By killing off “angry” immune cells that take up residence in obese fat and muscle tissue, researchers have shown that they can rapidly reverse insulin resistance in obese mice.  The findings reported in the October Cell Metabolism, a publication of Cell Press, suggest that treatments aimed at specific subsets of the so-called macrophage cells might offer a very effective new antidiabetic therapy, according to the researchers.

” We used a genetic ‘trick’ that allowed us to rapidly kill these macrophages,” said Jerrold Olefsky of the University of California, San Diego.  “The treatment killed these cells within hours, and insulin resistance simply reversed itself.  It argues strongly that macrophages are causative for the inflammation that leads to diabetes [in those who are obese].”

” The most interesting thing is that this reversal occurs very rapidly,” added Jaap Neels of INSERM in France, who led the work while in Olefsky’s lab.  “Twenty-four hours later the animals’ insulin response had completely normalized.  They were still obese, but no longer insulin resistant.”

Of course, Neels said, the strategy used in the obese mice wouldn’t translate to the clinic directly.  It’s also unclear whether or not it is the same subtype of macrophage cells that invade fat tissue in people who are obese.  Nevertheless, the findings suggest that you would not necessarily need to target all macrophages to have a beneficial effect on the diseases associated with obesity.  That’s critical because “you don’t want to knock out the whole immune system.”

Over the past decade, it has become quite clear that obesity gives rise to a state of chronic, low-grade inflammation that contributes to insulin resistance and type 2 diabetes, the researchers explained.

Olefsky and Neels’ team along with others recently found that a specific subset of macrophages invades obese fat and muscle tissue.  Although little was known about them, those macrophages are defined by a CD11c marker expressed on their surfaces.  They also produce high levels of proinflammatory chemicals that are linked to the development of obesity-associated insulin resistance.

In the new study, the researchers tested the idea that killing those cells would reverse the inflammatory symptoms that come with obesity using a mouse model developed earlier in which the CD11c-expressing macrophages were artificially made susceptible to diphtheria toxin.

They found that treatment with the toxin not only reversed the animals’ resistance to insulin, but also led to a marked decline in inflammatory signs through the body.  The treated animals showed a decline in the CD11c macrophages in both fat and muscle, they confirmed.

” It shows that high triglycerides in muscle don’t necessarily have to lead to insulin resistance as it has been thought—as long as the high lipid levels aren’t accompanied by inflammation,” Neels said.

The obese mice also had less fat in their livers, an important find given the epidemic of obesity-associated fatty liver disease.

If a unique marker can be identified on the macrophages found in human fat tissue, a drug could be designed to take advantage of those features to bind and kill them, Neels said.  Alternatively, it may be possible to convert the macrophage cells into another, less inflammatory type.

Reported in the Oct. 3, 2008 issue of Cell, the findings–from a study in mice–point to a completely new approach to treating and preventing obesity in humans.  The discovery also offers hope for new ways to treat related disorders, such as type 2 diabetes and cardiovascular diseases–the most prevalent health problems in the United States and the rest of the developed world.

Led by Dongsheng Cai, an assistant professor of physiology at the UW School of Medicine and Public Health, the researchers looked specifically at the hypothalamus–the brain structure responsible for maintaining a steady state in the body–and for the first time found that a cell-signaling pathway primarily associated with inflammation also influences the regulation of food intake.  Stimulating the pathway led the animals to increase their energy consumption, while suppressing it helped them maintain normal food intake and body weight.

The research stems from recent explorations into the problem called metabolic inflammation, a by-product of too much food or energy consumption.  Unlike the classical inflammation typically observed in infections, injuries and diseases such as cancer, the metabolic inflammation seen in obesity-related diseases is much milder, doesn’t lead to overt symptoms or cause tissues damage.

“Metabolic inflammation is a chronic, low-grade condition consisting of inflammatory-like responses at the molecular level.  It has many downstream consequences,” says Cai.  “It causes cellular dysfunction, which can decrease the regulation of several physiological processes, including metabolism.”

Scientists believe that metabolic inflammation may be at the core of many chronic, obesity-related metabolic disorders that are so common today, he adds.

Cai and his team zeroed in on NF-kappaB, a protein complex that can be activated specifically by IKKbeta to induce inflammatory reactions in many cell systems.

In earlier studies at Harvard, Cai and colleagues found that the pathway interrupted sugar, fat or protein metabolism in tissues where metabolism typically takes place–liver, fat and skeletal muscle.  Feeding mice high-sugar and high-fat diets activated the pathway in these tissues.

