Insight into the mechanism of lipids binding and uptake by CD36 receptor

Cluster-determinant 36 (CD36) mediates intestinal absorption of dietary astaxanthin and affects its secretion

The functional activity of dietary astaxanthin is closely related to its absorption, and the absorption of dietary carotenoids mainly mediated by transmembrane transport protein (TTP) has become the mainstream research direction in recent years. However, the main TTP mediating astaxanthin absorption and its potential mechanisms are still unclear. Hence, based on the preliminary screening results, this study aims to elucidate the role of cluster-determinant 36 (CD36) mediating astaxanthin absorption from the perspective of expression levels through in vitro cell model, in situ single-pass intestinal perfusion model and in vivo mice model. The results showed that astaxanthin uptake was significantly increased by 45.13% in CD36 overexpressing cells and decreased by 20.92% in the case of sulfo-N-succinimidyl oleate (SSO) inhibition. A similar trend also appeared in the duodenum and jejunum by in situ model. Moreover, astaxanthin uptake in the small intestine of CD36 knockout mice was significantly reduced by 88.22%. Furthermore, the inhibition or knockout of CD36 suppressed the expression of other transporters (SR-BI and NPC1L1). Interestingly, CD36 was also involved in the downstream secretion pathway, which is manifested by interfering with the expression of related proteins (ERK1/2, MTP, ApoB48, and ApoAI). Therefore, these results indicate the important role of CD36 in astaxanthin transmembrane transport for the first time, providing vital exploration way for the absorption of dietary fat-soluble substances.

Influence of cellular lipid content on influenza A virus replication

Influenza A virus (IAV) depends on the metabolism of its cellular host to provide energy and essential factors, including lipids, for viral replication. Previous studies have shown that fatty acids (FAs) play an important role in IAV replication and that inhibition of FA biosynthesis can diminish viral replication. However, cellular lipids can either be synthesized intracellularly or be imported from the extracellular environment. Interfering with FA import mechanisms may reduce the cellular lipid content and inhibit IAV replication. To test this hypothesis, MDCK and Detroit 562 cells were infected with IAV followed by exposure to palmitic acid and inhibitors of FA import. Replication of IAV significantly increased when infected cells were supplied with palmitic acid. This enhancement could be reduced by adding an FA import inhibitor. The addition of palmitic acid significantly increased the cellular lipid content, and this increased level was reduced by treatment with an FA import inhibitor. These results show that reducing the cellular lipid level might be an approach for IAV therapy.