[P4-07] Effects of starvation-induced negative energy balance (NEB) on endoplasmic reticulum (ER) stress in the liver of dry cows
Objective: To find out the effect of starvation-induced NEB on ER stress in the liver of dry cows. Methods: Blood sample and liver tissue were collected from 6 non-lactating cows before and after starvation for 48 h. The blood NEFA, BHB and glucose level were analyzed. RNA and protein were extracted from liver biopsy tissue. Results: Starvation for 48 h increased blood BHB and NEFA levels whereas decreased glucose level. Among the unfolded protein response related gene, XBP1s expression in liver was increased after a 48 h starvation but no difference found in ATF4 and CHOP. The protein level of p-IRE1α (an upstream of XBP1) was also increased. The mRNA levels of PPARα and its target gene for ketogenesis, ACOX1 and HMGCS2, were increased after a 48 h starvation but no change noted in PPARγ, a regulator of lipogenesis and other lipogenic gene SREBP1 and FASN. Therefore, starvation-induced NEB promotes the adaptive response in liver by activating the IRE1a-XBP1 pathway.