Basal insulin analogs: from pathophysiology to therapy. What we see, know, and try to comprehend?

During the past 10 years, several new basal insulin analogs have been developed. There has been for 3 years controversy on the potential increased risk for cancer with insulin glargine, which ceased with the publication of the ORIGIN trial in 2012. In insulin-treated persons with type 2 diabetes, it is usual to recommend that plasma insulin concentrations remain within a 50-200 pmol/L range in order to avoid overinsulinization, a potential causative factor for increased mitogenicity. Such concentrations are achieved when daily doses of insulin glargine or NPH insulin approximate 0.4 units/kg. However, the total plasma insulin concentrations are much greater in persons treated with insulin detemir and especially insulin degludec. These insulins derive their protracted action from the insertion of a long chain fatty acid moiety to the insulin molecule thereby increasing albumin binding. As a consequence, in persons with type 2 diabetes, stable total plasma concentrations as high as either 1600 or 6000 pmol/L are observed for insulin detemir or degludec, respectively. At present, the free to bound ratio of plasma insulin concentrations remains unknown for these two compounds. A first requirement is to understand how these insulins are eliminated or degraded and secondly to quantify the respective contributions of the free and bound fractions. Therefore, prior to early phase 2 or 3 randomized clinical trials, a better comprehension of the metabolism of all the new insulins would be invaluable.