At left is a healthy islet with many insulin-producing cells (green) and few glucagon-producing cells (red). At right, this situation is altered in a diabetic islet with a heavy preponderance of glucagon-producing cells (red) and very few insulin-producing cells CREDIT UT Southwestern Medical Center.

Blocking cell receptors for glucagon, the counter-hormone to insulin, cured mouse models of diabetes by converting glucagon-producing cells into insulin producers instead, a team led by UT Southwestern reports in a new study. The findings, published online in PNAS, could offer a new way to treat both Type 1 and Type 2 diabetes in people.

More than 34 million Americans have diabetes, a disease characterized by a loss of beta cells in the pancreas. Beta cells produce insulin, a hormone necessary for cells to absorb and use glucose, a type of sugar that circulates in the blood and serves as cellular fuel.

In Type 2 diabetes, the body’s tissues develop insulin resistance, prompting beta cells to die from exhaustion from secreting excess insulin to allow cells to take in glucose. In Type 1 diabetes, which affects about 10 percent of the diabetic population, beta cells die from an autoimmune attack. Both kinds of diabetes lead to severely elevated blood sugar levels that eventually cause a host of possible complications, including loss of limbs and eyesight, kidney damage, diabetic coma, and death.

Most treatments for diabetes focus on insulin, but its counterpart – the hormone glucagon that is produced by alpha cells in the pancreas – has received comparatively little attention, says study leader May-Yun Wang, Ph.D., assistant professor of internal medicine at UTSW. Glucagon binds to receptors on cells in the liver, prompting this organ to secrete glucose. Some recent studies have suggested that depleting glucagon or blocking its receptor can help research animals or humans with diabetes better manage their glucose levels. But how this phenomenon occurs has been unknown.

To answer this question, Wang and her colleagues, including William L. Holland, Ph.D., a former assistant professor of internal medicine at UTSW who is now at the University of Utah, and Philipp E. Scherer, Ph.D., professor of internal medicine and cell biology at UTSW and director of UTSW’s Touchstone Center for Diabetes Research, used monoclonal antibodies – manmade proteins that act like human antibodies and help the immune system identify and neutralize whatever they bind to – against the glucagon receptor in mouse models of diabetes.

In one model, called PANIC-ATTAC (pancreatic islet beta-cell apoptosis through targeted activation of caspase 8), a genetic mutation causes beta cells to selectively die off when these mice receive a chemical treatment. Once these animals’ beta cells were depleted, the researchers administered monoclonal antibodies against the glucagon receptor. Weekly treatment with the antibodies substantially lowered the rodents’ blood sugar, an effect that continued even weeks after the treatments stopped.

Further investigation showed that the number of cells in the pancreas of these animals significantly increased, including beta cells. Searching for the source of this effect, the researchers used a technique called lineage tracing to label their alpha cells. When they followed these alpha cells through rounds of cell divisions, they found that treatment with monoclonal antibodies pushed some of the glucagon-producing alpha cell population to convert into insulin-producing beta cells.

Although the PANIC-ATTAC model shares the same beta cell loss that occurs in both Type 1 and Type 2 diabetes, it’s missing the autoimmune attack that spurs Type 1 diabetes. To see if beta cells could rebound through alpha cell conversion under these circumstances, the researchers worked with a different mouse model called nonobese diabetic (NOD) mice in which their beta cells become depleted through an autoimmune reaction. When these animals were dosed with monoclonal antibodies, beta cells returned, despite active immune cells.

In a third animal model that more closely mimics a human system, the researchers injected human alpha and beta cells into immunodeficient NOD mice – just enough cells to produce sufficient insulin to make the animals borderline diabetic. When these mice received monoclonal antibodies against the glucagon receptor, their human beta cells increased in number, protecting them against diabetes, suggesting this treatment could do the same for people.

Holland notes that being able to push alpha cells to shift to beta cells could be especially promising for Type 1 diabetics. “Even after decades of an autoimmune attack on their beta cells, Type 1 diabetics will still have plentiful amounts of alpha cells. They aren’t the cells in the pancreas that die,” he says. “If we can harness those alpha cells and convert them into beta cells, it could be a viable treatment for anyone with Type 1 diabetes.”

