Lipoprotein lipase activity and its relationship to high milk fat transfer during lactation in grey seals

Abstract

Lipoprotein lipase regulates the hydrolysis of circulating triglyceride and the uptake of fatty acids by most tissues, including the mammary gland and adipose tissue. Thus, lipoprotein lipase is critical for the uptake and secretion of the long-chain fatty acids in milk and for the assimilation of a high-fat milk diet by suckling young. In the lactating female, lipoprotein lipase appears to be regulated such that levels in adipose tissue are almost completely depressed while those in the mammary gland are high. Thus, circulating fatty acids are directed to the mammary gland for milk fat production. Phocid seals serve as excellent models in the study of lipoprotein lipase and fat transfer during lactation because mothers may fast completely while secreting large quantities of high fat milks and pups deposit large amounts of fat as blubber. We measured pup body composition and milk fat intake by isotope (deuterium oxide) dilution and plasma post-heparin lipoprotein lipase activity in six grey seal (Halichoerus grypus) mother-pup pairs at birth and again late in the 16-day lactation period. Maternal post-heparin lipoprotein lipase activity increased by an average of four-fold by late lactation (P = 0.027), which paralleled an increase in milk fat concentration (from 38 to 56%; P = 0.043). Increasing lipoprotein lipase activity was correlated with increasing milk fat output (1.3-2.1 kg fat per day) over lactation (P = 0.019). Maternal plasma triglyceride (during fasting) was inversely correlated to lipoprotein lipase activity (P = 0.027) and may be associated with the direct incorporation of long-chain fatty acids from blubber into milk. In pups, post-heparin lipoprotein lipase activity was already high at birth and increased as total body fat content (P = 0.028) and the ratio of body fat: protein increased (P = 0.036) during lactation. Although pup plasma triglyceride increased with increasing daily milk fat intake (P = 0.023), pups effectively cleared lipid from the circulation and deposited 70% of milk fat consumed throughout lactation. Lipoprotein lipase may play an important role in the mechanisms involved with the extraordinary rates of fat transfer in phocid seals.

Decreased expression of adipose CD36 and FATP1 are associated with increased plasma non-esterified fatty acids during prolonged fasting in northern elephant seal pups (Mirounga angustirostris)

“…Interestingly, elephant seals maintain rates of glucose production and use more glucose than expected for an animal enduring such a prolonged fast (Champagne et al, 2005). The present study suggests that northern elephant seal pups possess robust mechanisms to regulate circulating lipids, a characteristic that may not be shared by other seals; for example, fasting duration decreases NEFA concentration in grey and hooded seal pups (Iverson et al, 1995;Mellish et al, 1999). These mechanisms may include decreasing the expression of CD36 and FATP1 and increasing the expression of ATGL in adipose tissue.…”

Transfer of fatty acids from mothers to their calves during lactation in white whales Delphinapterus leucas

“…FAs with 20 and 22 carbons are not readily synthesized in mammals (Iverson et al 1995b). The low amounts of these FAs in the blubber of the shortest calf indicate that this animal was probably younger than the other calf still bearing an umbilical cord (closer to newborn) (see Iverson et al 1995a).…”

Association of a polymorphism in the 3' untranslated region of the <i>OLR1</i> gene with milk fat and protein in dairy cows

“…Iverson et al (1995) revealed a relationship between lipoprotein lipase activity and high milk fat during lactation in grey seals. There may be an association of this kind in bovine mammary gland also.…”