Evidence for a local effect of leptin in bovine mammary gland.
On average, high-energy diets promoting body growth rates above 1 kg/d before puberty impair mammary development by 15 to 20% in cattle. We hypothesized that leptin, a protein produced by adipocytes, mediates the inhibitory effect of high-energy diets on mammary development. Therefore, our objectives were to determine the effect of leptin on mammary epithelial cell proliferation, and the distribution of mRNA for two leptin receptor isoforms in prepubertal bovine mammary glands and other peripheral tissues. Addition of leptin to culture media containing either 5 ng/ml of insulin-like growth factor-I (IGF-I) or 1% fetal bovine serum decreased DNA synthesis of a bovine mammary epithelial cell line (MAC-T) in a dose-dependent manner. The minimal doses of leptin that decreased IGF-I- and fetal bovine serum-stimulated cell proliferation were 64 and 1 ng/ml, respectively. In addition, we determined that MAC-T cells and isolated bovine mammary epithelial cells express the long form of leptin receptor (Ob-Rb) mRNA. Ob-Rb mRNA was detected in all bovine tissues examined. In contrast with reports on other species, mRNA expression of the short form of leptin receptor (Ob-Ra) was detected only in bovine liver, pituitary body, and spleen. These results support the concept that leptin mediates the inhibitory effect of high-energy diets on mammary development.
Silva
L F P
LF
Department of Animal Science, Michigan State University, East Lansing 48824, USA.
VandeHaar
M J
MJ
Weber Nielsen
M S
MS
Smith
G W
GW
D000818:Animals; D002417:Cattle; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D003470:Culture Media; D004247:DNA / Q000096:biosynthesis; D002149:Energy Intake; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D005260:Female; D005312:Fetal Blood; D015870:Gene Expression; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D020738:Leptin / Q000494:pharmacology*; D008099:Liver / Q000737:chemistry; D008321:Mammary Glands, Animal / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D010902:Pituitary Gland / Q000737:chemistry; D012333:RNA, Messenger / Q000032:analysis; D011956:Receptors, Cell Surface / Q000235:genetics; D054411:Receptors, Leptin; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013154:Spleen / Q000737:chemistry
D003470:Culture Media; D020738:Leptin; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D054411:Receptors, Leptin; D007334:Insulin-Like Growth Factor I; D004247:DNA