Genetic polymorphisms of the endocannabinoid system in obesity and diabetes

The endocannabinoid system (ECS) is involved in many physiological processes including fertility, pain and energy regulation. The aim of this systematic review was to examine the contribution of single nucleotide polymorphisms (SNPs) of the ECS to adiposity and glucose metabolism. Database searches identified 734 articles, of which 65 were included; these covered 70 SNPs in genes coding for cannabinoid receptors 1 and 2 (CB₁, CB₂), fatty acid amide hydrolase (FAAH) and N-acyl phosphatidylethanolamine phospholipase D (NAPE-PLD). No studies included SNPs relating to monoacylglycerol lipase or diacylglycerol lipase. The CB₁ receptor SNP rs1049353 showed 17 associations with lower body mass index (BMI) and fat mass (five studies). It also showed three associations with lower insulin levels (one study). Conversely, the CB₁ receptor SNP rs806368 was associated with increased BMI and waist circumference (two studies). The FAAH SNP rs324420 was associated with increased obesity (three studies). A haplotype of NAPE-PLD was associated with decreased BMI (one study). A total of 60 SNPs showed no association with any measured outcome. This review suggests a complex but important role of ECS SNPs in energy and glucose metabolism.     

What Role Does the Endocannabinoid System Play in the Pathogenesis of Obesity?

The endocannabinoid system (ECS) is an endogenous signaling system formed by specific receptors (cannabinoid type 1 and type 2 (CB₁ and CB₂)), their endogenous ligands (endocannabinoids), and enzymes involved in their synthesis and degradation. The ECS, centrally and peripherally, is involved in various physiological processes, including regulation of energy balance, promotion of metabolic process, food intake, weight gain, promotion of fat accumulation in adipocytes, and regulation of body homeostasis; thus, its overactivity may be related to obesity. In this review, we try to explain the role of the ECS and the impact of genetic factors on endocannabinoid system modulation in the pathogenesis of obesity, which is a global and civilizational problem affecting the entire world population regardless of age. We also emphasize that the search for potential new targets for health assessment, treatment, and the development of possible therapies in obesity is of great importance.     

IP(3)R-mediated Ca(2+) release is modulated by anandamide in isolated cardiac nuclei

Cannabinoids (CBs) are known to alter coronary vascular tone and cardiac performance. They also exhibit cardioprotective properties, particularly in their ability to limit the damage produced by ischaemia reperfusion injury. The mechanisms underlying these effects are unknown. Here we investigate the intracellular localisation of CB receptors in the heart and examine whether they may modulate localised nuclear Ca²⁺ release. In isolated cardiac nuclear preparations, expression of both the inositol 1,4,5-trisphosphate receptor type 2 (IP₃R) and CB receptors (CB₁R and CB₂R) was demonstrated by immunoblotting. Both receptors localised to the nucleus and purity of the nuclear preparations was confirmed by co-expression of the nuclear marker protein nucleolin but absence of cytoplasmic actin. To measure effects of IP₃R and CBR agonists on nuclear Ca²⁺ release, isolated nuclei were loaded with Fluo5N-AM. This dye accumulates in the nuclear envelope. Isolated nuclei responded to IP₃ with rapid and transient Ca²⁺ release from the nuclear envelope. Anandamide inhibited this IP₃-mediated release. Preincubation of nuclear preparations with either the CB₁R antagonist (AM251) or the CB₂R antagonist (AM630) reversed anandamide-mediated inhibition to 80% and 60% of control values respectively. When nuclei were pre-treated with both CBR antagonists, anandamide-mediated inhibition of IP₃-induced Ca²⁺ release was completely reversed. These results are the first to demonstrate the existence of cardiac nuclear CB receptors. They are also the first to show that anandamide can negatively modulate IP₃-mediated nuclear Ca²⁺ release. As such, this provides evidence for a novel key mechanism underlying the action of CBs and CBRs in the heart.     

