Anti-inflammatory Agents

Human milk lacks inflammatory mediators or their initiating systems (Goldman et al., 1986), but it contains a host of anti-inflammatory agents including agents that double as direct protective agents, antioxidants, enzymes that degrade inflammatory mediators, antienzymes, cytoprotective agents, and modulators of leukocyte activation (Goldman et al., 1986, 1990). Some of these agents are also components of the antimicrobial system in human milk, whereas others that have antioxidant activity, such as α-tocopherol and β-carotene, are also nutrients.

Enzymes

Human milk contains numerous proteins with enzyme activity (Hamosh, 1989; Hamosh et al., 1985a; Jenness, 1979; Shahani et al., 1980) (see Table 6-6 for examples of enzymes and enzyme functions). Little is known about the effects of maternal nutritional status on the amounts or activity levels of enzymes in milk. However, it is known that the regulation of enzyme activity in the lactating mammary gland differs from that of identical enzymes in other organs. Thus, in the lactating mammary gland the activity of lipoprotein lipase, which is markedly reduced in adipose tissue by fasting, is unaffected by fasting (Hamosh and Hamosh, 1983). The major fat-digesting enzyme in human milk (bile salt-stimulated lipase) is not affected by feeding pattern or diurnal variation (Hamosh et al., 1985b) or by nutritional status of the mother (Hernell et al., 1977).

Hormones, Growth Factors, and Inducers

Human milk contains many hormones, growth factors, and inducers of certain biologic processes (see reviews by Koldovskỳ [1989] and Koldovskỳ et al. [1987]). The hormones include cortisol (Koldovskỳ [1989]), somatostatin (Werner et al., 1985), insulin (Cevreska et al., 1975), thyroid hormones, and the lactogenic hormones oxytocin (Leake et al., 1981) and prolactin (Healy et al., 1980). There is agreement among investigators concerning the measurement of most of these agents, but there is considerable disagreement regarding measurement of thyroid hormones and some others (see review by Koldovskỳ et al. [1987]). The growth factors include epidermal growth factor (Carpenter, 1980), insulin (Cevreska et al., 1975), lactoferrin (Nichols et al., 1987), and factors that are specifically derived from the mammary gland epithelium (Kidwell et al., 1987). There is laboratory evidence for the presence of activators of monocytes such as tumor necrosis factor-β (Mushtaha et al., 1989a,b). Bendich and coworkers (1984) and Tengerdy et al. (1981) presented evidence that the vitamin α-tocopherol in human milk may stimulate the immune system in the



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