Lawrence A Leiter1. 1. Department of Medicine, University of Toronto, St. Michael's Hospital, Toronto, ON, Canada. leiterl@smh.toronto.on.ca
Abstract
BACKGROUND: Type 2 diabetes results from increasing insulin resistance coupled with progressive loss of beta-cell function. Further deterioration of beta-cell function is associated with progression of diabetes and the potential development of microvascular and macrovascular complications. SCOPE: This review examines current knowledge of beta-cell function and uses this information to assess how the results of ongoing trials could increase our understanding of disease progression and potential interventions. Data were derived from a Medline search using the search terms 'beta-cell dysfunction', 'IGT', 'thiazolidinediones', 'metformin', and 'sulfonylurea'. RESULTS: The mechanisms that underlie beta-cell dysfunction are complex and most likely involve the interplay of a range of factors that reduce both beta-cell mass and secretory function. These include detrimental effects associated with hyperglycemia itself, elevated free fatty acids, and inflammatory responses linked to adipocyte-derived cytokines, with apoptosis a key underlying mechanism. Early intervention with treatments that address these defects, and preserve beta-cell function while improving insulin sensitivity, may delay disease progression in patients with type 2 diabetes and also prevent the development of diabetes in 'at-risk' individuals. Two of the studies examining the effects of interventions on development and progression of diabetes that are due to report shortly are ADOPT (A Diabetes Outcome Progression Trial), comparing a thiazolidinedione, metformin and a sulfonylurea in patients with type 2 diabetes not previously treated with oral hypoglycemic agents, and DREAM (Diabetes REduction Assessment with ramipril and rosiglitazone Medication), assessing the effects of a thiazolidinedione and an angiotensin-converting enzyme inhibitor in subjects with impaired glucose tolerance and/or impaired fasting glucose. CONCLUSIONS: Although we do not have a full understanding of the mechanisms driving progression of type 2 diabetes, there is growing evidence that we may be able to modulate them and thereby improve patient outcomes.
BACKGROUND:Type 2 diabetes results from increasing insulin resistance coupled with progressive loss of beta-cell function. Further deterioration of beta-cell function is associated with progression of diabetes and the potential development of microvascular and macrovascular complications. SCOPE: This review examines current knowledge of beta-cell function and uses this information to assess how the results of ongoing trials could increase our understanding of disease progression and potential interventions. Data were derived from a Medline search using the search terms 'beta-cell dysfunction', 'IGT', 'thiazolidinediones', 'metformin', and 'sulfonylurea'. RESULTS: The mechanisms that underlie beta-cell dysfunction are complex and most likely involve the interplay of a range of factors that reduce both beta-cell mass and secretory function. These include detrimental effects associated with hyperglycemia itself, elevated free fatty acids, and inflammatory responses linked to adipocyte-derived cytokines, with apoptosis a key underlying mechanism. Early intervention with treatments that address these defects, and preserve beta-cell function while improving insulin sensitivity, may delay disease progression in patients with type 2 diabetes and also prevent the development of diabetes in 'at-risk' individuals. Two of the studies examining the effects of interventions on development and progression of diabetes that are due to report shortly are ADOPT (A Diabetes Outcome Progression Trial), comparing a thiazolidinedione, metformin and a sulfonylurea in patients with type 2 diabetes not previously treated with oral hypoglycemic agents, and DREAM (Diabetes REduction Assessment with ramipril and rosiglitazone Medication), assessing the effects of a thiazolidinedione and an angiotensin-converting enzyme inhibitor in subjects with impaired glucose tolerance and/or impaired fasting glucose. CONCLUSIONS: Although we do not have a full understanding of the mechanisms driving progression of type 2 diabetes, there is growing evidence that we may be able to modulate them and thereby improve patient outcomes.