Diabetes research: From epigenetics to islet cell transplants
January 4, 2014 | by Elizabeth Stewart
Nearly 350 million people worldwide are coping with diabetes, and the disease is expected to be the seventh-leading cause of death by 2030. Aware of these grim statistics, researchers at City of Hope are committed to halting the global epidemic.
On the frontiers of epigenetic engineering
Art Riggs, Ph.D., chair of the Department of Diabetes and Metabolic Diseases Research, is focused on the possibilities within the field of epigenetics. A concept pioneered by Riggs, epigenetics refers to stable changes in gene expression, some of which can be passed on to future generations — but are not written into our genetic code.
Riggs is currently studying epigenetic engineering, the process of making epigenetic changes in stem or progenitor cells to impact how those cells differentiate, grow and mature. Riggs is collaborating with researchers throughout City of Hope’s Diabetes Research Center to find ways to use epigenetic engineering to increase the supply of beta cells for islet transplantation, and to improve regulatory T cells to reverse autoimmunity.
Beta cells, a type of islet cell, make insulin. In people with type 1 diabetes, those beta cells have been destroyed by an autoimmune response.
By focusing on these two main obstacles to healing in patients with type 1 diabetes, Riggs believes, a cure for the disease is within reach.
Creating more cells for more transplants
Teresa Ku, Ph.D., a professor of diabetes and metabolic diseases research, is developing methods to use pancreatic stem cells to generate insulin-producing beta cells for transplant. Her research is aimed at addressing the need for more beta cells from donor pancreases for patients receiving transplant.
Ku has developed a unique and novel method to grow and analyze pancreatic stem cells in culture. Using this method, she and other researchers in her lab were able to find and characterize stem cells isolated from an adult pancreas and generate insulin-expressing cells by giving them nutrients or molecular signals. These findings have been published in two manuscripts in the Proceedings of the National Academy of Sciences, as well as a manuscript in press in The Review of Diabetic Studies.
A collaboration among Ku, Riggs and Wendong Huang, Ph.D., associate professor of molecular diabetes research, has led to the identification of a pathway that activates stem cells to differentiate into specialized cells.
This pathway is a result of epigenetic changes, which means that it is stimulated by changes in gene expression that are not encoded in DNA. The finding, recently accepted for publication in Proceedings of the National Academy of Sciences, may provide a novel approach to manipulating pancreatic stem cell differentiation to promote insulin production and, in so doing, treat diabetes.
Correcting an immune system gone awry
Chih-Pin Liu, Ph.D., professor in the Department of Diabetes and Metabolic Diseases Research, is working to understand how the interplay between two kinds of immune cells leads to diabetes.
Regulatory T cells (Treg) normally keep tight control over effector T cells (Teff), which find and fight invaders. However, in patients with diabetes, Treg cells are outnumbered by abnormal Teff cells — allowing these Teff cells to mount an uncontrolled attack on insulin-producing islet cells. Using this understanding, the focus of Liu’s research is two-pronged: He seeks to improve the function of Treg cells and to better suppress Teff cells.
Recent research, which reflected significant progress in identifying novel molecules critical in regulating the function of Treg cells, was recently highlighted in a journal of the American Diabetes Association. Liu’s research could lead to a treatment that heals patients with diabetes by restoring balance to the immune system.
Reversing autoimmunity to cure diabetes
Much of the current research of Defu Zeng, M.D., professor of diabetes, endocrinology and metabolism, is focused on curing type 1 diabetes by reversing the condition of autoimmunity, which occurs when the immune system, meant to protect the body by attacking invaders, attacks the body instead.
Zeng’s preclinical research has already shown the promise of curing autoimmune-related diabetes through transplantation using mixed chimerism, a combination of both host and donor immune cells. More recently, Zeng conducted research that showed how mixed chimerism eliminated diseased immune cells. He has submitted this study for publication.
And in parallel research, Zeng showed that, after reversing autoimmunity through mixed chimerism, the body can be made to produce mature beta cells that produce insulin. Next steps toward clinical application of this research are further studies in large animals, as well as developing more effective agents to induce mixed chimerism and prepare the patient’s immune system for transplant.
In related research, Zeng seeks to reverse autoimmunity for patients who are prediabetic — which can prevent the onset of diabetes. He recently found that the protein B7H1-Ig can help to do this by driving the growth of protective Treg cells and inducing death in pathogenic Teff cells. He is now working with Riggs to synthetically refine this protein for treatment.
