Research - 2005
Resistin: Role in Obesity-Related Cardiovascular Disease
Robert L. Judd, Ph.D.
Associate Professor, Chair
Boshell Diabetes & Metabolic Diseases Research Program
Obesity and diabetes have reached epidemic proportions in the U.S., with an estimated 60% of Americans being either overweight or obese. Alarmingly, this number is continuing to increase in both adults and children of all ethnic and cultural backgrounds. There are both direct and indirect associations between obesity and the development of cardiovascular disease. Therefore, the urgency to rapidly discover the factor(s) that link these conditions is on the rise. The long-term objective of this project is to understand the pathophysiologic mechanisms that are involved in cardiovascular metabolism and function, which may ultimately lead to cardiovascular disease. The recently discovered adipocyte-derived factor, resistin, which is thought to play a role in the development of insulin resistance, may provide a link between obesity/diabetes and cardiovascular disease. This project will determine the effect of resistin on cardiovascular function and metabolism, which is important because altered cardiac metabolism and function are hallmark characteristics of cardiovascular disease. Collectively, these outcomes will establish the basic cellular and molecular mechanisms of resistin-induced cardiovascular pathophysiology. This is expected to have positive effects on human health, because it will allow development of new pharmacological strategies targeted toward resistin and possibly other adipose tissue-derived factors.
Acupuncture for Treatment of Diabetic Neuropathy
Andrew Ahn, MD
Clinical Research Fellow
Harvard Medical School
Diabetic neuropathy is a common diabetic complication that affects nearly 30% of all people with diabetes. It is often characterized as burning and tingling and is considered to be the most symptomatically disturbing complication of diabetes. The present medical treatments for this disorder are generally recognized as inadequate: they occasionally provide partial relief but are commonly accompanied by side effects such as somnolence and constipation. Out of all the complementary and alternative medical (CAM) treatments available, acupuncture is one of the most promising for those suffering from diabetic neuropathy pain. Both animal studies and preliminary human studies have begun to produce evidence that acupuncture may not only reduce symptoms but also reverse some of the nerve damage seen in neuropathy something no approved medication has been able to do at this point. In order for the medical community to adopt acupuncture as a bonafide treatment, Dr. Ahn’s study aims to overcome three obstacles to being accepted by mainstream medicine: lack of clinical evidence, need for plausible mechanisms of action, and determination of which style works best. While a strategy that simultaneously addresses all three of these problems is needed, it has never been undertaken. This pilot study will measure the clinical effects of both Japanese and traditional Chinese acupuncture, in addition to pilot testing placebo controls. The Joslin Diabetes Center has agreed to provide free nerve conduction studies in cooperation with this study and Rey Laboratory for Nonlinear Dynamics in Medicine has agreed to analyze the physiologic data. This grant proposal aims to obtain the pilot data necessary to apply for a NIH and NCCAM (National Center for Complementary Alternative Medicine) grant that would fund a larger, more definitive, clinical and mechanistic study. This project is also seen as a step toward building a unique collaboration between clinical and scientific researchers at Harvard Medical School, the Joslin Diabetes Center, and CAM practitioners at the New England School of Acupuncture to develop new treatments benefiting patients suffering from diabetic neuropathy.
Endogenous mechanism for the regulation of cytokine-induced nitric oxide signaling in the islets
Hwyda Arafat, MD, PhD
Thomas Jefferson University
Transplantation of the pancreatic islets has long been considered a potential curative treatment for diabetes. However, the results of several clinical trials showed that most transplant recipients failed to achieve complete insulin independence. Very recently, a new immunosuppressive regimen in Edmonton, Canada has resulted in unprecedented success in achieving insulin independence with transplanted islets. Despite this success, some problems still persist and influence the outcome of islet transplantation. Transplanted islets are extremely sensitive to the injurious effect of substances that are released by the recipient immune cells (T-lymphocytes and macrophages). This results in early islet cell dysfunction and possibly death of the transplanted tissue. Experiments have shown that those injurious substances disturb insulin secretion from beta cell lines and whole islets through overproduction of the enzyme inducible nitric oxide synthase (iNOS). This leads to the production of toxic amounts of nitric oxide (NO). NO affects beta cell function by inducing cell death and suppressing glucose stimulated insulin release. Inhibition of NO has been shown to promote islet graft survival. Dr. Arafat is exploring a novel islet-related protein called osteopontin (OPN) as a potential regulator of NO production in the pancreatic islets. Prior experiments on many tissues have shown that OPN regulates NO production by inhibition of iNOS. Dr. Arafat plans to test whether OPN is able to regulate iNOS protein and gene expression levels and iNOS activity in the islets, and she will also investigate whether OPN, as a result of NO regulation, is able to improve insulin secretion from the islets. These studies offer hope for new therapeutic strategies to overcome islet damage early after islet transplantation.
