Insulin-Producing Beta Cell Subtypes May Impact Diabetes Treatment

Researchers from the Oregon Stem Cell Center in Portland, Oregon have demonstrated the existence of at least four separate subtypes of human insulin-producing beta cells that may be important in the understanding and treatment of diabetes.

“This study marks the first description of several different kinds of human insulin producing beta cells,” said Markus Grompe of the Oregon Stem Cell Center at Oregon Health Science University. “Some of the cells are better at releasing insulin than others, whereas others may regenerate quicker. Therefore, it is possible that people with different percentages of the subtypes are more prone to diabetes. Further understanding of cell characteristics could be the key to uncovering new treatment options, as well as the reason why some people are diabetic and others are not.”

Diabetes mellitus affects more than 29 million people in the United States. There are two main types of diabetes mellitus, type I and type II. Type I diabetes mellitus is caused by insufficient production of insulin. Type II diabetes mellitus is caused by insulin resistance or the inability of the body to properly respond to the insulin produced by the body. Type I diabetes mellitus results from dysfunction or loss of insulin producing beta cells in the endocrine portion of the pancreas. Insulin is a hormone that helps the body keep normal blood sugar levels, and incorporate sugar in the bloodstream into cells to grow and repair tissues. Previously, only a single variety of beta cell was known to exist. However, using human pancreatic islets, or clusters of up to 4,000 cells, Grompe and colleagues identified a method to identify and isolate four distinct types of beta cells. They also found that hundreds of genes were differently expressed between cell subtypes and that these distinct beta cell subtypes produced different amounts of insulin.

All type 2 diabetics had abnormal percentages of the subtypes, suggesting a possible role in the disease process. Additional research is needed to determine how different forms of diabetes – and other diseases – affect the new cell subtypes, as well as how researchers may take advantage of these differences for medical treatment.

This work was published in: Craig Dorrell et al., “Human islets contain four distinct subtypes of β cells,” Nature Communications, 2016; 7: 11756 DOI: 10.1038/ ncomms11756.


University of Iowa Team Creates Insulin-Producing Cells from Skin Cells

A research team from the University of Iowa has designed a protocol that can create insulin-producing cells that help normalize blood-sugar levels in diabetic mice from skin cells. This discovery represents one of the first steps toward developing patient-specific cell replacement therapy for Type 1 diabetes. This research, which was led by Nicholas Zavazava from the department of internal medicine, was published in the journal PLoS ONE.

Zavazava and his coworker used human skin cells taken from punch biopsies and reprogrammed them to into induced pluripotent stem cells. These induced pluripotent stem cells were then differentiated in culture into pancreatic insulin-producing beta cells.

In culture, Zavazava’s cell made insulin in response to increased concentrations, but when they were implanted into diabetic mice, these cells responded to glucose, secreted insulin and worked to lower the blood-sugar levels in the mice to normal or near-normal levels.

Mind you, these induced pluripotent stem cell-derived beta cells were not as effective as pancreatic cells in controlling blood sugar levels, according to Zavazava in a UI news release. However, Zavazava and his team views the cells’ response in mice as an “encouraging first step” toward the goal of generating effective insulin-producing cells that potentially could be used to not just treat but cure Type 1 diabetes in humans.

“This raises the possibility that we could treat patients with diabetes with their own cells,” Zavazava said. “That would be a major advance, which will accelerate treatment of diabetes.”

Zavazava is also a member of UI’s Fraternal Order of Eagles Diabetes Research Center. This center is one of several groups whose aim is to create an alternative source of insulin-producing cells that can replace the pancreatic beta cells that die off in people with Type 1 diabetes.

According to the UI news release, this study is the first to use human induced pluripotent stem cells instead of embryonic stem cells to generate insulin-producing pancreatic beta cells. This protocol has the advantage of creating beta cells from a patient’s own cells include. This would eliminate the need to wait for a donor pancreas, since pancreas transplants are an option for treating Type 1 diabetes, but the demand for transplants is much greater than the availability of organs from deceased donors. The use of induced pluripotent stem cells would also eliminate the need for transplant patients to take immunosuppressive drugs. Finally, the use of induced pluripotent stem cells would also avoid the ethical concerns with treatments based on embryonic stem cells.

Preventing the Onset of Type 1 Diabetes

Diabetes researchers at Saint Louis University have discovered a way to prevent the onset of Type I diabetes mellitus in diabetic mice. This strategy involves inhibiting the autoimmune processes that result in the destruction of the insulin-secreting pancreatic beta cells.

Type I diabetes is a life-long disease that results from insufficient production of the vital anabolic hormone insulin. In most cases of Type I diabetes mellitus, the body’s immune system destroys insulin-producing beta cells, and this insulin deficiency causes high blood sugar levels, also known as hyperglycemia. Treatments for the disease require daily injections of insulin.

