Omega-3 polyunsaturated fatty acids suppress the inflammatory responses of lipopolysaccharide-stimulated mouse microglia by activating SIRT1 pathways.

Obesity and diabetes are known risk factors for dementia, and it is speculated that chronic neuroinflammation contributes to this increased risk. Microglia are brain-resident immune cells modulating the neuroinflammatory state. Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), the major ω-3 polyunsaturated fatty acids (PUFAs) of fish oil, exhibit various effects, which include shifting microglia to the anti-inflammatory phenotype. To identify the molecular mechanisms involved, we examined the impact of EPA, DHA, and EPA+DHA on the lipopolysaccharide (LPS)-induced cytokine profiles and the associated signaling pathways in the mouse microglial line MG6. Both EPA and DHA suppressed the production of the pro-inflammatory cytokines TNF-α and IL-6 by LPS-stimulated MG6 cells, and this was also observed in LPS-stimulated BV-2 cells, the other microglial line. Moreover, the EPA+DHA mixture activated SIRT1 signaling by enhancing mRNA level of nicotinamide phosphoribosyltransferase (NAMPT), cellular NAD+ level, SIRT1 protein deacetylase activity, and SIRT1 mRNA levels in LPS-stimulated MG6. EPA+DHA also inhibited phosphorylation of the stress-associated transcription factor NF-κB subunit p65 at Ser536, which is known to enhance NF-κB nuclear translocation and transcriptional activity, including cytokine gene activation. Further, EPA+DHA increased the LC3-II/LC3-I ratio, an indicator of autophagy. Suppression of TNF-α and IL-6 production, inhibition of p65 phosphorylation, and autophagy induction were abrogated by a SIRT1 inhibitor. On the other hand, NAMPT inhibition reversed TNF-α suppression but not IL-6 suppression. Accordingly, these ω-3 PUFAs may suppress neuroinflammation through SIRT1-mediated inhibition of the microglial NF-κB stress response and ensue pro-inflammatory cytokine release, which is implicated in NAMPT-related and -unrelated pathways.

Blockade of visfatin induction by oleanolic acid via disturbing IL-6-TRAF6-NF-κB signaling of adipocytes.

Oleanolic acid is a pentacyclic triterpenoid naturally present in foods and medicinal plants with anticancer, antioxidant, and antiaging properties. The current study elucidated that oleanolic acid inhibited the production of insulin-mimetic and inflammatory adipokine of visfatin during adipogenic differentiation of 3T3-L1 adipocytes. Adipocytes were cultured in an adipogenic media with and without 1-25 µM oleanolic acid up to 8 days for differentiation. The cellular expression and secretion of visfatin was markedly enhanced in differentiating adipocytes, which was dose-dependently attenuated by 1-25 µM oleanolic acid. Secretion of interleukin (IL)-6 and macrophage inflammatory protein (MIP)-2 was highly elevated during differentiation, which was much earlier than visfatin production of adipocytes. The visfatin production was secondary to inflammatory IL-6 and MIP-2. This study further elucidated that nuclear factor-κB (NF-κB) signaling was responsible for cellular production of visfatin. NF-κB was activated by translocating into the nucleus with increased phosphorylation of inhibitory κB (IκB), which was disturbed by oleanolic acid. Cellular expression of tumor necrosis factor receptor associated factor 6 (TRAF6), a NF-κB upstream, was upregulated in parallel with transactivation with NF-κB. The TRAF6 induction required the auto-stimulation of inflammatory IL-6 and MIP-2. These results demonstrate that oleanolic acid inhibited visfatin and its inflammatory response during adipocyte differentiation through blocking IL-6-TRAF6-NF-κB signaling. Therefore, oleanolic acid may be a potent therapeutic agent targeting against adipogenesis and visfatin-linked inflammation.

Oleanolic acid reduces markers of differentiation in 3T3-L1 adipocytes.

