Is there a rationale for insulin therapy in pre-diabetic individuals?

Type 2 diabetes mellitus is usually preceded by impaired glucose tolerance (IGT) and/or impaired fasting glucose (IFG), which are often referred to as pre-diabetes. Individuals with IGT demonstrate beta-cell dysfunction, insulin resistance, and increased hepatic glucose production; IGT and IFG are risk factors for both diabetes and cardiovascular disease. Type 2 diabetes is associated with micro- and macrovascular complications that lead to excessive mortality and morbidity and the risk of microvascular complications extends to people with pre-diabetes. Maintaining good glycemic control in type 2 diabetes can reduce the risk of developing chronic disease-associated complications. Most individuals who develop type 2 diabetes appear to pass through a stage of IFG or IGT; thus, early intervention (lifestyle and/or pharmacologic) in individuals with pre-diabetes may help prevent cardiovascular disease and the development of type 2 diabetes.The use of exogenous insulin treatment offers the potential to reduce the cardiovascular risk in individuals with type 2 diabetes or pre-diabetes through effective reductions in blood glucose and lipid levels, and in the associated tissue damage resulting from their chronic elevations. However, there are barriers associated with insulin initiation in both type 2 diabetes and pre-diabetes (e.g. hypoglycemia, weight gain, the possible unpredictable action of long-acting insulin, and the need for injections). Insulin glargine, with its flat time-action profile, near 24-hour duration of action, reduced risk of hypoglycemia, and improved glycemic control compared with insulin suspension isophane (neutral protamine hagedorn [NPH] insulin), may help to overcome some of these barriers.Initial results from a small study have indicated the feasibility of treating individuals with pre-diabetes to near-normoglycemia using a regimen of low-dose insulin glargine plus caloric restriction. This is being followed up in the ongoing ORIGIN (Outcomes Reduction with Initial Glargine INtervention) study, which will investigate whether treatment to near-normoglycemia with insulin glargine in individuals with IGT, IFG, or new-onset type 2 diabetes can reduce cardiovascular morbidity and mortality compared with conventional management of these conditions, and whether the rate of progression to type 2 diabetes can be similarly reduced.Further studies are needed to investigate the potential benefits of insulin therapy in individuals with pre-diabetes.