TGF-ß2, a protective intestinal cytokine, is abundant in maternal human milk and human-derived fortifiers but not in donor human milk.

OBJECTIVE: This study compared cytokines (in particular transforming growth factor [TGF]-ß2) and lactoferrin in maternal human milk (MHM), human-derived milk fortifier (HDMF), and donor human milk (DHM). MATERIALS AND METHODS: MHM was randomly collected from breastfeeding mothers who had no infectious illness at the time of milk expression. HDMF and DHM were products derived from human milk processed by Holder pasteurization. MHM samples were collected at different times (early/late) and gestations (preterm/term). Lactoferrin was analyzed by western blotting, and cytokines were quantified using commercial enzyme-linked immunosorbent assays. Significance was determined using analysis of variance. RESULTS: In the 164 samples analyzed, TGF-ß2 concentrations in HDMF and preterm MHM (at all collection times) were fivefold higher than in DHM (p<0.05). Early preterm MHM had levels of interleukin (IL)-10 and IL-18, 11-fold higher than DHM (p<0.05). IL-6 in DHM was 0.3% of the content found in MHM. IL-18 was fourfold higher in early MHM versus late MHM regardless of gestational age (p<0.05). Lactoferrin concentration in DHM was 6% of that found in MHM. CONCLUSIONS: Pasteurization decreases concentrations of most cytokines and lactoferrin in DHM. TGF-ß2, a protective intestinal cytokine, has comparable concentrations in HDMF to MHM despite pasteurization.

Preterm human milk contains a large pool of latent TGF-ß, which can be activated by exogenous neuraminidase.

Human milk contains substantial amounts of transforming growth factor (TGF)-ß, particularly the isoform TGF-ß2. We previously showed in preclinical models that enterally administered TGF-ß2 can protect against necrotizing enterocolitis (NEC), an inflammatory bowel necrosis of premature infants. In this study we hypothesized that premature infants remain at higher risk of NEC than full-term infants, even when they receive their own mother's milk, because preterm human milk contains less bioactive TGF-ß than full-term milk. Our objective was to compare TGF-ß bioactivity in preterm vs. full-term milk and identify factors that activate milk-borne TGF-ß. Mothers who delivered between 23 0/7 and 31 6/7 wk or at ≥37 wk of gestation provided milk samples at serial time points. TGF-ß bioactivity and NF-κB signaling were measured using specific reporter cells and in murine intestinal tissue explants. TGF-ß1, TGF-ß2, TGF-ß3, and various TGF-ß activators were measured by real-time PCR, enzyme immunoassays, or established enzymatic activity assays. Preterm human milk showed minimal TGF-ß bioactivity in the native state but contained a large pool of latent TGF-ß. TGF-ß2 was the predominant isoform of TGF-ß in preterm milk. Using a combination of several in vitro and ex vivo models, we show that neuraminidase is a key regulator of TGF-ß bioactivity in human milk. Finally, we show that addition of bacterial neuraminidase to preterm human milk increased TGF-ß bioactivity. Preterm milk contains large quantities of TGF-ß, but most of it is in an inactive state. Addition of neuraminidase can increase TGF-ß bioactivity in preterm milk and enhance its anti-inflammatory effects.