pancreas
Science, Serendipity, and Art
Posted on by Lawrence Tabak, D.D.S., Ph.D.
Fractals are complex geometric patterns repeated at progressively smaller scales. You’ll find them throughout nature. That includes in the 3D structures and shapes of tissues throughout our bodies, from the bones in our skulls down to the blood vessels in our feet. But the fractal pattern above isn’t from a precisely patterned human tissue. It comes from some unexpected biochemistry that formed the stunning pattern on its own.
In fact, the exact source for this fractal pattern reminiscent of peacock feathers isn’t known. It turned up out of the blue (and green) in a sample that had been sitting around on the shelf for some time. The original image appeared in black and white, but the colors added post-collection help to highlight the fractal pattern of a sample including an essential hormone produced in the pancreas. The hormone is called islet amyloid polypeptide (IAPP).
Also known as amylin, IAPP plays many important roles in our bodies, including the feeling of fullness after a meal. But the amino acid chains that make up IAPP also are prone to forming abnormal clumps of misfolded polypeptides (a long name for proteins) known as amyloids. Much like the amyloid plaques in the brains of people with Alzheimer’s disease, misfolded IAPP amyloids in people with type 2 diabetes also can damage insulin-producing beta cells in the pancreas and make controlling their blood sugar levels even more difficult.
This unusual image comes from graduate students Bryan Bogin and Matthew Steinsaltz. They study the biophysics and biochemistry of protein folding and misfolding in the lab of Zachary Levine, Yale School of Medicine, New Haven, CT. The Levine lab recently moved to the Altos Labs San Diego Institute. However, Bogin and Steinsaltz continue to conduct their studies at Yale.
The two conduct in-solution experiments and molecular simulations to elucidate the precise conditions and triggers that can lead otherwise normal polypeptide chains to fold up incorrectly and wreak havoc as they do in diabetes and other diseases. When Steinsaltz was learning how to use transmission electron microscopy (TEM), a technique in which an electron beam captures images including detailed molecular-level structures, Bogin handed over an assortment of IAPP samples in different solution conditions from some of his past experiments for a look.
In those microscopy images, they expected to see long, linear fibrils consisting of IAPP polypeptides. While that’s indeed what they saw in most of the samples, this one was the exception. It was such a remarkable image that they submitted it in the Biophysical Society’s 2022 Art of Science Image Contest, where it took the top prize.
Bogin and Steinsaltz say they still can’t explain the source or meaning behind these unusual fractal patterns. But they do continue to conduct experiments to understand how various polypeptides implicated in health and disease misfold to form destructive aggregates. This striking image may not hold the answers they seek, but it is an inspiring reminder that the path to making groundbreaking biomedical discoveries will have many beautiful surprises along the way.
Links:
Type 2 Diabetes (National Institute of Diabetes and Digestive and Kidney Diseases/NIH)
Zachary Levine Lab (Yale School of Medicine, New Haven, CT)
Art of Science Image Contest (Biophysical Society, Rockville, MD)
NIH Support: National Institute on Aging
Artificial Pancreas Improves Blood Glucose Control in Young Kids with Type 1 Diabetes
Posted on by Lawrence Tabak, D.D.S., Ph.D.
Last week brought some great news for parents of small children with type 1 diabetes (T1D). It involved what’s called an “artificial pancreas,” a new type of device to monitor continuously a person’s blood glucose levels and release the hormone insulin at the right time and at the right dosage, much like the pancreas does in kids who don’t have T1D.
Researchers published last week in the New England Journal of Medicine [1] the results of the largest clinical trial yet of an artificial pancreas technology in small children, ages 2 to 6. The data showed that their Control-IQ technology was safe and effective over several weeks at controlling blood glucose levels in these children. In fact, the new device performed better than the current standard of care.
Two previous clinical trials of the Control-IQ technology had shown the same in older kids and adults, age 6 and up [2,3], and the latest clinical trial, one of the first in young kids, should provide the needed data for the U. S. Food and Drug Administration (FDA) to consider whether to extend the age range approved to use this artificial pancreas. The FDA earlier approved two other artificial pancreas devices—the MiniMed 770G and the Insulet Omnipod 5 systems—for use in children age 2 and older [4,5].
