ROLE OF MAMMARY GLAND LIPOPROTEIN LIPASE IN THE AVAILABILITY OF POLYUNSATURATED FATTY ACIDS FOR MILK SYNTHESIS

ROLE OF MAMMARY GLAND LIPOPROTEIN LIPASE IN THE AVAILABILITY OF

POLYUNSATURATED FATTY ACIDS FOR MILK SYNTHESIS

E. Amusquivar, I. López-Soldado, H. Ortega, E. Herrera

Faculty of Science and Health. University San Pablo CEU. Madrid. Spain.

Introduction: Mammary gland lipoprotein lipase (LPL) attached to the surface of capillary endothelium has been implicated in the clearance of circulating triacylglycerols (TAG) around parturition. By inhibiting the induction of mammary LPL expression around parturition, this study aimed to determiney whether this enzyme plays a role in driving plasma polyunsaturated fatty acids (PUFA) to the mammary gland for milk synthesis.

Methods: From the onset of pregnancy, Sprague-Dawley rats were fed ad libitum a semi synthetic diet containing 10% of either olive oil or fish oil. From the 19th day of pregnancy half of the rats from each group were s.c. treated with 7 mg of progesterone/day whereas the other half received the medium (controls). All the animals were studied at day 23 of postfecundation.

Results: Mammary gland LPL activity was lower in rats receiving progesterone than in controls, whereas adipose tissue LPL activity did not differ between the two groups. Plasma TAG and FFA were higher in the progesterone rats than in controls. Whereas progesterone treatment enhanced the concentration of 16:0, 18:1, 18:2 and 22:6 in plasma, it decreased the proportion of 18:0, 18:2, 18:3 and 20:5 in mammary gland, although the degree of response varied between the animals fed fish oil diet as compared to the olive oil. In fact, whereas progesterone treatment enhanced the proportion of 20:4 n-6 in mammary gland of rats fed olive oil diet, it did not have any effect in rats fed fish oil diet.

Conclusions: Since decreased LPL activity in mammary gland is associated with enhanced levels of PUFA in plasma and a decreased proportion in the mammary gland, we propose that, around parturition, LPL plays a role in driving circulating PUFA for milk synthesis.

176