RESEARCH NEWS STORY
July 5, 2023
Chiba University

New Study Shows Glutaminase 2 Regulates
Glucose Metabolism in Pancreatic β-Cells
Researchers use knockout mice and gene expression data to show that glutaminase 2 isinvolved in pancreatic glucose homeostasis under hyperglycemia
The enzymatic conversion of glutamine to glutamate is an important mitochondrial energy
pathway that is catalyzed by glutaminase 2 (GLS2). GLS2, abundant in the liver, is also foundin pancreatic β-cells. However, its role in pancreatic islets involved in glucose metabolism
remains mysterious. Now, researchers from Chiba University, Japan, have used in vivo
experiments and human islet cell gene expression data to show that pancreatic β-cell GLS2
regulates glucose metabolism under the condition of hyperglycemia.

Image title: Mechanism for the onset of diabetes mellitus following GLS2 inhibition.
Image caption: Researchers from Chiba University in Japan have found that GLS2 has an important role inglucose homeostasis under conditions of hyperglycemia.
Image credit: Sawako Suzuki from Chiba University, Japan
Image license: Original content

Glutaminase 2 (GLS2) is a master regulator of glutaminolysis. GLS2 converts glutamine toglutamate, thereby playing a role in cellular energy production. GLS2 is abundant in theliver, and is also found in pancreatic β-cells. However, the role of GLS2 in pancreatic islets –in which both ɑ- and β- cells are present – associated with glucose metabolism is currently
unknown.
Glucose homeostasis is known to be maintained by an intricate and complex interaction
between the liver, pancreatic ɑ- cells (which make glucagon), pancreatic β-cells (that makeinsulin), and associated organs, such as the intestines, skeletal muscles, and fat tissue.
Researchers from Chiba University in Japan had previously identified GLS2 as a target genefor p53, thereby functioning as a tumor suppressor. Since diabetes and cancer are closely
related, they decided to further examine the role of β-cells-specific GLS2 in glucose
homeostasis.
In the present study, they have uncovered the role of GLS2 in glucose homeostasis. They did
so by using a mouse model, in which GLS2 was conditionally deleted in pancreatic β-cells,
known as Gls2 CKO mice, along with a human pancreas islet gene data repository. Theirfindings were published online in Scientific Reports Volume 13 on May 05, 2023. The study
was led by Ms. Hannah Deguchi-Horiuchi, a doctoral student, and senior lecturer Sawako
Suzuki and co-authored by Prof. Koutaro Yokote from Chiba University.
“Our previous work identified GLS2 as a target of p53, which governs ferroptosis, andshowed that GLS2 had tumor suppressor function in vivo. We also knew that the GLS2
metabolite of glutamate regulated glucose-stimulated insulin production and hypothesizedthat the enzyme had a role to play in glucose homeostasis in pancreatic islets. This study
offers important insights as diabetes and cancer may share a common molecular basis in
their pathogenesis,” explains Dr. Suzuki regarding the group’s motivation to pursue theresearch.
The research team compared glucose homeostasis between Gls2 knockout (Gls2 CKO) andcontrol (RIP-Cre) mice. “When fed a high-fat diet, we found that GLS2 and p53 expression
increased in pancreatic β-cells from RIP-Cre mice. Conversely, the Gls2 CKO mice developed
diabetes mellitus, insulin resistance, and sustained glucose production. Paradoxically, insulin
secretion was suppressed and glucagon secretion elevated despite the high blood glucose
levels in Gls2 CKO mice,” says Dr. Suzuki. “This shows that impaired GLS2 activity drives theonset of diabetes mellitus by exacerbating the disrupted insulin and glucagon regulation.”
The research group’s findings were validated in separate experiments in which GLS2 wassilenced in pancreatic β-cells generated from a mouse cell line. Once again, insulin secretion
was seen to be reduced. Further, human pancreatic islet cell gene expression data fromdiabetic donors showed an increase in GLS2 expression. Lastly, in line with the Gls2
knockout mouse data, downregulated GLS2 in pancreatic β-cells from diabetic donors wasparadoxically linked to suppressed insulin and enhanced glucagon gene expression.
These findings show that pancreatic β-cell GLS2 is intricately involved in regulating glucose
levels under conditions of hyperglycemia. But are there any long-term therapeutic

applications for this research?
Indeed, this study emphasizes that developing tailor-made diabetic medications must
incorporate a patient’s genetic information along with data on blood glucose levels,metabolic status, age, duration of diabetes, and family history of the disease. Dr. Suzuki
concludes, “We need to delve deeper into the GLS2-regulated glucose metabolism. Patients
harboring GLS2 loss-of-function gene alterations could inherently have the potential todevelop diabetes mellitus. In the future, GLS2 could even be a therapeutic target for patients
suffering from this debilitating disease.”
About Associate Professor Sawako Suzuki
Dr. Sawako Suzuki is an Associate Professor in the Department of Diabetes, Metabolism, andEndocrinology at Chiba University Hospital in Japan. Dr. Suzuki has published over 50 peerreviewed articles.
Reference:

Title of original paper: Pancreatic β-cell glutaminase 2 maintains glucose homeostasis under thecondition of hyperglycaemia
Authors: Hannah Deguchi-Horiuchi1,2, Sawako Suzuki1,2, Eun Young Lee3, Takashi Miki3, Noriko
Yamanaka4, Ichiro Manabe5, Tomoaki Tanaka5, Koutaro Yokote1,2
Affiliations:1
Department of Endocrinology, Hematology and Gerontology, Graduate School of Medicine, Chiba
University, Japan.
2
Department of Diabetes, Metabolism and Endocrinology, Chiba University Hospital, Japan.
3
Department of Medical Physiology, Graduate School of Medicine, Chiba University, Japan.
4
Department of Disease Biology and Molecular Medicine, Graduate School of Medicine, Chiba
University, Japan.
5
Department of Molecular Diagnosis, Graduate School of Medicine, Chiba University, Japan.
Journal: Scientific Reports
DOI: 10.1038/s41598-023-34336-z

Contact:
Sawako SUZUKI
Graduate School of Medicine, Chiba University
Address: 1-8-1 Inohana, Chuo, Chiba 260-8670, Japan
Email: sawakosuzuki@chiba-u.jp
Public Relations Office, Chiba University
Address: 1-33 Yayoicho, Inage, Chiba 263-8522, Japan
Email: koho-press@chiba-u.jp