Endocannabinoid system and proopiomelanocortin gene expression in peripartal bovine liver in response to prepartal plane of nutrition

Summary: Endocannabinoids are fatty acid amides (FAE; oleoylethanolamide and anandamide) which have orexigenic, anorexigenic or anti-inflammatory properties. We examined mRNA expression via qPCR of endocannabinoid receptors (CNR1 and CNR2), enzymes that synthesize FAE (HRASLS5 and N-acyl phosphatidylethanolamine phospholipase D), enzymes that degrade FAE [fatty acid amide hydrolase (FAAH), N-acylethanolamine acid amidase (NAAA) and monoglyceride lipase (MGLL)], and the hormone precursor proopiomelanocortin (POMC) in liver at -14, 7, 14 and 30days around parturition from cows fed with a control (CON; NE_L=1.34Mcal/kg) or moderate-energy (OVER; NE_L=1.62Mcal/kg) diet during the dry period. Expression of CNR2 and POMC was greater at 7days in cows fed with OVER because of a decrease in expression between -14 and 7 days in cows fed with CON. Cows fed with CON had an increase in expression of FAAH, HRASLS5, NAA, MGLL and POMC between 7 and 14days; for FAAH and HRASLS5, such response led to greater expression at 14days vs. cows fed with OVER. Cows fed with OVER vs. CON had a approximately twofold increase in expression of MGLL between -14 and 7days followed by a gradual decrease through 30days at which point expression was still greater in OVER vs. CON. FAAH, MGLL and HRASLS5 were the most abundant genes measured. Expression of the hepatic endocannabinoid system and POMC was altered by plane of dietary energy prepartum particularly during the first 2-week postpartum. Such responses may play a role in the physiological adaptations to the onset of lactation, including energy balance and feed intake.