Absence of Serum-Stimulated Lipase Activity and Altered Lipid Content in Milk from a Patient with Type I Hyperlipoproteinaemia

Abstract

SummaryWe measured the serum-stimulated lipase activity, fatty acid content, and various biochemical parameters in the breast milk of a lactating mother suffering from familial lipoprotein lipase deficiency and of healthy control subjects. Serum-stimulated lipase activity was virtually undetectable in milk from our patient and the total fatty acid content was low. The fatty acid composition differed from normal showing a marked absolute and relative increase in the content of lauric (C12:O) and myristic (C14:O) fatty acids and considerably reduced levels of oleic (C18:l) and especially linoleic (C18:2) acids. Other fatty acid species showed lesser changes in concentration. Besides a reduced calcium concentration in the milk from our patient, other biochemical parameters were not significantly different from control subjects. (15) and other species including the rat (30), cow (8, 21), guinea pig (28, 37), and goat (45). Milk SSL resembles adipose AT-LPL with respect to substrate specificity, molecular weight, susceptibility to inhibition by 1.0 M sodium chloride or protarnine sulfate, dependence on apo CII for activity and immunologic specificity (25,32). The presumed identity of the two enzymes has not, however, been verified in terms of amino acid composition, and the enzymes are reciprocally regulated by prolactin, which is a powerful and rapid inducer of SSL synthesis but represses the adipose tissue enzyme (46). Evidence derived from animal studies (1, 2, 4, 11) and from manipulation of the fat intake of lactating mothers (20), indicates that plasma triglyceride of dietary origin, dependent presumably on mammary gland LPL activity (25, 27, 28,3 1, 39), makes a substantial contribution to milk lipid production. Scow et al. (40) have proposed that triglyceride present in chylomicrons and in very low density lipoprotein are hydrolysed at the capillary endothelial cell surface with liberation of fatty acids, partial glycerides, and glycerol that fmd their way into alveolar cells by diffusion in the plane of the membrane. Other sources of milk fatty acid include de novo synthesis within the mammary gland and uptake of NEFA from the plasma, derived ultimately from depot fat stores (20,27). AbbreviationsA patient under our care, with the typical clinical and biochemical features of type I hyperlipoproteinaemia (10, 16), recently became pregnant and was delivered of a normal male offspring. We were able to obtain milk for lipase assay and for the determination of lipid content on three separate occasions. Our results suggest that milk SSL and AT-LPL depend on a common or closely-related genetic locus for normal synthesis and that mammary gland SSL is an important determinant of the composition of milk lipid. MATERIALS AND METHODSCase report. Our patient, Mrs. N, was a 33-year-old female of Asiatic extraction with a history of repeated episodes of abdominal pain of undetermined origin since childhood. Shortly after her marriage, ten years before this study, Mrs. N gave birth to a normal infant but since that time h...

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