Effect of fat deposition on placental function in Shaziling sows and modulation by resveratrol

Excessive fat deposition is considered as an important factor impairing reproductive performance in sows, and resveratrol (RES) has shown a hypolipidemic effect in previous studies. This study aimed to investigate the impact of fat deposition on reproductive performance of Shaziling sows, and further clarify the intervention by RES. Fifty-six lard-type Shaziling sows at 75 d of gestation (G75d) were divided into four groups (n = 14) based on backfat thickness (BT): backfat thickness between 20 to 24 mm (NBT) and backfat thickness between 26 to 30 mm (HBT). The NBT-CTL and HBT-CTL groups were fed a basal diet, while NBT-RES and HBT-RES were fed a diet containing 500 mg/kg RES until delivery. Results showed that HBT sows had lower total litter weight (P = 0.008), average weight of total births (P < 0.001), live litter weight (P < 0.001), average weight of live birth (P < 0.001), and placental efficiency (P = 0.013), but higher average process of farrowing (P < 0.001) and stillbirth (P = 0.005), while RES recovered these indicators significantly. In addition, HBT sows showed lower placental vascular density with decreased fluorescence intensity of platelet endothelial cell adhesion molecule-1 (CD31; P = 0.006) and fibroblast growth factor (FGF; P = 0.001), and expression of nutrient transport genes including sodium coupled neutral amino acid transporter 1 (SNAT1; P = 0.029), cluster of differentiation 36 (CD36; P = 0.004). RES increased nutrient transport genes including glucose transporter protein 3 (GLUT3; P < 0.001), GLUT4 (P = 0.014), cationic amino acid transporter 1 (CAT-1; P = 0.005), SNAT2 (P = 0.015), and plasma membrane fatty acid binding protein (FABPpm; P = 0.009), but increased placental vascular density by increasing the expression of placental angiogenesis (FGF; P = 0.013), placental growth factor (PlGF; P < 0.001) and vascular endothelial growth factor (VEGF-A; P = 0.013) in placenta. Additionally, RES recovered the phosphorylation of phosphoinositide 3-kinase (PI3K; P < 0.001), protein kinase B (AKT; P < 0.001), and mammalian target of rapamycin (mTOR; P < 0.001) in placenta of HBT sows. These findings suggest that excessive fat deposition can impair reproductive performance, which is rescued by RES by increasing the expression of placental nutrient transport and angiogenesis genes in lard-type Shaziling sows, and PI3K may play an important role.