Being able to produce native insulin, adds Wang, could hold significant advantages over the insulin injections and pumps used by both Type 1 and Type 2 diabetics. Eventually, she says, similar monoclonal antibodies could be tested in diabetics in clinical trials.

“Even though Type 1 and Type 2 diabetics try their very best to keep glucose under control, it fluctuates quite massively throughout the day even with the best state-of-the-art pump,” Wang says. “Giving them back their own beta cells could help restore much better natural regulation, greatly improving glucose regulation and quality of life.”

Scherer holds the Gifford O. Touchstone, Jr. and Randolph G. Touchstone Distinguished Chair in Diabetes Research and the Touchstone/West Distinguished Chair in Diabetes Research.

A Stanford research team has developed a way to boost the effectiveness of the insulin injections people with diabetes routinely take to control their blood sugar.

Led by materials scientist Eric Appel, the advance might enable patients with diabetes to take a double-acting shot that contains insulin in combination with a drug based on a second hormone, known as amylin. Amylin plays a synergistic role with insulin to control blood sugar levels after eating in a way that is more effective than insulin alone and mimics what occurs naturally with a meal.

While the amylin-based drug is already commercially available, it is estimated that less than 1 percent of patients with diabetes taking insulin therapy also take this complementary treatment because the two hormones – which work together seamlessly in the body – are too unstable to coexist in the same syringe.

“Taking that second injection with the insulin shot is a real barrier for most patients. Our formulation would allow them to be given together in a single injection or in an insulin pump,” said Appel, senior author of a research paper published May 11 in Nature Biomedical Engineering.

The new technique involves a protective coating that wraps around insulin and amylin molecules and, for the first time, allows them to coexist in a single shot.

“This coating dissolves in the bloodstream, enabling these two important hormones to work together in a way that mimics how they function in healthy individuals,” Appel said.

So far, the researchers have tested the wrapper’s stability in the laboratory, and done preliminary experiments to see how their two-in-one injection works on the most advanced preclinical model – diabetic pigs. But, because both drugs are already on the market and the dual-drug formulation was tested in advanced models, Appel said the team need only demonstrate that their technique is nontoxic in humans to start trials in people, bringing this technology closer to market than most early-stage drugs.

Appel and his collaborators hope this approach could, one day, dramatically increase the use of amylin and lead to improved glucose management for the estimated 450 million people worldwide with either juvenile (type 1) diabetes or adult-onset (type 2) diabetes.

Although few patients with diabetes currently take the amylin-based drug after their insulin injection, those who do experience profound benefits, Appel said. Past clinical data shows that patients taking both lose weight and have better control over their blood sugar. Enhanced diabetes management can reduce the risk of serious health complications, such as renal failure, blindness, heart disease and amputations, all of which loom over anyone with diabetes.

If the wrapper approach makes it possible to combine insulin and amylin in one dose, this would offer patients with diabetes a convenient way to mimic their natural secretion in the human body. In non-diabetics, amylin is secreted from the same cells in the pancreas that produce insulin. Insulin improves the uptake of sugar by cells, removing it from the bloodstream.

For its part, amylin does three things to control blood sugar. First, it stops another hormone, glucagon, from telling the body to release additional sugar that has been stored in the liver. Second, it produces a sense of “fullness” at mealtimes that reduces food intake. Third, it actually slows the uptake of food by the body, reducing the typical spike in blood sugar after a meal. All three are a boon to diabetes care.

To make it possible to pair insulin and amylin in one syringe, the researchers developed a molecular wrapper made of polyethylene glycol, or PEG, a common nontoxic chemical used in everything from cosmetics to laxatives. The Stanford team used a new type of PEG that has a sort of molecular Velcro on the end, called cucurbituril-PEG or CB-PEG. The Velcro-like abilities of CB-PEG enable it to reversibly bind to both insulin and amylin separately, shielding the unstable portions of each molecule from breakdown. Once injected into the body, however, the drugs unbind from the CB-PEG and are free to act unhindered.

“CB-PEG is an entirely new chemical entity,” Appel said.

In lab tests of stability, the researchers heated wrapped and unwrapped insulin to normal body temperature and shook it, a process known as stressed aging. They found that unprotected insulin was stable for just 10 hours in the test tube, but the “PEGylated” insulin was still fully active 100 hours later. Without the wrap, the dual-drug combo fails in just 3 hours.

