n-3 Polyunsaturated fatty acid (PUFA) deficiency elevates and n-3 PUFA enrichment reduces brain 2-arachidonoylglycerol level in mice

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.

Endogenous cannabinoids in the brain and peripheral tissues: regulation of their levels and control of food intake

Endocannabinoids were first defined in 1995 as 'endogenous substances capable of binding to and functionally activating the cannabinoid receptors'. To date, two well-established endocannabinoids, N-arachidonoylethanolamine (anandamide) and 2-arachidonoylglycerol (2-AG), as well as a few other putative ligands, all derived from long-chain polyunsaturated fatty acids, have been identified in animal tissues. The biosynthetic and metabolic pathways for anandamide and 2-AG have been elucidated, and most of the enzymes therein involved have been cloned. We now know that CB1 receptors, and endocannabinoids in tissue concentrations sufficient to activate them, are more widely distributed than originally thought, and are found in brain and peripheral organs involved in the control of energy intake and processing, including the hypothalamus, nucleus accumbens, brainstem, vagus nerve, gastrointestinal tract, adipose tissue and liver. Endocannabinoid biosynthetic and inactivating pathways are under the regulation of neuropeptides and hormones involved in energy homeostasis, and endocannabinoid levels are directly affected by the diet. Endocannabinoids, in turn, regulate the expression and action of mediators involved in nutrient intake and processing. These cross-talks are at the basis of the proposed role of endocannabinoid signalling in the control of food intake, from invertebrates to lower vertebrates and mammals, and their perturbation appears to contribute to the development of eating disorders.

Endocannabinoid system and its role in energy regulation

Endocannabinoids are endogenous agonists for the two types of cannabinoid receptors identified to date, the CB₁ and CB₂ receptors. CB₁ receptors and tissue concentrations of endocannabinoids sufficient to activate them are present in the brain structures controlling energy intake (i.e., the hypothalamus, nucleus accumbens and nodose ganglion), as well as in all peripheral organs mostly involved in the regulation of energy homeostasis (i.e., the duodenum, small and large intestine, adipose tissue, skeletal muscle, pancreas and liver). Several peripheral neuropeptides and hormones involved in energy balance, and type of diet, regulate endocannabinoid levels, whereas endocannabinoids, in turn, regulate the expression and release of hypothalamic mediators involved in nutrient intake. Dysregulation of the endocannabinoid system might contribute to the development of eating disorders and explain why CB₁ receptor blockers are efficacious at reducing not only food intake but also the metabolic consequences of visceral adiposity and obesity.

Tardive dyskinesia and essential fatty acids

Tardive dyskinesia (TD) is a movement disorder described in individuals who have been treated with anti-dopaminergic agents. The pathophysiology of this condition remains to be fully elucidated. Several mechanisms like dopaminergic supersensitivity, dysfunction of striatonigral, GABAergic neurons and disturbed balance between dopaminergic and cholinergic systems have been described. Essential fatty acids (EFAs) are important components of neuronal membrane and the EFA content of these membranes can significantly influence neuronal functioning. Lower levels of EFAs have been reported in red blood cells (RBC) and plasma of individuals with moderate to severe TD. Supplementation with EFAs (omega-3 and omega-6 and ethyl-EPA) have been tried to alleviate TD in open and double-blind clinical trials and in some animal models of TD. In addition, antioxidants (Vitamin E) and melatonin have been tried. However, smaller numbers of patients and shortened length of clinical studies make it difficult to draw any definitive conclusions. Large multi-centre studies with sound methodology of both EFAs and antioxidants are needed.

Red cell membrane omega-3 fatty acids are decreased in nondepressed patients with social anxiety disorder

The "phospholipid hypothesis" attributes a pathophysiologic role to the polyunsaturated fatty acid (PUFA) composition of phospholipids in depression. The aim of the present study was to determine whether the hypothesis is relevant to social anxiety disorder (SAD). The study sample consisted of 27 untreated, nondepressed patients with SAD (DSM-IV) and 22 controls. Severity of SAD was assessed with the Liebowitz Social Anxiety Scale (LSAS). Erythrocyte PUFA concentrations were measured by gas-liquid chromatography. Concentrations of most n-3 PUFAs were lower in the patients: 18:3n-3 by 32% (p < 0.002), 20:3n-3 by 34%, 20:5n-3 by 36% (all p < 0.001) and 22:6n-3 by 18% (p = 0.002). No significant differences were observed in other fatty acids. Significant inverse correlations were obtained between levels of n-3 PUFAs and LSAS scores. In conclusion, the phospholipid hypothesis may apply to SAD, thereby opening new therapeutic options. The robust relationship between low erythrocyte n-3 PUFA concentrations and SAD justifies exploration of relevant neuropathophysiological mechanisms.

