Metabolism

The metabolic area centres on peptides that act on receptors involved in the processing of sugars and fats in cells, such as the receptors for GLP-1, GIP and glucagon. Many of these compounds are derived from gut hormones or from other endogenous signalling molecules. Researchers study in cell and animal models how these receptors cooperate and which signalling pathways inside the cell they switch on.

Beyond the individual receptors, this area looks at how several signals together shape the energy balance of a cell. The glucagon receptor, which a molecule such as Retatrutide also engages, is involved in liver cell models in releasing stored energy. In this way the research shifts from single receptors toward networks of signals that set the balance between storage and use at the cellular level.

Incretin receptors and multi-agonists

Incretins are gut hormones released after a meal that bind to receptors on, among others, the beta cells of the pancreas. One line of research concerns molecules that engage several of these receptors at once. Retatrutide is studied as a molecule that activates three receptors: those for GLP-1, GIP and glucagon. In receptor binding assays and cell models, researchers measure how combining these points of action changes signalling through cAMP and related pathways.

The growth hormone axis and metabolic signals

Alongside the incretins, other pathways are studied. Tesamorelin is a stabilised GHRH analogue that engages growth hormone release in pituitary models and is studied in relation to lipid metabolism at tissue level. AOD-9604 is a fragment derived from the growth hormone molecule and is investigated in fat cell cultures for lipolysis signals. Together these examples show how different hormonal systems are involved in energy balance in models.

Half-life and molecular design

An important difference between these compounds lies not in the receptor but in how long they stay intact. Natural incretins are broken down within minutes by the enzyme DPP-4. In the laboratory, peptides are therefore given modifications, such as an attached fatty acid chain or substituted amino acids, that make the molecule more stable. This molecular design is one reason why modern research peptides show a very different time course in experiments than the gut hormones they are derived from.