Beta cell dysfunction in patients with acute myocardial infarction but without previously known type 2 diabetes:: a report from the GAMI study

Aims/hypothesis: Patients with acute myocardial infarction (AMI) but without previously known type 2 diabetes have a high prevalence of undiagnosed IGT and type 2 diabetes. Such perturbations have dismal prognostic implications. The aim of this study was to characterise AMI patients in terms of insulin resistance and beta cell function. Methods: A total of 168 consecutive AMI patients were classified by means of an OGTT before hospital discharge as having NGT, IGT or type 2 diabetes. The homeostasis model assessment (HOMA-IR) was used to estimate insulin resistance. Beta cell responsiveness was quantified as insulinogenic index (IGI) at 30 min (Delta I-30/Delta G(30)). Results: According to the HOMA-IR, patients with type 2 diabetes were more insulin resistant than those with IGT or NGT (p=0.003). Beta cell responsiveness deteriorated with decreasing glucose tolerance as measured by the IGI (median [quartile 1, quartile 3] in pmol/mmol: NGT, 70.1 [42.7, 101.4]; IGT, 48.7 [34.7, 86.8], type 2 diabetes, 38.1 [25.7, 61.6]; p < 0.001). The IGI was significantly related to admission capillary blood glucose (r=-0.218, p=0.010) and to the area under the curve for glucose (r=-0.475, p < 0.001). Conclusions/interpretation: Glucose abnormalities are very common in patients with AMI but without previously known type 2 diabetes. To a significant extent, this seems to be related to impaired beta cell function and implies that dysglycaemia immediately after an infarction is not a stress epiphenomenon but reflects stable disturbances of glucose regulation preceding the AMI. Early beta cell dysfunction may have important pathophysiological implications and may serve as a future target for treatment strategies.