Objective

To examine whether Caulerpa okamurae ethanolic extract (COE) could inhibit obesity-mediated inflammation, improve glucose metabolism and increases insulin sensitivity, using in vitro cell models of RAW 264.7 macrophages and 3T3-L1 adipocytes. 

Methods

We cocultured 3T3-L1 adipocytes in direct contact with lipopolysaccharide-stimulated RAW 264.7 macrophages and induced insulin resistance in 3T3-L1 adipocytes with tumor necrosis factor-α (TNF-α) in the presence or absence of 250 μg/mL of COE. We investigated various markers of inflammation, glucose regulation and insulin sensitivity in these models using Griess reagent to measure nitric oxide (NO) production, 2-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl) amino]-2-deoxyglucose to measure glucose uptake, Western blot analysis to quantify protein expression and reverse transcriptase-polymerase chain reaction to evaluate mRNA expression.

Results

We found that COE (250 μg/mL) significantly inhibited the lipopolysaccharide-induced inflammatory response in RAW 264.7 macrophages by downregulating NO production, nitric oxide synthase 2 expression and nuclear translocation of nuclear factor-κB. COE also showed similar anti-inflammatory activity in coculture, along with decreased TNF-α, interleukin-6 and monocyte chemoattractant protein mRNA expression. In addition, COE also improved glucose uptake in coculture by upregulating glucose transporter-4 (GLUT-4) and adiponectin and reducing serine phosphorylation of insulin receptor substrate-1 (IRS1). In the TNF-α-induced insulin resistance model of 3T3-L1 adipocytes, COE significantly improved both basal and insulin-stimulated glucose uptake, accompanied by phosphorylation of IRS1 at tyrosine 632, phospho-5' adenosine monophosphate-activated protein kinase α and glycogen synthase kinase-3β (Ser9) as well as upregulation of GLUT-4.

Conclusion

Together, these findings suggest that COE has potential to treat or prevent obesity-induced metabolic disorders.

Key words: Caulerpa okamurae, , RAW 264.7 macrophages, 3T3-L1 adipocytes, Coculture, Metabolic disorder