More impressive, however, is that the co-formulation of PEGylated insulin and amylin remained stable for at least 100 hours, which could be a long enough shelf life to mean that the combination could be delivered by insulin pumps.

In animal studies, the researchers saw significant overlap of the activity of the dual-drug formulation, an important finding that indicates the approach is closely mimicking what happens in a healthy body – including a near-total suppression of glucagon, the hormone that tells the liver to release stored sugar, even though the person has just consumed a meal.

“We’re excited about the results to say the least,” Appel said. Appel has already filed for a patent on the technology.

If the brain reacts sensitively to the hormone, you lose a significant amount of weight, reduce unhealthy abdominal fat and can maintain weight in the long term. If the brain reacts only slightly or not at all to insulin, you only lose some weight at the beginning of the intervention and then gain weight again.

Just where fat is deposited in the body and to what degree a person may benefit from a lifestyle intervention depends, among other things, on how sensitive the brain is to insulin. If the person’s brain responds sensitively to the hormone, a significant amount of weight can be lost, unhealthy visceral fat reduced, and the weight loss can be maintained over the long term. However, If the person’s brain responds only slightly or not at all to insulin, the person only loses some weight at the beginning of the intervention and then experiences weight regain. Over the long term, the visceral fat also increases. These are the results of a long-term study by the German Center for Diabetes Research (DZD), Helmholtz Zentrum München and Tübingen University Hospital which has now been published in Nature Communications.

To which extent body fat has an unhealthy effect depends primarily on where it is stored. If fat accumulates in the abdomen, this is particularly unfavorable. This is because the visceral fat releases numerous neurotransmitters that affect blood pressure, influence the secretion of the hormone insulin and can cause inflammation. This increases the risk of diabetes, cardiovascular disease and certain types of cancer. The subcutaneous fat which accumulates on the buttocks, thighs and hips has no adverse health effects. However, it is still unclear why fat storage does not occur in the same place in all people. Studies in the Tübingen Lifestyle Intervention Program (TULIP) [1] suggest that brain insulin responsiveness could play an important role here. They showed that people with a high insulin sensitivity in the brain benefit significantly more from a lifestyle intervention with a diet rich in fiber and exercise than people with insulin resistance in the brain. Not only did they lose more weight, they also had a healthier fat distribution. But how does insulin sensitivity affect the distribution of body fat and weight in the long term? Researchers from the German Center for Diabetes Research (DZD), Helmholtz Zentrum München and Tübingen University Hospital investigated this question in a long-term study. For this purpose, they recorded the follow-up data of 15 participants over a period of nine years, in which the insulin sensitivity in the brain was determined by magnetoencephalography before the start of a 24-month lifestyle intervention.

High insulin sensitivity associated with reduction in visceral fat and weight

It was found that insulin action in the brain not only determines body weight, but also the distribution of fat in the body. “Subjects with high insulin sensitivity in the brain benefited from the lifestyle intervention with a pronounced reduction in weight and visceral fat. Even after the lifestyle intervention had ended, they only regained a small amount of fat during the nine-year follow-up,” said the head of the study, Professor Martin Heni from Tübingen University Hospital. In contrast, people with brain insulin resistance only showed a slight weight loss in the first nine months of the program. “Afterwards, their body weight and visceral fat increased again during the following months of lifestyle intervention,” said first author PD Dr. Stephanie Kullmann from the IDM.

Since the insulin action in the hypothalamus is crucial for the regulation of peripheral energy metabolism, the researchers also investigated how insulin sensitivity in this area of the brain is related to the distribution of body fat. For this purpose, they examined a cross-sectional cohort of 112 participants. The analysis of the data showed that people with high insulin sensitivity in the hypothalamus form little visceral fat. However, insulin sensitivity has no influence on the mass of subcutaneous fat.

Our study reveals a novel key mechanism that regulates fat distribution in humans. Insulin sensitivity in the brain determines where fat is deposited, “said Heni, summarizing the results. Since visceral fat not only plays a role in the development of type 2 diabetes, but also increases the risk of cardiovascular disease and cancer, the study results may also open up new approaches for treatment options beyond metabolic diseases. The researchers in Tübingen are already working on new therapies to abolish insulin resistance in the brain and thus have a beneficial effect on body fat distribution.