Dr. Thomas Burris, chair of the university’s pharmacological and physiological science department, and his colleagues, have published their results in the journal Endocrinology. IN this paper, they report a procedure that could potentially prevent the onset of the disease rather than just treating the symptoms

“None of the animals on the treatment developed diabetes even when we started treatment after significant beta cell damage had already occurred,” Burris explained in a prepared statement. “We believe this type of treatment would slow the progression of type I diabetes in people or potentially even eliminate the need for insulin therapy.”

A group of immune cells known as lymphocytes come in two main forms: B lymphocytes, which secrete the antibodies that bind to foreign cells and neutralize them, and T cells, which recognize foreign substances and regulate the immune response. There are several different types of T lymphocytes, but for the purposes of this discussion, two specific subtypes of T lymphocytes seem to be responsible for the onset of Type I diabetes. T “helper cells” that have the CD4 protein on their surfaces, and T “cytotoxic “ cells have the CD8 protein on their cell surfaces seem to play a role in the onset of Type I diabetes, but a third subtype of T lymphocyte has remained a bit of an enigma for some time. This subtype of T lymphocytes is a subcategory of CD4 T cells and secretes a protein called “interleukin 17,” and is, therefore, known as TH17.

Dr. Burris and his collaborators from the Department of Molecular Therapeutics at the Scripps Research Institute have been examining TH17 cells for some time and they came upon a pair of nuclear receptors that play a crucial role in the development of TH17 cells. Could hamstringing the maturation of TH17 cells delay the onset of Type 1 diabetes mellitus?

Burris and others targeted these receptors by using drugs that bound to them and prevented them from working. This prevented the maturation of the TH17 T lymphocytes. When two nuclear receptors, Retinoid-related orphan receptors alpha (ROR-alpha) and Gamma-t (ROR-gamma-t) were inhibited, they prevented the autoimmune response that destroyed the beta cells.

To block these ROR alpha and gamma t receptors, Burris and others used a selective ROR alpha inhibitor and a gamma t inverse agonist called SR1001 that was developed by Dr. Burris. These drugs significantly reduced diabetes in the mice that were treated with it.

These findings show that TH17 cells play a significant role in the onset of Type I diabetes, and suggest that the use of drugs like these that target this cell type may offer a new treatment for the illness.

According to the American Diabetes Association, only 5% of people with diabetes have the Type I form of the disease, which was previously known as juvenile diabetes because it is usually diagnosed in children and young adults. The organization said that over one-third of all research they conduct is dedicated to projects relevant to type 1 diabetes.

Digestive Cells Converted into Insulin-Secreting Cells

By switching off a single gene, Columbia Medical Center scientists have converted cells from the digestive tract into insulin-secreting cells. This suggests that drug treatments might be able to convert gut cells into insulin-secreting cells.

Senior author Domenico Accili said this of this work: “People have been talking about turning one cell into another for a long time, but until now we hadn’t gotten to the point of creating a fully functional insulin-producing cell by the manipulation of a single target.”

Accili’s work suggests that lost pancreatic beta cells might be replaced by retraining existing cells rather than transplanting new insulin-secreting cells. For nearly two decades, scientists have been trying to differentiate a wide variety of stem cells into pancreatic beta cells to treat type 1 diabetes. In type 1 diabetes, the patient’s insulin-producing beta cells are destroyed, usually by the patient’s own immune system. The patient becomes dependent on insulin shots in order to survive.

Without insulin, cells have no signal to take up sugar and metabolize it. Also muscles and the liver do not take up amino acids and make protein, and the body tends to waste away, ravaged by high blood sugar levels that progressively and relentlessly damage it without the means to repair this damage.

Insulin-producing beta cells can be made in the lab from several different types of stem cells, but the resulting beta cells often do not possess all the properties of naturally occurring beta cells.

This led Accili and others to attempt to transform existing cells into insulin-secreting beta cells. In previous work, Accili and others demonstrated that mouse intestinal cells could be converted into insulin-secreting cells (see Talchai C, et al., Nat Genet. 2012 44(4):406-12), This recent paper demonstrates that a similar technique also works in human intestinal cells.

The gene of interest, FOXO1, is indeed present in human gut endocrine progenitor and serotonin-producing cells. In order to determine in FOXO1 inhibition could induce the formation of insulin-secreting cells, Accili and others used human induced pluripotent stem cells (iPSCs) and small “gut organoids,” which are small balls of gut tissue that grow in culture.

Inhibition of FOXO1 by either introducing a mutant version of the gene that encoded a protein that soaked up all the wild-type protein or by using viruses that forced the expression of a small RNA that prevented the expression of the FOXO1 gene caused loss of FOXO1 activity. FOXO1 inhibition promoted the generation of insulin-positive cells within the gut organoids that express all the genes and proteins normally found in mature pancreatic β-cells. These transdifferentiated cells also released “C-peptide,” which is a byproduct of insulin production, in response to drugs that drive insulin secretion (insulin secretagogues). Furthermore, these cultured insulin-secreting cells and survive when transplanted into mice where they continue to secrete insulin in response to increased blood sugar concentrations.

