Effects of weaning on somatotrophic gene expression and circulating levels of insulin-like growth factor-1 (IGF-1) and IGF-2 in pigs.
The present study evaluated somatotrophic gene expression in liver, muscle and adipose tissue 4 d after weaning, a time point corresponding to greatly reduced serum concentrations of insulin-like growth factor (IGF)-1 and IGF-2 in pigs. Two-week-old barrows were either cross-fostered to a sow (SOW, n = 8) or weaned and fed a phase 1 diet containing either 0 or 7% spray-dried plasma (NP, n = 8 and SDP, n = 8; respectively). Piglets were allocated such that two size groups were equivalently represented in each experimental group (small, 3.5-4.3 kg and large, 4.6-5.7 kg). Animals were weighed daily and sacrificed 4 d after weaning for blood and tissue collection. Daily gains of the SOW piglets were significantly greater than those of the weaned pigs for the first 3 d of the experiment (P < 0.0001). Weight gains in the SOW and SDP pigs between d 3 and 4 were equivalently elevated relative to the NP pigs (P < 0.0001). Serum IGF-1 and IGF-2 concentrations were decreased in both NP and SDP compared to SOW (P < 0.0001). Serum IGF-2 levels were significantly lower in small piglets (P = 0.006). A Weaning Group X Size interaction was noted for liver IGF-2 mRNA (P < 0.03), reflecting a higher level of expression in large SOW piglets relative to small SOW piglets. Weaning did not affect IGF-1, IGF-2, or growth hormone (GH) receptor mRNA levels in liver, muscle, or fat (P > 0.05). Liver IGF-binding protein (IGFBP)-3 and acid-labile subunit (ALS) mRNA levels also were unaffected by weaning. Small pigs had lower levels of liver ALS (P = 0.0003), muscle IGF-2 (P = 0.02), and muscle GH receptor (P = 0.006) mRNAs. In contrast, adipose tissue IGF-1 and IGF-2 mRNA levels were greatest in the small piglets (P = 0.001 and 0.029, respectively).
Matteri
R L
RL
Animal Physiology Unit, Agricultural Research Service, United States Department of Agriculture, Room S-107 Animal Sciences Research Center, University of Missouri, Columbia, MO 65211, USA. matterir@missouri.edu
Dyer
C J
CJ
Touchette
K J
KJ
Carroll
J A
JA
Allee
G L
GL
D000273:Adipose Tissue / Q000737:chemistry; D000818:Animals; D000911:Antibodies, Monoclonal; D001483:Base Sequence; D015152:Blotting, Northern; D001835:Body Weight; D004247:DNA / Q000737:chemistry; D017931:DNA Primers / Q000737:chemistry; D005260:Female; D018507:Gene Expression Regulation, Developmental; D007334:Insulin-Like Growth Factor I / Q000032:analysis / Q000096:biosynthesis* / Q000235:genetics; D007335:Insulin-Like Growth Factor II / Q000032:analysis / Q000096:biosynthesis* / Q000235:genetics; D008099:Liver / Q000737:chemistry; D008297:Male; D008969:Molecular Sequence Data; D018482:Muscle, Skeletal / Q000737:chemistry; D012313:RNA / Q000737:chemistry / Q000302:isolation & purification; D011863:Radioimmunoassay / Q000662:veterinary; D011897:Random Allocation; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000662:veterinary; D017422:Sequence Analysis, DNA; D013552:Swine / Q000254:growth & development* / Q000502:physiology; D014886:Weaning; D015430:Weight Gain
D000911:Antibodies, Monoclonal; D017931:DNA Primers; D012313:RNA; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II; D004247:DNA