The Control-IQ clinical trial results are a culmination of more than a decade-long effort by the NIH’s National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) and many others to create technologies, such as an artificial pancreas, to improve blood glucose control. The reason is managing blood glucose levels remains critical for the long-term health of people with T1D.
What exactly is an artificial pancreas? It consists of three fully integrated components: a glucose monitor, an insulin pump, and a computer algorithm that allows the other two components to communicate. This automation frees people with T1D from checking their blood glucose levels multiple times a day and from many insulin dosing decisions, though they still interact with the system at mealtimes.
In this clinical trial, led by Marc D. Breton, University of Virginia School of Medicine, Charlottesville, researchers tested their Control-IQ technology (manufactured by Tandem Diabetes Care, San Diego, CA), also known as a hybrid closed-loop control system. Thanks to an algorithm developed at the University of Virginia Center for Diabetes Technology, insulin doses are administered automatically every few minutes based on readings from a continuous glucose monitor.
But treating younger children with T1D presents its own set of age-specific challenges. Younger kids generally require smaller doses of insulin more frequently. They also tend to have a more unpredictable schedule with lots of small snacks and random bursts of physical activity.
On top of all that, these young children have a tougher time than kids a few years older when it comes to understanding their own needs and letting the adults around them know when they need help. For all these reasons, young children with T1D tend to spend a greater proportion of time than older kids or adults do with blood glucose levels that are higher, or lower, than they should be. The hope was that the artificial pancreas might help to simplify things.
To find out, the trial enrolled 102 volunteers between ages 2 and 6. Sixty-eight were randomly assigned to receive the artificial pancreas, while the other 34 continued receiving insulin via either an insulin pump or multiple daily injections. The primary focus was on how long kids in each group spent in the target blood glucose range of 70 to 180 milligrams per deciliter, as measured using a continuous glucose monitor.
During the trial’s 13 weeks, participants in the artificial pancreas group spent approximately three more hours per day with their blood glucose in a healthy range compared to the standard care group. The greatest difference in blood glucose control was seen at night while the children should have been sleeping, from 10 p.m. to 6 a.m. During this important period, children with the artificial pancreas spent 18 percent more time in normal blood glucose range than the standard care group. That’s key because nighttime control is especially challenging to maintain in children with T1D.
Overall, the findings show benefits to young children similar to those seen previously in older kids. Those benefits also were observed in kids regardless of age, racial or ethnic group, parental education, or family income.
In the artificial pancreas group, there were two cases of severe hypoglycemia (low blood glucose) compared to one case in the other group. One child in the artificial pancreas group also developed diabetic ketoacidosis, a serious complication in which the body doesn’t have enough insulin. These incidents, while unfortunate, happened infrequently and at similar rates in the two groups.
Interestingly, the trial took place during the COVID-19 pandemic. As a result, much of the training on use of the artificial pancreas system took place virtually. Breton notes that the success of the artificial pancreas under these circumstances is an important finding, especially considering that many kids with T1D live in areas that are farther from endocrinologists or other specialists.
Even with these clinical trials now completed and a few devices on the market, there’s still more work to be done. The NIDDK has plans to host a meeting in the coming months to discuss next steps, including outstanding research questions and other priorities. It’s all very good news for people with T1D, including young kids and their families.
References:
[1] Trial of hybrid closed-loop control in young children with type 1 diabetes. Wadwa RP, Reed ZW, Buckingham BA, DeBoer MD, Ekhlaspour L, Forlenza GP, Schoelwer M, Lum J, Kollman C, Beck RW, Breton MD; PEDAP Trial Study Group. N Engl J Med. 2023 Mar 16;388(11):991-1001.
[2] A randomized trial of closed-loop control in children with type 1 diabetes. Breton MD, Kanapka LG, Beck RW, Ekhlaspour L, Forlenza GP, Cengiz E, Schoelwer M, Ruedy KJ, Jost E, Carria L, Emory E, Hsu LJ, Oliveri M, Kollman CC, Dokken BB, Weinzimer SA, DeBoer MD, Buckingham BA, Cherñavvsky D, Wadwa RP; iDCL Trial Research Group. N Engl J Med. 2020 Aug 27;383(9):836-845.
