Exposure to Flaxseed or Purified Lignan During Lactation Influences Rat Mammary Gland Structures.

Key Findings

The objective of this study was to determine whether lactation only is a critical stage of flaxseed feeding that impacts on mammary gland maturation and differentiation and whether the lignan component of flaxseed was responsible for the effects observed. Also, at the end of lactation, rats were switched to a basal diet (BD) or remained on their mother’s diet to evaluate whether continuous exposure to purified SDG or flaxseed resulted in a greater proportion of differentiated mammary gland structures than exposure only during lactation. The mechanism(s) by which exposure to flaxseed or SDG during lactation enhances the differentiation of TEBs to ABs and lobules remains uncertain. Here, exposure to flaxseed during lactation enhanced mammary gland development and, thereby, potentially protects against mammary cancer and perhaps breast cancer in humans. Furthermore, this study provides direct evidence that it is the lignan component in flaxseed that mediates these changes in the mammary gland.

ABSTRACT

Previous investigation demonstrated that feeding a 10% flaxseed (10F) diet during pregnancy and lactation enhanced the differentiation of highly proliferative terminal end bud (TEB) structures of rat mammary gland into less proliferative alveolar buds and lobules. From this study, it was hypothesized that the lignan component in flaxseed mediated the observed effects. Because mammary glands with more TEBs are more susceptible to carcinogens, exposure to flaxseed during early postnatal life may reduce the risk of developing mammary cancer. Our objectives were to elucidate whether exposure to flaxseed during lactation only and during pregnancy and lactation can similarly influence the differentiation of mammary gland structures and also to identify whether the lignan component of flaxseed is the biologically active agent. Offspring were exposed to a 10F diet or a dose of purified lignan equivalent to that in a 10F diet (10S) during lactation only or from lactation to postnatal Day 50. Compared with controls, exposure to 10F or 10S during lactation only or from lactation to postnatal Day 50 reduced the number of TEBs and resulted in a rise in the number of alveolar buds. In conclusion, exposure to flaxseed or its purified lignan during lactation is a critical period in which mammary gland development may be promoted by enhancing the differentiation of the mammary gland structures.  However, continuous exposure, particularly to purified lignans, resulted in the most differentiation of the mammary gland. The next step is to determine whether the changes in mammary gland structures are chemopreventive in rats challenged with a carcinogen.