Characterization of milk and soy phospholipid liposomes and inflammation in 3T3-L1 adipocytes

Abstract

Milk phospholipids (PL) are valuable dairy components that appear to impart human health benefits, including improved cognitive function in infants and adults. The commercial food industry uses primarily plant-based sources of PL, such as soy lecithin. However, it remains unclear whether different compositions of PL from different dietary sources, such as milk, convey the same benefits. We hypothesized that PL derived from bovine milk or soy have differing physiological effects in terms of inflammation due to their differences in composition. The objectives of this study were to characterize milk and soy liposomes by their physicochemical properties and composition and to evaluate their effects in vitro by means of inflammatory gene expression analyses. Milk and soy phospholipid large unilamellar vesicles (MPL-LUV and SPL-LUV, respectively) prepared using thin-film hydration coupled with extrusion were similar in terms of structure, size, and stability; however, they differed significantly in composition. The 3T3-L1 adipocytes were selected for this work because adipocytes are the main site of uptake, synthesis, modification, and breakdown of lipids and are important inflammatory mediators in mammalian systems. In this work, these cells exposed to both liposome varieties showed high biocompatibility and low cytotoxicity up to concentrations of 0.5 mg/mL as measured by colorimetric MTT and lactate dehydrogenase assays. Furthermore, SPL-LUV showed trends toward stimulating inflammation compared with MPL-LUV as measured by expression of 2 proinflammatory cytokines, monocyte chemoattractant protein-1 (MCP-1) and IL-6. Expression of MCP-1 significantly increased 1.82-fold relative to the control upon SPL-LUV treatment, with similar trends for IL-6 (increased 1.59-fold). The MPL-LUV showed relatively no change in cytokine expression. The results obtained in this work suggest that the methodology used to prepare LUV and the composition and proportion of milk PL are important in measuring cell physiology changes and inflammatory status in mammalian cells.