Abstract
Insulin sensitivity was evaluated in 16 insulinoma patients and in 15 obese persons
with Type 2 diabetes mellitus by using hyperinsulinaemic clamps and analysis of insulin
receptor characteristics on erythrocytes. Significantly decreased insulin sensitivity
index (M/I) was found in both insulinoma and obese Type 2 diabetic patients as compared
with healthy non-obese controls (21.2 ± 2.2 and 19.5 ± 2.6 vs 40.3 ± 3.7 µmol · kg-1 · min-1 per mU · I-1 × 100, p < 0.001). No difference was observed between both groups of patients. Metabolic
clearance rate of glucose was strongly reduced in obese diabetic patients but it was
normal in insulinoma patients in comparison with healthy persons (2.7 ± 0.4 vs 8.7
± 0.6 or 7.9 ± 0.7 ml · kg-1 · min-1, p < 0.001). A decreased insulin binding on specific receptors caused by reduced
binding capacity was observed only in insulinoma patients but not in obese Type 2
diabetic patients. A significant negative correlation was proved between body mass
index (BMI) and insulin sensitivity index (r = - 0.82, p < 0.001) indicating that
BMI is the main determining factor of insulin resistance in the total cohort of examined
patients. We conclude that insulin resistance was caused by postreceptor changes in
obese Type 2 diabetes, whereas a decreased insulin binding capacity together with
post-receptor defect was present in insulinoma patients.
Key words
Insulinoma - Type 2 Diabetes Mellitus - Insulin Sensitivity - Insulin Receptors
