Complexes between linoleate and native or aggregated β-lactoglobulin: interaction parameters and in vitro cytotoxic...

Area of Science:

• Food Science
• Protein Chemistry
• Biochemistry

Background:

• Dairy protein beta-lactoglobulin (βlg) forms complexes with fatty acids (FA).
• Industrial food processing can alter the native structure of βlg, potentially modifying FA/βlg complex properties.
• Understanding these structural changes is crucial for food applications and bioavailability.

Purpose of the Study:

• To investigate the interaction of bovine βlg in different structural forms (native, dimer, nanoparticles) with linoleate (C18:2).
• To assess how structural modifications of βlg influence linoleate binding and its subsequent in vitro cytotoxicity.
• To explore the modulation of fatty acid cytotoxicity by altering protein aggregation states.

Main Methods:

• Utilized fluorescence spectroscopy and Isothermal Titration Calorimetry (ITC) to study βlg-linoleate binding.
• Quantified binding stoichiometry and association constants across different βlg structural states.
• Employed in vitro cytotoxicity assays using Caco-2 cells to measure the impact of linoleate uptake.

Main Results:

• Linoleate binds to βlg at two distinct sites, irrespective of the protein's structural form.
• While association constants were similar, βlg nanoparticles exhibited a 6-fold increase in linoleate binding stoichiometry compared to native βlg.
• In vitro cytotoxicity of linoleate decreased in the order: free > complexed to dimers > complexed to nanoparticles > complexed to native βlg.

Conclusions:

• The structural state of βlg significantly modulates its binding capacity for fatty acids like linoleate.
• Altering βlg aggregation, particularly forming nanoparticles, can decrease linoleate's in vitro cytotoxicity.
• These findings suggest that controlling protein structure in food processing can influence the biological activity of bound fatty acids.