Aging Pushes Pancreatic Alpha Cells Into Overdrive, Fueling Diabetes Risk

For decades, the scientific conversation about age-related diabetes has revolved around a single cast member: the insulin-producing beta cell. A new study published in Aging Cell argues that another, long-overlooked player deserves equal billing. Researchers report that aging fundamentally rewires pancreatic alpha cells, the glucagon-secreting counterparts of beta cells, driving elevated blood glucagon levels and a breakdown in the mechanisms that normally keep these cells in check. The findings, backed by both mouse experiments and human clinical data, suggest that alpha cell dysfunction may be a hidden engine behind the diabetes epidemic in older populations.

The stakes are considerable. According to the International Diabetes Federation, type 2 diabetes affected 11.1 percent of the global population aged 20 to 74 in 2024, but that figure climbs above 20 percent among people aged 65 to 99. Aging and obesity are the two dominant risk factors for impaired glucose tolerance and type 2 diabetes, and insulin resistance is a central contributor to disease progression. Yet while the beta cell has been exhaustively studied in this context, the alpha cell, which raises blood glucose by triggering hepatic glucose production through glucagon, has remained largely terra incognita in aging research.

To disentangle the effects of aging itself from those of insulin resistance, the team studied 20-month-old male mice divided into two groups based on insulin sensitivity, measured by the QUICKI index, alongside young adult controls. Remarkably, both aged groups, whether insulin sensitive or resistant, developed hyperglucagonemia and showed exaggerated glucagon responses during an arginine tolerance test. Fasting glucagon levels correlated negatively with insulin sensitivity across all animals, indicating that insulin resistance further amplifies the problem, but the core defect emerged with age alone.

Morphological analysis of the pancreas revealed a likely partial explanation: alpha cell area and mass increased progressively in aged animals, with the expansion most pronounced in insulin-resistant mice. This growth did not stem from hypertrophy or new islet formation, since alpha cell size and islet density remained unchanged. Instead, the data suggest an accumulation of long-lived alpha cells formed earlier in life. Intriguingly, alpha cell proliferation actually declined with age, and apoptosis, while remaining very low overall, ticked up slightly in insulin-resistant animals, painting a picture of a slowly expanding, slowly turning-over cell population.

The architecture of the islets themselves also shifted. Insulin-resistant aged mice showed a reduced proportion of insulin-positive cells and an increased percentage of glucagon-positive cells, along with more alpha cells straying from their characteristic position at the islet periphery into the core. Because islet organization is critical for the paracrine signals that regulate hormone secretion, these spatial changes could directly undermine the inhibitory cues that normally restrain glucagon release when glucose is abundant.

Functional testing confirmed that loss of control. In isolated islets exposed to low glucose, which stimulates glucagon secretion, aged cells performed normally. But when the researchers applied the two physiological brakes, high glucose and insulin, islets from insulin-resistant aged mice failed to suppress glucagon significantly, achieving only about 24 percent inhibition with glucose and 28 percent with insulin, compared with roughly 43 and 54 percent in young controls. Patch-clamp recordings showed that voltage-gated potassium and calcium currents and the exocytotic machinery were largely preserved, pointing the finger at impaired glucose sensing, metabolism, or paracrine signaling rather than a generalized secretory failure.

Transmission electron microscopy uncovered the most striking cellular signature: a markedly enlarged endoplasmic reticulum in alpha cells from both aged groups, a classic hallmark of ER stress. The secretory granules themselves appeared largely normal in number, density, and maturation, though insulin-resistant mice showed slightly larger granules and fewer docked at the membrane, possible signs of early exhaustion from compensatory hypersecretion. Reanalysis of single-cell RNA sequencing data from more than 300,000 islet cells reinforced the finding, revealing upregulated expression of ER stress and unfolded protein response genes, including Hspa5, Atf6, Ddit3, and Xbp1, in alpha cells from old mice. Immunostaining confirmed increased BiP protein in aged alpha cells.

Notably, this ER stress appears adaptive rather than lethal. Unlike beta cells, which lose function under chronic ER stress, aged alpha cells retained their secretory capacity at stimulatory glucose concentrations and showed apoptosis rates of only about 0.1 to 0.2 percent. Recent work suggests ER stress in alpha cells can even enhance glucagon release. The researchers also detected moderate erosion of alpha cell identity: the proportion of glucagon-positive cells expressing the master regulator Arx declined modestly, and insulin-resistant aged mice showed a higher frequency of rare bihormonal cells producing both insulin and glucagon, echoing observations in insulin-resistant humans and elderly rhesus monkeys.

Crucially, the mouse findings translated to humans. Within the CORDIOPREV clinical study, the team analyzed 462 patients without diabetes at baseline, of whom 107 developed type 2 diabetes over a median follow-up of 60 months. Older adults with insulin resistance, whether classified by biological age using telomere length or by chronological age, displayed significantly higher fasting glucagon levels and a greater glucagon secretory response during an oral glucose tolerance test than any other group. Kaplan-Meier analysis showed that while age alone already conferred a significant risk of developing diabetes, elevated glucagon levels amplified that risk further.

The study’s authors caution that several questions remain, including how systemic factors such as inflammation, senescence-associated secretory signals from neighboring beta cells, and altered paracrine regulation integrate with intrinsic alpha cell aging. But the central message is clear: alpha cells are resilient survivors of aging that paradoxically become a metabolic liability, pumping out glucagon when the body can no longer rein them in. As glucagon signaling emerges as a therapeutic target in type 2 diabetes, older adults with insulin resistance may represent the population that stands to benefit most from treatments aimed at restoring the brake on these wayward cells.

Subject of Research: Effects of aging on pancreatic alpha cell function, glucagon secretion, and age-associated type 2 diabetes risk

Article Title: Aging Affects Pancreatic α‐Cell Function and Promotes Hyperglucagonemia: Implications in Age‐Associated Diabetes

Article References: Tudurí, E., Almagro, L., Ojeda‐Rodríguez, A., Pascua‐Maestro, R., Brunetta, H. S., Soriano, S., López‐Moreno, A., Boronat‐Belda, T., Velasco‐Avilés, S., da Silva Junior, J. A., Castellano‐Muñoz, M., Rafacho, A., Cózar‐Castellano, I., Nadal, Á., Alonso‐Magdalena, P., Merino, B., López‐Miranda, J., & Quesada, I. (2026). Aging Affects Pancreatic α‐Cell Function and Promotes Hyperglucagonemia: Implications in Age‐Associated Diabetes. Aging Cell, 25(10), Article e70753. https://doi.org/10.1111/acel.70753

Image Credits: AI Generated

DOI: 10.1111/acel.70753

Keywords: pancreatic alpha cells, glucagon, aging, type 2 diabetes, insulin resistance, hyperglucagonemia, endoplasmic reticulum stress, islet architecture, CORDIOPREV study, beta cells, glucose homeostasis, Aging Cell