They plan to test the protein’s ability to prevent type 1 diabetes in mouse models, and Zeng is also preparing to submit this research for publication. These new findings advance Zeng’s search for ways to correct diabetes-related immune imbalances.
Understanding complications caused by diabetes
Rama Natarajan, Ph.D., a professor in diabetes, endocrinology and metabolism and director of the Division of Molecular Diabetes Research, is studying mechanisms that drive kidney and vascular complications from diabetes. In one line of research, she is focused on the role that microRNAs (miRNAs) play in mediating the damaging effects of a molecule called TGF-beta, which drives kidney damage. Currently in mouse models, her research holds promise for slowing or stopping kidney disease in people coping with diabetes.
This year, Natarajan published three journal articles on this research. Diabetes featured a study showing that mice genetically deficient in a specific miRNA showed lesser rates of diabetic kidney disease compared to the control mice. Natarajan also published a paper in the premier journal Science Signaling revealing that this specific miRNA is increased under diabetic conditions through novel in-depth molecular mechanisms. This work was also featured in a "Perspectives” article in the same issue of the journal. And in another paper published this year in the Journal of Biological Chemistry, Natarajan showed the mechanisms by which another miRNA leads to renal damage under diabetic conditions.
Natarajan also found that epigenetic changes are involved in the expression of inflammatory and other pathological genes associated with diabetic complications. This research, featured on the cover of Physiological Genomics, presented newly identified groups of genes that are directly affected by hyperglycemia — and could serve as new therapeutic targets. Natarajan recently received a prestigious $2 million grant over five years from the National Institutes of Health to further these investigations.
In another study published in the American Journal of Physiology (Renal), she showed how key genes that promote renal dysfunction under diabetic conditions are regulated by epigenetic changes. These results are especially significant because of Natarajan’s research showing that a drug commonly used to treat diabetic kidney disease was ineffective in reversing all epigenetic marks in mouse models. She believes that to treat patients with disease caused by epigenetic changes, standard treatments need to be supplemented with epigenetic therapies. This study was published in Kidney International.
Natarajan also published a study in Circulation Research that showed for the first time how a recently characterized class of RNAs may control cellular responses to a hormone that is overactive in cardiovascular and heart diseases. This research could lead to targeted therapies for these life-threatening conditions.
Healing diabetes with gene therapy
Patients with type 1 diabetes are dependent on synthetic insulin because their immune systems attack insulin-producing cells. Research is now aimed at engineering surrogate insulin producing cells to enable patients to have a renewable source of insulin and freeing them from daily injections.
John Rossi, Ph.D., Lidow Family Research Chair and professor of molecular and cellular biology, has published a study in the journal Molecular Therapy—Nucleic Acids that explores a novel approach to this solution. He and a team of collaborators used a type of RNA called short-activating RNA oligonucleotides to activate specific genes and cause stem cells to differentiate into insulin-secreting cells.
They found that the differentiated stem cells also expressed several key proteins that are essential for glucose sensitivity and insulin secretion. This research provides a novel potential cure for patients with type 1 diabetes.
Seeing and tracking transplanted cells
John Shively, Ph.D., chair of the Department of Immunology, is developing novel techniques to image beta cells as a way to track progress after transplantation.
Shively is using PET scans, which boast high resolution and sensitivity, to detect small clusters of cells and determine a more precise count of beta cells in the pancreas. He and his collaborators (Zhanhong Wu and Fouad Kandeel, M.D., Ph.D. at City of Hope, as well as Zibo Li and Peter Conti at University of Southern California) are currently focused on developing an agent that targets beta cells so that they light up during PET scan.
The researchers are using a radioactive form of the common element fluorine called F-18 attached to a peptide. This peptide, currently used to treat diabetes and shown to be an excellent agent for targeting beta cells, delivers the fluorine directly to the beta cells. The scientists are currently testing this compound using mouse models of beta cell transplantation.
The imaging technique may help to understand patients’ responses to transplanted islet cells after the procedure and help to ensure successful transplantation.
Curing diabetes independent of diet
Sanjay Awasthi, M.D., professor of diabetes and metabolic diseases research, recently published compelling new research that gained widespread media attention. His paper, featured in the high-impact Journal of Biological Chemistry in August, posits that the RLIP76 protein plays a central role in the development of diabetes, obesity and cancer.
Awasthi has also shown that inhibiting this protein may cure these diseases regardless of diet — currently a significant intervention to manage type 2 diabetes. In his study, mice lacking the protein were resistant to gaining weight, even on a high-fat diet, and had reduced blood sugar, cholesterol and triglyceride levels. This research could lead to drugs that target RLIP76 and cure type 2 diabetes, even without an altered diet.
