(G-274) Thermogenic Modulation in Adipocytes Using Lipid Coated-Mesoporous Silica Nanoparticles

Introduction:: Obesity and its affiliated comorbidities are increasing worldwide and continue being a significant burden to the U.S. economy. Increasing thermogenic adipose tissue can enhance the overall energy expenditure of the body and may serve as a treatment for obesity. Forskolin, a poor water-soluble compound, is a cyclic AMP activator and can stimulate lipolysis in adipocytes. A more efficient delivery system for forskolin would increase its efficacy. Lipid coated mesoporous silica nanoparticles (aka protocells) have been shown to be a versatile vehicle to deliver small molecules to various tissues. In this study we developed a local drug delivery strategy that is retained in the adipose tissue and is capable of delivering forskolin to adipose tissue cells with the goal of increasing thermogenic activity.


Materials and Methods:: Mesoporous silica nanoparticles (MSNPs) were synthesized using a solution-based surfactant directed self-assembly method. Liposomes were fused to MSNPs through electrostatic interactions. Human adipose stem cells (hASCs) were differentiated to mature adipocytes and were treated with protocells to examine its effect on thermogenic activity. CellTiter-Glo Luminescent cell viability assay (Promega) was used to analyze the cytotoxicity of different concentrations of protocells in mature adipocytes in vitro. Fluorescently labeled MSNPs were added to mature adipocytes for 3h, 6h, 24h, and 48h, and cellular uptake was analyzed using flow cytometry. To test the thermogenic modulation effect of the nanoparticles treatment in vitro, Forskolin loaded protocells (PF) were used, with protocells and Forskolin alone as controls. Cellular UCP1 expression and other thermogenic gene markers were quantified using RT-PCR. Glucose uptake (Promega) and lipolytic function (Sigma) were also tested. In vivo studies were performed by injecting the fluorescently labeled, forskolin loaded and unloaded, protocells in the inguinal white adipose tissue in C57BL/6J mice. The animals were imaged using a non-invasive near-infrared optical imagining system to analyze for in vivo biodistribution at 3h, 6h, 24h, and 48h timepoints. At the selected timepoints, animals were sacrificed, and their inguinal white adipose tissues were extracted. The thermogenic gene markers’ expression in isolated fat were quantified. Functional lipolysis was assessed in the tissue were using a lipolysis kit (Sigma).

Results, Conclusions, and Discussions:: We observed no cytotoxic effects when differentiated adipocytes were treated with the protocells at concentrations between 0 µg/mL to 1000 µg/mL of media. Flow cytometry data confirmed that there was an increased nanoparticle uptake over time, up to 92.5% cellular uptake at 24 hours. Cells treated with PF also demonstrated a significant increase in glucose uptake and lipolysis at 3h, 6h, and 24h. Furthermore, at 3h and 6h, UCP1 expression was significantly increased in cells treated with PF when compared to the other two treatment groups, with the highest increase at 6 hour of PF treatment. In vivo, biodistribution studies showed protocell retention in adipose tissue until 48h. A significant increase in inguinal white adipose tissue lipolysis function was observed post 3-, 6-, and 24-hour injection. The UCP1 gene levels were highest at 6-hours post injection and had a greater than four-thousand-fold increase when compared to control. Forskolin loaded protocells can significantly increase the thermogenic capacity in adipose tissue.

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