Insulin requirements in patients with diabetes and declining kidney function: differences between insulin analogues and human insulin?

Objectives: In diabetic nephropathy the decline of renal function causes modifications of the insulin and carbohydrate metabolism resulting in changed insulin requirements. The aim of the present study was to identify potential differences in the requirements of human insulin and various insulin analogues in patients with type 1 diabetes mellitus and renal dysfunction. Methods: The insulin requirements of 346 patients with type 1 diabetes mellitus under everyday life circumstances were assessed in an observational study. Simultaneously, laboratory parameters were measured and the estimated glomerular filtration rate (eGFR) was calculated using the formula by Cockcroft-Gault. Medical history and concomitant medication were recorded. The insulin requirements of long-and short-acting insulin were tested for a relationship with the eGFR and laboratory parameters. Results: The dosage of long-acting human insulin did not show any relation to eGFR. In contrast, a strong positive relation between dosage and renal function was found for insulin glargine and insulin detemir. After classification according to renal function, the insulin dosage at eGFR less than 60 ml/min was 29.7% lower in glargine-treated and 27.3% lower in detemir-treated patients compared with eGFR greater than 90 ml/min. Considering the whole range of eGFR, short-acting human insulin did not show a relation with renal function. Only after classification according to renal function was a dose reduction found for human insulin at eGFR less than 60 ml/min. In contrast, requirements of insulin lispro were significantly related to eGFR over the whole range of eGFR. At eGFR less than 60 ml/min the insulin dosage was 32.6% lower than at eGFR greater than 90 ml/min. The requirements of insulin aspart did not show any association with the eGFR. Conclusions: Patients with type 1 diabetes mellitus show different insulin requirements according to the renal function depending on the applied insulin. This finding is essential for the adjustment of insulin therapy in patients with diabetic nephropathy to achieve balanced glycemic control. To determine the underlying mechanisms, further studies on the pharmacokinetics and pharmacodynamics of the different insulins in patients with diabetic nephropathy are needed.