Type 1 diabetes (T1D) is an autoimmune disease resulting from self-destruction of insulin-producing β cells. Reduced neutrophil counts have been observed in patients with T1D. However, the pathological roles of neutrophils in the development of T1D remain unknown. Here we show that circulating protein levels and enzymatic activities of neutrophil elastase (NE) and proteinase 3 (PR3), both of which are neutrophil serine proteases (NSPs) stored in neutrophil primary granules, were markedly elevated in patients with T1D, especially those with disease duration of less than one year. Furthermore, circulating NE and PR3 levels increased progressively with the increase of the positive numbers and titers of the autoantibodies against β-cell antigens. An obvious elevation of NE and PR3 was detected even in those autoantibody-negative patients. Increased NE and PR3 in T1D patients are closely associated with elevated formation of neutrophil extracellular traps. By contrast, the circulating levels of α1-antitrypsin (A1AT), an endogenous inhibitor of NSPs, are decreased in T1D patients. These findings support an early role of neutrophil activation and augmented NSPs activities in the pathogenesis of β-cell autoimmunity, and also suggest that circulating NE and PR3 may serve as sensitive biomarkers for diagnosis of T1D.
† These authors contributed equally to this work.
- Received March 24, 2014.
- Accepted July 28, 2014.
- © 2014 by the American Diabetes Association. Readers may use this article as long as the work is properly cited, the use is educational and not for profit, and the work is not altered.