TGFβ2 DISTRIBUTION IN AQUEOUS AND FAT COMPARTMENTS OF HUMAN MILK. 494

Human milk contains transforming growth factor-beta isoforms(TGFβ₁ and β₂). TGFβ affects growth and differentiation of neonatal intestinal epithelia, and modulates restitution of the gut epithilium following injury. A differential distribution of some bioactive factors in milk fat and aqueous fractions has been shown, which could affect bioavailability. It is unknown if TGF-β₂ shares similar distribution properties. We sought to determine if there is a differential concentration of TGFβ₂ in human milk aqueous and fat compartments. Eighteen milk samples were collected from 15 lactating mothers on postpartum day 2 to 27; gestational age of their infants at delivery ranged from 24 to 40 weeks. Whole milk was centrifuged at 2500g × 20 min at 4°C to achieve separation and isolation of its fat, aqueous and cellular components. Sodium taurcholate(STC) was added to the fat for emulsion. The concentration of acid-activated TGFβ₂ in the aqueous and fat components of human milk was measured by ELISA (R&D Systems; sensitivity 55 pg/ml sample; cross-reactivity with other TGFβ species/receptors is not significant; standard curve unaffected by STC). TGFβ₂ was detected in all aqueous samples (6214 ± 5083 pg/mL; range 1619 to 20686); and all fat samples (6987 ± 5344 pg/mL; range 1736 to 20576). Similac Special Care formula and Enfamil Premature formula, also tested, did not have detectable levels of TGFβ₂. In conclusion TGFβ₂ is found in high concentrations in both the aqueous and fat compartments of human milk. These findings may be of significance for differential distribution and bioavailability of TGFβ₂ in the newborn gut. Results of this study are important to future research, as fat is often discarded during human milk investigations.