Control of fatty acid synthesis in lactation

Abstract

Lactation results not only in major changes in the metabolism of the mammary gland, but also in the metabolism of other organs of the body, for it is clear that the massive demands which lactation imposes on the body require a co-ordinated adaptation of metabolism in the whole animal (Bauman & Currie, 1980; Williamson, 1980). Fatty acid synthesis provides a good example of such co-ordinated adaptation, for changes in lipogenic activity during lactation have been shown to occur in liver, white adipose tissue and brown adipose tissue as well as in the mammary gland. It is the nature and regulation of these adaptations which will form the main thesis of this review. Rates of fatty acid synthesis during Lactation In most studies, changes in the rate of fatty acid synthesis with and during lactation have been measured in vitro using either tissue slices, isolated cells or, in the case of mammary gland, isolated acini and using saturating concentrations of substrates. Results from such preparations have to be treated with caution (Mayer, 1978) and are not necessarily the same as those occurring in vivo; nevertheless they have provided useful information which in the case of the rat (Williamson, 1980) and mouse (Romsos et aL. 1978) have been confirmed (qualitatively) by measurement of the rate of fatty acid synthesis in vivo. Changes in the capacity for fatty acid synthesis can also be inferred from changes in the activity of key lipogenic enzymes, especially acetyl-CoA carboxylase which, as in liver and adipose tissue (Pearce, 1983)~ is thought to be rate limiting in the mammary gland