Energy restriction affect liver development in Hu sheep ram lambs through Hippo signaling pathway

This study aimed to evaluate the effects of dietary energy restriction on postnatal liver development in Hu sheep ram lambs. A total of 16 ram lambs were randomly divided into two groups: 100% energy requirements diet and 55% energy requirements diet, which were fed for 75 d. Results showed that the final body and liver weights decreased with energy restriction (p <0.05). Energy restriction caused a significant decrease in the levels of circulating insulin-like growth factor 1 (IGF1) and an increase in growth hormone secretion (p <0.05), which can be explained by the decreased mRNA expression levels of the growth hormone receptor (GHR) and IGF1 (p <0.05). The proliferating cell nuclear antigen (PCNA), Ki-67 and apoptosis-related proteins (BAX and BCL2) were mainly located in the nucleus and the cytoplasm of hepatocytes, respectively. The transcription and protein levels of PCNA and BAX were significantly decreased and increased by energy restriction, respectively (p <0.05). The caspase9 and caspase3 mRNA and activity were increased in energy restriction group (p <0.05). Moreover, Hippo signaling pathway proteins [mammalian sterile 20-like protein kinase 1 (MST1), large tumor suppressor kinase 1 (LATS1), and yes-associated protein 1 (YAP1)] were mainly observed around the hepatic portal area, and the expression levels of their mRNA and proteins were significantly decreased in energy restriction group (p <0.05). In summary, energy restriction in ram lambs impairs liver development by increasing apoptosis, which may occur via the Hippo signaling pathway.