[3] Six-month randomized, multicenter trial of closed-loop control in type 1 diabetes. Brown SA, Kovatchev BP, Raghinaru D, Lum JW, Buckingham BA, Kudva YC, Laffel LM, Levy CJ, Pinsker JE, Wadwa RP, Dassau E, Doyle FJ 3rd, Anderson SM, Church MM, Dadlani V, Ekhlaspour L, Forlenza GP, Isganaitis E, Lam DW, Kollman C, Beck RW; N Engl J Med. 2019 Oct 31;381(18):1707-1717.
[4] MiniMed 770G System-P160017/S076. U. S. Food and Drug Administration, December 23, 2020.
[5] FDA authorizes Omnipod 5 for ages 2+ in children with type 1 diabetes. Juvenile Diabetes Research Foundation news release, August 22, 2022
Links:
Type I Diabetes (National Institute of Diabetes and Digestive and Kidney Diseases/NIH)
Artificial Pancreas (NIDDK)
Marc Breton (University of Virginia, Charlottesville)
NIH Support: National Institute of Diabetes and Digestive and Kidney Diseases
How COVID-19 Can Lead to Diabetes
Posted on by Dr. Francis Collins
Along with the pneumonia, blood clots, and other serious health concerns caused by SARS-CoV-2, the COVID-19 virus, some studies have also identified another troubling connection. Some people can develop diabetes after an acute COVID-19 infection.
What’s going on? Two new NIH-supported studies, now available as pre-proofs in the journal Cell Metabolism [1,2], help to answer this important question, confirming that SARS-CoV-2 can target and impair the body’s insulin-producing cells.
Type 1 diabetes occurs when beta cells in the pancreas don’t secrete enough insulin to allow the body to metabolize food optimally after a meal. As a result of this insulin insufficiency, blood glucose levels go up, the hallmark of diabetes.
Earlier lab studies had suggested that SARS-CoV-2 can infect human beta cells [3]. They also showed that this dangerous virus can replicate in these insulin-producing beta cells, to make more copies of itself and spread to other cells [4].
The latest work builds on these earlier studies to discover more about the connection between COVID-19 and diabetes. The work involved two independent NIH-funded teams, one led by Peter Jackson, Stanford University School of Medicine, Palo Alto, CA, and the other by Shuibing Chen, Weill Cornell Medicine, New York. I’m actually among the co-authors on the study by the Chen team, as some of the studies were conducted in my lab at NIH’s National Human Genome Research Institute, Bethesda, MD.
Both studies confirmed infection of pancreatic beta cells in autopsy samples from people who died of COVID-19. Additional studies by the Jackson team suggest that the coronavirus may preferentially infect the insulin-producing beta cells.
This also makes biological sense. Beta cells and other cell types in the pancreas express the ACE2 receptor protein, the TMPRSS2 enzyme protein, and neuropilin 1 (NRP1), all of which SARS-CoV-2 depends upon to enter and infect human cells. Indeed, the Chen team saw signs of the coronavirus in both insulin-producing beta cells and several other pancreatic cell types in the studies of autopsied pancreatic tissue.
The new findings also show that the coronavirus infection changes the function of islets—the pancreatic tissue that contains beta cells. Both teams report evidence that infection with SARS-CoV-2 leads to reduced production and release of insulin from pancreatic islet tissue. The Jackson team also found that the infection leads directly to the death of some of those all-important beta cells. Encouragingly, they showed this could avoided by blocking NRP1.
In addition to the loss of beta cells, the infection also appears to change the fate of the surviving cells. Chen’s team performed single-cell analysis to get a careful look at changes in the gene activity within pancreatic cells following SARS-CoV-2 infection. These studies showed that beta cells go through a process of transdifferentiation, in which they appeared to get reprogrammed.
In this process, the cells begin producing less insulin and more glucagon, a hormone that encourages glycogen in the liver to be broken down into glucose. They also began producing higher levels of a digestive enzyme called trypsin 1. Importantly, they also showed that this transdifferentiation process could be reversed by a chemical (called trans-ISRIB) known to reduce an important cellular response to stress.
