GIP and GLP-1 have complementary effects across the brain, pancreas, and fat tissue, explaining why dual agonists like tirzepatide outperform single GLP-1 drugs for diabetes and obesity.
Complementary, not redundantGIP and GLP-1 have opposing effects on glucagon and fat metabolism, which is why combining them produces better results than either alone
What the researchers found
This review maps out how the two incretin hormones — GIP and GLP-1 — work across multiple organ systems and why combining their actions in dual agonist drugs produces superior metabolic effects. Key mechanistic differences include: both suppress appetite through brain satiety centers, both stimulate insulin from beta cells, but they diverge on glucagon — GIP promotes glucagon release during low blood sugar (protective against hypoglycemia) while GLP-1 suppresses glucagon during high blood sugar. On fat metabolism, GIP directly promotes fat storage in appropriate tissue while GLP-1 indirectly promotes fat breakdown, and together they maintain healthy fat distribution, reduce ectopic fat, and boost adiponectin secretion.
This complementary biology explains why dual GIP/GLP-1 agonists like tirzepatide can achieve greater weight loss and metabolic improvement than GLP-1-only drugs, while the GIP component provides a safety buffer against hypoglycemia.
Why it matters
Understanding why dual agonists outperform single GLP-1 agonists is crucial as the field moves toward triple agonists and next-generation metabolic drugs. This review provides the mechanistic roadmap: GIP and GLP-1 are not redundant — they have complementary and sometimes opposing effects that together create a more balanced metabolic intervention. This knowledge guides the development of future drugs with better efficacy and fewer side effects.
The numbers in context
2 incretin hormones (GIP and GLP-1) · Multiple tissue targets: brain, pancreatic β-cells, α-cells, adipocytes · Complementary effects on glucagon: glucagonotropic (GIP) vs glucagonostatic (GLP-1)
How the study worked
This is a narrative review published in Frontiers in Endocrinology that synthesizes published research on the cellular and molecular mechanisms of GIP and GLP-1 signaling across multiple tissues. The author reviews the pharmacology of approved GLP-1 and dual GIP/GLP-1 receptor agonists and their clinical trial outcomes in type 2 diabetes, obesity, and cardiovascular disease.
Who was studied
Review article — no direct study population
What this study cannot tell us
As a narrative review by a single author, it reflects one perspective on the literature rather than a systematic synthesis. Some mechanistic details are derived from preclinical studies that may not fully translate to humans. The review does not provide quantitative comparisons between specific drugs or detail their side effect profiles. Rapidly evolving clinical trial data means some conclusions may already be outdated.
How to read the evidence
This is a narrative review in a respected endocrinology journal, providing a comprehensive synthesis of molecular, preclinical, and clinical evidence. While reviews do not generate new data, this one effectively organizes the mechanistic understanding underpinning one of the most important drug classes in modern medicine.
When this study was published
Published in 2024, this is a very current review capturing the latest understanding of incretin biology at a time when dual and triple agonists are reshaping metabolic medicine.
The bigger picture
The incretin field is evolving rapidly from single GLP-1 agonists to dual agonists (GIP/GLP-1) and now triple agonists (GIP/GLP-1/glucagon). Understanding how each component contributes to metabolic improvement is essential for rational drug design. This review provides the mechanistic foundation for that progression, explaining why more receptor targets don't just mean more of the same effect — they create qualitatively different and potentially superior metabolic outcomes.
Questions still open
- Could selective GIP agonists alone have therapeutic value for specific metabolic conditions, or does GIP only shine in combination with GLP-1?
- How will triple agonists (adding glucagon receptor activation) change the benefit-harm balance compared to dual agonists?
- Do the complementary effects of GIP and GLP-1 on fat metabolism explain why tirzepatide produces more favorable body composition changes than semaglutide?
Common questions
What's the difference between GLP-1 drugs and dual GIP/GLP-1 drugs?
Why does GIP help prevent hypoglycemia?
Read the original research
Mechanisms of action and therapeutic applications of GLP-1 and dual GIP/GLP-1 receptor agonists.
Frontiers in endocrinology, 15, 1431292
Citation
Liu, Qiyuan Keith. (2024). Mechanisms of action and therapeutic applications of GLP-1 and dual GIP/GLP-1 receptor agonists.. Frontiers in endocrinology, 15, 1431292. https://doi.org/10.3389/fendo.2024.1431292