Gene expression of free fatty acids-sensing G protein-coupled receptors in beef cattle.

Many physiological functions are regulated by free fatty acids (FFA). Recently, the discovery of FFA-specific G protein-coupled receptors (FFARs) has added to the complexity of their actions at the cellular level. The study of FFAR in cattle is still in its earliest stages focusing mainly on dairy cows. In this study, we set out to map the expression of genes encoding FFARs in 6 tissues of beef cattle. We also investigated the potential effect of dietary forage nature on FFAR gene expression. To this end, 16 purebred Charolais bulls were fed a grass silage ration or a maize silage ration (n = 8/group) with a forage/concentrate ratio close to 60:40 for 196 d. The animals were then slaughtered at 485 ±â€…42 d and liver, spleen, ileum, rectum, perirenal adipose tissue (PRAT), and Longissimus Thoracis muscle were collected. FFAR gene expression was determined by real-time quantitative PCR. Our results showed that of the five FFARs investigated, FFAR1, FFAR2, FFAR3, and GPR84 are expressed (Ct < 30) in all six tissues, whereas FFAR4 was only expressed (Ct < 30) in PRAT, ileum, and rectum. In addition, our results showed that the nature of the forage, i.e., grass silage or maize silage, had no effect on the relative abundance of FFAR in any of the tissues studied (P value > 0.05). Taken together, these results open new perspectives for studying the physiological role of these receptors in beef cattle, particularly in nutrient partitioning during growth.

Free fatty acids (FFA) are key modulators of bovine physiology. Recently, it has been discovered that some G protein-coupled receptors, termed free fatty acid receptors (FFARs), may help mediate the action of FFA at the cellular level. In humans and rodents, a growing body of evidence has shown that i) FFARs are expressed in a wide range of tissues and ii) FFARs are involved in the regulation of major FFA-dependent physiological processes (inflammation, feed intake, insulin release, etc.). In cattle, information on FFAR expression and function in tissues are scarce and mainly concern dairy cows. In this study, we showed that FFARs are expressed in 6 different tissues of beef cattle: adipose tissue, muscle tissue, ileum, rectum, liver, and spleen. We also showed that the nature of forage fed to the animals (i.e., grass silage vs. maize silage) has no effect on FFARs gene expression.

Sunflower oil supplementation affects the expression of miR-20a-5p and miR-142-5p in the lactating bovine mammary gland.

Oil supplementation in dairy cattle diets is used to modulate milk fat composition, as well as the expression of mammary lipogenic genes, whose regulation remains unclear. MiRNAs are small non-coding RNA considered as crucial regulators of gene expression, offering clues to explain the mechanism underlying gene nutriregulation. The present study was designed to identify miRNAs whose expression in the cow mammary gland is modulated by sunflower oil supplementation. MiRNomes were obtained using RNAseq technology from the mammary gland of lactating cows receiving a low forage diet, supplemented or not with 4% sunflower oil. Among the 272 miRNAs characterized, eight were selected for RT-qPCR validations, showing the significant down-regulation of miR-142-5p and miR-20a-5p by sunflower supplementation. These two miRNAs are predicted to target genes whose expression was reported as differentially expressed by sunflower supplementation. Among their putative targets, ELOVL6 gene involved in lipid metabolism has been studied. However, a first analysis did not show its significant down-regulation, in response to the over-expression of miR-142-5p, of miR-20a-5p, or both, in a bovine mammary epithelial cell line. However, a clearer understanding of the miRNA expression by lipid supplementation would help to decipher the regulation of lactating cow mammary gland in response to nutrition.

Stress during pregnancy alters dendritic spine density and gene expression in the brain of new-born lambs.

Rodent studies show how prenatal stress (PS) can alter morphology in the cortico-limbic structures that support emotional and cognitive functions. PS-induced alteration is less well described in species with a gyrencephalic brain and complex earlier fetal development, and never in sheep at birth to rule out postnatal environment effects or influences of maternal behavior. This study aimed to assess the consequences of a mild chronic stress in pregnant ewes on the neurobiological development of their lambs at birth. During the last third of gestation, 7 ewes were exposed daily to various unpredictable and negative routine management-based challenges (stressed group), while 7 other ewes were housed without any additional perturbation (control group). For each group, a newborn from each litter was sacrificed at birth to collect its brain and analyze its expression levels of genes involved in neuronal dendritic morphology (Dlg4, Rac1, RhoA, Doc2b), synaptic transmission (Nr1, Grin2A, Grin2B) and glucocorticoid receptor (Nr3C1) in hippocampus (HPC), prefrontal cortex (PFC) and amygdala (AMYG). Results revealed that lambs from stressed dam (PS lambs) showed under-expression of Rac1 and Nr1 in PFC and overexpression of Dlg4 in AMYG compared to controls. To assess the morphological consequences of gene dysregulations, the dendritic morphology of pyramidal neurons was explored by Golgi-Cox staining in HPC and PFC. PS lambs had higher dendritic spine density in both structures and more stubby-type spines in the CA1 area of HPC than controls. This is the first demonstration in sheep that PS alters fetal brain, possibly reflecting functional changes in synaptic transmission to cope with adversity experienced in fetal life.