The consequences of this transdifferentiation of beta cells aren’t yet clear, but would be predicted to worsen insulin deficiency and raise blood glucose levels. More study is needed to understand how SARS-CoV-2 reaches the pancreas and what role the immune system might play in the resulting damage. Above all, this work provides yet another reminder of the importance of protecting yourself, your family members, and your community from COVID-19 by getting vaccinated if you haven’t already—and encouraging your loved ones to do the same.
References:
[1] SARS-CoV-2 infection induces beta cell transdifferentiation. Tang et al. Cell Metab 2021 May 19;S1550-4131(21)00232-1.
[2] SARS-CoV-2 infects human pancreatic beta cells and elicits beta cell impairment. Wu et al. Cell Metab. 2021 May 18;S1550-4131(21)00230-8.
[3] A human pluripotent stem cell-based platform to study SARS-CoV-2 tropism and model virus infection in human cells and organoids. Yang L, Han Y, Nilsson-Payant BE, Evans T, Schwartz RE, Chen S, et al. Cell Stem Cell. 2020 Jul 2;27(1):125-136.e7.
[4] SARS-CoV-2 infects and replicates in cells of the human endocrine and exocrine pancreas. Müller JA, Groß R, Conzelmann C, Münch J, Heller S, Kleger A, et al. Nat Metab. 2021 Feb;3(2):149-165.
Links:
COVID-19 Research (NIH)
Type 1 Diabetes (National Institute of Diabetes, Digestive and Kidney Disorders/NIH)
Jackson Lab (Stanford Medicine, Palo Alto, CA)
Shuibing Chen Laboratory (Weill Cornell Medicine, New York City)
NIH Support: National Institute of Diabetes and Digestive and Kidney Diseases; National Human Genome Research Institute; National Institute of General Medical Sciences; National Cancer Institute; National Institute of Allergy and Infectious Diseases; Eunice Kennedy Shriver National Institute of Child Health and Human Development
Insulin-Producing Organoids Offer Hope for Treating Type 1 Diabetes
Posted on by Dr. Francis Collins
For the 1 to 3 million Americans with type 1 diabetes, the immune system destroys insulin-producing beta cells of the pancreas that control the amount of glucose in the bloodstream. As a result, these individuals must monitor their blood glucose often and take replacement doses of insulin to keep it under control. Such constant attention, combined with a strict diet to control sugar intake, is challenging—especially for children.
For some people with type 1 diabetes, there is another option. They can be treated—maybe even cured—with a pancreatic islet cell transplant from an organ donor. These transplanted islet cells, which harbor the needed beta cells, can increase insulin production. But there’s a big catch: there aren’t nearly enough organs to go around, and people who receive a transplant must take lifelong medications to keep their immune system from rejecting the donated organ.
Now, NIH-funded scientists, led by Ronald Evans of the Salk Institute, La Jolla, CA, have devised a possible workaround: human islet-like organoids (HILOs) [1]. These tiny replicas of pancreatic tissue are created in the laboratory, and you can see them above secreting insulin (green) in a lab dish. Remarkably, some of these HILOs have been outfitted with a Harry Potter-esque invisibility cloak to enable them to evade immune attack when transplanted into mice.
Over several years, Doug Melton’s lab at Harvard University, Cambridge, MA, has worked steadily to coax induced pluripotent stem (iPS) cells, which are made from adult skin or blood cells, to form miniature islet-like cells in a lab dish [2]. My own lab at NIH has also been seeing steady progress in this effort, working with collaborators at the New York Stem Cell Foundation.
Although several years ago researchers could get beta cells to make insulin, they wouldn’t secrete the hormone efficiently when transplanted into a living mouse. About four years ago, the Evans lab found a possible solution by uncovering a genetic switch called ERR-gamma that when flipped, powered up the engineered beta cells to respond continuously to glucose and release insulin [3].
In the latest study, Evans and his team developed a method to program HILOs in the lab to resemble actual islets. They did it by growing the insulin-producing cells alongside each other in a gelatinous, three-dimensional chamber. There, the cells combined to form organoid structures resembling the shape and contour of the islet cells seen in an actual 3D human pancreas. After they are switched on with a special recipe of growth factors and hormones, these activated HILOs secrete insulin when exposed to glucose. When transplanted into a living mouse, this process appears to operate just like human beta cells work inside a human pancreas.
