Amino acid transportation, sensing and signal transduction in the mammary gland: key molecular signalling pathways in the regulation of milk synthesis

The mammary gland, a unique exocrine organ, is responsible for milk synthesis in mammals. Neonatal growth and health are predominantly determined by quality and quantity of milk production. Amino acids are crucial maternal nutrients that are the building blocks for milk protein and are potential energy sources for neonates. Recent advances made regarding the mammary gland further demonstrate that some functional amino acids also regulate milk protein and fat synthesis through distinct intracellular and extracellular pathways. In the present study, we discuss recent advances in the role of amino acids (especially branched-chain amino acids, methionine, arginine and lysine) in the regulation of milk synthesis. The present review also addresses the crucial questions of how amino acids are transported, sensed and transduced in the mammary gland.

Genetics

Epidemiological studies have demonstrated that osteoarthritis (OA) is a complex trait with numerous environmental and genetic risk factors. A great deal of effort has been spent elucidating these risk factors and progress has been made. It is clear however that the causes behind OA development and progression continue to remain largely elusive. Identification of those genes that, in conjunction with environmental factors, predispose to OA severity will lead to a better understanding of the mechanisms underlying disease development and thus promote improved health strategies for prevention. An understanding of the molecular signalling pathways involved in the initiation and progression of the disease will improve clinical diagnosis and help identify improved, tailored treatment regimens. This chapter focuses on these issues, exploring the heritability of OA, known genetic risk factors, and specific traits and outcomes studied in the genetics of OA.