Contribution of Tumor Necrosis Factor-a to Diabetic Heart Failure
Gregory L. Brower, D.V.M., Ph.D.
Research Assistant Professor
Diabetes, secondary to obesity, is reaching epidemic proportions in the U.S., and congestive heart failure (CHF) is one of the leading causes of death among people with diabetes. Patients with insulin resistance or type 2 diabetes have a particularly high risk for heart failure and a poor prognosis once they develop heart failure. Myocardial remodeling consisting of left ventricular hypertrophy and dilatation is also a significant risk factor for subsequent development of CHF. Over the last decade Dr. Brower’s laboratory has linked mast cells to myocardial remodeling. The underlying mechanism by which mast cells most likely contribute to diabetes is the induction and release of proinflammatory cytokines. Recent work by Dr. Brower and others indicate that the cytokine TNF-a also plays an integral role in myocardial remodeling, and TNF-a is also linked to the development of insulin resistance. Therefore, it is likely that TNF-a is playing a central role in the pathogenesis of CHF in patients with diabetes. However, no studies investigating this intriguing possibility have been performed. Thus, the overall objective of this proposal is to investigate the relationship between mast cells, proinflammatory cytokines and the development of diabetic heart failure. In the studies proposed for this project, Dr. Brower will examine the overall hypothesis that mast cell mediated elevations in the TNF-a contribute to the pathologic cardiovascular and renal remodeling and end organ damage responsible for the development of diabetic heart failure. It is expected that these studies will provide insight into pharmacologic approaches to prevent or attenuate the progressive myocardial and renal remodeling responsible for CHF.
Endothelial Dysfunction in Children with Obesity and Type 2 Diabetes and in Children with Type 1 Diabetes
Michael J. Haller, M.D.
Pediatric Endocrinology Fellow
University of Florida
The incidence of both obesity and type 2 diabetes has risen to epidemic proportions in children in the U.S. In addition, the incidence of Type 1 diabetes continues to rise. These conditions are all associated with a markedly increased risk of early morbidity and mortality from cardiovascular disease in the future. With type 1 and type 2 diabetes it is important to determine whether these children have early signs of endothelial dysfunction compared to healthy controls. Since endothelial dysfunction is an early finding in the process of atherosclerosis, noninvasive measurements of endothelial function, including brachial artery reactivity, radial artery tonometry, and pulse wave velocity, are valuable tools that have been proven to accurately assess cardiovascular risk. Unfortunately, there have been no studies to date evaluating endothelial dysfunction in children with diabetes and there have been no studies looking at the effects of lipid-lowering or insulin sensitizing medications on endothelial dysfunction in children. Dr. Haller’s project will study groups of children with both type 1 and type 2 diabetes with these noninvasive tests to determine whether there is a difference in endothelial function between obese children, those with type 2 diabetes, normal weight children, and children who have type 1 diabetes. The results of all ultrasound findings will then be correlated with serum markers, such as homocysteine and C-reactive protein, associated with cardiovascular disease. The results of this project will then determine how aggressively children with diabetes should be treated with any drugs. If Dr. Haller’s research demonstrates a difference in endothelial function between children with diabetes and controls, then future intervention studies will be implemented in an attempt to evaluate pharmacologic interventions to improve blood vessel function in children with diabetes and hopefully decrease the risk of future cardiovascular disease.
Mindfulness-Based Stress Reduction for Patients with Type 2 Diabetes Mellitus: Effects on Glycemic Control and Health Related Quality of Life
Diane Reibel, Ph.D.