Another major advance was the invisibility cloak. The Salk team borrowed the idea from cancer immunotherapy and a type of drug called a checkpoint inhibitor. These drugs harness the body’s own immune T cells to attack cancer. They start with the recognition that T cells display a protein on their surface called PD-1. When T cells interact with other cells in the body, PD-1 binds to a protein on the surface of those cells called PD-L1. This protein tells the T cells not to attack. Checkpoint inhibitors work by blocking the interaction of PD-1 and PD-L1, freeing up immune cells to fight cancer.
Reversing this logic for the pancreas, the Salk team engineered HILOs to express PD-L1 on their surface as a sign to the immune system not to attack. The researchers then transplanted these HILOs into diabetic mice that received no immunosuppressive drugs, as would normally be the case to prevent rejection of these human cells. Not only did the transplanted HILOs produce insulin in response to glucose spikes, they spurred no immune response.
So far, HILOs transplants have been used to treat diabetes for more than 50 days in diabetic mice. More research will be needed to see whether the organoids can function for even longer periods of time.
Still, this is exciting news, and provides an excellent example of how advances in one area of science can provide new possibilities for others. In this case, these insights provide fresh hope for a day when children and adults with type 1 diabetes can live long, healthy lives without the need for frequent insulin injections.
References:
[1] Immune-evasive human islet-like organoids ameliorate diabetes. [published online ahead of print, 2020 Aug 19]. Yoshihara E, O’Connor C, Gasser E, Wei Z, Oh TG, Tseng TW, Wang D, Cayabyab F, Dai Y, Yu RT, Liddle C, Atkins AR, Downes M, Evans RM. Nature. 2020 Aug 19. [Epub ahead of publication]
[2] Generation of Functional Human Pancreatic β Cells In Vitro. Pagliuca FW, Millman JR, Gürtler M, Segel M, Van Dervort A, Ryu JH, Peterson QP, Greiner D, Melton DA. Cell. 2014 Oct 9;159(2):428-39.
[3] ERRγ is required for the metabolic maturation of therapeutically functional glucose-responsive β cells. Yoshihara E, Wei Z, Lin CS, Fang S, Ahmadian M, Kida Y, Tseng T, Dai Y, Yu RT, Liddle C, Atkins AR, Downes M, Evans RM. Cell Metab. 2016 Apr 12; 23(4):622-634.
Links:
Type 1 Diabetes (National Institute of Diabetes and Digestive and Kidney Diseases/NIH)
Pancreatic Islet Transplantation (National Institute of Diabetes and Digestive and Kidney Diseases)
“The Nobel Prize in Physiology or Medicine 2012” for Induced Pluripotent Stem Cells, The Nobel Prize news release, October 8, 2012.
Evans Lab (Salk Institute, La Jolla, CA)
NIH Support: National Institute of Diabetes and Digestive and Kidney Diseases; National Cancer Institute
Study in Africa Yields New Diabetes Gene
Posted on by Dr. Francis Collins
When I volunteered to serve as a physician at a hospital in rural Nigeria more than 25 years ago, I expected to treat a lot of folks with infectious diseases, such as malaria and tuberculosis. And that certainly happened. What I didn’t expect was how many people needed care for type 2 diabetes (T2D) and the health problems it causes. Surprisingly, these individuals were generally not overweight, and the course of their illness seemed different than in the West.
The experience inspired me to join with other colleagues at Howard University, Washington, DC, to help found the Africa America Diabetes Mellitus (AADM) study. It aims to uncover genomic risk factors for T2D in Africa and, using that information, improve understanding of the condition around the world.
So, I’m pleased to report that, using genomic data from more than 5,000 volunteers, our AADM team recently discovered a new gene, called ZRANB3, that harbors a variant associated with T2D in sub-Saharan Africa [1]. Using sophisticated laboratory models, the team showed that a malfunctioning ZRANB3 gene impairs insulin production to control glucose levels in the bloodstream.
Since my first trip to Nigeria, the number of people with T2D has continued to rise. It’s now estimated that about 8 to 10 percent of Nigerians have some form of diabetes [2]. In Africa, diabetes affects more than 7 percent of the population, more than twice the incidence in 1980 [3].