Once he arrived at the SMPH three years ago, Cai began to consider whether metabolic inflammation might affect “higher-up” players in the central nervous system, particularly the hypothalamus.  This brain structure is a critical master regulator of appetite and energy balance, and also controls metabolism in the peripheral tissues he had studied before.  But nobody knew how the hypothalamus might contribute to the development of metabolic diseases such as obesity and diabetes.

“We wanted to learn whether the pathway or pathways underlying metabolic inflamm ation could affect metabolism regulators in the central nervous system,” he says.

In the current study, Cai and his team found first that IKKbeta/NF-kappaB does indeed exist in specific neurons in the hypothalamus.  The pathway is much more abundant in the hypothalamus than in peripheral tissue, and it normally remains inactive in the brain.

The researchers next showed that over-nutrition through high-fat diet feeding activates IKKbeta/NF-kappaB, specifically in neurons in the hypothalamus.

“When we knocked out the IKKbeta gene to suppress NF-kappaB activity in these neurons, the animals were significantly protected from energy over-consumption and obesity development,” Cai says.

The researchers also examined a cell component called the endoplasmic reticulum (ER), shown recently to be involved in metabolic diseases involving over-nutrition, to see if it might play a role in linking over-nutrition to activate IKKbeta/NF-kappaB in the hypothalamus.

“At the intracellular level, when the ER is challenged with over-nutrition, this leads to ER stress, which can push the IKKbeta/NF-kappaB pathway to an active state, although the involved reactions could be quite complicated,” Cai says.

In several experiments, the researchers found that ER stress caused by over-nutrition activated IKKbeta/NF-kappaB in the hypothalamus.  Suppressing ER stress in the central nervous system significantly preserved normal regulation of food intake and prevented obesity.

Cai says there’s still a lot of work to be done.  His group has begun studying IKKbeta/NF-kappaB’s connections to other pathways and regulations in the hypothalamus.

“The ultimate goal will certainly be to identify a selective and effective suppressor of the pathway to target related neurons,” he says.

But Cai continues to look at the big picture, seeking answers to questions such as: “How does the environment connect to the genetics that seem to underlie the obesity epidemic?  What are the key steps that have led to the dramatic rise of diabetes in the past three decades?  And Why can’t the body adjust to changes that have occurred in the way people eat and what they eat?”

Higher levels of urinary Bisphenol A (BPA), a chemical compound commonly used in plastic packaging for food and beverages, is associated with cardiovascular disease, type 2 diabetes and liver-enzyme abnormalities, according to a study in the September 17 issue of JAMA. This study is being released early to coincide with a Food and Drug Administration (FDA) hearing on BPA.

BPA is one of the world’s highest production–volume chemicals, with more than two million metric tons produced worldwide in 2003 and annual increase in demand of 6 percent to 10 percent annually, according to background information in the article. It is used in plastics in many consumer products. “Widespread and continuous exposure to BPA, primarily through food but also through drinking water, dental sealants, dermal exposure, and inhalation of household dusts, is evident from the presence of detectable levels of BPA in more than 90 percent of the U.S. population,” the authors write. Evidence of adverse effects in animals has created concern over low-level chronic exposures in humans, but there is little data of sufficient statistical power to detect low-dose effects. This is the first study of associations with BPA levels in a large population, and it explores “normal” levels of BPA exposure.

David Melzer, M.B., Ph.D., of Peninsula Medical School, Exeter, U.K., and colleagues examined associations between urinary BPA concentrations and the health status of adults, using data from the National Health and Nutrition Examination Survey (NHANES) 2003-2004. The survey included 1,455 adults, age 18 through 74 years, with measured urinary BPA concentrations.

The researchers found that average BPA concentrations, adjusted for age and sex, appeared higher in those who reported diagnoses of cardiovascular diseases and diabetes. A 1-Standard Deviation (SD) increase in BPA concentration was associated with a 39 percent increased odds of cardiovascular disease (angina, coronary heart disease, or heart attack combined) and diabetes.

When dividing BPA concentrations into quartiles, participants in the highest BPA concentration quartile had nearly three times the odds of cardiovascular disease compared with those in the lowest quartile. Similarly, those in the highest BPA concentration quartile had 2.4 times the odds of diabetes compared with those in the lowest quartile.

In addition, higher BPA concentrations were associated with clinically abnormal concentrations for three liver enzymes. No associations with other diagnoses were observed.

