Background: Intraperitoneally administered insulin is regarded as the most physiological replacement therapy, leading to lower peripheral insulin concentrations and equal or better glycaemic control than subcutaneous insulin. This two-part study was undertaken to evaluate the effect of CAPD, as well as the use of subcutaneous vs. intraperitoneal insulin on insulin sensitivity, glycaemic control and serum lipids in type 1 diabetes.
Methods: Eleven patients with type 1 diabetes mellitus and chronic renal failure participated the studies. Glycated haemoglobin (HbA1c), euglycaemic hyperin-sulinaemic clamp, serum lipids, and patient well-being were measured. During CAPD all patients were first treated with subcutaneous insulin and then with intraperitoneal insulin. The metabolic studies were repeated after both treatment periods for at least 3 months. Metabolic studies were performed on six of the patients also before initiation of CAPD.
Results: HbA1c rose after the initiation of CAPD from 8.85 +/- 0.54% to 9.58 +/- 0.66%, NS) and improved after changing from subcutaneous to intraperitoneally administered insulin (from 9.49 +/- 0.43% to 8.13 +/- 0.39%, P < 0.01). Insulin dose increased by 15% after initiation of CAPD and 128% after switching from subcutaneous to intraperitoneal insulin. Glucose disposal rate enhanced by 39% (P = 0.05) and 14% respectively (P < 0.01). Initiation of CAPD had no significant effects on serum lipids but intraperitoneally administered insulin reduced HDL cholesterol and increased LDL/HDL ratio significantly.
Conclusions: Intraperitoneal insulin therapy offers better glycaemic control and insulin sensitivity than subcutaneous insulin. Deterioration of HbA1c after initiation of CAPD while patients remained on subcutaneous insulin may be partly due to absorbed energy from the dialysate. Intraperitoneal insulin therapy seems to have detrimental effects on serum lipids. The clinical significance in modifying the risk of atherosclerosis remains unclear.