Tapping nature for cures
Continuing his research in natural products to treat cancer and diabetes, Wendong Huang, Ph.D., has identified berberine, found in several plants, as a potential compound to target disease.
He has found that berberine may activate the receptor TGR5, which improves insulin sensitivity and glucose balance. Because berberine is already Food and Drug Administration-approved, Huang is hopeful that this research will be translated rapidly to the clinic, and that it will provide an innovative and low-cost treatment for patients coping with diabetes.
Diagnosing diabetes through molecular markers
Kevin Ferreri, Ph.D., associate professor of diabetes and metabolic diseases research, is conducting research aimed at improving detection of diabetes. He is focused on identifying biomarkers for diabetes, specifically DNA marks from insulin-producing beta cells.
Already, he's reported the discovery of a unique DNA signature found in insulin-producing cells that is released into the blood when the cells die, such as during the onset of type 1 diabetes. Nearly 70 percent of beta cells die before a patient can be diagnosed with diabetes from current available methods, so testing for this DNA marker could help to detect the disease sooner.
Ferreri is now developing clinical tests for this biomarker to monitor diabetes in patients, as well as tests to detect type 2 diabetes and diabetic complications earlier. He also hopes to translate this research to monitor patients after islet cell transplantation.
Exploring the molecular benefits of exercise
Exercise is a well-known approach to regulate the body use of glucose, and is one of the most effective interventions to stabilize blood sugar levels in patients who are prediabetic or who have type 2 diabetes.
Janice Huss, Ph.D., associate professor of diabetes and metabolic diseases research, has identified a specific estrogen-related receptor (ERR) that may be the reason for this. Her data suggest that ERR-alpha may act as an integrating hub for signaling pathways that are activated during exercise. Over time, the receptor helps to translate repetitive signals into long-term, programmed changes in protein and enzyme levels that reprogram how the body uses glucose.
Huss is now using this premise to understand if targeted activation of the receptor mimics the beneficial effects of endurance exercise — and helps cure diabetes.
Novel therapeutics for type 2 diabetes
Research conducted at City of Hope identified the farnesoid X receptor (FXR), a protein that is highly expressed in the liver and intestine, and which regulates the levels of bile acids in the body. Our research has also explored the connection between FXR and type 2 diabetes, showing that the receptor regulates the use of glucose in the liver.
Continuing these studies, Donna Yu, Ph.D., research scientist, seeks to develop drugs that take advantage of FXR’s role in regulating glucose to treat diabetes. She found that activating FXR created some benefit, but that it also led to the possibility of liver injury.
Now, Yu is taking an alternative approach by exploring compounds as selective modulators that inhibit FXR signaling to target a specific group of genes that regulate glucose. She screened a series of compounds and derivatives, and among them identified DY268 as a promising lead for therapeutic development.
Yu will now use this compound in preclinical studies to further understand the mechanisms of FXR in regulating glucose, with the goal of developing new drugs that block FXR to treat patients with type 2 diabetes.
Developing drugs to treat obesity and diabetes
Continuing the work of the Rabhar laboratory, James Figarola, Ph.D., staff scientist, is studying drugs that activate a protein called AMPK, which plays a role in carbohydrate and fat metabolism.
His focus is on the drug COH-SR4, which the Rabhar lab has shown prevents fat cell development. Figarola tested this compound in diet-induced obese and type 2 diabetic mice, and found that COH-SR4 led to weight loss as well as improved glucose control and insulin resistance.
This promising study suggests that the novel drug may successfully treat obesity and type 2 diabetes.
Tackling one potential cause of obesity in women
Shiuan Chen, Ph.D., chair and professor of cancer biology, is renowned for his studies of aromatase, a protein that converts androgen to estrogen in women.
Currently, aromatase inhibitors are used to treat estrogen-dependent breast cancers, and have shown success in healing women. However, Chen’s research has shown that using these inhibitors can harm women by putting them at risk for obesity, metabolic syndrome and type 2 diabetes. He is now studying the side effects of aromatase inhibitors in women to find ways to combat obesity and insulin resistance before they occur.
In addition, researchers in his lab are screening environmental chemicals that suppress aromatase, and their findings suggest that exposure to these chemicals during critical stages of development could promote obesity and diabetes in women.
Chen’s research promises to benefit women fighting cancer while also addressing serious risk for diabetes and other life-threatening conditions.
