM‐1, an inhibitor of anandamide uptake, injected in the NAcS, as well as the effect of these treatments on activation of hypothalamic nuclei.