Endocannabinoid and lipid metabolism genes network analysis in adipose and liver tissue of dairy cows during the transition period
During the transition period dairy cows are exposed to enormous metabolic changes. These changes could affect the overall health and production. Two experiments were conducted on transition cows to evaluate the 1) effects of body condition score (BCS) on the endocannabinoid system and lipid metabolism gene expression in adipose tissue; and 2) effects of rumen-protected methionine on the endocannabinoid system in liver tissue. In the first study, cows were retrospectively classified according to their BCS at -3 wk from parturition into two groups: HiBCS (BCS ≥ 3.75) or LoBCS (BCS ≤ 3.25 ). Adipose tissue at -10, 7, and 20 d around parturition was used to examine mRNA expression via qPCR of endocannabinoid receptors (CNR1, CNR2), enzymes that synthesize endocannabinoid (NAPEPLD), enzymes that degrade endocannabinoids (FAAH, NAAA, MGLL), and the hormone precursor proopiomelanocortin (POMC). We also examined mRNA expression via qPCR of genes associated with lipolysis (LIPE, ABDH5, ATGL), fatty acid oxidation (CPT1A, CPT2, ACADVL, ACOX1), oxidative stress (SOD1, SOD2), and genes that are involved in inflammation (TLR9, TLR4, NFE2L2). Expression of CNR2 and NAPEPLD was greater at 7 d in LoBCS due to lower expression at the same time in HiBCS. The expression of FAAH was upregulated at d 7 and 20 in LoBCS than HiBCS cows. Expression of MGLL was overall greater across time in LoBCS than HiBCS, LoBCS had a tendency for greater overall expression of POMC across time. Regarding the genes associated with lipolysis, LoBCS compared with HiBCS cows had overall greater expression of ABDH5, LIPE and ATGL, indicating a greater state of basal lipolysis over time. Among genes related with fatty acid oxidation the expression of CPT1A and ACADVL was greater in HiBCS than LoBCS due to greater expression at -10 and 7 d. For the mitochondrial enzyme SOD2, important for clearing reactive-oxygen species that cause cellular stress and inflammation, we observed an interaction of BCS × day due to higher expression at d 7 in LoBCS than HiBCS. There was an overall BCS effect on the expression of SOD1 due to greater expression in LoBCS compared with HiBCS. In the second experiment, cows were fed experimental diets consisting of a basal control diet (CON) or rumen-protected methionine-supplemented (MET) during the transition period (-21 through 30 days in milk). The liver was biopsied at -10, 7, 20 and 30 days relative to parturition. Gene expression was determined through qPCR for endocannabinoid receptors (CNR1, CNR2), enzymes that synthesize endocannabinoid (NAPEPLD), enzymes that degrade endocannabinoid (FAAH, NAAA, MGLL), and the hormone precursor proopiomelanocortin (POMC). A significant interaction of treatment × day was observed for the endocannabinoid receptor CNR2 associated with lower expression in MET compared with control cows on d -10. There was an overall greater expression of FAAH, MGLL, NAAA and the EC-synthesizing enzyme NAPEPLD in MET compared with control cows. Cows supplemented with MET had greater in vitro blood neutrophil phagocytosis, neutrophil oxidative burst and monocyte oxidative burst. Results from experiment 1 indicate that expression of the endocannabinoid system and lipid metabolism genes in adipose tissue may be associated with BCS. A potential linkage between those pathways and risk of disorders postpartum remains to be determined. Results from experiment 2 suggest that the alterations in the hepatic EC signaling network in response to MET might be involved in the positive effect on performance and liver function.
Endocannabinoid, Transition period, Lipid metabolism, Body condition score
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign