Lactation decreases pancreatic lipase mRNA level in the rat

Lactation alters maternal metabolism and increases food intake in rats to support milk production. Pancreatic lipase (PL) is primarily responsible for fat digestion in adults and is regulated by dietary fat. The present research determined the regulation of PL by lactation and dietary fat. In Expt 1, eighteen Sprague-Dawley dams and twelve age-matched virgins (controls) were fed a low-fat diet (LF; 11 % energy as safflower oil) for 7-63 d. At postpartum (day 0), peak lactation (day 15) and post-lactation (day 56) and after 7 d in virgins, the pancreas was removed for mRNA and enzyme analyses. In Expt 2, thirty-six Sprague-Dawley dams were fed LF until day 9 postpartum when dams were divided into three groups of twelve; one continued to be fed LF, one was fed a moderate-fat diet (MF; 40 % energy as safflower oil); and one was fed a high-fat diet (HF; 67 % energy as safflower oil) diet. At peak lactation (day 15) and post-lactation (day 56), the pancreas was removed for mRNA and enzyme analyses. Expt 1 revealed that lactation and post-lactation significantly (P< 0.001) decreased PL mRNA (67 % and 76 %, respectively), but only post-lactation decreased PL activity. Increased dietary fat in Expt 2 significantly increased PL mRNA (LF < MF < HF, P< 0.001) and PL activity (LF < MF = HF, P<0.02) in both lactation and post-lactation. In summary, lactation and post-lactation decreased PL mRNA significantly even though dietary fat still regulated PL activity and mRNA in lactation and post-lactation.