Insulin dose-response studies in severely insulin-resistant type 2 diabetes--evidence for effectiveness of very high insulin doses.

AIM

To combat diabetic complications strict glycaemic control is desirable in type 2 diabetes, but some patients are severely insulin resistant and it is not known whether high doses of insulin are effective. This study was designed to determine the acute dose-response effects of insulin in patients with type 2 diabetes and severe insulin resistance.

METHODS

We included eight insulin-resistant (mean insulin dose: 186 IU/day; body mass index: 35) subjects with type 2 diabetes in a single-blinded, randomized crossover study. Each subject was studied on two occasions. On each occasion, subjects underwent two 3-h hyperinsulinaemic euglycaemic clamps. The subjects were randomized to two low-dose insulin infusions (0.5 and 1.5 mU/kg/min in random order) on one occasion and to two high-dose insulin infusions (3.0 and 5.0 mU/kg/min in random order) on another occasion.

RESULTS

On all occasions, steady-state glucose infusion rates (SSGIRs) were accomplished and we observed a clear dose-response relationship with GIR values of 0.4 ± 0.2 (s.e.), 2.6 ± 0.6, 3.7 ± 0.8 and 4.9 ± 0.9 mg/kg/min during the 0.5, 1.5, 3.0 and 5.0 mU/kg/min insulin infusions, respectively (p < 0.001). Likewise, there was a dose-dependent suppression of endogenous glucose production (EGP) (p < 0.009), plasma free fatty acids (FFAs) (p < 0.001) and plasma glucagon (p = 0.001).

CONCLUSIONS

Our results show that the insulin dose response in terms of GIR and EGP is preserved for insulin doses corresponding to >800 IU/day, suggesting effectiveness of very high insulin doses in severely insulin-resistant subjects.