Non-traditional roles of complement in type 2 diabetes: Metabolism, insulin secretion and homeostasis
MOLECULAR IMMUNOLOGY
Authors: King, Ben C.; Blom, Anna M.
Abstract
Type 2 Diabetes (T2D) is a disease of increasing importance and represents a growing burden on global healthcare and human health. In T2D, loss of effectiveness of insulin signaling in peripheral tissues cannot be compensated for by adequate insulin secretion, leading to hyperglycemia and resultant complications. In recent years, inflammation has been identified as a central component of T2D, both in inducing peripheral insulin resistance as well as in the pancreatic islet, where it contributes to loss of insulin secretion and death of insulin-secreting beta cells. In this review we will focus on non-traditional roles of complement proteins which have been identified in T2D-associated inflammation, beta cell secretory function, and in maintaining homeostasis of the pancreatic islet. Improved understanding of both traditional and novel roles of complement proteins in T2D may lead to new therapeutic approaches for this global disease. (C) 2016 Elsevier Ltd. All rights reserved.
Acquisition of negative complement regulators by the saprophyte Leptospira biflexa expressing LigA or LigB confers enhanced survival in human serum
IMMUNOLOGY LETTERS
Authors: Castiblanco-Valencia, Monica M.; Fraga, Tatiana R.; Breda, Leandro C. D.; Vasconcellos, Silvio A.; Figueira, Claudio P.; Picardeau, Mathieu; Wunder, Elsio; Ko, Albert I.; Barbosa, Angela S.; Isaac, Lourdes
Abstract
Leptospiral immunoglobulin-like (Lig) proteins are surface exposed molecules present in pathogenic but not in saprophytic Leptospira species. We have previously shown that Lig proteins interact with the soluble complement regulators Factor H (FH), FH like-1 (FHL-1), FH related-1 (FHR-1) and C4b Binding Protein (C4BP). In this study, we used the saprophyte L. biflexa serovar Patoc as a surrogate host to address the specific role of LigA and LigB proteins in leptospiral complement evasion. L biflexa expressing LigA or LigB was able to acquire FH and C4BP. Bound complement regulators retained their cofactor activities of Fl in the proteolytic cleavage of C3b and C4b. Moreover, heterologous expression of ligA and ligB genes in the saprophyte L. biflexa enhanced bacterial survival in human serum. Complement deposition on lig-transformed L biflexa was assessed by flow cytometry analysis. With regard to MAC deposition, L. biflexa expressing LigA or LigB presented an intermediate profile: MAC deposition levels were greater than those found in the pathogenic L. interrogans, but lower than those observed for L. biflexa wildtype. In conclusion, Lig proteins contribute to in vitro control of complement activation on the leptospiral surface, promoting an increased bacterial survival in human serum. (C) 2016 European Federation of Immunological Societies. Published by Elsevier B.V. All rights reserved.