The causes of T2D involve a complex interplay of genetic, environmental, and lifestyle factors. I was particularly interested in finding out whether the genetic factors for T2D might be different in sub-Saharan Africa than in the West. But at the time, there was a dearth of genomic information about T2D in Africa, the cradle of humanity. To understand complex diseases like T2D fully, we need all peoples and continents represented in the research.
To begin to fill this research gap, the AADM team got underway and hasn’t looked back. In the latest study, led by Charles Rotimi at NIH’s National Human Genome Research Institute, in partnership with multiple African diabetes experts, the AADM team enlisted 5,231 volunteers from Nigeria, Ghana, and Kenya. About half of the study’s participants had T2D and half did not.
As reported in Nature Communications, their genome-wide search for T2D gene variants turned up three interesting finds. Two were in genes previously linked to T2D risk in other human populations. The third involved a gene that codes for ZRANB3, an enzyme associated with DNA replication and repair that had never been reported in association with T2D.
To understand how ZRANB3 might influence a person’s risk for developing T2D, the researchers turned to zebrafish (Danio rerio), an excellent vertebrate model for its rapid development. The researchers found that the ZRANB3 gene is active in insulin-producing beta cells of the pancreas. That was important to know because people with T2D frequently have reduced numbers of beta cells, which compromises their ability to produce enough insulin.
The team next used CRISPR/Cas9 gene-editing tools either to “knock out” or reduce the expression of ZRANB3 in young zebrafish. In both cases, it led to increased loss of beta cells.
Additional study in the beta cells of mice provided more details. While normal beta cells released insulin in response to high levels of glucose, those with suppressed ZRANB3 activity couldn’t. Together, the findings show that ZRANB3 is important for beta cells to survive and function normally. It stands to reason, then, that people with a lower functioning variant of ZRANB3 would be more susceptible to T2D.
In many cases, T2D can be managed with some combination of diet, exercise, and oral medications. But some people require insulin to manage the disease. The new findings suggest, particularly for people of African ancestry, that the variant of the ZRANB3 gene that one inherits might help to explain those differences. People carrying particular variants of this gene also may benefit from beginning insulin treatment earlier, before their beta cells have been depleted.
So why wasn’t ZRANB3 discovered in the many studies on T2D carried out in the United States, Europe, and Asia? It turns out that the variant that predisposes Africans to this disease is extremely rare in these other populations. Only by studying Africans could this insight be uncovered.
More than 20 years ago, I helped to start the AADM project to learn more about the genetic factors driving T2D in sub-Saharan Africa. Other dedicated AADM leaders have continued to build the research project, taking advantage of new technologies as they came along. It’s profoundly gratifying that this project has uncovered such an impressive new lead, revealing important aspects of human biology that otherwise would have been missed. The AADM team continues to enroll volunteers, and the coming years should bring even more discoveries about the genetic factors that contribute to T2D.
References:
[1] ZRANB3 is an African-specific type 2 diabetes locus associated with beta-cell mass and insulin response. Adeyemo AA, Zaghloul NA, Chen G, Doumatey AP, Leitch CC, Hostelley TL, Nesmith JE, Zhou J, Bentley AR, Shriner D, Fasanmade O, Okafor G, Eghan B Jr, Agyenim-Boateng K, Chandrasekharappa S, Adeleye J, Balogun W, Owusu S, Amoah A, Acheampong J, Johnson T, Oli J, Adebamowo C; South Africa Zulu Type 2 Diabetes Case-Control Study, Collins F, Dunston G, Rotimi CN. Nat Commun. 2019 Jul 19;10(1):3195.
[2] Diabetes mellitus in Nigeria: The past, present and future. Ogbera AO, Ekpebegh C. World J Diabetes. 2014 Dec 15;5(6):905-911.
[3] Global report on diabetes. Geneva: World Health Organization, 2016. World Health Organization.
Links:
Diabetes (National Institute of Diabetes ad Digestive and Kidney Diseases/NIH)
Diabetes and African Americans (Department of Health and Human Services)
Why Use Zebrafish to Study Human Diseases (Intramural Research Program/NIH)
Charles Rotimi (National Human Genome Research Institute/NIH)
NIH Support: National Human Genome Research Institute; National Institute of Diabetes and Digestive and Kidney Diseases; National Institute on Minority Health and Health Disparities
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