Anti‐Inflammatory and Osteoprotective Effects of Cannabinoid‐2 Receptor Agonist HU‐308 in a Rat Model of Lipopolysaccharide‐Induced Periodontitis

Background: Anti‐inflammatory and immunologic properties of cannabinoids have been reported in several tissues. Expression of cannabinoid receptor Type 2 was reported in osteoblasts and osteoclasts, suggesting a key role in bone metabolism. The aim of this study is to assess the effect of treatment with cannabinoid‐2 receptor agonist HU‐308 in the oral health of rats subjected to lipopolysaccharide (LPS)‐induced periodontitis. Methods: Twenty‐four rats were distributed in four groups (six rats per group): 1) control rats; 2) sham rats; 3) rats submitted to experimental periodontitis (LPS); and 4) rats submitted to experimental periodontitis and treated with HU‐308 (LPS+HU). In groups LPS and LPS+HU, periodontitis was induced by LPS (1 mg/mL) injected into the gingival tissue (GT) of maxillary and mandibular first molars and into the interdental space between the first and second molars, 3 days per week for 6 weeks. In group LPS+HU, HU‐308 (500 ng/mL) was applied topically to the GT daily. Results: Alveolar bone loss resulting from LPS‐induced periodontitis was significantly attenuated with HU‐308 treatment (LPS+HU), measured by macroscopic and histologic examination. Treatment also reduced gingival production of inflammatory mediators augmented in LPS‐injected rats, such as: 1) inducible nitric oxide (iNOS) activity (LPS: 90.18 ± 36.51 pmol/minute/mg protein versus LPS+HU: 16.37 ± 4.73 pmol/minute/mg protein; P <0.05); 2) tumor necrosis factor alpha (LPS: 185.70 ± 25.63 pg/mg protein versus LPS+HU: 95.89 ± 17.47 pg/mg protein; P <0.05); and 3) prostaglandin E₂ (PGE₂) (LPS: 159.20 ± 38.70 pg/mg wet weight versus LPS+HU: 71.25 ± 17.75 pg/mg wet weight; P <0.05). Additionally, HU‐308 treatment prevented the inhibitory effect of LPS‐induced periodontitis on the salivary secretory response to pilocarpine. Moreover, iNOS activity and PGE₂ content, which were increased by LPS‐induced periodontitis in the submandibular gland, returned to control values after HU‐308 treatment. Conclusion: This study demonstrates anti‐inflammatory, osteoprotective, and prohomeostatic effects of HU‐308 in oral tissues of rats with LPS‐induced periodontitis.     

The rat pineal gland comprises an endocannabinoid system

In the mammalian pineal gland, the rhythm in melatonin biosynthesis depends on the norepinephrine (NE)-driven regulation of arylalkylamine N-acetyltransferase (AANAT), the penultimate enzyme of melatonin biosynthesis. A recent study showed that phytocannabinoids like tetrahydrocannabinol reduce AANAT activity and attenuate NE-induced melatonin biosynthesis in rat pineal glands, raising the possibility that an endocannabinoid system is present in the pineal gland. To test this hypothesis, we analyzed cannabinoid (CB) receptors and specific enzymes for endocannabinoid biosynthesis or catabolism in rat pineal glands and cultured pinealocytes. Immunohistochemical and immunoblot analyses revealed the presence of CB1 and CB2 receptor proteins, of N-acyl phosphatidyl ethanolamine hydrolyzing phospholipase D (NAPE-PLD), an enzyme catalyzing endocannabinoid biosynthesis and of fatty acid amide hydrolase (FAAH), an endocannabinoid catabolizing enzyme, in pinealocytes, and in pineal sympathetic nerve fibers identified by double immunofluorescence with an antibody against tyrosine hydroxylase. The immunosignals for the CB2 receptor, NAPE-PLD, and FAAH found in pinealocytes did not vary under a 12 hr light:12 hr dark cycle. The CB1 receptor immunoreaction in pinealocytes was significantly reduced at the end of the light phase [zeitgeber time (ZT) 12]. The immunosignal for NAPE-PLD found in pineal sympathetic nerve fibers was reduced in the middle of the dark phase (ZT 18). Stimulation of cultured pinealocytes with NE affected neither the subcellular distribution nor the intensity of the immunosignals for the investigated CB receptors and enzymes. In summary, the pineal gland comprises indispensable compounds of the endocannabinoid system indicating that endocannabinoids may be involved in the control of pineal physiology.     

