Abstract
Within-litter uniformity in pigs is a major factor affecting piglet survival and growth performance. We know that Meishan (MS) gilts have higher piglet survival rate than Large White (LW) gilts because their foetal weight is less varied. To understand the molecular basis for placental nutritional transport during the late stages of gestation in LW and MS, we employed the isobaric tags for relative and absolute quantification (iTRAQ) method to investigate alterations in the placental proteomes of LW and MS gilts on gestational day 90. Investigation of foetal weight at different uterine positions revealed that the foetal and placental weights as well as the foetal concentration of glucose were significantly higher in LW gilts positioned towards the utero-tubal junction than in those positioned toward the cervix; however, no such differences were observed in MS gilts, and MS gilts had a greater uniformity in foetal weight on day 90 of gestation. Comparisons of the proteomes between placentas positioned toward the cervix and those positioned toward the utero-tubal junction identified 38 differentially expressed proteins in the two breeds. These proteins play a central role in nutrient transport and metabolism, as well as in transcriptional and translational regulation. Of particular interest is the finding that the placentas of LW gilts showed 14 differential expression of proteins mainly related to lipid transport and energy metabolism (including solute carrier family 27, mitochondrial trifunctional protein, and NADH dehydrogenase [ubiquinone] flavoprotein 2), but only 2 proteins in MS gilts. In contrast, the differentially expressed proteins in MS gilts were primarily involved in transcriptional and translational regulation (such as ribosome-sec61 and 40S ribosomal protein S23), with a few related to glucose and coenzyme transport and metabolism (including glucose transport protein and ferrochelatase). Our results revealed that placental lipid and energy metabolism might play a crucial role in the regulation of foetal weight, based on uterine position in two distinct pig breeds. These findings provide a deeper understanding of placental efficiency that can be utilized to provide a new method to enhance the efficiency of livestock production.
Highlights
Within-litter variation in foetal weight (CVweight) is a major concern in the animal
The expression of differentially expressed proteins related to energy metabolism was affected by uterine position and breed. Expressed proteins such ascytochrome b5, V-type proton ATPase 116 kDa subunit, delta(24)-sterol reductase, adrenodoxin and NADH dehydrogenase [ubiquinone] flavoprotein 2 were higher in the placentas located at the utero-tubal junction than in those located at the cervix in Large White (LW) gilts
We identified a total of 38 proteins in LW and MS gilts that were differentially expressed depending on the position of the placenta within the uterus: 28 proteins were identified in LW gilts and 15 proteins were identified in MS gilts
Summary
Within-litter variation in foetal weight (CVweight) is a major concern in the animal. While there are probably numerous contributors to the higher proportion of low-birth-weight piglets in a litter, the factor that has attracted much attention is the efficiency of placental transport and metabolism [5,6], a better understanding of it can assist us in solving problem of CVweight. Several studies investigating the relationship between intrauterine position and foetal weight have indicated that foetal weight increases linearly from the cervix to the utero-tubal junction during late gestation [10, 11]. Foetal weight differences at both sides of the uterine horn represent an important factor influencing CVweight and may be associated with differences in placental nutrient transport efficiency according to uterine position [12]. Information about the molecular mechanisms regulating placental nutrient transport is critical for understanding the CVweight in LW and MS gilts during pregnancy, as well as how maternal nutrition and metabolic disturbances affect foetal growth
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