Scientists Engineer Improved Versions of the Appetite-Suppressing Peptide PYY for Obesity Treatment

What the researchers found

Using an intein-based expression system combined with parallel solid-phase synthesis, researchers generated an array of C-terminally modified PYY(3-36) analogues with substitutions at positions Arg33, Gln34, Arg35, and Tyr36.

Key findings from functional Y2 receptor assays:

- Substitutions at Tyr36 were generally better tolerated than modifications at Arg33, Gln34, or Arg35

- Arg33, Gln34, and Arg35 were critical for Y2 receptor activation

- Two analogues showed significantly improved Y2 receptor selectivity compared to native PYY(3-36)

- These results provide a foundation for designing new PYY-based obesity drug candidates with improved receptor selectivity

Why it matters

PYY(3-36) is a natural appetite suppressant that has shown promise in obesity research but hasn't yet become a successful drug partly due to receptor selectivity issues. By systematically engineering the peptide's critical C-terminal region, this work identified improved analogues that could eventually lead to more effective PYY-based obesity medications with fewer side effects.

How the study worked

Researchers used an intein-based expression system in E. coli to produce PYY(3-29) as a C-terminal peptide α-thioester. Heptapeptides with an N-terminal cysteine and C-terminal modifications were synthesized in parallel using 96-well plate solid-phase synthesis. The fragments were joined by native chemical ligation, followed by desulfurization and solid-phase extraction. The resulting analogues were tested in a functional Y2 receptor assay.

What this study cannot tell us

This was an in vitro study focused on receptor binding and selectivity, with no animal or human testing. Improved Y2 selectivity in a receptor assay does not guarantee improved efficacy or safety in vivo. Pharmacokinetic properties like metabolic stability and bioavailability of the analogues were not assessed. The semi-synthetic approach, while efficient, is limited to modifications at the C-terminal end.

How to read the evidence

This is a preclinical peptide chemistry study focused on structure-activity relationships and in vitro receptor assays. No animal or human testing was conducted, placing it at an early discovery stage.

When this study was published

Published in 2013, this represents foundational peptide engineering work. PYY-based therapies have not yet reached the market, though interest in multi-peptide approaches for obesity continues.

The bigger picture

While GLP-1 receptor agonists have dominated obesity drug development, PYY remains an important target because it works through a different receptor system (Y2) and pathway. Combination approaches using multiple gut peptide pathways — as seen with dual and triple agonists — could eventually incorporate PYY analogues to achieve greater weight loss with complementary mechanisms of action.

Questions still open

• Do the two improved PYY analogues retain their appetite-suppressing effects and Y2 selectivity in animal models?
• Could PYY-based drugs be combined with GLP-1 agonists for enhanced obesity treatment?
• What modifications would be needed to make PYY analogues suitable for oral or long-acting formulations?

Common questions

Read the original research

A parallel semisynthetic approach for structure-activity relationship studies of peptide YY.

ChemMedChem, 8(9), 1505-13, 1422

Citation

Albertsen, Louise; Østergaard, Søren; Paulsson, Johan F; Norrild, Jens Chr; Strømgaard, Kristian. (2013). A parallel semisynthetic approach for structure-activity relationship studies of peptide YY.. ChemMedChem, 8(9), 1505-13, 1422. https://doi.org/10.1002/cmdc.201300290