Diabetes mellitus as a protective factor of abdominal aortic aneurysm: Possible mechanisms.

Abdominal aortic aneurysm (AAA) shares several risk factors with atherosclerosis. Among these, diabetes mellitus (DM) could have a negative effect on the formation, growth and expansion of AAA. Several systematic reviews and meta-analyses reported up to 2016 have shown concordant results regarding the possible protective effect on AAA formation. However, the pathophysiological mechanisms of this supposed protective effect are still unknown. It appears that both hyperglycaemia and hyperinsulinemia, which are closely associated with DM, cause an increase in advanced glycation end-products, a decrease in fibrinolysis, and alterations in smooth muscle cells, leading to a decreased risk of aneurysm growth and expansion. This protective role is mainly mediated by a decrease in metalloproteinases, mainly type 2 and 9. In addition, drugs used to treat type 2 DM, as well as those for hypertension and dyslipidaemia could also play an important role in this protective effect. Metformin, thiazolidinediones, DPP4 inhibitors, statins, and angiotensin-converting enzyme inhibitors have been evaluated in this field. In conclusion, studies reported so far seem to confirm the protective effect of DM in both the formation and expansion of AAA, although future long-term studies are needed to confirm the pathophysiological mechanisms involved, as well as the role of concomitant medication.