Apod, also known as apolipoprotein D, is a 25-30 kDa glycosylated protein belonging to the lipocalin superfamily. It functions as a transporter of small hydrophobic molecules and is mainly associated with lipid metabolism, such as transporting arachidonic acid and modulating eicosanoid production. It also plays roles in neuroprotection, inflammation, antioxidative response, and is involved in different types of cancers [1].

In ApoD-/-mice, normal retinal sterol levels were observed, but there were changes in chorioretinal blood vessels and impaired retinal function. Whole-body glucose disposal was impaired, suggesting a role of Apod in retinal metabolism and glucose disposal [2]. In a study on osteoarthritis, APOD intervention on fibroblast-like synoviocyte and chondrocytes extracted from OA patients reversed gene expression changes, regulated cell proliferation, apoptosis, autophagy, and reduced oxidative stress, indicating its potential to delay OA progression [3].

In conclusion, Apod is a multi-functional protein with key roles in lipid metabolism, neuroprotection, and various disease-related processes. Studies using gene knockout mouse models, like ApoD-/-mice, have provided insights into its functions in retinal metabolism and glucose disposal. In addition, its potential in diseases like osteoarthritis shows its importance in disease-associated biological processes, contributing to our understanding of related disease mechanisms and potential therapeutic targets.

References:

1. Rassart, Eric, Desmarais, Frederik, Najyb, Ouafa, Bergeron, Karl-F, Mounier, Catherine. 2020. Apolipoprotein D. In Gene, 756, 144874. doi:10.1016/j.gene.2020.144874. https://pubmed.ncbi.nlm.nih.gov/32554047/

2. El-Darzi, Nicole, Mast, Natalia, Petrov, Alexey M, Bederman, Ilya, Pikuleva, Irina A. 2020. Studies of ApoD-/- and ApoD-/-ApoE-/- mice uncover the APOD significance for retinal metabolism, function, and status of chorioretinal blood vessels. In Cellular and molecular life sciences : CMLS, 78, 963-983. doi:10.1007/s00018-020-03546-3. https://pubmed.ncbi.nlm.nih.gov/32440710/

3. Xu, Wenbo, Gu, Shoubin, Zhang, Gang, Yan, Jinglong, Qin, Yong. 2023. APOD acts on fibroblast-like synoviocyte and chondrocyte to alleviate the process of osteoarthritis in vitro. In Journal of orthopaedic research : official publication of the Orthopaedic Research Society, 42, 296-305. doi:10.1002/jor.25690. https://pubmed.ncbi.nlm.nih.gov/37728985/