HUMAN-MILK AND INFANT FORMULA CAN INDUCE IN-VITRO ADIPOCYTE DIFFERENTIATION IN MURINE 3T3-L1 PREADIPOCYTES

The potential of infant diet to influence fat cell development has lar gely been examined in clinical studies with conflicting results. In th is study, the direct effects of two standard infant formulas, Enfamil and Similac, as well as human mill; were examined using a well charact erized model of adipocyte differentiation, the 3T3-L1 murine preadipoc yte cell line. After exposure to a hormonal regimen of insulin, dexame thasone, and 1-methyl-3-isobutylmethylxanthine, these cells undergo a mitotic expansion phase followed by terminal differentiation. On d 4 o f hormonal exposure, greater than 95% of 3T3-L1 cells exhibit the morp hologic and biochemical characteristics of mature adipocytes. In this study, cells were exposed to control medium, or control medium supplem ented with either 10% Enfamil, 10% Similac, 10% human milk (skim or wh ole), or the standard hormonal regimen. Oil Red O-detectable lipid acc umulation, immunocytochemical cell proliferation assays, and activated expression of adipocyte differentiation-specific mRNAs by Northern bl ot analysis were used to assess the effects of treatment on adipocyte differentiation. Results from each level of assess ment revealed that both Enfamil and human milk were as effective as the standard hormonal regimen at stimulating adipocyte differentiation. In contrast, result s from treatment with Similac or human skim milk were indistinguishabl e from control unstimulated cells. This study, demonstrating that Enfa mil and human milk are capable of independently inducing in vitro adip ocyte differentiation, suggests that diet during infancy could influen ce body fat development.