The findings of Accili and his colleagues provide some evidence that gut-targeted FOXO1 inhibition or transplantation of cultured gut organoids made from iPSCs could serve as a source of insulin-producing cells to treat human diabetes.

This is a remarkable piece of research, but there is one thing that troubles me about it. If the patient’s immune system has been sensitized to beta cells, making new beta cells will simply give the immune system something else to attack. It seems to me that retraining to immune system needs to be done first before replacement of the beta cells can ever hope to succeed.

Encapsulated Stem Cells to Treat Diabetes

A research group from the Sanford-Burnham Medical Research Institute in La Jolla, San Diego, California has used pluripotent stem cells to make insulin-secreting pancreatic beta cells that are encapsulated in a porous capsule from which they secrete insulin in response to rising blood glucose levels.

“Our study critically evaluates some of the potential pitfalls of using stem cells to treat insulin-dependent diabetes,” said Pamela Itkin-Ansari, an adjunct assistant professor with a joint appointment at UC San Diego. “We have shown that encapsulated hESC-derived pancreatic cells are able to produce insulin in response to elevated glucose without an increase in the mass or their escape from the capsule. This means that the encapsulated cells are both fully functional and retrievable.”

For this particular study, Itkin-Ansari and her colleagues used glowing cells to ensure that their encapsulated cells stayed in the capsule. To encapsulate the cells, this group utilized a pouch-like encapsulation device made by TheraCyte, Inc. that features a bilaminar polytetrafluoroethylene (PTFE) membrane system. This pouch surrounds the cells and protects from the immune system of the host while giving cells access to nutrients and oxygen.

With respect to the cells, making insulin-secreting beta cells from embryonic stem cell lines have met with formidable challenges. Not only are beta cells differentiated from embryonic stem cells poorly functional, but upon transplantation, they tend to be fragile and poorly viable.

To circumvent this problem, encapsulation technology was tapped to protect donor cells from the ravages of the host immune system. However, an additional advance made by Itkin-Ansari and her colleagues is that when they encapsulated islet-precursor cells, derived from embryonic stem cells, these cells survived and differentiated into pancreatic beta cells. In fact, islet progenitor cells turn out to be the ideal cell type for encapsulation, since they are heartier, and differentiate into beta cells quite efficiently when encapsulated.

In their animal model tests, these cells remained encapsulated for up to 150 days. Also, as an added bonus, because the progenitor cells develop glucose responsiveness without significant changes in mass, they do not outgrow their capsules.

In order to properly get this protocol to work in humans, Itkin-Ansari and her group has to scale up the size of their capsules and the number of cells packaged into them. Another nagging question is, “How long will an implanted capsule last in a human patient?

“Given the goals and continued successful results, I expect to see the technology become a treatment option for patients with insulin-dependent diabetes,” said Itkin-Ansari.

To date, Itkin-Ansari and others have been able to successfully treat diabetic mice. The problem with these experiments is that they mice were made diabetic by treatment with a drug called beta-alloxan, which destroys the pancreatic beta cells. Human type 1 diabetic patients have an immune system that is sensitized to beta cells. Even though the encapsulation shields the beta cells from contact with the immune system, will this last in human patients with an aggressive immune response against their own beta cells? It seems to me that induced pluripotent cells made from the patient’s own cells would be a better choice in this case than an embryonic stem cell line.

Nevertheless, this is a fine piece of research for diabetic patients.

Directly Reprogramming Gut Cells into Beta Cells to Treat Diabetes

Type 1 diabetes mellitus results from destruction of insulin-producing beta cells in the pancreas. Diabetics have to give themselves routine shots of insulin. The hope that stem cells offer is the production of cells that can replace the lost beta cells. “We are looking for ways to make new beta cells for these patients to one day replace daily insulin injections,” says Ben Stanger, MD, PhD, assistant professor of Medicine in the Division of Gastroenterology, Perelman School of Medicine at the University of Pennsylvania.

Some diabetics have had beta cells from cadavers transplanted into their bodies to replace the missing beta cells. Such a procedure shows that replacement therapy is, in principle possible. Therefore, transplanting islet cells to restore normal blood sugar levels in type 1 diabetics could treat and even cure disease. Unfortunately, transplantable islet cells are in short supply, and stem cell-based approaches have a long way to go before they reach the clinic. However, Stanger and his colleagues have tried a different strategy for treating type 1 diabetes. “It’s a powerful idea that if you have the right combination of transcription factors you can make any cell into any other cell. It’s cellular alchemy,” comments Stanger.

