Tailoring thermal treatment to form liprotide complexes between oleic acid and different proteins

Nanocarriers System for Vitamin D as Nutraceutical in Type 2 Diabetes: A Review

Incidence of diabetes are common among population around the world. Diabetes may lead to other complication and increasing morbidity and mortality. Many ways have been done to treat and prevent the development of diabetes. In addition of conventional pharmacotherapy, therapeutic therapy shown good opportunity to maintain and improve diabetic conditions. Vitamin D3 is known as nutraceutical and has good opportunity to develop the medication of type 2 diabetes. In another way, vitamin D3 naturally easy to damage by environmental condition. To overcome this weakness, researcher around the world have developed the method for protecting unstable compound as vitamin D3 with encapsulation. Liprotide is one of the various materials which can be used for encapsulation. Combination of lipid and protein molecules is expected to be a carrier and protector of vitamin D3 in gastrointestinal system. Here we review the research advances of liprotide as nanocarriers and vitamin D3 as nutraceuticals to discuss in applied on type 2 diabetes.

Structures and mechanisms of formation of liprotides

Many proteins form complexes called liprotides with oleic acid and other cis-fatty acids under conditions where the protein is partially unfolded. The complexes vary in structure depending on the ratio of protein and lipid, but the most common structural organization is the core-shell structure, in which a layer of dynamic, partially unfolded and extended proteins surrounds a micelle-like fatty acid core. This structure, first reported for α-lactalbumin together with OA, resembles complexes formed between proteins and anionic surfactants like SDS. Liprotides first rose to fame through their anti-carcinogenic properties which still remains promising for topical applications though not yet implemented in the clinic. In addition, liprotides show potential in drug delivery thanks to the ability of the micelle core to solubilize and stabilize hydrophobic compounds, though applications are challenged by their sensitivity to acidic pH and dynamic exchange of lipids which makes them easy prey for serum "hoovers" such as albumin. However, liprotides are also of fundamental interest as a generic "protein complex structure", demonstrating the many and varied structural consequences of protein-lipid interactions. Here we provide an overview of the different types of liprotide complexes, ranging from quasi-native complexes via core-shell structures to multi-layer structures, and discuss the many conditions under which they form. Given the many variable types of complexes that can form, rigorous biophysical analysis (stoichiometry, shape and structure of the complexes) remains crucial for a complete understanding of the mechanisms of action of this fascinating group of protein-lipid complexes both in vitro and in vivo.

Liprotides assist in folding of outer membrane proteins

Proteins and lipids can form complexes called liprotides, in which the partially denatured protein forms a shell encasing a lipid core. This effectively stabilizes a lipid micelle in an aqueous solvent and suggests that liprotides may provide a suitable vessel for membrane proteins. Accordingly we have investigated if liprotides consisting of α-lactalbumin and oleate could aid folding of four different outer membrane proteins (OMPs) tOmpA, PagP, BamA, and OmpF. tOmpA was able to fold in the presence of the liprotide, and folding did not occur if only oleate or α-lactalbumin were added. Although the liprotides did not fold the other three OMPs on its own, it was able to assist their folding in the presence of vesicles. Incubation with liprotides before folding into vesicles increased the folding yield of the outer membrane proteins to a level higher than using micelles of the non-ionic surfactant DDM. Even though the liprotide was stable at both high urea concentrations and high pH, it failed to efficiently fold OmpA at high pH. Instead, optimal folding was seen at pH 8-9, suggesting that important changes in the liprotide occurred when increasing the pH. We conclude that an otherwise folding-inactive fatty acid can be activated when presented by a liprotide and thereby work as an in vitro chaperone for outer membrane proteins.