Study identifies predictive causal role for specific cell types in type 1 diabetes

Researchers at the University of California San Diego School of Medicine revealed a predicted causative role for certain cell types in type 1 diabetes, an illness that affects more than 1.6 million Americans, by examining its genetic foundations.

Type 1 Diabetes. Image Credit: Eviart/Shutterstock.com

The study results were published in the online edition of Nature.

Type 1 diabetes is a complicated autoimmune illness defined by the damage and loss of insulin-producing pancreatic beta cells, followed by hyperglycemia (high blood sugar), which is harmful to the body and can lead to other major health issues like eyesight loss and heart disease.

Type 1 diabetes is less frequent than type 2 diabetes, although it is becoming more frequent. According to the Centers for Disease Control and Prevention, five million Americans will develop type 1 diabetes by 2050. There is currently no treatment, only disease management.

Type 1 diabetes mechanisms, particularly how autoimmunity is initiated, are poorly known. Because it has a significant genetic component, multiple genome-wide association studies (GWAS) have been done in recent years, in which researchers analyze full genomes of people with the same condition or disease, looking for changes in the genetic code that may be connected with that condition or disease.

In the case of type 1 diabetes, known at-risk variants have mostly been located in the genome’s non-coding regions.

Kyle Gaulton, Ph.D., an assistant professor in the Department of Pediatrics at UC San Diego School of Medicine, and collaborators merged GWAS data with epigenomic maps of cell types in the pancreas and peripheral blood in the Nature study.

Epigenomic mapping describes how and when genes are activated and deactivated in cells, hence influencing the synthesis of proteins required for various cellular processes.

Researchers specifically conducted the largest-to-date GWAS of type 1 diabetes, evaluating 520,580 genomic samples to uncover 69 unique association signals. The researchers next identified 448,142 cis-regulatory elements (non-coding DNA sequences within or near a gene) in pancreatic and peripheral blood cell types.

By combining these two methodologies, we were able to identify cell type-specific functions of disease variants and discover a predictive causal role for pancreatic exocrine cells in type 1 diabetes, which we were able to validate experimentally.”

Kyle Gaulton, PhD, Study Senior Author and Assistant Professor, Department of Pediatrics, UC San Diego School of Medicine

Pancreatic exocrine cells release enzymes into the small intestine, where they aid in digestion.

The results, according to co-author Maike Sander, MD, professor in the departments of Pediatrics and Cellular and Molecular Medicine at the University of California, San Diego School of Medicine, and director of the Pediatric Diabetes Research Center constitute a significant advancement in understanding the origins of type 1 diabetes. She called the research a “landmark study.”

The implication is that exocrine cell dysfunction might be a major contributor to disease. This study provides a genetic roadmap from which we can determine which exocrine genes may have a role in disease pathogenesis.”

Maike Sander, MD, Study Co-Author and Professor, Departments of Pediatrics and Cellular and Molecular Medicine, UC San Diego School of Medicine

“Understanding how type 1 diabetes originates at the cellular level is a critical step in finding treatments for reversing its course and, ultimately, preventing the disease altogether,” concluded first author Joshua Chiou, Ph.D., a recent graduate of the Biomedical Sciences graduate program at UC San Diego.