Anti-inflammatory Effects of Fatty Acid Esters of Hydroxy Fatty Acids (FAHFAs) In Vitro and In Vivo

Abstract

Obesity is characterized by low-grade chronic inflammation that contributes to the development of metabolic diseases that include insulin resistance and cardiac diseases. Due to its high prevalence and comorbidities, obesity has been accorded a lot of attention to develop novel intervention strategies to prevent obesity-induced inflammation. The recent, discovery of a novel class of endogenous lipids named fatty acid esters of hydroxy fatty acids (FAHFAs) which exert anti-diabetic and anti-inflammatory effects has become a potential avenue against combating obesity associated diseases. In this research, we examined the ability of FAHFAs in mitigating lipopolysaccharide (LPS)-induced inflammation in macrophages and low-grade inflammation under obese states. In vitro cell culture experiments showed that palmitic-acid-9-hydroxy-stearic-acid (9-PAHSA) and oleic-acid-12-hydroxy-stearic-acid (12-OAHSA) significantly inhibited LPS-induced cytotoxicity in RAW 264.7 cells. In addition, 9-PAHSA and 12-OAHSA suppressed LPS-induced inflammatory responses in macrophages through decreasing the expression of inflammatory genes. Exploration of 12-OAHSA effects on the nuclear factor kappa-light-chain-enhancer of activated B-cells (NF-κB) signaling pathway demonstrated that it reduced phosphorylation of the inhibitor of nuclear factor kappa-B kinase subunit beta (Ikkβ) and NF-κB subunit p65 (p65) while increasing total cytosolic nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor alpha (IkBα). These results collectively indicated that 12-OAHSA could have downregulated the expression of pro-inflammatory genes through this modus operandi in macrophages. In vivo experiments revealed that the administration of 12-OAHSA to the obese mice model significantly reduced blood glucose levels and insulin resistance compared to the vehicle treated group. 12-OAHSA treated mice also displayed significantly decreased accumulation of CD11c+ macrophages, CD4+ and CD8+ T lymphocytes in epididymal white adipose tissue (eWAT). Interestingly, 12-OAHSA effects on reducing immune cell populations in eWAT were abolished in blood and spleen indicating that its effects might be tissue specific. Further exploration of genes expression in eWAT of 12-OAHSA treated obese mice showed a reduction of interferon gamma (Ifng) expression as a pro-inflammatory gene and an increase in the expression of an anti-inflammatory gene, interleukin 10 (Il-10). An examination of the NF-κB signaling pathway in eWAT showed reductions in phosphorylation of the Ikkβ and the degradation of the IkBα which were indicative of improved inflammatory states. Combined, these results indicated that 12-OAHSA mitigates obesity-induced insulin resistance by regulation of adipose tissue inflammation. Therefore, 12-OAHSA can be a novel bioactive compound that is capable of having anti-inflammatory effects and might be used as a new nutritional bioactive compound for the intervention of obesity-associated low-grade inflammation and obesity related diseases.