Effects of emulsifier charge and concentration on pancreatic lipolysis: 2. Interplay of emulsifiers and biles.
As a direct continuation of the first part of our in vitro study (Vinarov et al., Langmuir 2012, 28, 8127), here we investigate the effects of emulsifier type and concentration on the degree of triglyceride lipolysis, in the presence of bile salts. Three types of surfactants are tested as emulsifiers: anionic, nonionic, and cationic. For all systems, we observe three regions in the dependence degree of fat lipolysis, α, versus emulsifier-to-bile ratio, f(s): α is around 0.5 in Region 1 (f(s) < 0.02); α passes through a maximum close to 1 in Region 2 (0.02 < f(s) < f(TR)); α is around zero in Region 3 (f(s) > f(TR)). The threshold ratio for complete inhibition of lipolysis, f(TR), is around 0.4 for the nonionic, 1.5 for the cationic, and 7.5 for the anionic surfactants. Measurements of interfacial tensions and optical observations revealed the following: In Region 1, the emulsifier molecules are solubilized in the bile micelles, and the adsorption layer is dominated by bile molecules. In Region 2, mixed surfactant-bile micelles are formed, with high solubilization capacity for the products of triglyceride lipolysis; rapid solubilization of these products leads to complete lipolysis. In Region 3, the emulsifier molecules prevail in the adsorption layer and completely block the lipolysis.
Department of Chemical Engineering, Faculty of Chemistry and Pharmacy, Sofia University, Sofia, Bulgaria.
Zahari
Z
Vinarov
Slavka
S
Tcholakova
Borislava
B
Damyanova
Yasen
Y
Atanasov
Nikolai D
ND
Denkov
Simeon D
SD
Stoyanov
Edward
E
Pelan
Alex
A
Lips
D000818:Animals; D001647:Bile Acids and Salts / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D045703:Emulsifying Agents / Q000737:chemistry* / Q000494:pharmacology*; D006868:Hydrolysis / Q000187:drug effects; D057927:Hydrophobic and Hydrophilic Interactions; D007700:Kinetics; D008049:Lipase / Q000378:metabolism; D008066:Lipolysis / Q000187:drug effects*; D008970:Molecular Weight; D010179:Pancreas / Q000201:enzymology / Q000378:metabolism*; D013499:Surface Properties; D013552:Swine; D014280:Triglycerides / Q000378:metabolism
D001647:Bile Acids and Salts; D045703:Emulsifying Agents; D014280:Triglycerides; D008049:Lipase