98 Differential gene expression of the endocannabinoid system in bovine tissues

Abstract

Abstract Because of the association with intake and metabolism, there is interest in the endocannabinoid system and how it may be manipulated to benefit livestock. With the recent interest in using industrial hemp as a feedstuff in ruminants, understanding the interaction between phytocannabinoids and the endocannabinoid system is necessary. However, the endocannabinoid system has not been specifically characterized in cattle, especially the gastrointestinal tract (GIT). The objective of this study was to characterize the distribution and transcriptional abundance of genes associated with the endocannabinoid system in cattle. Tissues including brain, spleen, thyroid, lung, liver, kidney, mesenteric vein, tongue, sublingual mucosa, rumen, omasum, duodenum, jejunum, ileum and colon were collected from 10-mo old Holstein steers (n = 6). Total RNA was extracted, and gene expression was measured using absolute quantification real time qPCR. Gene expression of endocannabinoid receptors CNR1 and CNR2, synthesis enzymes DAGLA, DAGLB and NAPEPLD, degradation enzymes MGLL and FAAH, and transient receptor potential vanilloids TRPV3 and TRPV6 was measured. Data were analyzed in R using a Kruskal-Wallis followed by a Wilcoxon rank-sum test. Results are reported as the median copy number/20 ng of equivalent cDNA (CN) with interquartile range (IQR). The greatest expression of CNR1 and CNR2 was in the brain and spleen, respectively. Expression of either receptor was not detected in any GIT tissues; however, there was a tendency (P = 0.095) for CNR2 to be expressed above background in rumen. Expression of endocannabinoid synthesis and degradation enzymes varied greatly across tissues. Brain tissue had the greatest expression at 641 CN (IQR 52; P ≤ 0.05) of DAGLA; however, expression in liver and most of the GIT tissues was below the limit of detection. DAGLB was detected in all tissues, with brain and spleen having the greatest expression (P ≤ 0.05). Expression of NAPEPLD in the GIT was least in tongue and sublingual mucosal. There was no difference in expression between hindgut tissues; however, these tissues collectively had 592% greater expression than rumen and omasum (P ≤ 0.05). While MGLL was found to be expressed in all tissues, expression of FAAH was only above the limit of detection in brain, liver, kidney, jejunum and ileum. TRPV3 was expressed above background in tongue, rumen, omasum and colon, with rumen having the greatest expression (198 CN, IQR 13.3; P = 0.02). Although not difference from each other, thyroid and duodenum had the greatest expression of TRPV6, with 285 (IQR 164) and 563 (IQR 467) CN compared with all other tissues (P < 0.05). These data demonstrate the complex distribution of the endocannabinoid system in cattle. Expression levels suggest that regulatory functions of this system are tissue dependent, providing initial insight into potential target tissues for manipulation of the endocannabinoid system.