Issues Surrounding Tight Glycemic Control in People with Type 2 Diabetes Mellitus

Abstract

OBJECTIVE: To review the prospective evidence surrounding the issue of tight glycemic control in people with type 2 diabetes mellitus and resultant long-term complications. DATA SOURCE: Conference proceedings and a MEDLINE search (1966–February 1998) identified pertinent English-language publications on type 2 diabetes in humans. Key search terms included insulin resistance, diabetes mellitus, non-insulin-dependent, macrovascular complications, microvascular complications, and intensive glycemic control. STUDY SELECTION: Selection of prospective epidemiologic and clinical studies were limited to those focusing on the management of type 2 diabetes. All articles with pertinent information relevant to the scope of this article were reviewed. DATA SYNTHESIS: The pathophysiology of type 1 and type 2 diabetes differ; however, both share chronic complications that significantly affect morbidity and mortality. People with type 1 diabetes have an absolute deficiency of insulin, whereas people with type 2 diabetes have varying degrees of insulin resistance and an inadequate compensatory insulin secretory response. The Diabetes Control and Complications Trial (DCCT) has clearly indicated that intense control of blood glucose in type 1 diabetes prevents and slows the progression of microvascular (i.e., retinopathy, nephropathy) and neuropathic complications. The Kumamoto study showed similar results in nonobese patients with type 2 diabetes. Intense insulin therapy in both populations has proven advantageous, thus supporting a common pathophysiologic process for the microvascular and neuropathic complications. Trends were seen toward fewer macrovascular (atherosclerotic disease) complications in the intensive insulin arm of the DCCT. Conversely, trends were seen toward an increase in macrovascular complications in the VA Cooperative study in people with type 2 diabetes using intensive insulin therapy. This may suggest a discordance in the pathophysiology of macrovascular disease between type 1 and type 2 diabetes. Additionally, it remains uncertain whether tight glycemic control prevents the onset or slows the progression of macrovascular disease. Two studies (the University Group Diabetes Program and the Veterans Affairs Cooperative Study on Glycemic Control and Complications in Type 2 Diabetes) to date have examined pharmacotherapy options for patients with type 2 diabetes and resultant macrovascular complications. It has yet to be determined whether any therapeutic intervention will decrease the morbidity and mortality of macrovascular disease in this population. CONCLUSIONS: In type 2 diabetes, limited prospective evidence does support tight glycemic control to help prevent or slow the progression of microvascular and neuropathic complications. It is uncertain whether tight glycemic control decreases macrovascular complications and which pharmacotherapeutic agent(s) is/are the best options. However, therapy that improves glucose control in combination with aggressive risk factor management should be initiated and enforced in patients with type 2 diabetes in an effort to reduce long-term complications.