Effect of Lampaya medicinalis Phil. (Verbenaceae) and Palmitic Acid on Insulin Signaling and Inflammatory Marker Expression in Human Adipocytes
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2024
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Background: Aging and obesity are associated with insulin resistance (IR) and low-gradeinflammation. Molecularly, IR is characterized by a reduction in glucose uptake and insulin signaling(IRS-1/Akt/AS160 pathway), while inflammation may result from upregulated NF-κB pathwayafter low Tyr-IκBαphosphorylation. Upregulated phosphatase activity of PTP1B is associated withimpaired insulin signaling and increased inflammation. Plasma levels of palmitic acid (PA) areelevated in obesity, triggering inflammation and disruption of insulin signaling. Traditional medicinein Northern Chile uses oral infusions ofLampaya medicinalisPhil. (Verbenaceae) to treat inflammatoryconditions. Significant amounts of flavonoids are found in the hydroethanolic extract of Lampaya(HEL), which may account for its biological activity. The aim of this work was to study the effect ofHEL and PA on insulin signaling and glucose uptake as well as inflammatory marker expression inhuman adipocytes. Methods: We studied HEL effects on PA-induced impairment on insulin signaling,glucose uptake and inflammatory marker content in human SW872 adipocytes. HEL cytotoxicity wasassessed in adipocytes at different concentrations (0.01 to 10 g/mL). Adipocytes were incubated or notwith PA (0.4 mM, 24 h) with or without HEL (2 h pre-incubation), and then stimulated with insulin(10 min, 100 mM) or a vehicle. Phospho-IRS-1, phospho-Akt, phospho-AS160, phospho-NF-κB andphospho-IκBα, as well as protein levels of PTP1B, were assessed using Western blotting, and glucoseuptake was evaluated using the 2-NBDG analogue. Results: At the assessed HEL concentrations, nocytotoxic effects were observed. PA decreased insulin-stimulated phospho-Akt and glucose uptake,while co-treatment with HEL increased such markers. PA decreased phospho-IRS-1 and phospho-Tyr-IκBα. On the other hand, incubation with HEL+PA decreased phospho-AS160 and phospho-NF-κBcompared with cells treated with PA alone. Conclusion: Our results suggest a beneficial effect ofHEL by improving PA-induced impairment on molecular markers of insulin signaling, glucoseuptake and inflammation in adipocytes. Further studies are necessary to elucidate whether lampayamay constitute a preventive strategy for people whose circulating PA levels contribute to IR andinflammation during aging and obesity.