TRIGLYCERIDE-METABOLISM IN HUMAN KERATINOCYTES CULTURED AT THE AIR-LIQUID INTERFACE

Although epidermis reconstructed in vitro histologically demonstrates the presence of fully differentiated tissue with cornified strata, it does not synthesize or release epidermal barrier lipids in the same pr oportions as does native skin, causing the barrier function to be impa ired. Lipids, the content of which deviates the most, include triglyce rides that are present in high amounts and stored as lipid droplets. O ur recent studies have revealed that a high triglyceride content may b e a reflection of a high synthetic rate and a low turnover. Therefore, the present study was undertaken to examine whether the triglyceride accumulation in the air-exposed cultures may be a result of insufficie nt supplementation of cells with oxygen, an excessive supplementation of cells with glucose, dysregulation of lipogenesis, or an impaired ca tabolism of triglycerides caused either by insufficient activity of tr iglyceride lipase and/or accumulation of free fatty acids due to insuf ficient activity of beta-oxidase. When keratinocytes were cultured at the air-liquid interface in medium containing a standard glucose conce ntration, both the lactate and triglyceride production was high. Lower ing glucose content in the medium resulted in a decrease in both lacta te production and triglyceride synthesis. However, even when grown at a low glucose concentration the triglyceride content remained higher t han found in vivo and synthesized triglycerides were stored in the cel ls as a stable pool, suggesting that the catabolism of triglycerides w as impaired. Since both lipase and beta-oxidase were found to be activ e in cultured keratinocytes, another factor or other factors are proba bly implicated in the regulation of triglyceride metabolism.