Why and by How Much is Insulin Absorption Reduced by Insulin-derived Amyloidosis? A Scoping Review

Insulin therapy is one of the central treatments for diabetes mellitus. Insulin-derived localized amyloidosis (IDLA) is a known skin-related complication of insulin injection. This is one of the causes of poor glycemic control in diabetic patients on insulin therapy. The aim of this study was to review and update the findings on the extent and mechanism of reduced insulin absorption in IDLA. A literature search was conducted on decreased insulin absorption and its mechanisms, and nine references were selected, with seven of these on decreased insulin absorption and four on mechanisms. Insulin absorption at IDLA sites was reported to be 27–94% lower compared with normal sites. In addition, a comparison between nonpalpable and palpable IDLA sites revealed a significant decrease in insulin absorption at the palpable IDLA site. The mechanism of insulin malabsorption was found to be a reduction in insulin absorption at the palpable IDLA sites. Four mechanisms of decreased insulin absorption were identified: decreased subcutaneous blood flow, adsorption of administered insulin onto insulin amyloid fibers, impaired diffusion of insulin subcutaneously, and physical factors such as shaking of the insulin preparation. These mechanisms should be investigated in vivo in the future.