Effect of short term diet restriction on gene expression in the bovine hypothalamus using next generation RNA sequencing technology

Background: Negative energy balance (NEB) is an imbalance between energy intake and energy requirements for lactation and body maintenance, affecting high-yielding dairy cows after calving and is of considerable economic importance due to its negative impact on fertility and health in dairy herds. The hypothalamus is central to the neural control of homeostasis. It is anticipated that the cow hypothalamus experience extensive biochemical changes during the early post partum period in an effort to re-establish metabolic homeostasis. There is variation in the tolerance to NEB between individual cows. In order to understand the genomic regulation of ovulation in hypothalamic tissue during NEB transcriptional patterns between tolerant and sensitive animals was examined. A short term dietary restriction heifer model was developed which induced abrupt onset of anoestrus in some animals (Restricted Anovulatory; RA) while others maintained oestrous cyclicity (Restricted Ovulatory; RO). In addition a third control group (C) received a higher level of normal feeding. Heifers were slaughtered and hypothalamic tissue was collected after 18 days of differential feeding. mRNAseq was performed to examine differential gene expression profiles in hypothalamic tissue between groups. Results: A total of 15,295 genes were expressed in hypothalamic tissue. The largest difference between groups was observed in the comparison between RA and RO heifers, with 1094 genes shown to be significantly differentially expressed (SDE). Innatedb pathway analysis showed that these SDE genes were associated with 6 canonical pathways (P < 0.01), of which neuroactive ligand-receptor interaction was the most significant. Within the comparisons the main over-represented pathway functions appear to be immune response including neuroprotection (CXCL10, Q1KLR3, IFIH1, IL1 and IL8; RA v C and RA v RO); energy homeostasis (AgRP and NPY; RA v RO); cell motility (CADH1, DSP and TSP4; RO v C) and prevention of GnRH release (NTSR1 IL1α, IL1β, NPY and PACA; RA v RO). Conclusion: This information assists in understanding the genomic factors regulating the influence of diet restriction on fertility and may assist in to optimise nutritional and management systems that improve reproductive performance. A short term dietary restriction heifer model was developed which induced abrupt onset of anoestrus in some animals (Restricted Anovulatory; RA) while others maintained oestrous cyclicity (Restricted Ovulatory; RO). In addition a third control group (C) received a higher level of normal feeding. Heifers were slaughtered and hypothalamic tissue was collected after 18 days of differential feeding. mRNAseq was performed to examine differential gene expression profiles in hypothalamic tissue between groups.