Complement component 3 (C3) as a biomarker for insulin resistance after bariatric surgery Letícia de Oliveira Souza Bratti a , Ícaro Andrade Rodrigues do Carmo b , Taís Ferreira Vilela c , Sandro Wopereis a , Ana Carolina Rabello de Moraes b , Beatriz Garcia Mendes Borba b , Liliete Canes Souza b , Fabíola Branco Filippin-Monteiro b, ⁎ a Programa de Pós-Gaduação em Farmácia, Centro de Ciências da Saúde, Universidade Federal de Santa Catarina, Florianópolis, SC 88040900, Brazil b Departamento de Análises Clínicas, Centro de Ciências da Saúde, Universidade Federal de Santa Catarina, Florianópolis, SC 88040900, Brazil c Departamento de Clínica Médica, Centro de Ciências da Saúde, Universidade Federal de Santa Catarina, Florianópolis, SC 88040900, Brazil abstract article info Article history: Received 27 October 2016 Received in revised form 22 January 2017 Accepted 6 February 2017 Available online xxxx Objectives: Since complement system has been recently associated with metabolic and cardiovascular dis- eases, and closely related to insulin resistance, we investigated the association of plasma complement factor 3 (C3) and factor 4 (C4) with insulin sensibility and weight loss after bariatric surgery. Methods: Serum levels of C3, C4, total cholesterol, triacylglycerol, HDL-cholesterol, LDL-cholesterol and ho- meostatic model assessment (HOMA-IR) measurements were assessed in morbidly obese patients before and after bariatric surgery, including a 6-month follow-up period, as well as a comparison with a lean group. Results: Weight loss decreased body mass index (BMI), serum triacylglycerol, and increased serum HDL-cho- lesterol and insulin sensitivity, as expected. C3 and C4 were significantly higher in obese individuals when com- pared to lean subjects (p b 0.001). In addition, C3 and C4 positively correlated with BMI and HOMA-IR, however, only C3 were significantly decreased 6 months after surgery. Conclusion: C3 was strongly associated with insulin sensitivity after bariatric surgery, © 2017 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved. Keywords: Morbid obesity Bariatric surgery Complement system C3, C4 and C3a-desArg Type 2 diabetes Dyslipidemia and cardiovascular disease 1. Introduction Recent data about global obesity revealed that approximately 39% of adults were overweight in 2014, and 13% were obese. Besides, obesity has been increased exponentially in the last 30 years and it has become a public health problem due to obesity-associated comorbidities such as type 2 diabetes, cardiovascular diseases, and cancer [1]. In the treatment of morbid obesity, bariatric surgery became popular due to the difficulty in weight loss maintenance with clinical treatment. Approximately 450 thousand bariatric surgeries are performed each year worldwide. This procedure has been used as an elective interven- tion, promoting substantial and durable weight loss, reducing comor- bidities, and improving the quality of life of these individuals. Bariatric surgery can be divided into three categories: restrictive, malabsorptive and a combination of both. The most common procedure is the Roux- en-Y gastric bypass (RYGB), a combination of restrictive and malabsorptive procedures, and the restrictive one, called sleeve gastrec- tomy (SG) [2] [3]. It is well-established that inflammation in obesity is characterized by a systemic, chronic and low-grade inflammation [4] that leads to an increase in pro-inflammatory proteins such as C-reactive protein (CRP) and interleukin-6 (IL-6) [5] and some components of comple- ment system [6] [7]. The complement system is mainly associated with innate immunity. However, recent studies have shown that this system is involved in metabolic events [7] [8]. The majority of comple- ment components are synthesized mainly by hepatocytes, but also can be produced by other cells such as macrophages and adipocytes [6] [8]. Recently, it was demonstrated that complement C3 (C3) synthesis can be up-regulated by pro-inflammatory cytokines IL-6 and interleu- kin-1 beta (IL-1β), while complement C4 (C4) can be influenced by gamma interferon (IFN-γ) [9]. Obese adipose tissue can contribute to the increase of pro-inflamma- tory cytokines leading to the hepatic production of C3 and C4 proteins. An increase of these proteins in obese individuals has already been re- ported [5]. In addition, C3 originates C3a-desArg lipogenic hormone, in- volved in the uptake of fatty acids, glucose and triacylglycerol synthesis by adipocytes [10]; it has been associated with cardiovascular risk Clinical Biochemistry xxx (2017) xxx–xxx ⁎ Corresponding author at: Campus Universitário, Universidade Federal de Santa Catarina, Trindade, 88040900, Florianópolis, SC, Brazil. E-mail address: fabiola.monteiro@ufsc.br (F.B. Filippin-Monteiro). CLB-09472; No. of pages: 4; 4C: http://dx.doi.org/10.1016/j.clinbiochem.2017.02.006 0009-9120/© 2017 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved. Contents lists available at ScienceDirect Clinical Biochemistry journal homepage: www.elsevier.com/locate/clinbiochem Please cite this article as: L.O.S. Bratti, et al., Complement component 3 (C3) as a biomarker for insulin resistance after bariatric surgery, Clin Biochem (2017), http://dx.doi.org/10.1016/j.clinbiochem.2017.02.006