Transcriptional abundance of type-1 endocannabinoid receptor (CB1) and fatty acid amide hydrolase (FAAH) in bull spermatozoa: Relationship with field fertility

A highly sophisticated endogenous cannabinoid system (ECS) has been shown to play a crucial role in controlling sperm functions and fertility in men. In the present study, we report the differences in the expression level of components of ECS [type-1 endocannabinoid receptor (CB1) and fatty acid amide hydrolase (FAAH)] in spermatozoa from bulls with different field fertility ratings. Cryopreserved spermatozoa from crossbred cattle bulls (n = 40) were utilized for the study. The bulls were classified into high-, medium- and low-fertile bulls based on field conception rates. Sperm viability, capacitation status and protamine deficiency were assessed. Spermatozoa RNA was isolated from all the bulls, cDNA was synthesized and quantitative real time PCR was carried out to study the transcriptional abundance of CB1 and FAAH genes. Sperm viability was lower and capacitation was higher (p < 0.05) in low fertile bulls compared to medium and high fertile bulls. The expression level of CB1 gene was significantly (p < 0.05) lower in spermatozoa from low and medium fertile bulls compared to high fertile bulls. The expression of CB1 gene was 21.07 and 4.23 times greater in high and medium fertile bulls, respectively compared to low fertile bulls. The correlation between CB1 gene expression and field conception rate of bulls was positive and significant (r = 0.57; p < 0.001). Unlike CB1 receptors, FAAH gene expression was similar among high, medium and low fertile bulls. The correlation of FAAH expression with bull conception rate was positive but not significant. It was concluded that the transcriptional abundance of type-1 endocannabinoid receptor (CB1) was positively and significantly related to bull fertility.