minocycline and Amyloidosis

The use of tetracyclines has declined because of the appearance of resistant bacterial strains. However, the indications of nonantimicrobial activities of these drugs have considerably raised interest and triggered clinical trials for a number of different pathologies. About 10 years ago we first reported that tetracyclines inhibited the aggregation of prion protein fragments and Alzheimer's β peptides, destabilizing their aggregates and promoting their degradation by proteases. On the basis of these observations, the antiamyloidogenic effects of tetracyclines on a variety of amyloidogenic proteins were studied and confirmed by independent research groups. In this review we comment on the data available on their antiamyloidogenic activity in preclinical and clinical studies. We also put forward that the beneficial effects of these drugs are a result of a peculiar pleiotropic action, comprising their interaction with oligomers and disruption of fibrils, as well as their antioxidant, anti-inflammatory, antiapoptotic, and matrix metalloproteinase inhibitory activities.

Topics: Amyloid; Amyloidogenic Proteins; Amyloidosis; Animals; Anti-Bacterial Agents; Anti-Inflammatory Agents; Antioxidants; Apoptosis; Clinical Trials as Topic; Drug Administration Schedule; Humans; Matrix Metalloproteinase Inhibitors; Protein Conformation; Tetracyclines

Skin-related complications of insulin therapy have long been a problem as a factor interfering with insulin therapy. Among the traditional skin-related complications, lipoatrophy and insulin allergy have decreased markedly with the development of insulin preparations, but lipohypertrophy is still common in insulin-treated patients. Recently, there have been more reports of a skin-related complication called insulin-derived amyloidosis or insulin ball. Insulin-derived amyloidosis is a condition in which injected insulin becomes amyloid protein and is deposited at the injection site. Insulin-derived amyloidosis causes poor glycemic control and increased insulin dose requirements, which are caused by decreased insulin absorption. Lipohypertrophy also decreases insulin absorption, but insulin-derived amyloidosis causes a more significant decrease in insulin absorption and has a greater clinical impact. Therefore, it is important to make a differential diagnosis between insulin-derived amyloidosis and lipohypertrophy, but sometimes it is difficult to distinguish the two and imaging studies are required. The diagnosis of insulin-derived amyloidosis is often difficult in the general practice, and its pathogenesis and prevalence have not been fully clarified. Recently, it has been reported that insulin-derived amyloidosis can be toxic, suggesting an association with minocycline use. The treatment of insulin-derived amyloidosis and lipohypertrophy is to avoid the site of amyloidosis or lipohypertrophy and inject insulin, but the dose of insulin injection should be reduced. Prevention of both insulin-derived amyloidosis and lipohypertrophy is important, and for this purpose, observations of the insulin injection site and instruction on appropriate insulin injection techniques are necessary, and multidisciplinary cooperation is extremely important.

Topics: Amyloidosis; Humans; Injections; Insulin; Minocycline

Insulin balls, localized insulin amyloids formed at subcutaneous insulin-injection sites in patients with diabetes, cause poor glycemic control owing to impairments in insulin absorption. Our previous study has shown that some insulin balls are cytotoxic, but others are not, implying amyloid polymorphism. Interestingly, the patient with toxic insulin balls had been treated with antibiotic minocycline, suggesting a possible relationship between toxicity of insulin balls and minocycline. However, the direct effect of minocycline on the structure and cytotoxicity of the insulin amyloid is still unclear. Herein, we demonstrated that that minocycline at physiological concentrations induced degradation of insulin amyloids formed from human insulin and insulin drug preparations used for diabetes patients. Interestingly, the process involved the initial appearance of the toxic species, which subsequently changed into less-toxic species. It is also shown that the structure of the toxic species was similar to that of sonicated fragments of human insulin amyloids. Our study shed new light on the clarification of the revelation of insulin balls and the development of the insulin analogs for diabetes therapy.

Topics: Amyloid; Amyloidosis; Anti-Bacterial Agents; HeLa Cells; Humans; Insulin; Minocycline