“Using data representative of the adult U.S. population, we found that higher urinary concentrations of BPA were associated with an increased prevalence of cardiovascular disease, diabetes, and liver-enzyme abnormalities. These findings add to the evidence suggesting adverse effects of low-dose BPA in animals. Independent replication and follow-up studies are needed to confirm these findings and to provide evidence on whether the associations are causal,” the authors conclude. “Given the substantial negative effects on adult health that may be associated with increased BPA concentrations and also given the potential for reducing human exposure, our findings deserve scientific follow-up.”

Hypoglycemic seizures occur in several diseases, particularly diabetes. In rats (and humans) seizures are induced by excess insulin, which stimulates glucose uptake throughout the body, reducing the amount available to neurons. The substantia nigra pars reticulata (SNR) has been implicated in seizure control: hyperpolarization of SNR neurons is anticonvulsant, whereas increased firing in SNR is proconvulsant. To further investigate the mechanism of hypoglycemic seizures, Velíšek et al. injected insulin into rats that had fasted overnight. Fasting doubled the probability that insulin would induce a seizure and decreased the latency to seizure. But differences in blood glucose levels did not explain the difference. Instead, the proconvulsant effect of fasting was associated with decreased expression of K_ATP channels specifically in the SNR. These channels normally open (causing hyperpolarization) only when ATP levels are low (e.g., during hypoglycemia). Decreased K_ATP expression prevents hyperpolarization of SNR neurons during hypoglycemia, and thus is proconvulsant.

One of the characteristics of type 2 diabetes is insulin resistance, which refers to the inability of cells in the body to respond appropriately to the hormone insulin.  Among the cells in the body that normally respond to insulin are nerves in a region of the brain known as the hypothalamus.  New data, generated in rats, by Hiraku Ono and colleagues, at Albert Einstein College of Medicine, New York, has provided insight into a molecular pathway in the hypothalamus that contributes to the development of insulin resistance.

Insulin plays a key role in controlling the amount of glucose in the body through its ability to make cells, such as liver and fat cells, take up glucose from the blood and store it for future use.  Insulin also prevents liver cells from releasing stored glucose, partly through its effects in the hypothalamus.  In the study, if rats were fed a high-fat diet for a short period of time the ability of insulin to prevent liver cells releasing stored glucose was reduced.  This was associated with both a decrease in insulin-induced signaling and an increase in activation of a protein known as SK6 in the hypothalamus.  The importance of SK6 activation in the hypothalamus in suppressing the ability of insulin to prevent glucose release from liver cells was confirmed by two sets of experiments.  First, it was shown that enforced SK6 activation in the hypothalamus had the same effects as feeding rats a high-fat diet; second, blocking the effects of SK6 activation restored the ability of insulin to prevent glucose release from liver cells, even when rats were fed a high-fat diet.  These data lead the authors to speculate that the earliest stages of diet-induced insulin resistance might be prevented by inhibition of S6K in the hypothalamus.

Uncontrolled blood vessel growth is a key feature of many pathological conditions, including the degenerative diabetic eye disease known as diabetic retinopathy.  Understanding the factors involved in the process is vital to developing treatments for the disease.  In a new study, a team of researchers at Keio University, Japan, has revealed a role for the protein LIF in blood vessel growth in mice.

Specifically, mice lacking LIF were observed to have increased blood vessel growth in many regions of the body, but as this study was focused on the eye, the authors homed in on the increased blood vessel growth in the retina of the eye.  Further analysis showed that mice lacking LIF developed more aberrant blood vessels in a model of retinopathy.  Mechanistically, LIF was found to inhibit the proliferation of brain cells known as astrocytes as well as inhibit their production of a factor known to promote blood vessel growth, VEGF.  It therefore seems that LIF is an important part of the communication between tissues and developing blood vessels, meaning that LIF and the signaling pathway it triggers might serve as a target for new treatment approaches for preventing diabetic retinopathy and other diseases that are associated with uncontrolled blood vessel growth, such as cancer.

UT Southwestern Medical Center researchers have genetically engineered a laboratory mouse in which pancreatic beta cells can regenerate after being induced to die. The new animal model’s regenerative ability may provide future insights into improved treatments of diabetes, which affects millions of Americans.The model, named the PANIC-ATTAC mouse, mimics what occurs in humans with type 1 diabetes, a condition that develops when the body’s immune system destroys pancreatic beta cells, as well as in type 2 diabetes, where beta cells die from working overtime.

After inducing death in the beta cells – which make and release the hormone insulin – the researchers found that the engineered mice’s beta-cell populations can regenerate, which makes the animal useful for studying conditions such as type 1 diabetes, hyperglycemia (high blood sugar) and gestational diabetes.

The animal model is described online and in a future print issue of the journal Diabetes.

