Non-insulin-treated ICA positive and negative diabetics are equally insulin resistant

Insulin action was assessed in 5 cytoplasmic islet cell antibody (ICA) positive non-diabetics, 8 ICA positive (type I) non-insulin-treated diabetics, 7 ICA negative insulin-treated diabetics by measurement of steady state plasma glucose (SSPG) levels during a combined intravenous infusion of propranolol, adrenaline, glucose and insulin. SPPG values of ICA positive and negative non-diabetics were similar and their combined value (4.0 +/- 0.5 mmol/l) was significantly lower (p less than 0.01 and less than 0.01) than those (11.5 +/- 1.9 and 11.3 +/- 2.2 mmol/l) of ICA positive and negative diabetics, indicating that both groups of diabetics were similarly insulin resistant. Similar correlations were observed between SSPG and HbA1 levels when considering all ICA positive subjects (r = 0.89, p less than 0.001) and all ICA negative subjects (r = 0.73, p less than 0.01). Conventional insulin treatment (2.6 months) in 4 ICA positive diabetics improved insulin action in each case with a reduction in mean SSPG concentration from 14.0 +/- 2.3 to 8.5 +/- 3.4 mmol/l. Thus, ICA positive and negative diabetics, of equivalent degree of carbohydrate intolerance, are equally insulin resistant. Insulin treatment may improve, but appears not to normalise, insulin action in ICA positive (type I) diabetics.