Self-nanoemulsifying drug delivery systems (SNEDDS) successfully delivered the GLP-1 peptide exendin-4 to pancreatic beta cells, increasing insulin secretion over 2-fold while protecting the peptide from digestive degradation.
2.21-fold insulin increaseSNEDDS-delivered exendin-4 more than doubled insulin secretion from pancreatic beta cells at low glucose concentrations, while achieving deeper intracellular penetration (nuclear vs. cytoplasmic) than free peptide.
What the researchers found
Exendin-4 loaded in SNEDDS and exendin-4/chymostatin SNEDDS (with an enzyme inhibitor for additional protection) were tested on INS-1E rat pancreatic beta cells:
- At low glucose (2.8 mM): Ex-4 SNEDDS increased insulin levels 2.21-fold and ex-4/chym SNEDDS increased them 2.17-fold compared to control
- At high glucose (16.7 mM): Both formulations also increased insulin levels compared to control
- Cell viability increased at higher dilution ratios, indicating safety at appropriate concentrations
- Cellular uptake studies showed SNEDDS delivered cargo to cell nuclei (visualized with coumarin-6), while free solution only reached the cell cytoplasm — demonstrating superior intracellular delivery
Why it matters
Converting injectable peptide drugs to oral forms remains a major pharmaceutical challenge. Exendin-4 (marketed as exenatide/Byetta) must be injected twice daily, limiting patient compliance. SNEDDS offer several practical advantages: they protect peptides from stomach acid and enzymes, are simple to manufacture at scale, and reduce food-related absorption variability. The demonstration of enhanced intracellular delivery (reaching the nucleus vs. just the cytoplasm) is particularly significant and could improve the biological effectiveness of orally delivered peptides.
How the study worked
Researchers formulated exendin-4 and exendin-4/chymostatin in self-nanoemulsifying drug delivery systems. Cytotoxicity was assessed via cell viability assays on INS-1E rat pancreatic beta cells at various dilution ratios. Insulin secretion was measured after incubating cells with the formulations at low (2.8 mM) and high (16.7 mM) glucose concentrations. Cellular uptake was visualized using fluorescent coumarin-6-loaded SNEDDS and confocal microscopy, comparing intracellular distribution of SNEDDS-delivered versus free coumarin-6.
What this study cannot tell us
All experiments were conducted in vitro using a rat beta cell line (INS-1E), which may not represent human pancreatic beta cell behavior. No in vivo oral bioavailability data was generated — the critical test of whether SNEDDS can deliver exendin-4 through the actual gut environment. The chymostatin enzyme inhibitor adds complexity and potential safety concerns for human use. Specific insulin secretion values at high glucose concentrations were not clearly stated in the abstract. Long-term stability of the exendin-4 SNEDDS formulation was not characterized.
How to read the evidence
This is an early-stage in vitro pharmaceutical formulation study using a cell line model. While the cellular uptake and insulin secretion data are promising, the absence of in vivo oral bioavailability testing limits the translational significance. This represents proof-of-concept at the cell culture stage.
When this study was published
Published in 2024, this is a recent study in the active field of oral peptide drug delivery. SNEDDS technology continues to be explored for various peptide therapeutics.
The bigger picture
This study contributes to the broader effort of enabling oral peptide drug delivery — a challenge relevant to the entire $50+ billion peptide therapeutics market. While oral semaglutide (Rybelsus) uses a different absorption enhancer approach, SNEDDS represent an alternative platform with potential advantages in manufacturing simplicity and scalability. The finding that SNEDDS achieve deeper intracellular penetration than free peptide solutions could be applicable to many other peptide drugs beyond exendin-4.
Questions still open
- Does SNEDDS-delivered exendin-4 achieve therapeutic oral bioavailability in animal models?
- How does SNEDDS oral exendin-4 bioavailability compare to the existing oral semaglutide (Rybelsus) approach?
- Could this SNEDDS platform be adapted for other peptide drugs like insulin, GLP-1 analogs, or antimicrobial peptides?
Common questions
What is a SNEDDS and how could it help with oral peptide drugs?
Why does deeper cell penetration matter for drug delivery?
Read the original research
In vitro cellular uptake and insulin secretion studies on INS-1E cells of exendin-4-loaded self-nanoemulsifying drug delivery systems.
Pharmaceutical development and technology, 29(10), 1101-1110
Citation
Çelik Tekeli, Merve; Yalçın, Yaprak; Verdi, Hasibe; Aktaş, Yeşim; Çelebi, Nevin. (2024). In vitro cellular uptake and insulin secretion studies on INS-1E cells of exendin-4-loaded self-nanoemulsifying drug delivery systems.. Pharmaceutical development and technology, 29(10), 1101-1110. https://doi.org/10.1080/10837450.2024.2423823