News & Research

University of Connecticut Storrs, Connecticut

Structural and Biophysical Mechanisms of Amylin Toxicity

General Research Subject: Type 2 Diabetes

Focus: Clinical Therapeutics/New Technology\Pharmacologic Treatment of Diabetes or its Complications, Genetics\Type 2 Diabetes, Islet Biology\Metabolic Regulation

Type of Grant: Basic Science

Project Start Date: January 1, 2010

Project End Date: December 31, 2012

Research Description

Type 2 diabetes affects over 100 million people worldwide and is thought to cost upward of $130 billion dollars a year to treat in the US alone. The hormone amylin which regulates metabolism appears to have key roles in the disease by misfolding into a toxic structure. Our research is aimed at understanding the structures which lead to toxicity and the forces that allow the toxic structures to form. A better understanding of these aspects of the disease could lead to new approaches for its treatment.

Researcher Profile

What area of diabetes research does your project cover? What role will this particular project play in preventing, treating and/or curing diabetes? 

Our work focuses on establishing how the endocrine hormone amylin (also known as islet amyloid polypeptide or IAPP) contributes to type 2 diabetes.  Amylin is a hormone made in the pancreas that regulates metabolism. In particular, its effects together with insulin are to reduce glucose levels in the blood. In patients with type 2 diabetes amylin levels are raised initially but fall as the disease progresses to stages where the pancreatic beta-cells that make amylin and insulin stop working. Amylin was originally discovered in pancreatic fibrillar amyloid deposits that occur in over 90% of the patients with type 2 diabetes. It is thought that during the course of the disease these fibrillar aggregates of amylin, or perhaps smaller oligomeric precursors, destroy the beta-cells that make amylin and insulin. Amyloid fibrils are abnormal protein aggregates that play a central role not only in type 2 diabetes but in diseases such as Alzheimer's, Parkinson's and Huntington's, amongst others. A common theme in these diseases is the abnormal association of proteins into long string-like 'fibril' structures in which molecules pair through a beta-sheet hydrogen-bonded network that runs along the length of the fibril. That amyloid fibrils from different diseases share common features suggests that they may exert their pathological effects through similar mechanisms, perhaps by disrupting the membrane envelopes of their target cells. Our work aims to identify the progression of intermediates that develop during the aggregation of amylin into fibrils and to establish the structural and energetic driving forces for the misfolding of the hormone into aggregates. Our research will integrate state-of-the-art technology including nuclear magnetic resonance (NMR), fluorimetry, transmission electron microscopy (TEM) and total internal reflection microscopy (TIRFM) to: (1) Obtain structural information on amylin aggregates over a range of distance scales and the processes by which they are formed. (2) Examine the role of charge-charge interactions in amylin aggregation. (3) Investigate the roles of membrane lipids and other cofactors in facilitating aggregation. The ultimate goal of our work is to build a structural and biophysical platform for the development of drugs that interfere with amylin aggregation, in order to treat type 2 diabetes.

If a person with diabetes were to ask you how your project will help them in the future, how would you respond? 

I would first reassure the person that researchers and health care providers all over the world are working hard to make progress towards understanding and treating the disease. Our own research is aimed at understanding the chemistry and physics of the processes that subvert the normal function of amylin and convert it into toxic aggregated forms. We will use NMR spectroscopy to gain insights into the structural properties of amylin at the atomic level. Fluorescence spectroscopy and isotope exchange techniques will be used to investigate the time course of the development of amylin aggregates and see how changes in the molecular environment (pH, salts, other molecules) affect aggregation. High-resolution microscopy techniques such as TIRFM will be used to obtain movies that track the growth of individual fibrils over period of hours to days, thereby allowing us to see directly the steps in aggregate growth and how aggregates interact with other macromolecules relevant to pathology. Once we have obtained a classification of the different types of amylin aggregates, we will correlate their properties with their toxicity to a mouse model of pancreatic beta-cells. With this information in hand, we can turn our attention to interfering with different steps in the processes that cause amylin to damage pancreatic beta-cells. For example, if uncharged segments of the hormone facilitate aggregation while the charged parts oppose it, we can take advantage of these properties to make analogues that attach to growing aggregates but block further aggregation. Similarly, we can design amylin analogues that would preserve the portions of the molecule involved in aggregation but that would interfere with the interactions of aggregates with cell membranes. These approaches should pave the way to new drugs that can be used to treat patients with type 2 diabetes.

Why is it important for you, personally, to become involved in diabetes research? What role will this award play in your research efforts? 

It is estimated that about 200 million people worldwide (4%) and about 24 million people in the US (8%) have diabetes. Type 2 diabetes is the most common form of the disease accounting for about 90% of all cases. If current trends continue, the incidence of type 2 diabetes is likely to increase, in part due to unhealthy lifestyles and in part due to an aging population as human life spans continue to increase. In addition to the suffering caused by the disease, the costs of treatment are staggering, exceeding $100 billon in the US alone. 

Diabetes is clearly an important health and societal problem. The award will allow me to apply my expertise in structural biology and biophysics to the challenging problem of how amylin converts from its normal state to harmful aggregates. Moreover, the award will enable my group to explore molecular design strategies to block amylin aggregation and toxicity. The main objective is to eventually use this research to develop drugs for the treatment of type 2 diabetes. A second mission of my research program is to train the students that will become the next generation of leaders in science. The funds from this award will make it possible to support the work of two highly ambitious graduate students and a postdoctoral fellow who are eager to start making their own contributions to diabetes research.

In what direction do you see the future of diabetes research going? 

I strongly believe that an understanding of the molecular structure aspects of diabetes will become increasingly important in formulating new approaches to disease treatment. It is often difficult for scientists to convey to non-specialists the importance of basic research. Yet much of what is known about amylin today came from scientists asking fundamental questions about what this molecule does. Similarly, drugs such as the amylin analogue pramlintide came from the realization that incorporating amino acids from rat amylin, which does not form fibrils, into the human sequence would result in a peptide that retained activity while avoiding aggregation. I expect that basic research on disease mechanisms will continue to be important in developing the expanding arsenal of tools that can be used to combat diabetes. In spite of the tremendous progress already achieved, much remains to be learned.  With regards to amylin, we still don't have a complete picture of what drives the transition of the hormone to pathological forms, and which of the aggregates are primarily responsible for pathology. Are the fibril endpoints of aggregation the culprits or are intermediates in fibrillization to blame? The problem becomes even more complex if, as we are starting to find, fibrils formed under different conditions vary in their toxicity. I expect that as in other fields of science, diabetes research will become increasingly interdisciplinary and collaborative. It is our hope that our work will be useful not only for the immediate goals of our project but to scientists working on other aspects of the disease. In turn, I appreciate that the discoveries we will make follow in the footsteps of pioneers in diabetes research and build upon the innovations of the scientists who developed the technologies we will use for our investigations.