Insulin antibody

Background of Insulin antibody

Proinsulin is synthesized as a single chain, 110 amino acid (aa) preproprecursor that contains a 24 aa signal sequence and an 86 aa proinsulin propeptide. Following removal of the signal peptide, the proinsulin peptide undergoes further proteolysis to generate mature insulin, a 51 aa disulfidelinked dimer that consists of a 30 aa B chain (aa 2554) bound to a 21 aa A chain (aa 90110). The 34 aa intervening peptide (aa 5589)that connects the B and A chains is termed the Cpeptide.

Human proinsulin shares 84% and 80% aa sequence identity with rat and bovine proinsulin, respectively. Most of the sequence variation between species occurs in the region of the Cpeptide. This peptide generates a structural conformation that allows for the correct formation of the intrachain disulphide bonds . Insulin is a molecule that facilitates the cellular uptake of glucose. This is accomplished by regulating the appearance of membrane glucose transporters. Low insulin levels or lack of insulin are associated with type 2 and type 1 diabetes mellitus, respectively. These conditions are associated with an increased risk for microvascular complications such as retinopathy, nephropathy, and peripheral neuropathy . Proinsulin also circulates, but its physiologic role is less well understood. It does possess about 25% of the activity of mature insulin, but it would seem unlikely to be a natural substitute for insulin . In type 2 diabetes, an elevated proinsulin to insulin ratio in the circulation is a well known abnormality . Perhaps this abnormality represents either compromised proteolytic processing or a general inability to process increased levels of insulin precursor . In any event, proinsulin will stimulate amylin secretion by .cells, and amyloid formation in pancreatic islets that promotes decreased . cell function . Studies also suggest that fasting serum proinsulin may be a better predictor of future type 2 diabetes than fasting insulin levels in obese children .