Adipocyte and Cell Biology

Nanoparticle-mediated in vitro delivery of E4orf1 to preadipocytes is a clinically relevant delivery system to improve glucose uptake



Impaired glycemic control is a common comorbidity of obesity. E4orf1(E4), an adenovirus-derived protein, reduces the activity of insulin receptor substrate (IRS), yet activates Akt and promotes the membrane translocation of GLUT4, resulting in better glycemic control in mice. To develop a clinically suitable delivery system, here we constructed and tested liposome nanoparticles (NP), to deliver E4 to preadipocytes.


Glutathione-S-transferase (GST)-tagged E4 was encapsulated in Rhodamine-phosphatidylethanolamine (PE)-tagged soy-phosphatidylcholine-NP. The NP were characterized. Preadipocytes were treated with free E4, E4 containing NP (E4 NP) or E4-free NP (void NP).


For void and E4 NP, the average size was ~150 and 130 nm, PDI was ~0.25 and 0.27, and Zeta potential was −23 and −25, respectively. The average encapsulation efficiency (EE) was ~50%. Cells treated with E4 showed maximum GST expression and Rhodamine signals at 24 h. The presence of E4 in cells was confirmed at 24, 48, and 72 h. At 72 h after exposure, E4 NP significantly decreased pTyr-IRS, yet increased pAkt protein abundance, membrane translocation of GLUT4, and glucose uptake, compared with cells treated with void NP. Free E4 (without NP) had no effect.


NP-mediated delivery of E4 promotes glucose uptake in preadipocytes. The next step is to test the efficacy of this clinically compatible delivery approach in vivo.

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Fig. 1: Morphology of NP.
Fig. 2: NP are able to encapsulate E4 protein and deliver it to the cells.
Fig. 3: Encapsulated E4 downregulates proximal insulin signaling but upregulates distal insulin signaling in preadipocytes.
Fig. 4: E4 NP enhance cellular glucose uptake in preadipocytes.
Fig. 5: NP are stable and functional after one week of storage at 4 °C.


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We would like to thank Mary Catherine Hastert for assistance with the transmission electron microscopy and Dr Peter Keyel for his help with flow cytometry (both at Texas Tech University).

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Correspondence to Nikhil V. Dhurandhar.

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NVD has received several United States and international patents that protect intellectual property about the use of adenoviruses and E4 protein in obesity, diabetes, and related areas.

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Feizy, Z., Peddibhotla, S., Khan, S. et al. Nanoparticle-mediated in vitro delivery of E4orf1 to preadipocytes is a clinically relevant delivery system to improve glucose uptake. Int J Obes (2020).

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