How the body keeps insulin-producing cells in check may shape future diabetes therapies

The insulin-producing beta cells nestled within the pancreatic islets of Langerhans are among the most tightly regulated cells in the human body, and a new commentary in the Journal of Molecular Medicine argues that this strict regulation holds the key to understanding why current diabetes therapies fall short and how future ones might succeed. Sigurd Lenzen of the Institute of Experimental Diabetes Research at Hannover Medical School lays out a detailed physiological account of how beta-cell mass is established, maintained and lost, and why the timing of therapeutic intervention may matter as much as the therapy itself. The analysis arrives at a moment of extraordinary ferment in diabetes research, as incretin-based drugs reshape the treatment landscape and immunotherapies edge closer to altering the course of type 1 diabetes.

The starting point of the commentary is a deceptively simple set of numbers. Beta cells proliferate slowly compared with most other cell types. In rodents, the replication rate ranges from roughly one to two percent per day. In humans it is an order of magnitude lower, somewhere between 0.1 and 0.2 percent per day. The rate is higher in children and adolescents than in adults, because during physical growth the beta-cell mass must expand in parallel with increasing body mass to meet the rising demand for insulin. Once adulthood is reached, however, the proliferative machinery is dialed down to a near-idle pace.

That near-idle pace is not, in itself, a design flaw. During the neonatal phase and early childhood, the formation of new beta cells from progenitor cells plays a central role in expanding the beta-cell mass. In adulthood, by contrast, new beta cells arise almost exclusively through the self-duplication of existing ones. Although this rate is very low, it is not zero, and crucially it appears to be sufficient. The trickle of new cells compensates for losses caused by apoptotic beta-cell death, thereby maintaining a stable functional population across decades of life. Beta cells, in other words, retain a degree of plasticity even in the mature pancreas, but that plasticity operates within narrow limits.

Lenzen emphasizes that the organism appears to possess an internal set point for functional beta-cell mass, and that this set point serves a protective purpose. Insulin is a potentially lethal molecule when present in excess, and unregulated expansion of the beta-cell population would risk fatal hypoglycemia. The clearest demonstration of the dangers of losing this regulatory control is persistent hyperinsulinemic hypoglycemia of infancy, a congenital disorder in which the genetically determined regulation of functional beta-cell mass fails, leading to life-threatening overproduction of insulin. Far from being a limitation to be overcome, the slow proliferation rate reflects an evolved compromise between metabolic safety and repair capacity.

The set point is not fixed in stone, however. Beta-cell mass is subject to complex hormonal regulation that operates across the mammalian kingdom, including in humans. Thyroid hormones reduce beta-cell mass by promoting apoptosis, while glucocorticoids increase it by stimulating proliferation. The well-documented expansion of beta-cell mass during pregnancy provides another striking example of physiologically orchestrated adaptation. In each case, the endocrine system adjusts the size of the insulin-producing cell pool to match anticipated metabolic demand, and understanding these regulatory levers has become a central goal of diabetes research.

The relevance to disease becomes apparent when one traces what happens to beta-cell mass over a lifetime in the context of modern lifestyles. In many adults, beta-cell mass increases by up to 50 percent between the third and fifth decades of life, coinciding with the development of obesity during this period. This expansion is driven by increasing insulin resistance associated with a Western diet and lifestyle, and the accompanying rise in insulin production. Only a minority of individuals, no more than 20 percent, are able to maintain this elevated beta-cell mass and the resulting adequate insulin supply into old age despite ongoing obesity. The vast majority cannot. In most people, a gradual decline in beta-cell mass follows this phase of life, leading to insulin deficiency and ultimately to the development of type 2 diabetes. The proliferative capacity of beta cells therefore matters in two ways: it can counteract the deterioration of metabolic state during the pre-diabetic phase, and it may support efforts to restore metabolic control after diabetes onset. At the same time, any increased workload on beta cells, whether caused by obesity or autoimmune attack, carries the risk of deteriorating beta-cell function and shrinking beta-cell mass, so reducing that workload is itself a therapeutic priority.

Hormones capable of increasing beta-cell mass have consequently moved to the forefront of scientific interest, and none more so than the gut hormone glucagon-like peptide-1, or GLP-1. A recent study by Erbasan and colleagues, published in the same journal, has provided compelling new evidence for the regenerative potential of this incretin hormone. Using gene therapy in neonatal and adult streptozotocin-diabetic rats, the researchers achieved GLP-1 release through lentivirally mediated overexpression of the hormone in hepatocytes. The result was support for pancreatic beta-cell regeneration, but with a crucial developmental twist. In the neonatal pancreas, plasticity was high, and beta-cell neogenesis from progenitor and duct-derived cells was evident. In the adult pancreas, new beta cells were generated mainly through self-duplication of existing cells, confirming earlier landmark observations, with only limited potential for neogenesis and consequently for recovery of beta-cell mass.

