Type 1 and type 2 diabetes mellitus: are they mutually exclusive?

ABSTRACT

<p><b>INTRODUCTION</b>With advancement in the understanding of the pathogenesis underlying diabetes mellitus (DM), the boundary between type 1 and type 2 DM (T1DM and T2DM) does not seem to be as clear cut as previously thought. This study was designed to test the possibility of overlap between the spectra of immune-mediated DM and insulin resistance.</p><p><b>METHODS</b>To test for the possibility of overlap, we looked for autoantibodies typical of T1DM in patients with classical T2DM, and insulin resistance in patients with T1DM. Autoantibodies against islet cell antigen, glutamic acid decarboxylase-65 and insulinoma-associated antigen-2 were tested in 82 patients with T2DM and 27 patients with T1DM. The patients had been diagnosed on clinical criteria using standard laboratory techniques. Clinical parameters of diagnostic importance were noted, and homeostatic model assessment of insulin resistance (HOMA-IR) was calculated using fasting insulin and fasting blood glucose ratio.</p><p><b>RESULTS</b>Autoantibodies against one or more beta cell antigens were detected in 12.19% of patients clinically diagnosed to have T2DM, and insulin resistance (HOMA-IR > 2.5) was diagnosed in 37.03% of patients with T1DM. It was not possible to identify any combination of clinical or biochemical markers that could predict autoantibody positivity in T2DM patients. T1DM patients with insulin resistance had a significantly higher body mass index than their insulin-sensitive counterparts (p = 0.02).</p><p><b>CONCLUSION</b>Autoantibodies against beta cell antigens are detectable in insulin-resistant T2DM patients, and insulin resistance may be present in relatively overweight T1DM patients. No differentiating clinical features that might predict autoantibody positivity in T2DM patients were found.</p>