Exposure to purified lignan from flaxseed (Linum usitatissimum) alters bone development in female rats.

Key Findings

The overall objective of the present study was to evaluate in female rats if exposure to the purified lignan component from flaxseed during suckling via mother’s milk or continuously during suckling through to adolescence (i.e. postnatal day (PND) 50) or adulthood (i.e. PND 132) would have a positive effect on bone development as indicated by a higher bone mineral content (BMC) accompanied by improved bone biomechanics (increased bone strength) compared with rats exposed only to basal diet (BD) that was devoid of phyto-oestrogens.  The study showed that exposure to dietary lignans does result in stronger bones at adolescence. The long-term consequences of the reduced bone area and BMC observed among rats exposed to lignans at PND 132 in the present study require further investigation. Exposure to dietary oestrogens may be of greater benefit when endogenous oestrogen levels are low as accompanies the ageing process or in specific disease states.

ABSTRACT

Due to the potential oestrogenic effects of secoisolariciresinol diglycoside (SDG), the mammalian lignan precursor in flaxseed (Linum usitatissimum), we hypothesized that exposure to purified SDG during early life would have a positive effect on developing bone. This present study determined whether exposure to SDG purified from flaxseed during suckling via mother’s milk or continuously to adolescence (postnatal day (PND) 50) or adulthood (PND 132) increased bone mineral content (BMC) or bone strength in female rat offspring. Offspring were exposed to basal diet (BD) or one of two doses of SDG (50S, 100S) equivalent to that in a 50 or 100 g flaxseed/kg diet during lactation only or through to PND 50 or 132. At PND 50 and 132, femurs were analysed for BMC by dual energy X-ray absorptiometry and biomechanical strength by a 3-point bending test. Compared with BD group, rats exposed to continuous 50S or 100S diet had stronger femurs at PND 50 without changes in BMC. At PND 132 there were no differences in femur strength despite the fact that continuous exposure to BD resulted in a higher BMC than rats exposed to 100S during lactation only or to 50S or 100S during lactation through to adulthood. In conclusion, female rat bone is more sensitive to the oestrogen-like action of lignans during early life when endogenous levels of sex hormones are low, but by adulthood the improved bone strength does not persist. Importantly, exposure to purified lignan does not have negative effects on bone strength.