Endocannabinoid type 1 receptor gene (CNR1) polymorphisms (rs806381, rs10485170, rs6454674, rs2023239) and cardiovascular risk factors in postmenopausal women

On the Role of Central Type-1 Cannabinoid Receptor Gene Regulation in Food Intake and Eating Behaviors

Different neuromodulatory systems are involved in long-term energy balance and body weight and, among these, evidence shows that the endocannabinoid system, in particular the activation of type-1 cannabinoid receptor, plays a key role. We here review current literature focusing on the role of the gene encoding type-1 cannabinoid receptors in the CNS and on the modulation of its expression by food intake and specific eating behaviors. We point out the importance to further investigate how environmental cues might have a role in the development of obesity as well as eating disorders through the transcriptional regulation of this gene in order to prevent or to treat these pathologies.

Role of Endocannabinoids on Sweet Taste Perception, Food Preference, and Obesity-related Disorders

The prevalence of obesity and obesity-related disorders such as type 2 diabetes (T2D) and metabolic syndrome has increased significantly in the past decades, reaching epidemic levels and therefore becoming a major health issue worldwide. Chronic overeating of highly palatable foods is one of the main responsible aspects behind overweight. Food choice is driven by food preference, which is influenced by environmental and internal factors, from availability to rewarding properties of food. Consequently, the acquisition of a dietary habit that may lead to metabolic alterations is the result of a learning process in which many variables take place. From genetics to socioeconomic status, the response to food and how this food affects energy metabolism is heavily influenced, even before birth. In this work, we review how food preference is acquired and established, particularly as regards sweet taste; towards which flavors and tastes we are positively predisposed by our genetic background, our early experience, further lifestyle, and our surroundings; and, especially, the role that the endocannabinoid system (ECS) plays in all of this. Ultimately, we try to summarize why this system is relevant for health purposes and how this is linked to important aspects of eating behavior, as its function as a modulator of energy homeostasis affects, and is affected by, physiological responses directly associated with obesity.

Uremic Pruritus Is Not Associated with Endocannabinoid Receptor 1 Gene Polymorphisms

Uremic pruritus (UP) is a frequent and bothersome symptom in hemodialysis patients. Its etiology is not fully understood and that is why there is no specific treatment. The endocannabinoid system plays a role in many pathological conditions. There is reliable evidence on the association between cannabinoid system and pruritus. In our study, we aimed to evaluate whether genetic variations in the endocannabinoid receptor 1 (CNR1) gene can affect UP. The rs12720071, rs806368, rs1049353, rs806381, rs10485170, rs6454674, and rs2023239 polymorphisms of the CNR1 gene were genotyped in 159 hemodialysis patients and 150 healthy controls using two multiplex polymerase chain reactions and the minisequencing technique. No statistically significant relationship was found in any of the evaluated genotypes between patients with and without UP, even after excluding patients with diabetes and dyslipidemia. There were no differences between patients with UP and the control group. However, in the group of all HD patients, a significantly higher incidence of GA genotype and lower incidence in GG genotype in the polymorphism rs806381s were revealed versus the control group (p = 0.04). It seems that polymorphisms of the CNR1 gene are not associated with uremic pruritus.

Selected CNR1 polymorphisms and hyperandrogenemia as well as fat mass and fat distribution in women with polycystic ovary syndrome

The endocannabinoid system is postulated to play an important role in the etiology of obesity, insulin resistance, fat distribution and metabolic disorders. Insulin resistance associated with abdominal obesity plays a leading role in the etiology of hyperandrogenism and other clinical features of the polycystic ovary syndrome (PCOS). A total of 174 women 16-38 years old, diagnosed with PCOS according to the Rotterdam criteria are recruited. Control group consisted of 125 healthy women 18-45 years old. Medical history, physical examination, anthropometric parameters and metabolic parameters were carried out. Six CNR1 gene polymorphisms were diagnosed. We observed a significantly three times higher risk of GG genotype in the polymorphism rs12720071 in women with PCOS versus the control group (p = 0.0344, OR = 3.01). A similar, significant 8-fold higher risk (p = 0.0176, OR = 8.81) was demonstrated for genotype CC polymorphism rs806368 associated with PCOS. We observed a 3.6-fold increased risk of hyperandrogenemia (free androgen index - FAI > 7) in patients with GG genotype in the rs12720071 polymorphism and AA genotype in the polymorphism rs1049353 (OR = 2.7). Our study may indicate a role of the endocannabinoid system in the occurrence of a specific hyperandrogenemia phenotype of PCOS.

