*4.4.1.5 Aminopeptidase*

Adipocytes are involved in production of a polypeptide hormone named aminopeptidase, which circulates at very high levels in the bloodstream, exerts anti-inflammatory effect. It also expresses an anti-atherosclerotic effect and inhibits intimal thickening and vascular smooth muscle cell proliferation in injured arteries [56]. Angiogenesis, a neo-vessel formation from pre-existing micro-vessels requires sequential steps involving detachment of pre-existing pericytes for vascular destabilisation, extracellular matrix turnover, migration, proliferation, tube formation by endothelial cells, and reattachment of pericytes for vascular stabilisation. Aminopeptidases has been found to regulate the N-terminal modification of proteins and peptides for maturation, activation or degradation, and thereby relate to a variety of biological processes. Three types of aminopeptidases which have been reported are involved in angiogenesis. They include type 2 methionine aminopeptidase, aminopeptidase N, and adipocyte-derived leucine aminopeptidase/puromycin insensitive leucyl-specific aminopeptidase [57]. It has been documented and shown by Costagliola et al. [58] that APN levels in aqueous humour of patients with type 2 diabetes, PDR, and macular edema are higher than in aqueous of control subjects.