Research Associate Professor
Thomas Jefferson University Hospital
The increasing prevalence of type 2 diabetes mellitus, with its associated health and economic consequences, necessitates that all effective management tools be utilized to control blood glucose levels. Evidence suggests that chronic stress may be a contributing factor in the development of type 2 diabetes and also a contributor to poor health outcomes. However, the potentially significant benefit of stress management on glycemic control in patients with diabetes has not been adequately studied. Mindfulness-Based Stress Reduction (MBSR) is a proven, clinical group intervention that is patient centered and educational. The core of the program involves training in mindfulness meditation, a practice that calms the mind, relaxes the body and enables one to respond skillfully to stress rather than react automatically. Mindfulness and other meditation practices have been shown to improve blood pressure, lower stress hormones, reduce the progression of atherosclerosis and enhance immune function. MSBR has been shown to reduce pain and other medical symptoms, lower anxiety and depression, and increase vitality and well-being among several patient populations. However, MBSR has not been studied in a diabetic population. Dr. Reibel plans to conduct a pilot study which will assess the potential clinical effectiveness of a twelve week MBSR program for patients with type 2 diabetes mellitus on oral medications. Factors which will be evaluated include Hemoglobin A1C, fasting blood glucose, blood lipids, blood pressure, and health-related quality of life issues including anxiety and depression. If MBSR is found to be effective, it will offer people with diabetes a low-cost, non-pharmacological, adjunctive treatment for improving their medical health and quality of life.
Statins as preventive therapy for the mesangial proliferation and hyperfiltration in early stage 2 diabetic mice
Steven C. Sansom Ph.D.
University of Nebraska Medical Center
Inhibitors of 30-hydroxy-3-methylglutaryl CoA reductase (statins) have been found to reduce the progression of cardiovascular disease by mechanisms other than those attributed to lowering cholesterol. Recently, statins have been shown to reduce proliferation of vascular smooth muscle cells and prevent the high glucose-induced proliferation of glomerular mesangial cells. Dr. Sansom’s laboratory has recently demonstrated that C57BI/6 mice, fed a high fat (45% kCal) diet for 12 weeks, develop type 2 diabetes mellitus (DM) as determined by elevated fasting insulin (5 fold increase) and fasting glucose levels (150 mg%). Moreover, these mice develop early-stage diabetic nephropathy. This was the first demonstration in mice that a diet-induced type 2 diabetes condition also expressed the hyperfiltration phase previously observed in type 1 diabetes. Angiotensin converting enzyme (ACE) inhibitors, the current therapy of choice, will retard but not prevent hyperfiltration and subsequent diabetic nephropathy. However, stimulation of eNOS, a demonstrated effect of statins, may be more beneficial alone or have a complementary beneficial effect with ACE inhibitors. Dr. Sansom’s project will focus on pharmacological therapy for the reduction of hyperfiltration and prevention of diabetic nephropathy in type 2 diabetes. The mouse model affords the advantage of studying the influence of statins on mesangial hyperplasia in vivo and in vitro. The specific aims of this project are: 1) Determine if simvastatin is beneficial, either alone or with ACE inhibitors, in preventing the hyperfiltration, mesangial expansion and subsequent nephropathy observed in type 2 mice 2) Determine if simvastatin prevents the high glucose/high insulin evoked mesangial proliferation in vitro. 3) Determine if simvastatin stimulates eNOS and nitric oxide accumulation in glomerular mesangial cells in culture. If this new therapy plan can prevent the hyperfiltration phase then the chances of progression to diabetic nephropathy will be reduced, which will mean less need for transplant or dialysis therapy.