Preventing the precursors to diabetes
Hua Yu, Ph.D., professor and associate chair of the Department of Cancer Immunotherapeutics and Tumor Immunology, is advancing her research in STAT3, a protein involved in the dysregulation of the immune system. She recently found that blocking STAT3 in T cells reduces the risk of conditions that lead to type 2 diabetes, including diet-induced obesity, insulin resistance and glucose imbalance, and inflammation in fat tissue. The study was published in the Proceedings of the National Academy of Sciences.
Yu is also studying the use of a gene silencing compound developed at City of Hope called CpG-STAT3 siRNA to silence STAT3 and block diet-induced insulin resistance in mice. She found that targeting a specific pathway called JAK2/STAT3 is a viable approach to treat obesity-related insulin resistance and type 2 diabetes.
Yu and her colleagues are preparing to submit this study for publication — research that could lead to a new therapy to treat patients with type 2 diabetes.
Overcoming obstacles to successful transplant
For islet transplantation to be a viable option for patients, several obstacles still need to be overcome. One is damage to fragile islet cells during transplant, which decreases the number of cells that survive the procedure.
Yoko Mullen, M.D., Ph.D., research professor in the Department of Clinical Diabetes, Endocrinology & Metabolism, has developed a technique in animal models in which the pancreas is coated with a solution that protects islets from damage caused by cold temperatures. Mullen seeks to translate this technique to human transplant.
Another obstacle is failure of newly transplanted islets to graft and grow in their new environment, a difficulty that requires researchers to consider where and how islet cells should be transplanted.
Mullen has made progress in developing hydrogel encapsulated islets to transplant islets subcutaneously, where there is ample space as well as ease for monitoring these islets after transplant. Now, Mullen and her collaborators at UC Irvine are working to address challenges in transplanting islets with hydrogels, including restoring blood flow to islets — critical to their function in monitoring and responding to changes in blood glucose.
Her promising research is providing innovative solutions to the difficulties posed by transplantation.
Detecting complications earlier
Currently, there are no methods to detect and diagnose the dangerous complications caused by diabetes — such as kidney and nerve damage, blindness and hypertension — until symptoms appear. And by this point, complications are often irreversible.
John Termini, Ph.D., professor of molecular medicine, has identified a small molecule called CEdG that could help to detect complications earlier. His research to date has shown that CEdG measures are accurate in determining hyperglycemia in several animal models of type 1 and type 2 diabetes. Over the last few years, Termini and his lab have developed an extremely accurate method to measure CEdG in urine and tissues. By measuring CEdG in tissues, clinicians can understand the impact and stress caused by glucose on specific organs, while measuring the molecule in urine provides an overall picture of whole-body exposure to glucose.
Now, Termini is setting up a clinical study to determine whether CEdG can be used in the clinic to diagnose and monitor patients, as well as predict future complications.
Developing targeted therapies
Zuoming Sun, Ph.D., a professor of immunology, is studying Th17 cells and their role in autoimmunity. This sub-class of T cell stimulates inflammation and, when produced in excess, promotes diabetes. Sun’s research is aimed at understanding and blocking the mechanisms that activate Th17 cells in excess.
Sun previously identified a molecule called RORgammat, required to activate Th17 cells, as a possible target to block Th17-mediated autoimmunity. However, researchers in his lab found that blocking RORgammat activity in mouse models can lead to life-threatening lymphomas originating in the immune system.
Sun is now uncovering critical domains in RORgammat that work only to block Th17 cells. He's also developing targeted drugs that prevent Th17-mediated autoimmune diseases, including diabetes, without causing lymphoma.
Coordinating worldwide islet cell research efforts
Against this research backdrop, City of Hope is the data coordinating center of the Integrated Islet Distribution Program (IIDP), a multiyear initiative to supply high-quality islet cells to diabetes researchers around the world.
In this role, Joyce Niland, Ph.D., the Edward and Estelle Alexander Chair in Information Sciences, and her team were recently awarded an additional five-year, $15 million grant from the National Institutes of Health to help ensure that researchers receive the islet cells they need to pursue diabetes research. Over the past year alone, the IIDP isolated nearly 17 million islets that were distributed in 946 shipments to investigators across North America, Israel and Germany.
Two years ago, the IIDP instituted a pilot program to provide up to 250,000 islets free of charge to unfunded researchers. To date, this program has supported 22 investigators, and 17 of these investigators have now achieved funding to continue their research. In all, research efforts supported by the IIDP at City of Hope have led to the publication of more than 420 high-quality scientific studies — advancing the understanding of diabetes and the development of novel therapies.