The implications for therapy are direct. GLP-1-based treatment represents a future option for counteracting the insulin deficiency that develops gradually during the course of type 2 diabetes as beta cells progressively fail. Ideally, Lenzen argues, such intervention should occur before metabolic deterioration sets in, when supporting endogenous proliferation can preserve beta-cell mass most effectively. Treatment with a GLP-1 analogue would offer a double benefit in this window: it would support the preservation of beta-cell mass while simultaneously promoting weight loss, thereby easing the insulin resistance that drives the excessive workload on the remaining cells in the first place.

Type 1 diabetes presents an even more formidable challenge, because the beta-cell loss is driven by autoimmune destruction rather than metabolic overload. More than 90 percent of patients who develop type 1 diabetes have no family history of the disease, which means almost all individuals are diagnosed only when they manifest overt disease at stage 3, by which point much of the beta-cell mass has already been destroyed. Interestingly, however, in the weeks following disease onset, most patients enter a remission phase while receiving insulin replacement therapy, during which the remaining beta cells recover. It is during this phase, ideally after beta-cell recovery but before the onset of renewed metabolic deterioration, that the chances of achieving a significant increase in beta-cell mass through self-duplication are optimal. Seizing this window requires therapies with curative potential, and because numerous monotherapies have proven ineffective, only combination therapies based on a profound understanding of the underlying pathomechanisms and validated in reliable preclinical animal studies are considered promising candidates. A critical constraint is that successful combination therapies for type 1 diabetes require the presence of at least 30 percent of normal beta-cell mass at the start of treatment.

The arithmetic of regeneration underscores why timing is everything. Based on generally accepted beta-cell proliferation rates of one percent per day in rats and 0.1 percent per day in humans, Lenzen calculates that after a cessation of autoimmune-mediated beta-cell destruction, approximately two months are required in rats to increase beta-cell mass from one-third to two-thirds of the original healthy mass, a prediction that aligns with experimental results from animal models. By analogy, the same increase in humans would take one to two years. Encouragingly, a recent medical case study found that a combination of the two therapeutic antibodies teplizumab and adalimumab proved effective in patients, resulting in sustained metabolic health one year after the start of therapy, with no symptoms of diabetes and no need for insulin replacement. Yet the sequencing matters profoundly. Only after successfully suppressing the autoimmune destruction driven by the proinflammatory cytokines TNF-alpha and IL-1 beta, and eliminating the immune-cell infiltration within the islets, does the administration of an agent such as a GLP-1 analogue become a viable option to enhance spontaneous beta-cell regeneration. This approach is particularly suitable when beta-cell mass is already significantly reduced below 50 percent, as it provides supplementary support for proliferation. Administering the agent earlier, while the autoimmune attack is still ongoing, would merely result in the immediate destruction of the newly formed beta cells; studies in animal models have shown that during an ongoing autoimmune attack, proliferation does attempt to counteract beta-cell loss but ultimately fails.

The overarching message is one of calibrated optimism. Despite the different pathomechanisms responsible for beta-cell loss in type 1 and type 2 diabetes, distinct windows of opportunity exist for therapeutic interventions at appropriate stages of both diseases. In type 2 diabetes, that window opens in the pre-diabetic phase, when GLP-1-based therapy can preserve and support an expanded beta-cell mass before it collapses under the combined burdens of insulin resistance and age-related proliferative decline. In type 1 diabetes, the window opens after autoimmune destruction has been halted and the remaining beta cells have begun to recover, when regenerative support can rebuild a functional cell population from the residual base. In both cases, the prospect of supporting endogenous mechanisms for increasing beta-cell mass through beta-cytotrophic molecules offers a pathway that works with the body’s own biology rather than against it. The slow pace of beta-cell renewal, once viewed primarily as an obstacle, is now understood as the defining constraint that any curative strategy must respect, and the therapies that succeed will be those that arrive at precisely the right moment in the disease course.

Subject of Research: Regulation of pancreatic beta-cell mass and its implications for antidiabetic therapies

Article Title: Regulation of pancreatic beta-cell mass and its importance for antidiabetic therapies

Article References: Regulation of pancreatic beta-cell mass and its importance for antidiabetic therapies. (n.d.). https://doi.org/10.1007/s00109-026-02716-3

Image Credits: AI Generated

DOI: 10.1007/s00109-026-02716-3

Keywords: pancreatic beta cells, beta-cell mass, diabetes, type 1 diabetes, type 2 diabetes, GLP-1, beta-cell proliferation, insulin, autoimmunity, gene therapy, teplizumab, endocrinology