“The ability to induce cell death is not novel. The fact that the beta cells regenerate after we kill them is really the new aspect of the model,” said Dr. Philipp Scherer, professor of internal medicine, director of the Touchstone Center for Diabetes Research at UT Southwestern and senior author of the study. “It enables us to see what kind of event or pharmacological intervention might stimulate or enhance the regeneration.”

In the study, the researchers genetically manipulated mature, insulin-positive pancreatic beta cells in the PANIC-ATTAC mice so that these cells would die when they came in contact with a drug. When the researchers stopped administering the drug and allowed the animals to recover, they found that the animals’ beta cells had regenerated and their blood glucose levels returned to normal after two months.

Dr. Scherer said it’s unclear what caused the pancreatic beta cells to regenerate, but uncovering the mechanisms that allow beta cells to rebound in this environment could provide major insights in type 1 diabetes research. He and his colleagues are now developing a way to isolate the cell population that gives rise to the newly emerging beta cells.

About 1 million people, between 5 percent and 10 percent of all diagnosed cases of diabetes, in the U.S. are affected by type 1 diabetes, for which there is no cure or preventive measure.

“This model allows us to get a transcriptional signature, a fingerprint, of how beta cells fend off the pharmaceutical stimulus we provide to prompt cell death,” Dr. Scherer said. “In other words, it provides a way to identify the most critical factors that protect against beta cell death and to potentially find ways to increase these factors in people with type 1 diabetes.”

The key, Dr. Scherer said, is that the process researchers use to kill beta cells is very targeted.

“It creates very little inflammation, so we can eliminate specific cells with minimal collateral damage,” he said. “The other nice aspect is that we can do it in a very dose-dependent way, so we can ablate, or kill, just a few cells, or we can ablate almost all of them.”

Dr. Scherer said this model lends itself to studying conditions of temporary hyperglycemia such as gestational diabetes, a condition in which pregnant women who have never had diabetes develop hyperglycemia. Gestational diabetes usually disappears after pregnancy, but it is not clear whether these transient bouts of elevated glucose can cause permanent damage in the vasculature that persists even after normal glucose levels have been restored.

Dr. Zhao Wang, a postdoctoral researcher at UT Southwestern and lead author of the study, said the strength of the PANIC-ATTAC mouse as a research tool lies partly in the ability to test how specific pharmaceuticals impact beta-cell regeneration.

“We can test which drugs can more rapidly repair the damage,” Dr. Wang said. “We can also test which drugs are protective. That’s probably more important physiologically because it allows us to screen for interventions that could protect beta cells during the early stages of diabetes to slow down and prevent the onset of hyperglycemia.”

High living standards and the life style connected to them seem to promote the development of autoimmune diseases and allergic symptoms. This has lead to the assumption that the immune system begins to overreact to the organism’s own structures or to exogenous non-infectious proteins, i.e. allergens, when it does not have to work hard enough to protect the individual from infections.

The European Union with its Seventh Framework Program has allocated 6 million euros to the University of Helsinki coordinated DIABIMMUNE research project for the years 2008-2013 to establish whether the decrease in the infection load is connected to type 1 diabetes and the emergence of allergies.

The project comprises 12 partners from five countries. The study will include 7 000 children from Finland, Estonia and Russian Karelia in northwestern Russia. In each country the study will follow more than 300 children from birth to their 3rd birthday. In addition, the research will focus on 2 000 children from their third to fifth birthdays.

“Earlier we have studied autoimmune phenomena and allergic responses in Finnish and Russian Karelian school children. Now we are to study infants and toddlers in order to yield new information on the maturation of the immune system and the interaction between the immune system and the environment”, says Professor Mikael Knip from the University of Helsinki.

Based on earlier studies it is known that the incidence of type 1 diabetes is six times higher and the prevalence of celiac disease five times higher among Finnish children than among Russian Karelian children. The HLA gene variants that predispose people to autoimmune diseases are however approximately equally common in both populations. The studies have also revealed that Russian Karelian school children have helicobacter antibodies as signs of earlier infections 15 times more often, Toxoplasma antibodies five times more often, and hepatitis A antibodies 12 times more often than Finnish children. Karelian children also have considerably more often antibodies against the Coxsackie B4 virus, belonging to the enterovirus group, than Finnish children have.

“The differences in the frequency of autoimmune phenomena and allergic responses between Finland and Russian Karelia cannot be due to genetic causes. High living standards and the associated life style appear to promote the development of autoimmune diseases and allergic responses”, Knip says.

