Welcome to the Kahn Laboratory

Our research involves both basic and clinical investigation and is focused on furthering our understanding of the pathophysiology, prevention and treatment of type 2 diabetes and related disorders.

Research:
Our basic science studies focus on the role of islet amyloid in the β-cell loss observed in type 2 diabetes and islet transplantation. These amyloid deposits contain as their unique peptide component islet amyloid polypeptide (IAPP), which misfolds to form amyloid fibrils and induces β-cell death. For this work we perform in vivo and in vitro studies using transgenic mouse models, islet and cell cultures aimed at understanding the cellular mechanisms by which amyloid results in β-cell apoptosis and impaired β-cell function. The ultimate goal is to identify novel approaches to reduce islet amyloidogenesis and its downstream adverse effects.

Our current work is focused on the following:
1.      The innate immune system is intimately involved in amyloid-induced β-cell loss, with macrophages playing a critical role. We have been examining the role of cytokines, including IL-1β and TNF-α, in this process. While large doses of IL-1β clearly induce cell death, we are interested in the effects of more physiological concentrations of the cytokine and the process by which it induces amyloid formation and β-cell loss. We are also studying necroptosis, a novel TNF-α dependent mechanism of cell death, that we have identified to occur with amyloid-induced production of TNF-α. Our goal is to fully delineate how these two cytokines result in cell loss with the ultimate goal to identify approaches to interrupt their action and thereby maintain β-cell number.
2.      Steroidogenic Acute Regulatory Protein (StAR) normally transports cholesterol across the mitochondria for subsequent metabolism to corticosteroids, sex steroids, neurosteroids, oxysterols and bile acids. We have found that StAR expression in β-cell mitochondria is selectively upregulated by amyloid resulting in abnormal mitochondrial function and apoptosis. We are pursuing studies to further understand the physiological role of StAR in the β-cell and to limit its deleterious effects when amyloid is present.
3.      Expression of tissue plasminogen activator (tPA) is also selectively increased by islet amyloid formation. We have found that tPA, which plays an important role in the plasmin system that is responsible for blood clot dissolution, is expressed in macrophages and limits amyloid fibril formation by IAPP by cleaving the peptide to render it non-amyloidogenic. Current work is aimed at developing approaches to increase its activity in order to reduce amyloid formation.
4.      Our efforts to limit islet amyloid formation are using a number of other approaches, many being done in collaboration with scientists at the University of Washington and outside of Seattle. One example is based on the concept that the α-sheet secondary structure of IAPP plays a critical role in both the aggregation and toxicity of soluble oligomers of this fibrillogenic peptide. Using specifically designed peptides with an α-sheet structure, we are studying in vitro and in vivo whether these peptides can preferentially interact with toxic intermediates of IAPP and thereby inhibit aggregation and prevent cell death.

Our clinical research work focuses primarily on the islet β-cell’s role in the development of the dysglycemia that characterizes prediabetes and type 2 diabetes. We have highlighted the importance of considering the magnitude of the insulin response relative to prevailing insulin sensitivity when assessing the adequacy of the β-cell’s response to secretory demand. This approach continues to be used by in our work and has been adopted by many others.

In line with this interest we are collaborating with colleagues interested in the pathophysiology of type 2 diabetes in adults and youth to further our understanding of the development of prediabetes and type 2 diabetes. Interestingly, this work suggests that the pathogenesis of the disease differs in younger and older individuals and that this may be why the progression of dysglycemia and loss of β-cell function is more rapid in youth, resulting in a poorer response to therapies commonly used in adults. Current work focuses on mechanisms that may underlie these differences with the long term goal being to identify approaches that can reduce disease progression in both age groups.

Our basic science studies using animal models of islet amyloid formation have allowed us to develop a PET-based imaging approach that provides a good quantitative measure of amyloid deposition determined by histology. We are now undertaking studies to determine whether this same PET approach using a tracer specific for amyloid in humans can provide insight into the degree of islet damage in humans.

Aside from these studies, we are also participating in a number of multicenter clinical trials the goals of which are to enhance our understanding of the best approaches to intervene in adults to prevent and treat type 2 diabetes. Our expertise in β-cell function is an important component being employed in the design and analyses of these studies.