preclinical (rodent) · PMID 19597507

A new glucagon and GLP-1 co-agonist eliminates obesity in rodents

2009 rodent study: a glucagon/GLP-1 co-agonist raised energy expenditure and cut body fat, an early case for adding glucagon agonism as retatrutide does.

Last updated · 2009 · Day, J.W., Ottaway, N., Patterson, J.T., Gelfanov, V., Smiley, D., Gidda, J., Findeisen, H., Bruemmer, D., Drucker, D.J., Chaudhary, N., Holland, J., Hembree, J., Abplanalp, W., Grant, E., Ruehl, J., Wilson, H., Kirchner, H., Lockie, S.H., Hofmann, S., Woods, S.C., Nogueiras, R., Pfluger, P.T., Perez-Tilve, D., DiMarchi, R., Tschöp, M.H. · Nature Chemical Biology

Key findings

A peptide acting on both glucagon and GLP-1 receptors had potent, sustained satiation-inducing and lipolytic effects
Once-weekly PEGylated co-agonists normalized adiposity and glucose tolerance in diet-induced obese mice
Weight loss came from body-fat loss driven by lower food intake and higher energy expenditure
Adding an appropriate degree of glucagon receptor activation to full GLP-1 agonism substantially enhanced fat loss without overt adverse effects in rodents

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Summary

This is a preclinical study in rodents, not a review or a human trial. Day and colleagues chemically modified glucagon to create peptides that activate both the glucagon and GLP-1 receptors, then tested them in rodent obesity models. Given once a week in PEGylated form, the co-agonists normalized adiposity and glucose tolerance in diet-induced obese mice. The weight lost was body fat, driven by both lower food intake and higher energy expenditure. The authors conclude that pairing full GLP-1 agonism with an appropriate degree of glucagon receptor activation can substantially enhance body-fat reduction without overt adverse effects in these models.

Key Findings

The co-agonist peptide had potent, sustained satiation-inducing (appetite-reducing) and lipolytic (fat-mobilizing) effects
Selective chemical modification of glucagon caused a loss of receptor specificity with minimal change to its inherent activity
The structural basis for the dual activity appears to combine local positional interactions with a change in secondary structure
Two co-agonists, differing only in how strongly they activate the glucagon receptor, were compared in rodent obesity models
Once-weekly PEGylated peptides normalized adiposity and glucose tolerance in diet-induced obese mice
Body-weight reduction came from loss of body fat, through decreased food intake and increased energy expenditure

Methodology

Peptide chemistry and receptor pharmacology to build glucagon/GLP-1 co-agonists, followed by once-weekly dosing of two PEGylated co-agonists in rodent obesity models, including diet-induced obese mice. The abstract does not state group sizes or study length.

Limitations

Rodent data only; no human participants
The abstract reports increased energy expenditure but does not describe the thermogenic mechanism behind it
The benefit depended on balancing glucagon activity against full GLP-1 agonism; the right balance in people is not addressed
Predates retatrutide and did not test it, so its relevance is mechanistic background only
Group sizes and treatment duration are not given in the abstract

Relevance to Content

Early preclinical evidence for the idea behind glucagon-containing multi-agonists: adding glucagon receptor activity to GLP-1 agonism increased energy expenditure and fat loss in rodents. Useful background when explaining why retatrutide includes a glucagon component, as long as it is presented as animal data rather than proof of effect in people.

Summary

Key Findings

Methodology

Limitations

Relevance to Content

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