Leptin Affects Prolactin Action on Milk Protein and Fat Synthesis in the Bovine Mammary Gland

Abstract

Leptin, a protein hormone produced and secreted predominantly by white adipose tissue, has a critical role in the regulation and coordination of energy metabolism. Identification of leptin in the milk of several mammals, including humans, led us to investigate its presence and regulatory effect in the cow mammary gland. The expression of leptin receptor in tissue culture of lactating mammary gland was augmented approximately 25 times by prolactin, but had no effect on virgin calf mammary tissue. Expression of leptin in tissue culture from mammary glands of lactating cows was enhanced 2.2-fold by prolactin. No effect of prolactin on leptin and leptin receptor expression was found in mammary gland tissue culture from calves. Leptin-enhanced fatty acid synthesis in the presence of prolactin, but had no effect without presence of prolactin. A similar pattern was found in the expression of alpha-casein and beta-lactoglobulin in mammary gland explants from a lactating cow. Our findings indicate that leptin plays an important role in mammary gland lactogenesis, and that the expression of leptin requires the presence of prolactin.

Fat Depot-Specific Differences in Angiogenic Growth Factor Gene Expression and Its Relation to Adipocyte Size in Cattle

“…Real-time PCR was performed with a Mini Opticon (Bio-Rad, Munich, Germany) using SYBR Green Real-time PCR Master Mix-Plus (Toyobo) according to the manufacturer's instructions. The primers for bovine angiogenic growth factors were designed as previously described [12,24,27,32,36]. The primer sequences were as follows: VEGF, 5'-GAA CTT TCT GCT CTC TTG GG-3' (forward) and 5'-CTG GCT TTG GTG AGG TTT GA-3' (reverse) [24]; FGF-2, 5'-ACC GGT CAA GGA AAT ACT CCA G-3' (forward) and 5'-CAG GTC CTG TTT TGG GTC CA-3' (reverse) [27]; FGF-10, 5'-AAC TCC TCT TCT TCT TCC TC-3' (forward) and 5'-TTC ACA GCA ACA ACT CCG AT-3' (reverse) [24]; HGF, 5'-CGC TAC GAA GTC TGT GAC ATT CC-3' (forward) and 5'-GAT CCA TGG GAC CTC GGT AA -3' (reverse) [32]; Leptin, 5'-GGA GAA GGT CCC GGA GGT T-3' (forward) and 5'-GGA CCA GAC ATT GGC GAT CT-3' (reverse) [12]; Ribosomal protein large P0 (RPLP0), 5'-CAA CCC TGA AGT GCT TGA CAT -3' (forward) and 5'-AGG CAG ATG GAT CAG CCA -3'(reverse) [36].…”

β-casein gene expression by in vitro cultured bovine mammary epithelial cells derived from developing mammary glands

“…Several groups have adopted this technique to study the action of hormones in the mammary gland, demonstrating the effect of leptin on the synthesis of milk proteins and lipids (Feuermann et al, 2004) and the influence of somatotrophin on β-casein mRNA levels (Yang et al, 2005). The great advantage of this culture strategy is the similarity in cellular composition and extracellular matrix to the in vivo tissue; therefore, the results of experimental manipulations closely represent what would occur in the natural environment.…”

Prolactin affects leptin action in the bovine mammary gland via the mammary fat pad

“…Locally produced growth factors are believed to mediate the adipocyte-epithelial interactions and to alter the actions of several steroid and peptide hormones in these tissues (Hovey et al 1999). Among the different factors controlling the fate of the mammary gland, leptin may be involved in the metabolic changes occurring during lactation (Feuermann et al 2004). Leptin, a protein hormone secreted predominantly by white adipose tissue (Friedman & Halaas 1998), is therefore a key factor in regulating the metabolic adaptation of nutrient partitioning during the energyconsuming processes of pregnancy and lactation (Moschos et al 2002).…”