Amino acids and mammary gland development: nutritional implications for milk production and neonatal growth

Abstract

Milk is synthesized by mammary epithelial cells of lactating mammals. The synthetic capacity of the mammary gland depends largely on the number and efficiency of functional mammary epithelial cells. Structural development of the mammary gland occurs during fetal growth, prepubertal and post-pubertal periods, pregnancy, and lactation under the control of various hormones (particularly estrogen, growth hormone, insulin-like growth factor-I, progesterone, placental lactogen, and prolactin) in a species-and stage-dependent manner. Milk is essential for the growth, development, and health of neonates. Amino acids (AA), present in both free and peptide-bound forms, are the most abundant organic nutrients in the milk of farm animals. Uptake of AA from the arterial blood of the lactating dam is the ultimate source of proteins (primarily β-casein and α-lactalbumin) and bioactive nitrogenous metabolites in milk. Results of recent studies indicate extensive catabolism of branched-chain AA (leucine, isoleucine and valine) and arginine to synthesize glutamate, glutamine, alanine, aspartate, asparagine, proline, and polyamines. The formation of polypeptides from AA is regulated not only by hormones (e.g., prolactin, insulin and glucocorticoids) and the rate of blood flow across the lactating mammary gland, but also by concentrations of AA, lipids, glucose, vitamins and minerals in the maternal plasma, as well as the activation of the mechanistic (mammalian) target rapamycin signaling by certain AA (e.g., arginine, branched-chain AA, and glutamine). Knowledge of AA utilization (including metabolism) by mammary epithelial cells will enhance our fundamental understanding of lactation biology and has important implications for improving the efficiency of livestock production worldwide.

Alpha-ketoglutarate enhances milk protein synthesis by porcine mammary epithelial cells

“…The number of mammary cells and the amount of nutrients available to those mammary cells are the main determinants of milk production (Kim and Wu 2009). Hence, promoting the proliferation of mammary epithelial cells and enhancing their synthesis of milk-specific proteins are two effective ways to improve the lactation performance of mammals (Bauman et al 2008;Rezaei et al 2016). In recent years, studies have focused on nutritional and hormonal regulation of mammary gland metabolism (McCormick et al 2014;Wang et al 2014;Lei et al 2012aLei et al , b, 2013.…”

“…The lactation performance of sows plays a key role in pork production (Rezaei et al 2016). It has been suggested that the milk yield of sows is influenced by various factors such as genotype, nutrition (Quesnel et al 2009), physical activity and sucking stimulation (Malmkvist et al 2012).…”

Breast Milk Polyamines and Microbiota Interactions: Impact of Mode of Delivery and Geographical Location

“…Polyamines are synthesised by lactating mammary tissue [6] and are involved in the hormonal regulation of lactogenic processes in the mammary gland [7] , which can explain their presence in milk. A large individual variation in polyamine levels in human milk has been recorded and is related to the age of the mother, ethnic origin, dietary intake of polyamines and nutritional status, among other factors [3,8] .…”

Kp‐10 promotes bovine mammary epithelial cell proliferation by activating GPR54 and its downstream signaling pathways

“…Ensuring adequate mammary epithelial cells helps improve milk production by bovines. The proliferation of mammary gland cells is controlled by numerous elements, such as hormones and nutrients (Osorio, Lohakare, & Bionaz, ; Rezaei, Wu, Hou, Bazer, & Wu, ). It has been reported that estrogens recognize the estrogen receptor and then promote the proliferation of mammary epithelial cells during puberty (Brisken & O'Malley, ).…”