GLP-1 is developing a reputation as a “magic bullet.” The drug was initially characterized by its ability to improve insulin release and treat diabetes, but was later found to promote weight loss and improve cardiovascular health. In addition to these amazing bonus benefits, GLP-1 drugs have the ability to improve pancreatic beta cell health. But how exactly does it do that?
Salk Institute researchers are digging into the details of the mechanisms behind how GLP-1 drugs promote pancreatic beta cell viability and stress tolerance. Because adaptations in cell performance arise from changes in gene expression, the research team screened for regulatory proteins that can “turn on” advantageous genetic programs during long-term use of GLP-1. They identified a protein called Med14, part of a larger protein complex called Mediator, that enables GLP-1-dependent changes in gene expression that lead to pancreatic health benefits.
This study Proceedings of the National Academy of Sciences Funding was provided by a federal research grant from the National Institutes of Health and private philanthropy.
The widespread beneficial effects of GLP-1 drugs on diabetes, cardiovascular disease, and obesity have triggered a wave of exciting scientific research at the mechanistic level. We wonder, “How does GLP-1 cause these effects?” We were able to single out a protein, Med14, that helps reprogram gene expression in pancreatic beta cells by activating downstream of GLP-1, improving cell viability and insulin production. ”
Marc Montminy, MD, senior author, biochemist, physiologist, distinguished professor emeritus at Salk University
What are GLP-1 drugs?
They are often simply referred to as “GLP-1 drugs” or “GLPs.” Glucagon-like peptide-1 receptor agonist It works by mimicking the hormones that our bodies naturally produce. This hormone, called glucagon-like peptide-1, helps regulate blood sugar levels by stimulating the secretion of insulin. They do this by binding to the corresponding GLP-1 receptors on pancreatic beta cells, producing and releasing insulin into the body.
However, there is one major difference between GLP-1 drugs and their natural counterparts. That said, unlike the man-made GLP-1 hormone, which comes and goes quickly around mealtime, man-made GLP-1 receptor agonists can linger much longer. Salk researchers suspect that this long-term existence may explain some of the “magic bullet” benefits of GLP-1 drugs. But at a molecular level, what exactly do GLP-1 drugs do when they linger, and how does their staying power translate to benefits like lower stroke risk and improved osteoarthritis?
“The fact that these hormone-based drugs are stable seems to be important for the long-term effects we are witnessing in pancreatic beta cells and other tissues,” says lead author Sam van de Velde, Ph.D., a staff scientist in the Montminy lab. “To understand how these long-term effects are achieved, we need to study these drugs over longer time scales, and that’s exactly what we did.”
How do GLP-1 drugs affect pancreatic health?
It is well documented that once the hormone GLP-1 finds a pancreatic beta cell, a series of subsequent changes in signal, protein, and gene expression lead to insulin secretion. On the other hand, the mechanisms and changes in long-term GLP-1 drug scale are poorly understood.
So the researchers embarked on a molecular fishing expedition for pancreatic beta cell lines. The research team expected to hook into proteins that undergo a specific chemical modification called phosphorylation after GLP-1 activation. And that’s exactly what they found with Med14.
Med14 is a subunit of a multiprotein complex called Mediator, which is a general regulator of gene expression throughout the genome. To see if Med14 is an essential link between GLP-1 drugs and eventual changes in gene expression and behavior of pancreatic beta cells, the researchers decided to perform a mutation. Med14, renders the protein resistant to phosphorylation.
Gene expression patterns associated with long-term GLP-1 drug exposure were abolished in the Med14 mutant pancreatic beta cell line and the beta cells of the Med14 mutant mouse model. Med14 activates a helpful genetic program that allows the beta cells in the pancreas to become hypercharged and grow, better able to cope with the postprandial sugar-rich environment.
What other effects can GLP-1 drugs have on the body?
Although none of the Salk team’s experiments were conducted on humans, they remain relevant. For example, some of the genes regulated by Med14 phosphorylation are known to be associated with type 2 diabetes susceptibility in humans.
“Our findings unexpectedly reveal that phosphorylation of a small portion of the Med14 protein plays an important role in the response to GLP-1 drugs and in the metabolic response to hormones more broadly,” says Reuben Shaw, Ph.D., Salk University professor, holder of the William R. Brody Professorship, and director of the National Cancer Institute-designated Salk Cancer Center. “There are many new questions to answer, from validating our findings in human tissues to confirming whether Med14 plays a similar role in other cells and organs.”
The research team is particularly interested in the effects of long-term GLP-1 exposure beyond pancreatic beta cells. One of the messenger molecules between GLP-1 and Med14 is called cAMP, which is a commonly used messenger molecule in many other situations that do not involve GLP-1. With that in mind, could other drugs and hormones also activate genetic programs similar to GLP-1? And what happens in other metabolically intensive tissues, such as fat?
Questions about so-called “magic bullets” persist, and Salk scientists are working diligently to answer them.
Other authors and funding
Other authors include Jungting Yu, K. Garrett Evensen, Edmund Pakhlevanyan, and Salk’s April Williams.
This research was supported by the National Institutes of Health (5R01 DK083834, R35 CA220538), Breakthrough T1D (INO-2022-1125-AN), the Paul F. Glenn Research Foundation for the Biology of Aging, the Creighton Medical Research Foundation, and the Leona M. Helmsley and Harry B. Helmsley Charitable Trust.
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Reference magazines:
Van de Velde, S. Others. (2026). Med14 phosphorylation shapes the genomic response to GLP-1 agonists. Proceedings of the National Academy of Sciences. DOI: 10.1073/pnas.2536772123. https://www.pnas.org/doi/10.1073/pnas.2536772123