Cannabinoid Type 1 Receptor: Another Arrow in the Adipocytes' Bow

The endocannabinoid system has recently emerged as an important modulator of several functions of adipose tissue, including cell proliferation, differentiation and secretion. Here, we will review the effects of cannabinoid type 1 (CB₁) receptor activation/blockade in adipocytes by summarising the data in the literature since the discovery of the presence of this receptor in adipose tissue. We will also discuss our original data obtained in mouse 3T3-L1 adipocyte cells using WIN55 212, a CB₁/CB₂ receptor agonist and SR141716 (rimonabant), a specific CB₁ receptor antagonist, respectively, in different experimental settings.     

大麻素受体1在帕金森病大鼠基底节表达的研究

目的：观察6-OHDA单侧毁损帕金森病（PD）大鼠模型基底节内大麻素受体1（CBR1表达特点，探讨其与PD的关系。方法：6-OHDA两点法立体定向单侧前脑内侧束（MFB）注射建立PD大鼠模型，采用免疫组化（IHC）和Western blot方法检测基底节内CBR1的表达水平。结果：IHC显示CBR1在大鼠基底节内广泛表达，PD组患侧纹状体（CPU）和苍白球（GP）CBR1较对照组显著增多（均P〈0、01）；但PD组患侧黑质网状部（SNr）CBR1较对照组明显减少（P〈0.01）。Western blot结果同IHC一致：PD组患侧CPU内CBR1较对照组显著增多（P〈0、01）。结论：PD时基底节内CBR1系统信号传导改变可能对PD的病理生理发展有重要调控作用。     

Increased motivation for beer in rats following administration of a cannabinoid CB1 receptor agonist

A series of experiments examined the effects of the cannabinoid CB₁ receptor agonist CP 55,940 ((−)-cis-3-[2-hydroxy-4-(1,1-dimethylheptyl)phenyl]-trans-4-(3-hydroxypropyl)cyclohexanol) on the motivation to consume beer, near-beer (a beer-like beverage containing <0.5% ethanol) and sucrose solutions in rats. The experiments employed a ‘lick-based progressive ratio paradigm' in which an ever increasing number of licks had to be emitted at a tube for each successive fixed unit of beverage delivered. Break point, the lick requirement at which responding ceased, was used as an index of motivation. In the first experiment, CP 55,940 (10, 30 or 50 μg/kg) caused a dose-dependent increase in break points for beer (containing 4.5% ethanol v/v) and for near-beer. The highest (50 μg/kg) dose of CP 55,940 also significantly decreased locomotor activity. In the second experiment, CP 55,940 (10 or 30 μg/kg) dose-dependently increased break points in rats licking for ‘light' beer (containing 2.7% ethanol v/v) or for a sucrose solution (8.6% w/v) containing the same number of calories as the beer. In the third experiment, the facilitatory effects of CP 55,940 (30 μg/kg) on responding for beer and near-beer were reversed by both the cannabinoid CB₁ receptor antagonist SR 141716 (N-(piperidin-1-yl)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide hydrochloride) (1.5 mg/kg) and the opioid receptor antagonist naloxone (2.5 mg/kg). Naloxone had a proportionally greater effect on rats licking for beer compared to near-beer, consistent with previous reports of opioid receptor mediation of alcohol craving. These results show that cannabinoids modulate the motivation for beer via both cannabinoid CB₁ receptors and opioid receptors. The similar effect of CP 55,940 on the motivation for beer, near-beer and sucrose suggests that the drug effect may reflect a general stimulatory effect on appetite for palatable beverages, although a more specific effect on the desire for alcohol cannot be ruled out.