Endocannabinoid control of food intake and energy balance

Marijuana and its major psychotropic component, Delta(9)-tetrahydrocannabinol, stimulate appetite and increase body weight in wasting syndromes, suggesting that the CB(1) 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.

Dietary fatty acids and the risk of Parkinson disease: The Rotterdam Study

BACKGROUND

Unsaturated fatty acids are important constituents of neuronal cell membranes and have neuroprotective, antioxidant, and anti-inflammatory properties.

OBJECTIVE

To determine if a high intake of unsaturated fatty acids might be associated with a lower risk of Parkinson disease (PD).

METHODS

In the Rotterdam Study, a prospective population-based cohort study of people ages > or =55, the association between intake of unsaturated fatty acids and the risk of incident PD was evaluated among 5,289 subjects who were free of dementia and parkinsonism and underwent complete dietary assessment at baseline. PD was assessed through repeated in-person examination, and the cohort was continuously monitored by computer linkage to medical records. The data were analyzed using Cox proportional hazards regression models.

RESULTS

After a mean follow-up of 6.0 years, 51 participants with incident PD were identified. Intakes of total fat, monounsaturated fatty acids (MUFAs), and polyunsaturated fatty acids (PUFAs) were significantly associated with a lower risk of PD, with an adjusted hazard ratio per SD increase of energy-adjusted intake of 0.69 (95% CI 0.52 to 0.91) for total fat, of 0.68 (95% CI 0.50 to 0.94) for MUFAs, and 0.66 (95% CI 0.46 to 0.96) for PUFAs. No associations were found for dietary saturated fat, cholesterol, or trans-fat.

CONCLUSION

These findings suggest that high intake of unsaturated fatty acids might protect against Parkinson disease.

ATP induces a rapid and pronounced increase in 2-arachidonoylglycerol production by astrocytes, a response limited by monoacylglycerol lipase

The cytoplasm of neural cells contain millimolar amounts of ATP, which flood the extracellular space after injury, activating purinergic receptors expressed by glial cells and increasing gliotransmitter production. These gliotransmitters, which are thought to orchestrate neuroinflammation, remain widely uncharacterized. Recently, we showed that microglial cells produce 2-arachidonoylglycerol (2-AG), an endocannabinoid known to prevent the propagation of harmful neuroinflammation, and that ATP increases this production by threefold at 2.5 min (Witting et al., 2004). Here we show that ATP increases 2-AG production from mouse astrocytes in culture, a response that is more rapid (i.e., significant within 10 sec) and pronounced (i.e., 60-fold increase at 2.5 min) than any stimulus-induced increase in endocannabinoid production reported thus far. Increased 2-AG production from astrocytes requires millimolar amounts of ATP, activation of purinergic P2X7 receptors, sustained rise in intracellular calcium, and diacylglycerol lipase activity. Furthermore, we show that astrocytes express monoacylglycerol lipase (MGL), the main hydrolyzing enzyme of 2-AG, the pharmacological inhibition of which potentiates the ATP-induced 2-AG production (up to 113-fold of basal 2-AG production at 2.5 min). Our results show that ATP greatly increases, and MGL limits, 2-AG production from astrocytes. We propose that 2-AG may function as a gliotransmitter, with MGL inhibitors potentiating this production and possibly restraining the propagation of harmful neuroinflammation.

Finding of endocannabinoids in human eye tissues: Implications for glaucoma

Cannabinoid CB(1) receptors are involved in ocular physiology and may regulate intraocular pressure (IOP). However, endocannabinoid levels in human ocular tissues of cornea, iris, ciliary body, retina, and choroid from normal and glaucomatous donors have not been investigated. Anandamide (N-arachidonoylethanolamine; AEA), 2-arachidonoylglycerol (2-AG), and the anandamide congener, palmitoylethanolamide (PEA), were detected in all the human tissues examined. In eyes from patients with glaucoma, significantly decreased 2-AG and PEA levels were detected in the ciliary body, an important tissue in the regulation of IOP. The findings suggest that these endogenous compounds may have a role in this disease, particularly with respect to regulation of IOP.