Effects of Emulsifier Charge and Concentration on Pancreatic Lipolysis: 2. Interplay of Emulsifiers and Biles

摘要

As a direct continuation of the first part of our in vitro study (Vinarov et al., Langmuir 2012, 28, 8127), here weninvestigate the effects of emulsifier type and concentration on the degree of triglyceride lipolysis, in the presence of bile salts.nThree types of surfactants are tested as emulsifiers: anionic, nonionic, and cationic. For all systems, we observe three regions innthe dependence degree of fat lipolysis, α, versus emulsifier-to-bile ratio, fs: α is around 0.5 in Region 1 (fs < 0.02); α passesnthrough a maximum close to 1 in Region 2 (0.02 < fs < f TR); α is around zero in Region 3 (fs > f TR). The threshold ratio forncomplete inhibition of lipolysis, f TR, is around 0.4 for the nonionic, 1.5 for the cationic, and 7.5 for the anionic surfactants.nMeasurements of interfacial tensions and optical observations revealed the following: In Region 1, the emulsifier molecules arensolubilized in the bile micelles, and the adsorption layer is dominated by bile molecules. In Region 2, mixed surfactant-bilenmicelles are formed, with high solubilization capacity for the products of triglyceride lipolysis; rapid solubilization of thesenproducts leads to complete lipolysis. In Region 3, the emulsifier molecules prevail in the adsorption layer and completely blocknthe lipolysis.