Treatment of Diabetes Mellitus with Gene Therapy
Douglas Sobel, MD
Professor of Pediatrics
Georgetown University Children’s Medical Center
The goal of this research study is to develop a means to inject a gene construct which will allow non-human primates with diabetes mellitus to again have glucose regulated insulin secretion, that is - a cure of their diabetes. A gene construct with a rodent regulator has been developed by Dr. Sobel's collaborator, Dr. J.W. Yoon, that cures diabetes when injected into diabetic rats and mice by allowing liver cells to make insulin in response to alterations of blood glucose. Because this treatment has never been demonstrated to cure diabetes in non-human primates or in any other animals larger than rodents, Dr. Sobel hopes to develop this mode of gene therapy for use in humans. A major aim of the study is to determine if the transfer of gene construct produces functional insulin activity to improve glucose utilization or reverse the diabetic state of insulin deficiency. Specifically, does gene construct transfer:
1) decrease exogenous daily insulin requirement
2) cause a non-insulin requiring state, i.e. cure
3) improve the body's handling of a glucose load
4) improve glycemic control (which is also dependent on the exogenous insulin administration)
Information obtained in this study will make it possible to understand:
1) the required dose of gene construct which may be considered to perform human studies to cure diabetes
2) the duration of insulin gene expression or cure of the diabetic state, the potential toxicities from this therapy
3) the immunologic responses to the gene construct (rAAV) which may be important to the ability of administering repeated doses of the rAAV
4) the potential toxicity of using this therapy Thus this work will provide a basis for future studies for exploring the possibility of a human trial to cure diabetes with gene therapy.
Time-Dependent Effects of Free Fatty Acids on the Regulation of Glucose Production in Type 2 Diabetes Mellitus
Julia Tonelli, MD
Albert Einstein College of Medicine
Bronx, NY 10461
This clinical research project examines the metabolic regulation of glucose production in type 2 diabetes. In the fasting state, the liver is capable of producing large amounts of glucose to maintain key bodily functions. A sudden rise in plasma glucose causes an abrupt decrease in the amount of glucose being produced by the liver in non-diabetic individuals. The lack of this normal regulation in individuals with type 2 diabetes contributes to further worsening of their elevated plasma glucose levels. It is noteworthy that free fatty acid (FFA) levels are substantially elevated in individuals with type 2 diabetes, and that such elevations could stimulate glucose production even in the presence of elevated plasma glucose. Furthermore, our preliminary data suggests that lowering free fatty acid levels in type 2 diabetes subjects results in a dramatic restoration of glucose-induced suppression of glucose production. Since inappropriate elevations in glucose production contribute importantly to hyperglycemia in type 2 diabetes, understanding the role played by increased free fatty acid levels should give rise to novel treatment strategies to improve hyperglycemia in type 2 diabetes. Reducing circulating levels of fatty acids offers a potentially promising approach to suppress glucose production by the liver when plasma glucose levels are already elevated. Dr. Tonelli will examine the impact of modest increases in FFA availability on the regulation of the glucose production using a dual experimental approach: elevating plasma FFA levels in non-diabetic subjects to type 2 diabetes levels with infusion of a lipid emulsion, and lowering FFA to non-diabetic levels in type 2 subjects by infusing nicotinic acid.
Identification of the Forkhead-related transcription factor that mediates the insulin responsiveness of the plasminogen activator inhibitor type 1 gene
Frederick M. Stanley, Ph.D.
Associate Professor of Pharmacology
NYU School of Medicine
New York, NY 10016
Plasminogen activator inhibitor type 1 is a serum protein whose primary role was thought to be the inhibition of the urokinase type and tissue type plasminogen activators (uPA and tPA). A triumvirate of proteins, uPA, its receptor, uPAR and PAI-1 regulates and cell-cell interaction, cell mobility and basement membrane remodeling. uPA and uPAR are the major effectors in this system, but PAI-1 is the major regulator. PAI-1 is elevated in both type 1 and type 2 diabetes. Elevated PAI-1, both systemic (in the blood) and locally produced were correlated with all of the complications of diabetes. In addition, diabetes causes a pseudo inflammatory state in which mediators of inflammation such as tumor necrosis factor alpha (TNFa) are increased. Dr. Stanley has identified a region of the PAI-1 gene that controls its over production in response to insulin, oxidizing conditions and TNFa. It is known that the increase caused by TNFa and oxidants is mediated by a pair of proteins called AP-1 that regulate PAI-1 from one part of this control region. Insulin’s action is mediated by a different protein that Dr. Stanley has identified as a member of the Forkhead family of proteins. The focus of this research project is to isolate that protein so that it can be determined how it is controlled by insulin and how it may interact with AP-1. A number of state-of-the-art techniques will be used to accomplish this goal. If Dr. Stanley can determine how insulin regulates this protein, it may be then possible to devise ways to normalize it in diabetes.