Journal of Associated Medical Sciences (Oct 2018)
Different effects of palmitic and oleic acid on LPS induced nitric oxide production and its association with intracellular lipid accumulation
Abstract
Background: Total free fatty acids (FFAs) levels were elevated in blood circulation of obese, T2DM as well as patients with cardiovascular events. Among structural differences of FFAs found in plasma, almost 60% were palmitic acid (PA) and oleic acid (OA). In previous vitro studies, PA was the most potent lipotoxin that caused apoptosis in various cells. On the other hand, OA tended to be stored as non-toxic neutral lipid droplets inside the cells. These indicated that different structures of fatty acids had different effects in cellular metabolism. Thus, this study aimed to characterize ability of palmitic acid and oleic acid in mitigating lipopolysaccharide (LPS) induced inflammation in macrophages and to investigate how lipid droplets (LD) loaded macrophages responded to LPS. Materials and Methods: RAW 264.7 macrophages cytotoxicity of PA and OA after a two-day incubation were analyzed by MTT assay. The ability of inflammatory protection was investigated by incubating the cells with non-toxic concentration of fatty acids for 24 hr and followed by incubating the cells with 0.5 μg/mL LPS for another 24 hr. Cell supernatants were collected and nitric oxide concentrations were assayed by griess reaction. Lipid droplets formation was assessed by determining cellular triglyceride and neutral lipid oil red O staining. Results: PA showed higher lipotoxic activity compared to oleic acid at the same concentration. OA at 200 μM mitigated LPS induced nitric oxide production in parallel with LD accumulation in macrophages, whilst PA at its non-toxic concentration (50μM) was unable to diminish inflammation and did not alter lipid accumulation. Conclusion: Lipid loaded macrophages mediated by OA mitigated LPS induced inflammation. The association between anti-inflammation and LD formation should be further investigated.