New research from Stanger and a postdoctoral fellow in his laboratory, Yi-Ju Chen that was published in Cell Reports, describes the production of new insulin-making cells in the gut of laboratory animals by introducing three new transcription factors. This experiment raises the prospect of using directly reprogrammed adult cells as a source for new beta cells.

In 2008, Stanger and others in Doug Melton’s laboratory used three beta-cell reprogramming factors (Pdx1, MafA, and Ngn3, collectively called PMN) to convert pancreatic acinar cells (the cells in the pancreas that secrete enzymes rather than hormones) into cells that had many of the features of pancreatic beta cells.

Following this report, the Stanger and his team set out to determine if other cells types could be directly reprogrammed into beta cells. “We expressed PMN in a wide spectrum of tissues in one-to-two-month-old mice,” says Stanger. “Three days later the mice died of hypoglycemia.” It was clear that Stanger and his crew were on to something. Further work showed that some of the mouse cells were making way too much extra insulin and that killed the mice.

When the dead mice were autopsied, “we saw transient expression of the three factors in crypt cells of the intestine near the pancreas,” explained Stanger.

They dubbed these beta-like, transformed cells “neoislet” cells. These neoislet cells express insulin and show outward structural features akin to beta cells. These neoislets also respond to glucose and release insulin when exposed to glucose. The cells were also able to improve hyperglycemia in diabetic mice.

Stanger and his co-workers also figured out how to turn on the expression of PMN in only the intestinal crypt cells to prevent the deadly whole-body hypoglycemia side effect that first killed the mice.

In culture, the expression of PMN in human intestinal ‘‘organoids,’ which are miniature intestinal units grown in culture, also converted intestinal epithelial cells into beta-like cells.

“Our results demonstrate that the intestine could be an accessible and abundant source of functional insulin-producing cells,” says Stanger. “Our ultimate goal is to obtain epithelial cells from diabetes patients who have had endoscopies, expand these cells, add PMN to them to make beta-like cells, and then give them back to the patient as an alternate therapy. There is a long way to go for this to be possible, including improving the functional properties of the cells, so that they more closely resemble beta cells, and figuring out alternate ways of converting intestinal cells to beta-like cells without gene therapy.”

This is hopefully a grand start to what might be a cure for type 1 diabetes.

Umbilical Cord Stem Cells Normalize Blood Glucose Levels in Diabetic Mice

Diabetes mellitus results from an insufficiency of insulin (Type 1 diabetes) or an inability to properly respond to insulin (Type 2 diabetes). Type 1 diabetes is caused by an attack by the patient’s own immune system on their pancreatic beta cells, which synthesize and secrete insulin. It is a disease characterized by inflammation in the pancreas. This suggests that abatement of inflammation in the pancreas might provide relief and delay the onset of diabetes.

Mesenchymal stem cells isolated from umbilical cord connective tissue, which is also known as Wharton’s jelly (WJ-MSCs), have the ability to reverse inflammatory destruction and might provide a way to delay or even reverse the onset of Type 1 diabetes.

To test this possibility, Jianxia Hu, Yangang Wang, and their colleagues took 60 non-obese diabetic mice and divided them into four groups: a normal control group, a normal diabetic group, a WJ-MSCs prevention group that was treated with WJ-MSCs before the onset of diabetes, and a WJ-MSCs treatment group that was treated with WJ-MSCs after the onset of diabetes.

After their respective treatments, the onset time of diabetes, levels of fasting plasma glucose (FPG), fed blood glucose levels and C-peptide (an indication of the amount of insulin synthesized), regulation of cytokines, and islet cells were examined and evaluated.

After WJ-MSCs infusion, fasting and fed blood glucose levels in WJ-MSCs treatment group decreased to normal levels in 6-8 days and were maintained for 6 weeks. The levels of fasting C-peptide of the WJ-MSC-treated mice was higher compared to diabetic control mice. In the WJ-MSCs prevention group, WJ-MSCs protected mice from the onset of diabetes for 8-weeks, and the fasting C-peptide in this group was higher compared to the other two diabetic groups.

Other comparisons between the WJ-MSC-treated group and the diabetic control group, showed that levels of regulatory T-cells (that down-regulate autoinflammation), were high and levels of pro-inflammatory molecules such as IL-2, IFN-γ, and TNF-α. The degree of inflammation in the pancreas was also examined, and pancreatic inflammation was depressed, especially in the WJ-MSCs prevention group.

These experiments show that infusions of WJ-MSCs can down-regulate autoimmunity and facilitate the recovery of islet β-cells whether given before or after onset of Type 1 Diabetes Mellitus. THis suggests that WJ-MSCs might be an effective treatment for Type 1 Diabetes Mellitus.

See March 2014 edition of the journal Endocrine.