GLP-1 Receptor Agonists in Type 2 Diabetes: State-of-the-Art Review
Nauck et al. (2021) published a comprehensive state-of-the-art review of GLP-1 receptor agonists (GLP-1 RAs). The review detailed the common mechanisms of action shared by all GLP-1 RAs: augmentation of hyperglycemia-induced insulin secretion, suppression of glucagon secretion at hyper- or euglycemia, deceleration of gastric emptying that prevents large post-meal glycemic increments, and a reduction in calorie intake and body weight. The authors noted that short-acting agents maintain their effect on gastric emptying during long-term treatment, while long-acting agents show tachyphylaxis for this effect. The review also highlighted emerging evidence for cardiovascular and renal protective effects beyond glucose control.
Citation: Nauck MA, Quast DR, Wefers J, Meier JJ. GLP-1 receptor agonists in the treatment of type 2 diabetes – state-of-the-art. Mol Metab. 2021;46:101102. doi:10.1016/j.molmet.2020.101102. PubMed PMID: 33068776
GLP-1 Promotes Islet Cell Growth and Inhibits Apoptosis in Diabetic Models
Farilla et al. (2002) investigated the trophic effects of GLP-1 on pancreatic islet cells using the Zucker diabetic rat model. The study demonstrated that GLP-1 administration promoted islet cell proliferation while simultaneously inhibiting apoptosis. GLP-1-treated animals showed improved glucose tolerance and enhanced beta cell mass compared to controls. Staining of pancreatic sections revealed increased Ki-67 expression (a marker of cell proliferation) and decreased TUNEL-positive cells (a marker of apoptosis) in GLP-1-treated islets. This study provided early mechanistic evidence that GLP-1’s beneficial effects in diabetic models involve direct trophic actions on the islet cell population.
Citation: Farilla L, Hui H, Bertolotto C, Kang E, Bulotta A, Di Mario U, Perfetti R. Glucagon-like peptide-1 promotes islet cell growth and inhibits apoptosis in Zucker diabetic rats. Endocrinology. 2002;143(11):4397-4408. doi:10.1210/en.2002-220405. PubMed PMID: 12399437
GLP-1 Receptor Signaling Modulates Beta Cell Apoptosis
Li et al. (2003) demonstrated that GLP-1 receptor signaling directly modulates the susceptibility of pancreatic beta cells to apoptotic injury. Using MIN6 beta cells and isolated mouse islets, the researchers showed that activation of the GLP-1 receptor by exendin-4 (a GLP-1 receptor agonist) reduced apoptosis induced by multiple stressors including streptozotocin, cytokines, and fatty acids. The anti-apoptotic effect was mediated through activation of PI3K and subsequent phosphorylation of Akt, which in turn phosphorylated and inactivated the pro-apoptotic factor Bad. These findings provided a molecular mechanism linking GLP-1 receptor activation to preservation of beta cell mass.
Citation: Li Y, Hansotia T, Yusta B, Ris F, Halban PA, Bhatt RS, Drucker DJ. Glucagon-like peptide-1 receptor signaling modulates beta cell apoptosis. J Biol Chem. 2003;278(1):471-478. doi:10.1074/jbc.M209423200. PubMed PMID: 12409292
Glucagon-Like Peptides as Regulators of Cell Proliferation, Differentiation, and Apoptosis
In a seminal review, Drucker (2003) comprehensively examined the roles of GLP-1 and GLP-2 as regulators of cell proliferation, differentiation, and apoptosis. The review detailed how GLP-1 promotes cell differentiation from exocrine cells or immature islet progenitors toward a more differentiated beta cell phenotype. GLP-1 was shown to exert anti-apoptotic actions in vivo, resulting in preservation of beta cell mass. The author described the signaling cascades downstream of GLP-1 receptor activation — including cAMP, PKA, PI3K, Akt, and MAPK pathways — and their integration into proliferative and pro-survival responses. This review established the foundational framework for understanding how incretin hormones regulate islet cell biology.
Citation: Drucker DJ. Glucagon-like peptides: regulators of cell proliferation, differentiation, and apoptosis. Mol Endocrinol. 2003;17(2):161-171. doi:10.1210/me.2002-0306. PubMed PMID: 12554744
GLP-1 Inhibits Apoptosis and Improves Glucose Responsiveness of Human Islets
Farilla et al. (2003) extended their earlier animal model work to human tissue, demonstrating that GLP-1 inhibits cell apoptosis and improves glucose responsiveness of freshly isolated human islets. Human pancreatic islets cultured with GLP-1 for five days showed preserved morphology and function compared to untreated controls. The GLP-1-treated islets demonstrated enhanced glucose-stimulated insulin secretion and maintained intracellular insulin content. Importantly, GLP-1 significantly reduced the rate of islet cell apoptosis, as measured by caspase-3 activity and TUNEL staining. This study was critical in translating preclinical GLP-1 findings to human tissue and supporting the potential of GLP-1 receptor agonism for beta cell preservation research.
Citation: Farilla L, Bulotta A, Hirshberg B, Li Calzi S, Khoury N, Noushmehr H, Bertolotto C, Di Mario U, Harlan DM, Perfetti R. Glucagon-like peptide 1 inhibits cell apoptosis and improves glucose responsiveness of freshly isolated human islets. Endocrinology. 2003;144(12):5149-5158. doi:10.1210/en.2003-0323. PubMed PMID: 12960095
Reviewed for scientific accuracy — Chameleon Peptides Research Team. Last reviewed: March 2026.