Effect of Human Milk Fortifier on the Immunodetection and Molecular Mass Profile of Transforming Growth Factor-Alpha

Abstract

Objective: To determine if the addition of human milk fortifier (HMF) affects the distribution, immunoreactivity, or molecular mass profile of transforming growth factor-α (TGF-α) within the compartments of human milk. Methods: Fifteen milk samples were obtained. Each sample was divided into two aliquots; a powdered HMF was added to the first aliquot. TGF-α concentration was measured via radioimmunoassay in whole milk and its aqueous and fat fractions ± HMF. TGF-α molecular mass profiles of the samples (v/v) were measured via Western blotting. Results: TGF-α concentration (mean ± SD) in fortified whole milk (15.7 ± 7.1 pg/100 μl) vs. nonfortified whole milk (14.8 ± 8.0 pg/100 μl) and in the aqueous fraction of fortified (14.0 ± 2.7 pg/100 μl) vs. nonfortified (14.0 ± 3.5 pg/100 μl) did not differ statistically. There was, however, a marked decrease in the concentration of TGF-α in the fat fraction of fortified (30.6 ± 2.8 pg/100 μl) vs. nonfortified (98.0 ± 6.9 pg/100 μl) milk samples. Western blot for TGF-α in whole milk and its separated fractions revealed characteristic bands at 6.5, 12–16, 22, 26–30 and 46 kD. HMF alone and HMF with sodium taurocholate had a prominent band at 18 kD and fainter bands at 6.5, 26–30, and 46 kD. While whole and aqueous milk samples with HMF also consistently showed the 18-kD band, in 8/15 fat fraction samples with HMF the 18-kD band was nondetectable and was only faintly detectable in the remaining 7/15 samples. Conclusions: It appears that HMF differentially alters the biochemical profile of human milk with regard to TGF-α concentration and molecular mass profile. What effect this alteration in human milk biochemistry has on neonatal gut function remains unknown.