The DIABIMMUNE project focuses for example on the development of the intestinal bacterial flora after birth and the effect the living environment has on the composition of the bacterial flora. The research also studies the effect infections have on the maturation of the human immune system and the operation of the white blood cells that regulate immune responses. In addition, the researchers study whether the protection conferred by infections against autoimmune and allergic responses is associated with the overall infection load or due to specific microbes. The project also examines the effect of the child’s nutrition on the maturation of the immune system, the intestinal bacterial flora and the occurrence of infections.

“The diseases we are studying are the most common chronic diseases in children and their impact, both societal and medical, is vast. We are searching for ways to stop these diseases from becoming more frequent and to prevent their development”, Knip says.

Microspheres carrying targeted nucleic acid molecules fabricated in the laboratory have been shown to prevent and even reverse new-onset cases of type 1 diabetes in animal models. The results of these studies were reported by diabetes researchers at the John G. Rangos Sr. Research Center at Children’s Hospital of Pittsburgh of UPMC and Baxter Healthcare Corporation.

In a research study at Children’s Hospital, the scientists injected the microspheres under the skin near the pancreas of mice with autoimmune diabetes. The microspheres were then captured by white blood cells known as dendritic cells which released the nucleic acid molecules within the dendritic cells. The released molecules reprogrammed these cells, and then migrated to the pancreas. There, they turned off the immune system attack on insulin-producing beta cells. Within weeks, the diabetic mice were producing insulin again with reduced blood glucose levels.

Results of the microsphere study are published in the June issue of Diabetes, the journal of the American Diabetes Association.

In type 1 diabetes, T cells from the immune system travel to the pancreas and destroy beta cells, which produce insulin. The scientists – led by Massimo Trucco, MD, and Nick Giannoukakis, PhD – found that the microspheres reprogram dendritic cells to block the signaling mechanism that sends T cells to destroy beta cells. The microsphere research builds on previous research by Drs. Giannoukakis and Trucco in which they used dendritic cells delivered to the pancreas in another method to turn off the immune system’s attack on insulin-producing beta cells, thereby allowing the cells of the pancreas to recover and begin producing insulin again.

Drs. Trucco and Giannoukakis anticipate that the latest research involving microspheres represents a significant improvement over their previous approach to extract (through a process known as leukapheresis) and reprogram the dendritic cells.

“The microspheres prevented the onset of type 1 diabetes and, most importantly, exhibited a capacity to reverse hyperglycemia, suggesting a potential to reverse type 1 diabetes in new-onset patients,” said Dr. Trucco, chief of the Division of Immunogenetics at Children’s. “This novel microsphere approach represents for the first time a vaccine with the potential to suppress and reverse diabetes. This finding holds true promise for clinical testing in people with type 1 diabetes.”

Currently, Drs. Trucco and Giannoukakis are conducting a clinical trial of their leukapheresis-based dendritic cell approach in humans at Children’s. This Phase 1 clinical trial has been approved by the U.S. Food and Drug Administration (FDA).

“Our ultimate goal is to offer this dendritic cell vaccine or microsphere-based therapy to children at risk for or newly diagnosed with type 1 diabetes. We want to make the procedure as safe and comfortable as possible,” Dr. Giannoukakis said.

The trial began late last year and enrollment is ongoing. The study, which plans to enroll a total of 15 adults over age 18 with type 1 diabetes, is expected to conclude later this year.

If the leukapheresis-based approach continues to show exceptional safety, the researchers hope to launch a national clinical trial that will assess the effectiveness of the dendritic cells in pediatric patients to prevent diabetes or reverse the disease right after it is clinically confirmed. At a later date, it is anticipated that Baxter Healthcare will collaborate with Drs. Trucco and Giannoukakis in a clinical trial utilizing the unique microsphere-based approach.

Leukapheresis is a process that allows for the collection of dendritic cell precursors from the patients in the study, which takes two to four hours. After the precursors are collected, they are treated in the lab with specific growth factors that turn them into dendritic cells. The growth factors are also combined with short DNA sequences that specifically block the expression of molecules that are found at the surface of dendritic cells known as CD40, CD80 and CD86. Once these reprogrammed dendritic cells are tested in the lab, they are injected back into the patient. They then orchestrate an anti-diabetic effect by suppressing the activity of T-cells which are responsible for the impairment and destruction of the pancreatic insulin-producing cells.

“Using microspheres will be much less invasive for the patient and much more efficient for clinicians. We wouldn’t need to harvest a patient’s dendritic cells, and it would eliminate the need to genetically reprogram the dendritic cells in a sterile, off-site facility. Instead, the patient would receive the microsphere injection with a small needle in a clinic setting in a matter of minutes,” Dr. Giannoukakis said.