Stevioside Promotes Lutein’S Bioavailability And Its Protective Mechanism Of Oxidative Damage

As an isoprene compound,lutein has multiple conjugated double bonds which are extremely unstable and prone to isomerization,oxidation,and degradation.At the same time,the high hydrophobicity of lutein seriously affects its absorption and bioavailability in the human body.The construction of nano-scale steady-state transport carriers to transport hydrophobic substances is a hot research topic.Our previous work has confirmed that stevioside can form a self-assembled nano-inclusion compound with lutein and significantly promote the solubility and bioavailability of lutein.The specific transmembrane transport mechanism and effective biological functions are not clear.In this study,the in vitro digestion model,Caco-2 cell model,and animal experiments were used to investigate the effects of stevioside embedding on lutein bioavailability and transmembrane transport characteristics;secondly,the oxidative damage model of retinal pigment epithelial cells induced by exogenous administration of hydrogen peroxide was used to study the effect of LUT-STE on the antioxidant activity and its mechanism.The main research conclusions are as follows:1.The bioaccessibility and apparent permeability coefficient of LUT-STE was measured by the in vitro digestion model and the Caco-2 cell monolayer model,and it was found that the stevioside embedding can promote the bioavailability and transmembrane absorption of lutein.After the stevioside were embedded,the bioavailability of lutein increased by 6.71 times,which was 4.42 times higher than that of LM.The cumulative transmembrane absorption of LUT-STE was 2.38 times that of lutein within 2 h.After treatment with EIPA,nystain,and dynasore inhibitors,nystain and dynasore significantly reduced the cell uptake of LUT-STE by 41.3%and 57.7%(compared with the blank group),and the cell uptake of LUT-STE was significantly lower than LUT group.The expression of transporter protein was further determined.The expression levels of CD36,NPC1L1,and PPARy protein in cells treated with LUT-STE were significantly higher than those in the blank group,and the expression levels of PPARγ protein were significantly higher than those in the LUT group,and the expression levels of CD36 and NPC1L1 proteins were higher than those in the LUT group,but there was no significant difference.2.To study the effects of stevioside embedding on lutein bioavailability and in vivo distribution through single feeding of mice LUT and LUT-STE.Stevioside embedding promoted the bioavailability of lutein.The lutein content in the plasma of the mice fed lut-ste was 1.6 times higher than that of LUT.After a single feeding of LUT-STE,the total amount of lutein in all tissues and organs of mice increased by 0.2 to 0.6 times,and mainly in the liver and spleen.The expression of related transporters in the small intestine of mice showed that the expression levels of CD36,NPC1L1,and PPARy protein in LUT-STE treated mice were significantly higher than those in the control group,and there was no significant difference from the LUT group.3.Exploring the antioxidant mechanism of LUT-STE by exogenously administering H2O2 to induce oxidative damage in ARPE cells as a disease model.ARPE cells induced with 800 μM H2O2 significantly reduced cell viability,increased ROS levels,and promoted apoptosis;Pretreatment of ARPE cells with 5 μg/mL LUT-STE significantly increased the content of SOD,CAT and GPx in the cells,reduced the content of ROS and MDA in the cells,and inhibited the expression of caspase-9 protein and caspase-3 activation.It inhibited the expression of p53 protein,as well as up-regulated Bcl-2/Bax,thereby inhibiting H2O2-induced apoptosis and improved cell viability.In addition,LUT-STE could inhibit the production of extracellular VEGF and reduce the over-expression of VEGF.