Cannabinoid receptor 1 gene polymorphisms and nonalcoholic Fatty liver disease in women with polycystic ovary syndrome and in healthy controls

Context. Polycystic ovary syndrome (PCOS) is frequently associated with nonalcoholic fatty liver disease (NAFLD). The endocannabinoid system may play a crucial role in the pathogenesis of NAFLD. Polymorphism of the cannabinoid receptor 1 gene (CNR1) may be responsible for individual susceptibility to obesity and related conditions. Objective. To determine the role of genetic variants of CNR1 in the etiopathology of NAFLD in women with PCOS. Design and Setting. Our department (a tertiary referral center) conducted a cross-sectional, case-controlled study. Subjects. 173 women with PCOS (aged 20-35) and 125 healthy, age- and weight-matched controls were studied. Methods. Hepatic steatosis was assessed by ultrasound evaluation. Single nucleotide polymorphisms of CNR1 (rs806368, rs12720071, rs1049353, rs806381, rs10485170, rs6454674) were genotyped. Results. Frequency of the G allele of rs806381 (P < 0.025) and the GG genotype of rs10485170 (P < 0.03) was significantly higher in women with PCOS and NAFLD than in PCOS women without NAFLD. Frequency of the TT genotype of rs6454674 was higher in PCOS women with NAFLD (not significantly, P = 0.059). In multivariate stepwise regression, allele G of rs806381 was associated with PCOS + NAFLD phenotype. Conclusion. Our preliminary results suggest the potential role of CNR1 polymorphisms in the etiology of NAFLD, especially in PCOS women.

CNR1 gene and risk of the metabolic syndrome in patients with schizophrenia

Metabolic disturbances are more prevalent in patients with schizophrenia (SCZ) than in the general population. The endocannabinoid system plays an important role in the regulation of dopamine transmission and several metabolic pathways, and the endocannabinoid receptor type 1 gene (CNR1) is considered a candidate gene for both SCZ and metabolic disorders. We examined whether genetic variation in CNR1 was associated with metabolic syndrome (MetS) in a naturalistic cohort of 407 patients with SCZ. The minor alleles of rs6928499, rs1535255, and rs2023239 were nominally associated with a lower risk of MetS [odds ratio (OR), 0.56; 95% confidence interval (CI), 0.37-0.84; P = 0.006; OR, 0.56; 95% CI, 0.37-0.84; P = 0.006; and OR, 0.44; 95% CI, 0.27-0.72; P = 0.001, respectively, adjusted for age, sex, duration of illness, clozapine or olanzapine treatment). These differences were mainly due to differences in high-density lipoprotein cholesterol and fasting glucose but not in body mass index or waist circumference. No significant association of the other polymorphisms (rs806377, rs1049353, rs6454674, and rs806379) with MetS was found. These results provide evidence that the prevalence of MetS is associated with the CNR1 gene in patients with SCZ during long-term treatment with antipsychotic treatment. Further studies are needed to uncover the exact molecular basis for this association, which could provide novel treatment targets for the MetS.

Associations of variants of CNR1 with obesity and obesity-related traits in Chinese women

The aim of this study was to investigate associations of two candidate gene SNPs of the endocannabinoid receptor type 1 gene (CNR1) with overweight, obesity and obesity-related traits in Chinese retired women. The study subjects were a subsample of the Taizhou Retiree Women Cohort, consisting of 2812 retired women aged 50-64 years recruited from Taizhou, Jiangsu, China. Neither rs2023239 nor rs806381 polymorphism was significantly associated with body mass index-defined overweight and obesity or waist-to-hip-ratio-defined obesity. For obesity-related traits, rs2023239 was significantly associated with glutamate pyruvate transaminase (GPT) (median, 18.00 vs 17.00 for TT and TC genotypes, respectively, P=0.043). The rs806381 also showed significant association with triglyceride (TG) (mean±SD, 1.46±0.20 vs 1.53±0.20 for GA and GG+AA genotypes, respectively, P=0.013) under the dominant genetic model. In conclusion, the rs2023239 and rs806381 polymorphisms of CNR1 were not associated with increased overweight and obesity risk. But the rs2023239 polymorphism was significantly associated with GPT, and the rs806381 polymorphism was significantly associated with TG.