Oleanolic acid is a triterpenoid compound that is widely present in vegetables, medicinal herbs, and other plants and has potent antioxidant and antiinflammatory properties. However, the potential of oleanolic acid to offset obesity is not clear. This study tested the hypothesis that oleanolic acid suppresses the differentiation of 3T3-L1 adipocytes by downregulating cellular induction of peroxisome proliferators-activated receptor γ (PPARγ) and cytidine-cytidine-adenosine-adenosine-thymidine (CCAAT) enhancer binding protein α (C/EBPα). The 3T3-L1 adipocytes were cultured and differentiated in Dulbecco modified Eagle medium containing 10% fetal bovine serum for 6 to 8 days in the absence and presence of 1 to 25 µmol/L oleanolic acid according to differentiating protocols. Nontoxic oleanolic acid, at 25 µmol/L or less, dose-dependently attenuated lipid accumulation in differentiated adipocytes as evidenced by Oil Red O staining. Western blot analysis showed that the induction of PPARγ and C/EBPα was markedly attenuated in differentiated and oleanolic acid-treated adipocytes at their transcriptional messenger RNA levels. Furthermore, this study examined whether oleanolic acid dampened the induction of visfatin, a proinflammatory and visceral fat-specific adipokine expressed in adipocytes. Visfatin expression was inhibited in differentiated adipocytes exposed to a PPARγ inhibitor GW9662. In addition, the visfatin production was significantly repressed in 25 µmol/L oleanolic acid-treated adipocytes, possibly through blocking PPARγ activation. These results demonstrate that oleanolic acid may be a promising agent to disturb adipocyte differentiation and suppress obesity-associated inflammation.

[Advances of the mechanism study on berberine in the control of blood glucose and lipid as well as metabolism disorders].

Berberine, an isoquinoline alkaloid isolated from some Chinese medicinal herbs such as Coptidis rhizoma, has been used for the treatment of diarrhea and other gastrointestinal infections as an antibacterial drug in Chinese medicine. In recent years, it was reported to have beneficial effects on the metabolism disorders states of diabetes. The mechanisms involve many aspects of the diabetes, including regulating the blood cholesterol and triglyceride, lowering blood glucose, ameliorating the insulin resistant state and influencing the function of the pancreatic beta cell.

Novel Danshen methoxybenzo[b]furan derivative antagonizing adipogenic differentiation and production of inflammatory adipokines.

Many benzo[b]furan lignans are known to be biologically active in nature. 2-(3'-Methoxy-4'-hydroxy-phenyl)-5-(3-hydroxypropyl)-7-methoxy-benzo[b]furan-3-carbaldehyde (XH-14) is found as a bioactive component isolated from the plant Salvia miltiorrhiza, commonly known as Danshen, which is a traditional Chinese medicine that is used as a cardiovascular medication. This study examined whether 3 different XH-14 derivatives can inhibit adipocyte differentiation and induction of the adipokines visfatin and resistin in 3T3-L1 adipocytes. Adipocytes were cultured and differentiated in Dulbecco's modified Eagle medium containing fetal bovine serum, 3-isobytyl-1-methylxanthine, dexamethasone, and insulin for 6-8d in the absence and presence of 1-25µM XH-14-derived benzo[b]furan derivatives. Nontoxic 2-(3'-methoxy-4'-hydroxy-phenyl)-6-(3-hydroxypropyl)-5-methoxy-benzo[b]furan (5-MBF) at ≥5µM attenuated cellular lipid accumulation and down-regulated induction of peroxisome proliferator activated receptors γ (PPARγ) and CCAAT enhancer binding protein α (C/EBPα) in a dose-dependent manner, as evidenced by Oil Red O staining and Western blot analysis. Such inhibition of PPAR( and C/EBP( by 5-MBF was achieved at transcriptional mRNA levels. However, 2-(3'-methoxy-4'-hydroxy-phenyl)-5-(3-hydroxypropyl)-7-methoxy-benzo[b]furan (7-MBF) and 2-(3'-methoxy-4'-hydroxy-phenyl)-5-(3-hydroxypropyl)-7-methoxy-benzo[b]furan (6-MBF) had minimal effects on adipogenic differentiation, suggesting a structure-activity relationship of methoxybenzo[b]furan derivatives as an inhibitor of adipogenic differentiation. Furthermore, ≥5µM 5-MBF retarded protein and mRNA expression of proinflammatory and insulin resistance-enhancing adipokines of visfatin and resistin in differentiated adipocytes. Induction of visfatin and resistin was, at least in part, mediated via adipocyte differentiation-associated activation of PPARγ signal targeting adipocyte protein 2 and stearoyl-CoA desaturase. These results demonstrate that the 2-(3'-methoxy-4'-hydroxy-phenyl)-3-hydroxypropyl benzo[b]furan lignan, with a methoxy group at the 5-position on the benzene ring, may be a promising agent for disturbance of adipogenic differentiation and for blockage of obesity-associated inflammatory and metabolic diseases.