Researchers at Kyoto University discovered that the molecular regulator carbonic anhydrase VIII, known as CA8, helps coordinate insulin secretion and hepatic glucose production. Published in Science Advances, the findings reveal that CA8 acts as an intracellular brake across both the pancreas and liver, offering a potential new therapeutic target for type 2 diabetes.
Maintaining healthy blood glucose levels depends on a precise physiological balance. The liver produces glucose during fasting periods, while pancreatic beta cells release insulin after meals. In type 2 diabetes, however, hepatic glucose production goes into overdrive while insulin secretion drops to insufficient levels. This multi-organ dysfunction drives hyperglycemia, or high blood glucose.
While intracellular calcium signaling connects these two essential processes, a common molecular regulator linking them had remained elusive. A team of researchers investigated the protein carbonic anhydrase VIII, or CA8, which is known to bind IP3R1—a calcium-release channel located in the endoplasmic reticulum—and to restrain calcium signaling in other tissues. Although CA8 lacks standard enzyme activity, investigators found the protein enriched in both pancreatic islets and liver hepatocytes, prompting a deeper look into its metabolic roles.
Metabolic Testing of Car8wdl Mice and Organ-Specific Duality
To understand the protein’s function, the research team combined metabolic testing of Car8wdl mice—which lack functional CA8—with experiments examining isolated pancreatic islets and liver hepatocytes. The scientists measured glucose production, insulin secretion, calcium responses, and gene expression, alongside pharmacological and genetic evaluations to determine whether these effects relied on IP3R1.
The experiments revealed that CA8-deficient mice exhibited increased secretion of both hepatic glucose and glucose-induced insulin from the pancreas. Yet, in obese and diabetic mice, CA8 expression shifted in opposite directions. Levels rose in the pancreatic islets while falling in the liver hepatocytes, mirroring impaired insulin secretion and excessive glucose production.
When researchers restored CA8 expression in the liver, they observed a reduction in excessive hepatic glucose production and fasting hyperglycemia. Muhammad Fauzi, first author, noted that the team was intrigued that a single intracellular regulator could act as a common brake in two organs but produce very different physiological outcomes, adding that this organ-specific duality gives them a new way to think about the multi-organ nature of type 2 diabetes.
Glucagon Desensitization and Implications for T2D Therapy
Further experiments uncovered how CA8 interacts with hormonal signaling. Chronic exposure to glucagon—the hormone responsible for triggering glucose production—increased CA8 expression, which subsequently desensitized further glucagon stimulation. This glucagon-desensitizing effect mediated by CA8 may offer a mechanistic explanation supporting emerging glucagon-based type 2 diabetes therapies.
Additionally, the team analyzed obese and diabetic mice alongside public RNA-sequencing data from mice fed high-fat diets. They observed intensified CA8 expression in pancreatic islets, pointing directly to the protein’s role in the pathogenesis of type 2 diabetes.
The study was detailed in the paper Carbonic anhydrase VIII regulates IP3R1-dependent Ca2+ signaling to coordinate insulin secretion and hepatic glucose production, published in 2026 in Science Advances (DOI: 10.1126/sciadv.aeh4948). Because the physiological mechanisms were primarily established in mice, investigators emphasize that further studies involving human tissues and cells are necessary before CA8 can be fully established as a viable therapeutic target.
Parallel investigations exploring therapeutic avenues for diabetes have also examined natural compounds such as Polydatin, a natural stilbenoid with a potential role in regulating glucolipid metabolism. In research evaluating pancreatic beta-cell protection, investigators identified common target predictions using databases including TCMSP, PharmMapper, SuperPred, SEA, CTD, and SwissTargetPrediction. While these investigations continue to evaluate agents capable of preserving pancreatic beta-cell survival and mitigating diabetes-related apoptosis, readers examining these scientific updates should consult qualified medical professionals for personal health guidance rather than relying solely on experimental outcomes.
